WorldWideScience

Sample records for active shape models

  1. Face Alignment Using Active Shape Model And Support Vector Machine

    OpenAIRE

    Le, Thai Hoang; Vo, Truong Nhat

    2012-01-01

    The Active Shape Model (ASM) is one of the most popular local texture models for face alignment. It applies in many fields such as locating facial features in the image, face synthesis, etc. However, the experimental results show that the accuracy of the classical ASM for some applications is not high. This paper suggests some improvements on the classical ASM to increase the performance of the model in the application: face alignment. Four of our major improvements include: i) building a mod...

  2. Face Alignment Using Active Shape Model And Support Vector Machine

    OpenAIRE

    Le Hoang Thai; Vo Nhat Truong

    2011-01-01

    The Active Shape Model (ASM) is one of the most popular local texture modelsfor face alignment. It applies in many fields such as locating facial features in theimage, face synthesis, etc. However, the experimental results show that theaccuracy of the classical ASM for some applications is not high. This papersuggests some improvements on the classical ASM to increase the performanceof the model in the application: face alignment. Four of our major improvementsinclude: i) building a model com...

  3. Midbrain volume segmentation using active shape models and LBPs

    Science.gov (United States)

    Olveres, Jimena; Nava, Rodrigo; Escalante-Ramírez, Boris; Cristóbal, Gabriel; García-Moreno, Carla María.

    2013-09-01

    In recent years, the use of Magnetic Resonance Imaging (MRI) to detect different brain structures such as midbrain, white matter, gray matter, corpus callosum, and cerebellum has increased. This fact together with the evidence that midbrain is associated with Parkinson's disease has led researchers to consider midbrain segmentation as an important issue. Nowadays, Active Shape Models (ASM) are widely used in literature for organ segmentation where the shape is an important discriminant feature. Nevertheless, this approach is based on the assumption that objects of interest are usually located on strong edges. Such a limitation may lead to a final shape far from the actual shape model. This paper proposes a novel method based on the combined use of ASM and Local Binary Patterns for segmenting midbrain. Furthermore, we analyzed several LBP methods and evaluated their performance. The joint-model considers both global and local statistics to improve final adjustments. The results showed that our proposal performs substantially better than the ASM algorithm and provides better segmentation measurements.

  4. Active Shape Models Using Scale Invariant Feature Transform

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new active shape models (ASMs) was presented, which is driven by scale invariant feature transform (SIFT) local descriptor instead of normalizing first order derivative profiles in the original formulation, to segment lung fields from chest radiographs. The modified SIFT local descriptor, more distinctive than the general intensity and gradient features, is used to characterize the image features in the vicinity of each pixel at each resolution level during the segmentation optimization procedure. Experimental results show that the proposed method is more robust and accurate than the original ASMs in terms of an average overlap percentage and average contour distance in segmenting the lung fields from an available public database.

  5. 3D active shape modeling for cardiac MR and CT image segmentation

    NARCIS (Netherlands)

    Assen, Hans Christiaan van

    2006-01-01

    3D Active Shape Modeling is a technique to capture shape information from a training set containing characteristic shapes of, e.g., a heart. The description contains a mean shape, and shape variations (e.g. eigen deformations and eigen values). Many models based on these statistics, and used for med

  6. Abdomen and spinal cord segmentation with augmented active shape models.

    Science.gov (United States)

    Xu, Zhoubing; Conrad, Benjamin N; Baucom, Rebeccah B; Smith, Seth A; Poulose, Benjamin K; Landman, Bennett A

    2016-07-01

    Active shape models (ASMs) have been widely used for extracting human anatomies in medical images given their capability for shape regularization of topology preservation. However, sensitivity to model initialization and local correspondence search often undermines their performances, especially around highly variable contexts in computed-tomography (CT) and magnetic resonance (MR) images. In this study, we propose an augmented ASM (AASM) by integrating the multiatlas label fusion (MALF) and level set (LS) techniques into the traditional ASM framework. Using AASM, landmark updates are optimized globally via a region-based LS evolution applied on the probability map generated from MALF. This augmentation effectively extends the searching range of correspondent landmarks while reducing sensitivity to the image contexts and improves the segmentation robustness. We propose the AASM framework as a two-dimensional segmentation technique targeting structures with one axis of regularity. We apply AASM approach to abdomen CT and spinal cord (SC) MR segmentation challenges. On 20 CT scans, the AASM segmentation of the whole abdominal wall enables the subcutaneous/visceral fat measurement, with high correlation to the measurement derived from manual segmentation. On 28 3T MR scans, AASM yields better performances than other state-of-the-art approaches in segmenting white/gray matter in SC. PMID:27610400

  7. Face Alignment Using Active Shape Model And Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Le Hoang Thai; Vo Nhat Truong

    2011-02-01

    Full Text Available The Active Shape Model (ASM is one of the most popular local texture modelsfor face alignment. It applies in many fields such as locating facial features in theimage, face synthesis, etc. However, the experimental results show that theaccuracy of the classical ASM for some applications is not high. This papersuggests some improvements on the classical ASM to increase the performanceof the model in the application: face alignment. Four of our major improvementsinclude: i building a model combining Sobel filter and the 2-D profile in searchingface in image; ii applying Canny algorithm for the enhancement edge on image;iii Support Vector Machine (SVM is used to classify landmarks on face, in orderto determine exactly location of these landmarks support for ASM; ivautomatically adjust 2-D profile in the multi-level model based on the size of theinput image. The experimental results on Caltech face database and TechnicalUniversity of Denmark database (imm_face show that our proposedimprovement leads to far better performance.

  8. Ultrasound Common Carotid Artery Segmentation Based on Active Shape Model

    Directory of Open Access Journals (Sweden)

    Xin Yang

    2013-01-01

    Full Text Available Carotid atherosclerosis is a major reason of stroke, a leading cause of death and disability. In this paper, a segmentation method based on Active Shape Model (ASM is developed and evaluated to outline common carotid artery (CCA for carotid atherosclerosis computer-aided evaluation and diagnosis. The proposed method is used to segment both media-adventitia-boundary (MAB and lumen-intima-boundary (LIB on transverse views slices from three-dimensional ultrasound (3D US images. The data set consists of sixty-eight, 17 × 2 × 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80 mg atorvastatin and nine with placebo, who had carotid stenosis of 60% or more, at baseline and after three months of treatment. Manually outlined boundaries by expert are adopted as the ground truth for evaluation. For the MAB and LIB segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC of 94.4% ± 3.2% and 92.8% ± 3.3%, mean absolute distances (MAD of 0.26 ± 0.18 mm and 0.33 ± 0.21 mm, and maximum absolute distances (MAXD of 0.75 ± 0.46 mm and 0.84 ± 0.39 mm. It took 4.3 ± 0.5 mins to segment single 3D US images, while it took 11.7 ± 1.2 mins for manual segmentation. The method would promote the translation of carotid 3D US to clinical care for the monitoring of the atherosclerotic disease progression and regression.

  9. Modeling injection molding of net-shape active ceramic components.

    Energy Technology Data Exchange (ETDEWEB)

    Baer, Tomas (Gram Inc.); Cote, Raymond O.; Grillet, Anne Mary; Yang, Pin; Hopkins, Matthew Morgan; Noble, David R.; Notz, Patrick K.; Rao, Rekha Ranjana; Halbleib, Laura L.; Castaneda, Jaime N.; Burns, George Robert; Mondy, Lisa Ann; Brooks, Carlton, F.

    2006-11-01

    To reduce costs and hazardous wastes associated with the production of lead-based active ceramic components, an injection molding process is being investigated to replace the current machining process. Here, lead zirconate titanate (PZT) ceramic particles are suspended in a thermoplastic resin and are injected into a mold and allowed to cool. The part is then bisque fired and sintered to complete the densification process. To help design this new process we use a finite element model to describe the injection molding of the ceramic paste. Flow solutions are obtained using a coupled, finite-element based, Newton-Raphson numerical method based on the GOMA/ARIA suite of Sandia flow solvers. The evolution of the free surface is solved with an advanced level set algorithm. This approach incorporates novel methods for representing surface tension and wetting forces that affect the evolution of the free surface. Thermal, rheological, and wetting properties of the PZT paste are measured for use as input to the model. The viscosity of the PZT is highly dependent both on temperature and shear rate. One challenge in modeling the injection process is coming up with appropriate constitutive equations that capture relevant phenomenology without being too computationally complex. For this reason we model the material as a Carreau fluid and a WLF temperature dependence. Two-dimensional (2D) modeling is performed to explore the effects of the shear in isothermal conditions. Results indicate that very low viscosity regions exist near walls and that these results look similar in terms of meniscus shape and fill times to a simple Newtonian constitutive equation at the shear-thinned viscosity for the paste. These results allow us to pick a representative viscosity to use in fully three-dimensional (3D) simulation, which because of numerical complexities are restricted to using a Newtonian constitutive equation. Further 2D modeling at nonisothermal conditions shows that the choice of

  10. Active Shapes for Automatic 3D Modeling of Buildings

    NARCIS (Netherlands)

    Sirmacek, B.; Lindenbergh, R.C.

    2015-01-01

    Recent technological developments help us to acquire high quality 3D measurements of our urban environment. However, these measurements, which come as point clouds or Digital Surface Models (DSM), do not directly give 3D geometrical models of buildings. In addition to that, they are not suitable for

  11. Automatic Segmentation of Vertebrae from Radiographs: A Sample-Driven Active Shape Model Approach

    DEFF Research Database (Denmark)

    Mysling, Peter; Petersen, Peter Kersten; Nielsen, Mads;

    2011-01-01

    Segmentation of vertebral contours is an essential task in the design of automatic tools for vertebral fracture assessment. In this paper, we propose a novel segmentation technique which does not require operator interaction. The proposed technique solves the segmentation problem in a hierarchical...... manner. In a first phase, a coarse estimate of the overall spine alignment and the vertebra locations is computed using a shape model sampling scheme. These samples are used to initialize a second phase of active shape model search, under a nonlinear model of vertebra appearance. The search...... is constrained by a conditional shape model, based on the variability of the coarse spine location estimates. The technique is evaluated on a data set of manually annotated lumbar radiographs. The results compare favorably to the previous work in automatic vertebra segmentation, in terms of both segmentation...

  12. A Framework of Vertebra Segmentation Using the Active Shape Model-Based Approach

    OpenAIRE

    Mohammed Benjelloun; Saïd Mahmoudi; Fabian Lecron

    2011-01-01

    We propose a medical image segmentation approach based on the Active Shape Model theory. We apply this method for cervical vertebra detection. The main advantage of this approach is the application of a statistical model created after a training stage. Thus, the knowledge and interaction of the domain expert intervene in this approach. Our application allows the use of two different models, that is, a global one (with several vertebrae) and a local one (with a single vertebra). Two modes of s...

  13. A Nonparametric Shape Prior Constrained Active Contour Model for Segmentation of Coronaries in CTA Images

    Directory of Open Access Journals (Sweden)

    Yin Wang

    2014-01-01

    Full Text Available We present a nonparametric shape constrained algorithm for segmentation of coronary arteries in computed tomography images within the framework of active contours. An adaptive scale selection scheme, based on the global histogram information of the image data, is employed to determine the appropriate window size for each point on the active contour, which improves the performance of the active contour model in the low contrast local image regions. The possible leakage, which cannot be identified by using intensity features alone, is reduced through the application of the proposed shape constraint, where the shape of circular sampled intensity profile is used to evaluate the likelihood of current segmentation being considered vascular structures. Experiments on both synthetic and clinical datasets have demonstrated the efficiency and robustness of the proposed method. The results on clinical datasets have shown that the proposed approach is capable of extracting more detailed coronary vessels with subvoxel accuracy.

  14. Modeling of Asteroid Shapes

    CERN Document Server

    Kokorev, Andrii

    2016-01-01

    In this article we consider different methods of modeling asteroid shapes, especially lightcurve inversion technique, and scattering laws used for it. We also introduce our program, which constructs lightcurves for a given asteroid shape model. It can be used to comparing shape model with observational data.

  15. Dendritic spine shape analysis using disjunctive normal shape models

    OpenAIRE

    Ghani, Muhammad Usman; Mesadi, Fitsum; Demir Kanık, Sümerya Ümmühan; Demir Kanik, Sumerya Ummuhan; Argunşah, Ali Özgür; Argunsah, Ali Ozgur; Israely, Inbal; Ünay, Devrim; Unay, Devrim; Taşdizen, Tolga; Tasdizen, Tolga; Çetin, Müjdat; Cetin, Mujdat

    2016-01-01

    Analysis of dendritic spines is an essential task to understand the functional behavior of neurons. Their shape variations are known to be closely linked with neuronal activities. Spine shape analysis in particular, can assist neuroscientists to identify this relationship. A novel shape representation has been proposed recently, called Disjunctive Normal Shape Models (DNSM). DNSM is a parametric shape representation and has proven to be successful in several segmentation problems. In this pap...

  16. A Framework of Vertebra Segmentation Using the Active Shape Model-Based Approach

    Directory of Open Access Journals (Sweden)

    Mohammed Benjelloun

    2011-01-01

    Full Text Available We propose a medical image segmentation approach based on the Active Shape Model theory. We apply this method for cervical vertebra detection. The main advantage of this approach is the application of a statistical model created after a training stage. Thus, the knowledge and interaction of the domain expert intervene in this approach. Our application allows the use of two different models, that is, a global one (with several vertebrae and a local one (with a single vertebra. Two modes of segmentation are also proposed: manual and semiautomatic. For the manual mode, only two points are selected by the user on a given image. The first point needs to be close to the lower anterior corner of the last vertebra and the second near the upper anterior corner of the first vertebra. These two points are required to initialize the segmentation process. We propose to use the Harris corner detector combined with three successive filters to carry out the semiautomatic process. The results obtained on a large set of X-ray images are very promising.

  17. A framework of vertebra segmentation using the active shape model-based approach.

    Science.gov (United States)

    Benjelloun, Mohammed; Mahmoudi, Saïd; Lecron, Fabian

    2011-01-01

    We propose a medical image segmentation approach based on the Active Shape Model theory. We apply this method for cervical vertebra detection. The main advantage of this approach is the application of a statistical model created after a training stage. Thus, the knowledge and interaction of the domain expert intervene in this approach. Our application allows the use of two different models, that is, a global one (with several vertebrae) and a local one (with a single vertebra). Two modes of segmentation are also proposed: manual and semiautomatic. For the manual mode, only two points are selected by the user on a given image. The first point needs to be close to the lower anterior corner of the last vertebra and the second near the upper anterior corner of the first vertebra. These two points are required to initialize the segmentation process. We propose to use the Harris corner detector combined with three successive filters to carry out the semiautomatic process. The results obtained on a large set of X-ray images are very promising. PMID:21826134

  18. Enhancing the T-shaped learning profile when teaching hydrology using data, modeling, and visualization activities

    Science.gov (United States)

    Sanchez, Christopher A.; Ruddell, Benjamin L.; Schiesser, Roy; Merwade, Venkatesh

    2016-03-01

    Previous research has suggested that the use of more authentic learning activities can produce more robust and durable knowledge gains. This is consistent with calls within civil engineering education, specifically hydrology, that suggest that curricula should more often include professional perspective and data analysis skills to better develop the "T-shaped" knowledge profile of a professional hydrologist (i.e., professional breadth combined with technical depth). It was expected that the inclusion of a data-driven simulation lab exercise that was contextualized within a real-world situation and more consistent with the job duties of a professional in the field, would provide enhanced learning and appreciation of job duties beyond more conventional paper-and-pencil exercises in a lower-division undergraduate course. Results indicate that while students learned in both conditions, learning was enhanced for the data-driven simulation group in nearly every content area. This pattern of results suggests that the use of data-driven modeling and visualization activities can have a significant positive impact on instruction. This increase in learning likely facilitates the development of student perspective and conceptual mastery, enabling students to make better choices about their studies, while also better preparing them for work as a professional in the field.

  19. Modeling, analysis, and validation of an active T-shaped noise barrier.

    Science.gov (United States)

    Fan, Rongping; Su, Zhongqing; Cheng, Li

    2013-09-01

    With ever-increasing land traffic, abatement of traffic noise using noise barriers remains significant, yet it is a challenging task due to spatial competition with other infrastructure. In this study, a deep insight into the diffraction characteristics of acoustic fields near noise barriers of various geometries and surface conditions was achieved using numerical simulations. A T-shaped passive noise barrier with acoustically soft upper surfaces was demonstrated to outperform other candidates in a middle- or high-frequency range. Based on attributes of the acoustic field diffracted by T-shaped barriers, an active control strategy was developed to revamp the T-shaped barrier, in which a filtered minimax algorithm was established to drive the secondary sound sources. This algorithm resulted in more uniformly distributed residual sound fields than a filtered-X least mean square algorithm. Performance of the actively controlled barrier was evaluated at different positions and spacings of secondary sound sources and error sensors, leading to a series of optimal criteria for the design of active noise barriers. A prototype was fabricated and validated experimentally, manifesting particular effectiveness in insulating low-frequency noise, supplementing well the capacity of a passive T-shaped barrier which is effective in the middle- or high-frequency range.

  20. Markov Random Field Restoration of Point Correspondences for Active Shape Modelling

    DEFF Research Database (Denmark)

    Hilger, Klaus Baggesen; Paulsen, Rasmus Reinhold; Larsen, Rasmus

    2004-01-01

    model mesh to the target shapes. When this is done by a nearest neighbour projection it can result in folds and inhomogeneities in the correspondence vector field. The novelty in this paper is the use and extension of a Markov random field regularisation of the correspondence field. The correspondence...... field is regarded as a collection of random variables, and using the Hammersley-Clifford theorem it is proved that it can be treated as a Markov Random Field. The problem of finding the optimal correspondence field is cast into a Bayesian framework for Markov Random Field restoration, where the prior...... distribution is a smoothness term and the observation model is the curvature of the shapes. The Markov Random Field is optimised using a combination of Gibbs sampling and the Metropolis-Hasting algorithm. The parameters of the model is found using a leave-one-out approach. The method leads to a generative...

  1. 3D active shape models of human brain structures: application to patient-specific mesh generation

    Science.gov (United States)

    Ravikumar, Nishant; Castro-Mateos, Isaac; Pozo, Jose M.; Frangi, Alejandro F.; Taylor, Zeike A.

    2015-03-01

    The use of biomechanics-based numerical simulations has attracted growing interest in recent years for computer-aided diagnosis and treatment planning. With this in mind, a method for automatic mesh generation of brain structures of interest, using statistical models of shape (SSM) and appearance (SAM), for personalised computational modelling is presented. SSMs are constructed as point distribution models (PDMs) while SAMs are trained using intensity profiles sampled from a training set of T1-weighted magnetic resonance images. The brain structures of interest are, the cortical surface (cerebrum, cerebellum & brainstem), lateral ventricles and falx-cerebri membrane. Two methods for establishing correspondences across the training set of shapes are investigated and compared (based on SSM quality): the Coherent Point Drift (CPD) point-set registration method and B-spline mesh-to-mesh registration method. The MNI-305 (Montreal Neurological Institute) average brain atlas is used to generate the template mesh, which is deformed and registered to each training case, to establish correspondence over the training set of shapes. 18 healthy patients' T1-weightedMRimages form the training set used to generate the SSM and SAM. Both model-training and model-fitting are performed over multiple brain structures simultaneously. Compactness and generalisation errors of the BSpline-SSM and CPD-SSM are evaluated and used to quantitatively compare the SSMs. Leave-one-out cross validation is used to evaluate SSM quality in terms of these measures. The mesh-based SSM is found to generalise better and is more compact, relative to the CPD-based SSM. Quality of the best-fit model instance from the trained SSMs, to test cases are evaluated using the Hausdorff distance (HD) and mean absolute surface distance (MASD) metrics.

  2. A magnetic resonance spectroscopy driven initialization scheme for active shape model based prostate segmentation.

    Science.gov (United States)

    Toth, Robert; Tiwari, Pallavi; Rosen, Mark; Reed, Galen; Kurhanewicz, John; Kalyanpur, Arjun; Pungavkar, Sona; Madabhushi, Anant

    2011-04-01

    Segmentation of the prostate boundary on clinical images is useful in a large number of applications including calculation of prostate volume pre- and post-treatment, to detect extra-capsular spread, and for creating patient-specific anatomical models. Manual segmentation of the prostate boundary is, however, time consuming and subject to inter- and intra-reader variability. T2-weighted (T2-w) magnetic resonance (MR) structural imaging (MRI) and MR spectroscopy (MRS) have recently emerged as promising modalities for detection of prostate cancer in vivo. MRS data consists of spectral signals measuring relative metabolic concentrations, and the metavoxels near the prostate have distinct spectral signals from metavoxels outside the prostate. Active Shape Models (ASM's) have become very popular segmentation methods for biomedical imagery. However, ASMs require careful initialization and are extremely sensitive to model initialization. The primary contribution of this paper is a scheme to automatically initialize an ASM for prostate segmentation on endorectal in vivo multi-protocol MRI via automated identification of MR spectra that lie within the prostate. A replicated clustering scheme is employed to distinguish prostatic from extra-prostatic MR spectra in the midgland. The spatial locations of the prostate spectra so identified are used as the initial ROI for a 2D ASM. The midgland initializations are used to define a ROI that is then scaled in 3D to cover the base and apex of the prostate. A multi-feature ASM employing statistical texture features is then used to drive the edge detection instead of just image intensity information alone. Quantitative comparison with another recent ASM initialization method by Cosio showed that our scheme resulted in a superior average segmentation performance on a total of 388 2D MRI sections obtained from 32 3D endorectal in vivo patient studies. Initialization of a 2D ASM via our MRS-based clustering scheme resulted in an average

  3. Use of quantitative shape-activity relationships to model the photoinduced toxicity of polycyclic aromatic hydrocarbons: Electron density shape features accurately predict toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Mezey, P.G.; Zimpel, Z.; Warburton, P.; Walker, P.D.; Irvine, D.G. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada); Huang, X.D.; Dixon, D.G.; Greenberg, B.M. [Univ. of Waterloo, Ontario (Canada). Dept. of Biology

    1998-07-01

    The quantitative shape-activity relationship (QShAR) methodology, based on accurate three-dimensional electron densities and detailed shape analysis methods, has been applied to a Lemna gibba photoinduced toxicity data set of 16 polycyclic aromatic hydrocarbon (PAH) molecules. In the first phase of the studies, a shape fragment QShAR database of PAHs was developed. The results provide a very good match to toxicity based on a combination of the local shape features of single rings in comparison to the central ring of anthracene and a more global shape feature involving larger molecular fragments. The local shape feature appears as a descriptor of the susceptibility of PAHs to photomodification and the global shape feature is probably related to photosensitization activity.

  4. Shape of optimal active flagella

    CERN Document Server

    Eloy, Christophe

    2013-01-01

    Many eukaryotic cells use the active waving motion of flexible flagella to self-propel in viscous fluids. However, the criteria governing the selection of particular flagellar waveforms among all possible shapes has proved elusive so far. To address this question, we derive computationally the optimal shape of an internally-forced periodic planar flagellum deforming as a travelling wave. The optimum is here defined as the shape leading to a given swimming speed with minimum energetic cost. To calculate the energetic cost though, we consider the irreversible internal power expanded by the molecular motors forcing the flagellum, only a portion of which ending up dissipated in the fluid. This optimisation approach allows us to derive a family of shapes depending on a single dimensionless number quantifying the relative importance of elastic to viscous effects: the Sperm number. The computed optimal shapes are found to agree with the waveforms observed on spermatozoon of marine organisms, thus suggesting that the...

  5. Shape Modelling Using Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    2001-01-01

    of Active Shape Models by Timothy Cootes and Christopher Taylor by building new information into the model. This new information consists of two types of prior knowledge. First, in many situation we will be given an ordering of the shapes of the training set. This situation occurs when the shapes......This paper addresses the problems of generating a low dimensional representation of the shape variation present in a training set after alignment using Procrustes analysis and projection into shape tangent space. We will extend the use of principal components analysis in the original formulation....... Both these types of knowledge may be used to defined Shape Maximum Autocorrelation Factors. The resulting point distribution models are compared to ordinary principal components analysis using leave-one-out validation....

  6. Women in Shape Modeling Workshop

    CERN Document Server

    Tari, Sibel

    2015-01-01

    Presenting the latest research from the growing field of mathematical shape analysis, this volume is comprised of the collaborations of participants of the Women in Shape Modeling (WiSh) workshop, held at UCLA's Institute for Pure and Applied Mathematics in July 2013. Topics include: Simultaneous spectral and spatial analysis of shape Dimensionality reduction and visualization of data in tree-spaces, such as classes of anatomical trees like airways and blood vessels Geometric shape segmentation, exploring shape segmentation from a Gestalt perspective, using information from the Blum medial axis of edge fragments in an image Representing and editing self-similar details on 3D shapes, studying shape deformation and editing techniques Several chapters in the book directly address the problem of continuous measures of context-dependent nearness and right shape models. Medical and biological applications have been a major source of motivation in shape research, and key topics are examined here in detail. All...

  7. Modeling of electric resistance of shape memory alloys: self-sensing for temperature and actuation control of active hybrid composites

    Science.gov (United States)

    Nissle, Sebastian; Hübler, Moritz; Gurka, Martin

    2016-04-01

    For actuation purposes active hybrid structures made of fiber reinforced polymers (FRP) and shape memory alloys (SMA) enable substantial savings concerning weight, space and cost. Such structures allow realizing new functions which are more or less impossible with commonly used systems consisting of the structure and the actuator as separated elements, e.g. morphing winglets in aeronautics. But there are also some challenges that still need to be addressed. For the successful application of SMA FRP composites a precise control of temperature is essential, as this is the activating quantity to reach the required deformation of the structure without overloading the active material. However, a direct measurement of the temperature is difficult due to the complete integration of SMA in the hybrid structure. Also the deformation of the structure which depends on the temperature, the stiffness of the hybrid structure and external loads is hard to determine. An opportunity for controlling the activation is provided by the special behavior of the electrical resistance of SMA. During the phase transformation of the SMA - also causing the actuation travel - the resistance drops with rising temperature. This behavior can be exploited for control purposes, especially as the electrical resistance can be easily measured during the activation done by Joule heating. As shown in this contribution, theoretical modelling and experimental tests provide a load-independent self-sensing control-concept of SMA-FRP-hybrid-structures.

  8. Robust boundary detection and tracking of left ventricles on ultrasound images using active shape model and ant colony optimization.

    Science.gov (United States)

    Zhang, Yaonan; Gao, Yuan; Jiao, Jinling; Li, Xian; Li, Sai; Yang, Jun

    2014-01-01

    Information regarding the motion, strain and synchronization are important for cardiac diagnosis and therapy. Extraction of such information from ultrasound images remains an open problem till today. In this paper, a novel method is proposed to extract the boundaries of left ventricles and track these boundaries in ultrasound image sequences. The initial detection of boundaries was performed by an active shape model scheme. Subsequent refinement of the boundaries was done by using local variance information of the images. The main objective of this paper is the formulation of a new boundary tracking algorithm using ant colony optimization technique. The experiments conducted on the simulated image sequences and the real cardiac ultrasound image sequences shows a positive and promising result. PMID:25226995

  9. A magnetic resonance spectroscopy driven initialization scheme for active shape model based prostate segmentation

    OpenAIRE

    Toth, Robert; Tiwari, Pallavi; Rosen, Mark; Reed, Galen; Kurhanewicz, John; Kalyanpur, Arjun; Pungavkar, Sona; Madabhushi, Anant

    2010-01-01

    Segmentation of the prostate boundary on clinical images is useful in a large number of applications including calculation of prostate volume pre- and post-treatment, to detect extra-capsular spread, and for creating patient-specific anatomical models. Manual segmentation of the prostate boundary is, however, time consuming and subject to inter- and intra-reader variability. T2-weighted (T2-w) magnetic resonance (MR) structural imaging (MRI) and MR spectroscopy (MRS) have recently emerged as ...

  10. Thermaly Active Structures for Shape Morphing Applications

    Directory of Open Access Journals (Sweden)

    Gildas L'Hostis

    2012-01-01

    Full Text Available For shape morphing application, thermal activation coupling to a bimetallic strip effect can be a substitute for classical actuators, piezoelectrical or shape memory alloys. The controlled behaviour of composite material (CBCM is a thermaly activated composite material. The thermal activation is made thanks to carbon yarns which are connected to a power supply. If the anisotropy of the structure is well organized, the desired deformation is reached when the temperature within the composite is rising. To obtain a CBCM morphing composite structure, it is necessary to design a specific structure. The aim of this work is to show that it is possible to adapt the CBCM principle in order to transform any kind of classical composite structure to an active structure. The first part of this work consists in presenting the experimental results for two examples of composite beams. The second part is about the active structure FEM modeling and the development of adapted tools for this particular design.

  11. Towards robust and effective shape modeling: sparse shape composition.

    Science.gov (United States)

    Zhang, Shaoting; Zhan, Yiqiang; Dewan, Maneesh; Huang, Junzhou; Metaxas, Dimitris N; Zhou, Xiang Sean

    2012-01-01

    Organ shape plays an important role in various clinical practices, e.g., diagnosis, surgical planning and treatment evaluation. It is usually derived from low level appearance cues in medical images. However, due to diseases and imaging artifacts, low level appearance cues might be weak or misleading. In this situation, shape priors become critical to infer and refine the shape derived by image appearances. Effective modeling of shape priors is challenging because: (1) shape variation is complex and cannot always be modeled by a parametric probability distribution; (2) a shape instance derived from image appearance cues (input shape) may have gross errors; and (3) local details of the input shape are difficult to preserve if they are not statistically significant in the training data. In this paper we propose a novel Sparse Shape Composition model (SSC) to deal with these three challenges in a unified framework. In our method, a sparse set of shapes in the shape repository is selected and composed together to infer/refine an input shape. The a priori information is thus implicitly incorporated on-the-fly. Our model leverages two sparsity observations of the input shape instance: (1) the input shape can be approximately represented by a sparse linear combination of shapes in the shape repository; (2) parts of the input shape may contain gross errors but such errors are sparse. Our model is formulated as a sparse learning problem. Using L1 norm relaxation, it can be solved by an efficient expectation-maximization (EM) type of framework. Our method is extensively validated on two medical applications, 2D lung localization in X-ray images and 3D liver segmentation in low-dose CT scans. Compared to state-of-the-art methods, our model exhibits better performance in both studies. PMID:21963296

  12. Shaping Neuronal Network Activity by Presynaptic Mechanisms.

    Directory of Open Access Journals (Sweden)

    Ayal Lavi

    2015-09-01

    Full Text Available Neuronal microcircuits generate oscillatory activity, which has been linked to basic functions such as sleep, learning and sensorimotor gating. Although synaptic release processes are well known for their ability to shape the interaction between neurons in microcircuits, most computational models do not simulate the synaptic transmission process directly and hence cannot explain how changes in synaptic parameters alter neuronal network activity. In this paper, we present a novel neuronal network model that incorporates presynaptic release mechanisms, such as vesicle pool dynamics and calcium-dependent release probability, to model the spontaneous activity of neuronal networks. The model, which is based on modified leaky integrate-and-fire neurons, generates spontaneous network activity patterns, which are similar to experimental data and robust under changes in the model's primary gain parameters such as excitatory postsynaptic potential and connectivity ratio. Furthermore, it reliably recreates experimental findings and provides mechanistic explanations for data obtained from microelectrode array recordings, such as network burst termination and the effects of pharmacological and genetic manipulations. The model demonstrates how elevated asynchronous release, but not spontaneous release, synchronizes neuronal network activity and reveals that asynchronous release enhances utilization of the recycling vesicle pool to induce the network effect. The model further predicts a positive correlation between vesicle priming at the single-neuron level and burst frequency at the network level; this prediction is supported by experimental findings. Thus, the model is utilized to reveal how synaptic release processes at the neuronal level govern activity patterns and synchronization at the network level.

  13. Shape Restoration by Active Self-Assembly

    Directory of Open Access Journals (Sweden)

    D. Arbuckle

    2005-01-01

    Full Text Available Shape restoration is defined as the problem of constructing a desired, or goal, solid shape Sg by growing an initial solid Si, which is a subset of the goal but is otherwise unknown. This definition attempts to capture abstractly a situation that often arises in the physical world when a solid object loses its desired shape due to wear and tear, corrosion or other phenomena. For example, if the top of the femur becomes distorted, the hip joint no longer functions properly and may have to be replaced surgically. Growing it in place back to its original shape would be an attractive alternative to replacement. This paper presents a solution to the shape restoration problem by using autonomous assembly agents (robots that self-assemble to fill the volume between Sg and Si. If the robots have very small dimension (micro or nano, the desired shape is approximated with high accuracy. The assembly agents initially execute a random walk. When two robots meet, they may exchange a small number of messages. The robot behavior is controlled by a finite state machine with a small number of states. Communication contact models chemical communication, which is likely to be the medium of choice for robots at the nanoscale, while small state and small messages are limitations that also are expected of nanorobots. Simulations presented here show that swarms of such robots organize themselves to achieve shape restoration by using distributed algorithms. This is one more example of an interesting geometric problem that can be solved by the Active Self-Assembly paradigm introduced in previous papers by the authors.

  14. Shaping frequency response of a vibrating plate for passive and active control applications by simultaneous optimization of arrangement of additional masses and ribs. Part I: Modeling

    Science.gov (United States)

    Wrona, Stanislaw; Pawelczyk, Marek

    2016-03-01

    An ability to shape frequency response of a vibrating plate according to precisely defined demands has a very high practical potential. It can be applied to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings by using both passive and active control. The proposed method is based on mounting severaladditional ribs and masses (passive and/or active) to the plate surface at locations followed from an optimization process. This paper, Part I, concerns derivation of a mathematical model of the plate with attached elements in the function of their shape and placement. The model is validated by means of simulations and laboratory experiments, and compared with models known from the literature. This paper is followed by a companion paper, Part II, where the optimization process is described. It includes arrangement of passive elements as well as actuators and sensors to improve controllability and observability measures, if active control is concerned.

  15. Statistical models of shape optimisation and evaluation

    CERN Document Server

    Davies, Rhodri; Taylor, Chris

    2008-01-01

    Addresses one of the key issues in shape modelling: that of establishing a meaningful correspondence between a set of shapesUses a novel approach to establishing correspondence by casting model-building as an optimisation problem Includes practical examples of applications for both 2D and 3D sets of shapesFull implementation details, perviously unpublished, provided

  16. A Heuristic Image Search Algorithm for Active Shape Model Segmentation of the Caudate Nucleus and Hippocampus in Brain MR Images of Children with FASD

    Directory of Open Access Journals (Sweden)

    A A Eicher

    2012-09-01

    Full Text Available Magnetic Resonance Imaging provides a non-invasive means to study the neural correlates of Fetal Alcohol Spectrum Disorder (FASD - the most common form of preventable mental retardation worldwide. One approach aims to detect brain abnormalities through an assessment of volume and shape of two sub-cortical structures, the caudate nucleus and hippocampus. We present a method for automatically segmenting these structures from high-resolution MR images captured as part of an ongoing study into the neural correlates of FASD. Our method incorporates an Active Shape Model, which is used to learn shape variation from manually segmented training data. A modified discrete Geometrically Deformable Model is used to generate point correspondence between training models. An ASM is then created from the landmark points. Experiments were conducted on the image search phase of ASM segmentation, in order to find the technique best suited to segmentation of the hippocampus and caudate nucleus. Various popular image search techniques were tested, including an edge detection method and a method based on grey profile Mahalanobis distance measurement. A novel heuristic image search method was also developed and tested. This heuristic method improves image segmentation by taking advantage of characteristics specific to the target data, such as a relatively homogeneous tissue colour in target structures. Results show that ASMs that use the heuristic image search technique produce the most accurate segmentations. An ASM constructed using this technique will enable researchers to quickly, reliably, and automatically segment test data for use in the FASD study.

  17. Generalized Models for Rock Joint Surface Shapes

    Directory of Open Access Journals (Sweden)

    Shigui Du

    2014-01-01

    Full Text Available Generalized models of joint surface shapes are the foundation for mechanism studies on the mechanical effects of rock joint surface shapes. Based on extensive field investigations of rock joint surface shapes, generalized models for three level shapes named macroscopic outline, surface undulating shape, and microcosmic roughness were established through statistical analyses of 20,078 rock joint surface profiles. The relative amplitude of profile curves was used as a borderline for the division of different level shapes. The study results show that the macroscopic outline has three basic features such as planar, arc-shaped, and stepped; the surface undulating shape has three basic features such as planar, undulating, and stepped; and the microcosmic roughness has two basic features such as smooth and rough.

  18. Quantitative control of organ shape by combinatorial gene activity.

    Directory of Open Access Journals (Sweden)

    Min-Long Cui

    Full Text Available The development of organs with particular shapes, like wings or flowers, depends on regional activity of transcription factors and signalling molecules. However, the mechanisms that link these molecular activities to the morphogenetic events underlying shape are poorly understood. Here we describe a combination of experimental and computational approaches that address this problem, applying them to a group of genes controlling flower shape in the Snapdragon (Antirrhinum. Four transcription factors are known to play a key role in the control of floral shape and asymmetry in Snapdragon. We use quantitative shape analysis of mutants for these factors to define principal components underlying flower shape variation. We show that each transcription factor has a specific effect on the shape and size of regions within the flower, shifting the position of the flower in shape space. These shifts are further analysed by generating double mutants and lines that express some of the genes ectopically. By integrating these observations with known gene expression patterns and interactions, we arrive at a combinatorial scheme for how regional effects on shape are genetically controlled. We evaluate our scheme by incorporating the proposed interactions into a generative model, where the developing flower is treated as a material sheet that grows according to how genes modify local polarities and growth rates. The petal shapes generated by the model show a good quantitative match with those observed experimentally for each petal in numerous genotypes, thus validating the hypothesised scheme. This article therefore shows how complex shapes can be accounted for by combinatorial effects of transcription factors on regional growth properties. This finding has implications not only for how shapes develop but also for how they may have evolved through tinkering with transcription factors and their targets.

  19. A NEW MODEL OF SHAPE MEMORY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    朱祎国; 吕和祥; 杨大智

    2002-01-01

    A new constitutive model of shape memory alloys ( SMAs ) based on Tanaka' s martensite fraction exponential expression is produced. This new model can present recoverable shape memory strain during different phase transformation, and reflect the action of martensite reorientation. Also it can overcome the defect of Tanaka's Model when the SMAs' microstructure is fully martensite . The model is very simple and suitable for using,and the correct behavior of the model is proved by test.

  20. Minimum Description Length Shape and Appearance Models

    DEFF Research Database (Denmark)

    Thodberg, Hans Henrik

    2003-01-01

    The Minimum Description Length (MDL) approach to shape modelling is reviewed. It solves the point correspondence problem of selecting points on shapes defined as curves so that the points correspond across a data set. An efficient numerical implementation is presented and made available as open s...

  1. Fourier Series, the DFT and Shape Modelling

    DEFF Research Database (Denmark)

    Skoglund, Karl

    2004-01-01

    This report provides an introduction to Fourier series, the discrete Fourier transform, complex geometry and Fourier descriptors for shape analysis. The content is aimed at undergraduate and graduate students who wish to learn about Fourier analysis in general, as well as its application to shape...... modelling and analysis....

  2. Automatic classification of squamosal abnormality in micro-CT images for the evaluation of rabbit fetal skull defects using active shape models

    Science.gov (United States)

    Chen, Antong; Dogdas, Belma; Mehta, Saurin; Bagchi, Ansuman; Wise, L. David; Winkelmann, Christopher

    2014-03-01

    High-throughput micro-CT imaging has been used in our laboratory to evaluate fetal skeletal morphology in developmental toxicology studies. Currently, the volume-rendered skeletal images are visually inspected and observed abnormalities are reported for compounds in development. To improve the efficiency and reduce human error of the evaluation, we implemented a framework to automate the evaluation process. The framework starts by dividing the skull into regions of interest and then measuring various geometrical characteristics. Normal/abnormal classification on the bone segments is performed based on identifying statistical outliers. In pilot experiments using rabbit fetal skulls, the majority of the skeletal abnormalities can be detected successfully in this manner. However, there are shape-based abnormalities that are relatively subtle and thereby difficult to identify using the geometrical features. To address this problem, we introduced a model-based approach and applied this strategy on the squamosal bone. We will provide details on this active shape model (ASM) strategy for the identification of squamosal abnormalities and show that this method improved the sensitivity of detecting squamosal-related abnormalities from 0.48 to 0.92.

  3. Region-based active contour with noise and shape priors

    CERN Document Server

    Lecellier, François; Fadili, Jalal; Aubert, Gilles; Revenu, Marinette; Saloux, Eric

    2008-01-01

    In this paper, we propose to combine formally noise and shape priors in region-based active contours. On the one hand, we use the general framework of exponential family as a prior model for noise. On the other hand, translation and scale invariant Legendre moments are considered to incorporate the shape prior (e.g. fidelity to a reference shape). The combination of the two prior terms in the active contour functional yields the final evolution equation whose evolution speed is rigorously derived using shape derivative tools. Experimental results on both synthetic images and real life cardiac echography data clearly demonstrate the robustness to initialization and noise, flexibility and large potential applicability of our segmentation algorithm.

  4. Body shape model, physical activity and eating behaviour Modelo estético corporal, actividad física y conducta alimentaria

    Directory of Open Access Journals (Sweden)

    I. Jáuregui Lobera

    2011-02-01

    Full Text Available Objectives: Research on the influence of body shape model on adolescent males is scarce. The current study aimed to assess this influence among adult males involved in intense physical activity and to determine its relationship to eating behaviour. Possible variations between 1998 and 2008 were also analysed. Method: A total of 950 males (672 in 1998 and 278 in 2008, all aspiring professional soldiers, were studied using the Questionnaire of Influences on Body Shape Model (CIMEC-V and the Eating Attitudes Test-40 (EAT-40, as well as by assessing their physical/sporting activity and body mass index (BMI. Results: Scores on the CIMEC-V were significantly correlated with the EAT-40 and BMI. As regards physical activity the only positive correlation referred to gym-based exercise. A cluster analysis revealed two subgroups with respect to physical activity, BMI, and scores on the CIMEC-V and EAT-40. One of them scored higher on these three variables and they also had a BMI > 25. The comparative study of data from 1998 and 2008 showed significant changes in some variables. Conclusions: Generally, the results differ considerably from those reported for younger samples (which would suggest a lower risk of disordered eating behaviour. However, there is a higher risk group in which the influence of body shape models, physical activity and eating behaviour are related to greater body volume. The influence of the body shape model on males has increased, especially as regards the influence of friends and in terms of behaviours aimed at weight loss.Objetivos: La investigación sobre la influencia del modelo estético corporal en varones adolescentes es escasa. El presente estudio analiza tal influencia en varones con intensa actividad física y su influencia en la conducta alimentaria. También fueron analizadas las posibles variaciones entre 1998 y 2008. Método: Un total de 950 varones (672 en 1998 y 278 en 2008, aspirante a soldado profesional, fueron

  5. Minimum Description Length Shape and Appearance Models

    DEFF Research Database (Denmark)

    Thodberg, Hans Henrik

    2003-01-01

    The Minimum Description Length (MDL) approach to shape modelling is reviewed. It solves the point correspondence problem of selecting points on shapes defined as curves so that the points correspond across a data set. An efficient numerical implementation is presented and made available as open s...... source Matlab code. The problems with the early MDL approaches are discussed. Finally the MDL approach is extended to an MDL Appearance Model, which is proposed as a means to perform unsupervised image segmentation....

  6. Correction of dental artifacts within the anatomical surface in PET/MRI using Active Shape Models and k-Nearest-Neighbors

    DEFF Research Database (Denmark)

    Ladefoged, Claes N.; Andersen, Flemming L.; Keller, Sune H.;

    2014-01-01

    n combined PET/MR, attenuation correction (AC) is performed indirectly based on the available MR image information. Metal implant-induced susceptibility artifacts and subsequent signal voids challenge MR-based AC. Several papers acknowledge the problem in PET attenuation correction when dental...... artifacts are ignored, but none of them attempts to solve the problem. We propose a clinically feasible correction method which combines Active Shape Models (ASM) and k- Nearest-Neighbors (kNN) into a simple approach which finds and corrects the dental artifacts within the surface boundaries of the patient...... vector, and fill the artifact voxels with a value representing soft tissue. We tested the method using fourteen patients without artifacts, and eighteen patients with dental artifacts of varying sizes within the anatomical surface of the head/neck region. Though the method wrongly filled a small volume...

  7. Modeling shape-memory behavior of dielectric elastomers

    Science.gov (United States)

    Xiao, Rui

    2016-04-01

    In this study, we present a constitutive model to couple the shape memory and dielectric behaviors of polymers. The model adopted multiple relaxation processes and temperature-dependent relaxation time to describe the glass transition behaviors. The model was applied to simulate the thermal-mechanical-electrical behaviors of the dielectric elastomer VHB 4905. We investigated the influence of deformation temperature, voltage rate, relaxation time on the electromechanical and shape-memory behavior of dielectric elastomers. This work provides a method for combining the shape-memory properties and electroactive polymers, which can expand the applications of these soft active materials.

  8. Statistical shape and appearance models of bones.

    Science.gov (United States)

    Sarkalkan, Nazli; Weinans, Harrie; Zadpoor, Amir A

    2014-03-01

    When applied to bones, statistical shape models (SSM) and statistical appearance models (SAM) respectively describe the mean shape and mean density distribution of bones within a certain population as well as the main modes of variations of shape and density distribution from their mean values. The availability of this quantitative information regarding the detailed anatomy of bones provides new opportunities for diagnosis, evaluation, and treatment of skeletal diseases. The potential of SSM and SAM has been recently recognized within the bone research community. For example, these models have been applied for studying the effects of bone shape on the etiology of osteoarthritis, improving the accuracy of clinical osteoporotic fracture prediction techniques, design of orthopedic implants, and surgery planning. This paper reviews the main concepts, methods, and applications of SSM and SAM as applied to bone.

  9. Multi-shape active composites by 3D printing of digital shape memory polymers

    Science.gov (United States)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-04-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

  10. Multi-shape active composites by 3D printing of digital shape memory polymers.

    Science.gov (United States)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L; Qi, H Jerry

    2016-04-13

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers - digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

  11. Multi-shape active composites by 3D printing of digital shape memory polymers.

    Science.gov (United States)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L; Qi, H Jerry

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers - digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications. PMID:27071543

  12. Multi-shape active composites by 3D printing of digital shape memory polymers

    Science.gov (United States)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications. PMID:27071543

  13. Conditional shape models for cardiac motion estimation

    DEFF Research Database (Denmark)

    Metz, C.T.; Baka, N.; Kirisli, H.A.;

    2010-01-01

    We propose a conditional statistical shape model to predict patient specific cardiac motion from the 3D end-diastolic CTA scan. The model is built from 4D CTA sequences by combining atlas based segmentation and 4D registration. Cardiac motion estimation is, for example, relevant in the dynamic al...

  14. Statistical Shape Modelling and Markov Random Field Restoration (invited tutorial and exercise)

    DEFF Research Database (Denmark)

    Hilger, Klaus Baggesen

    This tutorial focuses on statistical shape analysis using point distribution models (PDM) which is widely used in modelling biological shape variability over a set of annotated training data. Furthermore, Active Shape Models (ASM) and Active Appearance Models (AAM) are based on PDMs and have proven...... deformation field between shapes. The tutorial demonstrates both generative active shape and appearance models, and MRF restoration on 3D polygonized surfaces. ''Exercise: Spectral-Spatial classification of multivariate images'' From annotated training data this exercise applies spatial image restoration...... using Markov random field relaxation of a spectral classifier. Keywords: the Ising model, the Potts model, stochastic sampling, discriminant analysis, expectation maximization....

  15. Modeling Self-Occlusions/Disocclusions in Dynamic Shape and Appearance Tracking for Obtaining Precise Shape

    KAUST Repository

    Yang, Yanchao

    2013-05-01

    We present a method to determine the precise shape of a dynamic object from video. This problem is fundamental to computer vision, and has a number of applications, for example, 3D video/cinema post-production, activity recognition and augmented reality. Current tracking algorithms that determine precise shape can be roughly divided into two categories: 1) Global statistics partitioning methods, where the shape of the object is determined by discriminating global image statistics, and 2) Joint shape and appearance matching methods, where a template of the object from the previous frame is matched to the next image. The former is limited in cases of complex object appearance and cluttered background, where global statistics cannot distinguish between the object and background. The latter is able to cope with complex appearance and a cluttered background, but is limited in cases of camera viewpoint change and object articulation, which induce self-occlusions and self-disocclusions of the object of interest. The purpose of this thesis is to model self-occlusion/disocclusion phenomena in a joint shape and appearance tracking framework. We derive a non-linear dynamic model of the object shape and appearance taking into account occlusion phenomena, which is then used to infer self-occlusions/disocclusions, shape and appearance of the object in a variational optimization framework. To ensure robustness to other unmodeled phenomena that are present in real-video sequences, the Kalman filter is used for appearance updating. Experiments show that our method, which incorporates the modeling of self-occlusion/disocclusion, increases the accuracy of shape estimation in situations of viewpoint change and articulation, and out-performs current state-of-the-art methods for shape tracking.

  16. Facial Expression Biometrics Using Statistical Shape Models

    Science.gov (United States)

    Quan, Wei; Matuszewski, Bogdan J.; Shark, Lik-Kwan; Ait-Boudaoud, Djamel

    2009-12-01

    This paper describes a novel method for representing different facial expressions based on the shape space vector (SSV) of the statistical shape model (SSM) built from 3D facial data. The method relies only on the 3D shape, with texture information not being used in any part of the algorithm, that makes it inherently invariant to changes in the background, illumination, and to some extent viewing angle variations. To evaluate the proposed method, two comprehensive 3D facial data sets have been used for the testing. The experimental results show that the SSV not only controls the shape variations but also captures the expressive characteristic of the faces and can be used as a significant feature for facial expression recognition. Finally the paper suggests improvements of the SSV discriminatory characteristics by using 3D facial sequences rather than 3D stills.

  17. Facial Expression Biometrics Using Statistical Shape Models

    Directory of Open Access Journals (Sweden)

    Djamel Ait-Boudaoud

    2009-01-01

    Full Text Available This paper describes a novel method for representing different facial expressions based on the shape space vector (SSV of the statistical shape model (SSM built from 3D facial data. The method relies only on the 3D shape, with texture information not being used in any part of the algorithm, that makes it inherently invariant to changes in the background, illumination, and to some extent viewing angle variations. To evaluate the proposed method, two comprehensive 3D facial data sets have been used for the testing. The experimental results show that the SSV not only controls the shape variations but also captures the expressive characteristic of the faces and can be used as a significant feature for facial expression recognition. Finally the paper suggests improvements of the SSV discriminatory characteristics by using 3D facial sequences rather than 3D stills.

  18. Phenomenological modeling of ferromagnetic shape memory alloys

    Science.gov (United States)

    Kiefer, Bjorn; Lagoudas, Dimitris C.

    2004-07-01

    A thermodynamically consistent phenomenological model is presented which captures the ferromagnetic shape memory effect, i. e. the large macroscopically observable shape change of magnetic shape memory materials under the application of external magnetic fields. In its most general form the model includes the influence of the microstructure for both the volume fraction of different martensitic variants and magnetic domains on the described macroscopic constitutive behavior. A phase diagram based approach is taken to postulate functions governing the onset and termination of the reorientation process. A numerical example is given for an experiment on a NiMnGa single crystal specimen reported in the literature, for which the model is reduced to a two-dimensional case of an assumed magnetic domain structure.

  19. Statistical Shape Modeling of Cam Femoroacetabular Impingement

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Michael D.; Dater, Manasi; Whitaker, Ross; Jurrus, Elizabeth R.; Peters, Christopher L.; Anderson, Andrew E.

    2013-10-01

    In this study, statistical shape modeling (SSM) was used to quantify three-dimensional (3D) variation and morphologic differences between femurs with and without cam femoroacetabular impingement (FAI). 3D surfaces were generated from CT scans of femurs from 41 controls and 30 cam FAI patients. SSM correspondence particles were optimally positioned on each surface using a gradient descent energy function. Mean shapes for control and patient groups were defined from the resulting particle configurations. Morphological differences between group mean shapes and between the control mean and individual patients were calculated. Principal component analysis was used to describe anatomical variation present in both groups. The first 6 modes (or principal components) captured statistically significant shape variations, which comprised 84% of cumulative variation among the femurs. Shape variation was greatest in femoral offset, greater trochanter height, and the head-neck junction. The mean cam femur shape protruded above the control mean by a maximum of 3.3 mm with sustained protrusions of 2.5-3.0 mm along the anterolateral head-neck junction and distally along the anterior neck, corresponding well with reported cam lesion locations and soft-tissue damage. This study provides initial evidence that SSM can describe variations in femoral morphology in both controls and cam FAI patients and may be useful for developing new measurements of pathological anatomy. SSM may also be applied to characterize cam FAI severity and provide templates to guide patient-specific surgical resection of bone.

  20. Artificial Neuron Modelling Based on Wave Shape

    Directory of Open Access Journals (Sweden)

    Kieran Greer

    2013-10-01

    Full Text Available This paper describes a new model for an artificial neural network processing unit or neuron. It is slightly different to a traditional feedforward network by the fact that it favours a mechanism of trying to match the wave-like ‘shape’ of the input with the shape of the output against specific value error corrections. The expectation is then that a best fit shape can be transposed into the desired output values more easily. This allows for notions of reinforcement through resonance and also the construction of synapses.

  1. A Model Coupling Method for Shape Prediction

    Institute of Scientific and Technical Information of China (English)

    WANG Dong-cheng; LIU Hong-min

    2012-01-01

    The shape of strip is calculated by iterative method which combines strip plastic deformation model with rolls elastic deformation model through their calculation results, which can be called results coupling method. Be- cause the shape and rolling force distribution are very sensitive to strip thickness transverse distribution% variation, the iterative course is rather unstable and sometimes convergence cannot be achieved. In addition, the calculating speed of results coupling method is low, which restricts its usable range. To solve the problem, a new model cou- pling method is developed, which takes the force distribution between rolls, rolling force distribution and strip's exit transverse displacement distribution as basic unknowns, and integrates strip plastic deformation model and rolls elas- tic deformation model as a unified linear equations through their internal relation, so the iterative calculation between the strip plastic deformation model and rolls elastic deformation model can be avoided. To prove the effectiveness of the model coupling method, two examples are calculated by results coupling method and model coupling method re- spectively. The results of front tension stress, back tension stress, strip~s exit gauge, the force between rolls and rolling force distribution calculated by model coupling method coincide very well with results coupling method. How- ever the calculation course of model coupling method is more steady than results coupling method, and its calculating speed is about ten times as much as the maximal speed of results coupling method, which validates its practicability and reliability.

  2. DEFICIENT INFORMATION MODELING OF MECHANICAL PRODUCTS FOR CONCEPTUAL SHAPE DESIGN

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In allusion to the deficient feature of product information in conceptual design, a framework of deficient information modeling for conceptual shape design is put forward, which includes qualitative shape modeling (a qualitative solid model), uncertain shape modeling (an uncertain relation model) and imprecise shape modeling (an imprecise region model). In the framework, the qualitative solid model is the core, which represents qualitatively (using symbols) the conceptual shapes of mechanical products. The uncertain relation model regarding domain relations as objects and the imprecise region model regarding domains as objects are used to deal with the uncertain and imprecise issues respectively, which arise from qualitative shape modeling or exist in product information itself.

  3. Analysis of trabecular bone architectural changes induced by osteoarthritis in rabbit femur using 3D active shape model and digital topology

    Science.gov (United States)

    Saha, P. K.; Rajapakse, C. S.; Williams, D. S.; Duong, L.; Coimbra, A.

    2007-03-01

    Osteoarthritis (OA) is the most common chronic joint disease, which causes the cartilage between the bone joints to wear away, leading to pain and stiffness. Currently, progression of OA is monitored by measuring joint space width using x-ray or cartilage volume using MRI. However, OA affects all periarticular tissues, including cartilage and bone. It has been shown previously that in animal models of OA, trabecular bone (TB) architecture is particularly affected. Furthermore, relative changes in architecture are dependent on the depth of the TB region with respect to the bone surface and main direction of load on the bone. The purpose of this study was to develop a new method for accurately evaluating 3D architectural changes induced by OA in TB. Determining the TB test domain that represents the same anatomic region across different animals is crucial for studying disease etiology, progression and response to therapy. It also represents a major technical challenge in analyzing architectural changes. Here, we solve this problem using a new active shape model (ASM)-based approach. A new and effective semi-automatic landmark selection approach has been developed for rabbit distal femur surface that can easily be adopted for many other anatomical regions. It has been observed that, on average, a trained operator can complete the user interaction part of landmark specification process in less than 15 minutes for each bone data set. Digital topological analysis and fuzzy distance transform derived parameters are used for quantifying TB architecture. The method has been applied on micro-CT data of excised rabbit femur joints from anterior cruciate ligament transected (ACLT) (n = 6) and sham (n = 9) operated groups collected at two and two-to-eight week post-surgery, respectively. An ASM of the rabbit right distal femur has been generated from the sham group micro-CT data. The results suggest that, in conjunction with ASM, digital topological parameters are suitable for

  4. Volume changes during active shape fluctuations in cells

    CERN Document Server

    Taloni, Alessandro; Salman, Oguz Umut; Truskinovsky, Lev; Zapperi, Stefano; La Porta, Caterina A M

    2015-01-01

    Cells modify their volume in response to changes in osmotic pressure but it is usually assumed that other active shape variations do not involve significant volume fluctuations. Here we report experiments demonstrating that water transport in and out of the cell is needed for the formation of blebs, commonly observed protrusions in the plasma membrane driven by cortex contraction. We develop and simulate a model of fluid mediated membrane-cortex deformations and show that a permeable membrane is necessary for bleb formation which is otherwise impaired. Taken together our experimental and theoretical results emphasize the subtle balance between hydrodynamics and elasticity in actively driven cell morphological changes.

  5. Multi-shape active composites by 3D printing of digital shape memory polymers

    OpenAIRE

    Jiangtao Wu; Chao Yuan; Zhen Ding; Michael Isakov; Yiqi Mao; Tiejun Wang; Martin L. Dunn; H. Jerry Qi

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of...

  6. Incorporating Prior Shape into Geometric Active Contours for Face Contour Detection

    Institute of Scientific and Technical Information of China (English)

    HUANGFuzhen; SUJianbo; XIYugeng

    2004-01-01

    In this paper a new method that incorporates prior shape information into geometric active contours for face contour detection is proposed. As in general a human face can be treated as an ellipse with a little shape variation, the prior face shape is represented as an elliptical curve. By combining the prior face shape with the powerful geometric active model proposed by Chan and Vese, the improved geometric active model can retain all the advantage of the Chan-Vese model and can detect face contours in images with complex backgrounds accurately even if the image is noisy. Moreover, by implementing the new model in a variational level set framework, automatic topological changes of the model can be achieved naturally and the transformation parameters that map the face boundary to the prior shape can be roughly estimated simultaneously. The experimental results show our procedure to be eiTicient.

  7. Embedding responses in spontaneous neural activity shaped through sequential learning.

    Directory of Open Access Journals (Sweden)

    Tomoki Kurikawa

    Full Text Available Recent experimental measurements have demonstrated that spontaneous neural activity in the absence of explicit external stimuli has remarkable spatiotemporal structure. This spontaneous activity has also been shown to play a key role in the response to external stimuli. To better understand this role, we proposed a viewpoint, "memories-as-bifurcations," that differs from the traditional "memories-as-attractors" viewpoint. Memory recall from the memories-as-bifurcations viewpoint occurs when the spontaneous neural activity is changed to an appropriate output activity upon application of an input, known as a bifurcation in dynamical systems theory, wherein the input modifies the flow structure of the neural dynamics. Learning, then, is a process that helps create neural dynamical systems such that a target output pattern is generated as an attractor upon a given input. Based on this novel viewpoint, we introduce in this paper an associative memory model with a sequential learning process. Using a simple hebbian-type learning, the model is able to memorize a large number of input/output mappings. The neural dynamics shaped through the learning exhibit different bifurcations to make the requested targets stable upon an increase in the input, and the neural activity in the absence of input shows chaotic dynamics with occasional approaches to the memorized target patterns. These results suggest that these dynamics facilitate the bifurcations to each target attractor upon application of the corresponding input, which thus increases the capacity for learning. This theoretical finding about the behavior of the spontaneous neural activity is consistent with recent experimental observations in which the neural activity without stimuli wanders among patterns evoked by previously applied signals. In addition, the neural networks shaped by learning properly reflect the correlations of input and target-output patterns in a similar manner to those designed in

  8. Digital Modeling and Shaping of Design Practices

    DEFF Research Database (Denmark)

    Reijonen, Satu

    coordination between the two communities but also shapes coordinative practices around the emerging building. The paper draws on two interlinked strands of literature that have engaged in the role of material artefacts in the social: the entanglement of technology in organizing and management (Orlikowski 2000...... of this study suggest that generative potential of digital modeling tools such as the calculation programme resides in their ability to restrictively define the possible roles in, focus of and sequence of working. In addition, digital modeling provides a separate medium with the help of which the design object...... may be re-enacted and restructured over and over again. In the case at hand, this enabled a ‘trial and error’ type of intervention practice by energy engineers....

  9. Joint modeling of cell and nuclear shape variation.

    Science.gov (United States)

    Johnson, Gregory R; Buck, Taraz E; Sullivan, Devin P; Rohde, Gustavo K; Murphy, Robert F

    2015-11-01

    Modeling cell shape variation is critical to our understanding of cell biology. Previous work has demonstrated the utility of nonrigid image registration methods for the construction of nonparametric nuclear shape models in which pairwise deformation distances are measured between all shapes and are embedded into a low-dimensional shape space. Using these methods, we explore the relationship between cell shape and nuclear shape. We find that these are frequently dependent on each other and use this as the motivation for the development of combined cell and nuclear shape space models, extending nonparametric cell representations to multiple-component three-dimensional cellular shapes and identifying modes of joint shape variation. We learn a first-order dynamics model to predict cell and nuclear shapes, given shapes at a previous time point. We use this to determine the effects of endogenous protein tags or drugs on the shape dynamics of cell lines and show that tagged C1QBP reduces the correlation between cell and nuclear shape. To reduce the computational cost of learning these models, we demonstrate the ability to reconstruct shape spaces using a fraction of computed pairwise distances. The open-source tools provide a powerful basis for future studies of the molecular basis of cell organization. PMID:26354424

  10. Shape regulation generates elastic interaction between active force dipoles

    CERN Document Server

    Golkov, Roman

    2016-01-01

    The organization of live cells to tissues is associated with the mechanical interaction between cells, which is mediated through their mechanical environment. We model live cells as spherical active force dipoles surrounded by an infinite elastic matrix, and analytically evaluate their elastic interaction energy for different scenarios of their regulatory behavior. For purely dilational eigenstrains the elastic interaction energy between any two bodies vanishes. We identify mechanical interactions between active cells applying non isotropic displacements with a regulation mechanism designed so that they will preserve their spherical shape. We express the resultant non-isotropic deformation field by a multipole expansion in terms of spherical harmonics. Mechanical self-regulation of live cells is not fully understood, and we compare homeostatic (set point) force applied by the cells on their environment versus homeostatic displacements on their surface. By including or excluding the first term of the expansion...

  11. Probabilistic contour extraction based on shape prior model

    Institute of Scientific and Technical Information of China (English)

    FAN Xin; LIANG De-qun

    2005-01-01

    Statistical shape prior model is employed to construct the dynamics in probabilistic contour estimation.By applying principal component analysis,plausible shape samples are efficiently generated to predict contour samples.Based on the shape-dependent dynamics and probabilistic image model,a particle filter is used to estimate the contour with a specific shape.Compared with the deterministic approach with shape information,the proposed method is simple yet more effective in extracting contours from images with shape variations and occlusion.

  12. Shape prior modeling using sparse representation and online dictionary learning.

    Science.gov (United States)

    Zhang, Shaoting; Zhan, Yiqiang; Zhou, Yan; Uzunbas, Mustafa; Metaxas, Dimitris N

    2012-01-01

    The recently proposed sparse shape composition (SSC) opens a new avenue for shape prior modeling. Instead of assuming any parametric model of shape statistics, SSC incorporates shape priors on-the-fly by approximating a shape instance (usually derived from appearance cues) by a sparse combination of shapes in a training repository. Theoretically, one can increase the modeling capability of SSC by including as many training shapes in the repository. However, this strategy confronts two limitations in practice. First, since SSC involves an iterative sparse optimization at run-time, the more shape instances contained in the repository, the less run-time efficiency SSC has. Therefore, a compact and informative shape dictionary is preferred to a large shape repository. Second, in medical imaging applications, training shapes seldom come in one batch. It is very time consuming and sometimes infeasible to reconstruct the shape dictionary every time new training shapes appear. In this paper, we propose an online learning method to address these two limitations. Our method starts from constructing an initial shape dictionary using the K-SVD algorithm. When new training shapes come, instead of re-constructing the dictionary from the ground up, we update the existing one using a block-coordinates descent approach. Using the dynamically updated dictionary, sparse shape composition can be gracefully scaled up to model shape priors from a large number of training shapes without sacrificing run-time efficiency. Our method is validated on lung localization in X-Ray and cardiac segmentation in MRI time series. Compared to the original SSC, it shows comparable performance while being significantly more efficient. PMID:23286160

  13. Weed Identification Using An Automated Active Shape Matching (AASM) Technique

    DEFF Research Database (Denmark)

    Swain, K C; Nørremark, Michael; Jørgensen, R N;

    2011-01-01

    on the concept of ‘active shape modelling’ to identify weed and crop plants based on their morphology. The automated active shape matching system (AASM) technique consisted of, i) a Pixelink camera ii) an LTI (Lehrstuhlfuer technische informatik) image processing library, iii) a laptop pc with the Linux OS. A 2......-identification process required 0.062 s for eight iterations with the Linux platform used....

  14. Weed identification using an automated active shape matching (AASM) technique

    OpenAIRE

    Swain, Kishore; Nørremark, Michael; Jørgensen, Rasmus N.; Midtiby, Henrik S.; Green, Ole

    2011-01-01

    Weed identification and control is a challenge for intercultural operations in agriculture. As an alternative to chemical pest control, a smart weed identification technique followed by mechanical weed control system could be developed. The proposed smart identification technique works on the concept of ‘active shape modelling’ to identify weed and crop plants based on their morphology. The automated active shape matching system (AASM) technique consisted of, i) a Pixelink camera ii) an LTI L...

  15. A probabilistic model for component-based shape synthesis

    KAUST Repository

    Kalogerakis, Evangelos

    2012-07-01

    We present an approach to synthesizing shapes from complex domains, by identifying new plausible combinations of components from existing shapes. Our primary contribution is a new generative model of component-based shape structure. The model represents probabilistic relationships between properties of shape components, and relates them to learned underlying causes of structural variability within the domain. These causes are treated as latent variables, leading to a compact representation that can be effectively learned without supervision from a set of compatibly segmented shapes. We evaluate the model on a number of shape datasets with complex structural variability and demonstrate its application to amplification of shape databases and to interactive shape synthesis. © 2012 ACM 0730-0301/2012/08-ART55.

  16. Learning shapes spontaneous activity itinerating over memorized states.

    Directory of Open Access Journals (Sweden)

    Tomoki Kurikawa

    Full Text Available Learning is a process that helps create neural dynamical systems so that an appropriate output pattern is generated for a given input. Often, such a memory is considered to be included in one of the attractors in neural dynamical systems, depending on the initial neural state specified by an input. Neither neural activities observed in the absence of inputs nor changes caused in the neural activity when an input is provided were studied extensively in the past. However, recent experimental studies have reported existence of structured spontaneous neural activity and its changes when an input is provided. With this background, we propose that memory recall occurs when the spontaneous neural activity changes to an appropriate output activity upon the application of an input, and this phenomenon is known as bifurcation in the dynamical systems theory. We introduce a reinforcement-learning-based layered neural network model with two synaptic time scales; in this network, I/O relations are successively memorized when the difference between the time scales is appropriate. After the learning process is complete, the neural dynamics are shaped so that it changes appropriately with each input. As the number of memorized patterns is increased, the generated spontaneous neural activity after learning shows itineration over the previously learned output patterns. This theoretical finding also shows remarkable agreement with recent experimental reports, where spontaneous neural activity in the visual cortex without stimuli itinerate over evoked patterns by previously applied signals. Our results suggest that itinerant spontaneous activity can be a natural outcome of successive learning of several patterns, and it facilitates bifurcation of the network when an input is provided.

  17. Persistent Homology Transform for Modeling Shapes and Surfaces

    OpenAIRE

    Turner, Katharine; Mukherjee, Sayan; Doug M Boyer

    2013-01-01

    In this paper we introduce a statistic, the persistent homology transform (PHT), to model surfaces in $\\mathbb{R}^3$ and shapes in $\\mathbb{R}^2$. This statistic is a collection of persistence diagrams - multiscale topological summaries used extensively in topological data analysis. We use the PHT to represent shapes and execute operations such as computing distances between shapes or classifying shapes. We prove the map from the space of simplicial complexes in $\\mathbb{R}^3$ into the space ...

  18. AC Electric Field Activated Shape Memory Polymer Composite

    Science.gov (United States)

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  19. Model Equations of Shape Memory Effect - Nitinol

    Directory of Open Access Journals (Sweden)

    Ion Vela

    2010-01-01

    Full Text Available Even it has been already confirmed that SMA’s have high potential for robotic actuators, actuators included in space robotics, underwater robotics, robotics for logistics, safety, as well as “green robotics” (robotics for the environment, energy conservation, sustainable development or agriculture, the number of applications of SMA-based actuators is still quite small, especially in applications in which their large strains, high specific work output and structural integration potential are useful,. The paper presents a formulated mathematical model calculated for binary SMA (Ni-Ti, helpful to estimate the stress distribution along with the transformation ratio of a SMA active element.

  20. Studying Doctoral Education: Using Activity Theory to Shape Methodological Tools

    Science.gov (United States)

    Beauchamp, Catherine; Jazvac-Martek, Marian; McAlpine, Lynn

    2009-01-01

    The study reported here, one part of a larger study on doctoral education, describes a pilot study that used Activity Theory to shape a methodological tool for better understanding the tensions inherent in the doctoral experience. As doctoral students may function within a range of activity systems, we designed data collection protocols based on…

  1. Confidence of model based shape reconstruction from sparse data

    DEFF Research Database (Denmark)

    Baka, N.; de Bruijne, M.; Reiber, J.H.C.;

    2010-01-01

    and assign a confidence value to the resulting reconstructed shape. An evaluation study is performed to compare three methods used for sparse SSM fitting w.r.t. specificity, generalization ability, and correctness of estimated confidence limits with an increasing amount of input information. We find...... that the proposed constrained shape model outperforms the other models, is robust against the selection and amount of sparse information, and indicates the shape confidence well....

  2. Modeling self-occlusions in dynamic shape and appearance tracking

    KAUST Repository

    Yang, Yanchao

    2013-12-01

    We present a method to track the precise shape of a dynamic object in video. Joint dynamic shape and appearance models, in which a template of the object is propagated to match the object shape and radiance in the next frame, are advantageous over methods employing global image statistics in cases of complex object radiance and cluttered background. In cases of complex 3D object motion and relative viewpoint change, self-occlusions and disocclusions of the object are prominent, and current methods employing joint shape and appearance models are unable to accurately adapt to new shape and appearance information, leading to inaccurate shape detection. In this work, we model self-occlusions and dis-occlusions in a joint shape and appearance tracking framework. Experiments on video exhibiting occlusion/dis-occlusion, complex radiance and background show that occlusion/dis-occlusion modeling leads to superior shape accuracy compared to recent methods employing joint shape/appearance models or employing global statistics. © 2013 IEEE.

  3. Mathematical and computer modeling of component surface shaping

    Science.gov (United States)

    Lyashkov, A.

    2016-04-01

    The process of shaping technical surfaces is an interaction of a tool (a shape element) and a component (a formable element or a workpiece) in their relative movements. It was established that the main objects of formation are: 1) a discriminant of a surfaces family, formed by the movement of the shape element relatively the workpiece; 2) an enveloping model of the real component surface obtained after machining, including transition curves and undercut lines; 3) The model of cut-off layers obtained in the process of shaping. When modeling shaping objects there are a lot of insufficiently solved or unsolved issues that make up a single scientific problem - a problem of qualitative shaping of the surface of the tool and then the component surface produced by this tool. The improvement of known metal-cutting tools, intensive development of systems of their computer-aided design requires further improvement of the methods of shaping the mating surfaces. In this regard, an important role is played by the study of the processes of shaping of technical surfaces with the use of the positive aspects of analytical and numerical mathematical methods and techniques associated with the use of mathematical and computer modeling. The author of the paper has posed and has solved the problem of development of mathematical, geometric and algorithmic support of computer-aided design of cutting tools based on computer simulation of the shaping process of surfaces.

  4. Tensegrity Models and Shape Control of Vehicle Formations

    CERN Document Server

    Nabet, Benjamin

    2009-01-01

    Using dynamic models of tensegrity structures, we derive provable, distributed control laws for stabilizing and changing the shape of a formation of vehicles in the plane. Tensegrity models define the desired, controlled, multi-vehicle system dynamics, where each node in the tensegrity structure maps to a vehicle and each interconnecting strut or cable in the structure maps to a virtual interconnection between vehicles. Our method provides a smooth map from any desired planar formation shape to a planar tensegrity structure. The stabilizing vehicle formation shape control laws are then given by the forces between nodes in the corresponding tensegrity model. The smooth map makes possible provably well behaved changes of formation shape over a prescribed time interval. A designed path in shape space is mapped to a path in the parametrized space of tensegrity structures and the vehicle formation tracks this path with forces derived from the time-varying tensegrity model. By means of examples, we illustrate the i...

  5. Asteroid Shape and Spin Axis Modeling Via Light Curve Inversion

    Science.gov (United States)

    Friz, Paul; Gokhale, V.

    2013-01-01

    We present light curves and shape and spin axis models for the five asteroids: 291 Alice, 281 Lucretia, 321 Florentina, 714 Ulula, and 3169 Ostro. These models were obtained using data taken from the Truman Observatory, the Asteroid Photometric Catalogue, and the Minor Planet Center. Knowledge of individual asteroids shapes and spin axes is vital to understanding the solar system. However, currently only 213 out of the 500,000 asteroids with known orbits have been modeled. By taking many light curves of asteroids over several apparitions it is possible to determine their shapes and spin axes by a process known as light curve inversion.

  6. Coupled Shape Model Segmentation in Pig Carcasses

    DEFF Research Database (Denmark)

    Hansen, Mads Fogtmann; Larsen, Rasmus; Ersbøll, Bjarne Kjær;

    2006-01-01

    In this paper we are concerned with multi-object segmentation. For each object we will train a level set function based shape prior from a sample set of outlines. The outlines are aligned in a multi-resolution scheme wrt. an Euclidean similarity transformation in order to maximize the overlap...... levels inside the outline as well as in a narrow band outside the outline. The maximum a posteriori estimate of the outline is found by gradient descent optimization. In order to segment a group of mutually dependent objects we propose 2 procedures, 1) the objects are found sequentially by conditioning...... the initialization of the next search from already found objects; 2) all objects are found simultaneously and a repelling force is introduced in order to avoid overlap between outlines in the solution. The methods are applied to segmentation of cross sections of muscles in slices of CT scans of pig backs for quality...

  7. Shape 4.0: 3D Shape Modeling and Processing Using Semantics.

    Science.gov (United States)

    Spagnuolo, Michela

    2016-01-01

    In the last decade, sensor, communication, and computing technologies have advanced rapidly, producing dramatic changes in our daily lives and in a variety of application domains. Emerging technologies are leading us to a gradual, but inescapable integration of our material and digital realities and the advent of cyber-physical worlds. Although attaining visual realism is within the grasp of current 3D modeling approaches, it is less clear whether current modeling techniques will accommodate the needs of human communication and of the applications that we can already envisage in those futuristic worlds. Inspired by the evolution trends of the Web, this article describes the evolution of shape modeling from the Shape 1.0 geometry-only, mesh-based stage to the forthcoming semantics-driven Shape 4.0 era. PMID:26780764

  8. Agricultural activity shapes the communication and migration patterns in Senegal.

    Science.gov (United States)

    Martin-Gutierrez, S; Borondo, J; Morales, A J; Losada, J C; Tarquis, A M; Benito, R M

    2016-06-01

    The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country. PMID:27368795

  9. Agricultural activity shapes the communication and migration patterns in Senegal

    Science.gov (United States)

    Martin-Gutierrez, S.; Borondo, J.; Morales, A. J.; Losada, J. C.; Tarquis, A. M.; Benito, R. M.

    2016-06-01

    The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country.

  10. An overview of constitutive models for shape memory alloys

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available The remarkable properties of shape memory alloys have facilitated their applications in many areas of technology. The purpose of this paper is to present an overview of thermomechanical behavior of these alloys, discussing the main constitutive models for their mathematical description. Metallurgical features and engineering applications are addressed as an introduction. Afterwards, five phenomenological theories are presented. In general, these models capture the general thermomechanical behavior of shape memory alloys, characterized by pseudoelasticity, shape memory effect, phase transformation phenomenon due to temperature variation, and internal subloops due to incomplete phase transformations.

  11. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bo; LIU YanJu; LENG JinSong; ZOU GuangPing

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations de-scribing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA).The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper.The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect.Shape memory factor is redefined in order to make clear its physical meaning.A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test.It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA.A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy.It is expanded from one-dimension to three-dimension with assuming SMA as iso-tropic material.All material constants in the new constitutive equation can be determined from mac-roscopic experiments,which makes it more easily used in practical applications.

  12. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations describing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA). The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper. The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect. Shape memory factor is redefined in order to make clear its physical meaning. A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test. It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA. A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy. It is expanded from one-dimension to three-dimension with assuming SMA as isotropic material. All material constants in the new constitutive equation can be determined from macroscopic experiments, which makes it more easily used in practical applications.

  13. Statistical shape model-based segmentation of brain MRI images.

    Science.gov (United States)

    Bailleul, Jonathan; Ruan, Su; Constans, Jean-Marc

    2007-01-01

    We propose a segmentation method that automatically delineates structures contours from 3D brain MRI images using a statistical shape model. We automatically build this 3D Point Distribution Model (PDM) in applying a Minimum Description Length (MDL) annotation to a training set of shapes, obtained by registration of a 3D anatomical atlas over a set of patients brain MRIs. Delineation of any structure from a new MRI image is first initialized by such registration. Then, delineation is achieved in iterating two consecutive steps until the 3D contour reaches idempotence. The first step consists in applying an intensity model to the latest shape position so as to formulate a closer guess: our model requires far less priors than standard model in aiming at direct interpretation rather than compliance to learned contexts. The second step consists in enforcing shape constraints onto previous guess so as to remove all bias induced by artifacts or low contrast on current MRI. For this, we infer the closest shape instance from the PDM shape space using a new estimation method which accuracy is significantly improved by a huge increase in the model resolution and by a depth-search in the parameter space. The delineation results we obtained are very encouraging and show the interest of the proposed framework. PMID:18003193

  14. Adding Curvature to Minimum Description Length Shape Models

    DEFF Research Database (Denmark)

    Thodberg, Hans Henrik; Ólafsdóttir, Hildur

    2003-01-01

    problem: How to select points on shapes defined as curves so that the points correspond across a data set. However, this MDL approach does not capture important shape characteristics related to the curvature of the curves, and occasionally it places marks in obvious conflict with the human notion of point...... correspondence. This paper shows how the MDL approach can be fine-tuned by adding a term to the cost function expressing the mismatch of curvature features across the data set. The method is illustrated on silhouettes of adult heads. The MDL method is able to solve the point correspondence problem......The Minimum Description Length (MDL) approach to shape modelling seeks a compact description of a set of shapes in terms of the coordinates of marks on the shapes. It has been shown that the mark positions resulting from this optimisation to a large extent solve the so-called point correspondence...

  15. A Faceted Shape Model Approach to Altimetry and Velocimetry for Irregularly Shaped Bodies

    Science.gov (United States)

    Bayard, D.S.; Brugarolas, P.B.; Broschart, S.B.

    2008-01-01

    Range and velocity sensors based on lidar or radar with multiple beams are often used to measure the altitude and velocity, respectively, of a spacecraft above a targetbody. A difficulty that arises when navigating about small bodies such as asteroids or comets, is that the notion of altitude is largely obscured by the irregular shape of the target surface. This paper develops a method to incorporate the multibeam altimeter and Doppler velocimeter measurements into the on-board spacecraft state estimator by using information from a faceted shape model representation of the target body surface.

  16. Modeling of T-Shaped Microcantilever Resonators

    CERN Document Server

    Narducci, M; Gracia, I; Fonseca, L; Santander, J; Cané, C

    2008-01-01

    The extensive research and development of micromechanical resonators is trying to allow the use of these devices for highly sensitive applications. Microcantilevers are some of the simplest MEMS structure and had been proved to be a good platform due to its excellent mechanical properties. A cantilever working in dynamic mode, adjust its resonance frequency depending on changes in both the spring constant (k) and mass (m) of the resonator. The aim of this work was to model a cantilever structure to determine the optimal dimensions in which the resonance frequency would be a function dominated by mass changes and not stiffness changes. In order to validate the model a set of microcantilevers were fabricated and characterized.

  17. Active contour-based visual tracking by integrating colors, shapes, and motions.

    Science.gov (United States)

    Hu, Weiming; Zhou, Xue; Li, Wei; Luo, Wenhan; Zhang, Xiaoqin; Maybank, Stephen

    2013-05-01

    In this paper, we present a framework for active contour-based visual tracking using level sets. The main components of our framework include contour-based tracking initialization, color-based contour evolution, adaptive shape-based contour evolution for non-periodic motions, dynamic shape-based contour evolution for periodic motions, and the handling of abrupt motions. For the initialization of contour-based tracking, we develop an optical flow-based algorithm for automatically initializing contours at the first frame. For the color-based contour evolution, Markov random field theory is used to measure correlations between values of neighboring pixels for posterior probability estimation. For adaptive shape-based contour evolution, the global shape information and the local color information are combined to hierarchically evolve the contour, and a flexible shape updating model is constructed. For the dynamic shape-based contour evolution, a shape mode transition matrix is learnt to characterize the temporal correlations of object shapes. For the handling of abrupt motions, particle swarm optimization is adopted to capture the global motion which is applied to the contour in the current frame to produce an initial contour in the next frame. PMID:23288333

  18. Support-shape Dependent Catalytic Activity in Pt/alumina Systems Using USANS/SANS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Hoon; Han, Sugyeong; Ha, Heonphil; Byun, Jiyoung; Kim, Man-ho [KIST, Seoul (Korea, Republic of)

    2015-10-15

    Pt nanoparticles dispersed on ceramic powder such as alumina and ceria powder are used as catalyst materials to reduce pollution from automobile exhaust, power plant exhaust, etc. Much effort has been put to investigate the relationship between types of catalyst support materials and reactivity of the supported metallic particles. The surface shape of support materials can also be expected to control the catalysts size with the surface shape of support materials. In this presentation, we show our SANS (small angle neutron scattering) -USANS (ultra small angle neutron scattering) analysis on the structural differences of different shapes of the same γ alumina powder with different loadings of Pt nanoparticles. Then, the reactivity of the prepared catalyst materials are presented and discussed based on the investigation of the structure of the support materials by SANS. The shapes of gamma alumina, rod-like or plate-like shape, were determined from nanometer to micrometer with USANS and SANS analysis. We found that the platelet-like alumina consists of an aggregate of 2 - 3 layers, which further reduce specific surface area and catalytic activity compared to rod-like shape. Rod-like shape shows more than 100% enhancement in the catalytic activities in model three-way-catalyst (TWC) reactions of CO, NO, and C{sub 3}H{sub 6} at low temperature around 200 .deg. C.

  19. Modeling of the Shape Forming of Composite Roll

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A shape modeling of spray formed composite roll, which is utilized to predict the shape and dimension of roll during spray forming process, is developed in this paper. The influences of the principal spray forming parameters, suich as the spatial distribution of melt mass flux, spray distance, rotating and translating speeds of substrate bar etc., on the geometry and dimension of spray formed product were investigated.

  20. Modelling the shape hierarchy for visually guided grasping

    Directory of Open Access Journals (Sweden)

    Omid eRezai

    2014-10-01

    Full Text Available The monkey anterior intraparietal area (AIP encodes visual information about three-dimensional object shape that is used to shape the hand for grasping. We modelled shape tuning in visual AIP neurons and its relationship with curvature and gradient information from the caudal intraparietal area (CIP. The main goal was to gain insight into the kinds of shape parameterizations that can account for AIP tuning and that are consistent with both the inputs to AIP and the role of AIP in grasping. We first experimented with superquadric shape parameters. We considered superquadrics because they occupy a role in robotics that is similar to AIP, in that superquadric fits are derived from visual input and used for grasp planning. We also experimented with an alternative shape parameterization that was based on an Isomap dimension reduction of spatial derivatives of depth (i.e. distance from the observer to the object surface. We considered an Isomap-based model because its parameters lacked discontinuities between similar shapes. When we matched the dimension of the Isomap to the number of superquadric parameters, the superquadric model fit the AIP data somewhat more closely. However, higher-dimensional Isomaps provided excellent fits. Also, we found that the Isomap parameters could be approximated much more accurately than superquadric parameters by feedforward neural networks with CIP-like inputs. We conclude that Isomaps, or perhaps alternative dimension reductions of visual inputs to AIP, provide a promising model of AIP electrophysiology data. However (in contrast with superquadrics further work is needed to test whether such shape parameterizations actually provide an effective basis for grasp control.

  1. Liver recognition based on statistical shape model in CT images

    Science.gov (United States)

    Xiang, Dehui; Jiang, Xueqing; Shi, Fei; Zhu, Weifang; Chen, Xinjian

    2016-03-01

    In this paper, an automatic method is proposed to recognize the liver on clinical 3D CT images. The proposed method effectively use statistical shape model of the liver. Our approach consist of three main parts: (1) model training, in which shape variability is detected using principal component analysis from the manual annotation; (2) model localization, in which a fast Euclidean distance transformation based method is able to localize the liver in CT images; (3) liver recognition, the initial mesh is locally and iteratively adapted to the liver boundary, which is constrained with the trained shape model. We validate our algorithm on a dataset which consists of 20 3D CT images obtained from different patients. The average ARVD was 8.99%, the average ASSD was 2.69mm, the average RMSD was 4.92mm, the average MSD was 28.841mm, and the average MSD was 13.31%.

  2. Shape Modeling of a Concentric-tube Continuum Robot

    DEFF Research Database (Denmark)

    Bai, Shaoping; Xing, Charles Chuhao

    2012-01-01

    Concentric-tube continuum robots feature with simple and compact structures and have a great potential in medical applications. The paper is concerned with the shape modeling of a type of concentric-tube continuum robot built with a collection of super-elastic NiTiNol tubes. The mechanics...... is modeled on the basis of energy approach for both the in-plane and out-plane cases. The torsional influences on the shape of the concentric-tube robots are considered. An experimental device was build for the model validation. The results of simulation and experiments are included and analyzed....

  3. Multi-region Statistical Shape Model for Cochlear Implantation

    DEFF Research Database (Denmark)

    Romera, Jordi; Kjer, H. Martin; Piella, Gemma;

    2016-01-01

    Statistical shape models are commonly used to analyze the variability between similar anatomical structures and their use is established as a tool for analysis and segmentation of medical images. However, using a global model to capture the variability of complex structures is not enough to achie...

  4. Shape Modelling Using Markov Random Field Restoration of Point Correspondences

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Hilger, Klaus Baggesen

    2003-01-01

    A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized...

  5. Thermoelectric control of shape memory alloy microactuators: a thermal model

    Science.gov (United States)

    Abadie, J.; Chaillet, Nicolas; Lexcellent, Christian; Bourjault, Alain

    1999-06-01

    Microtechnologies and microsystems engineering use new active materials. These materials are interesting to realize microactuators and microsensors. In this category of materials, Shape Memory Alloys (SMA) are good candidates for microactuation. SMA wires, or thin plates, can be used as active material in microfingers. These microstructures are able to provide very important forces, but have low dynamic response, especially for cooling, in confined environment. The control of the SMA phase transformations, and then the mechanical power generation, is made by the temperature. The Joule effect is an easy and efficiency way to heat the SMA wires, but cooling is not so easy. The dynamic response of the actuator depends on cooling capabilities. The thermal convection and conduction are the traditional ways to cool the SMA, but have limitations for microsystems. We are looking for a reversible way of heating and cooling SMA microactuators, based on the thermoelectric effects. Using Peltier effect, a positive or a negative electrical courant is able to pump or produce heat, in the SMA actuator. A physical model based on thermal exchanges between a Nickel/Titanium (NiTi) SMA, and Bismuth/Telluride (Te3Bi2) thermoelectric material has been developed. For simulation, we use a numerical resolution of our model, with finite elements, which takes into account the Peltier effect, the Joule effect, the convection, the conduction and the phase transformation of the SMA. We have also developed the corresponding experimental system, with two thermoelectric junctions, where the SMA actuator is one of the element of each junction. In this paper, the physical model and its numerical resolution are given, the experimental system used to validate the model is described, and experimental results are shown.

  6. Active shape control of composite structures under thermal loading

    Science.gov (United States)

    Binette, P.; Dano, M.-L.; Gendron, G.

    2009-02-01

    Maintaining the shape of high-precision structures such as space antennas and optical mirrors is still a challenging issue for designers. These structures are subjected to varying temperature conditions which often introduce thermal distortions. The development of smart materials offers great potential to correct the shape and to minimize the surface error. In this study, shape control of a composite structure under thermal loading using piezocomposites is investigated. The composite structure is made of a foam core and two carbon-epoxy face sheets. Macro-fiber composite (MFC™) patches are bonded on one side of the structure. The structure is subjected to a through-the-thickness temperature gradient which induces thermal distortion, essentially in the form of bending. The objective is to apply electric potential to the MFC™ actuators such that the deflection can be minimized. Finite-element analyses are conducted using the commercial software ABAQUS. Experiments are performed to study thermally induced distortion, piezoelectric actuation, and compensation of thermal distortion using MFC™ actuators. Numerical and experimental results are compared. A control loop based on strain measurements is used to actively control the structure. The results show that MFC™ actuators can compensate thermal distortion at all times, and that this is an efficient methodology.

  7. Active shape control of composite structures under thermal loading

    International Nuclear Information System (INIS)

    Maintaining the shape of high-precision structures such as space antennas and optical mirrors is still a challenging issue for designers. These structures are subjected to varying temperature conditions which often introduce thermal distortions. The development of smart materials offers great potential to correct the shape and to minimize the surface error. In this study, shape control of a composite structure under thermal loading using piezocomposites is investigated. The composite structure is made of a foam core and two carbon–epoxy face sheets. Macro-fiber composite (MFC(TM)) patches are bonded on one side of the structure. The structure is subjected to a through-the-thickness temperature gradient which induces thermal distortion, essentially in the form of bending. The objective is to apply electric potential to the MFC(TM) actuators such that the deflection can be minimized. Finite-element analyses are conducted using the commercial software ABAQUS. Experiments are performed to study thermally induced distortion, piezoelectric actuation, and compensation of thermal distortion using MFC(TM) actuators. Numerical and experimental results are compared. A control loop based on strain measurements is used to actively control the structure. The results show that MFC(TM) actuators can compensate thermal distortion at all times, and that this is an efficient methodology

  8. A model for ferromagnetic shape memory thin film actuators

    Science.gov (United States)

    Lee, Kwok-Lun; Seelecke, Stefan

    2005-05-01

    The last decade has witnessed the discovery of materials combining shape memory behavior with ferromagnetic properties (FSMAs), see James & Wuttig1, James et al.2, Ullakko et al.3. These materials feature the so-called giant magnetostrain effect, which, in contrast to conventional magnetostriction is due motion of martensite twins. This effect has motivated the development of a new class of active materials transducers, which combine intrinsic sensing capabilities with superior actuation speed and improved efficiency when compared to conventional shape memory alloys. Currently, thin film technology is being developed intensively in order to pave the way for applications in micro- and nanotechnology. As an example, Kohl et al., recently proposed a novel actuation mechanism based on NiMnGa thin film technology, which makes use of both the ferromagnetic transition and the martensitic transformation allowing the realization of an almost perfect antagonism in a single component part. The implementation of the mechanism led to the award-winning development of an optical microscanner. Possible applications in nanotechnology arise, e.g., by combination of smart NiMnGa actuators with scanning probe technologies. The key aspect of Kohl's device is the fact that it employs electric heating for actuation, which requires a thermo-magneto-mechanical model for analysis. The research presented in this paper aims at the development of a model that simulates this particular material behavior. It is based on ideas originally developed for conventional shape memory alloy behavior, (Mueller & Achenbach, Achenbach, Seelecke, Seelecke & Mueller) and couples it with a simple expression for the nonlinear temperature- and position-dependent effective magnetic force. This early and strongly simplified version does not account for a full coupling between SMA behavior and ferromagnetism yet, and does not incorporate the hysteretic character of the magnetization phenomena either. It can however

  9. Politics and economics to shape international oil and gas activity

    International Nuclear Information System (INIS)

    This paper reports that political and economic events play unusually strong roles in shaping worldwide oil and gas activity levels this year. Developments in the former U.S.S.R. will be critical. As the now-independent republics adopt new economic systems, production and demand patterns will change, as will exports from what has been the world's leading oil producer. Changing conditions in the Middle East among members of the Organization of Petroleum Exporting countries also will affect the industry in the year following the brief Persian Gulf war. Unless worldwide demand surges unexpectedly, these substantial additions to supply will tend to weaken oil prices in 1992

  10. Research for the energy turnaround. Phase transitions actively shape. Contributions

    International Nuclear Information System (INIS)

    The Annual Conference 2014 of the Renewable Energy Research Association was held in Berlin on 6 and 7 November 2014. This book documents the contributions of the conference on research for the energy turnaround, phase transitions actively shape. After an introduction and two contributions to the political framework, the contributions to the economic phases of the energy transition, the phase of the current turn, the phases of social energy revolution, the stages of heat turnaround (Waermewende), and the stages of the mobility turn deal with the stages of development of the energy system. Finally, the Research Association Renewable Energy is briefly presented.

  11. Patch-Based Generative Shape Model and MDL Model Selection for Statistical Analysis of Archipelagos

    DEFF Research Database (Denmark)

    Ganz, Melanie; Nielsen, Mads; Brandt, Sami

    2010-01-01

    We propose a statistical generative shape model for archipelago-like structures. These kind of structures occur, for instance, in medical images, where our intention is to model the appearance and shapes of calcifications in x-ray radio graphs. The generative model is constructed by (1) learning...... a patch-based dictionary for possible shapes, (2) building up a time-homogeneous Markov model to model the neighbourhood correlations between the patches, and (3) automatic selection of the model complexity by the minimum description length principle. The generative shape model is proposed...... as a probability distribution of a binary image where the model is intended to facilitate sequential simulation. Our results show that a relatively simple model is able to generate structures visually similar to calcifications. Furthermore, we used the shape model as a shape prior in the statistical segmentation...

  12. Photometry and shape modeling of Mars crosser asteroid (1011 Laodamia

    Directory of Open Access Journals (Sweden)

    Apostolovska G.

    2014-01-01

    Full Text Available An analysis of photometric observations of Mars crosser asteroid 1011 Laodamia conducted at Bulgarian National Astronomical Observatory Rozhen over a twelve year interval (2002, 2003, 2004, 2006, 2007, 2008, 2011, 2012 and 2013 is made. Based on the obtained lightcurves the spin vector, sense of rotation, and preliminary shape model of (1011 Laodamia have been determined using the lightcurve inversion method. The aim of this investigation is to increase the set of asteroids with known spin and shape parameters and to contribute in improving the model in combination with other techniques and sparse data produced by photometric asteroid surveys such as Pan-STARRS or GAIA.

  13. FACIAL LANDMARKING LOCALIZATION FOR EMOTION RECOGNITION USING BAYESIAN SHAPE MODELS

    Directory of Open Access Journals (Sweden)

    Hernan F. Garcia

    2013-02-01

    Full Text Available This work presents a framework for emotion recognition, based in facial expression analysis using Bayesian Shape Models (BSM for facial landmarking localization. The Facial Action Coding System (FACS compliant facial feature tracking based on Bayesian Shape Model. The BSM estimate the parameters of the model with an implementation of the EM algorithm. We describe the characterization methodology from parametric model and evaluated the accuracy for feature detection and estimation of the parameters associated with facial expressions, analyzing its robustness in pose and local variations. Then, a methodology for emotion characterization is introduced to perform the recognition. The experimental results show that the proposed model can effectively detect the different facial expressions. Outperforming conventional approaches for emotion recognition obtaining high performance results in the estimation of emotion present in a determined subject. The model used and characterization methodology showed efficient to detect the emotion type in 95.6% of the cases.

  14. Effect of nodule shape for modeling of auxetic microporous polymers

    Directory of Open Access Journals (Sweden)

    Lim Teik-Cheng

    2015-01-01

    Full Text Available Previous models for describing auxetic microporous polymers adopt 2D rectangular blocks with fibril interconnections. In this paper, spherical nodes are used in order to approximate the granular nodule shape and for taking into consideration the 3D nature of the nodes. Assuming curvilinear motion of the nodes as a result of fibril rotation, a quantitative description of the Poisson’s ratio is given as a function of the nodule density packing factor. Comparison with the 3D rectangular model shows that the spherical model gives a more conservative description of the Poisson’s ratio although both models exhibit similar trend. Results reveal the significance of the assumed node shape for modeling the Poisson’s ratio of auxetic microporous polymers.

  15. Advection around ventilated U-shaped burrows: A model study

    Science.gov (United States)

    Brand, Andreas; Lewandowski, JöRg; Hamann, Enrico; Nützmann, Gunnar

    2013-05-01

    Advective transport in the porous matrix of sediments surrounding burrows formed by fauna such as Chironomus plumosus has been generally neglected. A positron emission tomography study recently revealed that the pumping activity of the midge larvae can indeed induce fluid flow in the sediment. We present a numerical model study which explores the conditions at which advective transport in the sediment becomes relevant. A 0.15 m deep U-shaped burrow with a diameter of 0.002 m within the sediment was represented in a 3-D domain. Fluid flow in the burrow was calculated using the Navier-Stokes equation for incompressible laminar flow in the burrow, and flow in the sediment was described by Darcy's law. Nonreactive and reactive transport scenarios were simulated considering diffusion and advection. The pumping activity of the model larva results in considerable advective flow in the sediment at reasonable high permeabilities with flow velocities of up to 7.0 × 10-6 m s-1 close to the larva for a permeability of 3 × 10-12 m2. At permeabilities below 7 × 10-13 m2 advection is negligible compared to diffusion. Reactive transport simulations using first-order kinetics for oxygen revealed that advective flux into the sediment downstream of the pumping larva enhances sedimentary uptake, while the advective flux into the burrow upstream of the larvae inhibits diffusive sedimentary uptake. Despite the fact that both effects cancel each other with respect to total solute uptake, the advection-induced asymmetry in concentration distribution can lead to a heterogeneous solute and redox distribution in the sediment relevant to complex reaction networks.

  16. Biomedical Applications of Thermally Activated Shape Memory Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Small IV, W; Singhal, P; Wilson, T S; Maitland, D J

    2009-04-10

    Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.

  17. Irregular Shaped Building Design Optimization with Building Information Modelling

    Directory of Open Access Journals (Sweden)

    Lee Xia Sheng

    2016-01-01

    Full Text Available This research is to recognise the function of Building Information Modelling (BIM in design optimization for irregular shaped buildings. The study focuses on a conceptual irregular shaped “twisted” building design similar to some existing sculpture-like architectures. Form and function are the two most important aspects of new buildings, which are becoming more sophisticated as parts of equally sophisticated “systems” that we are living in. Nowadays, it is common to have irregular shaped or sculpture-like buildings which are very different when compared to regular buildings. Construction industry stakeholders are facing stiff challenges in many aspects such as buildability, cost effectiveness, delivery time and facility management when dealing with irregular shaped building projects. Building Information Modelling (BIM is being utilized to enable architects, engineers and constructors to gain improved visualization for irregular shaped buildings; this has a purpose of identifying critical issues before initiating physical construction work. In this study, three variations of design options differing in rotating angle: 30 degrees, 60 degrees and 90 degrees are created to conduct quantifiable comparisons. Discussions are focused on three major aspects including structural planning, usable building space, and structural constructability. This research concludes that Building Information Modelling is instrumental in facilitating design optimization for irregular shaped building. In the process of comparing different design variations, instead of just giving “yes or no” type of response, stakeholders can now easily visualize, evaluate and decide to achieve the right balance based on their own criteria. Therefore, construction project stakeholders are empowered with superior evaluation and decision making capability.

  18. 3D Model Retrieval Based on Semantic and Shape Indexes

    CERN Document Server

    Kassimi, My Abdellah

    2011-01-01

    The size of 3D models used on the web or stored in databases is becoming increasingly high. Then, an efficient method that allows users to find similar 3D objects for a given 3D model query has become necessary. Keywords and the geometry of a 3D model cannot meet the needs of users' retrieval because they do not include the semantic information. In this paper, a new method has been proposed to 3D models retrieval using semantic concepts combined with shape indexes. To obtain these concepts, we use the machine learning methods to label 3D models by k-means algorithm in measures and shape indexes space. Moreover, semantic concepts have been organized and represented by ontology language OWL and spatial relationships are used to disambiguate among models of similar appearance. The SPARQL query language has been used to question the information displayed in this language and to compute the similarity between two 3D models. We interpret our results using the Princeton Shape Benchmark Database and the results show ...

  19. Using a Shape Model in the Design of Hearing Aids

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Nielsen, Claus; Laugesen, Søren;

    2004-01-01

    Today the design of custom completely-in-the-canal hearing aids is a manual process and therefore there is a variation in the quality of the finished hearing aids. Especially the placement of the so-called faceplate on the hearing aid strongly influences the size and shape of the hearing aid. Since...... the future hearing aid production will be less manual there is a need for algorithms that mimic the craftsmanship of skilled operators. In this paper it is described how a statistical shape model of the ear canal can be used to predict the placement of the faceplate on a hearing aid made for a given ear...

  20. Orthodontic applications of a superelastic shape-memory alloy model

    International Nuclear Information System (INIS)

    During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

  1. Shape coexistence in the microscopically guided interacting boson model

    CERN Document Server

    Nomura, K; Van Isacker, P

    2015-01-01

    Shape coexistence has been a subject of great interest in nuclear physics for many decades. In the context of the nuclear shell model, intruder excitations may give rise to remarkably low-lying excited $0^+$ states associated with different intrinsic shapes. In heavy open-shell nuclei, the dimension of the shell-model configuration space that includes such intruder excitations becomes exceedingly large, thus requiring a drastic truncation scheme. Such a framework has been provided by the interacting boson model (IBM). In this article we address the phenomenon of shape coexistence and its relevant spectroscopy from the point of view of the IBM. A special focus is placed on the method developed recently which makes use of the link between the IBM and the self-consistent mean-field approach based on the nuclear energy density functional. The method is extended to deal with various intruder configurations associated with different equilibrium shapes. We assess the predictive power of the method and suggest possib...

  2. First Principles Modelling of Shape Memory Alloys Molecular Dynamics Simulations

    CERN Document Server

    Kastner, Oliver

    2012-01-01

    Materials sciences relate the macroscopic properties of materials to their microscopic structure and postulate the need for holistic multiscale research. The investigation of shape memory alloys is a prime example in this regard. This particular class of materials exhibits strong coupling of temperature, strain and stress, determined by solid state phase transformations of their metallic lattices. The present book presents a collection of simulation studies of this behaviour. Employing conceptually simple but comprehensive models, the fundamental material properties of shape memory alloys are qualitatively explained from first principles. Using contemporary methods of molecular dynamics simulation experiments, it is shown how microscale dynamics may produce characteristic macroscopic material properties. The work is rooted in the materials sciences of shape memory alloys and  covers  thermodynamical, micro-mechanical  and crystallographical aspects. It addresses scientists in these research fields and thei...

  3. A macro-mechanical constitutive model for shape memory polymer

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    It is of theoretical and engineering interest to establish a macro-mechanical constitutive model of the shape memory polymer (SMP), which includes the mechanical constitutive equation and the material parameter function, from the viewpoint of practical application. In this paper, a new three-dimensional macro-mechanical constitutive equation, which describes the mechanical behaviors associated with the shape memory effect of SMP, is developed based on solid mechanics and the viscoelasticity theorem. According to the results of the DMA test, a new material parameter function is established to express the relationship of the material parameters and temperature during the glass transition of SMP. The new macro-mechanical constitutive equation and material parameter function are used to numerically simulate the process producing the shape memory effect of SMP, which includes deforming at high temperature, stress freezing, unloading at low temperature and shape recovery. They are also used to investigate and analyze the influences of loading rate and temperature change rate on the thermo-mechanical behaviors of SMP. The numerical results and the comparisons with Zhou’s material parameter function and Tobushi’s mechanical constitutive equation illustrate that the proposed three-dimensional macro-mechanical constitutive model can effectively predict the thermo-mechanical behaviors of SMP under the state of complex stress.

  4. Multi-region statistical shape model for cochlear implantation

    Science.gov (United States)

    Romera, Jordi; Kjer, H. Martin; Piella, Gemma; Ceresa, Mario; González Ballester, Miguel A.

    2016-03-01

    Statistical shape models are commonly used to analyze the variability between similar anatomical structures and their use is established as a tool for analysis and segmentation of medical images. However, using a global model to capture the variability of complex structures is not enough to achieve the best results. The complexity of a proper global model increases even more when the amount of data available is limited to a small number of datasets. Typically, the anatomical variability between structures is associated to the variability of their physiological regions. In this paper, a complete pipeline is proposed for building a multi-region statistical shape model to study the entire variability from locally identified physiological regions of the inner ear. The proposed model, which is based on an extension of the Point Distribution Model (PDM), is built for a training set of 17 high-resolution images (24.5 μm voxels) of the inner ear. The model is evaluated according to its generalization ability and specificity. The results are compared with the ones of a global model built directly using the standard PDM approach. The evaluation results suggest that better accuracy can be achieved using a regional modeling of the inner ear.

  5. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation.

    Directory of Open Access Journals (Sweden)

    J Farley Norman

    Full Text Available It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped "glaven" for 12 seconds and were required to indicate which of 12 (for bell peppers or 8 (for glavens simultaneously visible objects possessed the same shape. The initial single object's shape was defined either by boundary contours alone (i.e., presented as a silhouette, specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions-e.g., the participants' performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions. The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision.

  6. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation

    Science.gov (United States)

    Cheeseman, Jacob R.; Thomason, Kelsey E.; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B.; Lamirande, Davora

    2016-01-01

    It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped “glaven”) for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object’s shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions–e.g., the participants’ performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531

  7. Shaping tissues by balancing active forces and geometric constraints

    Science.gov (United States)

    Foolen, Jasper; Yamashita, Tadahiro; Kollmannsberger, Philip

    2016-02-01

    The self-organization of cells into complex tissues during growth and regeneration is a combination of physical-mechanical events and biochemical signal processing. Cells actively generate forces at all stages in this process, and according to the laws of mechanics, these forces result in stress fields defined by the geometric boundary conditions of the cell and tissue. The unique ability of cells to translate such force patterns into biochemical information and vice versa sets biological tissues apart from any other material. In this topical review, we summarize the current knowledge and open questions of how forces and geometry act together on scales from the single cell to tissues and organisms, and how their interaction determines biological shape and structure. Starting with a planar surface as the simplest type of geometric constraint, we review literature on how forces during cell spreading and adhesion together with geometric constraints impact cell shape, stress patterns, and the resulting biological response. We then move on to include cell-cell interactions and the role of forces in monolayers and in collective cell migration, and introduce curvature at the transition from flat cell sheets to three-dimensional (3D) tissues. Fibrous 3D environments, as cells experience them in the body, introduce new mechanical boundary conditions and change cell behaviour compared to flat surfaces. Starting from early work on force transmission and collagen remodelling, we discuss recent discoveries on the interaction with geometric constraints and the resulting structure formation and network organization in 3D. Recent literature on two physiological scenarios—embryonic development and bone—is reviewed to demonstrate the role of the force-geometry balance in living organisms. Furthermore, the role of mechanics in pathological scenarios such as cancer is discussed. We conclude by highlighting common physical principles guiding cell mechanics, tissue patterning and

  8. Shaping tissues by balancing active forces and geometric constraints

    International Nuclear Information System (INIS)

    The self-organization of cells into complex tissues during growth and regeneration is a combination of physical–mechanical events and biochemical signal processing. Cells actively generate forces at all stages in this process, and according to the laws of mechanics, these forces result in stress fields defined by the geometric boundary conditions of the cell and tissue. The unique ability of cells to translate such force patterns into biochemical information and vice versa sets biological tissues apart from any other material. In this topical review, we summarize the current knowledge and open questions of how forces and geometry act together on scales from the single cell to tissues and organisms, and how their interaction determines biological shape and structure. Starting with a planar surface as the simplest type of geometric constraint, we review literature on how forces during cell spreading and adhesion together with geometric constraints impact cell shape, stress patterns, and the resulting biological response. We then move on to include cell–cell interactions and the role of forces in monolayers and in collective cell migration, and introduce curvature at the transition from flat cell sheets to three-dimensional (3D) tissues. Fibrous 3D environments, as cells experience them in the body, introduce new mechanical boundary conditions and change cell behaviour compared to flat surfaces. Starting from early work on force transmission and collagen remodelling, we discuss recent discoveries on the interaction with geometric constraints and the resulting structure formation and network organization in 3D. Recent literature on two physiological scenarios—embryonic development and bone—is reviewed to demonstrate the role of the force-geometry balance in living organisms. Furthermore, the role of mechanics in pathological scenarios such as cancer is discussed. We conclude by highlighting common physical principles guiding cell mechanics, tissue patterning

  9. Modeling Permanent Deformations of Superelastic and Shape Memory Materials.

    Science.gov (United States)

    Urbano, Marco Fabrizio; Auricchio, Ferdinando

    2015-06-11

    In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement.

  10. Rock shape, restitution coefficients and rockfall trajectory modelling

    Science.gov (United States)

    Glover, James; Christen, Marc; Bühler, Yves; Bartelt, Perry

    2014-05-01

    Restitution coefficients are used in rockfall trajectory modelling to describe the ratio between incident and rebound velocities during ground impact. They are central to the problem of rockfall hazard analysis as they link rock mass characteristics to terrain properties. Using laboratory experiments as a guide, we first show that restitution coefficients exhibit a wide range of scatter, although the material properties of the rock and ground are constant. This leads us to the conclusion that restitution coefficients are poor descriptors of rock-ground interaction. The primary problem is that "apparent" restitution coefficients are applied at the rock's centre-of-mass and do not account for rock shape. An accurate description of the rock-ground interaction requires the contact forces to be applied at the rock surface with consideration of the momentary rock position and spin. This leads to a variety of rock motions including bouncing, sliding, skipping and rolling. Depending on the impact configuration a wide range of motions is possible. This explains the large scatter of apparent restitution coefficients. We present a rockfall model based on newly developed hard-contact algorithms which includes the effects of rock shape and therefore is able to reproduce the results of different impact configurations. We simulate the laboratory experiments to show that it is possible to reproduce run-out and dispersion of different rock shapes using parameters obtained from independent tests. Although this is a step forward in rockfall trajectory modelling, the problem of parametersing real terrain remains.

  11. Orthodontic applications of a superelastic shape-memory alloy model

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, R.W.; Enlow, R.L. [Otago Univ., Dunedin (New Zealand). Dept. of Math. and Stat.; Hood, J.A.A. [Dept. of Oral Sciences and Orthodontics, Univ. of Otago, Dunedin (New Zealand)

    2000-07-01

    During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

  12. SHADE: A Shape-Memory-Activated Device Promoting Ankle Dorsiflexion

    Science.gov (United States)

    Pittaccio, S.; Viscuso, S.; Rossini, M.; Magoni, L.; Pirovano, S.; Villa, E.; Besseghini, S.; Molteni, F.

    2009-08-01

    Acute post-stroke rehabilitation protocols include passive mobilization as a means to prevent contractures. A device (SHADE) that provides repetitive passive motion to a flaccid ankle by using shape memory alloy actuators could be of great help in providing this treatment. A suitable actuator was designed as a cartridge of approximately 150 × 20 × 15 mm, containing 2.5 m of 0.25 mm diameter NiTi wire. This actuator was activated by Joule’s effect employing a 7 s current input at 0.7 A, which provided 10 N through 76 mm displacement. Cooling and reset by natural convection took 30 s. A prototype of SHADE was assembled with two thermoplastic shells hinged together at the ankle and strapped on the shin and foot. Two actuators were fixed on the upper shell while an inextensible thread connected each NiTi wire to the foot shell. The passive ankle motion (passive range of motion, PROM) generated by SHADE was evaluated optoelectronically on three flaccid patients (58 ± 5 years old); acceptability was assessed by a questionnaire presented to further three flaccid patients (44 ± 11.5 years old) who used SHADE for 5 days, 30 min a day. SHADE was well accepted by all patients, produced good PROM, and caused no pain. The results prove that suitable limb mobilization can be produced by SMA actuators.

  13. Methods of artificial enlargement of the training set for statistical shape models.

    Science.gov (United States)

    Koikkalainen, Juha; Tölli, Tuomas; Lauerma, Kirsi; Antila, Kari; Mattila, Elina; Lilja, Mikko; Lötjönen, Jyrki

    2008-11-01

    Due to the small size of training sets, statistical shape models often over-constrain the deformation in medical image segmentation. Hence, artificial enlargement of the training set has been proposed as a solution for the problem to increase the flexibility of the models. In this paper, different methods were evaluated to artificially enlarge a training set. Furthermore, the objectives were to study the effects of the size of the training set, to estimate the optimal number of deformation modes, to study the effects of different error sources, and to compare different deformation methods. The study was performed for a cardiac shape model consisting of ventricles, atria, and epicardium, and built from magnetic resonance (MR) volume images of 25 subjects. Both shape modeling and image segmentation accuracies were studied. The objectives were reached by utilizing different training sets and datasets, and two deformation methods. The evaluation proved that artificial enlargement of the training set improves both the modeling and segmentation accuracy. All but one enlargement techniques gave statistically significantly (p < 0.05) better segmentation results than the standard method without enlargement. The two best enlargement techniques were the nonrigid movement technique and the technique that combines principal component analysis (PCA) and finite element model (FEM). The optimal number of deformation modes was found to be near 100 modes in our application. The active shape model segmentation gave better segmentation accuracy than the one based on the simulated annealing optimization of the model weights.

  14. Biologically Inspired Model for Inference of 3D Shape from Texture.

    Science.gov (United States)

    Gomez, Olman; Neumann, Heiko

    2016-01-01

    A biologically inspired model architecture for inferring 3D shape from texture is proposed. The model is hierarchically organized into modules roughly corresponding to visual cortical areas in the ventral stream. Initial orientation selective filtering decomposes the input into low-level orientation and spatial frequency representations. Grouping of spatially anisotropic orientation responses builds sketch-like representations of surface shape. Gradients in orientation fields and subsequent integration infers local surface geometry and globally consistent 3D depth. From the distributions in orientation responses summed in frequency, an estimate of the tilt and slant of the local surface can be obtained. The model suggests how 3D shape can be inferred from texture patterns and their image appearance in a hierarchically organized processing cascade along the cortical ventral stream. The proposed model integrates oriented texture gradient information that is encoded in distributed maps of orientation-frequency representations. The texture energy gradient information is defined by changes in the grouped summed normalized orientation-frequency response activity extracted from the textured object image. This activity is integrated by directed fields to generate a 3D shape representation of a complex object with depth ordering proportional to the fields output, with higher activity denoting larger distance in relative depth away from the viewer.

  15. Biologically Inspired Model for Inference of 3D Shape from Texture.

    Science.gov (United States)

    Gomez, Olman; Neumann, Heiko

    2016-01-01

    A biologically inspired model architecture for inferring 3D shape from texture is proposed. The model is hierarchically organized into modules roughly corresponding to visual cortical areas in the ventral stream. Initial orientation selective filtering decomposes the input into low-level orientation and spatial frequency representations. Grouping of spatially anisotropic orientation responses builds sketch-like representations of surface shape. Gradients in orientation fields and subsequent integration infers local surface geometry and globally consistent 3D depth. From the distributions in orientation responses summed in frequency, an estimate of the tilt and slant of the local surface can be obtained. The model suggests how 3D shape can be inferred from texture patterns and their image appearance in a hierarchically organized processing cascade along the cortical ventral stream. The proposed model integrates oriented texture gradient information that is encoded in distributed maps of orientation-frequency representations. The texture energy gradient information is defined by changes in the grouped summed normalized orientation-frequency response activity extracted from the textured object image. This activity is integrated by directed fields to generate a 3D shape representation of a complex object with depth ordering proportional to the fields output, with higher activity denoting larger distance in relative depth away from the viewer. PMID:27649387

  16. Hysteresis in Magnetic Shape Memory Composites: Modeling and Simulation

    CERN Document Server

    Conti, Sergio; Rumpf, Martin

    2015-01-01

    Magnetic shape memory alloys are characterized by the coupling between a structural phase transition and magnetic one. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the transformation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the phase boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimali...

  17. Vertebral classification using localized pathology-related shape model

    Science.gov (United States)

    Zewail, R.; Elsafi, A.; Durdle, N.

    2008-03-01

    Radiographs of the spine are frequently examined for assessment of vertebral abnormalities. Features like osteophytes (bony growth of vertebra's corners), and disc space narrowing are often used as visual evidence of osteoarthris or degenerative joint disease. These symptoms result in remarkable changes in the shapes of the vertebral body. Statistical analysis of anatomical structure has recently gained increased popularity within the medical imaging community, since they have the potential to enhance the automated diagnosis process. In this paper, we present a novel method for computer-assisted vertebral classification using a localized, pathology-related shape model. The new classification scheme is able to assess the condition of multiple vertebrae simultaneously, hence is possible to directly classify the whole spine anatomy according to the condition of interest (anterior osteophites). At the core of this method is a new localized shape model that uses concepts of sparsity, dimension reduction, and statistical independence to extract sets of localized modes of deformations specific to each of the vertebrae under investigation. By projection of the shapes onto any specific set of deformation modes (or basis), we obtain low-dimensional features that are most directly related to the pathology of the vertebra of interest. These features are then used as input to a support vector machine classifier to classify the vertebra under investigation as normal or upnormal. Experiments are conducted using contours from digital x-ray images of five vertebrae of lumbar spine. The accuracy of the classification scheme is assessed using the ROC curves. An average specifity of 96.8 % is achieved with a sensitivity of 80 %.

  18. Error Model and Compensation of Bell-Shaped Vibratory Gyro

    Directory of Open Access Journals (Sweden)

    Zhong Su

    2015-09-01

    Full Text Available A bell-shaped vibratory angular velocity gyro (BVG, inspired by the Chinese traditional bell, is a type of axisymmetric shell resonator gyroscope. This paper focuses on development of an error model and compensation of the BVG. A dynamic equation is firstly established, based on a study of the BVG working mechanism. This equation is then used to evaluate the relationship between the angular rate output signal and bell-shaped resonator character, analyze the influence of the main error sources and set up an error model for the BVG. The error sources are classified from the error propagation characteristics, and the compensation method is presented based on the error model. Finally, using the error model and compensation method, the BVG is calibrated experimentally including rough compensation, temperature and bias compensation, scale factor compensation and noise filter. The experimentally obtained bias instability is from 20.5°/h to 4.7°/h, the random walk is from 2.8°/h1/2 to 0.7°/h1/2 and the nonlinearity is from 0.2% to 0.03%. Based on the error compensation, it is shown that there is a good linear relationship between the sensing signal and the angular velocity, suggesting that the BVG is a good candidate for the field of low and medium rotational speed measurement.

  19. Mascon gravitation model using a shaped polyhedral source

    Science.gov (United States)

    Chanut, T. G. G.; Aljbaae, S.; Carruba, V.

    2015-07-01

    In the last two decades, new computational tools have been developed in order to aid space missions to orbit around irregular small bodies. One of the techniques consists in rebuilding their shape in tetrahedral polyhedron. This method is well suited to determine the shape and estimate certain physical features of asteroids. However, a large computational effort is necessary depending on the quantity of triangular faces chosen. Another method is based on a representation of the central body in terms of mascons (discrete spherical masses). The main advantage of the method is its simplicity which makes the calculation faster. Nevertheless, the errors are non-negligible when the attraction expressions are calculated near the surface of the body. In this work, we carry out a study to develop a new code that determines the centre of mass of each tetrahedron of a shaped polyhedral source and evaluates the gravitational potential function and its first- and second-order derivatives. We performed a series of tests and compared the results with the classical polyhedron method. We found good agreement between our determination of the attraction expressions close to the surface, and the same determination by the classical polyhedron method. However, this agreement does not occur inside the body. Our model appears to be more accurate in representing the potential very close to the body's surface when we divide the tetrahedron in three parts. Finally, we have found that in terms of CPU time requirements, the execution of our code is much faster compared with the polyhedron method.

  20. Hysteresis in magnetic shape memory composites: Modeling and simulation

    Science.gov (United States)

    Conti, Sergio; Lenz, Martin; Rumpf, Martin

    2016-04-01

    Magnetic shape memory alloys are characterized by the coupling between the reorientation of structural variants and the rearrangement of magnetic domains. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the reorientation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the twin boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimality condition. We illustrate and discuss the influence of the particle geometry (volume fraction, shape, arrangement) and the polymer elastic parameters on the observed hysteresis and compare with recent experimental results.

  1. Sparse decomposition and modeling of anatomical shape variation

    DEFF Research Database (Denmark)

    Sjöstrand, Karl; Rostrup, Egill; Ryberg, Charlotte;

    2007-01-01

    counterparts if constructed carefully. In most medical applications, models are required to have both good statistical performance and a relevant clinical interpretation to be of value. Morphometry of the corpus callosum is one illustrative example. This paper presents a method for relating spatial features to...... anatomical variation related to clinical outcome. In the present application, landmark-based shape data of the corpus callosum is analyzed in relation to age, gender, and clinical tests of walking speed and verbal fluency. To put the data-driven sparse principal component method into perspective, we consider...

  2. Sparse Decomposition and Modeling of Anatomical Shape Variation

    DEFF Research Database (Denmark)

    Sjöstrand, Karl; Rostrup, Egill; Ryberg, Charlotte;

    2007-01-01

    counterparts if constructed carefully. In most medical applications, models are required to have both good statistical performance and a relevant clinical interpretation to be of value. Morphometry of the corpus callosum is one illustrative example. This paper presents a method for relating spatial features to...... anatomical variation related to clinical outcome. In the present application, landmark-based shape data of the corpus callosum is analyzed in relation to age, gender, and clinical tests of walking speed and verbal fluency. To put the data-driven sparse principal component method into perspective, we consider...

  3. Genetic Fuzzy Modelling of User Perception of 3D Shapes

    DEFF Research Database (Denmark)

    Achiche, Sofiane; Ahmed-Kristensen, Saeema

    2011-01-01

    the emotion/perception with different shapes composed of a set of different geometric features. In this paper, the authors propose an automatic approach to formalize the relationships between geometric information of 3D objects and the intended emotional content using fuzzy logic. In addition......, the automatically generated fuzzy knowledge base was compared to the user’s perceptions and to the manually constructed fuzzy knowledge base. The initial findings indicate that the approach is indeed valid to formalize geometric information with perceptions and validate the author’s manually developed fuzzy models....

  4. A Preliminary Shape and Spin Axis Model for 595 Polyxena

    Science.gov (United States)

    Warner, Brian D.

    2008-10-01

    Photometric observations made at the Palmer Divide Observatory during the 2006 and 2008 apparitions of the main-belt asteroid 595 Polyxena were combined with dense lightcurves from 1993 included in the Uppsala Asteroid Photometric Catalog and a sparse lightcurve based on data from the USNO to determine a preliminary shape and spin axis model. Two solutions dominated the result set, one prograde (? = 42°, ß = 8°) and one retrograde (? = 222°, ß = -4°). The uncertainty in each coordinate is ± 5°. The sidereal period was found to be 11.794162 ± 0.000023 h.

  5. MHD modeling of dense plasma focus electrode shape variation

    Science.gov (United States)

    McLean, Harry; Hartman, Charles; Schmidt, Andrea; Tang, Vincent; Link, Anthony; Ellsworth, Jen; Reisman, David

    2013-10-01

    The dense plasma focus (DPF) is a very simple device physically, but results to date indicate that very extensive physics is needed to understand the details of operation, especially during the final pinch where kinetic effects become very important. Nevertheless, the overall effects of electrode geometry, electrode size, and drive circuit parameters can be informed efficiently using MHD fluid codes, especially in the run-down phase before the final pinch. These kinds of results can then guide subsequent, more detailed fully kinetic modeling efforts. We report on resistive 2-d MHD modeling results applying the TRAC-II code to the DPF with an emphasis on varying anode and cathode shape. Drive circuit variations are handled in the code using a self-consistent circuit model for the external capacitor bank since the device impedance is strongly coupled to the internal plasma physics. Electrode shape is characterized by the ratio of inner diameter to outer diameter, length to diameter, and various parameterizations for tapering. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  6. Modeling variance structure of body shape traits of Lipizzan horses.

    Science.gov (United States)

    Kaps, M; Curik, I; Baban, M

    2010-09-01

    Heterogeneity of variance of growth traits over age is a common issue in estimating genetic parameters and is addressed in this study by selecting appropriate variance structure models for additive genetic and environmental variances. Modeling and partitioning those variances connected with analyzing small data sets were demonstrated on Lipizzan horses. The following traits were analyzed: withers height, chest girth, and cannon bone circumference. The measurements were taken at birth, and at approximately 6, 12, 24, and 36 mo of age of 660 Lipizzan horses born in Croatia between 1948 and 2000. The corresponding pedigree file consisted of 1,458 horses. Sex, age of dam, and stud-year-season interaction were considered fixed effects; additive genetic and permanent environment effects were defined as random. Linear adjustments of age at measuring were done within measuring groups. Maternal effects were included only for measurements taken at birth and at 6 mo. Additive genetic variance structures were modeled by using uniform structures or structures based on polynomial random regression. Environmental variance structures were modeled by using one of the following models: unstructured, exponential, Gaussian, or combinations of identity or diagonal with structures based on polynomial random regression. The parameters were estimated by using REML. Comparison and fits of the models were assessed by using Akaike and Bayesian information criteria, and by checking graphically the adequacy of the shape of the overall (phenotypic) and component (additive genetic and environmental) variance functions. The best overall fit was obtained from models with unstructured error variance. Compared with the model with uniform additive genetic variance, models with structures based on random regression only slightly improved overall fit. Exponential and Gaussian models were generally not suitable because they do not accommodate adequately heterogeneity of variance. Using the unstructured

  7. Modeling Permanent Deformations of Superelastic and Shape Memory Materials

    Science.gov (United States)

    Urbano, Marco Fabrizio; Auricchio, Ferdinando

    2015-01-01

    In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement. PMID:26110494

  8. Modeling Permanent Deformations of Superelastic and Shape Memory Materials

    Directory of Open Access Journals (Sweden)

    Marco Fabrizio Urbano

    2015-06-01

    Full Text Available In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement.

  9. Attitude Estimation for Unresolved Agile Space Objects with Shape Model Uncertainty

    Science.gov (United States)

    Holzinger, M.; Alfriend, K. T.; Wetterer, C. J.; Luu, K. K.; Sabol, C.; Hamada, K.; Harms, A.

    2012-09-01

    The increasing number of manufactured on-orbit objects as well as improving sensor capabilities indicate that the number of trackable objects will likely exceed 100,000 within the next several years. Characterizing the large population of non-spatially resolved active spacecraft, retired spacecraft, rocket bodies, debris, and High Area to Mass Ratio (HAMR) objects necessarily involves both attitude and shape estimation. While spatially unresolved space objects cannot be directly imaged, attitude and shape may be inferred by carefully examining their lightcurves. Lightcurves are temporally-resolved sequences of photometric intensity measurements over one or more bandwidths. Because the observable reflected light from an unresolved space object is a strong function of both its shape and attitude, estimating these parameters using lightcurves can provide an avenue to determine both space object attitude and shape. This problem is traditionally called `lightcurve inversion.' While lightcurves have been used for 25 years to characterize spin states and shapes of asteroids, estimating the attitude states and shapes of manufactured space objects involves a new set of challenges. New challenges addressed in this paper are 1) An active (agile) space object is often directly controlling its attitude, meaning that torques acting on the space object are not necessarily zero (non-homogeneous motion) and mass properties may not be known, 2) Shape models must often be estimated, and as such contain errors that need to be accounted for in the measurement function, 3) Dynamics and measurement functions are excessively nonlinear, and manufactured space objects may be quite symmetric about at least one axis of rotation/reflection. This can lead to multiple possible attitude estimate solutions and suggests the use of non-Gaussian estimation approaches. Agile space objects (those that can actively maneuver) pose new problems to lightcurve inversion efforts to estimate attitude. Because

  10. Shape and Doppler corrected beamforming for low frequency active sonars

    NARCIS (Netherlands)

    Groen, J.; Beerens, S.P.; Doisy, Y.

    2004-01-01

    ASW operations have shifted toward shallow water environments, where water space is limited and manoeuvring an essential part of operations. The problem that is tackled in this article is the performance loss due to the shape and motion of a manoeuvring sonar. Standard beamforming in towed sonar arr

  11. A white-box model of S-shaped and double S-shaped single-species population growth.

    Science.gov (United States)

    Kalmykov, Lev V; Kalmykov, Vyacheslav L

    2015-01-01

    Complex systems may be mechanistically modelled by white-box modeling with using logical deterministic individual-based cellular automata. Mathematical models of complex systems are of three types: black-box (phenomenological), white-box (mechanistic, based on the first principles) and grey-box (mixtures of phenomenological and mechanistic models). Most basic ecological models are of black-box type, including Malthusian, Verhulst, Lotka-Volterra models. In black-box models, the individual-based (mechanistic) mechanisms of population dynamics remain hidden. Here we mechanistically model the S-shaped and double S-shaped population growth of vegetatively propagated rhizomatous lawn grasses. Using purely logical deterministic individual-based cellular automata we create a white-box model. From a general physical standpoint, the vegetative propagation of plants is an analogue of excitation propagation in excitable media. Using the Monte Carlo method, we investigate a role of different initial positioning of an individual in the habitat. We have investigated mechanisms of the single-species population growth limited by habitat size, intraspecific competition, regeneration time and fecundity of individuals in two types of boundary conditions and at two types of fecundity. Besides that, we have compared the S-shaped and J-shaped population growth. We consider this white-box modeling approach as a method of artificial intelligence which works as automatic hyper-logical inference from the first principles of the studied subject. This approach is perspective for direct mechanistic insights into nature of any complex systems.

  12. A white-box model of S-shaped and double S-shaped single-species population growth.

    Science.gov (United States)

    Kalmykov, Lev V; Kalmykov, Vyacheslav L

    2015-01-01

    Complex systems may be mechanistically modelled by white-box modeling with using logical deterministic individual-based cellular automata. Mathematical models of complex systems are of three types: black-box (phenomenological), white-box (mechanistic, based on the first principles) and grey-box (mixtures of phenomenological and mechanistic models). Most basic ecological models are of black-box type, including Malthusian, Verhulst, Lotka-Volterra models. In black-box models, the individual-based (mechanistic) mechanisms of population dynamics remain hidden. Here we mechanistically model the S-shaped and double S-shaped population growth of vegetatively propagated rhizomatous lawn grasses. Using purely logical deterministic individual-based cellular automata we create a white-box model. From a general physical standpoint, the vegetative propagation of plants is an analogue of excitation propagation in excitable media. Using the Monte Carlo method, we investigate a role of different initial positioning of an individual in the habitat. We have investigated mechanisms of the single-species population growth limited by habitat size, intraspecific competition, regeneration time and fecundity of individuals in two types of boundary conditions and at two types of fecundity. Besides that, we have compared the S-shaped and J-shaped population growth. We consider this white-box modeling approach as a method of artificial intelligence which works as automatic hyper-logical inference from the first principles of the studied subject. This approach is perspective for direct mechanistic insights into nature of any complex systems. PMID:26038717

  13. Investigating Energetic X-Shaped Flares on the Outskirts of A Solar Active Region

    Science.gov (United States)

    Liu, Rui; Chen, Jun; Wang, Yuming; Liu, Kai

    2016-09-01

    Typical solar flares display two quasi-parallel, bright ribbons on the chromosphere. In between is the polarity inversion line (PIL) separating concentrated magnetic fluxes of opposite polarity in active regions (ARs). Intriguingly a series of flares exhibiting X-shaped ribbons occurred at the similar location on the outskirts of NOAA AR 11967, where magnetic fluxes were scattered, yet three of them were alarmingly energetic. The X shape, whose center coincided with hard X-ray emission, was similar in UV/EUV, which cannot be accommodated in the standard flare model. Mapping out magnetic connectivities in potential fields, we found that the X morphology was dictated by the intersection of two quasi-separatrix layers, i.e., a hyperbolic flux tube (HFT), within which a separator connecting a double null was embedded. This topology was not purely local but regulated by fluxes and flows over the whole AR. The nonlinear force-free field model suggested the formation of a current layer at the HFT, where the current dissipation can be mapped to the X-shaped ribbons via field-aligned heat conduction. These results highlight the critical role of HFTs in 3D magnetic reconnection and have important implications for astrophysical and laboratory plasmas.

  14. Investigating Energetic X-Shaped Flares on the Outskirts of A Solar Active Region

    Science.gov (United States)

    Liu, Rui; Chen, Jun; Wang, Yuming; Liu, Kai

    2016-01-01

    Typical solar flares display two quasi-parallel, bright ribbons on the chromosphere. In between is the polarity inversion line (PIL) separating concentrated magnetic fluxes of opposite polarity in active regions (ARs). Intriguingly a series of flares exhibiting X-shaped ribbons occurred at the similar location on the outskirts of NOAA AR 11967, where magnetic fluxes were scattered, yet three of them were alarmingly energetic. The X shape, whose center coincided with hard X-ray emission, was similar in UV/EUV, which cannot be accommodated in the standard flare model. Mapping out magnetic connectivities in potential fields, we found that the X morphology was dictated by the intersection of two quasi-separatrix layers, i.e., a hyperbolic flux tube (HFT), within which a separator connecting a double null was embedded. This topology was not purely local but regulated by fluxes and flows over the whole AR. The nonlinear force-free field model suggested the formation of a current layer at the HFT, where the current dissipation can be mapped to the X-shaped ribbons via field-aligned heat conduction. These results highlight the critical role of HFTs in 3D magnetic reconnection and have important implications for astrophysical and laboratory plasmas. PMID:27677354

  15. The way organizational models shape human resource management practices and the perceptions of workers

    OpenAIRE

    Marques, Maria Amélia

    2012-01-01

    The main aim of this study was to analyse the way organizational models shape human resource management practices in firms linked to technology-intensive sectors. We used multiple-case study methodology. Four firms we chosen for the case study. The methodology included the use of a series of data collecting techniques, namely: interviews with HRM directors, questionnaires to workers, documental analysis and observation. Our main findings were, first, that the sector of activity, understood in...

  16. Bayes estimation of shape model with application to vertebrae boundaries

    DEFF Research Database (Denmark)

    Crimi, Alessandro; Ghosh, Anarta; Sporring, Jon;

    2009-01-01

    Estimation of the covariance matrix is a pivotal step in landmark based statistical shape analysis. For high dimensional representation of the shapes, often the number of available shape examples is far too small for reliable estimation of the covariance matrix by the traditionally used Maximum L...

  17. Shape optimization of active and passive drag-reducing devices on a D-shaped bluff body

    CERN Document Server

    Semaan, Richard

    2016-01-01

    Shape optimization of an active and a passive drag-reducing device on a two-dimensional D-shaped bluff body is performed. The two devices are: Coanda actuator, and randomly-shaped trailing-edge flap. The optimization sequence is performed by coupling the genetic algorithm software DAKOTA to the mesh generator Pointwise and to the CFD solver OpenFOAM. For the the active device the cost functional is the power ratio, whereas for the passive device it is the drag coefficient. The optimization leads to total power savings of $\\approx 70\\%$ for the optimal Coanda actuator, and a 40\\% drag reduction for the optimal flap. This reduction is mainly achieved through streamlining the base flow and suppressing the vortex shedding. The addition of either an active or a passive device creates two additional smaller recirculation regions in the base cavity that shifts the larger recirculation region away from the body and increases the base pressure. The results are validated against more refined URANS simulations for selec...

  18. A NEW DEFORMABLE MODEL USING LEVEL SETS FOR SHAPE SEGMENTALTION

    Institute of Scientific and Technical Information of China (English)

    He Ning; Zhang Peng; Lu Ke

    2009-01-01

    In this paper,we present a new deformable model for shape segmentation,which makes two modifications to the original level set implementation of deformable models.The modifications are motivated by difficulties that we have encountered in applying deformable models to segmentation of medical images.The level set algorithm has some advantages over the classical snake deformable models.However,it could develop large gaps in the boundary and holes within the objects.Such boundary gaps and holes of objects can cause inaccurate segmentation that requires manual correction.The proposed method in this paper possesses an inherent property to detect gaps and holes within the object with a single initial contour and also does not require specific initialization.The first modification is to replace the edge detector by some area constraint,and the second modification utilizes weighted length constraint to regularize the curve under evolution.The proposed method has been applied to both synthetic and real images with promising results.

  19. Styrene-based shape memory foam: fabrication and mathematical modeling

    Science.gov (United States)

    Yao, Yongtao; Zhou, Tianyang; Qin, Chao; Liu, Yanju; Leng, Jinsong

    2016-10-01

    Shape memory polymer foam is a promising kind of structure in the biomedical and aerospace field. Shape memory styrene foam with uniform and controlled open-cell structure was successfully fabricated using a salt particulate leaching method. Shape recovery capability exists for foam programming in both high-temperature compression and low-temperature compression (Shape recovery properties such as shape fixing property and shape recovery ratio were also characterized. In order to provide guidance for the future fabrication of shape memory foam, the theories of Gibson and Ashby as well as differential micromechanics theory were applied to predict Young’s modulus and the mechanical behavior of SMP styrene foams during the compression process.

  20. Active self-polarization of contractile cells in asymmetrically shaped domains

    Science.gov (United States)

    Zemel, A.; Safran, S. A.

    2007-08-01

    Mechanical forces generated by contractile cells allow the cells to sense their environment and to interact with other cells. By locally pulling on their environment, cells can sense and respond to mechanical features such as the local stress (or strain), the shape of a cellular domain, and the surrounding rigidity; at the same time, they also modify the mechanical state of the system. This creates a mechanical feedback loop that can result in self-polarization of cells. In this paper, we present a quantitative mechanical model that predicts the self-polarization of cells in spheroidally shaped domains, comprising contractile cells and an elastic matrix, that are embedded in a three-dimensional, cell-free gel. The theory is based on a generalization of the known results for passive inclusions in solids to include the effects of cell activity. We use the active cellular susceptibility tensor presented by Zemel [Phys. Rev. Lett. 97, 128103 (2006)] to calculate the polarization response and hence the elastic stress field developed by the cells in the cellular domain. The cell polarization is analyzed as a function of the shape and the elastic moduli of the cellular domain compared with the cell-free surrounding material. Consistent with experiment, our theory predicts the development of a stronger contractile force for cells in a gel that is surrounded by a large, cell-free material whose elastic modulus is stiffer than that of the gel that contains the cells. This provides a quantitative explanation of the differences in the development of cellular forces as observed in free and fixed gels. In the case of an asymmetrically shaped (spheroidal) domain of cells, we show that the anisotropic elastic field within the domain leads to a spontaneous self-polarization of the cells along the long axis of the domain.

  1. The Social Shaping of Canteen TakeAway activitis

    DEFF Research Database (Denmark)

    Poulsen, Signe

    or adjustments to solutions (inscription and domestication), together with theory about political processes, in order to capture both user perspectives and production perspectives of CTA. The results show that in all four cases CTA is established as an attempt to create aa better work-life balance...... the processes and results related to the shaping. The thesis is based on case studies at two hospitals, a financial company and an industrial worksite. Theoretically, the thesis draws on theories about design as the interaction between developers conceptions about potential users and the users’ rejection...

  2. An active contour framework based on the Hermite transform for shape segmentation of cardiac MR images

    Science.gov (United States)

    Barba-J, Leiner; Escalante-Ramírez, Boris

    2016-04-01

    Early detection of cardiac affections is fundamental to address a correct treatment that allows preserving the patient's life. Since heart disease is one of the main causes of death in most countries, analysis of cardiac images is of great value for cardiac assessment. Cardiac MR has become essential for heart evaluation. In this work we present a segmentation framework for shape analysis in cardiac magnetic resonance (MR) images. The method consists of an active contour model which is guided by the spectral coefficients obtained from the Hermite transform (HT) of the data. The HT is used as model to code image features of the analyzed images. Region and boundary based energies are coded using the zero and first order coefficients. An additional shape constraint based on an elliptical function is used for controlling the active contour deformations. The proposed framework is applied to the segmentation of the endocardial and epicardial boundaries of the left ventricle using MR images with short axis view. The segmentation is sequential for both regions: the endocardium is segmented followed by the epicardium. The algorithm is evaluated with several MR images at different phases of the cardiac cycle demonstrating the effectiveness of the proposed method. Several metrics are used for performance evaluation.

  3. MEG inversion using spherical head model combined with brain-shaped head model

    Institute of Scientific and Technical Information of China (English)

    LI Jun

    2001-01-01

    The spherical head model has been widely used in magnetoen cephalography (MEG) as a simple forward model for calculating the external mag netic field producing by neural currents in a human brain. But this model may lead to an inaccurate result, even if the computation speed is fast. For more precise computation, realistic brain-shaped head model is used with the boundary element method (BME), but at greatly increased computational cost. When solving MEG inverse problem by using optimization methods, the forward problem must often be solved for thousands of possible source configurations. So if the brain-shaped head model is used in all iterative steps of optimization, it may be computationally infeasible for practical application. In this paper, we present a method about using compound head model in MEG inverse solution. In this method, first spherical head model is used for a rough estimation, then brain-shaped head model is adopted for more precise solution. Numerical simulation indicates that under the condition of same accuracy, the computation speed for the present method is about three times faster than a method using the brain-shaped head model at all iterations.

  4. Unified Taxonomy for Reference Ontology of Shape Features in Product Model

    OpenAIRE

    Gupta, Ravi Kumar; Gurumoorthy, B

    2013-01-01

    This paper presents a unified taxonomy of shape features. Such taxonomy is required to construct ontologies to address heterogeneity in product/shape models. Literature provides separate classifications for volumetric, deformation and free-form surface features. The unified taxonomy proposed allows classification, representation and extraction of shape features in a product model. The novelty of the taxonomy is that the classification is based purely on shape entities and therefore it is poss...

  5. Segmentation of the left ventricular endocardium from magnetic resonance images by using different statistical shape models.

    Science.gov (United States)

    Piazzese, Concetta; Carminati, M Chiara; Colombo, Andrea; Krause, Rolf; Potse, Mark; Auricchio, Angelo; Weinert, Lynn; Tamborini, Gloria; Pepi, Mauro; Lang, Roberto M; Caiani, Enrico G

    2016-01-01

    We evaluate in this paper different strategies for the construction of a statistical shape model (SSM) of the left ventricle (LV) to be used for segmentation in cardiac magnetic resonance (CMR) images. From a large database of LV surfaces obtained throughout the cardiac cycle from 3D echocardiographic (3DE) LV images, different LV shape models were built by varying the considered phase in the cardiac cycle and the registration procedure employed for surface alignment. Principal component analysis was computed to describe the statistical variability of the SSMs, which were then deformed by applying an active shape model (ASM) approach to segment the LV endocardium in CMR images of 45 patients. Segmentation performance was evaluated by comparing LV volumes derived by ASM segmentation with different SSMs and those obtained by manual tracing, considered as a reference. A high correlation (r(2)>0.92) was found in all cases, with better results when using the SSM models comprising more than one frame of the cardiac cycle. PMID:27046100

  6. Hippocampal sub-regional shape and physical activity in older adults.

    Science.gov (United States)

    Varma, Vijay R; Tang, Xiaoying; Carlson, Michelle C

    2016-08-01

    Hippocampal atrophy is a hallmark of Alzheimer's disease pathology, and a target biomarker region for testing intervention efficacy. Over the last few decades, a growing body of evidence from animal and human models suggests that physical activity (PA) is associated with structural benefits to the hippocampus in older adults. Very few human studies, however have explored hippocampal sub-regional specificity of PA; this is significant considering that sub-regions of the hippocampus are associated with distinct cognitive tasks and are differentially affected by disease pathology. This study used objective and self-reported measures of daily walking activity and exercise, and surface-based regional shape analysis using high-field hippocampal sub-regional partitions to explore sub-region specific hippocampal associations in a sample of nondemented, community-dwelling older adults at elevated sociodemographic risk for cognitive decline. Vertex-wise surface areas, which may be more sensitive than global volume measures, were calculated using shape diffeomorphometry, and PA was assessed using step activity monitors and PA questionnaires. We found that daily walking activity in a participant's environment was associated in cross-section mainly with larger surface areas of the subiculum in women. Associations remained significant when controlling for self-reported exercise. Prior studies have found that PA related to exercise and aerobic fitness may be most closely associated with the anterior hippocampus, particularly the dentate gyrus of the hippocampus. These novel findings are the first, to our knowledge, in human models to suggest that PA related to navigation that may not reach the level of moderate-intensity exercise may be associated with specific sub-regions of the hippocampus. These findings underscore the importance of better understanding the independent and related biological mechanisms and pathways by which increasing exercise as well as non

  7. Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments

    Directory of Open Access Journals (Sweden)

    A. Lendlein

    2012-01-01

    Full Text Available Thermo-sensitive shape-memory polymers (SMP, which are capable of memorizing two or more different shapes, have generated significant research and technological interest. A triple-shape effect (TSE of SMP can be activated e.g. by increasing the environmental temperature (Tenv, whereby two switching temperatures (Tsw have to be exceeded to enable the subsequent shape changes from shape (A to shape (B and finally the original shape (C. In this work, we explored the thermally and magnetically initiated shape-memory properties of triple-shape nanocomposites with various compositions and particle contents using different shape-memory creation procedures (SMCP. The nanocomposites were prepared by the incorporation of magnetite nanoparticles into a multiphase polymer network matrix with grafted polymer network architecture containing crystallizable poly(ethylene glycol (PEG side chains and poly(ε-caprolactone (PCL crosslinks named CLEGC. Excellent triple-shape properties were achieved for nanocomposites with high PEG weight fraction when two-step programming procedures were applied. In contrast, single-step programming resulted in dual-shape properties for all investigated materials as here the temporary shape (A was predominantly fixed by PCL crystallites.

  8. Whole vertebral bone segmentation method with a statistical intensity-shape model based approach

    Science.gov (United States)

    Hanaoka, Shouhei; Fritscher, Karl; Schuler, Benedikt; Masutani, Yoshitaka; Hayashi, Naoto; Ohtomo, Kuni; Schubert, Rainer

    2011-03-01

    An automatic segmentation algorithm for the vertebrae in human body CT images is presented. Especially we focused on constructing and utilizing 4 different statistical intensity-shape combined models for the cervical, upper / lower thoracic and lumbar vertebrae, respectively. For this purpose, two previously reported methods were combined: a deformable model-based initial segmentation method and a statistical shape-intensity model-based precise segmentation method. The former is used as a pre-processing to detect the position and orientation of each vertebra, which determines the initial condition for the latter precise segmentation method. The precise segmentation method needs prior knowledge on both the intensities and the shapes of the objects. After PCA analysis of such shape-intensity expressions obtained from training image sets, vertebrae were parametrically modeled as a linear combination of the principal component vectors. The segmentation of each target vertebra was performed as fitting of this parametric model to the target image by maximum a posteriori estimation, combined with the geodesic active contour method. In the experimental result by using 10 cases, the initial segmentation was successful in 6 cases and only partially failed in 4 cases (2 in the cervical area and 2 in the lumbo-sacral). In the precise segmentation, the mean error distances were 2.078, 1.416, 0.777, 0.939 mm for cervical, upper and lower thoracic, lumbar spines, respectively. In conclusion, our automatic segmentation algorithm for the vertebrae in human body CT images showed a fair performance for cervical, thoracic and lumbar vertebrae.

  9. Shape-Enhanced Photocatalytic Activities of Thoroughly Mesoporous ZnO Nanofibers

    KAUST Repository

    Ren, Xiaolong

    2016-06-24

    1D mesoporous materials have attracted extensive interest recently, owning to their fascinating properties and versatile applications. However, it remains as a grand challenge to develop a simple and efficient technique to produce oxide nanofibers with mesoporous architectures, controlled morphologies, large surface areas, and optimal performances. In this work, a facile foaming-assisted electrospinning strategy with foaming agent of tea saponin is used to produce thoroughly mesoporous ZnO nanofibers with high purity and controlled morphology. Interestingly, mesoporous fibers with elliptical cross-section exhibit the significantly enhanced photocatalytic activity for hydrogen production, as compared to the counterparts with circular and rectangular cross-sections, and they also perform better than the commercial ZnO nanopowders. The unexpected shape dependence of photocatalytic activities is attributed to the different stacking modes of the mesoporous fibers, and a geometrical model is developed to account for the shape dependence. This work represents an important step toward producing thoroughly mesoporous ZnO nanofibers with tailored morphologies, and the discovery that fibers with elliptical cross-section render the best performance provides a valuable guideline for improving the photocatalytic performance of such mesoporous nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Investigating Energetic X-Shaped Flares on the Outskirts of A Solar Active Region

    CERN Document Server

    Liu, Rui; Wang, Yuming; Liu, Kai

    2016-01-01

    Typical solar flares display two quasi-parallel, bright ribbons on the chromosphere. In between is the polarity inversion line (PIL) separating concentrated magnetic fluxes of opposite polarity in active regions (ARs). Intriguingly a series of flares exhibiting X-shaped ribbons occurred at the similar location on the outskirts of NOAA AR 11967, where magnetic fluxes were scattered, yet three of them were alarmingly energetic. The X shape, whose center coincided with hard X-ray emission, was similar in UV/EUV, which cannot be accommodated in the standard flare model. Mapping out magnetic connectivities in potential fields, we found that the X morphology was dictated by the intersection of two quasi-separatrix layers, i.e., a hyperbolic flux tube (HFT), within which a separator connecting a double null was embedded. This topology was not purely local but regulated by fluxes and flows over the whole AR. The nonlinear force-free field model suggested the formation of a current layer at the HFT, where the current ...

  11. Segmentation of uterine fibroid ultrasound images using a dynamic statistical shape model in HIFU therapy.

    Science.gov (United States)

    Ni, Bo; He, Fazhi; Yuan, ZhiYong

    2015-12-01

    Segmenting the lesion areas from ultrasound (US) images is an important step in the intra-operative planning of high-intensity focused ultrasound (HIFU). However, accurate segmentation remains a challenge due to intensity inhomogeneity, blurry boundaries in HIFU US images and the deformation of uterine fibroids caused by patient's breathing or external force. This paper presents a novel dynamic statistical shape model (SSM)-based segmentation method to accurately and efficiently segment the target region in HIFU US images of uterine fibroids. For accurately learning the prior shape information of lesion boundary fluctuations in the training set, the dynamic properties of stochastic differential equation and Fokker-Planck equation are incorporated into SSM (referred to as SF-SSM). Then, a new observation model of lesion areas (named to RPFM) in HIFU US images is developed to describe the features of the lesion areas and provide a likelihood probability to the prior shape given by SF-SSM. SF-SSM and RPFM are integrated into active contour model to improve the accuracy and robustness of segmentation in HIFU US images. We compare the proposed method with four well-known US segmentation methods to demonstrate its superiority. The experimental results in clinical HIFU US images validate the high accuracy and robustness of our approach, even when the quality of the images is unsatisfactory, indicating its potential for practical application in HIFU therapy.

  12. Segmentation of uterine fibroid ultrasound images using a dynamic statistical shape model in HIFU therapy.

    Science.gov (United States)

    Ni, Bo; He, Fazhi; Yuan, ZhiYong

    2015-12-01

    Segmenting the lesion areas from ultrasound (US) images is an important step in the intra-operative planning of high-intensity focused ultrasound (HIFU). However, accurate segmentation remains a challenge due to intensity inhomogeneity, blurry boundaries in HIFU US images and the deformation of uterine fibroids caused by patient's breathing or external force. This paper presents a novel dynamic statistical shape model (SSM)-based segmentation method to accurately and efficiently segment the target region in HIFU US images of uterine fibroids. For accurately learning the prior shape information of lesion boundary fluctuations in the training set, the dynamic properties of stochastic differential equation and Fokker-Planck equation are incorporated into SSM (referred to as SF-SSM). Then, a new observation model of lesion areas (named to RPFM) in HIFU US images is developed to describe the features of the lesion areas and provide a likelihood probability to the prior shape given by SF-SSM. SF-SSM and RPFM are integrated into active contour model to improve the accuracy and robustness of segmentation in HIFU US images. We compare the proposed method with four well-known US segmentation methods to demonstrate its superiority. The experimental results in clinical HIFU US images validate the high accuracy and robustness of our approach, even when the quality of the images is unsatisfactory, indicating its potential for practical application in HIFU therapy. PMID:26459767

  13. Modeling the dynamic behavior of a shape memory alloy actuated catheter

    Science.gov (United States)

    Veeramani, Arun S.; Buckner, Gregory D.; Owen, Stephen B.; Cook, Richard C.; Bolotin, Gil

    2008-02-01

    In this paper we investigate the transient behavior of a simple active catheter: a central tube actuated by a single nitinol tendon enclosed by an outer sleeve. Dynamic models are developed to characterize the transient behavior and optimize the design of an experimental prototype. The bending mechanics are derived using a circular arc model and are experimentally validated. Nitinol actuation is described using the Seelecke-Muller-Achenbach model for single-crystal shape memory alloys using experimentally determined parameters. The dynamic characteristics of this active catheter system are simulated and compared with experimental results. Joule heating is used to generate tip deflections, which are computed in real time using a dual-camera imaging system. The effects of outer sleeve thickness on heat transfer and transient response characteristics are studied.

  14. Shape memory actuators - potentials and specifics of their technical use and electrical activation

    Directory of Open Access Journals (Sweden)

    J. Strittmatter a,b

    2012-12-01

    Full Text Available Due to a martensitic phase change shape memory alloys can revert to their original shape by heating when they undergo an appropriate treatment. Actuator elements with this shape memory effect can show a significant design change combined with a considerable force. Therefore they can be used to solve many technical tasks in the field of actuating elements and mechatronics. These intelligent materials will play an increasing role in the next years, especially within the automotive technology, energy management, power and mechanical engineering as well as medical technology. In order to use the potential of these materials in an optimal way it is necessary to know and understand the extraordinary and unconventional properties of shape memory alloys.This paper will present the commonly used systems of shape memory alloys of today including their performance characteristics and will explain the basics of the shape memory effect in a vivid way. A multitude of application possibilities of shape memory actuators will be presented, in particular the research and development projects that have been carried out at the Konstanz University of Applied Sciences during the last years. In this way a solid state heat engine and an intramedullary nail for bone elongation will be presented as well as various adaptive systems for automotive safety and comfort systems, driven by shape memory elements. Regarding the applications in the automotive field a special focus will be given to different electrical activations to enable very fast contraction times of the shape memory components.

  15. Analytical modeling and experimental validation of a V-shape piezoelectric ultrasonic transducer

    Science.gov (United States)

    Li, Xiaoniu; Yao, Zhiyuan

    2016-07-01

    In this paper, an analytical model of a V-shape piezoelectric ultrasonic transducer is presented. The V-shape piezoelectric ultrasonic transducer has been widely applied to the piezoelectric actuator (ultrasonic motor), ultrasonic aided fabrication, sensor, and energy harvesting device. The V-shape piezoelectric ultrasonic transducer consists of two Langevin-type transducers connected together through a coupling point with a certain coupling angle. Considering the longitudinal and lateral movements of a single beam, the symmetrical and asymmetrical modals of the V-shape piezoelectric ultrasonic transducer are calculated. By using Hamilton–Lagrange equations, the electromechanical coupling model of the V-shape piezoelectric ultrasonic transducer is proposed. The influence of the coupling angle and cross-section on modal characteristics and electromechanical coupling coefficient are analyzed by the analytical model. A prototype of the V-shape piezoelectric ultrasonic transducer is fabricated, and the results of the experiments are in good agreement with the analytical model.

  16. Asteroid spin and shape modelling using two lightcurve inversion methods

    Science.gov (United States)

    Marciniak, Anna; Bartczak, Przemyslaw; Konstanciak, Izabella; Dudzinski, Grzegorz; Mueller, Thomas G.; Duffard, Rene

    2016-10-01

    We are conducting an observing campaign to counteract strong selection effects in photometric studies of asteroids. Our targets are long-period (P>12 hours) and low-amplitude (a_maxstudied in terms of their spins and shapes. Our campaign targets a sample of around 100 bright (Hadaptive optics imaging) or against data in thermal infrared range gathered by ground and space-bound observatories. The thermal data could provide assignment of size and albedo, but also can help to resolve spin-pole ambiguities. In special cases, the thermal data from Spitzer and Wise/NEOWise might even help in testing specific shape features via thermal infrared lightcurves.

  17. Analysis of Body Shapes and Physical Activity Dominant Patterns in a Coloring Books Collection

    Directory of Open Access Journals (Sweden)

    Vladimir Martínez Bello

    2014-06-01

    Full Text Available Curriculum materials play an important role in the construction of the concept of the body to the extent that they are transmitters of knowledge, ideas and values. The aim of the study was to analyse whether the images in a collection of coloring books entitled The Boys´ Doodles Book and The girl´s Doodles Book show sexist stereotypes about body models and dominant patterns of physical activity. An independent observational group studied the images of the body through content analysis with a coding scheme using categories (gender, age, somatotype, space and type of physical activity previously adopted by experts. The Boys´ Doodles Book shows an adult man with different body types, while women are not represented. In both books, the bodies do not maintain a preferred location. The Girls´Doodles Book represents a higher percentage of girls with a slender body, while men, who were under-represented, assume different body types. The Girls´Doodles Book tends to represent women in physical activities or sports with an artistic component. In conclusion, the images in both coloring books, promote sexist body shapes and physical activities. It is a warning to parents and mothers, as well as publishing houses, libraries and government agencies to critically analyse underlying patterns on coloring books.

  18. An integrated numerical model for the prediction of Gaussian and billet shapes

    DEFF Research Database (Denmark)

    Hattel, Jesper; Pryds, Nini; Pedersen, Trine Bjerre

    2004-01-01

    Separate models for the atomisation and the deposition stages were recently integrated by the authors to form a unified model describing the entire spray-forming process. In the present paper, the focus is on describing the shape of the deposited material during the spray-forming process, obtained...... and the shading effect for Gaussian and billet shape, respectively. From the obtained results, the effect of these parameters on the final shape is illustrated. (C) 2004 Elsevier B.V. All rights reserved....

  19. A Vertical Resonance Heating Model for X- or Peanut-Shaped Galactic Bulges

    OpenAIRE

    Quillen, Alice C.; Minchev, Ivan; Sharma, Sanjib; Qin, Yu-Jing; Di Matteo, Paola

    2013-01-01

    We explore a second order Hamiltonian vertical resonance model for X-shaped or peanut-shaped galactic bulges. The X-shape is caused by the 2:1 vertical Lindblad resonance with the bar, with two vertical oscillation periods per orbital period in the bar frame. We examine N-body simulations and find that due to the bar slowing down and disk thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the vertical re...

  20. Shape interior modeling and mass property optimization using ray-reps

    DEFF Research Database (Denmark)

    Wu, Jun; Kramer, Lou; Westermann, Rüdiger

    2016-01-01

    We present a novel method for the modeling and optimization of the material distribution inside 3D shapes, such that their 3D printed replicas satisfy prescribed constraints regarding mass properties. In particular, we introduce an extension of ray-representation to shape interior modeling...

  1. Improved shape hardening function for bounding surface model for cohesive soils

    Institute of Scientific and Technical Information of China (English)

    Andrés Nieto-Leal; Victor N.Kaliakin

    2014-01-01

    A shape hardening function is developed that improves the predictive capabilities of the generalized bounding surface model for cohesive soils, especially when applied to overconsolidated specimens. This improvement is realized without any changes to the simple elliptical shape of the bounding surface, and actually reduces the number of parameters associated with the model by one.

  2. Improved shape hardening function for bounding surface model for cohesive soils

    Directory of Open Access Journals (Sweden)

    Andrés Nieto-Leal

    2014-08-01

    Full Text Available A shape hardening function is developed that improves the predictive capabilities of the generalized bounding surface model for cohesive soils, especially when applied to overconsolidated specimens. This improvement is realized without any changes to the simple elliptical shape of the bounding surface, and actually reduces the number of parameters associated with the model by one.

  3. Shape-dependent bactericidal activity of copper oxide nanoparticle mediated by DNA and membrane damage

    Energy Technology Data Exchange (ETDEWEB)

    Laha, Dipranjan; Pramanik, Arindam [Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S C Mallick Road, Kolkata 700032 (India); Laskar, Aparna [CSIR-Indian Institute of Chemical Biology, Kolkata 700032 (India); Jana, Madhurya [Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S C Mallick Road, Kolkata 700032 (India); Pramanik, Panchanan [Department of Chemistry, Indian Institute of Technology, Kharagpur 721302 (India); Karmakar, Parimal, E-mail: pkarmakar_28@yahoo.co.in [Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S C Mallick Road, Kolkata 700032 (India)

    2014-11-15

    Highlights: • Spherical and sheet shaped copper oxide nanoparticles were synthesized. • Physical characterizations of these nanoparticles were done by TEM, DLS, XRD, FTIR. • They showed shape dependent antibacterial activity on different bacterial strain. • They induced both membrane damage and ROS mediated DNA damage in bacteria. - Abstract: In this work, we synthesized spherical and sheet shaped copper oxide nanoparticles and their physical characterizations were done by the X-ray diffraction, fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. The antibacterial activity of these nanoparticles was determined on both gram positive and gram negative bacterial. Spherical shaped copper oxide nanoparticles showed more antibacterial property on gram positive bacteria where as sheet shaped copper oxide nanoparticles are more active on gram negative bacteria. We also demonstrated that copper oxide nanoparticles produced reactive oxygen species in both gram negative and gram positive bacteria. Furthermore, they induced membrane damage as determined by atomic force microscopy and scanning electron microscopy. Thus production of and membrane damage are major mechanisms of the bactericidal activity of these copper oxide nanoparticles. Finally it was concluded that antibacterial activity of nanoparticles depend on physicochemical properties of copper oxide nanoparticles and bacterial strain.

  4. Computational Modeling aided Near Net Shape Manufacturing for Aluminum Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This program will focus on developing and validating computational models for near-net shape processing of aluminum alloys. Computational models will be developed...

  5. Thermo-mechanical finite element modeling of shape memory materials’ microindentation

    Science.gov (United States)

    Perlovich, Yu A.; Isaenkova, M. G.; Krymskaya, O. A.; Zhuk, D. I.

    2016-04-01

    Indentation of shape memory materials and later heating with recovery of indent is studied in this work using finite element modelling. Results of simulations of two types of shape memory materials, with one-way shape memory effect and with superelastic properties compared to experimental indentation with 200μm spherical indenter. Based on results of finite element modeling, several useful quantities plotted for loading, unloading and thermal recovery for various materials with shape memory effect. Recovery of imprint made with Berkovich (three-sided pyramid) compared to recovery of imprint made with spherical indenter.

  6. Thermally Activated Composite with Two-Way and Multi-Shape Memory Effects

    Directory of Open Access Journals (Sweden)

    Bernard Durand

    2013-09-01

    Full Text Available The use of shape memory polymer composites is growing rapidly in smart structure applications. In this work, an active asymmetric composite called “controlled behavior composite material (CBCM” is used as shape memory polymer composite. The programming and the corresponding initial fixity of the composite structure is obtained during a bending test, by heating CBCM above thermal glass transition temperature of the used Epoxy polymer. The shape memory properties of these composites are investigated by a bending test. Three types of recoveries are conducted, two classical recovery tests: unconstrained recovery and constrained recovery, and a new test of partial recovery under load. During recovery, high recovery displacement and force are produced that enables the composite to perform strong two-way actuations along with multi-shape memory effect. The recovery force confirms full recovery with two-way actuation even under a high load. This unique property of CBCM is characterized by the recovered mechanical work.

  7. Active illumination and appearance model for face alignment

    DEFF Research Database (Denmark)

    Kahraman, Fatih; Gokmen, M.; Darkner, Sune;

    2010-01-01

    Active Illumination and Appearance Model (AIA) which combines identity, illumination and shape components in a single model and allows us to control them, separately. One of the major advantage of the proposed AIA model is that efficient model fitting is achieved, whilst maintaining performance against...

  8. Incorporating S-shaped testing-effort functions into NHPP software reliability model with imperfect debugging

    Institute of Scientific and Technical Information of China (English)

    Qiuying Li; Haifeng Li; Minyan Lu

    2015-01-01

    Testing-effort (TE) and imperfect debugging (ID) in the reliability modeling process may further improve the fitting and pre-diction results of software reliability growth models (SRGMs). For describing the S-shaped varying trend of TE increasing rate more accurately, first, two S-shaped testing-effort functions (TEFs), i.e., delayed S-shaped TEF (DS-TEF) and inflected S-shaped TEF (IS-TEF), are proposed. Then these two TEFs are incorporated into various types (exponential-type, delayed S-shaped and in-flected S-shaped) of non-homogeneous Poisson process (NHPP) SRGMs with two forms of ID respectively for obtaining a series of new NHPP SRGMs which consider S-shaped TEFs as wel as ID. Final y these new SRGMs and several comparison NHPP SRGMs are applied into four real failure data-sets respectively for investigating the fitting and prediction power of these new SRGMs. The experimental results show that: (i) the proposed IS-TEF is more suitable and flexible for describing the consumption of TE than the previous TEFs; (i ) incorporating TEFs into the inflected S-shaped NHPP SRGM may be more effective and appropriate compared with the exponential-type and the delayed S-shaped NHPP SRGMs; (i i) the inflected S-shaped NHPP SRGM con-sidering both IS-TEF and ID yields the most accurate fitting and prediction results than the other comparison NHPP SRGMs.

  9. Fuzzy Shape Control Based on Elman Dynamic Recursion Network Prediction Model

    Institute of Scientific and Technical Information of China (English)

    JIA Chun-yu; LIU Hong-min

    2006-01-01

    In the strip rolling process, shape control system possesses the characteristics of nonlinearity, strong coupling, time delay and time variation. Based on self-adapting Elman dynamic recursion network prediction model, the fuzzy control method was used to control the shape on four-high cold mill. The simulation results showed that the system can be applied to real time on line control of the shape.

  10. A Solvable Model for Nuclear Shape Phase Transitions

    International Nuclear Information System (INIS)

    There has been considerable interest recently in phase transitions that occur between some well-defined nuclear shapes, e.g. the spherical vibrator, the axially deformed rotor and the γ-unstable rotor, which are assigned to the U(5), SU(3) and 0(6) symmetries. These shape phase transitions occur through critical points of the IBM phase diagram and correspond to rapid structural changes. The first transition of this type describes transition form the spherical to the γ-unstable phase and has been associated with an E(5) symmetry. Later further critical point symmetries e.g. X(5) and Y(5) have also been proposed for transitions between other nuclear shape phases. In another application the chain of even Ru isotopes was considered from A 98 to 112 [2]. The parameters were extracted from a fit to the low-lying energy spectrum of each nucleus and were used to plot the corresponding potential. It was found that up to A =102 the potential is essentially an harmonic oscillator, while at A =104 a rather flat potential was seen, in accordance with the expected phase transition and E(5) symmetry there. With increasing A then the minimum got increasingly deeper and moved away from β = 0. We discuss the possibility of generalizing the formalism in two ways: first by including dependence on the 7 variable allowing for the approximate description of nuclei close to the X(5) symmetry, and second, including higher-lying energy levels in the quasi-exactly solvable formalism

  11. Thermophysical modeling of asteroids from WISE thermal infrared data - Significance of the shape model and the pole orientation uncertainties

    Science.gov (United States)

    Hanuš, J.; Delbo', M.; Ďurech, J.; Alí-Lagoa, V.

    2015-08-01

    In the analysis of thermal infrared data of asteroids by means of thermophysical models (TPMs) it is a common practice to neglect the uncertainty of the shape model and the rotational state, which are taken as an input for the model. Here, we present a novel method of investigating the importance of the shape model and the pole orientation uncertainties in the thermophysical modeling - the varied shape TPM (VS-TPM). Our method uses optical photometric data to generate various shape models that map the uncertainty in the shape and the rotational state. The TPM procedure is then run for all these shape models. We apply the implementation of the classical TPM as well as our VS-TPM to the convex shape models of several asteroids together with their thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer (WISE) and compare the results. These show that the uncertainties of the shape model and the pole orientation can be very important (e.g., for the determination of the thermal inertia) and should be considered in the thermophysical analyses. We present thermophysical properties for six asteroids - (624) Hektor, (771) Libera, (1036) Ganymed, (1472) Muonio, (1627) Ivar, and (2606) Odessa.

  12. Thermophysical modeling of asteroids from WISE thermal infrared data - Significance of the shape model and the pole orientation uncertainties

    CERN Document Server

    Hanuš, Josef; Ďurech, Josef; Alí-Lagoa, Victor

    2015-01-01

    In the analysis of thermal infrared data of asteroids by means of thermophysical models (TPMs) it is a common practice to neglect the uncertainty of the shape model and the rotational state, which are taken as an input for the model. Here, we present a novel method of investigating the importance of the shape model and the pole orientation uncertainties in the thermophysical modeling - the varied shape TPM (VS-TPM). Our method uses optical photometric data to generate various shape models that map the uncertainty in the shape and the rotational state. The TPM procedure is then run for all these shape models. We apply the implementation of the classical TPM as well as our VS-TPM to the convex shape models of several asteroids together with their thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer (WISE) and compare the results. These show that the uncertainties of the shape model and the pole orientation can be very important (e.g., for the determination of the thermal inertia) and...

  13. Visualization of a Fish Behavior using Successive Three-Dimensional Shape Modeling

    OpenAIRE

    Doi, Junta; Miyake, Tetsuo

    2000-01-01

    Visualization of a three-dimensional fish behavior based on the successive feature extraction using the time sequential three-dimensional shape modeling is reported. The principle of the modeling is based on the intersected viewing pyramid consisting of each image boundary of the object and the corresponding focal point. Threedirectional video images are simultaneously acquired and sequential solid models are then reconstructed to obtain behavioral parameters such as body shape, skeleton, hea...

  14. Modified peak shape method for the determination of activation energy in thermoluminescence

    International Nuclear Information System (INIS)

    We have reconsidered the peak shape method in thermoluminescence by taking into account the main difficulty of the peak shape method, i.e. the dependence of the symmetry factor μ g on um (=E/kTm ) , where E is the activation energy, Tm is the peak temperature and k is the Boltzmann constant. In the present paper, the peak shape method is improved by taking into account this dependence. Finally, the applicability of the present findings has been analyzed by considering both synthetic and experimental thermoluminescence curves including glow curves of the most common dosimetric material LiF : Mg, Ti (TLD-100). It is also found that activation energies as calculated by the present method are in good agreement with those calculated by the rigorous method of curve fitting.

  15. Content-Based Search on a Database of Geometric Models: Identifying Objects of Similar Shape

    Energy Technology Data Exchange (ETDEWEB)

    XAVIER, PATRICK G.; HENRY, TYSON R.; LAFARGE, ROBERT A.; MEIRANS, LILITA; RAY, LAWRENCE P.

    2001-11-01

    The Geometric Search Engine is a software system for storing and searching a database of geometric models. The database maybe searched for modeled objects similar in shape to a target model supplied by the user. The database models are generally from CAD models while the target model may be either a CAD model or a model generated from range data collected from a physical object. This document describes key generation, database layout, and search of the database.

  16. Modeling Macroscopic Shape Distortions during Sintering of Multi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye

    capabilities of the existing constitutive models. In this context, a simulation method or framework has been developed, which involves the use of sintering experiments, analytical and numerical methods. In addition to the intrinsic material parameters (shrinkage and viscous behaviors), the effect of extrinsic...... been developed. The linear version of the Skorohod Olevsky Viscous Sintering (SOVS) model has been used in the developed simulation models. A combination of free shrinkage rate measurements from optical dilatometry and analytical models has been used to determine the necessary input parameters....... This model excels in requiring a single optical dilatometry run to collect all the necessary input parameters for modeling of the sintering of the bi-layers. The determined input parameters have also been used in a finite element model, which is developed based on the continuum theory of sintering, to model...

  17. Modeling concepts for communication of geometric shape data

    Science.gov (United States)

    Collins, M. F.; Emnett, R. F.; Magedson, R. L.; Shu, H. H.

    1984-01-01

    ANSI5, an abbreviation for Section 5 of the American National Standard under Engineering Drawing and Related Documentation Practices (Committee Y14) on Digital Representation for Communication of Product Definition Data (ANSI Y14.26M-1981), allows encoding of a broad range of geometric shapes to be communicated through digital channels. A brief review of its underlying concepts is presented. The intent of ANSI5 is to devise a unified set of concise language formats for transmission of data pertaining to five types of geometric entities in Euclidean 3 space (E(3)). These are regarded as point like, curve like, surface like, solid like, and a combination of these types. For the first four types, ANSI5 makes a distinction between the geometry and topology. Geometry is a description of the spatial occupancy of the entity, and topology discusses the interconnectedness of the entity's boundary components.

  18. Leidenfrost effect: Accurate drop shape modeling and refined scaling laws.

    Science.gov (United States)

    Sobac, B; Rednikov, A; Dorbolo, S; Colinet, P

    2014-11-01

    We here present a simple fitting-parameter-free theory of the Leidenfrost effect (droplet levitation above a superheated plate) covering the full range of stable shapes, i.e., from small quasispherical droplets to larger puddles floating on a pocketlike vapor film. The geometry of this film is found to be in excellent quantitative agreement with the interferometric measurements of Burton et al. [Phys. Rev. Lett. 109, 074301 (2012)PRLTAO0031-900710.1103/PhysRevLett.109.074301]. We also obtain new scalings generalizing classical ones derived by Biance et al. [Phys. Fluids 15, 1632 (2003)PHFLE61070-663110.1063/1.1572161] as far as the effect of plate superheat is concerned and highlight the relative role of evaporation, gravity, and capillarity in the vapor film. To further substantiate these findings, a treatment of the problem by matched asymptotic expansions is also presented. PMID:25493885

  19. Wave shape classification of spontaneous neuronal activity in cortical cultures on micro-electrode arrays

    OpenAIRE

    Staveren, van, R.; Buitenweg, J.R.; Heida, T.; Rutten, W.L.C.

    2002-01-01

    Dissociated embryonal or postnatal rat cortical cells were cultured onto multi electrode arrays (MEA's) with 61 electrode sites. They developed into networks and became spontaneously active after about one week in vitro. About 180,000 recorded action potential waveforms were sorted using several spike features and classified with a Mahalanobis distance sorting procedure. They were classified into six basic wave shapes.

  20. Atypical balance between occipital and fronto-parietal activation for visual shape extraction in dyslexia.

    Directory of Open Access Journals (Sweden)

    Ying Zhang

    Full Text Available Reading requires the extraction of letter shapes from a complex background of text, and an impairment in visual shape extraction would cause difficulty in reading. To investigate the neural mechanisms of visual shape extraction in dyslexia, we used functional magnetic resonance imaging (fMRI to examine brain activation while adults with or without dyslexia responded to the change of an arrow's direction in a complex, relative to a simple, visual background. In comparison to adults with typical reading ability, adults with dyslexia exhibited opposite patterns of atypical activation: decreased activation in occipital visual areas associated with visual perception, and increased activation in frontal and parietal regions associated with visual attention. These findings indicate that dyslexia involves atypical brain organization for fundamental processes of visual shape extraction even when reading is not involved. Overengagement in higher-order association cortices, required to compensate for underengagment in lower-order visual cortices, may result in competition for top-down attentional resources helpful for fluent reading.

  1. IgE epitope proximity determines immune complex shape and effector cell activation capacity

    Science.gov (United States)

    Gieras, Anna; Linhart, Birgit; Roux, Kenneth H.; Dutta, Moumita; Khodoun, Marat; Zafred, Domen; Cabauatan, Clarissa R.; Lupinek, Christian; Weber, Milena; Focke-Tejkl, Margarete; Keller, Walter; Finkelman, Fred D.; Valenta, Rudolf

    2016-01-01

    Background IgE-allergen complexes induce mast cell and basophil activation and thus immediate allergic inflammation. They are also important for IgE-facilitated allergen presentation to T cells by antigen-presenting cells. Objective To investigate whether the proximity of IgE binding sites on an allergen affects immune complex shape and subsequent effector cell activation in vitro and in vivo. Methods We constructed artificial allergens by grafting IgE epitopes in different numbers and proximity onto a scaffold protein. The shape of immune complexes formed between artificial allergens and the corresponding IgE was studied by negative-stain electron microscopy. Allergenic activity was determined using basophil activation assays. Mice were primed with IgE, followed by injection of artificial allergens to evaluate their in vivo allergenic activity. Severity of systemic anaphylaxis was measured by changes in body temperature. Results We could demonstrate simultaneous binding of 4 IgE antibodies in close vicinity to each other. The proximity of IgE binding sites on allergens influenced the shape of the resulting immune complexes and the magnitude of effector cell activation and in vivo inflammation. Conclusions Our results demonstrate that the proximity of IgE epitopes on an allergen affects its allergenic activity. We thus identified a novel mechanism by which IgE-allergen complexes regulate allergic inflammation. This mechanism should be important for allergy and other immune complex–mediated diseases. PMID:26684291

  2. Deep Neural Networks as a Computational Model for Human Shape Sensitivity

    Science.gov (United States)

    Op de Beeck, Hans P.

    2016-01-01

    Theories of object recognition agree that shape is of primordial importance, but there is no consensus about how shape might be represented, and so far attempts to implement a model of shape perception that would work with realistic stimuli have largely failed. Recent studies suggest that state-of-the-art convolutional ‘deep’ neural networks (DNNs) capture important aspects of human object perception. We hypothesized that these successes might be partially related to a human-like representation of object shape. Here we demonstrate that sensitivity for shape features, characteristic to human and primate vision, emerges in DNNs when trained for generic object recognition from natural photographs. We show that these models explain human shape judgments for several benchmark behavioral and neural stimulus sets on which earlier models mostly failed. In particular, although never explicitly trained for such stimuli, DNNs develop acute sensitivity to minute variations in shape and to non-accidental properties that have long been implicated to form the basis for object recognition. Even more strikingly, when tested with a challenging stimulus set in which shape and category membership are dissociated, the most complex model architectures capture human shape sensitivity as well as some aspects of the category structure that emerges from human judgments. As a whole, these results indicate that convolutional neural networks not only learn physically correct representations of object categories but also develop perceptually accurate representational spaces of shapes. An even more complete model of human object representations might be in sight by training deep architectures for multiple tasks, which is so characteristic in human development. PMID:27124699

  3. Deep Neural Networks as a Computational Model for Human Shape Sensitivity.

    Directory of Open Access Journals (Sweden)

    Jonas Kubilius

    2016-04-01

    Full Text Available Theories of object recognition agree that shape is of primordial importance, but there is no consensus about how shape might be represented, and so far attempts to implement a model of shape perception that would work with realistic stimuli have largely failed. Recent studies suggest that state-of-the-art convolutional 'deep' neural networks (DNNs capture important aspects of human object perception. We hypothesized that these successes might be partially related to a human-like representation of object shape. Here we demonstrate that sensitivity for shape features, characteristic to human and primate vision, emerges in DNNs when trained for generic object recognition from natural photographs. We show that these models explain human shape judgments for several benchmark behavioral and neural stimulus sets on which earlier models mostly failed. In particular, although never explicitly trained for such stimuli, DNNs develop acute sensitivity to minute variations in shape and to non-accidental properties that have long been implicated to form the basis for object recognition. Even more strikingly, when tested with a challenging stimulus set in which shape and category membership are dissociated, the most complex model architectures capture human shape sensitivity as well as some aspects of the category structure that emerges from human judgments. As a whole, these results indicate that convolutional neural networks not only learn physically correct representations of object categories but also develop perceptually accurate representational spaces of shapes. An even more complete model of human object representations might be in sight by training deep architectures for multiple tasks, which is so characteristic in human development.

  4. Investigation on penetration model of shaped charge jet in water

    Science.gov (United States)

    Shi, Jinwei; Luo, Xingbai; Li, Jinming; Jiang, Jianwei

    2016-01-01

    To analyze the process of jet penetration in water medium quantitatively, the properties of jet penetration spaced target with water interlayer were studied through test and numerical simulation. Two theoretical models of jet penetration in water were proposed. The theoretical model 1 was established considering the impact of the shock wave, combined with the shock equation Rankine-Hugoniot and the virtual origin calculation method. The theoretical model 2 was obtained by fitting theoretical analysis and numerical simulation results. The effectiveness and universality of the two theoretical models were compared through the numerical simulation results. Both the models can reflect the relationship between the penetration velocity and the penetration distance in water well, and both the deviation and stability of theoretical model 1 are better than 2, the lower penetration velocity, and the larger deviation of the theoretical model 2. Therefore, the theoretical model 1 can reflect the properties of jet penetration in water effectively, and provide the reference of model simulation and theoretical research.

  5. Shape: A 3D Modeling Tool for Astrophysics.

    Science.gov (United States)

    Steffen, Wolfgang; Koning, Nicholas; Wenger, Stephan; Morisset, Christophe; Magnor, Marcus

    2011-04-01

    We present a flexible interactive 3D morpho-kinematical modeling application for astrophysics. Compared to other systems, our application reduces the restrictions on the physical assumptions, data type, and amount that is required for a reconstruction of an object's morphology. It is one of the first publicly available tools to apply interactive graphics to astrophysical modeling. The tool allows astrophysicists to provide a priori knowledge about the object by interactively defining 3D structural elements. By direct comparison of model prediction with observational data, model parameters can then be automatically optimized to fit the observation. The tool has already been successfully used in a number of astrophysical research projects.

  6. Influence of metal nanoparticle decorated CNTs on polyurethane based electro active shape memory nanocomposite actuators

    International Nuclear Information System (INIS)

    Highlights: → Polyurethane based on pristine and metal (Ag and Cu) nanoparticle decorated CNTs nanocomposites are prepared through melt blending process. → The electrical, mechanical, dynamic mechanical, thermal conductivity and electro active shape memory properties of the PU nanocomposites were investigated. → The influence of metal nanoparticle decorated CNTs showed significant improvement in their all properties to compare to pristine CNTs. → Electro active shape memory studies of the PU/M-CNTs nanocomposites reveal extraordinary recoverability of its shape at lower applied dc voltages. - Abstract: Polymer nanocomposites based on thermoplastic polyurethane (PU) elastomer and metal nanoparticle (Ag and Cu) decorated multiwall carbon nanotubes (M-CNTs) were prepared through melt mixing process and investigated for its mechanical, dynamic mechanical and electro active shape memory properties. Structural characterization and morphological characterization of the PU nanocomposites were done using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Morphological characterization revealed better dispersion of M-CNTs in the polyurethane, which is attributed to the improved interaction between the M-CNTs and polyurethane. Loading of the metal nanoparticle coated carbon nanotubes resulted in the significant improvement on the mechanical properties such as tensile strength of the PU composites in comparison to the pristine carbon nanotubes (P-CNTs). Dynamic mechanical analysis showed that the glass transition temperature (Tg) of the polyurethane increases slightly with increasing loading of both pristine and metal nanoparticle functionalized carbon nanotubes. The metal nanoparticles decorated carbon nanotubes also showed significant improvement in the thermal and electrical conductivity of the PU/M-CNTs nanocomposites. Shape memory studies of the PU/M-CNTs nanocomposites exhibit remarkable recoverability of its shape at lower applied dc voltages.

  7. The Influence of Particle Shape and Size on the Activity of Platinum Nanoparticles for Oxygen Reduction Reaction: A Density Functional Theory Study

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Cerri, Isotta; Bligaard, Thomas;

    2014-01-01

    We present first principle investigation of the influence of platinum nanoparticle shape and size on the oxygen reduction reaction activity. We compare the activities of nanoparticles with specific shapes (tetrahedron, octahedron, cube and truncated octahedron) with that of equilibrium particle...... by explicitly taking the coverage of oxygenated species into account. A kinetic model derived from counting the number of sites shows that the theoretical activity obtained for equilibrium particle fits well with experimental data. Particles with similar to 3 nm diameter are found to possess the highest...... activity....

  8. Towards Low-Cost Effective and Homogeneous Thermal Activation of Shape Memory Polymers

    Directory of Open Access Journals (Sweden)

    Andrés Díaz Lantada

    2013-11-01

    Full Text Available A typical limitation of intelligent devices based on the use of shape-memory polymers as actuators is linked to the widespread use of distributed heating resistors, via Joule effect, as activation method, which involves several relevant issues needing attention, such as: (a Final device size is importantly increased due to the additional space required for the resistances; (b the use of resistances limits materials’ strength and the obtained devices are normally weaker; (c the activation process through heating resistances is not homogeneous, thus leading to important temperature differences among the polymeric structure and to undesirable thermal gradients and stresses, also limiting the application fields of shape-memory polymers. In our present work we describe interesting activation alternatives, based on coating shape-memory polymers with different kinds of conductive materials, including textiles, conductive threads and conductive paint, which stand out for their easy, rapid and very cheap implementation. Distributed heating and homogeneous activation can be achieved in several of the alternatives studied and the technical results are comparable to those obtained by using advanced shape-memory nanocomposites, which have to deal with complex synthesis, processing and security aspects. Different combinations of shape memory epoxy resin with several coating electrotextiles, conductive films and paints are prepared, simulated with the help of thermal finite element method based resources and characterized using infrared thermography for validating the simulations and overall design process. A final application linked to an active catheter pincer is detailed and the advantages of using distributed heating instead of conventional resistors are discussed.

  9. 4D Shape-Preserving Modelling of Bone Growth

    DEFF Research Database (Denmark)

    Andresen, Per Rønsholt; Nielsen, Mads; Kreiborg, Sven

    1998-01-01

    subdivide the growth analysis into growth simulation, growth modelling, and finally the growth analysis. In this paper, we present results of growth simulation of the mandible from 3 scannings of the same patient in the age of 9 months, 21 months, and 7 years. We also present the first growth models and...

  10. 3D Shape Modeling Using High Level Descriptors

    DEFF Research Database (Denmark)

    Andersen, Vedrana

    The goal of this Ph.D. project is to investigate and improve the methods for describing the surface of 3D objects, with focus on modeling geometric texture on surfaces. Surface modeling being a large field of research, the work done during this project concentrated around a few smaller areas...

  11. Emergent Structures in an Active Polar Fluid : dynamics of shape, scattering and merger

    CERN Document Server

    Husain, Kabir

    2016-01-01

    Spatially localised defect structures emerge spontaneously in a hydrodynamic description of an active polar fluid comprising polar 'actin' filaments and 'myosin' motor proteins that (un)bind to filaments and exert active contractile stresses. These emergent defect structures are characterized by distinct textures and can be either static or mobile - we derive effective equations of motion for these 'extended particles' and analyse their shape, kinetics, interactions and scattering. Depending on the impact parameter and propulsion speed, these active defects undergo elastic scattering or merger. Our results are relevant for the dynamics of actomyosin-dense structures at the cell cortex, reconstituted actomyosin complexes and 2D active colloidal gels.

  12. One-dimensional shape memory alloy models for use with reinforced composite structures

    Science.gov (United States)

    Zak, A. J.; Cartmell, M. P.; Ostachowicz, W. M.; Wiercigroch, M.

    2003-06-01

    In this paper three models of the shape memory alloy behaviour have been presented and re-investigated. The models are attributed to Tanaka, Liang and Rogers, and Brinson, and have been used extensively in the literature for studying the static or dynamic performance of different composite material structures with embedded shape memory alloy components. The major differences and similarities between these models have been emphasised and examined in the paper. A simple experimental rig was designed and manufactured to gain additional insight into the main mechanics governing the shape memory alloy (SMA) mechanical properties. Data obtained from the experimental measurements on Ni-Ti wires have been used in the numerical simulation for validation purposes. It has been found that the three models all agree well in their predictions of the superelastic behaviour at higher temperatures, above the austenite finish temperature when shape memory alloys stay in the fully austenitic phase. However, at low temperatures, when the alloys stay in the fully martensitic phase, some difficulties may be encountered. The model developed by Brinson introduces two new state variables and therefore two different mechanisms for the instigation of stress-induced and temperature-induced martensite. This enables more accurate predictions of the superelastic behaviour. In general, it can be recommended that for investigations of the shape memory and superelastic behaviour of shape memory alloy components the Brinson model, or refinements based on the Brinson model, should be applied.

  13. The generation and use of numerical shape models for irregular Solar System objects

    Science.gov (United States)

    Simonelli, Damon P.; Thomas, Peter C.; Carcich, Brian T.; Veverka, Joseph

    1993-01-01

    We describe a procedure that allows the efficient generation of numerical shape models for irregular Solar System objects, where a numerical model is simply a table of evenly spaced body-centered latitudes and longitudes and their associated radii. This modeling technique uses a combination of data from limbs, terminators, and control points, and produces shape models that have some important advantages over analytical shape models. Accurate numerical shape models make it feasible to study irregular objects with a wide range of standard scientific analysis techniques. These applications include the determination of moments of inertia and surface gravity, the mapping of surface locations and structural orientations, photometric measurement and analysis, the reprojection and mosaicking of digital images, and the generation of albedo maps. The capabilities of our modeling procedure are illustrated through the development of an accurate numerical shape model for Phobos and the production of a global, high-resolution, high-pass-filtered digital image mosaic of this Martian moon. Other irregular objects that have been modeled, or are being modeled, include the asteroid Gaspra and the satellites Deimos, Amalthea, Epimetheus, Janus, Hyperion, and Proteus.

  14. A dynamic spar numerical model for passive shape change

    Science.gov (United States)

    Calogero, J. P.; Frecker, M. I.; Hasnain, Z.; Hubbard, J. E., Jr.

    2016-10-01

    A three-dimensional constraint-driven dynamic rigid-link numerical model of a flapping wing structure with compliant joints (CJs) called the dynamic spar numerical model is introduced and implemented. CJs are modeled as spherical joints with distributed mass and spring-dampers with coupled nonlinear spring and damping coefficients, which models compliant mechanisms spatially distributed in the structure while greatly reducing computation time compared to a finite element model. The constraints are established, followed by the formulation of a state model used in conjunction with a forward time integrator, an experiment to verify a rigid-link assumption and determine a flapping angle function, and finally several example runs. Modeling the CJs as coupled bi-linear springs shows the wing is able to flex more during upstroke than downstroke. Coupling the spring stiffnesses allows an angular deformation about one axis to induce an angular deformation about another axis, where the magnitude is proportional to the coupling term. Modeling both the leading edge and diagonal spars shows that the diagonal spar changes the kinematics of the leading edge spar verses only considering the leading edge spar, causing much larger axial rotations in the leading edge spar. The kinematics are very sensitive to CJ location, where moving the CJ toward the wing root causes a stronger response, and adding multiple CJs on the leading edge spar with a CJ on the diagonal spar allows the wing to deform with larger magnitude in all directions. This model lays a framework for a tool which can be used to understand flapping wing flight.

  15. Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

    OpenAIRE

    Guan Rong; Guang Liu; Di Hou; Chuang-bing Zhou

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock sa...

  16. New Approaches For Asteroid Spin State and Shape Modeling From Delay-Doppler Radar Images

    Science.gov (United States)

    Raissi, Chedy; Lamee, Mehdi; Mosiane, Olorato; Vassallo, Corinne; Busch, Michael W.; Greenberg, Adam; Benner, Lance A. M.; Naidu, Shantanu P.; Duong, Nicholas

    2016-10-01

    Delay-Doppler radar imaging is a powerful technique to characterize the trajectories, shapes, and spin states of near-Earth asteroids; and has yielded detailed models of dozens of objects. Reconstructing objects' shapes and spins from delay-Doppler data is a computationally intensive inversion problem. Since the 1990s, delay-Doppler data has been analyzed using the SHAPE software. SHAPE performs sequential single-parameter fitting, and requires considerable computer runtime and human intervention (Hudson 1993, Magri et al. 2007). Recently, multiple-parameter fitting algorithms have been shown to more efficiently invert delay-Doppler datasets (Greenberg & Margot 2015) – decreasing runtime while improving accuracy. However, extensive human oversight of the shape modeling process is still required. We have explored two new techniques to better automate delay-Doppler shape modeling: Bayesian optimization and a machine-learning neural network.One of the most time-intensive steps of the shape modeling process is to perform a grid search to constrain the target's spin state. We have implemented a Bayesian optimization routine that uses SHAPE to autonomously search the space of spin-state parameters. To test the efficacy of this technique, we compared it to results with human-guided SHAPE for asteroids 1992 UY4, 2000 RS11, and 2008 EV5. Bayesian optimization yielded similar spin state constraints within a factor of 3 less computer runtime.The shape modeling process could be further accelerated using a deep neural network to replace iterative fitting. We have implemented a neural network with a variational autoencoder (VAE), using a subset of known asteroid shapes and a large set of synthetic radar images as inputs to train the network. Conditioning the VAE in this manner allows the user to give the network a set of radar images and get a 3D shape model as an output. Additional development will be required to train a network to reliably render shapes from delay

  17. Novel active comb-shaped dry electrode for EEG measurement in hairy site.

    Science.gov (United States)

    Huang, Yan-Jun; Wu, Chung-Yu; Wong, Alice May-Kuen; Lin, Bor-Shyh

    2015-01-01

    Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode.

  18. Turning a random laser into a tunable singlemode laser by active pump shaping

    CERN Document Server

    Bachelard, N; Noblin, X; Sebbah, P

    2013-01-01

    A laser is not necessarily a sophisticated device: Pumping energy into an amplifying medium randomly filled with scatterers, a powder for instance, makes a perfect "random laser." In such a laser, the absence of mirrors greatly simplifies laser design, but control over emission directionality or frequency tunability is lost, seriously hindering prospects for this otherwise simple laser. We recently proposed a novel approach to harness random lasers, inspired by spatial shaping methods recently employed for coherent light control in complex media. Here, we experimentally implement this method in an optofluidic random laser where modes are spatially extended and therefore strongly overlap, making individual selection a priori impossible. We show that control over the random laser emission can indeed be regained by actively shaping the spatial profile of the optical pump. This unique degree of freedom, which has never been really exploited, allows us to select any desired wavelength and shaping of lasing modes, ...

  19. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    Energy Technology Data Exchange (ETDEWEB)

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  20. Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent

    Directory of Open Access Journals (Sweden)

    Matthews Dennis L

    2007-11-01

    Full Text Available Abstract Background Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel. Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. Methods A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. Results At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W. Conclusion We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  1. Sparse Principal Component Analysis in Medical Shape Modeling

    DEFF Research Database (Denmark)

    Sjöstrand, Karl; Stegmann, Mikkel Bille; Larsen, Rasmus

    2006-01-01

    Principal component analysis (PCA) is a widely used tool in medical image analysis for data reduction, model building, and data understanding and exploration. While PCA is a holistic approach where each new variable is a linear combination of all original variables, sparse PCA (SPCA) aims...

  2. Industrial forging applications of shaping simulation using modeling clay

    Science.gov (United States)

    Ravassard, P.; Bournicon, C.

    1982-09-01

    The use of Plasticine and similar modeling materials to simulate forgings is advocated. It permits low cost studies of complex processes for manufacturing or training purposes without interfering with work schedules of real machines. Criteria for choosing a clay, construction of dies, equipment, and laboratory procedures are described.

  3. Biosynthesis and recovery of rod-shaped tellurium nanoparticles and their bactericidal activities

    Energy Technology Data Exchange (ETDEWEB)

    Zare, Bijan; Faramarzi, Mohammad Ali; Sepehrizadeh, Zargham [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, P.O. Box 14155-6451 Tehran (Iran, Islamic Republic of); Shakibaie, Mojtaba [Department of Pharmacognosy and Biotechnology, School of Pharmacy, Pharmaceutics Research Center, Kerman University of Medical Sciences, P.O. Box 76175-493 Kerman (Iran, Islamic Republic of); Rezaie, Sassan [Department of Medical Biotechnology, School of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Shahverdi, Ahmad Reza, E-mail: shahverd@sina.tums.ac.ir [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, P.O. Box 14155-6451 Tehran (Iran, Islamic Republic of)

    2012-11-15

    Highlights: ► Biosynthesis of rod shape tellurium nanoparticles with a hexagonal crystal structure. ► Extraction procedure for isolation of tellurium nanoparticles from Bacillus sp. BZ. ► Extracted tellurium nanoparticles have good bactericidal activity against some bacteria. -- Abstract: In this study, a tellurium-transforming Bacillus sp. BZ was isolated from the Caspian Sea in northern Iran. The isolate was identified by various tests and 16S rDNA analysis, and then used to prepare elemental tellurium nanoparticles. The isolate was subsequently used for the intracellular biosynthesis of elemental tellurium nanoparticles. The biogenic nanoparticles were released by liquid nitrogen and purified by an n-octyl alcohol water extraction system. The shape, size, and composition of the extracted nanoparticles were characterized. The transmission electron micrograph showed rod-shaped nanoparticles with dimensions of about 20 nm × 180 nm. The energy dispersive X-ray and X-ray diffraction spectra respectively demonstrated that the extracted nanoparticles consisted of only tellurium and have a hexagonal crystal structure. This is the first study to demonstrate a biological method for synthesizing rod-shaped elemental tellurium by a Bacillus sp., its extraction and its antibacterial activity against different clinical isolates.

  4. 3D segmentation of rodent brain structures using hierarchical shape priors and deformable models.

    Science.gov (United States)

    Zhang, Shaoting; Huang, Junzhou; Uzunbas, Mustafa; Shen, Tian; Delis, Foteini; Huang, Xiaolei; Volkow, Nora; Thanos, Panayotis; Metaxas, Dimitris N

    2011-01-01

    In this paper, we propose a method to segment multiple rodent brain structures simultaneously. This method combines deformable models and hierarchical shape priors within one framework. The deformation module employs both gradient and appearance information to generate image forces to deform the shape. The shape prior module uses Principal Component Analysis to hierarchically model the multiple structures at both global and local levels. At the global level, the statistics of relative positions among different structures are modeled. At the local level, the shape statistics within each structure is learned from training samples. Our segmentation method adaptively employs both priors to constrain the intermediate deformation result. This prior constraint improves the robustness of the model and benefits the segmentation accuracy. Another merit of our prior module is that the size of the training data can be small, because the shape prior module models each structure individually and combines them using global statistics. This scheme can preserve shape details better than directly applying PCA on all structures. We use this method to segment rodent brain structures, such as the cerebellum, the left and right striatum, and the left and right hippocampus. The experiments show that our method works effectively and this hierarchical prior improves the segmentation performance. PMID:22003750

  5. Method of Modeling and Simulation of Shaped External Occulters

    Science.gov (United States)

    Lyon, Richard G. (Inventor); Clampin, Mark (Inventor); Petrone, Peter, III (Inventor)

    2016-01-01

    The present invention relates to modeling an external occulter including: providing at least one processor executing program code to implement a simulation system, the program code including: providing an external occulter having a plurality of petals, the occulter being coupled to a telescope; and propagating light from the occulter to a telescope aperture of the telescope by scalar Fresnel propagation, by: obtaining an incident field strength at a predetermined wavelength at an occulter surface; obtaining a field propagation from the occulter to the telescope aperture using a Fresnel integral; modeling a celestial object at differing field angles by shifting a location of a shadow cast by the occulter on the telescope aperture; calculating an intensity of the occulter shadow on the telescope aperture; and applying a telescope aperture mask to a field of the occulter shadow, and propagating the light to a focal plane of the telescope via FFT techniques.

  6. Modeling Latency and Shape Changes in Trial Based Neuroimaging Data

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai; Madsen, Kristoffer Hougaard

    2011-01-01

    To overcome poor signal-to-noise ratios in neuroimaging, data sets are often acquired over repeated trials that form a three-way array of spacetimetrials. As neuroimaging data contain multiple inter-mixed signal components blind signal separation and decomposition methods are frequently invoked...... for exploratory analysis and as a preprocessing step for signal detection. Most previous component analyses have avoided working directly with the tri-linear structure, but resorted to bi-linear models such as ICA, PCA, and NMF. Multi-linear decomposition can exploit consistency over trials and contrary to bi......-linear decomposition render unique representations without additional constraints. However, they can degenerate if data does not comply with the given multi-linear structure, e.g., due to time-delays. Here we extend multi-linear decomposition to account for general temporal modeling within a convolutional...

  7. Deformation of the UI-14at%Nb shape memory alloy: experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Field, Robert D [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Mc Cabe, Rodney J [Los Alamos National Laboratory; Clarke, Amy J [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tupper, Catherine N [Los Alamos National Laboratory

    2010-12-22

    U-14at%Nb is a shape memory effect (SME) alloy that undergoes deformation by the motion of complex twins and twin related lath boundaries up to the limit of SME deformation ({approx}7%). All of the twins present in the as-transformed martensite and active during SME deformation are derived from those of the orthorhombic alpha-U phase, modified for the monoclinic distortion of the alpha martensite phase. In the SME regime a simple Bain strain model qualitatively predicts variant selection, texture development in polycrystalline samples, and stress-strain behavior as a function of parent phase orientation in single crystal micropillars. In the post-SME regime, unrecoverable deformation occurs by a combination of slip and twinning, with the first few percent of strain in tension apparently governed by a twin species specifically associated with the monoclinic distortion (i.e. not present in the orthorhombic alpha-U phase). The situation in compression is more complicated, with a combination of slip and twinning systems believed responsible for deformation. A review of the Bain strain model for SME deformation will be presented in conjunction with experimental data. In addition, results from modeling of post-SME behavior using the Visco-Plastic Self-Consistent (VPSC) model will be compared to experimental texture measurements.

  8. Variable Camber Continuous Aerodynamic Control Surfaces and Methods for Active Wing Shaping Control

    Science.gov (United States)

    Nguyen, Nhan T. (Inventor)

    2016-01-01

    An aerodynamic control apparatus for an air vehicle improves various aerodynamic performance metrics by employing multiple spanwise flap segments that jointly form a continuous or a piecewise continuous trailing edge to minimize drag induced by lift or vortices. At least one of the multiple spanwise flap segments includes a variable camber flap subsystem having multiple chordwise flap segments that may be independently actuated. Some embodiments also employ a continuous leading edge slat system that includes multiple spanwise slat segments, each of which has one or more chordwise slat segment. A method and an apparatus for implementing active control of a wing shape are also described and include the determination of desired lift distribution to determine the improved aerodynamic deflection of the wings. Flap deflections are determined and control signals are generated to actively control the wing shape to approximate the desired deflection.

  9. Deep Learning Guided Partitioned Shape Model for Anterior Visual Pathway Segmentation.

    Science.gov (United States)

    Mansoor, Awais; Cerrolaza, Juan J; Idrees, Rabia; Biggs, Elijah; Alsharid, Mohammad A; Avery, Robert A; Linguraru, Marius George

    2016-08-01

    Analysis of cranial nerve systems, such as the anterior visual pathway (AVP), from MRI sequences is challenging due to their thin long architecture, structural variations along the path, and low contrast with adjacent anatomic structures. Segmentation of a pathologic AVP (e.g., with low-grade gliomas) poses additional challenges. In this work, we propose a fully automated partitioned shape model segmentation mechanism for AVP steered by multiple MRI sequences and deep learning features. Employing deep learning feature representation, this framework presents a joint partitioned statistical shape model able to deal with healthy and pathological AVP. The deep learning assistance is particularly useful in the poor contrast regions, such as optic tracts and pathological areas. Our main contributions are: 1) a fast and robust shape localization method using conditional space deep learning, 2) a volumetric multiscale curvelet transform-based intensity normalization method for robust statistical model, and 3) optimally partitioned statistical shape and appearance models based on regional shape variations for greater local flexibility. Our method was evaluated on MRI sequences obtained from 165 pediatric subjects. A mean Dice similarity coefficient of 0.779 was obtained for the segmentation of the entire AVP (optic nerve only =0.791 ) using the leave-one-out validation. Results demonstrated that the proposed localized shape and sparse appearance-based learning approach significantly outperforms current state-of-the-art segmentation approaches and is as robust as the manual segmentation.

  10. An Internal Heating Model to Elucidate the Shape of a Small Planetary Body

    Institute of Scientific and Technical Information of China (English)

    LI Gen; CHEN Chu-Xin

    2012-01-01

    Small planetary bodies usually have irregular shapes.If they are large enough to be heated to a partial melting status,the deforming force of gravity could overcome the internal forces and make the shape transfigure from potato-like to spherical.We have developed a model to calculate the thermal history of a planetoid and apply the model to asteroids,since ample evidence has shown that many asteroids could have undergone differentiation.After revealing the relation between the shape and the ratio of the melt part,we also examine the surface roughness of these asteroids and suggest that 280km would be a critical radius for an asteroid to develop a virtually globular contour.%Small planetary bodies usually have irregular shapes. If they are large enough to be heated to a partial melting status, the deforming force of gravity could overcome the internal forces and make the shape transfigure from potato-like to spherical. We have developed a model to calculate the thermal history of a planetoid and apply the model to asteroids, since ample evidence has shown that many asteroids could have undergone differentiation. After revealing the relation between the shape and the ratio of the melt part, we also examine the surface roughness of these asteroids and suggest that 280 km would be a critical radius for an asteroid to develop a virtually globular contour.

  11. Deep Learning Guided Partitioned Shape Model for Anterior Visual Pathway Segmentation.

    Science.gov (United States)

    Mansoor, Awais; Cerrolaza, Juan J; Idrees, Rabia; Biggs, Elijah; Alsharid, Mohammad A; Avery, Robert A; Linguraru, Marius George

    2016-08-01

    Analysis of cranial nerve systems, such as the anterior visual pathway (AVP), from MRI sequences is challenging due to their thin long architecture, structural variations along the path, and low contrast with adjacent anatomic structures. Segmentation of a pathologic AVP (e.g., with low-grade gliomas) poses additional challenges. In this work, we propose a fully automated partitioned shape model segmentation mechanism for AVP steered by multiple MRI sequences and deep learning features. Employing deep learning feature representation, this framework presents a joint partitioned statistical shape model able to deal with healthy and pathological AVP. The deep learning assistance is particularly useful in the poor contrast regions, such as optic tracts and pathological areas. Our main contributions are: 1) a fast and robust shape localization method using conditional space deep learning, 2) a volumetric multiscale curvelet transform-based intensity normalization method for robust statistical model, and 3) optimally partitioned statistical shape and appearance models based on regional shape variations for greater local flexibility. Our method was evaluated on MRI sequences obtained from 165 pediatric subjects. A mean Dice similarity coefficient of 0.779 was obtained for the segmentation of the entire AVP (optic nerve only =0.791 ) using the leave-one-out validation. Results demonstrated that the proposed localized shape and sparse appearance-based learning approach significantly outperforms current state-of-the-art segmentation approaches and is as robust as the manual segmentation. PMID:26930677

  12. Manual activity shapes structure and function in contralateral human motor hand area

    DEFF Research Database (Denmark)

    Granert, Oliver; Peller, Martin; Gaser, Christian;

    2011-01-01

    From longitudinal voxel-based morphometry (VBM) studies we know that relatively short periods of training can increase regional grey matter volume in trained cortical areas. In 14 right-handed patients with writer's cramp, we employed VBM to test whether suppression (i.e., immobilization) or enha......1(HAND) is dynamically shaped by the level of manual activity. This bi-directional structural plasticity is functionally relevant as local grey matter changes are mirrored by changes in regional excitability....

  13. Hysteresis Modeling of Magnetic Shape Memory Alloy Actuator Based on Krasnosel'skii-Pokrovskii Model

    Directory of Open Access Journals (Sweden)

    Miaolei Zhou

    2013-01-01

    Full Text Available As a new type of intelligent material, magnetically shape memory alloy (MSMA has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.

  14. A thermo dynamical model for the shape and size effect on melting of boron carbide nanoparticles.

    Science.gov (United States)

    Antoniammal, Paneerselvam; Arivuoli, Dakshanamoorthy

    2012-02-01

    The size and shape dependence of the melting temperature of Boron Carbide (B4C) nanoparticles has been investigated with a numerical thermo dynamical approach. The problem considered in this paper is the inward melting of nanoparticles with spherical and cylindrical geometry. The cylindrical Boron Carbide (B4C) nanoparticles, whose melting point has been reported to decrease with decreasing particle radius, become larger than spherical shaped nanoparticle. Comparative investigation of the size dependence of the melting temperature with respect to the two shapes is also been done. The melting temperature obtained in the present study is approximately a dealing function of radius, in a good agreement with prediction of thermo dynamical model.

  15. Fine Extruding Deformation and Modeling Optimization of Die Cavityin Special-Shaped Products

    Institute of Scientific and Technical Information of China (English)

    Qi Hongyuan; Zhu Hengjun

    2004-01-01

    On the basis of Conformal Mapping theory, using approaches of numerical trigonometric interpolation and vector normal convergence, region function of three-dimension deforming, surface function of die cavity, and mapping function between the plastic flow model and the axis-symmetry model were set up respectively for fine extruding special-shaped products with different arc radius ri. Then the stream function and both fields of velocity and strain ratio are inferred for special-shaped plastic deformation; meanwhile, with the help of Upper-Bound principle, the parameter of die cavity gets optimized. Taking square-shaped and hexagon-shaped products with different arc radius ri as examples,the velocity field gets analyzed, the parameter of die cavity is optimized and the die cavity gets depicted as well. Consequently, above study provides theoretical support for achieving the technical goal of CAD/CAM integration in die cavity of fine extrusion.

  16. Evaluation of automated statistical shape model based knee kinematics from biplane fluoroscopy

    DEFF Research Database (Denmark)

    Baka, Nora; Kaptein, Bart L.; Giphart, J. Erik;

    2014-01-01

    State-of-the-art fluoroscopic knee kinematic analysis methods require the patient-specific bone shapes segmented from CT or MRI. Substituting the patient-specific bone shapes with personalizable models, such as statistical shape models (SSM), could eliminate the CT/MRI acquisitions, and thereby...... decrease costs and radiation dose (when eliminating CT). SSM based kinematics, however, have not yet been evaluated on clinically relevant joint motion parameters. Therefore, in this work the applicability of SSMs for computing knee kinematics from biplane fluoroscopic sequences was explored. Kinematic......-posterior tibial drawer, joint distraction-contraction, flexion, tibial rotation and adduction. The relationship between kinematic precision and bone shape accuracy was also investigated. The SSM based kinematics resulted in sub-millimeter (0.48-0.81mm) and approximately 1° (0.69-0.99°) median precision...

  17. Line shape modeling in warm and dense hydrogen plasmas

    Science.gov (United States)

    Ferri, S.; Calisti, A.; Mossé, C.; Talin, B.; Gigosos, M. A.; González, M. A.

    2007-05-01

    A study of hydrogen lines emitted in warm ( T˜1eV) and dense ( N≥1018cm -3) plasmas is presented. Under such plasma conditions, the electronic and the ionic contributions to the line width are comparable, and the general question related to a transition from impact to quasi-static broadening arises not only for the far wings but also for the core of spectral lines. The transition from impact to quasi-static broadening for electrons is analyzed by means of Frequency Fluctuation Model (FFM). In parallel, direct integration of the semi-classical evolution equation is performed using electron electric fields calculated by Molecular Dynamics (MD) simulations that permit one to correctly describe the emitter environment. New cross comparisons between benchmark MD simulations and FFM are carried out for electron broadening of the Balmer series lines, and, especially, for the Hα line, for which a few experiments in the warm and dense plasma regimes are available.

  18. Radar Shape Modeling Of (8567) 1996 HW1 Combined With Thermal Observations

    Science.gov (United States)

    Howell, Ellen S.; Magri, C.; Nolan, M. C.; Taylor, P. A.; Vervack, R. J., Jr.; Fernandez, Y. R.; Mueller, M.; Benner, L. A. M.; Giorgini, J. D.; Scheeres, D. J.; Hicks, M. D.; Rhoades, H.; Somers, J. M.; Gaftonyuk, N. M.; Krugly, Y. N.; Kouprianov, V. V.; Molotov, I. E.; Benishek, V.; Protitch-Benishek, V.; Galad, A.; Higgins, D.; Kusnirak, P.; Pray, D.

    2010-10-01

    We observed near-Earth asteroid (8567) 1996 HW1 at the Arecibo Observatory on six dates in September 2008, obtaining radar images and spectra. By combining these data with an extensive set of new lightcurves taken during 2008-2009 and with previously published lightcurves from 2005, we were able to reconstruct the object's shape and spin state. 1996 HW1 is an elongated, highly bifurcated object, and appears to be a contact binary. A convex shape model derived from the lightcurves alone produces a pole orientation that is consistent with the pole derived from the radar data. It is instructive to compare these two shape models. We have also obtained near-infrared spectra at the NASA IRTF using SpeX in both prism and LXD modes. The prism spectra show pyroxene and olivine bands. We obtained LXD spectra (2-4 microns) on 19 August, 1 September and 1 October 2008. Thermal modeling using the shape model and derived pole and rotation constrain the regolith properties. The radar shape model and results of the thermal modeling will be presented.

  19. 3D shape analysis of the brain's third ventricle using a midplane encoded symmetric template model

    OpenAIRE

    Kim, J; Valdes Hernandez, Maria; Royle, Natalie; Muñoz Maniega, Susana; Aribisala, Benjamin; Gow, Alan; Bastin, Mark; Deary, Ian; Wardlaw, Joanna; Park, J.

    2016-01-01

    BackgroundStructural changes of the brain's third ventricle have been acknowledged as an indicative measure of the brain atrophy progression in neurodegenerative and endocrinal diseases. To investigate the ventricular enlargement in relation to the atrophy of the surrounding structures, shape analysis is a promising approach. However, there are hurdles in modeling the third ventricle shape. First, it has topological variations across individuals due to the inter-thalamic adhesion. In addition...

  20. Building and Testing a Statistical Shape Model of the Human Ear Canal

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Larsen, Rasmus; Laugesen, Søren;

    2002-01-01

    Today the design of custom in-the-ear hearing aids is based on personal experience and skills and not on a systematic description of the variation of the shape of the ear canal. In this paper it is described how a dense surface point distribution model of the human ear canal is built based...... for gender related differences in size and shape of the ear canal....

  1. A SHAPE-NAVIGATED IMAGE DEFORMATION MODEL FOR 4D LUNG RESPIRATORY MOTION ESTIMATION

    OpenAIRE

    Liu, Xiaoxiao; Saboo, Rohit R.; Pizer, Stephen M.; Mageras, Gig S.

    2009-01-01

    Intensity modulated radiation therapy (IMRT) for cancers in the lung remains challenging due to the complicated respiratory dynamics. We propose a shape-navigated dense image deformation model to estimate the patient-specific breathing motion using 4D respiratory correlated CT (RCCT) images. The idea is to use the shape change of the lungs, the major motion feature in the thorax image, as a surrogate to predict the corresponding dense image deformation from training.

  2. Restructuring shapes in terms of emergent subshapes: a computational and cognitive model

    OpenAIRE

    Liu, Y.T.

    1996-01-01

    In order to interpret the current state of a design, designers possess the powerful, spontaneous ability to restructure shapes in terms of emergent subshapes. In this paper a theoretical model of restructuring shapes is presented, one that aims to recognize explicit and implicit emergent subshapes computationally and to explain cognitively some critical phenomena of designers' visual behaviors. A computing procedure using two neuron-like connectionist networks and two attentional techniques s...

  3. Automated Finite Element Modeling of Wing Structures for Shape Optimization

    Science.gov (United States)

    Harvey, Michael Stephen

    1993-01-01

    The displacement formulation of the finite element method is the most general and most widely used technique for structural analysis of airplane configurations. Modem structural synthesis techniques based on the finite element method have reached a certain maturity in recent years, and large airplane structures can now be optimized with respect to sizing type design variables for many load cases subject to a rich variety of constraints including stress, buckling, frequency, stiffness and aeroelastic constraints (Refs. 1-3). These structural synthesis capabilities use gradient based nonlinear programming techniques to search for improved designs. For these techniques to be practical a major improvement was required in computational cost of finite element analyses (needed repeatedly in the optimization process). Thus, associated with the progress in structural optimization, a new perspective of structural analysis has emerged, namely, structural analysis specialized for design optimization application, or.what is known as "design oriented structural analysis" (Ref. 4). This discipline includes approximation concepts and methods for obtaining behavior sensitivity information (Ref. 1), all needed to make the optimization of large structural systems (modeled by thousands of degrees of freedom and thousands of design variables) practical and cost effective.

  4. Finite element modeling of a progressively expanding shape memory stent.

    Science.gov (United States)

    Thériault, Philippe; Terriault, Patrick; Brailovski, Vladimir; Gallo, Richard

    2006-01-01

    Cardiovascular stents are small cylindrical devices introduced in stenosed arteries to reopen the lumen and restore blood flow. However, this treatment presents complications, including restenosis, which is the reclosing of the artery's diameter after the insertion of a stent. The structure of the prosthesis penetrates into and injures the walls of the patient's artery. There then follows a proliferation of cells and the formation of scar tissue around the injury, similar to the scarring of other organic tissues. This reaction to the trauma subjects the artery to close. The proposed solution is to develop a Nitinol stent with a progressive expansion device made of polyethylene, allowing smooth and gradual contact between the stent and the artery's wall by creep effect. The purpose of this paper is to describe the technology and methodology for the numerical study of this kind of stent through the finite element method. ANSYS 8.0 software is used to perform the analysis. The Nitinol is modeled with a superelastic law and the polyethylene with a yield hardening law. A first simulation determines the final geometry of the stent laser cut from a small tube. A second simulation examines the behavior of the prosthesis during surgery and over the 4 weeks following the operation. The results demonstrate that a compromise can be reached between a limited expansion prior the inflation of the expandable balloon and a significant expansion by creep of the polymer rings.

  5. Numerical simulation study on active and passive hydroforming process optimization of box shaped part

    Science.gov (United States)

    Zeng, Y. P.; Dong, J. L.; He, T. D.; Wang, B.

    2016-08-01

    Low qualified rate and inferior quality frequently occurring in the general deep drawing process of a certain box-shaped part, now use hydroforming to optimize forming process, in order to study the effect of hydroforming for improving the quality and formability, purposed five process schemes: general deep drawing, active hydroforming, passive hydroforming, general deep drawing combined with active hydroforming, passive combined with active hydroforming. Each process was simulated by finite element simulation and results were analysed. The results indicate the passive combined with active hydroforming is the best scheme which can obtain smallest thickness thinning and satisfactory formability, then optimized hydroforming pressure, blank holder force subsequently by adjust the simulation parameters. Research result proves that active/passive hydroforming is a new method for complex parts forming.

  6. Similar extrusion and mapping optimization of die cavity modeling for special-shaped products

    Institute of Scientific and Technical Information of China (English)

    QI Hong-yuan; WANG Shuang-xin; ZHU Heng-jun

    2006-01-01

    Aimed at the modeling issues in design and quick processing of extruding die for special-shaped products, with the help of Conformal Mapping theory, Conformal Mapping function is determined by the given method of numerical trigonometric interpolation. Three-dimensional forming problems are transformed into two-dimensional problems, and mathematical model of die cavity surface is established based on different kinds of vertical curve, as well as the mathematical model of plastic flow in extruding deformation of special-shaped products gets completed. By upper bound method, both vertical curves of die cavity and its parameters are optimized. Combining the optimized model with the latest NC technology, NC Program of die cavity and its CAM can be realized. Taking the similar extrusion of square-shaped products with arc radius as instance, both metal plastic similar extrusion and die cavity optimization are carried out.

  7. CELL TRACKING USING PARTICLE FILTERS WITH IMPLICIT CONVEX SHAPE MODEL IN 4D CONFOCAL MICROSCOPY IMAGES

    Science.gov (United States)

    Ramesh, Nisha; Tasdizen, Tolga

    2016-01-01

    Bayesian frameworks are commonly used in tracking algorithms. An important example is the particle filter, where a stochastic motion model describes the evolution of the state, and the observation model relates the noisy measurements to the state. Particle filters have been used to track the lineage of cells. Propagating the shape model of the cell through the particle filter is beneficial for tracking. We approximate arbitrary shapes of cells with a novel implicit convex function. The importance sampling step of the particle filter is defined using the cost associated with fitting our implicit convex shape model to the observations. Our technique is capable of tracking the lineage of cells for nonmitotic stages. We validate our algorithm by tracking the lineage of retinal and lens cells in zebrafish embryos. PMID:27403085

  8. Stability Analysis for Cellinoid Shape Model in Inverse Process from Lightcurves

    Science.gov (United States)

    Lu, Xiao-Ping; Ip, Wing-Huen; Song, Yun-Lin; Zhao, Hai-Bin

    2016-04-01

    Based on the special shape first introduced by Alberto Cellino, which consists of eight ellipsoidal octants with the constraint that adjacent octants must have two identical semi-axes, an efficient algorithm to derive the physical parameters, such as the rotational period, spin axis, and overall shape from either lightcurves or sparse photometric data of asteroids, is developed by Lu et al.[1]. They call this model 'Cellinoid' shape model. Numerical applications confirm that the cellinoid shape model could derive the best-fit rotational period for the asteroid from several lightcurves observed in one apparition. Furthermore by exploiting more lightcurves observed in various viewing circumstances, the derived spin axis could be refined [2]. Additionally the cellinoid shape model is applied to the sparse Hipparcos data with the average number of measurements being of the order of 70 per object, similar to the future catalog of the ongoing space project, Gaia [3]. The derived rotational periods from 70 sparse measurements are accurate and the spin axes are close to the known results, derived from lightcurves by other methods. With only 3 more parameters than the traditional triaxial ellipsoid, the cellinoid shape model of having the asymmetric morphology could perform efficiently and simulate the real asteroids better. That could be employed for the huge number of photometric sparse data observed by Gaia in the coming future. For thoroughly investigating the relationship between the morphology of the synthetic lightcurves generated by the cellinoid shape model and its six semi-axes, the numerical tests are implemented to compare the synthetic lightcurves generated by various cellinoid models. Furthermore, the sensitivity of the stable spin axis of cellinoid shape model with respect to its semi-axes is analyzed, too. These numerical tests provide important information for optimizing the aforementioned algorithm to search the physical parameters for asteroids based on

  9. Interactive Shape Modeling using a Skeleton-Mesh Co-Representation

    DEFF Research Database (Denmark)

    Bærentzen, Jacob Andreas; Abdrashitov, Rinat; Singh, Karan

    2014-01-01

    We introduce the Polar-Annular Mesh representation (PAM). A PAM is a mesh-skeleton co-representation designed for the modeling of 3D organic, articulated shapes. A PAM represents a manifold mesh as a partition of polar (triangle fans) and annular (rings of quads) regions. The skeletal topology...... a PAM to a quad-only mesh. We further present a PAM-based multi-touch sculpting application in order to demonstrate its utility as a shape representation for the interactive modeling of organic, articulated figures as well as for editing and posing of pre-existing models....

  10. Modeling fluid structure interaction with shape memory alloy actuated morphing aerostructures

    Science.gov (United States)

    Oehler, Stephen D.; Hartl, Darren J.; Turner, Travis L.; Lagoudas, Dimitris C.

    2012-04-01

    The development of efficient and accurate analysis techniques for morphing aerostructures incorporating shape memory alloys (SMAs) continues to garner attention. These active materials have a high actuation energy density, making them an ideal replacement for conventional actuation mechanisms in morphing structures. However, SMA components are often exposed to the same highly variable environments experienced by the aeroelastic assemblies into which they are incorporated. This is motivating design engineers to consider modeling fluidstructure interaction for prescribing dynamic, solution-dependent boundary conditions. This work presents a computational study of a particular morphing aerostructure with embedded, thermally actuating SMA ribbons and demonstrates the effective use of fluid-structure interaction modeling. A cosimulation analysis is utilized to determine the surface deflections and stress distributions of an example aerostructure with embedded SMA ribbons using the Abaqus Finite Element Analysis (FEA) software suite, combined with an Abaqus Computational Fluid Dynamics (CFD) processor. The global FEA solver utilizes a robust user-defined material subroutine which contains an accurate three-dimensional SMA constitutive model. Variations in the ambient fluid environment are computed using the CFD solver, and fluid pressure is mapped into surface distributed loads. Results from the analysis are qualitatively validated with independently obtained data from representative flow tests previously conducted on a physical prototype of the same aerostructure.

  11. Titanium-Nickel Shape Memory Alloy Spring Actuator for Forward-Looking Active Catheter

    OpenAIRE

    Shozo Inoue; Takahiro Miki; Takafumi Tsurui; Hiroyuki Nagasawa; Mamoru Komatsubara; Takahiro Namazu

    2011-01-01

    The fabrication and characterization of forward-looking active catheter actuated by titanium-nickel (Ti-Ni) shape memory alloy (SMA) springs are described. The catheter has been designed for wide-range observation of an affected area inside a blood vessel when the blood vessel is occluded. The developed active catheter consists of eight Ti-Ni SMA spring actuators for actuation of catheter tip, an ultrasonic transducer for forward-looking, a guide wire, a polyurethane tube for coating, and spi...

  12. Multistage Development of Müller-Achenbach model for Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Simin A. Oshkovr

    2008-01-01

    Full Text Available This research focused on the conceptual development of constitutive Müller-Achenbach model and proceeds to construct a model based on phase transition under changing temperature and load for variants of martensite in shape memory alloy CuAlNi (Copper-aluminum-nickel. Problem statement: Motivation of this research is rare information of a variant of martensite phase (M++ and prediction of the shape recovery of shape memory alloy in this stage of transformation. Approach: The mathematical equations proposed a prediction of stability of Austenite phases and extend it to multistage martensitic phase transformation. These phase transformations occurred by loading on the material. Equations described free energy landscape in CuAlNi shape memory alloys at low (260K and high temperature (440K. The model evaluated the free energy due to the phase transformation between the austenite and multistage martensitic structures. Results: Results for M++ phase showed decrease in temperature from 440K to 260K presented decrease in stress approximately from 1 kN to 0.4kN and free energy from 5 kJ/kg to 0.1 kJ/kg. Equations have been solved and plotted by software programmed in MATLAB. Conclusions/Recommendations: The model which has derived focused on homogeneous shape memory alloys, but future performance requirements will most likely be met with heterogeneous materials. Therefore, simulation models for heterogeneous materials must be developed.

  13. Effect of ocular shape and vascular geometry on retinal hemodynamics: a computational model.

    Science.gov (United States)

    Dziubek, Andrea; Guidoboni, Giovanna; Harris, Alon; Hirani, Anil N; Rusjan, Edmond; Thistleton, William

    2016-08-01

    A computational model for retinal hemodynamics accounting for ocular curvature is presented. The model combines (i) a hierarchical Darcy model for the flow through small arterioles, capillaries and small venules in the retinal tissue, where blood vessels of different size are comprised in different hierarchical levels of a porous medium; and (ii) a one-dimensional network model for the blood flow through retinal arterioles and venules of larger size. The non-planar ocular shape is included by (i) defining the hierarchical Darcy flow model on a two-dimensional curved surface embedded in the three-dimensional space; and (ii) mapping the simplified one-dimensional network model onto the curved surface. The model is solved numerically using a finite element method in which spatial domain and hierarchical levels are discretized separately. For the finite element method, we use an exterior calculus-based implementation which permits an easier treatment of non-planar domains. Numerical solutions are verified against suitably constructed analytical solutions. Numerical experiments are performed to investigate how retinal hemodynamics is influenced by the ocular shape (sphere, oblate spheroid, prolate spheroid and barrel are compared) and vascular architecture (four vascular arcs and a branching vascular tree are compared). The model predictions show that changes in ocular shape induce non-uniform alterations of blood pressure and velocity in the retina. In particular, we found that (i) the temporal region is affected the least by changes in ocular shape, and (ii) the barrel shape departs the most from the hemispherical reference geometry in terms of associated pressure and velocity distributions in the retinal microvasculature. These results support the clinical hypothesis that alterations in ocular shape, such as those occurring in myopic eyes, might be associated with pathological alterations in retinal hemodynamics. PMID:26445874

  14. 3D shape analysis of the brain's third ventricle using a midplane encoded symmetric template model

    Science.gov (United States)

    Kim, Jaeil; Valdés Hernández, Maria del C.; Royle, Natalie A.; Maniega, Susana Muñoz; Aribisala, Benjamin S.; Gow, Alan J.; Bastin, Mark E.; Deary, Ian J.; Wardlaw, Joanna M.; Park, Jinah

    2016-01-01

    Background Structural changes of the brain's third ventricle have been acknowledged as an indicative measure of the brain atrophy progression in neurodegenerative and endocrinal diseases. To investigate the ventricular enlargement in relation to the atrophy of the surrounding structures, shape analysis is a promising approach. However, there are hurdles in modeling the third ventricle shape. First, it has topological variations across individuals due to the inter-thalamic adhesion. In addition, as an interhemispheric structure, it needs to be aligned to the midsagittal plane to assess its asymmetric and regional deformation. Method To address these issues, we propose a model-based shape assessment. Our template model of the third ventricle consists of a midplane and a symmetric mesh of generic shape. By mapping the template's midplane to the individuals’ brain midsagittal plane, we align the symmetric mesh on the midline of the brain before quantifying the third ventricle shape. To build the vertex-wise correspondence between the individual third ventricle and the template mesh, we employ a minimal-distortion surface deformation framework. In addition, to account for topological variations, we implement geometric constraints guiding the template mesh to have zero width where the inter-thalamic adhesion passes through, preventing vertices crossing between left and right walls of the third ventricle. The individual shapes are compared using a vertex-wise deformity from the symmetric template. Results Experiments on imaging and demographic data from a study of aging showed that our model was sensitive in assessing morphological differences between individuals in relation to brain volume (i.e. proxy for general brain atrophy), gender and the fluid intelligence at age 72. It also revealed that the proposed method can detect the regional and asymmetrical deformation unlike the conventional measures: volume (median 1.95 ml, IQR 0.96 ml) and width of the third

  15. Detecting Growth Shape Misspecifications in Latent Growth Models: An Evaluation of Fit Indexes

    Science.gov (United States)

    Leite, Walter L.; Stapleton, Laura M.

    2011-01-01

    In this study, the authors compared the likelihood ratio test and fit indexes for detection of misspecifications of growth shape in latent growth models through a simulation study and a graphical analysis. They found that the likelihood ratio test, MFI, and root mean square error of approximation performed best for detecting model misspecification…

  16. The model of magnetic-field-controlled shape memory effect in NiMnGa

    Energy Technology Data Exchange (ETDEWEB)

    Likhachev, A.A. [Inst. of Metal Physics, Kiev (Ukraine). Dept. of Phase Transitions; Ullakko, K. [Inst. of Metal Physics, Kiev (Ukraine). Dept. of Phase Transitions; Helsinki Univ. of Technology, Espoo (Finland). Lab. of Engineering Physics and Mathematics

    2001-11-01

    This report represents some new experimental results and the quantitative model describing large magneto-strain effect and main mechanical and magnetic properties observed in several ferromagnetic shape-memory alloys. The model application to giant magneto-strain effect recently found in some non-stoichiometric Ni-Mn-Ga alloys is discussed. (orig.)

  17. On the selection of shape and orientation of a greenhouse. Thermal modeling and experimental validation

    Energy Technology Data Exchange (ETDEWEB)

    Sethi, V.P. [Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana 141 004, Punjab (India)

    2009-01-15

    In this study, five most commonly used single span shapes of greenhouses viz. even-span, uneven-span, vinery, modified arch and quonset type have been selected for comparison. The length, width and height (at the center) are kept same for all the selected shapes. A mathematical model for computing transmitted total solar radiation (beam, diffused and ground reflected) at each hour, for each month and at any latitude for the selected geometry greenhouses (through each wall, inclined surfaces and roofs) is developed for both east-west and north-south orientation. Computed transmitted solar radiation is then introduced in a transient thermal model developed to compute hourly inside air temperature for each shape and orientation. Experimental validation of both the models is carried out for the measured total solar radiation and inside air temperature for an east-west orientation, even-span greenhouse (for a typical day in summer) at Ludhiana (31 N and 77 E) Punjab, India. During the experimentation, capsicum crop is grown inside the greenhouse. The predicted and measured values are in close agreement. Results show that uneven-span shape greenhouse receives the maximum and quonset shape receives the minimum solar radiation during each month of the year at all latitudes. East-west orientation is the best suited for year round greenhouse applications at all latitudes as this orientation receives greater total radiation in winter and less in summer except near the equator. Results also show that inside air temperature rise depends upon the shape of the greenhouse and this variation from uneven-span shape to quonset shape is 4.6 C (maximum) and 3.5 C (daily average) at 31 N latitude. (author)

  18. A unified spray forming model for the prediction of billet shape geometry

    DEFF Research Database (Denmark)

    Hattel, Jesper; Pryds, Nini

    2004-01-01

    In the present work a unified model for simulating the spray forming process has been developed. Models for the atomization and the deposition processes have been coupled together in order to obtain a new unified description of the spray forming process. The model is able to predict the shape and...... part of the present work, is also described. Results from the integrated model are presented and the potential for better process understanding as well as process optimization is evident....

  19. Event-Based Activity Modeling

    DEFF Research Database (Denmark)

    Bækgaard, Lars

    2004-01-01

    We present and discuss a modeling approach that supports event-based modeling of information and activity in information systems. Interacting human actors and IT-actors may carry out such activity. We use events to create meaningful relations between information structures and the related activit...

  20. Hydration and diffusion processes shape microbial community organization and function in model soil aggregates

    Science.gov (United States)

    Ebrahimi, Ali; Or, Dani

    2015-12-01

    The constantly changing soil hydration status affects gas and nutrient diffusion through soil pores and thus the functioning of soil microbial communities. The conditions within soil aggregates are of particular interest due to limitations to oxygen diffusion into their core, and the presence of organic carbon often acting as binding agent. We developed a model for microbial life in simulated soil aggregates comprising of 3-D angular pore network model (APNM) that mimics soil hydraulic and transport properties. Within these APNM, we introduced individual motile (flagellated) microbial cells with different physiological traits that grow, disperse, and respond to local nutrients and oxygen concentrations. The model quantifies the dynamics and spatial extent of anoxic regions that vary with hydration conditions, and their role in shaping microbial community size and activity and the spatial (self) segregation of anaerobes and aerobes. Internal carbon source and opposing diffusion directions of oxygen and carbon within an aggregate were essential to emergence of stable coexistence of aerobic and anaerobic communities (anaerobes become extinct when carbon sources are external). The model illustrates a range of hydration conditions that promote or suppress denitrification or decomposition of organic matter and thus affect soil GHG emissions. Model predictions of CO2 and N2O production rates were in good agreement with limited experimental data. These limited tests support the dynamic modeling approach whereby microbial community size, composition, and spatial arrangement emerge from internal interactions within soil aggregates. The upscaling of the results to a population of aggregates of different sizes embedded in a soil profile is underway.

  1. Shape regulated anticancer activities and systematic toxicities of drug nanocrystals in vivo.

    Science.gov (United States)

    Zhou, Mengjiao; Zhang, Xiujuan; Yu, Caitong; Nan, Xueyan; Chen, Xianfeng; Zhang, Xiaohong

    2016-01-01

    In this paper, shape regulated anticancer activities as well as systematic toxicities of hydroxycamptothecin nanorods and nanoparticles (HCPT NRs and NPs) were systematically studied. In vitro and in vivo therapeutic efficacies were evaluated in cancer cells and tumor-bearing mice, indicating that NRs possessed superior antitumor efficacy over NPs at the equivalent dose, while systematic toxicity of the differently shaped nanodrugs assessed in healthy mice, including the maximum tolerated dose, blood analysis and histology examinations and so on, suggested that the NRs also caused higher toxicities than NPs, and also had a long-term toxicity. These results imply that the balance between anticancer efficiency and systematic toxicity of drug nanocrystals should be fully considered in practice, which will provide new concept in the future design of drug nanocrystals for cancer therapy. From the Clinical Editor: Advances in nanotechnology have enabled the design of novel nanosized drugs for the treatment of cancer. One of the interesting findings thus far is the different biological effects seen with different shaped nanoparticles. In this article, the authors investigated and compared the anticancer activities of hydroxycamptothecin nanorods and nanoparticles. The experimental data would provide a better understanding for future drug design. PMID:26427356

  2. Growth and shape modelling of the rabbit tibia: study of the dynamics of developing skeleton.

    Science.gov (United States)

    Pazzaglia, U E; Zarattini, G; Spagnuolo, F; Superti, G; Marchese, M

    2012-06-01

    The proliferative impulse of the growth plate cartilage and related structures and its effect on the dimensions of long bones are well documented. The modulation of shape, however, is less known, and in general, it is referred to the coupled resorption/apposition process of bone modelling. A morphometric study was carried out on rabbit tibiae comparing size increments and shape changes in relation to age. Utilizing measurements made using dried bones, radiography and computerized tomography, it was possible to perform a three-dimensional analysis of shape modulation occurring during a period of growth extending from 3 months to 1 year of age. The dynamics of the shape changes related to growth were studied with a fluorescent tetracycline labelling. This enabled correlation of shape modulation with the 3-D distribution of apposition and resorption. The current thinking behind the influences and mechanical forces affecting bone architecture was discussed in the light of these findings. Several factors play a role in the structural organization of the human and upper vertebrates' skeleton, whose shape is genetically determined in the complex process usually referred as 'modelling'. This does not conflict with the existing evidence of remodelling being influenced by mechanical stimuli, but the unsolved question remains how physical forces (strains) act on the biological substrate of cartilage and bone cells.

  3. Objective estimation of body condition score by modeling cow body shape from digital images.

    Science.gov (United States)

    Azzaro, G; Caccamo, M; Ferguson, J D; Battiato, S; Farinella, G M; Guarnera, G C; Puglisi, G; Petriglieri, R; Licitra, G

    2011-04-01

    Body condition score (BCS) is considered an important tool for management of dairy cattle. The feasibility of estimating the BCS from digital images has been demonstrated in recent work. Regression machines have been successfully employed for automatic BCS estimation, taking into account information of the overall shape or information extracted on anatomical points of the shape. Despite the progress in this research area, such studies have not addressed the problem of modeling the shape of cows to build a robust descriptor for automatic BCS estimation. Moreover, a benchmark data set of images meant as a point of reference for quantitative evaluation and comparison of different automatic estimation methods for BCS is lacking. The main objective of this study was to develop a technique that was able to describe the body shape of cows in a reconstructive way. Images, used to build a benchmark data set for developing an automatic system for BCS, were taken using a camera placed above an exit gate from the milking robot. The camera was positioned at 3 m from the ground and in such a position to capture images of the rear, dorsal pelvic, and loin area of cows. The BCS of each cow was estimated on site by 2 technicians and associated to the cow images. The benchmark data set contained 286 images with associated BCS, anatomical points, and shapes. It was used for quantitative evaluation. A set of example cow body shapes was created. Linear and polynomial kernel principal component analysis was used to reconstruct shapes of cows using a linear combination of basic shapes constructed from the example database. In this manner, a cow's body shape was described by considering her variability from the average shape. The method produced a compact description of the shape to be used for automatic estimation of BCS. Model validation showed that the polynomial model proposed in this study performs better (error=0.31) than other state-of-the-art methods in estimating BCS even at the

  4. Experimental and modelling studies of the shape memory properties of amorphous polymer network composites

    Science.gov (United States)

    Arrieta, J. S.; Diani, J.; Gilormini, P.

    2014-09-01

    Shape memory polymer composites (SMPCs) have become an important way to leverage improvements in the development of applications featuring shape memory polymers (SMPs). In this study, an amorphous SMP matrix has been filled with different types of reinforcements. An experimental set of results is presented and then compared to three-dimensional (3D) finite-element simulations. Thermomechanical shape memory cycles were performed in uniaxial tension. The fillers effect was studied in stress-free and constrained-strain recoveries. Experimental observations indicate complete shape recovery and put in evidence the increased sensitivity of constrained length stress recoveries to the heating ramp on the tested composites. The simulations reproduced a simplified periodic reinforced composite and used a model for the matrix material that has been previously tested on regular SMPs. The latter combines viscoelasticity at finite strain and time-temperature superposition. The simulations easily allow representation of the recovery properties of a reinforced SMP.

  5. RIGID-PLASTIC MECHANICAL MODEL FOR THE FORGING METHOD WITH HORIZONTAL V-SHAPED ANVIL

    Institute of Scientific and Technical Information of China (English)

    LIU Zhubai; NI Liyong; LIU Guohui; ZHANG Yongjun; ZHU Wenbo

    2006-01-01

    In order to decrease the anisotropy of mechanical properties, the rigid-plastic mechanical model for the forging method with horizontal V-shaped anvil is presented. The forging method,through the change of anvils shape, is able to control fibrous tissue direction, to improve the anisotropy of mechanical properties of axial forgings, to realize uniform forging. Therefore, the forging method can overcome the defect that conventional forging methods produce. The mechanism of the forging method with horizontal V-shaped anvil and the process of metal deformation are analyzed. The agreement of theoretical analysis with experimental study verifies the fact that the forging method with horizontal V-shaped anvil can control effectively the mechanical properties of axial forgings.

  6. Passive mechanical models of fish caudal fins: effects of shape and stiffness on self-propulsion.

    Science.gov (United States)

    Feilich, Kara L; Lauder, George V

    2015-06-01

    Fishes are found in a great variety of body forms with tail shapes that vary from forked tuna-like tails to the square-shaped tails found in some deep-bodied species. Hydrodynamic theory suggests that a fish's body and tail shape affects undulatory swimming performance. For example, a narrow caudal peduncle is believed to reduce drag, and a tuna-like tail to increase thrust. Despite the prevalence of these assertions, there is no experimental verification of the hydrodynamic mechanisms that may confer advantages on specific forms. Here, we use a mechanically-actuated flapping foil model to study how two aspects of shape, caudal peduncle depth and presence or absence of a forked caudal fin, may affect different aspects of swimming performance. Four different foil shapes were each made of plastics of three different flexural stiffnesses, permitting us to study how shape might interact with stiffness to produce swimming performance. For each foil, we measured the self-propelling swimming speed. In addition, we measured the forces, torques, cost of transport and power coefficient of each foil swimming at its self-propelling speed. There was no single 'optimal' foil exhibiting the highest performance in all metrics, and for almost all measures of swimming performance, foil shape and flexural stiffness interacted in complicated ways. Particle image velocimetry of several foils suggested that stiffness might affect the relative phasing of the body trailing edge and the caudal fin leading edge, changing the flow incident to the tail, and affecting hydrodynamics of the entire foil. The results of this study of a simplified model of fish body and tail morphology suggest that considerable caution should be used when inferring a swimming performance advantage from body and tail shape alone. PMID:25879846

  7. 3D geometry analysis of the medial meniscus--a statistical shape modeling approach.

    Science.gov (United States)

    Vrancken, A C T; Crijns, S P M; Ploegmakers, M J M; O'Kane, C; van Tienen, T G; Janssen, D; Buma, P; Verdonschot, N

    2014-10-01

    The geometry-dependent functioning of the meniscus indicates that detailed knowledge on 3D meniscus geometry and its inter-subject variation is essential to design well functioning anatomically shaped meniscus replacements. Therefore, the aim of this study was to quantify 3D meniscus geometry and to determine whether variation in medial meniscus geometry is size- or shape-driven. Also we performed a cluster analysis to identify distinct morphological groups of medial menisci and assessed whether meniscal geometry is gender-dependent. A statistical shape model was created, containing the meniscus geometries of 35 subjects (20 females, 15 males) that were obtained from MR images. A principal component analysis was performed to determine the most important modes of geometry variation and the characteristic changes per principal component were evaluated. Each meniscus from the original dataset was then reconstructed as a linear combination of principal components. This allowed the comparison of male and female menisci, and a cluster analysis to determine distinct morphological meniscus groups. Of the variation in medial meniscus geometry, 53.8% was found to be due to primarily size-related differences and 29.6% due to shape differences. Shape changes were most prominent in the cross-sectional plane, rather than in the transverse plane. Significant differences between male and female menisci were only found for principal component 1, which predominantly reflected size differences. The cluster analysis resulted in four clusters, yet these clusters represented two statistically different meniscal shapes, as differences between cluster 1, 2 and 4 were only present for principal component 1. This study illustrates that differences in meniscal geometry cannot be explained by scaling only, but that different meniscal shapes can be distinguished. Functional analysis, e.g. through finite element modeling, is required to assess whether these distinct shapes actually influence

  8. Modeling and Testing of Hydrodynamic Damping Model for a Complex-shaped Remotely-operated Vehicle for Control

    Institute of Scientific and Technical Information of China (English)

    Cheng Chin; Michael Lau

    2012-01-01

    In this paper,numerical modeling and model testing of a complex-shaped remotely-operated vehicle (ROV) were shown.The paper emphasized the systematic modeling of hydrodynamic damping using the computational fluid dynamic software ANSYS-CFXTM on the complex-shaped ROV,a practice that is not commonly applied.For initial design and prototype testing during the developmental stage,small-scale testing using a free-decaying experiment was used to verify the theoretical models obtained from ANSYS-CFXTM.Simulation results are shown to coincide with the experimental tests.The proposed method could determine the hydrodynamic damping coefficients of the ROV.

  9. Active control: Wind turbine model

    DEFF Research Database (Denmark)

    Bindner, H.

    1999-01-01

    validation as well as parameter estimation. The model includes a simple model of the structure of the turbine including tower and flapwise blade bending,a detailed model of the gear box and induction generator, a linearized aerodynamic model including modelling of induction lag and actuator and sensor models......This report is a part of the reporting of the work done in the project 'Active Control of Wind Turbines'. This project aim is to develop a simulation model for design of control systems for turbines with pitch control and to use that model to designcontrollers. This report describes the model...... developed for controller design and analysis. Emphasis has been put on establishment of simple models describing the dynamic behavior of the wind turbine in adequate details for controller design. This hasbeen done with extensive use of measurements as the basis for selection of model complexity and model...

  10. Shape-Dependent Biomimetic Inhibition of Enzyme by Nanoparticles and Their Antibacterial Activity.

    Science.gov (United States)

    Cha, Sang-Ho; Hong, Jin; McGuffie, Matt; Yeom, Bongjun; VanEpps, J Scott; Kotov, Nicholas A

    2015-09-22

    Enzyme inhibitors are ubiquitous in all living systems, and their biological inhibitory activity is strongly dependent on their molecular shape. Here, we show that small zinc oxide nanoparticles (ZnO NPs)-pyramids, plates, and spheres-possess the ability to inhibit activity of a typical enzyme β-galactosidase (GAL) in a biomimetic fashion. Enzyme inhibition by ZnO NPs is reversible and follows classical Michaelis-Menten kinetics with parameters strongly dependent on their geometry. Diverse spectroscopic, biochemical, and computational experimental data indicate that association of GAL with specific ZnO NP geometries interferes with conformational reorganization of the enzyme necessary for its catalytic activity. The strongest inhibition was observed for ZnO nanopyramids and compares favorably to that of the best natural GAL inhibitors while being resistant to proteases. Besides the fundamental significance of this biomimetic function of anisotropic NPs, their capacity to serve as degradation-resistant enzyme inhibitors is technologically attractive and is substantiated by strong shape-specific antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), endemic for most hospitals in the world. PMID:26325486

  11. Interactive Shape Modeling using a Skeleton-Mesh Co-Representation

    OpenAIRE

    Bærentzen, Jacob Andreas; Abdrashitov, Rinat; Singh, Karan

    2014-01-01

    We introduce the Polar-Annular Mesh representation (PAM). A PAM is a mesh-skeleton co-representation designed for the modeling of 3D organic, articulated shapes. A PAM represents a manifold mesh as a partition of polar (triangle fans) and annular (rings of quads) regions. The skeletal topology of a shape is uniquely embedded in the mesh connectivity of a PAM, enabling both surface and skeletal modeling operations, interchangeably and directly on the mesh itself. We develop an algorithm to con...

  12. A Model to Describe the Magnetomechanical Behavior of Martensite in Magnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Zaoyang Guo

    2014-01-01

    Full Text Available A model to describe the constitutive behavior of magnetic shape memory alloy composed with pure martensite is proposed based on the analysis of variants reorientation. A hyperbolic tangent expression is given to describe the variants transition during magnetic and mechanical loading process. The main features of magnetic shape memory alloy, such as pseudoelastic and partially pseudoelastic behavior as well as minor hysteretic loops, can be successfully replicated with the proposed model. A good agreement is achieved between calculated results and experimental data for NiMnGa single crystal.

  13. Instability of the hedgehog shape for the octet baryon in the chiral quark soliton model

    CERN Document Server

    Akiyama, S; Akiyama, Satoru; Futami, Yasuhiko

    2003-01-01

    In this paper the stability of the hedgehog shape of the chiral soliton is studied for the octet baryon with the SU(3) chiral quark soliton model. The strangeness degrees of freedom are treated by a simplified bound-state approach, which omits the locality of the kaon wave function. The mean field approximation for the flavor rotation is applied to the model. The classical soliton changes shape according to the strangeness. The baryon appears as a rotational band of the combined system of the deformed soliton and the kaon.

  14. Moving Kriging shape function modeling of vector TARMA models for modal identification of linear time-varying structural systems

    Science.gov (United States)

    Yang, Wu; Liu, Li; Zhou, Si-Da; Ma, Zhi-Sai

    2015-10-01

    This work proposes a Moving Kriging (MK) shape function modeling method for modal identification of linear time-varying (LTV) structural systems based on vector time-dependent autoregressive moving average (VTARMA) models. It aims to avoid the functional subspaces selection of the conventional functional series VTARMA (FS-VTARMA) models. Instead of the common basis functions, it constructs the time-varying coefficients on the time nodes with the MK shape functions in a compact support domain. The merit of the MK shape function is to determine its shape parameters upon vector random vibration signals adaptively. Model identification is effectively dealt with through an optimization scheme that decomposes the identification problem into two subproblems: estimating model parameters via two-stage least squares (2SLS) method and estimating shape function parameters via a discrete-continuous-variable hybrid optimization. In addition, the model order selection is achieved by the optimization scheme. This method has been validated by a Monte Carlo study of simulation case and further by an experimental test case, and the performance and potential advantages are illustrated.

  15. A New Finite Interval Lifetime Distribution Model for Fitting Bathtub-Shaped Failure Rate Curve

    Directory of Open Access Journals (Sweden)

    Xiaohong Wang

    2015-01-01

    Full Text Available This paper raised a new four-parameter fitting model to describe bathtub curve, which is widely used in research on components’ life analysis, then gave explanation of model parameters, and provided parameter estimation method as well as application examples utilizing some well-known lifetime data. By comparative analysis between the new model and some existing bathtub curve fitting model, we can find that the new fitting model is very convenient and its parameters are clear; moreover, this model is of universal applicability which is not only suitable for bathtub-shaped failure rate curves but also applicable for the constant, increasing, and decreasing failure rate curves.

  16. A reconfigurable CBP/LP active RC filter with noise-shaping technique for wireless receivers

    International Nuclear Information System (INIS)

    A reconfigurable complex band-pass (CBP)/low-pass (LP) active-RC filter with a noise-shaping technique for wireless receivers is presented. Its bandwidth is reconfigurable among 500 kHz, 1 MHz and 4 MHz in LP mode and 1 MHz, 2 MHz and 8 MHz in CBP mode with 3 MHz center frequency. The Op-Amps used in the filter are realized in cell arrays in order to obtain scalable power consumption among the different operation modes. Furthermore, the filter can be configured into the 1st order, 2nd order or 3rd order mode, thus achieving a flexible filtering property. The noise-shaping technique is introduced to suppress the flicker noise contribution. The filter has been implemented in 180 nm CMOS and consumes less than 3 mA in the 3rd 8 MHz-bandwidth CBP mode. The spot noise at 100 Hz can be reduced by 14.4 dB at most with the introduced noise-shaping technique. (semiconductor integrated circuits)

  17. Seamless tube shape is constrained by endocytosis-dependent regulation of active Moesin.

    Science.gov (United States)

    Schottenfeld-Roames, Jodi; Rosa, Jeffrey B; Ghabrial, Amin S

    2014-08-01

    Most tubes have seams (intercellular or autocellular junctions that seal membranes together into a tube), but "seamless" tubes also exist. In Drosophila, stellate-shaped tracheal terminal cells make seamless tubes, with single branches running through each of dozens of cellular extensions. We find that mutations in braided impair terminal cell branching and cause formation of seamless tube cysts. We show that braided encodes Syntaxin7 and that cysts also form in cells deficient for other genes required either for membrane scission (shibire) or for early endosome formation (Rab5, Vps45, and Rabenosyn-5). These data define a requirement for early endocytosis in shaping seamless tube lumens. Importantly, apical proteins Crumbs and phospho-Moesin accumulate to aberrantly high levels in braided terminal cells. Overexpression of either Crumbs or phosphomimetic Moesin induced lumenal cysts and decreased terminal branching. Conversely, the braided seamless tube cyst phenotype was suppressed by mutations in crumbs or Moesin. Indeed, mutations in Moesin dominantly suppressed seamless tube cyst formation and restored terminal branching. We propose that early endocytosis maintains normal steady-state levels of Crumbs, which recruits apical phosphorylated (active) Moe, which in turn regulates seamless tube shape through modulation of cortical actin filaments. PMID:25065756

  18. Modelling and engineering aspects of the plasma shape control in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Albanese, R.; Ambrosino, G.; Coccorese, E.; Pironti, A. [Naples Univ., Dip. di Ingegneria Elettrica, Consorzio CREATE, Naples (Italy); Lister, J.B.; Ward, D.J. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)

    1996-10-01

    As part of the ITER Engineering Design Activity, a number of questions related to plasma control has been addressed, using linearised and non-linear simulation codes to assess the control of the plasma shape given the particular design restrictions of ITER. (author) 5 figs., 1 tab., 2 refs.

  19. ACTIVE VIBRATION CONTROL OF FINITE L-SHAPED BEAM WITH TRAVELLING WAVE APPROACH

    Institute of Scientific and Technical Information of China (English)

    Chunchuan Liu; Fengming Li; Wenhu Huang

    2010-01-01

    In this paper,the disturbance propagation and active vibration control of a finite L-shaped beam are studied.The dynamic response of the structure is obtained by the travelling wave approach.The active vibration suppression of the finite L-shaped beam is performed based on the structural vibration power flow.In the numerical calculation,the influences of the near field effect of the error sensor and the small error of the control forces on the control results are all considered.The simulation results indicate that the structural vibration response in the medium and high frequency regions can be effectively computed by the travelling wave method.The effect of the active control by controlling the power flow is much better than that by controlling the acceleration in some cases.And the control results by the power flow method are slightly affected by the locations of the error sensor and the small error of the control forces.

  20. Instantaneous Shape Sampling - a model for the $\\gamma$-absorption cross section of transitional nuclei

    CERN Document Server

    Bentley, I; Doenau, F; Frauendorf, S; Kampfer, B; Schwengner, R; Zhang, S

    2010-01-01

    The influence of the quadrupole shape fluctuations on the dipole vibrations in transitional nuclei is investigated in the framework of the Instantaneous Shape Sampling Model, which combines the Interacting Boson Model for the slow collective quadrupole motion with the Random Phase Approximation for the rapid dipole vibrations. Coupling to the complex background configurations is taken into account by folding the results with a Lorentzian with an energy dependent width. The low-energy energy portion of the $\\gamma$- absorption cross section, which is important for photo-nuclear processes, is studied for the isotopic series of Kr, Xe, Ba, and Sm. The experimental cross sections are well reproduced. The low-energy cross section is determined by the Landau fragmentation of the dipole strength and its redistribution caused by the shape fluctuations. Collisional damping only wipes out fluctuations of the absorption cross section, generating the smooth energy dependence observed in experiment. In the case of semi-ma...

  1. A model for estimating body shape biological age based on clinical parameters associated with body composition

    Directory of Open Access Journals (Sweden)

    Bae CY

    2012-12-01

    Full Text Available Chul-Young Bae,1 Young Gon Kang,2 Young-Sung Suh,3 Jee Hye Han,4 Sung-Soo Kim,5 Kyung Won Shim61MediAge Research Center, Seoul, Korea; 2Chaum Power Aging Center, College of Medicine, CHA University, Seoul, Korea; 3Health Promotion Center, Keimyung University Dongsam Medical Center, Daegu, Korea; 4Department of Family Medicine, College of Medicine, Eulji University, Seoul, Korea; 5Department of Family Medicine, College of Medicine, Chungnam National University, Daejeon, Korea; 6Department of Family Medicine, Ewha Womans University Mokdong Hospital, Ewha Womans University, Seoul, KoreaBackground: To date, no studies have attempted to estimate body shape biological age using clinical parameters associated with body composition for the purposes of examining a person's body shape based on their age.Objective: We examined the relations between clinical parameters associated with body composition and chronological age, and proposed a model for estimating the body shape biological age.Methods: The study was conducted in 243,778 subjects aged between 20 and 90 years who received a general medical checkup at health promotion centers at university and community hospitals in Korea from 2004 to 2011.Results: In men, the clinical parameters with the highest correlation to age included the waist-to-hip ratio (r = 0.786, P < 0.001, hip circumference (r = −0.448, P < 0.001, and height (r = −0.377, P < 0.001. In women, the clinical parameters with the highest correlation to age include the waist-to-hip ratio (r = 0.859, P < 0.001, waist circumference (r = 0.580, P < 0.001, and hip circumference (r = 0.520, P < 0.001. To estimate the optimal body shape biological age based on clinical parameters associated with body composition, we performed a multiple regression analysis. In a model estimating the body shape biological age, the coefficient of determination (R2 was 0.71 in men and 0.76 in women.Conclusion: Our model for estimating body shape biological age

  2. Size and shape dependence of the photocatalytic activity of TiO2 nanocrystals: a total scattering Debye function study.

    Science.gov (United States)

    Cernuto, Giuseppe; Masciocchi, Norberto; Cervellino, Antonio; Colonna, Gian Maria; Guagliardi, Antonietta

    2011-03-01

    Nanocrystalline TiO(2) samples, prepared for smart textiles applications by the sol-gel technique in acidic or basic media, have been characterized by synchrotron X-ray powder diffraction and total scattering methods based on a fast implementation of the Debye function and original algorithms for sampling interatomic distances. Compared to the popular and widely used Rietveld-based approaches, our method is able to simultaneously model both Bragg and diffuse contributions and to quantitatively extract either sizes and size distribution information from the experimental data. The photocatalytic activity of the investigated samples is here systematically correlated to the average sizes and size distributions of anisotropically shaped coherent domains, modeled according to bivariate populations of nanocrystals grown along two normal directions. PMID:21323336

  3. Solar granulation and statistical crystallography: A modeling approach using size-shape relations

    Science.gov (United States)

    Noever, D. A.

    1994-01-01

    The irregular polygonal pattern of solar granulation is analyzed for size-shape relations using statistical crystallography. In contrast to previous work which has assumed perfectly hexagonal patterns for granulation, more realistic accounting of cell (granule) shapes reveals a broader basis for quantitative analysis. Several features emerge as noteworthy: (1) a linear correlation between number of cell-sides and neighboring shapes (called Aboav-Weaire's law); (2) a linear correlation between both average cell area and perimeter and the number of cell-sides (called Lewis's law and a perimeter law, respectively) and (3) a linear correlation between cell area and squared perimeter (called convolution index). This statistical picture of granulation is consistent with a finding of no correlation in cell shapes beyond nearest neighbors. A comparative calculation between existing model predictions taken from luminosity data and the present analysis shows substantial agreements for cell-size distributions. A model for understanding grain lifetimes is proposed which links convective times to cell shape using crystallographic results.

  4. The KOALA Shape Modeling Technique Validated at (21) Lutetia by ESA Rosetta Mission

    Science.gov (United States)

    Carry, Benoit; Merline, W. J.; Kaasalainen, M.; Conrad, A.; Drummond, J. D.; Dumas, C.; Kueppers, M.; OSIRIS Instrument Team

    2010-10-01

    We recently developed a shape reconstruction algorithm, dubbed KOALA (Kaasalainen, IPI 2010; Carry et al., Icarus 2010), which allows the determination of the size, shape, and spin properties of asteroids from a combined data set of disk-resolved images, optical lightcurves, and stellar occultations. Using adaptive optics (AO) imaging systems on the Keck and VLT telescopes, we acquired more than 300 images of the main-belt asteroid (21) Lutetia in 2007 and 2008. We combined these images with 50 lightcurves spanning some 48 years and including data taken almost up until the time of flyby. We produced a 3D shape model of Lutetia and determined the spin pole and rotation rate (Carry et al., submitted to A&A). On 2010 July 10, the International Rosetta Mission of the European Space Agency successfully encountered (21) Lutetia. The images recorded by the OSIRIS camera on-board Rosetta revealed our shape prediction to be accurate. We will present the KOALA (Knitted Occultation, Adaptive-optics, and Lightcurve Analysis) method, and a comparison of our shape model with the high-resolution images acquired by Rosetta during the flyby.

  5. Model-free 3D face shape reconstruction from video sequences

    NARCIS (Netherlands)

    Dam, van Chris; Veldhuis, Raymond; Spreeuwers, Luuk

    2013-01-01

    In forensic comparison of facial video data, often only the best quality frontal face frames are selected, and hence much video data is ignored. To improve 2D facial comparison for law enforcement and forensic investigation, we introduce a model-free 3D shape reconstruction algorithm based on 2D lan

  6. Landmark-based model-free 3D face shape reconstruction from video sequences

    NARCIS (Netherlands)

    Dam, van Chris; Veldhuis, Raymond; Spreeuwers, Luuk; Broemme, A.; Busch, C.

    2013-01-01

    In forensic comparison of facial video data, often only the best quality frontal face frames are selected, and hence potentially useful video data is ignored. To improve 2D facial comparison for law enforcement and forensic investigation, we introduce a model-free 3D shape reconstruction algorithm b

  7. Extraction of the mode shapes of a segmented ship model with a hydroelastic response

    Directory of Open Access Journals (Sweden)

    Kim Yooil

    2015-11-01

    Full Text Available The mode shapes of a segmented hull model towed in a model basin were predicted using both the Proper Orthogonal Decomposition (POD and cross random decrement technique. The proper orthogonal decomposition, which is also known as Karhunen-Loeve decomposition, is an emerging technology as a useful signal processing technique in structural dynamics. The technique is based on the fact that the eigenvectors of a spatial coherence matrix become the mode shapes of the system under free and randomly excited forced vibration conditions. Taking advantage of the simplicity of POD, efforts have been made to reveal the mode shapes of vibrating flexible hull under random wave excitation. First, the segmented hull model of a 400 K ore carrier with 3 flexible connections was towed in a model basin under different sea states and the time histories of the vertical bending moment at three different locations were measured. The measured response time histories were processed using the proper orthogonal decomposition, eventually to obtain both the first and second vertical vibration modes of the flexible hull. A comparison of the obtained mode shapes with those obtained using the cross random decrement technique showed excellent correspondence between the two results.

  8. Spin dependence of even-even nucleus shape in the model of Davydov-Chaban

    International Nuclear Information System (INIS)

    The shape parameters of the even-even nuclei 154Gd, 156,158,160Dy, 164,168Er, 168Yb, 176Hf, 180W are calculated within the phenomenological model of the nonaxial soft by β-oscillation deformed nucleus. The spin dependence of the softness, nonaxiality and energy factor is assumed

  9. Short Term Evaluation of an Anatomically Shaped Polycarbonate Urethane Total Meniscus Replacement in a Goat Model

    NARCIS (Netherlands)

    Vrancken, A.C.T.; Madej, W.; Hannink, G.; Verdonschot, N.J.; Tienen, T.G. van; Buma, P.

    2015-01-01

    PURPOSE: Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU), total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on th

  10. Modelling the spatial shape of nondiffracting beams: Experimental generation of Frozen Waves via computer generated holograms

    CERN Document Server

    Vieira, Tárcio A; Gesualdi, Marcos R R

    2013-01-01

    In this paper we implement experimentally the spatial shape modelling of nondiffracting optical beams via computer generated holograms. The results reported here are the experimental confirmation of the so called Frozen Wave method, developed few years ago. Optical beams of this type can possess potential applications in optical tweezers, medicine, atom guiding, remote sensing, etc..

  11. A statistical multi-vertebrae shape+pose model for segmentation of CT images

    Science.gov (United States)

    Rasoulian, Abtin; Rohling, Robert N.; Abolmaesumi, Purang

    2013-03-01

    Segmentation of the spinal column from CT images is a pre-processing step for a range of image guided interventions. Current techniques focus on identification and separate segmentation of each vertebra. Recently, statistical multi-object shape models have been introduced to extract common statistical characteristics between several anatomies. These models are also used for segmentation purposes and are shown to be robust, accurate, and computationally tractable. In this paper, we reconstruct a statistical multi-vertebrae shape+pose model and propose a novel technique to register such a model to CT images. We validate our technique in terms of accuracy of the multi-vertebrae segmentation of CT images acquired from 16 subjects. The mean distance error achieved for all vertebrae is 1.17 mm with standard deviation of 0.38 mm.

  12. A thermomechanical model accounting for the behavior of shape memory alloys in finite deformations

    Science.gov (United States)

    Haller, Laviniu; Nedjar, Boumedienne; Moumni, Ziad; Vedinaş, Ioan; Trană, Eugen

    2016-07-01

    Shape memory alloys (SMA) comport an interesting behavior. They can undertake large strains and then recover their undeformed shape by heating. In this context, one of the aspects that challenged many researchers was the development of a mathematical model to predict the behavior of a known SMA under real-life conditions, or finite strain. This paper is aimed at working out a finite strain mathematical model for a Ni-Ti SMA, under the superelastic experiment conditions and under uniaxial mechanical loading, based on the Zaki-Moumni 3D mathematical model developed under the small perturbations assumption. Within the current article, a comparison between experimental findings and calculated results is also investigated. The proposed finite strain mathematical model shows good agreement with experimental data.

  13. Numerical Modeling of a Teeth-shaped Nano-plasmonic Waveguide Filter

    CERN Document Server

    Lin, Xianshi

    2009-01-01

    In this paper, tooth-shaped and multiple-teeth-shaped plasmonic filters in the metal-insulator-metal (MIM) waveguides are demonstrated numerically. By introducing a three-port waveguide splitter, a modified model based on the multiple-beam-interference and the scattering matrix is given. The ransmittance spectrum as a function of teeth width, depth, period and period number are respectively addressed. The result shows the new structure not only performs the filtering function as well as MIM grating-like structures, but also is of submicrometer size for ultra-high integration and relatively easy fabrication.

  14. Model-based pulse shape correction for CdTe detectors

    Science.gov (United States)

    Bargholtz, Chr.; Fumero, E.; Mårtensson, L.

    1999-02-01

    We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta.

  15. Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia

    OpenAIRE

    Carry, B.; Kaasalainen, M.; Merline, W. J.; Müller, T. G.; Jorda, L.; Drummond, J. D.; Berthier, J.; O'Rourke, L.; Durech, J.; Küppers, M.; Conrad, A; Tamblyn, P.; Dumas, C.; Sierks, H.; Team, the OSIRIS

    2011-01-01

    We present a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. We present our 3-D shape-modeling technique KOALA which is based on multi-dataset inversion. We compare the results we obtained with KOALA, pri...

  16. Pattern formation in a gene network model with boundary shape dependence

    Science.gov (United States)

    Diambra, Luis; da Fontoura Costa, Luciano

    2006-03-01

    A fundamental task in developmental biology is to identify the mechanisms which drive morphogenesis. Traditionally pattern formation have been modeled mainly using Turing-type mechanisms, where complex patterns arise by symmetry breaking. However, there is a growing experimental evidence that the influence of signals derived from surrounding tissues can contribute to the patterning processes. In this paper, we show that the interplay between the shape of surrounding tissues and a hierarchically organized gene regulatory network can be able to induce stable complex patterns. The rise of these patterns depends strongly on the shape of the surrounding tissues.

  17. Model-based pulse shape correction for CdTe detectors

    CERN Document Server

    Bargholtz, C; Maartensson, L

    1999-01-01

    We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta. (author)

  18. Neural network modeling for weld shape process of P-GMAW

    Institute of Scientific and Technical Information of China (English)

    Yan Zhihong; Wu Lin; Zhang Guangjun; Gao Hongming

    2007-01-01

    Weld shape control is a fundamental issue in automatic welding. In this paper, a double side visual system is established for pulsed gas metal arc welding (P-GMAW), and both topside and backside weld pool images can be captured and stored continuously in real time. By analyzing the weld shape regulation with the molten metal volume, some topside weld pool characterized parameters (WPCPs) are proposed for determining penetration in butt welding of thin mild steel. Moreover, some BP network models are established to predict backside weld pool width with welding parameters and WPCPs as inputs.

  19. A computer graphics based model for scattering from objects of arbitrary shapes in the optical region

    Science.gov (United States)

    Goel, Narendra S.; Rozehnal, Ivan; Thompson, Richard L.

    1991-01-01

    A computer-graphics-based model, named DIANA, is presented for generation of objects of arbitrary shape and for calculating bidirectional reflectances and scattering from them, in the visible and infrared region. The computer generation is based on a modified Lindenmayer system approach which makes it possible to generate objects of arbitrary shapes and to simulate their growth, dynamics, and movement. Rendering techniques are used to display an object on a computer screen with appropriate shading and shadowing and to calculate the scattering and reflectance from the object. The technique is illustrated with scattering from canopies of simulated corn plants.

  20. Analysis of shape isomer yields of 237Pu in the framework of dynamical–statistical model

    Indian Academy of Sciences (India)

    Hadi Eslamizadeh

    2012-02-01

    Data on shape isomer yield for + 235U reaction at $E^{\\text{lab}}$ = 20–29 MeV are analysed in the framework of a combined dynamical–statistical model. From this analysis, information on the double humped fission barrier parameters for some Pu isotopes has been obtained and it is shown that the depth of the second potential well should be less than the results of statistical model calculations.

  1. Shape Evolution of the Compound Nucleus in the Superheavy Element Synthesis Reaction via the BUU Model

    Institute of Scientific and Technical Information of China (English)

    WEI Liang; LIU Yu-Xin

    2005-01-01

    @@ By taking the BUU model, we simulate the superheavy element synthesis reaction. With the rotation effect being included in the B UU model, the effect of the non-centrality of the reaction 48 Ca + 238U→ 286112 is studied. It is shown that the promising impact parameter in the synthesis process can be released from zero to a value little smaller than the radius of the smaller nucleus involved in the reaction. Meanwhile, the compound nucleus may involve rich shape phases.

  2. Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia

    CERN Document Server

    Carry, B; Merline, W J; Müller, T G; Jorda, L; Drummond, J D; Berthier, J; O'Rourke, L; Durech, J; Küppers, M; Conrad, A; Tamblyn, P; Dumas, C; Sierks, H

    2011-01-01

    We present a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. We present our 3-D shape-modeling technique KOALA which is based on multi-dataset inversion. We compare the results we obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with the high-spatial resolution images of the asteroid taken with the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter with Lutetia. The spin axis determined with KOALA was found to be accurate to within two degrees, while the KOALA diameter determinations were within 2% of the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed by the spectacular visual agreement between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We fo...

  3. Using statistical deformable models to reconstruct vocal tract shape from magnetic resonance images.

    Science.gov (United States)

    Vasconcelos, M J M; Rua Ventura, S M; Freitas, D R S; Tavares, J M R S

    2010-10-01

    The mechanisms involved in speech production are complex and have thus been subject to growing attention by the scientific community. It has been demonstrated that magnetic resonance imaging (MRI) is a powerful means in the understanding of the morphology of the vocal tract. Over the last few years, statistical deformable models have been successfully used to identify and characterize bones and organs in medical images and point distribution models (PDMs) have gained particular relevance. In this work, the suitability of these models has been studied to characterize and further reconstruct the shape of the vocal tract in the articulation of Portuguese European (EP) speech sounds, one of the most spoken languages worldwide, with the aid of MR images. Therefore, a PDM has been built from a set of MR images acquired during the artificially sustained articulation of 25 EP speech sounds. Following this, the capacity of this statistical model to characterize the shape deformation of the vocal tract during the production of sounds was analysed. Next, the model was used to reconstruct five EP oral vowels and the EP fricative consonants. As far as a study on speech production is concerned, this study is considered to be the first approach to characterize and reconstruct the vocal tract shape from MR images by using PDMs. In addition, the findings achieved permit one to conclude that this modelling technique compels an enhanced understanding of the dynamic speech events involved in sustained articulations based on MRI, which are of particular interest for speech rehabilitation and simulation. PMID:21138233

  4. Fracture of granular materials composed of arbitrary grain shapes: A new cohesive interaction model

    Science.gov (United States)

    Neveu, A.; Artoni, R.; Richard, P.; Descantes, Y.

    2016-10-01

    Discrete Element Methods (DEM) are a useful tool to model the fracture of cohesive granular materials. For this kind of application, simple particle shapes (discs in 2D, spheres in 3D) are usually employed. However, dealing with more general particle shapes allows to account for the natural heterogeneity of grains inside real materials. We present a discrete model allowing to mimic cohesion between contacting or non-contacting particles whatever their shape in 2D and 3D. The cohesive interactions are made of cohesion points placed on interacting particles, with the aim of representing a cohesive phase lying between the grains. Contact situations are solved according to unilateral contact and Coulomb friction laws. In order to test the developed model, 2D unixial compression simulations are performed. Numerical results show the ability of the model to mimic the macroscopic behavior of an aggregate grain subject to axial compression, as well as fracture initiation and propagation. A study of the influence of model and sample parameters provides important information on the ability of the model to reproduce various behaviors.

  5. A review of modeling techniques for advanced effects in shape memory alloy behavior

    Science.gov (United States)

    Cisse, Cheikh; Zaki, Wael; Ben Zineb, Tarak

    2016-10-01

    micro, micro-macro and macro scales focusing pseudoelastic and shape memory effects. The paper reviews and discusses various techniques used in the literature for modeling complex behaviors observed in shape memory alloys (SMAs) that go beyond the core pseudoelastic and shape memory effects. These behaviors, which will be collectively referred to herein as ‘secondary effects’, include mismatch between austenite and martensite moduli, martensite reorientation under nonproportional multiaxial loading, slip and transformation-induced plasticity and their influence on martensite transformation, strong thermomechanical coupling and the influence of loading rate, tensile-compressive asymmetry, and the formation of internal loops due to incomplete phase transformation. In addition, because of their importance for practical design considerations, the paper discusses functional and structural fatigue, and fracture mechanics of SMAs.

  6. Laboratory simulation and modeling of size, shape distributed interstellar graphite dust analogues: A comparative study

    Science.gov (United States)

    Boruah, Manash J.; Gogoi, Ankur; Ahmed, Gazi A.

    2016-06-01

    The computation of the light scattering properties of size and shape distributed interstellar graphite dust analogues using discrete dipole approximation (DDA) is presented. The light scattering properties of dust particles of arbitrary shapes having sizes ranging from 0.5 to 5.0 μm were computed using DDSCAT 7.3.0 software package and an indigenously developed post-processing tool for size and shape averaging. In order to model realistic samples of graphite dust and compute their light scattering properties using DDA, different target geometries were generated to represent the graphite particle composition in terms of surface smoothness, surface roughness and aggregation or their combination, for using as the target for DDSCAT calculations. A comparison of the theoretical volume scattering function at 543.5 nm and 632.8 nm incident wavelengths with laboratory simulation is also presented in this paper.

  7. Quasi-static modeling of NiMnGa magnetic shape memory alloy

    Science.gov (United States)

    Couch, Ronald N.; Chopra, Inderjit

    2005-05-01

    A quasi-static model for NiMnGa magnetic shape memory alloy (MSMA) is formulated in parallel to the Brinson and Tanaka thermal SMA constitutive models. Since the shape memory effect (SME) and pseudoelasticity exist in both NiTi and NiMnGa, constitutive models for SMAs can serve as a basis for MSMA behavioral modeling. The quasi-static model for NiMnGa was characterized by nine material parameters identified by conducting a series of uniaxial compression tests in a constant field environment. These model parameters include free strain, Young"s modulus, fundamental critical stresses, fundamental threshold fields, and stress-influence coefficients. The Young"s moduli of the material in both its field and stress preferred configurations were determined to be 450 MPa and 820 MPa respectively, while the free strain was measured to be 5.8%. These test data were used to assemble a critical stress profile that is useful for determining model parameters and for understanding the dependence of critical stresses on magnetic fields. Once implemented, the analytical model shows good correlation with test data for all modes of NiMnGa quasi-static behavior, capturing both the magnetic shape memory effect and pseudoelasticity. Furthermore, the model is also capable of predicting partial pseudoelasticity, minor hysteretic loops and stress-strain behaviors. To correct for the effects of magnetic saturation, a series of stress influence functions were developed from the critical stress profile. Although requiring further refinement, the model"s results are encouraging, indicating that the model is a useful analytical tool for predicting NiMnGa actuator behavior.

  8. Applicability of Shape Memory Alloy Wire for an Active, Soft Orthotic

    Science.gov (United States)

    Stirling, Leia; Yu, Chih-Han; Miller, Jason; Hawkes, Elliot; Wood, Robert; Goldfield, Eugene; Nagpal, Radhika

    2011-07-01

    Current treatments for gait pathologies associated with neuromuscular disorders may employ a passive, rigid brace. While these provide certain benefits, they can also cause muscle atrophy. In this study, we examined NiTi shape memory alloy (SMA) wires that were annealed into springs to develop an active, soft orthotic (ASO) for the knee. Actively controlled SMA springs may provide variable assistances depending on factors such as when, during the gait cycle, the springs are activated; ongoing muscle activity level; and needs of the wearer. Unlike a passive brace, an active orthotic may provide individualized control, assisting the muscles so that they may be used more appropriately, and possibly leading to a re-education of the neuro-motor system and eventual independence from the orthotic system. A prototype was tested on a suspended, robotic leg to simulate the swing phase of a typical gait. The total deflection generated by the orthotic depended on the knee angle and the total number of actuators triggered, with a max deflection of 35°. While SMA wires have a high energy density, they require a significant amount of power. Furthermore, the loaded SMA spring response times were much longer than the natural frequency of an average gait for the power conditions tested. While the SMA wires are not appropriate for correction of gait pathologies as currently implemented, the ability to have a soft, actuated material could be appropriate for slower timescale applications.

  9. Patient-specific acetabular shape modelling: comparison among sphere, ellipsoid and conchoid parameterisations.

    Science.gov (United States)

    Cerveri, Pietro; Manzotti, Alfonso; Baroni, Guido

    2014-04-01

    The shape of the human acetabular cup was commonly represented as a hemisphere, but different geometries and patient-specific shapes have been recently proposed in the literature. Our aim was to test the limits of the sphericity assumption by comparing three different parameterisations, namely the sphere, the ellipsoid and the rotational conchoid. Models of hip surfaces, reconstructed from CT scans taken from Caucasian race cadavers and patients, were automatically processed to extract the acetabular surface. Two separate analyses were carried out on the overall acetabular shape, including both the acetabular fossa and the lunate surface (case A) and acetabular cup represented by the lunate surface only (case B). Nonlinear gradient-based and evolutionary computation approaches were implemented for the fitting process. Minor differences from the three idealised geometries were detected (median values of the fitting errors different from both the ellipsoid (p difference was detected between the ellipsoid and the conchoid for case A. Significance of the difference between ellipsoid and sphere (p difference was detected between the ellipsoid and the conchoid. In conclusion, we synthesise that the morphology of the overall acetabular cup can be parameterised both with an ellipsoid shape and with a conchoid shape as well with superior quality than the simple sphere. Differently, if one considers just the lunate surface, better fitting results are expected when using the ellipsoid. PMID:22789071

  10. Multi-scale modeling of shape distortions during sintering of bi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Bjørk, Rasmus; Olevsky, Eugene;

    2014-01-01

    theories like the continuum theory of sintering. A new multi-scale numerical approach for modeling of shape distortions during sintering of macroscopically inhomogeneous structures combined with a microstructure model is developed. The microstructures of the porous body are described by unit cells based on...... unit cells simulated by the kMC model. Examples of simulation of sintering of bi-layers based on different material systems are presented to illustrate the multi-scale model. The approach can be considered as an extension to the continuum theory of sintering combined with the meso-scale kinetic Monte...

  11. A quasi-static model for NiMnGa magnetic shape memory alloy

    Science.gov (United States)

    Couch, Ronald N.; Chopra, Inderjit

    2007-02-01

    A quasi-static model for NiMnGa magnetic shape memory alloy (MSMA) is formulated in parallel to the Brinson and Tanaka thermal SMA constitutive models. Since the shape memory effect (SME) and pseudoelasticity exist in both NiTi and NiMnGa, constitutive models for SMAs can serve as a basis for MSMA behavioral modeling. The simplified, linear, quasi-static model for NiMnGa was characterized by nine material parameters identified by conducting a series of uniaxial compression tests in a constant field environment. These model parameters include free strain, Young's modulus, fundamental critical stresses, fundamental threshold fields, and stress-influence coefficients. The Young's moduli of the material in both its field and stress preferred configurations were determined to be 450 MPa and 820 MPa respectively, while the free strain was measured to be 5.8%. These test data were used to assemble a critical stress profile that is useful for determining model parameters and for understanding the dependence of critical stresses on magnetic fields. Once implemented, the analytical model shows good correlation with test data for all modes of NiMnGa quasi-static behavior, capturing both the magnetic shape memory effect and pseudoelasticity. Furthermore, the model is also capable of predicting partial pseudoelasticity, minor hysteretic loops and stress-strain behaviors. To correct for the effects of magnetic saturation, a series of stress influence functions were developed from the critical stress profile. Although requiring further refinement, the model's results are encouraging, indicating that the model is a useful analytical tool for predicting NiMnGa actuator behavior.

  12. Use of a Ni60Ti shape memory alloy for active jet engine chevron application: II. Experimentally validated numerical analysis

    International Nuclear Information System (INIS)

    A shape memory alloy (SMA) composition of Ni60Ti40 (wt%) was chosen for the fabrication of active beam components used as cyclic actuators and incorporated into morphing aerospace structures. The active structure is a variable-geometry chevron (VGC) designed to reduce jet engine noise in the take-off flight regime while maintaining efficiency in the cruise regime. This two-part work addresses the training, characterization and derived material properties of the new nickel-rich NiTi composition, the assessment of the actuation properties of the active beam actuator and the accurate analysis of the VGC and its subcomponents using a model calibrated from the material characterization. The second part of this two-part work focuses on the numerical modeling of the jet engine chevron application, where the end goal is the accurate prediction of the VGC actuation response. A three-dimensional (3D) thermomechanical constitutive model is used for the analysis and is calibrated using the axial testing results from part I. To best capture the material response, features of several SMA constitutive models proposed in the literature are combined to form a new model that accounts for two material behaviors not previously addressed simultaneously. These are the variation in the generated maximum actuation strain with applied stress level and a smooth strain–temperature constitutive response at the beginning and end of transformation. The accuracy of the modeling effort is assessed by comparing the analysis deflection predictions for a given loading path imposed on the VGC or its subcomponents to independently obtained experimental results consisting of photogrammetric data. For the case of full actuation of the assembled VGC, the average error in predicted centerline deflection is less than 6%

  13. Molecular Basis for Enzymatic Sulfite Oxidation -- HOW THREE CONSERVED ACTIVE SITE RESIDUES SHAPE ENZYME ACTIVITY

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Susan; Rapson, Trevor; Johnson-Winters, Kayunta; Astashkin, Andrei; Enemark, John; Kappler, Ulrike

    2008-11-10

    Sulfite dehydrogenases (SDHs) catalyze the oxidation and detoxification of sulfite to sulfate, a reaction critical to all forms of life. Sulfite-oxidizing enzymes contain three conserved active site amino acids (Arg-55, His-57, and Tyr-236) that are crucial for catalytic competency. Here we have studied the kinetic and structural effects of two novel and one previously reported substitution (R55M, H57A, Y236F) in these residues on SDH catalysis. Both Arg-55 and His-57 were found to have key roles in substrate binding. An R55M substitution increased Km(sulfite)(app) by 2-3 orders of magnitude, whereas His-57 was required for maintaining a high substrate affinity at low pH when the imidazole ring is fully protonated. This effect may be mediated by interactions of His-57 with Arg-55 that stabilize the position of the Arg-55 side chain or, alternatively, may reflect changes in the protonation state of sulfite. Unlike what is seen for SDHWT and SDHY236F, the catalytic turnover rates of SDHR55M and SDHH57A are relatively insensitive to pH (~;;60 and 200 s-1, respectively). On the structural level, striking kinetic effects appeared to correlate with disorder (in SDHH57A and SDHY236F) or absence of Arg-55 (SDHR55M), suggesting that Arg-55 and the hydrogen bonding interactions it engages in are crucial for substrate binding and catalysis. The structure of SDHR55M has sulfate bound at the active site, a fact that coincides with a significant increase in the inhibitory effect of sulfate in SDHR55M. Thus, Arg-55 also appears to be involved in enabling discrimination between the substrate and product in SDH.

  14. Estimating Small-Body Gravity Field from Shape Model and Navigation Data

    Science.gov (United States)

    Park, Ryan S.; Werner, Robert A.; Bhaskaran, Shyam

    2008-01-01

    This paper presents a method to model the external gravity field and to estimate the internal density variation of a small-body. We first discuss the modeling problem, where we assume the polyhedral shape and internal density distribution are given, and model the body interior using finite elements definitions, such as cubes and spheres. The gravitational attractions computed from these approaches are compared with the true uniform-density polyhedral attraction and the level of accuracies are presented. We then discuss the inverse problem where we assume the body shape, radiometric measurements, and a priori density constraints are given, and estimate the internal density variation by estimating the density of each finite element. The result shows that the accuracy of the estimated density variation can be significantly improved depending on the orbit altitude, finite-element resolution, and measurement accuracy.

  15. 2-D IMAGE-BASED VOLUMETRIC MODELING FOR PARTICLE OF RANDOM SHAPE

    Institute of Scientific and Technical Information of China (English)

    Chen Ken; Larry E. Banta; Jiang Gangyi

    2006-01-01

    In this paper, an approach to predicting randomly-shaped particle volume based on its twoDimensional (2-D) digital image is explored. Conversion of gray-scale image of the particles to its binary counterpart is first performed using backlighting technique. The silhouette of particle is thus obtained, and consequently, informative features such as particle area, centroid and shape-related descriptors are collected. Several dimensionless parameters are defined, and used as regressor variables in a multiple linear regression model to predict particle volume. Regressor coefficients are found by fitting to a randomly selected sample of 501 particles ranging in size from 4.75mm to 25mm. The model testing experiment is conducted against a different aggregate sample of the similar statistical properties, the errors of the model-predicted volume of the batch is within ±2%.

  16. Pulmonary nodule detection in CT images based on shape constraint CV model

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bing; Tian, Xuedong [College of Mathematics and Computer Science, Hebei University, Baoding 071002 (China); Wang, Qian [Hebei Geological Laboratory, Baoding 071000, China and Multi-disciplinary Research Center, Hebei University, Baoding 071002 (China); Yang, Ying [Hebei University Affiliated Hospital, Baoding 071002 (China); Xie, Hongzhi, E-mail: gulixu@sjtu.edu.cn, E-mail: xiehongzhi@medmail.com.cn; Zhang, Shuyang [Department of Cardiology, Peking Union Medical College Hospital, Peking 100005 (China); Gu, Lixu, E-mail: gulixu@sjtu.edu.cn, E-mail: xiehongzhi@medmail.com.cn [Multi-disciplinary Research Center, Hebei University, Baoding 071002, China and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2015-03-15

    Purpose: Accurate detection of pulmonary nodules remains a technical challenge in computer-aided diagnosis systems because some nodules may adhere to the blood vessels or the lung wall, which have low contrast compared to the surrounding tissues. In this paper, the analysis of typical shape features of candidate nodules based on a shape constraint Chan–Vese (CV) model combined with calculation of the number of blood branches adhered to nodule candidates is proposed to reduce false positive (FP) nodules from candidate nodules. Methods: The proposed scheme consists of three major stages: (1) Segmentation of lung parenchyma from computed tomography images. (2) Extraction of candidate nodules. (3) Reduction of FP nodules. A gray level enhancement combined with a spherical shape enhancement filter is introduced to extract the candidate nodules and their sphere-like contour regions. FPs are removed by analysis of the typical shape features of nodule candidates based on the CV model using spherical constraint and by investigating the number of blood branches adhered to the candidate nodules. The constrained shapes of CV model are automatically achieved from the extracted candidate nodules. Results: The detection performance was evaluated on 127 nodules of 103 cases including three types of challenging nodules, which are juxta-pleural nodules, juxta-vascular nodules, and ground glass opacity nodules. The free-receiver operating characteristic (FROC) curve shows that the proposed method is able to detect 88% of all the nodules in the data set with 4 FPs per case. Conclusions: Evaluation shows that the authors’ method is feasible and effective for detection of three types of nodules in this study.

  17. INTERIOR MODELS OF SATURN: INCLUDING THE UNCERTAINTIES IN SHAPE AND ROTATION

    Energy Technology Data Exchange (ETDEWEB)

    Helled, Ravit [Department of Geophysics, Atmospheric and Planetary Sciences, Tel-Aviv University, Tel-Aviv (Israel); Guillot, Tristan [Universite de Nice-Sophia Antipolis, Observatoire de la Cote d' Azur, CNRS UMR 7293, BP 4229, F-06304 Nice (France)

    2013-04-20

    The accurate determination of Saturn's gravitational coefficients by Cassini could provide tighter constraints on Saturn's internal structure. Also, occultation measurements provide important information on the planetary shape which is often not considered in structure models. In this paper we explore how wind velocities and internal rotation affect the planetary shape and the constraints on Saturn's interior. We show that within the geodetic approach the derived physical shape is insensitive to the assumed deep rotation. Saturn's re-derived equatorial and polar radii at 100 mbar are found to be 54,445 {+-} 10 km and 60,365 {+-} 10 km, respectively. To determine Saturn's interior, we use one-dimensional three-layer hydrostatic structure models and present two approaches to include the constraints on the shape. These approaches, however, result in only small differences in Saturn's derived composition. The uncertainty in Saturn's rotation period is more significant: with Voyager's 10{sup h}39{sup m} period, the derived mass of heavy elements in the envelope is 0-7 M{sub Circled-Plus }. With a rotation period of 10{sup h}32{sup m}, this value becomes <4 M{sub Circled-Plus }, below the minimum mass inferred from spectroscopic measurements. Saturn's core mass is found to depend strongly on the pressure at which helium phase separation occurs, and is estimated to be 5-20 M{sub Circled-Plus }. Lower core masses are possible if the separation occurs deeper than 4 Mbar. We suggest that the analysis of Cassini's radio occultation measurements is crucial to test shape models and could lead to constraints on Saturn's rotation profile and departures from hydrostatic equilibrium.

  18. Hexagonal-shaped chondroitin sulfate self-assemblies have exalted anti-HSV-2 activity.

    Science.gov (United States)

    Galus, Aurélia; Mallet, Jean-Maurice; Lembo, David; Cagno, Valeria; Djabourov, Madeleine; Lortat-Jacob, Hugues; Bouchemal, Kawthar

    2016-01-20

    The initial step in mucosal infection by the herpes simplex virus type 2 (HSV-2) requires its binding to certain glycosaminoglycans naturally present on host cell membranes. We took advantage of this interaction to design biomimetic supramolecular hexagonal-shaped nanoassemblies composed of chondroitin sulfate having exalted anti-HSV-2 activity in comparison with native chondroitin sulfate. Nanoassemblies were formed by mixing hydrophobically-modified chondroitin sulfate with α-cyclodextrin in water. Optimization of alkyl chain length grafted on chondroitin sulfate and the ratio between hydrophobically-modified chondroitin sulfate and α-cyclodextrin showed that more cohesive and well-structured nanoassemblies were obtained using higher α-cyclodextrin concentration and longer alkyl chain lengths. A structure-activity relationship was found between anti-HSV-2 activity and the amphiphilic nature of hydrophobically-modified chondroitin sulfate. Also, antiviral activity of hexagonal nanoassemblies against HSV-2 was further improved in comparison with hydrophobically-modified chondroitin sulfate. This work suggests a new biomimetic formulation approach that can be extended to other heparan-sulfate-dependent viruses. PMID:26572336

  19. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account.

    Science.gov (United States)

    Imbir, Kamil K

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  20. Active Learning for Player Modeling

    DEFF Research Database (Denmark)

    Shaker, Noor; Abou-Zleikha, Mohamed; Shaker, Mohammad

    2015-01-01

    Learning models of player behavior has been the focus of several studies. This work is motivated by better understanding of player behavior, a knowledge that can ultimately be employed to provide player-adapted or personalized content. In this paper, we propose the use of active learning for player...... experience modeling. We use a dataset from hundreds of players playing Infinite Mario Bros. as a case study and we employ the random forest method to learn mod- els of player experience through the active learning approach. The results obtained suggest that only part of the dataset (up to half the size...

  1. Radar Shape Modeling of Binary Near-Earth Asteroid 2000 CO101

    Science.gov (United States)

    Jimenez, Nicholas; Howell, E. S.; Nolan, M. C.; Taylor, P. A.; Benner, L. A. M.; Brozovic, M.; Giorgini, J. D.; Vervack, R. J.; Fernandez, Y. R.; Mueller, M.; Margot, J.; Shepard, M. K.

    2010-10-01

    We observed the near-Earth binary system 2000 CO101 in 2009 September using the Goldstone and Arecibo radar systems and inverted these images to create shape models of the primary. Asteroid 2000 CO101 was discovered to be a binary system from Arecibo images taken on 2009 September 26 (Taylor et al. 2009). Analyzing the images, we were able to determine approximate values for the radius of the primary (310 m) and the radius of the secondary (22 m). The maximum observed range separation was approximately 610 m. The images show it to appear spherical. Shape modeling of the primary of this system will constrain the asteroid's size, spin rate, and pole orientation. Because other NEA binary systems have exhibited shapes similar to that of 1999 KW4 (Ostro et al. 2006, Scheeres et al. 2006), we initially adopted this shape for 2000 CO101 and have allowed only the linear scales along the three principal axes to adjust to the radar data. This enables us to constrain the volume. With some constraints on the orbit of the satellite we will place limits on the density of the primary. The near-infrared spectrum of 2000 CO101 was measured on 2009 September 21 and 2010 March 13. The 0.8-2.5 micron spectrum was measured on both dates, and shows a featureless, red-sloped spectrum. On September 21 we also measured the thermal emission between 2-4 microns to determine the albedo and thermal properties. Both standard thermal models and thermophysical models have been applied to these data. The albedo we derive from the thermal modeling must also be consistent with the radar size. Characterization of this unusual NEA binary system will be presented.

  2. Adaptive Shape Functions and Internal Mesh Adaptation for Modelling Progressive Failure in Adhesively Bonded Joints

    Science.gov (United States)

    Stapleton, Scott; Gries, Thomas; Waas, Anthony M.; Pineda, Evan J.

    2014-01-01

    Enhanced finite elements are elements with an embedded analytical solution that can capture detailed local fields, enabling more efficient, mesh independent finite element analysis. The shape functions are determined based on the analytical model rather than prescribed. This method was applied to adhesively bonded joints to model joint behavior with one element through the thickness. This study demonstrates two methods of maintaining the fidelity of such elements during adhesive non-linearity and cracking without increasing the mesh needed for an accurate solution. The first method uses adaptive shape functions, where the shape functions are recalculated at each load step based on the softening of the adhesive. The second method is internal mesh adaption, where cracking of the adhesive within an element is captured by further discretizing the element internally to represent the partially cracked geometry. By keeping mesh adaptations within an element, a finer mesh can be used during the analysis without affecting the global finite element model mesh. Examples are shown which highlight when each method is most effective in reducing the number of elements needed to capture adhesive nonlinearity and cracking. These methods are validated against analogous finite element models utilizing cohesive zone elements.

  3. Using Students' Science Ideas to Drive Instruction: How Responsive Teaching Shapes Learning Activity

    Science.gov (United States)

    Canavesi, Cristina

    Teaching in a way that is responsive to students' science ideas creates opportunities for meaningful, rigorous sense-making in a way that traditional science teaching does not. In this study, the researcher, as a visiting teacher, taught the same three-week circuits unit to one fourth grade class and two fifth grade classes from a responsive teaching stance. The teachers' attention to and incorporation of students' science ideas shifted unit trajectories and uniquely shaped the ongoing learning activity within whole-group discourse. A unit-level analysis of the frequency and category of science concepts present in whole-group discourse shows that all three classes discussed the same science concepts by the end of the unit; however, when these ideas presented themselves within whole group discourse differed across time, even though students were engaged in the same lessons. Tensions and dilemmas of responsive science teaching are discussed.

  4. A simplified compact model of miniaturized cross-shaped CMOS integrated Hall devices

    Institute of Scientific and Technical Information of China (English)

    Huang Haiyun; Wang Dejun; Li Wenbo; Xu Yue; Qin Huibin; Hu Yongcai

    2012-01-01

    A simplified compact model for a miniaturized cross-shaped CMOS integrated Hall device is presented.The model has a simple circuit structure,only consisting of a passive network with eight non-linear resistors and four current-controlled voltage sources.It completely considers the following effects:non-linear conductivity,geometry dependence of sensitivity,temperature drift,lateral diffusion,and junction field effect.The model has been implemented in Verilog-A hardware description language and was successfully performed in a Cadence Spectre simulator.The simulation results are in good accordance with the classic experimental results reported in the literature.

  5. Modelling stochastic chances in curve shape, with an application to cancer diagnostics

    DEFF Research Database (Denmark)

    Hobolth, A; Jensen, Eva B. Vedel

    2000-01-01

    Often, the statistical analysis of the shape of a random planar curve is based on a model for a polygonal approximation to the curve. In the present paper, we instead describe the curve as a continuous stochastic deformation of a template curve. The advantage of this continuous approach...... is that the parameters in the model do not relate to a particular polygonal approximation. A somewhat similar approach has been used by Kent et al. (1996), who describe the limiting behaviour of a model with a first-order Markov property as the landmarks on the curve become closely spaced; see also Grenander(1993...

  6. Modeling the Pulse Signal by Wave-Shape Function and Analyzing by Synchrosqueezing Transform.

    Directory of Open Access Journals (Sweden)

    Hau-Tieng Wu

    Full Text Available We apply the recently developed adaptive non-harmonic model based on the wave-shape function, as well as the time-frequency analysis tool called synchrosqueezing transform (SST to model and analyze oscillatory physiological signals. To demonstrate how the model and algorithm work, we apply them to study the pulse wave signal. By extracting features called the spectral pulse signature, and based on functional regression, we characterize the hemodynamics from the radial pulse wave signals recorded by the sphygmomanometer. Analysis results suggest the potential of the proposed signal processing approach to extract health-related hemodynamics features.

  7. Modeling the Pulse Signal by Wave-Shape Function and Analyzing by Synchrosqueezing Transform

    Science.gov (United States)

    Wang, Chun-Li; Yang, Yueh-Lung; Wu, Wen-Hsiang; Tsai, Tung-Hu; Chang, Hen-Hong

    2016-01-01

    We apply the recently developed adaptive non-harmonic model based on the wave-shape function, as well as the time-frequency analysis tool called synchrosqueezing transform (SST) to model and analyze oscillatory physiological signals. To demonstrate how the model and algorithm work, we apply them to study the pulse wave signal. By extracting features called the spectral pulse signature, and based on functional regression, we characterize the hemodynamics from the radial pulse wave signals recorded by the sphygmomanometer. Analysis results suggest the potential of the proposed signal processing approach to extract health-related hemodynamics features. PMID:27304979

  8. A phenomenological two-phase constitutive model for porous shape memory alloys

    KAUST Repository

    El Sayed, Tamer S.

    2012-07-01

    We present a two-phase constitutive model for pseudoelastoplastic behavior of porous shape memory alloys (SMAs). The model consists of a dense SMA phase and a porous plasticity phase. The overall response of the porous SMA is obtained by a weighted average of responses of individual phases. Based on the chosen constitutive model parameters, the model incorporates the pseudoelastic and pseudoplastic behavior simultaneously (commonly reported for porous SMAs) as well as sequentially (i.e. dense SMAs; pseudoelastic deformation followed by the pseudoplastic deformation until failure). The presented model also incorporates failure due to the deviatoric (shear band formation) and volumetric (void growth and coalescence) plastic deformation. The model is calibrated by representative volume elements (RVEs) with different sizes of spherical voids that are solved by unit cell finite element calculations. The overall response of the model is tested against experimental results from literature. Finally, application of the presented constitutive model has been presented by performing finite element simulations of the deformation and failure in unaixial dog-bone shaped specimen and compact tension (CT) test specimen. Results show a good agreement with the experimental data reported in the literature. © 2012 Elsevier B.V. All rights reserved.

  9. Design and Control of a Proof-of-Concept Active Jet Engine Intake Using Shape Memory Alloy Actuators

    Science.gov (United States)

    Song, Gangbing; Ma, Ning; Penney, Nicholas; Barr, Todd; Lee, Ho-Jun; Arnold, Steven M.

    2004-01-01

    The design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators is used to demonstrate the potential of an adaptive intake to improve the fuel efficiency of a jet engine. The Nitinol SMA material is selected for this research due to the material's ability to generate large strains of up to 5 percent for repeated operations, a high power-to-weight ratio, electrical resistive actuation, and easy fabrication into a variety of shapes. The proof-of-concept engine intake employs an overlapping leaf design arranged in a concentric configuration. Each leaf is mounted on a supporting bar that rotates upon actuation by SMA wires electrical resistive heating. Feedback control is enabled through the use of a laser range sensor to detect the movement of a leaf and determine the radius of the intake area. Due to the hysteresis behavior inherent in SMAs, a nonlinear robust controller is used to direct the SMA wire actuation. The controller design utilizes the sliding-mode approach to compensate for the nonlinearities associated with the SMA actuator. Feedback control experiments conducted on a fabricated proof-of-concept model have demonstrated the capability to precisely control the intake area and achieve up to a 25 percent reduction in intake area. The experiments demonstrate the feasibility of engine intake area control using the proposed design.

  10. Bacterial proteasome activator bpa (rv3780 is a novel ring-shaped interactor of the mycobacterial proteasome.

    Directory of Open Access Journals (Sweden)

    Cyrille L Delley

    Full Text Available The occurrence of the proteasome in bacteria is limited to the phylum of actinobacteria, where it is maintained in parallel to the usual bacterial compartmentalizing proteases. The role it plays in these organisms is still not fully understood, but in the human pathogen Mycobacterium tuberculosis (Mtb the proteasome supports persistence in the host. In complex with the ring-shaped ATPase Mpa (called ARC in other actinobacteria, the proteasome can degrade proteins that have been post-translationally modified with the prokaryotic ubiquitin-like protein Pup. Unlike for the eukaryotic proteasome core particle, no other bacterial proteasome interactors have been identified to date. Here we describe and characterize a novel bacterial proteasome activator of Mycobacterium tuberculosis we termed Bpa (Rv3780, using a combination of biochemical and biophysical methods. Bpa features a canonical C-terminal proteasome interaction motif referred to as the HbYX motif, and its orthologs are only found in those actinobacteria encoding the proteasomal subunits. Bpa can inhibit degradation of Pup-tagged substrates in vitro by competing with Mpa for association with the proteasome. Using negative-stain electron microscopy, we show that Bpa forms a ring-shaped homooligomer that can bind coaxially to the face of the proteasome cylinder. Interestingly, Bpa can stimulate the proteasomal degradation of the model substrate β-casein, which suggests it could play a role in the removal of non-native or damaged proteins.

  11. Bacterial proteasome activator bpa (rv3780) is a novel ring-shaped interactor of the mycobacterial proteasome.

    Science.gov (United States)

    Delley, Cyrille L; Laederach, Juerg; Ziemski, Michal; Bolten, Marcel; Boehringer, Daniel; Weber-Ban, Eilika

    2014-01-01

    The occurrence of the proteasome in bacteria is limited to the phylum of actinobacteria, where it is maintained in parallel to the usual bacterial compartmentalizing proteases. The role it plays in these organisms is still not fully understood, but in the human pathogen Mycobacterium tuberculosis (Mtb) the proteasome supports persistence in the host. In complex with the ring-shaped ATPase Mpa (called ARC in other actinobacteria), the proteasome can degrade proteins that have been post-translationally modified with the prokaryotic ubiquitin-like protein Pup. Unlike for the eukaryotic proteasome core particle, no other bacterial proteasome interactors have been identified to date. Here we describe and characterize a novel bacterial proteasome activator of Mycobacterium tuberculosis we termed Bpa (Rv3780), using a combination of biochemical and biophysical methods. Bpa features a canonical C-terminal proteasome interaction motif referred to as the HbYX motif, and its orthologs are only found in those actinobacteria encoding the proteasomal subunits. Bpa can inhibit degradation of Pup-tagged substrates in vitro by competing with Mpa for association with the proteasome. Using negative-stain electron microscopy, we show that Bpa forms a ring-shaped homooligomer that can bind coaxially to the face of the proteasome cylinder. Interestingly, Bpa can stimulate the proteasomal degradation of the model substrate β-casein, which suggests it could play a role in the removal of non-native or damaged proteins. PMID:25469515

  12. Input Shaping enhanced Active Disturbance Rejection Control for a twin rotor multi-input multi-output system (TRMS).

    Science.gov (United States)

    Yang, Xiaoyan; Cui, Jianwei; Lao, Dazhong; Li, Donghai; Chen, Junhui

    2016-05-01

    In this paper, a composite control based on Active Disturbance Rejection Control (ADRC) and Input Shaping is presented for TRMS with two degrees of freedom (DOF). The control tasks consist of accurately tracking desired trajectories and obtaining disturbance rejection in both horizontal and vertical planes. Due to un-measurable states as well as uncertainties stemming from modeling uncertainty and unknown disturbance torques, ADRC is employed, and feed-forward Input Shaping is used to improve the dynamical response. In the proposed approach, because the coupling effects are maintained in controller derivation, there is no requirement to decouple the TRMS into horizontal and vertical subsystems, which is usually performed in the literature. Finally, the proposed method is implemented on the TRMS platform, and the results are compared with those of PID and ADRC in a similar structure. The experimental results demonstrate the effectiveness of the proposed method. The operation of the controller allows for an excellent set-point tracking behavior and disturbance rejection with system nonlinearity and complex coupling conditions.

  13. Automatic Segmentation of Wrist Bones in CT Using a Statistical Wrist Shape + Pose Model.

    Science.gov (United States)

    Anas, Emran Mohammad Abu; Rasoulian, Abtin; Seitel, Alexander; Darras, Kathryn; Wilson, David; John, Paul St; Pichora, David; Mousavi, Parvin; Rohling, Robert; Abolmaesumi, Purang

    2016-08-01

    Segmentation of the wrist bones in CT images has been frequently used in different clinical applications including arthritis evaluation, bone age assessment and image-guided interventions. The major challenges include non-uniformity and spongy textures of the bone tissue as well as narrow inter-bone spaces. In this work, we propose an automatic wrist bone segmentation technique for CT images based on a statistical model that captures the shape and pose variations of the wrist joint across 60 example wrists at nine different wrist positions. To establish the correspondences across the training shapes at neutral positions, the wrist bone surfaces are jointly aligned using a group-wise registration framework based on a Gaussian Mixture Model. Principal component analysis is then used to determine the major modes of shape variations. The variations in poses not only across the population but also across different wrist positions are incorporated in two pose models. An intra-subject pose model is developed by utilizing the similarity transforms at all wrist positions across the population. Further, an inter-subject pose model is used to model the pose variations across different wrist positions. For segmentation of the wrist bones in CT images, the developed model is registered to the edge point cloud extracted from the CT volume through an expectation maximization based probabilistic approach. Residual registration errors are corrected by application of a non-rigid registration technique. We validate the proposed segmentation method by registering the wrist model to a total of 66 unseen CT volumes of average voxel size of 0.38 mm. We report a mean surface distance error of 0.33 mm and a mean Jaccard index of 0.86. PMID:26890640

  14. Use of Image Based Modelling for Documentation of Intricately Shaped Objects

    Science.gov (United States)

    Marčiš, M.; Barták, P.; Valaška, D.; Fraštia, M.; Trhan, O.

    2016-06-01

    In the documentation of cultural heritage, we can encounter three dimensional shapes and structures which are complicated to measure. Such objects are for example spiral staircases, timber roof trusses, historical furniture or folk costume where it is nearly impossible to effectively use the traditional surveying or the terrestrial laser scanning due to the shape of the object, its dimensions and the crowded environment. The actual methods of digital photogrammetry can be very helpful in such cases with the emphasis on the automated processing of the extensive image data. The created high resolution 3D models and 2D orthophotos are very important for the documentation of architectural elements and they can serve as an ideal base for the vectorization and 2D drawing documentation. This contribution wants to describe the various usage of image based modelling in specific interior spaces and specific objects. The advantages and disadvantages of the photogrammetric measurement of such objects in comparison to other surveying methods are reviewed.

  15. IMC-PID design based on model matching approach and closed-loop shaping.

    Science.gov (United States)

    Jin, Qi B; Liu, Q

    2014-03-01

    Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability.

  16. Quantitative model for the generic 3D shape of ICMEs at 1 AU

    CERN Document Server

    Démoulin, P; Masías-Meza, J J; Dasso, S

    2016-01-01

    Interplanetary imagers provide 2D projected views of the densest plasma parts of interplanetary coronal mass ejections (ICMEs) while in situ measurements provide magnetic field and plasma parameter measurements along the spacecraft trajectory, so along a 1D cut. As such, the data only give a partial view of their 3D structures. By studying a large number of ICMEs, crossed at different distances from their apex, we develop statistical methods to obtain a quantitative generic 3D shape of ICMEs. In a first approach we theoretically obtain the expected statistical distribution of the shock-normal orientation from assuming simple models of 3D shock shapes, including distorted profiles, and compare their compatibility with observed distributions. In a second approach we use the shock normal and the flux rope axis orientations, as well as the impact parameter, to provide statistical information across the spacecraft trajectory. The study of different 3D shock models shows that the observations are compatible with a ...

  17. A structured continuum modelling framework for martensitic transformation and reorientation in shape memory materials.

    Science.gov (United States)

    Bernardini, Davide; Pence, Thomas J

    2016-04-28

    Models for shape memory material behaviour can be posed in the framework of a structured continuum theory. We study such a framework in which a scalar phase fraction field and a tensor field of martensite reorientation describe the material microstructure, in the context of finite strains. Gradients of the microstructural descriptors naturally enter the formulation and offer the possibility to describe and resolve phase transformation localizations. The constitutive theory is thoroughly described by a single free energy function in conjunction with a path-dependent dissipation function. Balance laws in the form of differential equations are obtained and contain both bulk and surface terms, the latter in terms of microstreses. A natural constraint on the tensor field for martensite reorientation gives rise to reactive fields in these balance laws. Conditions ensuring objectivity as well as the relation of this framework to that provided by currently used models for shape memory alloy behaviour are discussed.

  18. IMC-PID design based on model matching approach and closed-loop shaping.

    Science.gov (United States)

    Jin, Qi B; Liu, Q

    2014-03-01

    Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability. PMID:24280534

  19. Modelling of the non isothermal cyclic behaviour of a polycrystalline Cu Zn Al shape memory alloy

    International Nuclear Information System (INIS)

    In this paper, a model describing the behaviour of Shape Memory Alloys (SMA) under constant applied stress and thermal cycling is developed. This is the first (and necessary) step to obtain a coherent modelling of the well-known Two Way Shape Memory Effect (TWSME) exhibited by SMA after a training process. Two different mechanisms characteristic to SMA are involved in the present description. The first one is related to training itself, whose macroscopic manifestation is the appearance of a permanent strain. The second one concerns the response of SMA to non-isothermal loading. It can be solved by the introduction of news variables in the internal variables set. There are the volume fraction of self-accommodating martensite (pure thermal effect) and the volume fraction of ''oriented'' martensite (thermo-mechanical effect). The comparison between simulation and our experimental results on Cu Zn Al polycrystals is fairly good. (orig.)

  20. Optimal input shaping for Fisher identifiability of control-oriented lithium-ion battery models

    Science.gov (United States)

    Rothenberger, Michael J.

    This dissertation examines the fundamental challenge of optimally shaping input trajectories to maximize parameter identifiability of control-oriented lithium-ion battery models. Identifiability is a property from information theory that determines the solvability of parameter estimation for mathematical models using input-output measurements. This dissertation creates a framework that exploits the Fisher information metric to quantify the level of battery parameter identifiability, optimizes this metric through input shaping, and facilitates faster and more accurate estimation. The popularity of lithium-ion batteries is growing significantly in the energy storage domain, especially for stationary and transportation applications. While these cells have excellent power and energy densities, they are plagued with safety and lifespan concerns. These concerns are often resolved in the industry through conservative current and voltage operating limits, which reduce the overall performance and still lack robustness in detecting catastrophic failure modes. New advances in automotive battery management systems mitigate these challenges through the incorporation of model-based control to increase performance, safety, and lifespan. To achieve these goals, model-based control requires accurate parameterization of the battery model. While many groups in the literature study a variety of methods to perform battery parameter estimation, a fundamental issue of poor parameter identifiability remains apparent for lithium-ion battery models. This fundamental challenge of battery identifiability is studied extensively in the literature, and some groups are even approaching the problem of improving the ability to estimate the model parameters. The first approach is to add additional sensors to the battery to gain more information that is used for estimation. The other main approach is to shape the input trajectories to increase the amount of information that can be gained from input

  1. Titanium-Nickel Shape Memory Alloy Spring Actuator for Forward-Looking Active Catheter

    Directory of Open Access Journals (Sweden)

    Takahiro Namazu

    2011-01-01

    Full Text Available The fabrication and characterization of forward-looking active catheter actuated by titanium-nickel (Ti-Ni shape memory alloy (SMA springs are described. The catheter has been designed for wide-range observation of an affected area inside a blood vessel when the blood vessel is occluded. The developed active catheter consists of eight Ti-Ni SMA spring actuators for actuation of catheter tip, an ultrasonic transducer for forward-looking, a guide wire, a polyurethane tube for coating, and spiral wirings for realization of various flexure motions of catheter tip using Ti-Ni SMA actuators. The size of the catheter is 3.5 mm in diameter and 60 mm in length of the sum of transducer and actuator sections. Ti-Ni SMA springs were fabricated from a Ti-50.9at.%Ni sheet by electrochemical etching with a mixed solution of ethanol and lithium chloride. The catheter was assembled by hand under a stereomicroscope. The tip of the produced catheter was able to move in parallel toward at least eight directions by controlling an applied current to Ti-Ni SMA springs. We have confirmed that the active catheter was able to observe an object settled in the front.

  2. Shaping prestimulus neural activity with auditory rhythmic stimulation improves the temporal allocation of attention

    Science.gov (United States)

    Pincham, Hannah L.; Cristoforetti, Giulia; Facoetti, Andrea; Szűcs, Dénes

    2016-01-01

    Human attention fluctuates across time, and even when stimuli have identical physical characteristics and the task demands are the same, relevant information is sometimes consciously perceived and at other times not. A typical example of this phenomenon is the attentional blink, where participants show a robust deficit in reporting the second of two targets (T2) in a rapid serial visual presentation (RSVP) stream. Previous electroencephalographical (EEG) studies showed that neural correlates of correct T2 report are not limited to the RSVP period, but extend before visual stimulation begins. In particular, reduced oscillatory neural activity in the alpha band (8-12 Hz) before the onset of the RSVP has been linked to lower T2 accuracy. We therefore examined whether auditory rhythmic stimuli presented at a rate of 10 Hz (within the alpha band) could increase oscillatory alpha-band activity and improve T2 performance in the attentional blink time window. Behaviourally, the auditory rhythmic stimulation worked to enhance T2 accuracy. This enhanced perception was associated with increases in the posterior T2-evoked N2 component of the event-related potentials and this effect was observed selectively at lag 3. Frontal and posterior oscillatory alpha-band activity was also enhanced during auditory stimulation in the pre-RSVP period and positively correlated with T2 accuracy. These findings suggest that ongoing fluctuations can be shaped by sensorial events to improve the allocation of attention in time. PMID:26986506

  3. Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

    OpenAIRE

    Kun-Dar Li; Kwanyu Chen

    2015-01-01

    In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion do...

  4. Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia

    Science.gov (United States)

    Carry, B.; Kaasalainen, M.; Merline, W. J.; Müller, T. G.; Jorda, L.; Drummond, J. D.; Berthier, J.; O'Rourke, L.; Ďurech, J.; Küppers, M.; Conrad, A.; Tamblyn, P.; Dumas, C.; Sierks, H.; Osiris Team

    2012-06-01

    We present here a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. Knowledge of certain observable physical properties of small bodies (e.g., size, spin, 3-D shape, and density) have far-reaching implications in furthering our understanding of these objects, such as composition, internal structure, and the effects of non-gravitational forces. We review the different observing techniques used to determine the above physical properties of asteroids and present our 3-D shape-modeling technique KOALA - Knitted Occultation, Adaptive-optics, and Lightcurve Analysis - which is based on multi-dataset inversion. We compare the results we obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with the high-spatial resolution images of the asteroid taken with the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter with Lutetia on 2010 July 10. The spin axis determined with KOALA was found to be accurate to within 2°, while the KOALA diameter determinations were within 2% of the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed by the spectacular visual agreement between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We found a typical deviation of only 2 km at local scales between the profiles from KOALA predictions and OSIRIS images, resulting in a volume uncertainty provided by KOALA better than 10%. Radiometric techniques for the interpretation of thermal infrared data also benefit greatly from the KOALA shape model: the absolute size and geometric albedo can be derived with high accuracy, and thermal properties, for example the thermal inertia, can be determined unambiguously. The corresponding Lutetia analysis leads

  5. Automatic Sex Determination of Skulls Based on a Statistical Shape Model

    Directory of Open Access Journals (Sweden)

    Li Luo

    2013-01-01

    Full Text Available Sex determination from skeletons is an important research subject in forensic medicine. Previous skeletal sex assessments are through subjective visual analysis by anthropologists or metric analysis of sexually dimorphic features. In this work, we present an automatic sex determination method for 3D digital skulls, in which a statistical shape model for skulls is constructed, which projects the high-dimensional skull data into a low-dimensional shape space, and Fisher discriminant analysis is used to classify skulls in the shape space. This method combines the advantages of metrical and morphological methods. It is easy to use without professional qualification and tedious manual measurement. With a group of Chinese skulls including 127 males and 81 females, we choose 92 males and 58 females to establish the discriminant model and validate the model with the other skulls. The correct rate is 95.7% and 91.4% for females and males, respectively. Leave-one-out test also shows that the method has a high accuracy.

  6. Transient flow model and pressure dynamic features of tree-shaped fractal re- servoirs

    Institute of Scientific and Technical Information of China (English)

    TAN Xiao-hua; LI Xiao-ping

    2014-01-01

    A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the tree-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch numberN, the length ratioα, and the branch angleθ. The diameter ratioβ has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch levelM of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.

  7. A STUDY FOR THE MATHEMATIC MODELING OF 2D IRREGULAR SHAPES FOR FOOTWEAR CAD SYSTEM

    Directory of Open Access Journals (Sweden)

    DRIŞCU Mariana

    2015-05-01

    Full Text Available For using a specialized footwear CAD system it's imperative to know the analytical expression of the outlines of the footwear patterns. This brings us to the field of mathematical modeling. Mathematic modeling is based on the equation of the function defining the outline of the model contour. Shapes, contours cannot be identified, in designing, by simple function of the form y=f(x, because most of them have irregular forms, with many concavities and convexities, which explains why their form is intrinsically dependent on the coordinates system. For example, if we want to plot a curve, it is absolutely necessary that we choose the right set of contour points in a system of coordinates, but the important factor in determining the form of the object is the relation between these points, not that between the points and the randomly chosen coordinates system. Further more, the contour forms may have vertical tangents. If the shape were represented by a function y=f(x, the vertical tangents would be an inconvenient in designing, which might be avoided by an approximation of analytic function (e.g. of polynomials For all these reasons, the dominant representation of shapes in CAD is not possible a function y=f(x but a set of function which can be obtained on various portions. This paper presents a study regarding the interpolation of the footwear components and outlines contours and the graphic visualization, using the following methods: Lagrange, B-Spline, Bezier.

  8. Assessment of left ventricular function parameters with a new three-dimensional shape model

    Energy Technology Data Exchange (ETDEWEB)

    Bansmann, P.M.; Lund, G.; Kemper, J.; Adam, G.; Stork, A. [Universitaetsklinikum Hamburg, Eppendorf (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie; Senegas, J. [Philips Research Europe (Germany); Muellerleile, K. [Universitaetsklinikum Hamburg, Eppendorf (Germany). Klinik und Poliklinik fuer Kardiologie/Angiologie

    2009-02-15

    To evaluate a 3D model of the left ventricle (LV) which allows calculation of LV function parameters on the basis of both short axis (SA) and long axis (LA) cine acquisitions. Comparison with the conventional Simpson's rule method in a volunteer and patient collective. Cine imaging was performed with a prospectively triggered SSFP sequence: trueFISP: TR 3.6 msec, TE 1.8 msec, bFFE: TR 3.0 msec, TE 1.4 msec, flip angle 60 , resolution 1.37 x 1.37 mm, slice thickness 8 mm, gap 2 mm in SA orientation from apex to basis and in radial LA orientation (spacing 15 ) in 11 volunteers and 27 patients with mitral valve insufficiency. Five different volume computations were compared: Simpson's rule based on all SA slices (M0), 3D shape model based on all SA slices (M1a), 3D shape model based on 3 SA slices (M1b), 3D shape model based on all SA and LA slices (M2a), and 3D shape model based on 3 SA slices and 1 LA slice (M2b). M 0 and M 1a give similar results (r: 0.99, b: 0.98). M 2a produces larger volumes than M 0 (b: 0.85) due to the inclusion of the LA contours. M 1b effectively reproduces the volumes computed with M 0 (r: 0.99, b: 1.02). M 2b effectively reproduces the volumes computed with M 2a (r: 0.99, b: 0.94). M 2b and M 0 give similar results in the patient collective (r: 0.99, b: 0.97). The proposed 3D shape model allows merging of information acquired in different orientations and thus the combination of SA and LA contours with better coverage of the left ventricle. It provides a suitable fit with a reduced number of segmented contours. (orig.)

  9. Biological models for active vision: Towards a unified architecture

    OpenAIRE

    Terzic K.; Lobato D.; Saleiro M.; Martins J; Farrajota M.; Rodrigues J.M.F.; Du Buf J.M.H.

    2013-01-01

    Building a general-purpose, real-time active vision system completely based on biological models is a great challenge. We apply a number of biologically plausible algorithms which address different aspects of vision, such as edge and keypoint detection, feature extraction,optical flow and disparity, shape detection, object recognition and scene modelling into a complete system. We present some of the experiments from our ongoing work, where our system leverages a combination of algorithms to ...

  10. The contents of predictions in sentence comprehension: activation of the shape of objects before they are referred to

    NARCIS (Netherlands)

    Rommers, J.; Meyer, A.S.; Praamstra, P.; Hüttig, F.

    2013-01-01

    When comprehending concrete words, listeners and readers can activate specific visual information such as the shape of the words' referents. In two experiments we examined whether such information can be activated in an anticipatory fashion. In Experiment 1, listeners' eye movements were tracked whi

  11. The shape of the Aegean MCC's, Insights from 3D numerical modelling

    Science.gov (United States)

    Le Pourhiet, L.; Denèle, Y.; Huet, B.; Jolivet, L.

    2010-12-01

    The Aegean sea is a back arc basin in which the continental lithosphere has been stretched through the tertiary leaving several diachronous belts of Metamorphic Core Complexes (MCCs). The Aegean MCCs present two classes of shapes. Some are elongated in the direction of the lineation (A-type e.g. Naxos, Paros..) while the others are elongated in a direction normal to the lineation (B-type e.g. Tinos, Evvia ...). While it is well established from 1 and 2D modeling that MCC's forms when the lower crust is weak, the reason for the diversity of shape remains an open question. The A-type domes are not only elongated in shape; their P-T-t paths indicate a clear phase of warming during the exhumation and they also present migmatites (which are not observed in the other islands). Several hypothesis may be drawn. The elongated domes could result from 1) the competition of boudinage versus normal constriction folding, 2) lateral variation of the thickness or the temperature of the crust resulting in local buoyant instability (R-T instability) or 3) lateral gradient of deformation. This contribution presents the preliminary results obtained with thermo-mechanical models in which we test the influence of a local plutonic intrusions, along strike variation of extensional rate, and lateral boundary condition (normal shortening or extension) on the shape of the domes. As this problem is inherently three dimensional, the models were computed on our computer cluster using Gale/Underworld an ALE method with visco-plastic temperature dependent rheologies.

  12. Does shape discrimination by the mouth activate the parietal and occipital lobes? - near-infrared spectroscopy study.

    Directory of Open Access Journals (Sweden)

    Tomonori Kagawa

    Full Text Available A cross-modal association between somatosensory tactile sensation and parietal and occipital activities during Braille reading was initially discovered in tests with blind subjects, with sighted and blindfolded healthy subjects used as controls. However, the neural background of oral stereognosis remains unclear. In the present study, we investigated whether the parietal and occipital cortices are activated during shape discrimination by the mouth using functional near-infrared spectroscopy (fNIRS. Following presentation of the test piece shape, a sham discrimination trial without the test pieces induced posterior parietal lobe (BA7, extrastriate cortex (BA18, BA19, and striate cortex (BA17 activation as compared with the rest session, while shape discrimination of the test pieces markedly activated those areas as compared with the rest session. Furthermore, shape discrimination of the test pieces specifically activated the posterior parietal cortex (precuneus/BA7, extrastriate cortex (BA18, 19, and striate cortex (BA17, as compared with sham sessions without a test piece. We concluded that oral tactile sensation is recognized through tactile/visual cross-modal substrates in the parietal and occipital cortices during shape discrimination by the mouth.

  13. Comparison of Two Methods Used to Model Shape Parameters of Pareto Distributions

    Science.gov (United States)

    Liu, C.; Charpentier, R.R.; Su, J.

    2011-01-01

    Two methods are compared for estimating the shape parameters of Pareto field-size (or pool-size) distributions for petroleum resource assessment. Both methods assume mature exploration in which most of the larger fields have been discovered. Both methods use the sizes of larger discovered fields to estimate the numbers and sizes of smaller fields: (1) the tail-truncated method uses a plot of field size versus size rank, and (2) the log-geometric method uses data binned in field-size classes and the ratios of adjacent bin counts. Simulation experiments were conducted using discovered oil and gas pool-size distributions from four petroleum systems in Alberta, Canada and using Pareto distributions generated by Monte Carlo simulation. The estimates of the shape parameters of the Pareto distributions, calculated by both the tail-truncated and log-geometric methods, generally stabilize where discovered pool numbers are greater than 100. However, with fewer than 100 discoveries, these estimates can vary greatly with each new discovery. The estimated shape parameters of the tail-truncated method are more stable and larger than those of the log-geometric method where the number of discovered pools is more than 100. Both methods, however, tend to underestimate the shape parameter. Monte Carlo simulation was also used to create sequences of discovered pool sizes by sampling from a Pareto distribution with a discovery process model using a defined exploration efficiency (in order to show how biased the sampling was in favor of larger fields being discovered first). A higher (more biased) exploration efficiency gives better estimates of the Pareto shape parameters. ?? 2011 International Association for Mathematical Geosciences.

  14. Modeling of the shape of infrared stimulated luminescence signals in feldspars

    DEFF Research Database (Denmark)

    Pagonis, Vasilis; Jain, Mayank; Murray, Andrew S.;

    2012-01-01

    This paper presents a new empirical model describing infrared (IR) stimulation phenomena in feldspars. In the model electrons from the ground state of an electron trap are raised by infrared optical stimulation to the excited state, and subsequently recombine with a nearest-neighbor hole via...... that the shape of the IRSL curves does not change significantly under different experimental conditions. The relationship between the simulated IRSL signal and the well-known power-law dependence of relaxation processes in solids is also explored, by fitting the IRSL signal at long times with a power-law type...

  15. Atomically thin spherical shell-shaped superscatterers based on a Bohr model.

    Science.gov (United States)

    Li, Rujiang; Lin, Xiao; Lin, Shisheng; Liu, Xu; Chen, Hongsheng

    2015-12-18

    Graphene monolayers can be used for atomically thin three-dimensional shell-shaped superscatterer designs. Due to the excitation of the first-order resonance of transverse magnetic (TM) graphene plasmons, the scattering cross section of the bare subwavelength dielectric particle is enhanced significantly by five orders of magnitude. The superscattering phenomenon can be intuitively understood and interpreted with a Bohr model. In addition, based on the analysis of the Bohr model, it is shown that contrary to the TM case, superscattering is hard to achieve by exciting the resonance of transverse electric (TE) graphene plasmons due to their poor field confinements.

  16. Atomically thin spherical shell-shaped superscatterers based on Bohr model

    CERN Document Server

    Li, Rujiang; Lin, Shisheng; Liu, Xu; Chen, Hongsheng

    2015-01-01

    Graphene monolayers can be used for atomically thin three-dimensional shell-shaped superscatterer designs. Due to the excitation of the first-order resonance of transverse magnetic (TM) graphene plasmons, the scattering cross section of the bare subwavelength dielectric particle is enhanced significantly by five orders of magnitude. The superscattering phenomenon can be intuitively understood and interpreted with Bohr model. Besides, based on the analysis of Bohr model, it is shown that contrary to the TM case, superscattering is hard to occur by exciting the resonance of transverse electric (TE) graphene plasmons due to their poor field confinements.

  17. Calibration and Finite Element Implementation of an Energy-Based Material Model for Shape Memory Alloys

    Science.gov (United States)

    Junker, Philipp; Hackl, Klaus

    2016-06-01

    Numerical simulations are a powerful tool to analyze the complex thermo-mechanically coupled material behavior of shape memory alloys during product engineering. The benefit of the simulations strongly depends on the quality of the underlying material model. In this contribution, we discuss a variational approach which is based solely on energetic considerations and demonstrate that unique calibration of such a model is sufficient to predict the material behavior at varying ambient temperature. In the beginning, we recall the necessary equations of the material model and explain the fundamental idea. Afterwards, we focus on the numerical implementation and provide all information that is needed for programing. Then, we show two different ways to calibrate the model and discuss the results. Furthermore, we show how this model is used during real-life industrial product engineering.

  18. Somatostatin and Somatostatin-Containing Neurons in Shaping Neuronal Activity and Plasticity

    Science.gov (United States)

    Liguz-Lecznar, Monika; Urban-Ciecko, Joanna; Kossut, Malgorzata

    2016-01-01

    Since its discovery over four decades ago, somatostatin (SOM) receives growing scientific and clinical interest. Being localized in the nervous system in a subset of interneurons somatostatin acts as a neurotransmitter or neuromodulator and its role in the fine-tuning of neuronal activity and involvement in synaptic plasticity and memory formation are widely recognized in the recent literature. Combining transgenic animals with electrophysiological, anatomical and molecular methods allowed to characterize several subpopulations of somatostatin-containing interneurons possessing specific anatomical and physiological features engaged in controlling the output of cortical excitatory neurons. Special characteristic and connectivity of somatostatin-containing neurons set them up as significant players in shaping activity and plasticity of the nervous system. However, somatostatin is not just a marker of particular interneuronal subpopulation. Somatostatin itself acts pre- and postsynaptically, modulating excitability and neuronal responses. In the present review, we combine the knowledge regarding somatostatin and somatostatin-containing interneurons, trying to incorporate it into the current view concerning the role of the somatostatinergic system in cortical plasticity. PMID:27445703

  19. Emphasis: an active management model

    International Nuclear Information System (INIS)

    The Institute of Nuclear Materials Management was founded and has grown on the basis of promoting professionalism in the nuclear industry. This paper is concerned with professional management of nuclear material. The paper introduces the reader to Emphasis, an active management model. The management model provides the framework to assist a manager in directing his available resources. Emphasis provides for establishing goals, identifying and selecting objectives, matching objectives to specific personnel, preparing and monitoring action plans, and evaluating results. The model stresses crisis prevention by systematically administering and controlling resources. A critical requirement for implementation of the model is the desire to manage, to be in charge of the situation. The nuclear industry does need managers - people who realize the sensitive nature of the industry, professionals who insist on improved performance

  20. A Constitutive Model for Superelastic Shape Memory Alloys Considering the Influence of Strain Rate

    Directory of Open Access Journals (Sweden)

    Hui Qian

    2013-01-01

    Full Text Available Shape memory alloys (SMAs are a relatively new class of functional materials, exhibiting special thermomechanical behaviors, such as shape memory effect and superelasticity, which enable their applications in seismic engineering as energy dissipation devices. This paper investigates the properties of superelastic NiTi shape memory alloys, emphasizing the influence of strain rate on superelastic behavior under various strain amplitudes by cyclic tensile tests. A novel constitutive equation based on Graesser and Cozzarelli’s model is proposed to describe the strain-rate-dependent hysteretic behavior of superelastic SMAs at different strain levels. A stress variable including the influence of strain rate is introduced into Graesser and Cozzarelli’s model. To verify the effectiveness of the proposed constitutive equation, experiments on superelastic NiTi wires with different strain rates and strain levels are conducted. Numerical simulation results based on the proposed constitutive equation and experimental results are in good agreement. The findings in this paper will assist the future design of superelastic SMA-based energy dissipation devices for seismic protection of structures.

  1. Modeling Defects, Shape Evolution, and Programmed Auto-origami in Liquid Crystal Elastomers

    Directory of Open Access Journals (Sweden)

    Andrew eKonya

    2016-06-01

    Full Text Available Liquid crystal elastomers represent a novel class of programmable shape-transforming materials whose shape change trajectory is encoded in the material’s nematic director field. Using three-dimensional nonlinear finite element elastodynamics simulation, we model a variety of different actuation geometries and device designs: thin films containing topological defects, patterns that induce formation of folds and twists, and a bas-relief structure. The inclusion of finite bending energy in the simulation model reveals features of actuation trajectory that may be absent when bending energy is neglected. We examine geometries with a director pattern uniform through the film thickness encoding multiple regions of positive Gaussian curvature. Simulations indicate that heating such a system uniformly produces a disordered state with curved regions emerging randomly in both directions due to the film’s up/down symmetry. By contrast, applying a thermal gradient by heating the material first on one side breaks up/down symmetry and results in a deterministic trajectory producing a more ordered final shape. We demonstrate that a folding zone design containing cut-out areas accommodates transverse displacements without warping or buckling; and demonstrate that bas-relief and more complex bent/twisted structures can be assembled by combining simple design motifs.

  2. Radar Images And Shape Model Of A Triple Asteroid (136617) 1994CC

    Science.gov (United States)

    Brozovic, Marina; Benner, L. A. M.; Nolan, M. C.; Howell, E. S.; Magri, C.; Giorgini, J. D.; Taylor, P. A.; Margot, J. L.; Busch, M. W.; Shepard, M. K.; Scheeres, D. J.; Carter, L. M.

    2010-10-01

    We report radar observations and shape modeling of asteroid (136617) 1994CC, which is only the second triple system known in the near-Earth population, after (153591) 2001 SN263. This object was observed at Goldstone (8560 MHz, 3.5 cm) and Arecibo (2380 MHz, 12.6 cm) from June 12 to June 21, 2009. The radar images and subsequent shape modeling reveal that the primary is 600 m in diameter with a shape that closely resembles that of 1999 KW4 Alpha. The secondary is 130 m in diameter and appears to be in a synchronous orbit with a period of 30 hours. The tertiary satellite is 90 m in diameter and has an orbital period of 9 days. Its semimajor axis of 20 primary radii is the largest discovered so far among near-Earth multiple systems. Among the 37 NEA binary or ternary systems currently known, 80% have been observed by radar and 2/3 were discovered by radar. Since January 1999, 17% of radar-detected NEAs with diameters greater than 200 m have been found to be multiple systems.

  3. Improving the S-Shape Solar Radiation Estimation Method for Supporting Crop Models

    Directory of Open Access Journals (Sweden)

    Nándor Fodor

    2012-01-01

    Full Text Available In line with the critical comments formulated in relation to the S-shape global solar radiation estimation method, the original formula was improved via a 5-step procedure. The improved method was compared to four-reference methods on a large North-American database. According to the investigated error indicators, the final 7-parameter S-shape method has the same or even better estimation efficiency than the original formula. The improved formula is able to provide radiation estimates with a particularly low error pattern index (PIdoy which is especially important concerning the usability of the estimated radiation values in crop models. Using site-specific calibration, the radiation estimates of the improved S-shape method caused an average of 2.72±1.02 (=0.05 relative error in the calculated biomass. Using only readily available site specific metadata the radiation estimates caused less than 5% relative error in the crop model calculations when they were used for locations in the middle, plain territories of the USA.

  4. Modeling Defects, Shape Evolution, and Programmed Auto-origami in Liquid Crystal Elastomers

    Science.gov (United States)

    Konya, Andrew; Gimenez-Pinto, Vianney; Selinger, Robin

    2016-06-01

    Liquid crystal elastomers represent a novel class of programmable shape-transforming materials whose shape change trajectory is encoded in the material’s nematic director field. Using three-dimensional nonlinear finite element elastodynamics simulation, we model a variety of different actuation geometries and device designs: thin films containing topological defects, patterns that induce formation of folds and twists, and a bas-relief structure. The inclusion of finite bending energy in the simulation model reveals features of actuation trajectory that may be absent when bending energy is neglected. We examine geometries with a director pattern uniform through the film thickness encoding multiple regions of positive Gaussian curvature. Simulations indicate that heating such a system uniformly produces a disordered state with curved regions emerging randomly in both directions due to the film’s up/down symmetry. By contrast, applying a thermal gradient by heating the material first on one side breaks up/down symmetry and results in a deterministic trajectory producing a more ordered final shape. We demonstrate that a folding zone design containing cut-out areas accommodates transverse displacements without warping or buckling; and demonstrate that bas-relief and more complex bent/twisted structures can be assembled by combining simple design motifs.

  5. A parabolic model to control quantum interference in T-shaped molecular junctions.

    Science.gov (United States)

    Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio

    2013-09-01

    Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.

  6. Capturing spiral radial growth of conifers using the superellipse to model tree-ring geometric shape

    Directory of Open Access Journals (Sweden)

    Pei-Jian eShi

    2015-10-01

    Full Text Available Tree-rings are often assumed to approximate a circular shape when estimating forest productivity and carbon dynamics. However, tree rings are rarely, if ever, circular, thereby possibly resulting in under- or over-estimation in forest productivity and carbon sequestration. Given the crucial role played by tree ring data in assessing forest productivity and carbon storage within a context of global change, it is particularly important that mathematical models adequately render cross-sectional area increment derived from tree rings. We modelled the geometric shape of tree rings using the superellipse equation and checked its validation based on the theoretical simulation and six actual cross sections collected from three conifers. We found that the superellipse better describes the geometric shape of tree rings than the circle commonly used. We showed that a spiral growth trend exists on the radial section over time, which might be closely related to spiral grain along the longitudinal axis. The superellipse generally had higher accuracy than the circle in predicting the basal area increment, resulting in an improved estimate for the basal area. The superellipse may allow better assessing forest productivity and carbon storage in terrestrial forest ecosystems.

  7. Molecular dynamics simulation of shape memory behaviour using a multi-grain model

    International Nuclear Information System (INIS)

    Shape-memory behaviour in multi-grain material is simulated using a molecular dynamics method. An embedded-atom-method potential for NiAl alloy is applied, and a sequence of conditions including loading, unloading, heating and cooling is imposed. Two types of grain arrangement are used, and the deformation and shape recovery due to phase transformation are observed for both models. The stress–strain relation is revealed to draw a hysteresis loop, and the individual curves are smoother than those previously obtained from a single-crystal model. The deformation mechanism during loading is discussed using local structure analysis. Local deformation is initiated at the grain boundaries, and the deformed region propagates along the twin plane in the grain. The propagation is then obstructed by the grain boundaries, and a band pattern of the deformed area is formed. The influence of the grain shape and distribution, as well as the crystal orientation of each grain, on the deformation behaviour is also investigated. Qualitatively common features in the deformation mechanism and stress–strain relation are observed despite different grain distributions, while the critical values in stress vary, owing to the crystal orientations of the grains

  8. A parabolic model to control quantum interference in T-shaped molecular junctions.

    Science.gov (United States)

    Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio

    2013-09-01

    Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions. PMID:23558406

  9. The life of a meander bend: Connecting shape and dynamics via analysis of a numerical model

    Science.gov (United States)

    Schwenk, Jon; Lanzoni, Stefano; Foufoula-Georgiou, Efi

    2015-04-01

    Analysis of bend-scale meandering river dynamics is a problem of theoretical and practical interest. This work introduces a method for extracting and analyzing the history of individual meander bends from inception until cutoff (called "atoms") by tracking backward through time the set of two cutoff nodes in numerical meander migration models. Application of this method to a simplified yet physically based model provides access to previously unavailable bend-scale meander dynamics over long times and at high temporal resolutions. We find that before cutoffs, the intrinsic model dynamics invariably simulate a prototypical cutoff atom shape we dub simple. Once perturbations from cutoffs occur, two other archetypal cutoff planform shapes emerge called long and round that are distinguished by a stretching along their long and perpendicular axes, respectively. Three measures of meander migration—growth rate, average migration rate, and centroid migration rate—are introduced to capture the dynamic lives of individual bends and reveal that similar cutoff atom geometries share similar dynamic histories. Specifically, through the lens of the three shape types, simples are seen to have the highest growth and average migration rates, followed by rounds, and finally longs. Using the maximum average migration rate as a metric describing an atom's dynamic past, we show a strong connection between it and two metrics of cutoff geometry. This result suggests both that early formative dynamics may be inferred from static cutoff planforms and that there exists a critical period early in a meander bend's life when its dynamic trajectory is most sensitive to cutoff perturbations. An example of how these results could be applied to Mississippi River oxbow lakes with unknown historic dynamics is shown. The results characterize the underlying model and provide a framework for comparisons against more complex models and observed dynamics.

  10. Attractors for a Three-Dimensional Thermo-Mechanical Model of Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    Pierluigi COLLI; Michel FR(E)MOND; Elisabetta ROCCA; Ken SHIRAKAWA

    2006-01-01

    In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global attractor. More precisely,we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the non-autonomous case by the limiting global attractor.

  11. Average pulse shape model for leading edge timing with Ge(Li) coaxial detector

    International Nuclear Information System (INIS)

    A model is presented for prompt time-response from leading-edge triggering, where calculations are rendered simpler for uniform γ-irradiation of coaxial Ge(Li) detector. Pulse shapes are formed at the timing filter amplifier output, from direct detector pulse. Average pulse-shape method is found responsible for some sort of walk compensation and by drawing time-resolution vs triggering fraction, one can predict the best FWHM with detector of RC-filtered signal. It also shows the effect of mixed filter time-constant on r.m.s. noise. Taking account of both statistical and noise effects on FWHM, the statistical contribution increases to 7% at 3 MeV of the detected energy

  12. Modeling of effects of matrix on actuation characteristics of embedded shape memory alloy wires

    Institute of Scientific and Technical Information of China (English)

    CUI Xiao-long; ZHENG Yan-jun; CUI Li-shan

    2005-01-01

    Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum recovery stress. The thermal strain rate of the SMA wires upon heating is more sensitive to the matrix properties than the stress rate does. Additional fibers embedded in the matrix have significant effect on the stress distribution between the SMA wires and the matrix, and thus affect the interface quality significantly. Fibers with negative thermal expansion coefficient are beneficial to the interface between shape memory alloy wires and the epoxy matrix. All conclusions based on the numerical modeling can find experimental supports.

  13. Improved Frequency Fluctuation Model for Spectral Line Shape Calculations in Fusion Plasmas

    Science.gov (United States)

    Ferri, S.; Calisti, A.; Mossé, C.; Talin, B.; Lisitsa, V.

    2010-10-01

    A very fast method to calculate spectral line shapes emitted by plasmas accounting for charge particle dynamics and effects of an external magnetic field is proposed. This method relies on a new formulation of the Frequency Fluctuation Model (FFM), which yields to an expression of the dynamic line profile as a functional of the static distribution function of frequencies. This highly efficient formalism, not limited to hydrogen-like systems, allows to calculate pure Stark and Stark-Zeeman line shapes for a wide range of density, temperature and magnetic field values, which is of importance in plasma physics and astrophysics. Various applications of this method are presented for conditions related to fusion plasmas.

  14. Hysteresis model of shape memory alloy wire-based laminated rubber bearing under compression and unidirectional shear loadings

    Science.gov (United States)

    Hedayati Dezfuli, F.; Shahria Alam, M.

    2015-06-01

    Smart lead rubber bearings (LRBs), in which a shape memory alloy (SMA) is used in the form of wires, are a new generation of elastomeric isolators with improved performance in terms of recentering capability and energy dissipation capacity. It is of great interest to implement SMA wire-based lead rubber bearings (SMA-LRBs) in bridges; however, currently there is no appropriate hysteresis model for accurately simulating the behavior of such isolators. A constitutive model for SMA-LRBs is proposed in this study. An LRB is equipped with a double cross configuration of SMA wires (DC-SMAW) and subjected to compression and unidirectional shear loadings. Due to the complexity of the shear behavior of the SMA-LRB, a hysteresis model is developed for the DC-SMAWs and then combined with the bilinear kinematic hardening model, which is assumed for the LRB. Comparing the hysteretic response of decoupled systems with that of the SMA-LRB shows that the high recentering capability of the DC-SMAW model with zero residual deformation could noticeably reduce the residual deformation of the LRB. The developed constitutive model for DC-SMAWs is characterized by three stiffnesses when the shear strain exceeds a starting limit at which the SMA wires are activated due to phase transformation. An important point is that the shear hysteresis of the DC-SMAW model looks different from the flag-shaped hysteresis of the SMA because of the specific arrangement of wires and its effect on the resultant forces transferred from the wires to the rubber bearing.

  15. Rhizosphere heterogeneity shapes abundance and activity of sulfur-oxidizing bacteria in vegetated salt marsh sediments

    Directory of Open Access Journals (Sweden)

    François eThomas

    2014-06-01

    Full Text Available Salt marshes are highly productive ecosystems hosting an intense sulfur (S cycle, yet little is known about S-oxidizing microorganisms in these ecosystems. Here, we studied the diversity and transcriptional activity of S-oxidizers in salt marsh sediments colonized by the plant Spartina alterniflora, and assessed variations with sediment depth and small-scale compartments within the rhizosphere. We combined next-generation amplicon sequencing of 16S rDNA and rRNA libraries with phylogenetic analyses of marker genes for two S-oxidation pathways (soxB and rdsrAB. Gene and transcript numbers of soxB and rdsrAB phylotypes were quantified simultaneously, using newly designed (RT-qPCR assays. We identified a diverse assemblage of S-oxidizers, with Chromatiales and Thiotrichales being dominant. The detection of transcripts from S-oxidizers was mostly confined to the upper 5 cm sediments, following the expected distribution of root biomass. A common pool of species dominated by Gammaproteobacteria transcribed S-oxidation genes across roots, rhizosphere, and surrounding sediment compartments, with rdsrAB transcripts prevailing over soxB. However, the root environment fine-tuned the abundance and transcriptional activity of the S-oxidizing community. In particular, the global transcription of soxB was higher on the roots compared to mix and rhizosphere samples. Furthermore, the contribution of Epsilonproteobacteria-related S-oxidizers tended to increase on Spartina roots compared to surrounding sediments. These data shed light on the under-studied oxidative part of the sulfur cycle in salt marsh sediments and indicate small-scale heterogeneities are important factors shaping abundance and potential activity of S-oxidizers in the rhizosphere.

  16. The contents of predictions in sentence comprehension: activation of the shape of objects before they are referred to.

    Science.gov (United States)

    Rommers, Joost; Meyer, Antje S; Praamstra, Peter; Huettig, Falk

    2013-02-01

    When comprehending concrete words, listeners and readers can activate specific visual information such as the shape of the words' referents. In two experiments we examined whether such information can be activated in an anticipatory fashion. In Experiment 1, listeners' eye movements were tracked while they were listening to sentences that were predictive of a specific critical word (e.g., "moon" in "In 1969 Neil Armstrong was the first man to set foot on the moon"). 500 ms before the acoustic onset of the critical word, participants were shown four-object displays featuring three unrelated distractor objects and a critical object, which was either the target object (e.g., moon), an object with a similar shape (e.g., tomato), or an unrelated control object (e.g., rice). In a time window before shape information from the spoken target word could be retrieved, participants already tended to fixate both the target and the shape competitors more often than they fixated the control objects, indicating that they had anticipatorily activated the shape of the upcoming word's referent. This was confirmed in Experiment 2, which was an ERP experiment without picture displays. Participants listened to the same lead-in sentences as in Experiment 1. The sentence-final words corresponded to the predictable target, the shape competitor, or the unrelated control object (yielding, for instance, "In 1969 Neil Armstrong was the first man to set foot on the moon/tomato/rice"). N400 amplitude in response to the final words was significantly attenuated in the shape-related compared to the unrelated condition. Taken together, these results suggest that listeners can activate perceptual attributes of objects before they are referred to in an utterance.

  17. Mathematical Modeling and Control of Nonlinear Oscillators with Shape Memory Alloys

    Science.gov (United States)

    Bendame, Mohamed

    Shape memory alloys (SMAs) belong to an interesting type of materials that have attracted the attention of scientists and engineers over the last few decades. They have some interesting properties that made them the subject of extensive research to find the best ways to utilize them in different engineering, biomedical, and scientific applications. In this thesis, we develop a mathematical model and analyze the behavior of SMAs by considering a one degree of freedom nonlinear oscillator consisting of a mass connected to a fixed frame through a viscous damping and a shape memory alloy device. Due to the nonlinear and dissipative nature of shape memory alloys, optimal control and Lyapunov stability theories are used to design a controller to stabilize the response of the one degree of freedom nonlinear oscillator. Since SMAs exist in two phases, martensite and austenite, and their phase transformations are dependent on stress and temperature, this work is presented in two parts. The first part deals with the nonlinear oscillator system in its two separate phases by considering a temperature where the SMA exists in only one of the phases. A model for each phase is developed based on Landau-Ginzburg-Devonshire theory that defines the free energy in a polynomial form enabling us to describe the SMAs shape memory effect and pseudoelasticity. However, due to the phenomenon of hysteresis in SMAs, the response of the nonlinear oscillator with a SMA element, in either phase, is chaotic and unstable. In order to stabilize the chaotic behavior, an optimal linear quadratic regulator controller is designed around a stable equilibrium for the martensitic and the austenitic phases. The closed-loop response for each phase is then simulated and computational results are presented. The second part of the thesis deals with the entire system in its dynamics by combining the two phases and taking into account the effect of temperature on the response of the system. Governing equations

  18. Local Iinearization modeling method of a multilayer wave-shaped steel-belt damper (MWSD)

    Institute of Scientific and Technical Information of China (English)

    AO Hong-rui; HAO De-gang; SUN Yi; JIANG Hong-yuan; B.A. Antipov

    2008-01-01

    To analyze the modeling methods of the dry friction rotor system, a local linearization model of the dry friction damping rotor system was built based on the simplified model of the wave-shaped steel-belt support- ing rotor system. In this model, the linear stiffness of damper closed to pre-deformation was defined as the stiff-ness of damper, the maximum amplitude of the rotor was calculated according to the load and linear rotor, and the damper's parameters were defined on the basis of the energy dissipation parameters. The presented method can reflect the hysteresis characteristics and is easy to calculate. Experimental results demonstrate the accuracy and feasibility of this method.

  19. A Model for the Secondary Scintillation Pulse Shape from a Gas Proportional Scintillation Counter

    CERN Document Server

    Kazkaz, Kareem

    2015-01-01

    Proportional scintillation counters (PSCs), both single- and dual-phase, can measure the scintillation (S1) and ionization (S2) channels from particle interactions within the detector volume. The signal obtained from these detectors depends first on the physics of the medium (the initial scintillation and ionization), and second how the physics of the detector manipulates the resulting photons and liberated electrons. In this paper we develop a model of the detector physics that incorporates event topology, detector geometry, electric field configuration, purity, optical properties of components, and wavelength shifters. We present an analytic form of the model, which allows for general study of detector design and operation, and a Monte Carlo model which enables a more detailed exploration of S2 events. This model may be used to study systematic effects in currents detectors such as energy and position reconstruction, pulse shape discrimination, event topology, dead time calculations, purity, and electric fi...

  20. Using the Correlation Criterion to Position and Shape RBF Units for Incremental Modelling

    Institute of Scientific and Technical Information of China (English)

    Xun-Xian Wang; Sheng Chen; Chris J. Harris

    2006-01-01

    A novel technique is proposed for the incremental construction of sparse radial basis function (RBF) networks.The correlation between an RBF regressor and the training data is used as the criterion to position and shape the RBF node, and it is shown that this is equivalent to incrementally minimise the modelling mean square error. A guided random search optimisation method, called the repeated weighted boosting search, is adopted to append RBF nodes one by one in an incremental regression modelling procedure. The experimental results obtained using the proposed method demonstrate that it provides a viable alternative to the existing state-of-the-art modelling techniques for constructing parsimonious RBF models that generalise well.

  1. Computational modeling of size-dependent superelasticity of shape memory alloys

    Science.gov (United States)

    Qiao, Lei; Radovitzky, Raul

    2016-08-01

    We propose a nonlocal continuum model to describe the size-dependent superelastic responses observed in recent experiments of shape memory alloys. The modeling approach extends a superelasticity formulation based on the martensitic volume fraction, and combines it with gradient plasticity theories. Size effects are incorporated through two internal length scales, an energetic length scale and a dissipative length scale, which correspond to the gradient terms in the free energy and the dissipation, respectively. We also propose a computational framework based on a variational formulation to solve the coupled governing equations resulting from the nonlocal superelastic model. Within this framework, a robust and scalable algorithm is implemented for large scale three-dimensional problems. A numerical study of the grain boundary constraint effect shows that the model is able to capture the size-dependent stress hysteresis and strain hardening during the loading and unloading cycles in polycrystalline SMAs.

  2. Computer aided segmentation of kidneys using locally shape constrained deformable models on CT images

    Science.gov (United States)

    Erdt, Marius; Sakas, Georgios

    2010-03-01

    This work presents a novel approach for model based segmentation of the kidney in images acquired by Computed Tomography (CT). The developed computer aided segmentation system is expected to support computer aided diagnosis and operation planning. We have developed a deformable model based approach based on local shape constraints that prevents the model from deforming into neighboring structures while allowing the global shape to adapt freely to the data. Those local constraints are derived from the anatomical structure of the kidney and the presence and appearance of neighboring organs. The adaptation process is guided by a rule-based deformation logic in order to improve the robustness of the segmentation in areas of diffuse organ boundaries. Our work flow consists of two steps: 1.) a user guided positioning and 2.) an automatic model adaptation using affine and free form deformation in order to robustly extract the kidney. In cases which show pronounced pathologies, the system also offers real time mesh editing tools for a quick refinement of the segmentation result. Evaluation results based on 30 clinical cases using CT data sets show an average dice correlation coefficient of 93% compared to the ground truth. The results are therefore in most cases comparable to manual delineation. Computation times of the automatic adaptation step are lower than 6 seconds which makes the proposed system suitable for an application in clinical practice.

  3. A multidimensional stability model for predicting shallow landslide size and shape across landscapes

    Science.gov (United States)

    Milledge, David G; Bellugi, Dino; McKean, Jim A; Densmore, Alexander L; Dietrich, William E

    2014-01-01

    The size of a shallow landslide is a fundamental control on both its hazard and geomorphic importance. Existing models are either unable to predict landslide size or are computationally intensive such that they cannot practically be applied across landscapes. We derive a model appropriate for natural slopes that is capable of predicting shallow landslide size but simple enough to be applied over entire watersheds. It accounts for lateral resistance by representing the forces acting on each margin of potential landslides using earth pressure theory and by representing root reinforcement as an exponential function of soil depth. We test our model's ability to predict failure of an observed landslide where the relevant parameters are well constrained by field data. The model predicts failure for the observed scar geometry and finds that larger or smaller conformal shapes are more stable. Numerical experiments demonstrate that friction on the boundaries of a potential landslide increases considerably the magnitude of lateral reinforcement, relative to that due to root cohesion alone. We find that there is a critical depth in both cohesive and cohesionless soils, resulting in a minimum size for failure, which is consistent with observed size-frequency distributions. Furthermore, the differential resistance on the boundaries of a potential landslide is responsible for a critical landslide shape which is longer than it is wide, consistent with observed aspect ratios. Finally, our results show that minimum size increases as approximately the square of failure surface depth, consistent with observed landslide depth-area data. PMID:26213663

  4. A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators

    Energy Technology Data Exchange (ETDEWEB)

    Sepiani, H.; Ebrahimi, F. [University of Tehran, Tehran (Iran, Islamic Republic of); Karimipour, H. [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

    2009-12-15

    This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant

  5. VOF Modeling and Analysis of the Segmented Flow in Y-Shaped Microchannels for Microreactor Systems

    Directory of Open Access Journals (Sweden)

    Xian Wang

    2013-01-01

    Full Text Available Microscaled devices receive great attention in microreactor systems for producing high renewable energy due to higher surface-to-volume, higher transport rates (heat or/and mass transfer rates, and other advantages over conventional-size reactors. In this paper, the two-phase liquid-liquid flow in a microchannel with various Y-shaped junctions has been studied numerically. Two kinds of immiscible liquids were injected into a microchannel from the Y-shaped junctions to generate the segment flow mode. The segment length was studied. The volume of fluid (VOF method was used to track the liquid-liquid interface and the piecewise-liner interface construction (PLIC technique was adopted to get a sharp interface. The interfacial tension was simulated with continuum surface force (CSF model and the wall adhesion boundary condition was taken into consideration. The simulated flow pattern presents consistence with our experimental one. The numerical results show that a segmented flow mode appears in the main channel. Under the same inlet velocities of two liquids, the segment lengths of the two liquids are the same and depend on the inclined angles of two lateral channels. The effect of inlet velocity is studied in a typical T-shaped microchannel. It is found that the ratio between the lengths of two liquids is almost equal to the ratio between their inlet velocities.

  6. Polypod-Shaped DNAs: Small-Angle X-ray Scattering and Immunostimulatory Activity.

    Science.gov (United States)

    Sanada, Yusuke; Shiomi, Tomoki; Okobira, Tadashi; Tan, Mengmeng; Nishikawa, Makiya; Akiba, Isamu; Takakura, Yoshinobu; Sakurai, Kazuo

    2016-04-19

    We explored in detail the relationship between the structure in aqueous solution and immunostimulatory activity of polypod-shaped DNAs, called polypodnas. The polypodnas were constructed using 3-6 oligodeoxynucleotides (ODNs) to obtain tri-, tetra-, penta-, and hexapodna, each of which had 3, 4, 5, and 6 arms made of double-stranded DNA, respectively. A highly potent immunostimulatory CpG sequence was included into each of the polypodnas. Synchrotron X-ray scattering analysis showed that the double-stranded DNA arms of all of the polypodnas adopted a B-form DNA conformation. The analysis also suggested that some nucleotides in the central parts of pentapodna and hexapodna did not form base pairs, whereas those of tripodna and tetrapodna all formed base pairs. This difference would occur because of an increase in steric hindrance and electrical repulsion with increasing number of arms. The pentapodna and hexapodna induced a large amount of tumor necrosis factor α-release from macrophage-like cells compared with the tripodna and tetrapodna, suggesting that the partly loosened DNA in polypodna with many arms is advantageous for exposing the immunostimulatory sequences of the polypodna. PMID:27007061

  7. Immunological identification of candidate proteins involved in regulating active shape changes of outer hair cells.

    Science.gov (United States)

    Knipper, M; Zimmermann, U; Köpschall, I; Rohbock, K; Jüngling, S; Zenner, H P

    1995-06-01

    By employing immunological methods, it has been demonstrated that myosin, myosin light chain (MLC) and myosin light chain kinase (MLCK) proteins in outer hair cells (OHC) are immunologically different from isoforms in platelets, smooth muscle and heart muscle, and are probably more related to isoforms found in red blood cells (RBC). Moreover, proteins related to band 3 protein (b3p) and protein 4.1 (p 4.1), ankyrin as well as fodrin and spectrin, but not glycophorin, have been identified in isolated OHCs. Both OHCs and RBC differ from other motile non-muscle cells in their lack of smooth muscle isoforms of actin, their common high levels of spectrin-, ankyrin- and band 3-like proteins, as well as the expression of the 80 kDa protein 4.1 isoform. The data support the notion that motility of OHC may be based upon regulation of the b3p/p 4.1/ankyrin complex, and thus may be reminiscent to the active shape changes in RBC.

  8. Community environments shaping transactional sex among sexually active men in Malawi, Nigeria, and Tanzania.

    Science.gov (United States)

    Stephenson, Rob; Winter, Amy; Elfstrom, Miriam

    2013-01-01

    Transactional sex, or the exchange of sex for material goods or money, is a risky sexual behavior that has been linked to HIV/AIDS and gender-based violence. Throughout sub-Saharan Africa, transactional sex remains a common practice, putting men and women at risk of HIV. However, little is known of how community environments shape men's participation in risky transactional sex. This analysis examines community-level influences on participation in risky transactional sex among sexually active men in three African countries (Malawi, Tanzania, and Nigeria). The analysis uses Demographic and Health Survey (DHS) data to examine the association between men's report of risky transactional sex and community characteristics including economic, gender norms, HIV behavior and knowledge, and demographic factors. The results show that men residing in communities with more female education and later age of first birth are less likely to report risky transactional sex, while men who live in communities where men report higher number of sexual partners are more likely to report risky transactional sex. While programmatic interventions should continue to improve women's status individually and relative to men, such efforts should be extended to recognize that many community and cultural influences also affect men's sexual behavior. Programs that understand, discuss, and challenge community factors that influence men's sexual behavior may be able to provide a more effective intervention resulting in opportunities for communities to initiate behavioral change.

  9. Nanobiomimetic Active Shape Control - Fluidic and Swarm-Intelligence Embodiments for Planetary Exploration

    Science.gov (United States)

    Santoli, S.

    The concepts of Active Shape Control ( ASC ) and of Generalized Quantum Holography ( GQH ), respectively embodying a closer approach to biomimicry than the current macrophysics-based attempts at bioinspired robotic systems, and realizing a non-connectionistic, life-like kind of information processing that allows increasingly depths of mimicking of the biological structure-function solidarity, which have been formulated in physical terms in previous papers, are here further investigated for application to bioinspired flying or swimming robots for planetary exploration. It is shown that nano-to-micro integration would give the deepest level of biomimicry, and that both low and very low Reynolds number ( Re ) fluidics would involve GQH and Fiber Bundle Topology ( FBT ) for processing information at the various levels of ASC bioinspired robotics. While very low Re flows lend themselves to geometrization of microrobot dynamics and to FBT design, the general design problem is geometrized through GQH , i.e. made independent of dynamic considerations, thus allowing possible problems of semantic dyscrasias in highly complex hierarchical dynamical chains of sensing information processing actuating to be overcome. A roadmap to near- and medium-term nanostructured and nano-to-micro integration realizations is suggested.

  10. Rotation Driven Shape-Phase Transition of the Yrast Nuclear States with O(6) Symmetry in the Interacting Boson Model

    Institute of Scientific and Technical Information of China (English)

    MU Liang-Zhu; LIU Yu-Xin

    2005-01-01

    @@ In a framework of the interacting boson model (usually referred to as IBM-1) with angular momentum projection on the coherent state, we obtain the energy surface functional of nuclei in terms of angular momentum and shape parameters. Analysing the rotation driven effect on the equilibrium shape shows that the yrast states of the nuclei with O(6) symmetry will experience a shape-phase transition from γ-soft deformed to triaxially deformed and then to spherical shape along the yrast line as the angular momentum increases.

  11. System-Level Design of a Shape Memory Alloy Actuator for Active Clearance Control in the High-Pressure Turbine

    Science.gov (United States)

    DeCastro, Jonathan A.; Melcher, Kevin J.; Noebe, Ronald D.

    2005-01-01

    This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

  12. Nucleon shape and electromagnetic form factors in the chiral constituent quark model

    CERN Document Server

    Dahiya, Harleen

    2010-01-01

    The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.

  13. Conformal mapping modeling of metal plastic deformation and die cavity in special-shaped extrusion

    Institute of Scientific and Technical Information of China (English)

    齐红元; 朱衡君; 杜凤山; 刘才

    2002-01-01

    With the help of Complex Function Mapping studied results, the analysis function of Conformal Mapping is set up. Since the complicated three dimension's deformation problems are transferred into two dimension problems, both the stream function and strain ratio field are analyzed in the metal plastic deformation. Using the upper-bound principles, the theory of metal deformation and die cavity optimized modeling is established for random special-shaped product extrusion. As a result, this enables the realization of intelligent technique target in the die cavity of CAD/CAM integration.

  14. Functional data analytic approach of modeling ECG T-wave shape to measure cardiovascular behavior

    CERN Document Server

    Zhou, Yingchun; 10.1214/09-AOAS273

    2010-01-01

    The T-wave of an electrocardiogram (ECG) represents the ventricular repolarization that is critical in restoration of the heart muscle to a pre-contractile state prior to the next beat. Alterations in the T-wave reflect various cardiac conditions; and links between abnormal (prolonged) ventricular repolarization and malignant arrhythmias have been documented. Cardiac safety testing prior to approval of any new drug currently relies on two points of the ECG waveform: onset of the Q-wave and termination of the T-wave; and only a few beats are measured. Using functional data analysis, a statistical approach extracts a common shape for each subject (reference curve) from a sequence of beats, and then models the deviation of each curve in the sequence from that reference curve as a four-dimensional vector. The representation can be used to distinguish differences between beats or to model shape changes in a subject's T-wave over time. This model provides physically interpretable parameters characterizing T-wave sh...

  15. A drifting trajectory prediction model based on object shape and stochastic mo-tion features

    Institute of Scientific and Technical Information of China (English)

    王胜正; 聂皓冰; 施朝健

    2014-01-01

    There is a huge demand to develop a method for marine search and rescue (SAR) operators automatically predicting the most probable searching area of the drifting object. This paper presents a novel drifting prediction model to improve the accuracy of the drifting trajectory computation of the sea-surface objects. First, a new drifting kinetic model based on the geometry characteristics of the objects is proposed that involves the effects of the object shape and stochastic motion features in addition to the traditional factors of wind and currents. Then, a computer simulation-based method is employed to analyze the stochastic motion features of the drifting objects, which is applied to estimate the uncertainty parameters of the stochastic factors of the drifting objects. Finally, the accuracy of the model is evaluated by comparison with the flume experimental results. It is shown that the proposed method can be used for various shape objects in the drifting trajectory prediction and the maritime search and rescue decision-making system.

  16. Modelling profile and shape evolution during hot rolling of steel strip

    International Nuclear Information System (INIS)

    Profile and shape control are required to assure the dimensional quality of rolled strip. Occurrence of waves either at the edges or centre of strips is attributed to inconsistency between the entry and exit cross-section profiles of the stock within a given rolling pass. The exit profile of the strip can be computed by considering that the such profile is the complement of that of the roll-gap, which is affected by wear, thermal expansion and distortion of the work rolls. A computer model was developed to predict the profile of the roll-gap taking into account the thermal gradient within the work roll and the distortion caused by the acting forces. It was possible to establish a good correlation between the profiles of strips obtained from trials carried out on site, and the predictions of the model. The model allows for the prediction of the onset of shape defects from changes in the profile of rolled strips. (Author) 17 refs

  17. A Thrombus Generation Model Applied to Aneurysms Treated with Shape Memory Polymer Foam and Metal Coils

    Science.gov (United States)

    Horn, John; Ortega, Jason; Hartman, Jonathan; Maitland, Duncan

    2015-11-01

    To prevent their rupture, intracranial aneurysms are often treated with endovascular metal coils which fill the aneurysm sac and isolate it from the arterial flow. Despite its widespread use, this method can result in suboptimal outcomes leading to aneurysm recurrence. Recently, shape memory polymer foam has been proposed as an alternative aneurysm filler. In this work, a computational model has been developed to predict thrombus formation in blood in response to such cardiovascular implantable devices. The model couples biofluid and biochemical phenomena present as the blood interacts with a device and stimulates thrombus formation. This model is applied to simulations of both metal coil and shape memory polymer foam treatments within an idealized 2D aneurysm geometry. Using the predicted thrombus responses, the performance of these treatments is evaluated and compared. The results suggest that foam-treated aneurysms may fill more quickly and more completely with thrombus than coil-filled aneurysms, potentially leading to improved long-term aneurysm healing. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  18. Thermodynamic constitutive model for load-biased thermal cycling test of shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Young, Sung, E-mail: ysy@kut.ac.kr [Korea University of Technology and Education, Chonan (Korea, Republic of); Nam, Tae-Hyun, E-mail: tahynam@gnu.ac.kr [School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of)

    2013-12-15

    Graphical abstract: - Highlights: • Thermodynamic calculation model for martensitic transformation of shape memory alloy was proposed. • Evolution of the self-accommodation was considered independently by a rate-dependent kinetic equation. • Finite element calculation was conducted for B2–B19′ transformation of Ti–44.5Ni–5Cu–0.5 V (at.%). • Three-dimensional numerical results predict the macroscopic strain under bias loading accurately. - Abstract: This paper presents a three-dimensional calculation model for martensitic phase transformation of shape memory alloy. Constitutive model based on thermodynamic theory was provided. The average behavior was accounted for by considering the volume fraction of each martensitic variant in the material. Evolution of the volume fraction of each variant was determined by a rate-dependent kinetic equation. We assumed that nucleation rate is faster for the self-accommodation than for the stress-induced variants. Three-dimensional finite element analysis was conducted and the results were compared with the experimental data of Ti–44.5Ni–5Cu–0.5 V (at.%) alloy under bias loading.

  19. A unified model for an external trap in a cigar-shaped Bose–Einstein condensate

    International Nuclear Information System (INIS)

    In recent years, the study of cigar shaped Bose–Einstein condensate (BEC) under a variety of external confinements has attracted a great deal of attention, from both theoretical and experimental researchers. We report a unified model for obtaining explicit solutions under various kinds of physically relevant space- and time-modulated external traps and nonlinearities for the cigar shaped BEC. Our novel mechanism paves the way to investigate the system for a family of potential functions unified as a physical parameter of the system. We apply and illustrate our results for a number of exactly solvable quantum mechanical potentials; harmonic, double-well, Pösch–Teller, Morse, Toda lattice and power-law as some of the applications of our model. Expressions of the condensate density are provided for these potentials. In addition, as an application of our model, we have illustrated the condensate dynamics for harmonic, double-well and Pösch–Teller potentials. In the presence of loss/gain for a Pösch–Teller potential, the condensate density shows an interesting collapse and revival. (paper)

  20. Review of critical point symmetries and shape phase transitions within algebraic and collective models

    International Nuclear Information System (INIS)

    Several aspect of shape phase transitions and critical point symmetries are reviewed in this contribution within the frameworks of the Interacting Boson Model (IBM) and the Interacting Boson Fermion Model (IBFM) for even and odd systems respectively and compared with collective geometric models. We discuss in particular the case of an odd j = 3/2 particle coupled to an even-even boson core that undergoes a transition from the spherical limit U(5) to the γ-unstable limit O(6). The spectrum and transition rates at the critical point are similar to those of the even core and they agree qualitatively with the E(5/4) boson-fermion symmetry. We discuss also the UBF (5) to SUBF (3) shape phase transition in which the allowed fermionic orbitals are j = 1/2; 3/2; 5/2. The formalism of the intrinsic or coherent states is used to describe in details the ground state as well as the excited β- and γ- bands. This formalism is also used to calculate the Potential Energy Surface of the cubic quadrupole operator that leads to triaxiality. (author)

  1. Analytical model for low-frequency transmission loss calculation of membranes loaded with arbitrarily shaped masses

    Science.gov (United States)

    Langfeldt, F.; Gleine, W.; von Estorff, O.

    2015-08-01

    An analytical model for the transmission loss calculation of thin rectangular and circular membranes loaded with rigid masses of arbitrary shape, the so-called membrane-type acoustic metamaterials, is presented. The coupling between the membrane and the added masses is introduced by approximating the continuous interaction force with a set of discrete point forces. This results in a generalized linear eigenvalue problem that is solved for the eigenfrequencies and eigenvectors of the coupled system. The concept of the effective surface mass density is employed to calculate the low-frequency transmission loss using the obtained eigenpairs. The proposed model is verified using numerical data from a finite element model and the convergence behavior of the point matching approach is investigated using Richardson extrapolation. Finally, a method based upon the grid convergence index for estimating the error that is introduced due to the point matching approach is presented.

  2. Using Soft Constraints To Learn Semantic Models Of Descriptions Of Shapes

    CERN Document Server

    Guadarrama, Sergio

    2010-01-01

    The contribution of this paper is to provide a semantic model (using soft constraints) of the words used by web-users to describe objects in a language game; a game in which one user describes a selected object of those composing the scene, and another user has to guess which object has been described. The given description needs to be non ambiguous and accurate enough to allow other users to guess the described shape correctly. To build these semantic models the descriptions need to be analyzed to extract the syntax and words' classes used. We have modeled the meaning of these descriptions using soft constraints as a way for grounding the meaning. The descriptions generated by the system took into account the context of the object to avoid ambiguous descriptions, and allowed users to guess the described object correctly 72% of the times.

  3. Void probability as a function of the void's shape and scale-invariant models

    Science.gov (United States)

    Elizalde, E.; Gaztanaga, E.

    1991-01-01

    The dependence of counts in cells on the shape of the cell for the large scale galaxy distribution is studied. A very concrete prediction can be done concerning the void distribution for scale invariant models. The prediction is tested on a sample of the CfA catalog, and good agreement is found. It is observed that the probability of a cell to be occupied is bigger for some elongated cells. A phenomenological scale invariant model for the observed distribution of the counts in cells, an extension of the negative binomial distribution, is presented in order to illustrate how this dependence can be quantitatively determined. An original, intuitive derivation of this model is presented.

  4. Fast Preisach modeling method for shape memory alloy actuators using major hysteresis loops

    Science.gov (United States)

    Choi, Byung-Jun; Lee, Yun-Jung; Choi, Bong-Yeol

    2004-10-01

    The control accuracy of smart actuators, such as a shape memory alloy (SMA) or piezoceramic actuator, is limited due to their inherent hysteresis nonlinearities with a local memory, resulting from the influence of a previous input on subsequent behavior. In addition, the existence of minor loops in the major loop because of a local memory also makes the mathematical modeling and design of a controller difficult for SMA actuators. Therefore, to enhance the controllability of a smart actuator, the Preisach hysteresis model has emerged as an appropriate behavioral model, yet the modeling is difficult and the model equation complex. Accordingly, to resolve these difficulties, the current paper proposes a simple method based on applying the proportional relationship between the major loop and the FOD curves of an SMA actuator to the Preisach model. As such, using only data for the major hysteresis loop, the proposed method enables the FOD curves to be easily approximated and the output length rapidly computed. The efficacy of the proposed Preisach modeling method is confirmed based on comparative experiments with the classical Preisach model.

  5. ON SKEW-NORMAL MODEL FOR ECONOMICALLY ACTIVE POPULATION

    Directory of Open Access Journals (Sweden)

    OLOSUNDE AKINLOLU A

    2011-04-01

    Full Text Available The literature related to skew-symmetric distribution have grown rapidly in recent years but at the moment no publication on its applications concerning the description of economically active data with this type of probability models. In this paper, we provided an extension to this skew-normal distribution, which is also part of the family of skewed class of normal but with additional shape parameters δ. Some properties of this distribution are presented and finally, we considered fitting it to economically active population data. The model exhibited a better behaviour when compared to normal and skew normal distributions.

  6. Consistent dust and gas models for protoplanetary disks. I. Disk shape, dust settling, opacities, and PAHs

    Science.gov (United States)

    Woitke, P.; Min, M.; Pinte, C.; Thi, W.-F.; Kamp, I.; Rab, C.; Anthonioz, F.; Antonellini, S.; Baldovin-Saavedra, C.; Carmona, A.; Dominik, C.; Dionatos, O.; Greaves, J.; Güdel, M.; Ilee, J. D.; Liebhart, A.; Ménard, F.; Rigon, L.; Waters, L. B. F. M.; Aresu, G.; Meijerink, R.; Spaans, M.

    2016-02-01

    We propose a set of standard assumptions for the modelling of Class II and III protoplanetary disks, which includes detailed continuum radiative transfer, thermo-chemical modelling of gas and ice, and line radiative transfer from optical to cm wavelengths. The first paper of this series focuses on the assumptions about the shape of the disk, the dust opacities, dust settling, and polycyclic aromatic hydrocarbons (PAHs). In particular, we propose new standard dust opacities for disk models, we present a simplified treatment of PAHs in radiative equilibrium which is sufficient to reproduce the PAH emission features, and we suggest using a simple yet physically justified treatment of dust settling. We roughly adjust parameters to obtain a model that predicts continuum and line observations that resemble typical multi-wavelength continuum and line observations of Class II T Tauri stars. We systematically study the impact of each model parameter (disk mass, disk extension and shape, dust settling, dust size and opacity, gas/dust ratio, etc.) on all mainstream continuum and line observables, in particular on the SED, mm-slope, continuum visibilities, and emission lines including [OI] 63 μm, high-J CO lines, (sub-)mm CO isotopologue lines, and CO fundamental ro-vibrational lines. We find that evolved dust properties, i.e. large grains, often needed to fit the SED, have important consequences for disk chemistry and heating/cooling balance, leading to stronger near- to far-IR emission lines in general. Strong dust settling and missing disk flaring have similar effects on continuum observations, but opposite effects on far-IR gas emission lines. PAH molecules can efficiently shield the gas from stellar UV radiation because of their strong absorption and negligible scattering opacities in comparison to evolved dust. The observable millimetre-slope of the SED can become significantly more gentle in the case of cold disk midplanes, which we find regularly in our T Tauri models

  7. Classification of bones from MR images in torso PET-MR imaging using a statistical shape model

    Science.gov (United States)

    Reza Ay, Mohammad; Akbarzadeh, Afshin; Ahmadian, Alireza; Zaidi, Habib

    2014-01-01

    of 20 clinical studies was designed. Using this training set, a bone atlas was trained taking advantage of PCA analysis. Our active shape segmentation technique uses the trained shape model to segment bones from user defined initial seed points. The segmentation algorithm was evaluated using 10 clinical datasets (aligned MR and CT pairs). The resulting attenuation maps were compared to corresponding attenuation maps derived from CT resulting in a mean relative difference less than 7%.

  8. Classification of bones from MR images in torso PET-MR imaging using a statistical shape model

    International Nuclear Information System (INIS)

    of 20 clinical studies was designed. Using this training set, a bone atlas was trained taking advantage of PCA analysis. Our active shape segmentation technique uses the trained shape model to segment bones from user defined initial seed points. The segmentation algorithm was evaluated using 10 clinical datasets (aligned MR and CT pairs). The resulting attenuation maps were compared to corresponding attenuation maps derived from CT resulting in a mean relative difference less than 7%

  9. Classification of bones from MR images in torso PET-MR imaging using a statistical shape model

    Energy Technology Data Exchange (ETDEWEB)

    Reza Ay, Mohammad, E-mail: mohammadreza_ay@tums.ac.ir [Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Akbarzadeh, Afshin [Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Ahmadian, Alireza [Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Research Center for Biomedical Technology and Robotics, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Zaidi, Habib [Geneva University Hospital, Division of Nuclear Medicine and Molecular Imaging, CH-1211 Geneva (Switzerland); Geneva Neuroscience Center, Geneva University, CH-1205 Geneva (Switzerland); Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, 9700 RB Groningen (Netherlands)

    2014-01-11

    of 20 clinical studies was designed. Using this training set, a bone atlas was trained taking advantage of PCA analysis. Our active shape segmentation technique uses the trained shape model to segment bones from user defined initial seed points. The segmentation algorithm was evaluated using 10 clinical datasets (aligned MR and CT pairs). The resulting attenuation maps were compared to corresponding attenuation maps derived from CT resulting in a mean relative difference less than 7%.

  10. Generation of a statistical shape model with probabilistic point correspondences and the expectation maximization- iterative closest point algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Hufnagel, Heike [Institut National de Recherche en Informatique et en Automatique (INRIA), Asclepios Project, Sophia Antipolis (France); University Medical Center Hamburg-Eppendorf, Department of Medical Informatics, Hamburg (Germany); Pennec, Xavier; Ayache, Nicholas [Institut National de Recherche en Informatique et en Automatique (INRIA), Asclepios Project, Sophia Antipolis (France); Ehrhardt, Jan; Handels, Heinz [University Medical Center Hamburg-Eppendorf, Department of Medical Informatics, Hamburg (Germany)

    2008-03-15

    Identification of point correspondences between shapes is required for statistical analysis of organ shapes differences. Since manual identification of landmarks is not a feasible option in 3D, several methods were developed to automatically find one-to-one correspondences on shape surfaces. For unstructured point sets, however, one-to-one correspondences do not exist but correspondence probabilities can be determined. A method was developed to compute a statistical shape model based on shapes which are represented by unstructured point sets with arbitrary point numbers. A fundamental problem when computing statistical shape models is the determination of correspondences between the points of the shape observations of the training data set. In the absence of landmarks, exact correspondences can only be determined between continuous surfaces, not between unstructured point sets. To overcome this problem, we introduce correspondence probabilities instead of exact correspondences. The correspondence probabilities are found by aligning the observation shapes with the affine expectation maximization-iterative closest points (EM-ICP) registration algorithm. In a second step, the correspondence probabilities are used as input to compute a mean shape (represented once again by an unstructured point set). Both steps are unified in a single optimization criterion which depe nds on the two parameters 'registration transformation' and 'mean shape'. In a last step, a variability model which best represents the variability in the training data set is computed. Experiments on synthetic data sets and in vivo brain structure data sets (MRI) are then designed to evaluate the performance of our algorithm. The new method was applied to brain MRI data sets, and the estimated point correspondences were compared to a statistical shape model built on exact correspondences. Based on established measures of 'generalization ability' and &apos

  11. Generation of a statistical shape model with probabilistic point correspondences and the expectation maximization- iterative closest point algorithm

    International Nuclear Information System (INIS)

    Identification of point correspondences between shapes is required for statistical analysis of organ shapes differences. Since manual identification of landmarks is not a feasible option in 3D, several methods were developed to automatically find one-to-one correspondences on shape surfaces. For unstructured point sets, however, one-to-one correspondences do not exist but correspondence probabilities can be determined. A method was developed to compute a statistical shape model based on shapes which are represented by unstructured point sets with arbitrary point numbers. A fundamental problem when computing statistical shape models is the determination of correspondences between the points of the shape observations of the training data set. In the absence of landmarks, exact correspondences can only be determined between continuous surfaces, not between unstructured point sets. To overcome this problem, we introduce correspondence probabilities instead of exact correspondences. The correspondence probabilities are found by aligning the observation shapes with the affine expectation maximization-iterative closest points (EM-ICP) registration algorithm. In a second step, the correspondence probabilities are used as input to compute a mean shape (represented once again by an unstructured point set). Both steps are unified in a single optimization criterion which depe nds on the two parameters 'registration transformation' and 'mean shape'. In a last step, a variability model which best represents the variability in the training data set is computed. Experiments on synthetic data sets and in vivo brain structure data sets (MRI) are then designed to evaluate the performance of our algorithm. The new method was applied to brain MRI data sets, and the estimated point correspondences were compared to a statistical shape model built on exact correspondences. Based on established measures of ''generalization ability'' and ''specificity'', the estimates were very satisfactory

  12. Experimental characterization and modeling of a three-variant magnetic shape memory alloy

    Science.gov (United States)

    Feigenbaum, Heidi P.; Ciocanel, Constantin; Eberle, J. Lance; Dikes, Jason L.

    2016-10-01

    Researchers have attempted to characterize and predict the magneto-mechanical behavior of magnetic shape memory alloys (MSMAs) for over a decade. However, all prior experimental investigations on MSMA have been performed on samples accommodating two martensite variants and generally the MSMA is only exposed to two-dimensional magneto-mechanical loading. As efforts have been underway to develop models able to predict the most general (i.e. 3D) loading conditions for MSMAs with three-varints, there is also a need for experimental data to support the calibration and validation of these models. This paper presents magneto-mechanical data from experiments where MSMA specimens, whose microstructure accommodates three martensite variants, is subjected to three-dimensional magneto-mechanical loading, along with model predictions of these experimental results. The 3D magneto-mechanical model deployed here is a modified version of the model developed by our group (LaMaster et al 2015 J. Intell. Mater. Syst. Struct. 26 663-79), and assumes that three martensite variants coexist in the material. The LaMaster et al model captures some of the general trends seen in the experimental data, but does not predict the data with a high degree of accuracy. Possible reasons for the mismatch between experimental data and model predictions are discussed.

  13. An anatomically shaped lower body model for CT scanning of cadaver femurs

    Energy Technology Data Exchange (ETDEWEB)

    Tanck, Esther; Deenen, J C W; Verdonschot, Nico [Orthopaedic Research Laboratory, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen (Netherlands); Huisman, Henk Jan [Department of Radiology, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands); Kooloos, Jan G [Department of Anatomy, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands); Huizenga, Henk [Department of Radiotherapy, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands)], E-mail: e.tanck@orthop.umcn.nl

    2010-01-21

    Bone specific, CT-based finite element (FE) analyses have great potential to accurately predict the fracture risk of deteriorated bones. However, it has been shown that differences exist between FE-models of femora scanned in a water basin or scanned in situ within the human body, as caused by differences in measured bone mineral densities (BMD). In this study we hypothesized that these differences can be reduced by re-creating the patient CT-conditions by using an anatomically shaped physical model of the lower body. BMD distributions were obtained from four different femora that were scanned under three conditions: (1) in situ within the cadaver body, (2) in a water basin and (3) in the body model. The BMD of the three scanning protocols were compared at two locations: proximally, in the trabecular bone of the femoral head, and in the cortical bone of the femoral shaft. Proximally, no significant differences in BMD were found between the in situ scans and the scans in the body model, whereas the densities from the water basin scans were on average 10.8% lower than in situ. In the femoral shaft the differences between the three scanning protocols were insignificant. In conclusion, the body model better approached the in situ situation than a water basin. Future studies can use this body model to mimic patient situations and to develop protocols to improve the performance of the FE-models in actual patients. (note)

  14. Poly(glycerol sebacate urethane)-cellulose nanocomposites with water-active shape-memory effects.

    Science.gov (United States)

    Wu, Tongfei; Frydrych, Martin; O'Kelly, Kevin; Chen, Biqiong

    2014-07-14

    Biodegradable and biocompatible materials with shape-memory effects (SMEs) are attractive for use as minimally invasive medical devices. Nanocomposites with SMEs were prepared from biodegradable poly(glycerol sebacate urethane) (PGSU) and renewable cellulose nanocrystals (CNCs). The effects of CNC content on the structure, water absorption, and mechanical properties of the PGSU were studied. The water-responsive mechanically adaptive properties and shape-memory performance of PGSU-CNC nanocomposites were observed, which are dependent on the content of CNCs. The PGSU-CNC nanocomposite containing 23.2 vol % CNCs exhibited the best SMEs among the nanocomposites investigated, with the stable shape fixing and shape recovery ratios being 98 and 99%, respectively, attributable to the formation of a hydrophilic, yet strong, CNC network in the elastomeric matrix. In vitro degradation profiles of the nanocomposites were assessed with and without the presence of an enzyme. PMID:24877559

  15. Tomographic active optical trapping of arbitrarily shaped objects by exploiting 3-D refractive index maps

    CERN Document Server

    Kim, Kyoohyun

    2016-01-01

    Optical trapping can be used to manipulate the three-dimensional (3-D) motion of spherical particles based on the simple prediction of optical forces and the responding motion of samples. However, controlling the 3-D behaviour of non-spherical particles with arbitrary orientations is extremely challenging, due to experimental difficulties and the extensive computations. Here, we achieved the real-time optical control of arbitrarily shaped particles by combining the wavefront shaping of a trapping beam and measurements of the 3-D refractive index (RI) distribution of samples. Engineering the 3-D light field distribution of a trapping beam based on the measured 3-D RI map of samples generates a light mould, which can be used to manipulate colloidal and biological samples which have arbitrary orientations and/or shapes. The present method provides stable control of the orientation and assembly of arbitrarily shaped particles without knowing a priori information about the sample geometry. The proposed method can ...

  16. Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kun-Dar, E-mail: kundar@mail.nutn.edu.tw; Chen, Kwanyu [Department of Materials Science, National University of Tainan, Tainan 700, Taiwan (China)

    2015-11-15

    In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.

  17. Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

    Directory of Open Access Journals (Sweden)

    Kun-Dar Li

    2015-11-01

    Full Text Available In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.

  18. Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

    Science.gov (United States)

    Li, Kun-Dar; Chen, Kwanyu

    2015-11-01

    In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.

  19. An Approach to 3d Digital Modeling of Surfaces with Poor Texture by Range Imaging Techniques. `SHAPE from Stereo' VS. `SHAPE from Silhouette' in Digitizing Jorge Oteiza's Sculptures

    Science.gov (United States)

    García Fernández, J.; Álvaro Tordesillas, A.; Barba, S.

    2015-02-01

    Despite eminent development of digital range imaging techniques, difficulties persist in the virtualization of objects with poor radiometric information, in other words, objects consisting of homogeneous colours (totally white, black, etc.), repetitive patterns, translucence, or materials with specular reflection. This is the case for much of the Jorge Oteiza's works, particularly in the sculpture collection of the Museo Fundación Jorge Oteiza (Navarra, Spain). The present study intend to analyse and asses the performance of two digital 3D-modeling methods based on imaging techniques, facing cultural heritage in singular cases, determined by radiometric characteristics as mentioned: Shape from Silhouette and Shape from Stereo. On the other hand, the text proposes the definition of a documentation workflow and presents the results of its application in the collection of sculptures created by Oteiza.

  20. A computational model that recovers the 3D shape of an object from a single 2D retinal representation.

    Science.gov (United States)

    Li, Yunfeng; Pizlo, Zygmunt; Steinman, Robert M

    2009-05-01

    Human beings perceive 3D shapes veridically, but the underlying mechanisms remain unknown. The problem of producing veridical shape percepts is computationally difficult because the 3D shapes have to be recovered from 2D retinal images. This paper describes a new model, based on a regularization approach, that does this very well. It uses a new simplicity principle composed of four shape constraints: viz., symmetry, planarity, maximum compactness and minimum surface. Maximum compactness and minimum surface have never been used before. The model was tested with random symmetrical polyhedra. It recovered their 3D shapes from a single randomly-chosen 2D image. Neither learning, nor depth perception, was required. The effectiveness of the maximum compactness and the minimum surface constraints were measured by how well the aspect ratio of the 3D shapes was recovered. These constraints were effective; they recovered the aspect ratio of the 3D shapes very well. Aspect ratios recovered by the model were compared to aspect ratios adjusted by four human observers. They also adjusted aspect ratios very well. In those rare cases, in which the human observers showed large errors in adjusted aspect ratios, their errors were very similar to the errors made by the model. PMID:18621410

  1. Modeling the Influence of Antifreeze Proteins on Three-Dimensional Ice Crystal Melt Shapes using a Geometric Approach

    CERN Document Server

    Liu, Jun Jie; Dolev, Maya Bar; Celik, Yeliz; Wettlaufer, J S; Braslavsky, Ido

    2012-01-01

    The melting of pure axisymmetric ice crystals has been described previously by us within the framework of so-called geometric crystal growth. Nonequilibrium ice crystal shapes evolving in the presence of hyperactive antifreeze proteins (hypAFPs) are experimentally observed to assume ellipsoidal geometries ("lemon" or "rice" shapes). To analyze such shapes we harness the underlying symmetry of hexagonal ice Ih and extend two-dimensional geometric models to three-dimensions to reproduce the experimental dissolution process. The geometrical model developed will be useful as a quantitative test of the mechanisms of interaction between hypAFPs and ice.

  2. TENSILE TEST AND PHYSICAL MODEL OF NiTi SHAPE MEMORY ALLOY

    Institute of Scientific and Technical Information of China (English)

    HUZi-li; WANGXin-wei; XIONGKe

    2004-01-01

    The tensile stress-strain curves of NiTi wires are obtained by tensile experiments under different heat treatments. A phenomenological physical model based on hysteresis element method is developed to describe the experimentally determined stress-strain curves of shape memory alloy (SMA) wires. Numerical simulations are made. Simulation results show that:(1) a series of unusual changes on physical and mechanical properties of SMA wires occur when martensitic, especially R (rhombohedral) phase transformation emerge. The stress-strain relation of SMA wires is highly non-linear; (2) there are no notable yielding phenomena before NiTi wires are broken; (3) numerical results obtained by the physical model are in good agreement with experimental data.

  3. A parabolic model to control quantum interference in T-shaped molecular junctions

    DEFF Research Database (Denmark)

    Nozaki, Daijiro; Sevincli, Haldun; Avdoshenko, Stanislav M.;

    2013-01-01

    to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal...... resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group...... and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions....

  4. Cohesive granular media modelization with non-convex particles shape: Application to UO2 powder compaction

    International Nuclear Information System (INIS)

    We model in this work granular materials composed of non-convex and cohesive aggregates, in view of application to the rheology of UO2 powders. The effect of non convexity is analyzed in terms of bulk quantities (Coulomb internal friction and cohesion) and micromechanical parameters such as texture anisotropy and force transmission. In particular, we find that the packing fraction evolves in a complex manner with the shape non convexity and the shear strength increases but saturates due to interlocking between the aggregates. We introduce simple models to describe these features in terms of micro-mechanical parameters. Furthermore, a systematic investigation of shearing, uniaxial compaction and simple compression of cohesive packings show that bulk cohesion increases with non-convexity but is strongly influenced by the boundary conditions and shear bands or stress concentration. (author)

  5. A model for shape memory alloys with the possibility of voids

    CERN Document Server

    Fremond, Michel

    2009-01-01

    The paper is devoted to the study of a mathematical model for the thermomechanical evolution of metallic shape memory alloys. The main novelty of our approach consists in the fact that we include the possibility for these materials to exhibit voids during the phase change process. Indeed, in the engineering paper has been recently proved that voids may appear when the mixture is produced by the aggregations of powder. Hence, the composition of the mixture varies (under either thermal or mechanical actions) in this way: the martensites and the austenite transform into one another whereas the voids volume fraction evolves. The first goal of this contribution is hence to state a PDE system capturing all these modelling aspects in order then to establish the well-posedness of the associated initial-boundary value problem.

  6. Thermal Properties and an Improved Shape Model for Near-Earth Asteroid (162421) 2000 ET70

    CERN Document Server

    Marshall, Sean E; Magri, Christopher; Vervack, Ronald J; Campbell, Donald B; Fernández, Yanga R; Nolan, Michael C; Crowell, Jenna L; Hicks, Michael D; Lawrence, Kenneth J; Taylor, Patrick A

    2016-01-01

    We present thermal properties and an improved shape model for potentially hazardous asteroid (162421) 2000 ET70. In addition to the radar data from 2000 ET70's apparition in 2012, our model incorporates optical lightcurves and infrared spectra that were not included in the analysis of Naidu et al. (2013, Icarus 226, 323-335). We confirm the general "clenched fist" appearance of the previous model but find the asteroid's dimensions to be somewhat different at 2.90 km $\\times$ 2.24 km $\\times$ 1.50 km. In particular, the lightcurves favor a model that is significantly shorter along its z-axis (rotation axis) than the model of Naidu et al. With the available data, 2000 ET70's period and pole position are degenerate with each other. The radar and lightcurve data together constrain the pole direction to fall along an arc that is about thirty degrees long and nine degrees wide. Infrared spectra from the NASA InfraRed Telescope Facility (IRTF) provide an additional constraint on the pole. Thermophysical modeling, us...

  7. Face to Face: Anthropometry-Based Interactive Face Shape Modeling Using Model Priors

    OpenAIRE

    Yu Zhang; Prakash, Edmond C.

    2009-01-01

    This paper presents a new anthropometrics-based method for generating realistic, controllable face models. Our method establishes an intuitive and efficient interface to facilitate procedures for interactive 3D face modeling and editing. It takes 3D face scans as examples in order to exploit the variations presented in the real faces of individuals. The system automatically learns a model prior from the data-sets of example meshes of facial features using principal compon...

  8. How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

    Science.gov (United States)

    Corbi, Fabio; Rivalta, Eleonora; Pinel, Virginie; Maccaferri, Francesco; Bagnardi, Marco; Acocella, Valerio

    2016-04-01

    Calderas are topographic depressions formed by the collapse of a partly drained magma reservoir. At volcanic edifices with calderas, eruptive fissures can circumscribe the outer caldera rim, be oriented radially and/or align with the regional tectonic stress field. Constraining the mechanisms that govern this spatial arrangement is fundamental to understand the dynamics of shallow magma storage and transport and evaluate volcanic hazard. Here we use numerical models to show that the previously unappreciated unloading effect of caldera formation may contribute significantly to the stress budget of a volcano. We first test this hypothesis against the ideal case of Fernandina, Galápagos, where previous models only partly explained the peculiar pattern of circumferential and radial eruptive fissures and the geometry of the intrusions determined by inverting the deformation data. We show that by taking into account the decompression due to the caldera formation, the modeled edifice stress field is consistent with all the observation. We then develop a general model for the stress state at volcanic edifices with calderas based on the competition of caldera decompression, magma buoyancy forces and tectonic stresses. These factors control the shallow accumulation of magma in stacked sills, consistently with observations as well as the conditions for the development of circumferential and/or radial eruptive fissures, as observed on active volcanoes. This top-down control exerted by changes in the distribution of mass at the surface allows better understanding of how shallow magma is transferred at active calderas, contributing to forecasting the location and type of opening fissures.

  9. A homotopy-based sparse representation for fast and accurate shape prior modeling in liver surgical planning.

    Science.gov (United States)

    Wang, Guotai; Zhang, Shaoting; Xie, Hongzhi; Metaxas, Dimitris N; Gu, Lixu

    2015-01-01

    Shape prior plays an important role in accurate and robust liver segmentation. However, liver shapes have complex variations and accurate modeling of liver shapes is challenging. Using large-scale training data can improve the accuracy but it limits the computational efficiency. In order to obtain accurate liver shape priors without sacrificing the efficiency when dealing with large-scale training data, we investigate effective and scalable shape prior modeling method that is more applicable in clinical liver surgical planning system. We employed the Sparse Shape Composition (SSC) to represent liver shapes by an optimized sparse combination of shapes in the repository, without any assumptions on parametric distributions of liver shapes. To leverage large-scale training data and improve the computational efficiency of SSC, we also introduced a homotopy-based method to quickly solve the L1-norm optimization problem in SSC. This method takes advantage of the sparsity of shape modeling, and solves the original optimization problem in SSC by continuously transforming it into a series of simplified problems whose solution is fast to compute. When new training shapes arrive gradually, the homotopy strategy updates the optimal solution on the fly and avoids re-computing it from scratch. Experiments showed that SSC had a high accuracy and efficiency in dealing with complex liver shape variations, excluding gross errors and preserving local details on the input liver shape. The homotopy-based SSC had a high computational efficiency, and its runtime increased very slowly when repository's capacity and vertex number rose to a large degree. When repository's capacity was 10,000, with 2000 vertices on each shape, homotopy method cost merely about 11.29 s to solve the optimization problem in SSC, nearly 2000 times faster than interior point method. The dice similarity coefficient (DSC), average symmetric surface distance (ASD), and maximum symmetric surface distance measurement

  10. New and updated convex shape models of asteroids based on optical data from a large collaboration network

    CERN Document Server

    Hanuš, J; Oszkiewicz, D A; Behrend, R; Carry, B; Delbo', M; Adam, O; Afonina, V; Anquetin, R; Antonini, P; Arnold, L; Audejean, M; Aurard, P; Bachschmidt, M; Badue, B; Barbotin, E; Barroy, P; Baudouin, P; Berard, L; Berger, N; Bernasconi, L; Bosch, J-G; Bouley, S; Bozhinova, I; Brinsfield, J; Brunetto, L; Canaud, G; Caron, J; Carrier, F; Casalnuovo, G; Casulli, S; Cerda, M; Chalamet, L; Charbonnel, S; Chinaglia, B; Cikota, A; Colas, F; Coliac, J-F; Collet, A; Coloma, J; Conjat, M; Conseil, E; Costa, R; Crippa, R; Cristofanelli, M; Damerdji, Y; Debackere, A; Decock, A; Déhais, Q; Déléage, T; Delmelle, S; Demeautis, C; Dróżdż, M; Dubos, G; Dulcamara, T; Dumont, M; Durkee, R; Dymock, R; del Valle, A Escalante; Esseiva, N; Esseiva, R; Esteban, M; Fauchez, T; Fauerbach, M; Fauvaud, M; Fauvaud, S; Forné, E; Fournel, C; Fradet, D; Garlitz, J; Gerteis, O; Gillier, C; Gillon, M; Giraud, R; Godard, J-P; Goncalves, R; Hamanowa, H; Hamanowa, H; Hay, K; Hellmich, S; Heterier, S; Higgins, D; Hirsch, R; Hodosan, G; Hren, M; Hygate, A; Innocent, N; Jacquinot, H; Jawahar, S; Jehin, E; Jerosimic, L; Klotz, A; Koff, W; Korlevic, P; Kosturkiewicz, E; Krafft, P; Krugly, Y; Kugel, F; Labrevoir, O; Lecacheux, J; Lehký, M; Leroy, A; Lesquerbault, B; Lopez-Gonzales, M J; Lutz, M; Mallecot, B; Manfroid, J; Manzini, F; Marciniak, A; Martin, A; Modave, B; Montaigut, R; Montier, J; Morelle, E; Morton, B; Mottola, S; Naves, R; Nomen, J; Oey, J; Ogłoza, W; Paiella, M; Pallares, H; Peyrot, A; Pilcher, F; Pirenne, J-F; Piron, P; Polinska, M; Polotto, M; Poncy, R; Previt, J P; Reignier, F; Renauld, D; Ricci, D; Richard, F; Rinner, C; Risoldi, V; Robilliard, D; Romeuf, D; Rousseau, G; Roy, R; Ruthroff, J; Salom, P A; Salvador, L; Sanchez, S; Santana-Ros, T; Scholz, A; Séné, G; Skiff, B; Sobkowiak, K; Sogorb, P; Soldán, F; Spiridakis, A; Splanska, E; Sposetti, S; Starkey, D; Stephens, R; Stiepen, A; Stoss, R; Strajnic, J; Teng, J-P; Tumolo, G; Vagnozzi, A; Vanoutryve, B; Vugnon, J M; Warner, B D; Waucomont, M; Wertz, O; Winiarski, M; Wolf, M

    2015-01-01

    Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. This amount already provided a deep insight into physical properties of main-belt asteroids or large collisional families. We aim to increase the number of asteroid shape models and rotation states. Such results are an important input for various further studies such as analysis of asteroid physical properties in different populations, including smaller collisional families, thermophysical modeling, and scaling shape models by disk-resolved images, or stellar occultation data. This provides, in combination with known masses, bulk density estimates, but constrains also theoretical collisional and evolutional models of the Solar System. We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) ...

  11. Shape-memory polymers

    Directory of Open Access Journals (Sweden)

    Marc Behl

    2007-04-01

    Full Text Available Shape-memory polymers are an emerging class of active polymers that have dual-shape capability. They can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus. While shape B is given by the initial processing step, shape A is determined by applying a process called programming. We review fundamental aspects of the molecular design of suitable polymer architectures, tailored programming and recovery processes, and the quantification of the shape-memory effect. Shape-memory research was initially founded on the thermally induced dual-shape effect. This concept has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups on the molecular level. Finally, polymers are introduced that can be multifunctional. Besides their dual-shape capability, these active materials are biofunctional or biodegradable. Potential applications for such materials as active medical devices are highlighted.

  12. Consistent dust and gas models for protoplanetary disks. I. Disk shape, dust settling, opacities, and PAHs

    CERN Document Server

    Woitke, P; Pinte, C; Thi, W -F; Kamp, I; Rab, C; Anthonioz, F; Antonellini, S; Baldovin-Saavedra, C; Carmona, A; Dominik, C; Dionatos, O; Greaves, J; Güdel, M; Ilee, J D; Liebhart, A; Ménard, F; Rigon, L; Waters, L B F M; Aresu, G; Meijerink, R; Spaans, M

    2015-01-01

    We propose a set of standard assumptions for the modelling of Class II and III protoplanetary disks, which includes detailed continuum radiative transfer, thermo-chemical modelling of gas and ice, and line radiative transfer from optical to cm wavelengths. We propose new standard dust opacities for disk models, we present a simplified treatment of PAHs sufficient to reproduce the PAH emission features, and we suggest using a simple treatment of dust settling. We roughly adjust parameters to obtain a model that predicts typical Class II T Tauri star continuum and line observations. We systematically study the impact of each model parameter (disk mass, disk extension and shape, dust settling, dust size and opacity, gas/dust ratio, etc.) on all continuum and line observables, in particular on the SED, mm-slope, continuum visibilities, and emission lines including [OI] 63um, high-J CO lines, (sub-)mm CO isotopologue lines, and CO fundamental ro-vibrational lines. We find that evolved dust properties (large grains...

  13. Hydrothermal synthesis of bamboo-shaped nanosheet KNb{sub 3}O{sub 8} with enhanced photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaobin [Electronic Materials Research Laboratory, International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Kong, Ling Bing [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2015-04-05

    Graphical abstract: A new type of bamboo-shaped KNb{sub 3}O{sub 8} nanosheet was synthesized by using a two-step hydrothermal method. In addition, the photocatalytic degradation performances of the bamboo-shaped KNb{sub 3}O{sub 8} nanosheet and a rod-like KNb{sub 3}O{sub 8} prepared by using molted salt method were also investigated and compared in terms of degradation of Rhodamine B, and the results indicated that the bamboo-shaped KNb{sub 3}O{sub 8} nanosheet had higher photocatalytic activity. Importantly, the crystal structure and morphology diagram of KNb{sub 3}O{sub 8} nanosheet and their photocatalytic degradation performances as well as a possible mechanism for the photocatalytic degradation are shown below. - Highlights: • A new type of bamboo-shaped KNb{sub 3}O{sub 8} nanosheet was synthesized. • The effect of potassium content on the KNb{sub 3}O{sub 8} phase formation has been studied. • The specific surface area, structural and optical characteristics were studied. • The bamboo-shaped nanosheet KNb{sub 3}O{sub 8} exhibits higher photocatalytic activity. - Abstract: A new type of bamboo-shaped KNb{sub 3}O{sub 8} nanosheet was synthesized by using a two-step hydrothermal method. In particular, an effect of potassium content on the phase formation of KNb{sub 3}O{sub 8} in the second-step hydrothermal process at pH = 5–6 was investigated. Specific surface area, structural properties and optical characteristics of the as-synthesized samples were investigated by using Brunauer–Emmett–Teller measurement, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and UV–visible diffuse reflectance. Furthermore, the photocatalytic degradation performances of the bamboo-shaped KNb{sub 3}O{sub 8} nanosheet and a rod-like KNb{sub 3}O{sub 8} prepared by using molted salt method were also investigated and compared in terms of degradation of Rhodamine B, and the results indicated that the bamboo-shaped KNb{sub 3}O{sub 8

  14. Controlled synthesis of T-shaped BiVO{sub 4} and enhanced visible light responsive photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Shuying; Yu, Chongfei; Li, Yukun [School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, Xinxiang, Henan 453007 (China); Li, Yihui [School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Sun, Jianhui, E-mail: sunjh@htu.cn [School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, Xinxiang, Henan 453007 (China); Geng, Xiaofei [School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, Xinxiang, Henan 453007 (China)

    2014-03-15

    A novel T-shaped BiVO{sub 4} microcrystal photocatalyst was successfully synthesized by the hydrothermal method with the aid of a structure-directing surfactant SDBS in the present study. Having received well characterization with the aid of various techniques and the results showed that the SDBS greatly changed the microstructure of BiVO{sub 4}, which had a unique T shape and belonged to the monoclinic family. The fast exchange dynamics between the surfactants bound to the Bi{sup 3+} seed surface and the free VO{sub 3}{sup −} in the solution significantly increase the rate of heterogeneous nucleation. In addition, the photocatalytic activity of the prepared T-shaped BiVO{sub 4} was evaluated by the degradation of Methylene Blue solution under visible light irradiation, 17% and 47% higher decolorization rates than the commercial P25 and BiVO{sub 4} synthesized without SDBS, respectively. Meanwhile, it has been found that the degradation kinetics of MB fitted the pseudo-first-order kinetics and the T-shaped BiVO{sub 4} also displayed high photocatalytic performance for metronidazole degradation. -- Graphical abstract: H{sub 2}O{sub 2} molecules function as electron trapping reagent to react with e{sup −} to enhance the photocatalytic degradation efficiency of MB in the BiVO{sub 4}/H{sub 2}O{sub 2} system under visible light irradiation. Highlights: • T-shaped BiVO{sub 4} was synthesized using SDBS as a structure-directing surfactant. • SDBS greatly changed the microstructure of BiVO{sub 4}. • The T-shaped BiVO{sub 4} had a better visible-light photocatalytic activity. • Degradation kinetics of MB by BiVO{sub 4} fitted the pseudo-first-order kinetics.

  15. Controlled synthesis of T-shaped BiVO4 and enhanced visible light responsive photocatalytic activity

    International Nuclear Information System (INIS)

    A novel T-shaped BiVO4 microcrystal photocatalyst was successfully synthesized by the hydrothermal method with the aid of a structure-directing surfactant SDBS in the present study. Having received well characterization with the aid of various techniques and the results showed that the SDBS greatly changed the microstructure of BiVO4, which had a unique T shape and belonged to the monoclinic family. The fast exchange dynamics between the surfactants bound to the Bi3+ seed surface and the free VO3− in the solution significantly increase the rate of heterogeneous nucleation. In addition, the photocatalytic activity of the prepared T-shaped BiVO4 was evaluated by the degradation of Methylene Blue solution under visible light irradiation, 17% and 47% higher decolorization rates than the commercial P25 and BiVO4 synthesized without SDBS, respectively. Meanwhile, it has been found that the degradation kinetics of MB fitted the pseudo-first-order kinetics and the T-shaped BiVO4 also displayed high photocatalytic performance for metronidazole degradation. -- Graphical abstract: H2O2 molecules function as electron trapping reagent to react with e− to enhance the photocatalytic degradation efficiency of MB in the BiVO4/H2O2 system under visible light irradiation. Highlights: • T-shaped BiVO4 was synthesized using SDBS as a structure-directing surfactant. • SDBS greatly changed the microstructure of BiVO4. • The T-shaped BiVO4 had a better visible-light photocatalytic activity. • Degradation kinetics of MB by BiVO4 fitted the pseudo-first-order kinetics

  16. Noise-shaping all-digital phase-locked loops modeling, simulation, analysis and design

    CERN Document Server

    Brandonisio, Francesco

    2014-01-01

    This book presents a novel approach to the analysis and design of all-digital phase-locked loops (ADPLLs), technology widely used in wireless communication devices. The authors provide an overview of ADPLL architectures, time-to-digital converters (TDCs) and noise shaping. Realistic examples illustrate how to analyze and simulate phase noise in the presence of sigma-delta modulation and time-to-digital conversion. Readers will gain a deep understanding of ADPLLs and the central role played by noise-shaping. A range of ADPLL and TDC architectures are presented in unified manner. Analytical and simulation tools are discussed in detail. Matlab code is included that can be reused to design, simulate and analyze the ADPLL architectures that are presented in the book.   • Discusses in detail a wide range of all-digital phase-locked loops architectures; • Presents a unified framework in which to model time-to-digital converters for ADPLLs; • Explains a procedure to predict and simulate phase noise in oscil...

  17. A comparison of computational models for eukaryotic cell shape and motility.

    Directory of Open Access Journals (Sweden)

    William R Holmes

    Full Text Available Eukaryotic cell motility involves complex interactions of signalling molecules, cytoskeleton, cell membrane, and mechanics interacting in space and time. Collectively, these components are used by the cell to interpret and respond to external stimuli, leading to polarization, protrusion, adhesion formation, and myosin-facilitated retraction. When these processes are choreographed correctly, shape change and motility results. A wealth of experimental data have identified numerous molecular constituents involved in these processes, but the complexity of their interactions and spatial organization make this a challenging problem to understand. This has motivated theoretical and computational approaches with simplified caricatures of cell structure and behaviour, each aiming to gain better understanding of certain kinds of cells and/or repertoire of behaviour. Reaction-diffusion (RD equations as well as equations of viscoelastic flows have been used to describe the motility machinery. In this review, we describe some of the recent computational models for cell motility, concentrating on simulations of cell shape changes (mainly in two but also three dimensions. The problem is challenging not only due to the difficulty of abstracting and simplifying biological complexity but also because computing RD or fluid flow equations in deforming regions, known as a "free-boundary" problem, is an extremely challenging problem in applied mathematics. Here we describe the distinct approaches, comparing their strengths and weaknesses, and the kinds of biological questions that they have been able to address.

  18. TECHNICAL NOTE: Thermal modelling of shape memory alloy fixator for medical application

    Science.gov (United States)

    Song, C.; Campbell, P. A.; Frank, T. G.; Cuschieri, A.

    2002-04-01

    Shape memory alloy has been recently used for tissue fixation in minimal access surgery (MAS). It offers an alternative to conventional thread-based suturing of human tissue, with the advantage that its deployment is faster and requires fewer surgical skills. To minimize the damage to surrounding tissue, thermal analysis of tissue-fixator interactions has been done to optimize the heating method, and to predict the heating effect and affected range. The finite-difference method has been used to solve the one-dimensional transient heat transfer problem, with fixator-tissue conduction boundary condition, and the finite-element method was used to build a three-dimensional model for the design optimization. The predicted temperature responses of tissue are considered within a safety range. Tissue temperature drops quickly after heating, and the affected tissue is limited to a layer 1 mm thick next to the fixator. Further in vivo animal studies on the use of the shape memory alloy fixator are ongoing for future applications of tissue suturing in MAS.

  19. Transformation-induced plasticity in high-temperature shape memory alloys: a one-dimensional continuum model

    Science.gov (United States)

    Sakhaei, Amir Hosein; Lim, Kian-Meng

    2016-07-01

    A constitutive model based on isotropic plasticity consideration is presented in this work to model the thermo-mechanical behavior of high-temperature shape memory alloys. In high-temperature shape memory alloys (HTSMAs), both martensitic transformation and rate-dependent plasticity (creep) occur simultaneously at high temperatures. Furthermore, transformation-induced plasticity is another deformation mechanism during martensitic transformation. All these phenomena are considered as dissipative processes to model the mechanical behavior of HTSMAs in this study. The constitutive model was implemented for one-dimensional cases, and the results have been compared with experimental data from thermal cycling test for actuator applications.

  20. On-Demand Removal of Bacterial Biofilms via Shape Memory Activation.

    Science.gov (United States)

    Gu, Huan; Lee, Sang Won; Buffington, Shelby Lois; Henderson, James H; Ren, Dacheng

    2016-08-24

    Bacterial biofilms are a major cause of chronic infections and biofouling; however, effective removal of established biofilms remains challenging. Here we report a new strategy for biofilm control using biocompatible shape memory polymers with defined surface topography. These surfaces can both prevent bacterial adhesion and remove established biofilms upon rapid shape change with moderate increase of temperature, thereby offering more prolonged antifouling properties. We demonstrate that this strategy can achieve a total reduction of Pseudomonas aeruginosa biofilms by 99.9% compared to the static flat control. It was also found effective against biofilms of Staphylococcus aureus and an uropathogenic strain of Escherichia coli.

  1. On-Demand Removal of Bacterial Biofilms via Shape Memory Activation.

    Science.gov (United States)

    Gu, Huan; Lee, Sang Won; Buffington, Shelby Lois; Henderson, James H; Ren, Dacheng

    2016-08-24

    Bacterial biofilms are a major cause of chronic infections and biofouling; however, effective removal of established biofilms remains challenging. Here we report a new strategy for biofilm control using biocompatible shape memory polymers with defined surface topography. These surfaces can both prevent bacterial adhesion and remove established biofilms upon rapid shape change with moderate increase of temperature, thereby offering more prolonged antifouling properties. We demonstrate that this strategy can achieve a total reduction of Pseudomonas aeruginosa biofilms by 99.9% compared to the static flat control. It was also found effective against biofilms of Staphylococcus aureus and an uropathogenic strain of Escherichia coli. PMID:27517738

  2. Principal component analysis in construction of 3D human knee joint models using a statistical shape model method.

    Science.gov (United States)

    Tsai, Tsung-Yuan; Li, Jing-Sheng; Wang, Shaobai; Li, Pingyue; Kwon, Young-Min; Li, Guoan

    2015-01-01

    The statistical shape model (SSM) method that uses 2D images of the knee joint to predict the three-dimensional (3D) joint surface model has been reported in the literature. In this study, we constructed a SSM database using 152 human computed tomography (CT) knee joint models, including the femur, tibia and patella and analysed the characteristics of each principal component of the SSM. The surface models of two in vivo knees were predicted using the SSM and their 2D bi-plane fluoroscopic images. The predicted models were compared to their CT joint models. The differences between the predicted 3D knee joint surfaces and the CT image-based surfaces were 0.30 ± 0.81 mm, 0.34 ± 0.79 mm and 0.36 ± 0.59 mm for the femur, tibia and patella, respectively (average ± standard deviation). The computational time for each bone of the knee joint was within 30 s using a personal computer. The analysis of this study indicated that the SSM method could be a useful tool to construct 3D surface models of the knee with sub-millimeter accuracy in real time. Thus, it may have a broad application in computer-assisted knee surgeries that require 3D surface models of the knee.

  3. Modeling the coupling between martensitic phase transformation and plasticity in shape memory alloys

    Science.gov (United States)

    Manchiraju, Sivom

    The thermo-mechanical response of NiTi shape memory alloys (SMAs) is predominantly dictated by two inelastic deformation processes---martensitic phase transformation and plastic deformation. This thesis presents a new microstructural finite element (MFE) model that couples these processes and anisotropic elasticity. The coupling occurs via the stress redistribution induced by each mechanism. The approach includes three key improvements to the literature. First, transformation and plasticity are modeled at a crystallographic level and can occur simultaneously. Second, a rigorous large-strain finite element formulation is used, thereby capturing texture development (crystal rotation). Third, the formulation adopts recent first principle calculations of monoclinic martensite stiffness. The model is calibrated to experimental data for polycrystalline NiTi (49.9 at% Ni). Inputs include anisotropic elastic properties, texture, and DSC data as well as a subset of pseudoelastic and load-biased thermal cycling data. This calibration process provides updated material values---namely, larger self-hardening between similar martensite plates. It is then assessed against additional pseudoelastic and load-biased thermal cycling experimental data and neutron diffraction measurements of martensite texture evolution. Several experimental trends are captured---in particular, the transformation strain during thermal cycling monotonically increases with increasing bias stress, reaching a peak and then decreasing due to intervention of plasticity---a trend which existing MFE models are unable to capture. Plasticity is also shown to enhance stress-induced martensite formation during loading and generate retained martensite upon unloading. The simulations even enable a quantitative connection between deformation processing and two-way shape memory effect. Some experimental trends are not captured---in particular, the ratcheting of macrostrain with repeated thermal cycling. This may

  4. Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

    Science.gov (United States)

    Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David

    2016-07-01

    This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl-Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

  5. A validated model for induction heating of shape memory alloy actuators

    Science.gov (United States)

    Saunders, Robert N.; Boyd, James G.; Hartl, Darren J.; Brown, Jonathan K.; Calkins, Frederick T.; Lagoudas, Dimitris C.

    2016-04-01

    Shape memory alloy (SMA) actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. One disadvantage of these thermally driven actuators is their slow cyclic time response compared to conventional actuators. Induction heating has recently been proposed to quickly heat SMA components. However efforts to date have been purely empirical. The present work approachs this problem in a computational manner by developing a finite element model of induction heating in which the time-harmonic electromagnetic equations are solved for the Joule heat power field, the energy equation is solved for the temperature field, and the linear momentum equations are solved to find the stress, displacement, and internal state variable fields. The combined model was implemented in Abaqus using a Python script approach and applied to SMA torque tube and beam actuators. The model has also been used to examine magnetic flux concentrators to improve the induction systems performance. Induction heating experiments were performed using the SMA torque tube, and the model agreed well with the experiments.

  6. Shape Optimization of Hollow Concrete Blocks Using the Lattice Discrete Particle Model

    Directory of Open Access Journals (Sweden)

    Fatemeh Javidan

    2013-01-01

    Full Text Available Hollow concrete blocks are one of the widely used building elements of masonry structures in whichthey are normally loaded under combined action of shear and compression. Accordingly and due to theirstructural importance, the present study intends to numerically search for an optimum shape of such blocks.The optimality index is selected to be the ratio of block’s failure strength to its weight, a non-dimensionalparameter, which needs to be maximized. The nonlinear analysis has been done using a homemade code writtenbased on the recently developed Lattice Discrete Particle Model (LDPM for the meso-scale simulation ofconcrete. This numerical approach accounts for the different aspects of concrete’s complex behavior such astensile fracturing, cohesive and frictional shearing and also its nonlinear compressive response. The modelparameters were calibrated against previously reported experimental data. Various two-core configurations forthe hollow blocks are examined, compared and discussed.

  7. Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

    Science.gov (United States)

    Sun, Chunya; Song, Baowei; Wang, Peng

    2015-11-01

    Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

  8. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    Science.gov (United States)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  9. Scaling the Mode Shapes of a Building Model by Mass Changes

    DEFF Research Database (Denmark)

    Brincker, Rune; Rodrigues, J.; Andersen, P.

    2004-01-01

    It is well known, that when using natural input modal analysis, the loads are not known, and thus, the mode scaling factor that relates the magnitude of the loading to the magnitude of the response cannot be estimated. However It has been pointed out by several theoretical papers that mode shapes...... change technique can be used on a ¼ scale model of a 4-storey building. The uncertainties on the estimated scaling factors are illustrated by repeating the estimation using different mass changes....... can be scaled by performing  several natural input modal analysis tests with different mass changes, observe the frequency shift introduced by the mass changes and then follow an estimation scheme that allows the user to estimate the scaling factor modeby- mode, i.e. only information of the particular...

  10. Corpus Callosum Analysis using MDL-based Sequential Models of Shape and Appearance

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Davies, Rhodri H.; Ryberg, Charlotte

    2004-01-01

    This paper describes a method for automatically analysing and segmenting the corpus callosum from magnetic resonance images of the brain based on the widely used Active Appearance Models (AAMs) by Cootes et al. Extensions of the original method, which are designed to improve this specific case...... are proposed, but all remain applicable to other domain problems. The well-known multi-resolution AAM optimisation is extended to include sequential relaxations on texture resolution, model coverage and model parameter constraints. Fully unsupervised analysis is obtained by exploiting model parameter...

  11. Shape dependency of the extinction and absorption cross sections of dust aerosols modeled as randomly oriented spheroids

    Directory of Open Access Journals (Sweden)

    R. Wagner

    2011-09-01

    Full Text Available We present computational results on the shape dependency of the extinction and absorption cross sections of dustlike aerosol particles that were modeled as randomly oriented spheroids. Shape dependent variations in the extinction cross sections are largest in the size regime that is governed by the interference structure. Elongated spheroids best fitted measured extinction spectra of re-dispersed Saharan dust samples. For dust particles smaller than 1.5 μm in diameter and low absorption potential, shape effects on the absorption cross sections are very small.

  12. Investigations into Haptic Space and Haptic Perception of Shape for Active Touch

    NARCIS (Netherlands)

    Sanders, A.F.J.

    2008-01-01

    This thesis presents a number of psychophysical investigations into haptic space and haptic perception of shape. Haptic perception is understood to include the two subsystems of the cutaneous sense and kinesthesis. Chapter 2 provides an extensive quantitative study into haptic perception of curvatur

  13. Transport phenomena in a model cheese: the influence of the charge and shape of solutes on diffusion.

    Science.gov (United States)

    Silva, J V C; Peixoto, P D S; Lortal, S; Floury, J

    2013-10-01

    During cheese ripening, microorganisms grow as immobilized colonies, metabolizing substrates present in the matrix and generating products from enzymatic reactions. Local factors that limit the rates of diffusion, either within the general cheese matrix or near the colonies, may influence the metabolic activity of the bacteria during ripening, affecting the final quality of the cheese. The objective of this study was to determine the diffusion coefficients of solutes as a function of their different physicochemical characteristics (size, charge, and shape) in an ultrafiltrate (UF) model cheese (based on ultrafiltered milk) to enable better understanding of the ripening mechanisms. Diffusion coefficients of fluorescein isothiocyanate (FITC)-dextrans (4 kDa to 2 MDa) and FITC-labeled dairy proteins (α-lactalbumin, β-lactoglobulin, and BSA) were measured using the technique of fluorescence recovery after photobleaching (FRAP). This study showed that macromolecules up to 2 MDa and proteins could diffuse through the UF model cheese. The larger FITC-dextrans were not more hindered by the structure of the UF model cheese compared with the smaller ones. Any decrease in the diffusion coefficients of solutes was related only to their hydrodynamic radii. The FITC-dextran diffusion data were fitted to an obstruction model, resulting in a constant obstruction factor (k ~0.42). Diffusion in the model cheese was sensitive to the physicochemical characteristics of the solute. The FITC-dairy proteins studied (rigid and negatively charged molecules) were hindered to a greater degree than the FITC-dextrans (flexible and charge-neutral molecules) in the UF model cheese. The existence of steric and electrostatic interactions between the protein matrix of the UF model cheese and the FITC-dairy proteins could explain the decrease in diffusion compared with FITC-dextrans.

  14. The formation of an inverse S-shaped active-region filament driven by sunspot motion and magnetic reconnection

    CERN Document Server

    Yan, X L; Guo, Q L; Xue, Z K; Wang, J C; Yang, L H

    2016-01-01

    We present a detailed study of the formation of an inverse S-shaped filament prior to its eruption in active region NOAA 11884 from October 31 to November 2, 2013. In the initial stage, clockwise rotation of a small positive sunspot around the main negative trailing sunspot formed a curved filament. Then the small sunspot cancelled with negative magnetic flux to create a longer active-region filament with an inverse S-shape. At the cancellation site a brightening was observed in UV and EUV images and bright material was transferred to the filament. Later the filament erupted after cancellation of two opposite polarities under the upper part of the filament. Nonlinear force-free field (NLFFF) extrapolation of vector photospheric fields suggests that the filament may have a twisted structure, but this cannot be confirmed from the current observations.

  15. Human performance modeling for system of systems analytics: combat performance-shaping factors.

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, Craig R.; Miller, Dwight Peter

    2006-01-01

    The US military has identified Human Performance Modeling (HPM) as a significant requirement and challenge of future systems modeling and analysis initiatives. To support this goal, Sandia National Laboratories (SNL) has undertaken a program of HPM as an integral augmentation to its system-of-system (SoS) analytics capabilities. The previous effort, reported in SAND2005-6569, evaluated the effects of soldier cognitive fatigue on SoS performance. The current effort began with a very broad survey of any performance-shaping factors (PSFs) that also might affect soldiers performance in combat situations. The work included consideration of three different approaches to cognition modeling and how appropriate they would be for application to SoS analytics. This bulk of this report categorizes 47 PSFs into three groups (internal, external, and task-related) and provides brief descriptions of how each affects combat performance, according to the literature. The PSFs were then assembled into a matrix with 22 representative military tasks and assigned one of four levels of estimated negative impact on task performance, based on the literature. Blank versions of the matrix were then sent to two ex-military subject-matter experts to be filled out based on their personal experiences. Data analysis was performed to identify the consensus most influential PSFs. Results indicate that combat-related injury, cognitive fatigue, inadequate training, physical fatigue, thirst, stress, poor perceptual processing, and presence of chemical agents are among the PSFs with the most negative impact on combat performance.

  16. Dynamics of asteroid family halos constrained by spin/shape models

    Science.gov (United States)

    Broz, Miroslav

    2016-10-01

    A number of asteroid families cannot be identified solely on the basis of the Hierarchical Clustering Method (HCM), because they have additional 'former' members in the surroundings which constitute a so called halo (e.g. Broz & Morbidelli 2013). They are usually mixed up with the background population which has to be taken into account too.Luckily, new photometric observations allow to derive new spin/shape models, which serve as independent constraints for dynamical models. For example, a recent census of the Eos family shows 43 core and 27 halo asteroids (including background) with known spin orientations.To this point, we present a complex spin-orbital model which includes full N-body dynamics and consequently accounts for all mean-motion, secular, or three-body gravitational resonances, the Yarkovsky drift, YORP effect, collisional reorientations and also spin-orbital interactions. These are especially important for the Koronis family. In this project, we make use of data from the DAMIT database and ProjectSoft Blue Eye 600 observatory.

  17. Analysis of shape memory alloy sensory particles for damage detection via substructure and continuum damage modeling

    Science.gov (United States)

    Bielefeldt, Brent R.; Benzerga, A. Amine; Hartl, Darren J.

    2016-04-01

    The ability to monitor and predict the structural health of an aircraft is of growing importance to the aerospace industry. Currently, structural inspections and maintenance are based upon experiences with similar aircraft operating in similar conditions. While effective, these methods are time-intensive and unnecessary if the aircraft is not in danger of structural failure. It is imagined that future aircraft will utilize non-destructive evaluation methods, allowing for the near real-time monitoring of structural health. A particularly interesting method involves utilizing the unique transformation response of shape memory alloy (SMA) particles embedded in an aircraft structure. By detecting changes in the mechanical and/or electromagnetic responses of embedded particles, operators could detect the formation or propagation of fatigue cracks in the vicinity of these particles. This work focuses on a finite element model of SMA particles embedded in an aircraft wing using a substructure modeling approach in which degrees of freedom are retained only at specified points of connection to other parts or the application of boundary conditions, greatly reducing computational cost. Previous work evaluated isolated particle response to a static crack to numerically demonstrate and validate this damage detection method. This paper presents the implementation of a damage model to account for crack propagation and examine for the first time the effect of particle configuration and/or relative placement with respect to the ability to detect damage.

  18. U(5)-SU(3) nuclear shape transition within the interacting boson model applied to dysprosium isotopes

    Science.gov (United States)

    Kotb, M.

    2016-07-01

    In the framework of the interacting boson model (IBM) with intrinsic coherent state, the shape Hamiltonian from spherical vibrator U(5) to axially symmetric prolate deformed rotator SU(3) are examined. The Hamiltonian used is composed of a single boson energy term and quadrupole term. The potential energy surfaces (PES' s) corresponding to the U(5)-SU(3) transition are calculated with variation of a scaling and control parameters. The model is applied to 150-162Dy chain of isotopes. In this chain a change from spherical to well deformed nuclei is observed when moving from the lighter to heavier isotopes. 156Dy is a good candidate for the critical point symmetry X(5). The parameters of the model are determined by using a computer simulated search program in order to minimize the deviation between our calculated and some selected experimental energy levels, B(E2) transition rates and the two neutron separation energies S2n. We have also studied the energy ratios and the B(E2) values for the yrast state of the critical nucleus. The nucleon pair transfer intensities between ground-ground and ground-beta states are examined within IBM and boson intrinsic coherent framework.

  19. Evolution of ground state nuclear shapes in tungsten nuclei in terms of interacting boson model

    Science.gov (United States)

    Khalaf, A. M.; El-Shal, A. O.; Taha, M. M.; El-Sayed, M. A.

    2016-03-01

    The tungsten nuclei 180-190W are investigated within the framework of the interacting boson model using an intrinsic coherent state formalism. The Hamiltonian operator contains only multipole operators of the subalgebra associated with the dynamical symmetries SU(3) and O(6). The study includes the behavior of potential energy surfaces (BES's) and critical points in the space of the model parameters to declare the geometric character of the tungsten isotopic chain. Some selected energy levels and reduced E2 transition probabilities B(E2) for each nucleus are calculated to adjust the model parameters by using a computer code PH INT and simulated computer fitting programme to fit the experimental data with the IBM calculation by minimizing the root mean square deviations. The 180-190W isotopes lies in shape transition SU(3)-O(6) region of the IBM such that the lighter isotopes comes very clare to the SU(3) limit, while the behavior ones tend to be near the γ-unstable O(6) limit.

  20. Modelling and assessment of dependent performance shaping factors through Analytic Network Process

    Energy Technology Data Exchange (ETDEWEB)

    De Ambroggi, Massimiliano, E-mail: massimiliano.deambroggi@mail.polimi.i [Politecnico di Milano, Department of Management, Economics and Industrial Engineering, Piazza Leonardo da Vinci 32, Milan 20132 (Italy); Trucco, Paolo [Politecnico di Milano, Department of Management, Economics and Industrial Engineering, Piazza Leonardo da Vinci 32, Milan 20132 (Italy)

    2011-07-15

    Despite continuous progresses in research and applications, one of the major weaknesses of current HRA methods dwells in their limited capability of modelling the mutual influences between performance shaping factors (PSFs). Indeed at least two types of dependencies between PSFs can be defined: (i) dependency between the states of the PSFs; (ii) dependency between the influences (impacts) of the PSFs on the human performance. This paper introduces a method, based on Analytic Network Process (ANP), for the quantification of the latter, where the overall contribution of each PSF (weight) to the human error probability (HEP) is eventually returned. The core of the method is the modelling process, articulated into two steps: firstly, a qualitative network of dependencies between PSFs is identified, then, the importance of each PSF is quantitatively assessed using ANP. The model allows to distinguish two components of the PSF influence: direct influence that is the influence that the considered PSF is able to express by itself, notwithstanding the presence of other PSFs and indirect influence that is the incremental influence of the considered PSF through its influence on other PSFs. A case study in Air Traffic Control is presented where the proposed approach is integrated into the cognitive simulator PROCOS. The results demonstrated a significant modification of the influence of PSFs over the operator performance when dependencies are taken into account, underlining the importance of considering not only the possible correlation between the states of PSFs but also their mutual dependency in affecting human performance in complex systems.

  1. Spectral Line-Shape Model to Replace the Voigt Profile in Spectroscopic Databases

    Science.gov (United States)

    Lisak, Daniel; Ngo, Ngoc Hoa; Tran, Ha; Hartmann, Jean-Michel

    2014-06-01

    The standard description of molecular line shapes in spectral databases and radiative transfer codes is based on the Voigt profile. It is well known that its simplified assumptions of absorber free motion and independence of collisional parameters from absorber velocity lead to systematic errors in analysis of experimental spectra, and retrieval of gas concentration. We demonstrate1,2 that the partially correlated quadratic speed-dependent hardcollision profile3. (pCqSDHCP) is a good candidate to replace the Voigt profile in the next generations of spectroscopic databases. This profile takes into account the following physical effects: the Doppler broadening, the pressure broadening and shifting of the line, the velocity-changing collisions, the speed-dependence of pressure broadening and shifting, and correlations between velocity- and phase/state-changing collisions. The speed-dependence of pressure broadening and shifting is incorporated into the pCqSDNGP in the so-called quadratic approximation. The velocity-changing collisions lead to the Dicke narrowing effect; however in many cases correlations between velocityand phase/state-changing collisions may lead to effective reduction of observed Dicke narrowing. The hard-collision model of velocity-changing collisions is also known as the Nelkin-Ghatak model or Rautian model. Applicability of the pCqSDHCP for different molecular systems was tested on calculated and experimental spectra of such molecules as H2, O2, CO2, H2O in a wide span of pressures. For all considered systems, pCqSDHCP is able to describe molecular spectra at least an order of magnitude better than the Voigt profile with all fitted parameters being linear with pressure. In the most cases pCqSDHCP can reproduce the reference spectra down to 0.2% or better, which fulfills the requirements of the most demanding remote-sensing applications. An important advantage of pCqSDHCP is that a fast algorithm for its computation was developedab4,5 and allows

  2. Ventral-stream-like shape representation : from pixel intensity values to trainable object-selective COSFIRE models

    NARCIS (Netherlands)

    Azzopardi, George; Petkov, Nicolai

    2014-01-01

    The remarkable abilities of the primate visual system have inspired the construction of computational models of some visual neurons. We propose a trainable hierarchical object recognition model, which we call S-COSFIRE (S stands for Shape and COSFIRE stands for Combination Of Shifted Filter REsponse

  3. Ventral-stream-like shape representation: from pixel intensity values to trainable object-selective COSFIRE models

    NARCIS (Netherlands)

    Azzopardi, G.; Petkov, N.

    2014-01-01

    The remarkable abilities of the primate visual system have inspired the construction of computational models of some visual neurons. We propose a trainable hierarchical object recognition model, which we call S-COSFIRE (S stands for Shape and COSFIRE stands for Combination Of Shifted FIlter REsponse

  4. A two-dimensional analytical model and experimental validation of garter stitch knitted shape memory alloy actuator architecture

    Science.gov (United States)

    Abel, Julianna; Luntz, Jonathan; Brei, Diann

    2012-08-01

    Active knits are a unique architectural approach to meeting emerging smart structure needs for distributed high strain actuation with simultaneous force generation. This paper presents an analytical state-based model for predicting the actuation response of a shape memory alloy (SMA) garter knit textile. Garter knits generate significant contraction against moderate to large loads when heated, due to the continuous interlocked network of loops of SMA wire. For this knit architecture, the states of operation are defined on the basis of the thermal and mechanical loading of the textile, the resulting phase change of the SMA, and the load path followed to that state. Transitions between these operational states induce either stick or slip frictional forces depending upon the state and path, which affect the actuation response. A load-extension model of the textile is derived for each operational state using elastica theory and Euler-Bernoulli beam bending for the large deformations within a loop of wire based on the stress-strain behavior of the SMA material. This provides kinematic and kinetic relations which scale to form analytical transcendental expressions for the net actuation motion against an external load. This model was validated experimentally for an SMA garter knit textile over a range of applied forces with good correlation for both the load-extension behavior in each state as well as the net motion produced during the actuation cycle (250% recoverable strain and over 50% actuation). The two-dimensional analytical model of the garter stitch active knit provides the ability to predict the kinetic actuation performance, providing the basis for the design and synthesis of large stroke, large force distributed actuators that employ this novel architecture.

  5. Longitudinal modeling of appearance and shape and its potential for clinical use.

    Science.gov (United States)

    Gerig, Guido; Fishbaugh, James; Sadeghi, Neda

    2016-10-01

    Clinical assessment routinely uses terms such as development, growth trajectory, degeneration, disease progression, recovery or prediction. This terminology inherently carries the aspect of dynamic processes, suggesting that single measurements in time and cross-sectional comparison may not sufficiently describe spatiotemporal changes. In view of medical imaging, such tasks encourage subject-specific longitudinal imaging. Whereas follow-up, monitoring and prediction are natural tasks in clinical diagnosis of disease progression and of assessment of therapeutic intervention, translation of methodologies for calculation of temporal profiles from longitudinal data to clinical routine still requires significant research and development efforts. Rapid advances in image acquisition technology with significantly reduced acquisition times and with increase of patient comfort favor repeated imaging over the observation period. In view of serial imaging ranging over multiple years, image acquisition faces the challenging issue of scanner standardization and calibration which is crucial for successful spatiotemporal analysis. Longitudinal 3D data, represented as 4D images, capture time-varying anatomy and function. Such data benefits from dedicated analysis methods and tools that make use of the inherent correlation and causality of repeated acquisitions of the same subject. Availability of such data spawned progress in the development of advanced 4D image analysis methodologies that carry the notion of linear and nonlinear regression, now applied to complex, high-dimensional data such as images, image-derived shapes and structures, or a combination thereof. This paper provides examples of recently developed analysis methodologies for 4D image data, primarily focusing on progress in areas of core expertise of the authors. These include spatiotemporal shape modeling and growth trajectories of white matter fiber tracts demonstrated with examples from ongoing longitudinal

  6. Short Term Evaluation of an Anatomically Shaped Polycarbonate Urethane Total Meniscus Replacement in a Goat Model.

    Directory of Open Access Journals (Sweden)

    A C T Vrancken

    Full Text Available Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU, total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical integrity of the implant and the effect of the implant on synovial membrane and articular cartilage histopathological condition.The right medial meniscus of seven Saanen goats was replaced by the implant. Sham surgery (transection of the MCL, arthrotomy and MCL suturing was performed in six animals. The contralateral knee joints of both groups served as control groups. After three months follow-up the following aspects of implant performance were evaluated: implant position, implant deformation and the histopathological condition of the synovium and cartilage.Implant geometry was well maintained during the three month implantation period. No signs of PCU wear were found and the implant did not induce an inflammatory response in the knee joint. In all animals, implant fixation was compromised due to suture breakage, wear or elongation, likely causing the increase in extrusion observed in the implant group. Both the femoral cartilage and tibial cartilage in direct contact with the implant showed increased damage compared to the sham and sham-control groups.This study demonstrates that the novel, anatomically shaped PCU total meniscal replacement is biocompatible and resistant to three months of physiological loading. Failure of the fixation sutures may have increased implant mobility, which probably induced implant extrusion and potentially stimulated cartilage degeneration. Evidently, redesigning the fixation method is necessary. Future animal studies should evaluate the improved fixation method and compare implant performance to current treatment standards, such as allografts.

  7. Longitudinal modeling of appearance and shape and its potential for clinical use.

    Science.gov (United States)

    Gerig, Guido; Fishbaugh, James; Sadeghi, Neda

    2016-10-01

    Clinical assessment routinely uses terms such as development, growth trajectory, degeneration, disease progression, recovery or prediction. This terminology inherently carries the aspect of dynamic processes, suggesting that single measurements in time and cross-sectional comparison may not sufficiently describe spatiotemporal changes. In view of medical imaging, such tasks encourage subject-specific longitudinal imaging. Whereas follow-up, monitoring and prediction are natural tasks in clinical diagnosis of disease progression and of assessment of therapeutic intervention, translation of methodologies for calculation of temporal profiles from longitudinal data to clinical routine still requires significant research and development efforts. Rapid advances in image acquisition technology with significantly reduced acquisition times and with increase of patient comfort favor repeated imaging over the observation period. In view of serial imaging ranging over multiple years, image acquisition faces the challenging issue of scanner standardization and calibration which is crucial for successful spatiotemporal analysis. Longitudinal 3D data, represented as 4D images, capture time-varying anatomy and function. Such data benefits from dedicated analysis methods and tools that make use of the inherent correlation and causality of repeated acquisitions of the same subject. Availability of such data spawned progress in the development of advanced 4D image analysis methodologies that carry the notion of linear and nonlinear regression, now applied to complex, high-dimensional data such as images, image-derived shapes and structures, or a combination thereof. This paper provides examples of recently developed analysis methodologies for 4D image data, primarily focusing on progress in areas of core expertise of the authors. These include spatiotemporal shape modeling and growth trajectories of white matter fiber tracts demonstrated with examples from ongoing longitudinal

  8. Investigating the probability of detection of typical cavity shapes through modelling and comparison of geophysical techniques

    Science.gov (United States)

    James, P.

    2011-12-01

    With a growing need for housing in the U.K., the government has proposed increased development of brownfield sites. However, old mine workings and natural cavities represent a potential hazard before, during and after construction on such sites, and add further complication to subsurface parameters. Cavities are hence a limitation to certain redevelopment and their detection is an ever important consideration. The current standard technique for cavity detection is a borehole grid, which is intrusive, non-continuous, slow and expensive. A new robust investigation standard in the detection of cavities is sought and geophysical techniques offer an attractive alternative. Geophysical techniques have previously been utilised successfully in the detection of cavities in various geologies, but still has an uncertain reputation in the engineering industry. Engineers are unsure of the techniques and are inclined to rely on well known techniques than utilise new technologies. Bad experiences with geophysics are commonly due to the indiscriminate choice of particular techniques. It is imperative that a geophysical survey is designed with the specific site and target in mind at all times, and the ability and judgement to rule out some, or all, techniques. To this author's knowledge no comparative software exists to aid technique choice. Also, previous modelling software limit the shapes of bodies and hence typical cavity shapes are not represented. Here, we introduce 3D modelling software (Matlab) which computes and compares the response to various cavity targets from a range of techniques (gravity, gravity gradient, magnetic, magnetic gradient and GPR). Typical near surface cavity shapes are modelled including shafts, bellpits, various lining and capping materials, and migrating voids. The probability of cavity detection is assessed in typical subsurface and noise conditions across a range of survey parameters. Techniques can be compared and the limits of detection distance

  9. Modelling profile and shape evolution during hot rolling of steel strip

    Directory of Open Access Journals (Sweden)

    Zambrano, P. C.

    2006-10-01

    Full Text Available Profile and shape control are required to assure the dimensional quality of rolled strip. Occurrence of waves either at the edges or centre of strips is attributed to inconsistency between the entry and exit cross-section profiles of the stock within a given rolling pass. The exit profile of the strip can be computed by considering that the such profile is the complement of that of the roll-gap, which is affected by wear, thermal expansion and distortion of the work rolls A computer model was developed to predict the profile of the roll-gap taking into account the thermal gradient within the work roll and the distortion caused by the acting forces. It was possible to establish a good correlation between the profiles of strips obtained from trials carried out on site, and the predictions of the model. The model allows for the prediction of the onset of shape defects from changes in the profile of rolled strips.

    Se requiere del control del perfil y forma para asegurar la calidad dimensional de la cinta laminada. La presencia de ondulaciones, ya sea en la orilla o al centro de la cinta, se atribuye a la inconsistencia entre el perfil de la sección transversal de la pieza a la entrada y a la salida, en un dado paso. El perfil de salida de la cinta se puede calcular al suponer que dicho perfil es el complemento del entrehierro, que es afectado por desgaste, expansión térmica y distorsión de los rodillos de trabajo. Un modelo matemático se desarrolló para predecir el perfil del entrehierro tomando en cuenta el gradiente térmico en el rodillo de trabajo y la distorsión producida por las fuerzas actuantes. Fue posible encontrar una buena correlación entre los perfiles de cintas obtenidos a partir de pruebas en planta y las predicciones del modelo. El modelo permite predecir el origen de defectos de forma a partir de cambios en el perfil de cintas laminadas.

  10. Shapes of clusters and groups of galaxies: Comparison of model predictions with observations

    OpenAIRE

    Paz, D. J.; Lambas, D. G.; Padilla, N.; Merchan, M.

    2005-01-01

    We study the properties of the 3-dimensional and projected shapes of haloes using high resolution numerical simulations and observational data where the latter comes from the 2PIGG (Eke et al. 2004) and SDSS-DR3GC group catalogues (Merchan & Zandivarez 2005). We investigate the dependence of halo shape on characteristics such as mass and number of members. In the 3-dimensional case, we find a significant correlation between the mass and halo shape; massive systems are more prolate than small ...

  11. Locally Linear Diffeomorphic Metric Embedding (LLDME) for surface-based anatomical shape modeling.

    Science.gov (United States)

    Yang, Xianfeng; Goh, Alvina; Qiu, Anqi

    2011-05-01

    This paper presents the algorithm, Locally Linear Diffeomorphic Metric Embedding (LLDME), for constructing efficient and compact representations of surface-based brain shapes whose variations are characterized using Large Deformation Diffeomorphic Metric Mapping (LDDMM). Our hypothesis is that the shape variations in the infinite-dimensional diffeomorphic metric space can be captured by a low-dimensional space. To do so, traditional Locally Linear Embedding (LLE) that reconstructs a data point from its neighbors in Euclidean space is extended to LLDME that requires interpolating a shape from its neighbors in the infinite-dimensional diffeomorphic metric space. This is made possible through the conservation law of momentum derived from LDDMM. It indicates that initial momentum, a linear transformation of the initial velocity of diffeomorphic flows, at a fixed template shape determines the geodesic connecting the template to a subject's shape in the diffeomorphic metric space and becomes the shape signature of an individual subject. This leads to the compact linear representation of the nonlinear diffeomorphisms in terms of the initial momentum. Since the initial momentum is in a linear space, a shape can be approximated by a linear combination of its neighbors in the diffeomorphic metric space. In addition, we provide efficient computations for the metric distance between two shapes through the first order approximation of the geodesic using the initial momentum as well as for the reconstruction of a shape given its low-dimensional Euclidean coordinates using the geodesic shooting with the initial momentum as the initial condition. Experiments are performed on the hippocampal shapes of 302 normal subjects across the whole life span (18-94years). Compared with Principal Component Analysis and ISOMAP, LLDME provides the most compact and efficient representation of the age-related hippocampal shapes. Even though the hippocampal volumes among young adults are as

  12. Shakedown based model for high-cycle fatigue of shape memory alloys

    Science.gov (United States)

    Gu, Xiaojun; Moumni, Ziad; Zaki, Wael; Zhang, Weihong

    2016-11-01

    The paper presents a high-cycle fatigue criterion for shape memory alloys (SMAs) based on shakedown analysis. The analysis accounts for phase transformation as well as reorientation of martensite variants as possible sources of fatigue damage. In the case of high-cycle fatigue, once the structure has reached an asymptotic state, damage is assumed to become confined at the mesoscopic scale, or the scale of the grain, with no discernable inelasticity at the macroscopic scale. Using a multiscale approach, a high-cycle fatigue criterion analogous to the Dang Van model (Dang Van 1973) for elastoplastic metals is derived for SMAs obeying the Zaki–Moumni model for SMAs (Zaki and Moumni 2007a). For these alloys, a safe domain is established in stress deviator space, consisting of a hypercylinder with axis parallel to the direction of martensite orientation at the mesoscopic scale. Safety with regard to high-cycle fatigue, upon elastic shakedown, is conditioned by the persistence of the macroscopic stress path at every material point within the hypercylinder, whose size depends on the volume fraction of martensite. The proposed criterion computes a fatigue factor at each material point, indicating its degree of safeness with respect to high cycle fatigue.

  13. Elastodynamic shape modeler: a tool for defining the deformation behavior of virtual tissues.

    Science.gov (United States)

    Radetzky, A; Nürnberger, A; Pretschner, D P

    2000-01-01

    A main goal of surgical simulators is the creation of virtual training environments for prospective surgeons. Thus, students can rehearse the various steps of surgical procedures on a computer system without any risk to the patient. One main condition for realistic training is the simulated interaction with virtual medical devices, such as endoscopic instruments. In particular, the virtual deformation and transection of tissues are important. For this application, a neuro-fuzzy model has been developed, which allows the description of the visual and haptic deformation behavior of the simulated tissue by means of expert knowledge in the form of medical terms. Pathologic conditions affecting the visual and haptic tissue response can be easily changed by a medical specialist without mathematical knowledge. By using the personal computer-based program Elastodynamic Shape Modeler, these conditions can be adjusted via a graphical user interface. With a force feedback device, which is similar to a real laparoscopic instrument, virtual deformations can be performed and the resulting haptic feedback can be felt. Thus, use of neuro-fuzzy technologies for the definition and calculation of virtual deformations seems applicable to the simulation of surgical interventions in virtual environments.

  14. Modeling of thermo-mechanical fatigue and damage in shape memory alloy axial actuators

    Science.gov (United States)

    Wheeler, Robert W.; Hartl, Darren J.; Chemisky, Yves; Lagoudas, Dimitris C.

    2015-04-01

    The aerospace, automotive, and energy industries have seen the potential benefits of using shape memory alloys (SMAs) as solid state actuators. Thus far, however, these actuators are generally limited to non-critical components or over-designed due to a lack of understanding regarding how SMAs undergo thermomechanical or actuation fatigue and the inability to accurately predict failure in an actuator during use. The purpose of this study was to characterize the actuation fatigue response of Nickel-Titanium-Hafnium (NiTiHf) axial actuators and, in turn, use this characterization to predict failure and monitor damage in dogbone actuators undergoing various thermomechanical loading paths. Calibration data was collected from constant load, full cycle tests ranging from 200-600MPa. Subsequently, actuator lifetimes were predicted for four additional loading paths. These loading paths consisted of linearly varying load with full transformation (300-500MPa) and step loads which transition from zero stress to 300-400MPa at various martensitic volume fractions. Thermal cycling was achieved via resistive heating and convective cooling and was controlled via a state machine developed in LabVIEW. A previously developed fatigue damage model, which is formulated such that the damage accumulation rate is general in terms of its dependence on current and local stress and actuation strain states, was utilized. This form allows the model to be utilized for specimens undergoing complex loading paths. Agreement between experiments and simulations is discussed.

  15. Scanning electron microscope measurement of width and shape of 10 nm patterned lines using a JMONSEL-modeled library

    Energy Technology Data Exchange (ETDEWEB)

    Villarrubia, J.S., E-mail: john.villarrubia@nist.gov [Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Vladár, A.E.; Ming, B. [Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Kline, R.J.; Sunday, D.F. [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Chawla, J.S.; List, S. [Intel Corporation, RA3-252, 5200 NE Elam Young Pkwy, Hillsboro, OR 97124 (United States)

    2015-07-15

    The width and shape of 10 nm to 12 nm wide lithographically patterned SiO{sub 2} lines were measured in the scanning electron microscope by fitting the measured intensity vs. position to a physics-based model in which the lines' widths and shapes are parameters. The approximately 32 nm pitch sample was patterned at Intel using a state-of-the-art pitch quartering process. Their narrow widths and asymmetrical shapes are representative of near-future generation transistor gates. These pose a challenge: the narrowness because electrons landing near one edge may scatter out of the other, so that the intensity profile at each edge becomes width-dependent, and the asymmetry because the shape requires more parameters to describe and measure. Modeling was performed by JMONSEL (Java Monte Carlo Simulation of Secondary Electrons), which produces a predicted yield vs. position for a given sample shape and composition. The simulator produces a library of predicted profiles for varying sample geometry. Shape parameter values are adjusted until interpolation of the library with those values best matches the measured image. Profiles thereby determined agreed with those determined by transmission electron microscopy and critical dimension small-angle x-ray scattering to better than 1 nm.

  16. Scanning electron microscope measurement of width and shape of 10 nm patterned lines using a JMONSEL-modeled library

    International Nuclear Information System (INIS)

    The width and shape of 10 nm to 12 nm wide lithographically patterned SiO2 lines were measured in the scanning electron microscope by fitting the measured intensity vs. position to a physics-based model in which the lines' widths and shapes are parameters. The approximately 32 nm pitch sample was patterned at Intel using a state-of-the-art pitch quartering process. Their narrow widths and asymmetrical shapes are representative of near-future generation transistor gates. These pose a challenge: the narrowness because electrons landing near one edge may scatter out of the other, so that the intensity profile at each edge becomes width-dependent, and the asymmetry because the shape requires more parameters to describe and measure. Modeling was performed by JMONSEL (Java Monte Carlo Simulation of Secondary Electrons), which produces a predicted yield vs. position for a given sample shape and composition. The simulator produces a library of predicted profiles for varying sample geometry. Shape parameter values are adjusted until interpolation of the library with those values best matches the measured image. Profiles thereby determined agreed with those determined by transmission electron microscopy and critical dimension small-angle x-ray scattering to better than 1 nm

  17. A spherical harmonics intensity model for 3D segmentation and 3D shape analysis of heterochromatin foci.

    Science.gov (United States)

    Eck, Simon; Wörz, Stefan; Müller-Ott, Katharina; Hahn, Matthias; Biesdorf, Andreas; Schotta, Gunnar; Rippe, Karsten; Rohr, Karl

    2016-08-01

    The genome is partitioned into regions of euchromatin and heterochromatin. The organization of heterochromatin is important for the regulation of cellular processes such as chromosome segregation and gene silencing, and their misregulation is linked to cancer and other diseases. We present a model-based approach for automatic 3D segmentation and 3D shape analysis of heterochromatin foci from 3D confocal light microscopy images. Our approach employs a novel 3D intensity model based on spherical harmonics, which analytically describes the shape and intensities of the foci. The model parameters are determined by fitting the model to the image intensities using least-squares minimization. To characterize the 3D shape of the foci, we exploit the computed spherical harmonics coefficients and determine a shape descriptor. We applied our approach to 3D synthetic image data as well as real 3D static and real 3D time-lapse microscopy images, and compared the performance with that of previous approaches. It turned out that our approach yields accurate 3D segmentation results and performs better than previous approaches. We also show that our approach can be used for quantifying 3D shape differences of heterochromatin foci. PMID:27037463

  18. Use of a Ni60Ti shape memory alloy for active jet engine chevron application: I. Thermomechanical characterization

    International Nuclear Information System (INIS)

    A shape memory alloy (SMA) with a composition of Ni60Ti40 (wt%) was chosen for the fabrication of active beam elements intended for use as cyclic actuators and incorporated into a morphing aerospace structure. The active structure is a variable-geometry chevron (VGC) designed to reduce jet engine noise in the take-off flight regime while maintaining efficiency in the cruise regime. This two-part work addresses the training, characterization and derived material properties of the new nickel-rich composition, the assessment of the actuation properties of the active beam actuator and the accurate analysis of the VGC and its subcomponents using a model calibrated from the material characterization. The characterization performed in part I of this work was intended to provide quantitative information used to predict the response of SMA beam actuators of the same composition and with the same heat treatment history. Material in the form of plates was received and ASTM standard tensile testing coupons were fabricated and tested. To fully characterize the material response as an actuator, various thermomechanical experiments were performed. Properties such as actuation strain and transformation temperatures as a function of applied stress were of primary interest. Results from differential scanning calorimetry, monotonic tensile loading and constant stress thermal loading for the as-received, untrained material are first presented. These show lower transformation temperatures, higher elastic stiffnesses (60–90 GPa) and lower recoverable transformation strains (≈1.5%) when compared to equiatomic NiTi (Nitinol). Stabilization (training) cycles were applied to the tensile specimens and characterization tests were repeated for the stable (trained) material. The effects of specimen training included the saturation of cyclically generated irrecoverable plastic strains and a broadening of the thermal transformation hysteresis. A set of final derived material properties for

  19. Dependence of the single-scattering properties of small ice crystals on idealized shape models

    Directory of Open Access Journals (Sweden)

    J. Um

    2010-11-01

    Full Text Available Small ice crystals (with maximum dimension <50 μm appear quasi-circular when imaged by probes on aircraft flying through cloud. Therefore, idealized models constructed to calculate their single-scattering properties have included quasi-spherical models such as Chebyshev particles, Gaussian random spheres, and droxtals. Recently, an ice analogue grown from sodium fluorosilicate solution on a glass substrate, with several columns emanating from a common center of mass, was shown to be quasi-circular when imaged by state-of-the-art cloud probes. In this study, a new idealized model, called the budding Bucky ball (3B that resembles the shape of the small ice analogue is developed. The corresponding single-scattering properties (scattering phase function P11 and asymmetry parameter g are computed by a ray-tracing code. Compared with previosly used models, 3B scatters less light in the forward and more light in the lateral and backward directions. The Chebyshev particles and Gaussian random spheres show smooth and featureless P11, whereas droxtals and 3Bs, which have a faceted structure, show several peaks in P11 associated with angles of minimum deviation. Overall, the difference in the forward (lateral; backward scattering between models are up to 22% (994%; 132%, 20% (510%; 101%, and 16% (146%; 156% for small ice crystals with repective area ratios of 0.85, 0.77, and 0.69. The g for different models varies by up to 25%, 23%, and 19% for particles with area ratios of 0.85, 0.77, and 0.69, respectively. Becuase the single-scattering properties of small ice crystals depend both on the choice of the idealized model and the area ratios used to characterize the small ice crystals, higher resolution observations of small ice crystals or direct observations of their single-scattering properties are required.

  20. Pulmonary lobe segmentation based on ridge surface sampling and shape model fitting

    Energy Technology Data Exchange (ETDEWEB)

    Ross, James C., E-mail: jross@bwh.harvard.edu [Channing Laboratory, Brigham and Women' s Hospital, Boston, Massachusetts 02215 (United States); Surgical Planning Lab, Brigham and Women' s Hospital, Boston, Massachusetts 02215 (United States); Laboratory of Mathematics in Imaging, Brigham and Women' s Hospital, Boston, Massachusetts 02126 (United States); Kindlmann, Gordon L. [Computer Science Department and Computation Institute, University of Chicago, Chicago, Illinois 60637 (United States); Okajima, Yuka; Hatabu, Hiroto [Department of Radiology, Brigham and Women' s Hospital, Boston, Massachusetts 02215 (United States); Díaz, Alejandro A. [Pulmonary and Critical Care Division, Brigham and Women' s Hospital and Harvard Medical School, Boston, Massachusetts 02215 and Department of Pulmonary Diseases, Pontificia Universidad Católica de Chile, Santiago (Chile); Silverman, Edwin K. [Channing Laboratory, Brigham and Women' s Hospital, Boston, Massachusetts 02215 and Pulmonary and Critical Care Division, Brigham and Women' s Hospital and Harvard Medical School, Boston, Massachusetts 02215 (United States); Washko, George R. [Pulmonary and Critical Care Division, Brigham and Women' s Hospital and Harvard Medical School, Boston, Massachusetts 02215 (United States); Dy, Jennifer [ECE Department, Northeastern University, Boston, Massachusetts 02115 (United States); Estépar, Raúl San José [Department of Radiology, Brigham and Women' s Hospital, Boston, Massachusetts 02215 (United States); Surgical Planning Lab, Brigham and Women' s Hospital, Boston, Massachusetts 02215 (United States); Laboratory of Mathematics in Imaging, Brigham and Women' s Hospital, Boston, Massachusetts 02126 (United States)

    2013-12-15

    Purpose: Performing lobe-based quantitative analysis of the lung in computed tomography (CT) scans can assist in efforts to better characterize complex diseases such as chronic obstructive pulmonary disease (COPD). While airways and vessels can help to indicate the location of lobe boundaries, segmentations of these structures are not always available, so methods to define the lobes in the absence of these structures are desirable. Methods: The authors present a fully automatic lung lobe segmentation algorithm that is effective in volumetric inspiratory and expiratory computed tomography (CT) datasets. The authors rely on ridge surface image features indicating fissure locations and a novel approach to modeling shape variation in the surfaces defining the lobe boundaries. The authors employ a particle system that efficiently samples ridge surfaces in the image domain and provides a set of candidate fissure locations based on the Hessian matrix. Following this, lobe boundary shape models generated from principal component analysis (PCA) are fit to the particles data to discriminate between fissure and nonfissure candidates. The resulting set of particle points are used to fit thin plate spline (TPS) interpolating surfaces to form the final boundaries between the lung lobes. Results: The authors tested algorithm performance on 50 inspiratory and 50 expiratory CT scans taken from the COPDGene study. Results indicate that the authors' algorithm performs comparably to pulmonologist-generated lung lobe segmentations and can produce good results in cases with accessory fissures, incomplete fissures, advanced emphysema, and low dose acquisition protocols. Dice scores indicate that only 29 out of 500 (5.85%) lobes showed Dice scores lower than 0.9. Two different approaches for evaluating lobe boundary surface discrepancies were applied and indicate that algorithm boundary identification is most accurate in the vicinity of fissures detectable on CT. Conclusions: The

  1. Seamless tube shape is constrained by endocytosis-dependent regulation of active Moesin

    OpenAIRE

    Schottenfeld-Roames, Jodi; Rosa, Jeffrey B.; Ghabrial, Amin S.

    2014-01-01

    Most tubes have “seams” – intercellular or autocellular junctions that seal membranes together into a tube – but “seamless” tubes also exist [1-3]. In Drosophila, stellate-shaped tracheal terminal cells make seamless tubes, with single branches running through each of dozens of cellular extensions. We find that mutations in braided impair terminal cell branching and cause formation of seamless tube cysts. We show that braided encodes Syntaxin7, and that cysts also form in cells deficient for ...

  2. Variational formulation and stability analysis of a three dimensional superelastic model for shape memory alloys

    Science.gov (United States)

    Alessi, Roberto; Pham, Kim

    2016-02-01

    This paper presents a variational framework for the three-dimensional macroscopic modelling of superelastic shape memory alloys in an isothermal setting. Phase transformation is accounted through a unique second order tensorial internal variable, acting as the transformation strain. Postulating the total strain energy density as the sum of a free energy and a dissipated energy, the model depends on two material scalar functions of the norm of the transformation strain and a material scalar constant. Appropriate calibration of these material functions allows to render a wide range of constitutive behaviours including stress-softening and stress-hardening. The quasi-static evolution problem of a domain is formulated in terms of two physical principles based on the total energy of the system: a stability criterion, which selects the local minima of the total energy, and an energy balance condition, which ensures the consistency of the evolution of the total energy with respect to the external loadings. The local phase transformation laws in terms of Kuhn-Tucker relations are deduced from the first-order stability condition and the energy balance condition. The response of the model is illustrated with a numerical traction-torsion test performed on a thin-walled cylinder. Evolutions of homogeneous states are given for proportional and non-proportional loadings. Influence of the stress-hardening/softening properties on the evolution of the transformation domain is emphasized. Finally, in view of an identification process, the issue of stability of homogeneous states in a multi-dimensional setting is answered based on the study of second-order derivative of the total energy. Explicit necessary and sufficient conditions of stability are provided.

  3. Modeling of active beam units with Modelica

    DEFF Research Database (Denmark)

    Maccarini, Alessandro; Hultmark, Göran; Vorre, Anders;

    2015-01-01

    This paper proposes an active beam model suitable for building energy simulations with the programming language Modelica. The model encapsulates empirical equations derived by a novel active beam terminal unit that operates with low-temperature heating and high-temperature cooling systems....... Measurements from a full-scale experiment are used to compare the thermal behavior of the active beam with the one predicted by simulations. The simulation results show that the model corresponds closely with the actual operation. The model predicts the outlet water temperature of the active beam...... with a maximum mean absolute error of 0.18 °C. In term of maximum mean absolute percentage error, simulation results differ by 0.9%. The methodology presented is general enough to be applied for modeling other active beam units. Modeling of active beam units with Modelica. Available from: https...

  4. Uncertainty analysis of a one-dimensional constitutive model for shape memory alloy thermomechanical description

    DEFF Research Database (Denmark)

    Oliveira, Sergio A.; Savi, Marcelo A.; Santos, Ilmar F.

    2014-01-01

    The use of shape memory alloys (SMAs) in engineering applications has increased the interest of the accuracy analysis of their thermomechanical description. This work presents an uncertainty analysis related to experimental tensile tests conducted with shape memory alloy wires. Experimental data ...

  5. Shape dynamics of growing cell walls

    CERN Document Server

    Banerjee, Shiladitya; Dinner, Aaron R

    2015-01-01

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell-wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to d...

  6. MODELING OF RUNNING CUTTERS FOR SHAPING OF IMPROVED NONINVOLUTE TOOTH GEARS

    Directory of Open Access Journals (Sweden)

    Tatyana TRETYAK

    2012-05-01

    Full Text Available The questions of tooling design for production of advanced gears are considered. Engineering is based on the special applied development of the mathematical theory of multiparametric mappings of space. In fulfilled engineering of gear cutting tools for shaping of noninvolute gears it is provided for exclusion of distorted profiling after tool regrinds. There are proposed calculation algorithms, which may be used in dataware of respective CAD/CAM systems of maintenance for tooling backup. Among developed tools there are assembled shaping cutters with prismatic and round cutters. Compensatory possibilities of proposed assembled shaping cutters are ensured by repositioning of shaped cutting edges after their regrindings: by linear displacement of prismatic shaped cutters and angular displacement of round ones respectively.

  7. A case of impaired shape integration: Implications for models of visual object processing

    DEFF Research Database (Denmark)

    Gerlach, Christian; Marstrand, Lisbeth; Habekost, Thomas;

    2005-01-01

    We describe a patient, HE, who was left with a remarkably selective deficit in intermediate vision following an infarct in the right occipito-temporal region. Thus, HE was able to group elements by colour and proximity but impaired in grouping based on similarity in shape. This finding supports...... the notion that grouping may be divided into two general steps: (i) element clustering and (ii) shape configuration, with the latter operation being impaired in HE. As opposed to previous cases with shape integration deficits, HE was able to name objects accurately. Initially, this might suggest that shape...... integration is not a prerequisite for normal object naming. However, on more demanding tests of visual object recognition, HE's performance deteriorated, with her performance being inversely related to the demand placed on integration of local elements into more elaborate shape descriptions. From this we...

  8. Determination of reactive oxygen species from ZnO micro-nano structures with shape-dependent photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    He, Weiwei; Zhao, Hongxiao; Jia, Huimin [Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, Xuchang University, Henan 461000 (China); Yin, Jun-Jie [Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740 (United States); Zheng, Zhi, E-mail: zhengzhi99999@gmail.com [Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, Xuchang University, Henan 461000 (China)

    2014-05-01

    Graphical abstract: ZnO micro/nano structures with shape dependent photocatalytic activity were prepared by hydrothermal reaction. The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were identified precisely by electron spin resonance spectroscopy. The type of reactive oxygen species was determined by band gap structure of ZnO. - Highlights: • ZnO micro/nano structures with different morphologies were prepared by solvothermal reaction. • Multi-pod like ZnO structures exhibited superior photocatalytic activity. • The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were characterized precisely by electron spin resonance spectroscopy. • The type of reactive oxygen species was determined by band gap structure of ZnO. - Abstract: ZnO micro/nano structures with different morphologies have been prepared by the changing solvents used during their synthesis by solvothermal reaction. Three typical shapes of ZnO structures including hexagonal, bell bottom like and multi-pod formed and were characterized by scanning electron microscopy and X-ray diffraction. Multi pod like ZnO structures exhibited the highest photocatalytic activity toward degradation of methyl orange. Using electron spin resonance spectroscopy coupled with spin trapping techniques, we demonstrate an effective way to identify precisely the generation of hydroxyl radicals, superoxide and singlet oxygen from the irradiated ZnO multi pod structures. The type of reactive oxygen species formed was predictable from the band gap structure of ZnO. These results indicate that the shape of micro-nano structures significantly affects the photocatalytic activity of ZnO, and demonstrate the value of electron spin resonance spectroscopy for characterizing the type of reactive oxygen species formed during photoexcitation of semiconductors.

  9. Modeling of a honeycomb-shaped pyroelectric energy harvester for human body heat harvesting

    Science.gov (United States)

    Kim, Myoung-Soo; Jo, Sung-Eun; Ahn, Hye-Rin; Kim, Yong-Jun

    2015-06-01

    Pyroelectric conversion can be used for thermal energy harvesting in lieu of thermoelectric conversion. In the case of human body energy harvesting, the general pyroelectric energy harvester (PEH) cannot be applied because the weak body heat can hardly penetrate the protecting layer to reach the pyroelectric material. This paper presents the realization of a honeycomb-shaped PEH (H-PEH) and a modeling method of the electrode and hole areas. The fabricated H-PEH successfully generated electrical energy using human body heat. The H-PEH with a 1:1.5 electrode-and-hole area ratio showed the best performance. To verify the human energy harvesting, we evaluated the characteristics of conventional PEH and H-PEH when body heat was used as a heat source. The maximum power of the H-PEH was 0.06 and 0.16 μW at wind velocities of 2 and 4 m s-1, respectively. These output power values of the H-PEH were 200 and 224% larger than those of the PEH, respectively, according to the wind velocity.

  10. Thermal shape fluctuation model study of the giant dipole resonance in $^{152}$Gd

    CERN Document Server

    Kumar, A K Rhine

    2015-01-01

    We have studied the giant dipole resonance (GDR) in the hot and rotating nucleus $^{152}$Gd within the framework of thermal shape fluctuation model (TSFM) built on the microscopic-macroscopic calculations of the free energies with a macroscopic approach for the GDR. Our results for GDR cross sections are in good agreement with the experimental values except for a component peaking around 17 MeV where the data has large uncertainties. Such a component is beyond our description which properly takes care of the splitting of GDR components due to the deformation and Coriolis effects. Around this 17 MeV lies the half maximum in experimental cross sections, and hence the extracted GDR widths and deformations (estimated from these widths) turn out to be overestimated and less reliable. Reproducing these widths with empirical formulae could conceal the information contained in the cross sections. Fully microscopic GDR calculations and a more careful look at the data could be useful to understand the GDR component aro...

  11. Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

    Directory of Open Access Journals (Sweden)

    Sun Chunya

    2015-11-01

    Full Text Available Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB, is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO, is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

  12. Local phase tensor features for 3-D ultrasound to statistical shape+pose spine model registration.

    Science.gov (United States)

    Hacihaliloglu, Ilker; Rasoulian, Abtin; Rohling, Robert N; Abolmaesumi, Purang

    2014-11-01

    Most conventional spine interventions are performed under X-ray fluoroscopy guidance. In recent years, there has been a growing interest to develop nonionizing imaging alternatives to guide these procedures. Ultrasound guidance has emerged as a leading alternative. However, a challenging problem is automatic identification of the spinal anatomy in ultrasound data. In this paper, we propose a local phase-based bone feature enhancement technique that can robustly identify the spine surface in ultrasound images. The local phase information is obtained using a gradient energy tensor filter. This information is used to construct local phase tensors in ultrasound images, which highlight the spine surface. We show that our proposed approach results in a more distinct enhancement of the bone surfaces compared to recently proposed techniques based on monogenic scale-space filters and logarithmic Gabor filters. We also demonstrate that registration accuracy of a statistical shape+pose model of the spine to 3-D ultrasound images can be significantly improved, using the proposed method, compared to those obtained using monogenic scale-space filters and logarithmic Gabor filters.

  13. Refined rotational period, pole solution, and shape model for (3200) Phaethon

    Energy Technology Data Exchange (ETDEWEB)

    Ansdell, Megan; Meech, Karen J.; Kaluna, Heather [NASA Astrobiology Institute, Honolulu, HI 96822 (United States); Hainaut, Olivier [European Southern Observatory, Karl Schwarzschild Straße, 85748 Garching bei München (Germany); Buie, Marc W. [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Bauer, James [Jet Propulsion Laboratory, 4800 Oak Grove Drive, MS 183-401, Pasadena, CA 91109 (United States); Dundon, Luke, E-mail: mansdell@ifa.hawaii.edu [United States Navy, Washington, DC 20350 (United States)

    2014-09-20

    (3200) Phaethon exhibits both comet- and asteroid-like properties, suggesting it could be a rare transitional object such as a dormant comet or previously volatile-rich asteroid. This justifies detailed study of (3200) Phaethon's physical properties as a better understanding of asteroid-comet transition objects can provide insight into minor body evolution. We therefore acquired time series photometry of (3200) Phaethon over 15 nights from 1994 to 2013, primarily using the Tektronix 2048 × 2048 pixel CCD on the University of Hawaii 2.2 m telescope. We utilized light curve inversion to (1) refine (3200) Phaethon's rotational period to P = 3.6032 ± 0.0008 hr; (2) estimate a rotational pole orientation of λ = +85° ± 13° and β = –20° ± 10°; and (3) derive a shape model. We also used our extensive light curve data set to estimate the slope parameter of (3200) Phaethon's phase curve as G ∼ 0.06, consistent with C-type asteroids. We discuss how this highly oblique pole orientation with a negative ecliptic latitude supports previous evidence for (3200) Phaethon's origin in the inner main asteroid belt as well as the potential for deeply buried volatiles fueling impulsive yet rare cometary outbursts.

  14. Refined rotational period, pole solution, and shape model for (3200) Phaethon

    International Nuclear Information System (INIS)

    (3200) Phaethon exhibits both comet- and asteroid-like properties, suggesting it could be a rare transitional object such as a dormant comet or previously volatile-rich asteroid. This justifies detailed study of (3200) Phaethon's physical properties as a better understanding of asteroid-comet transition objects can provide insight into minor body evolution. We therefore acquired time series photometry of (3200) Phaethon over 15 nights from 1994 to 2013, primarily using the Tektronix 2048 × 2048 pixel CCD on the University of Hawaii 2.2 m telescope. We utilized light curve inversion to (1) refine (3200) Phaethon's rotational period to P = 3.6032 ± 0.0008 hr; (2) estimate a rotational pole orientation of λ = +85° ± 13° and β = –20° ± 10°; and (3) derive a shape model. We also used our extensive light curve data set to estimate the slope parameter of (3200) Phaethon's phase curve as G ∼ 0.06, consistent with C-type asteroids. We discuss how this highly oblique pole orientation with a negative ecliptic latitude supports previous evidence for (3200) Phaethon's origin in the inner main asteroid belt as well as the potential for deeply buried volatiles fueling impulsive yet rare cometary outbursts.

  15. CT segmentation of dental shapes by anatomy-driven reformation imaging and B-spline modelling.

    Science.gov (United States)

    Barone, S; Paoli, A; Razionale, A V

    2016-06-01

    Dedicated imaging methods are among the most important tools of modern computer-aided medical applications. In the last few years, cone beam computed tomography (CBCT) has gained popularity in digital dentistry for 3D imaging of jawbones and teeth. However, the anatomy of a maxillofacial region complicates the assessment of tooth geometry and anatomical location when using standard orthogonal views of the CT data set. In particular, a tooth is defined by a sub-region, which cannot be easily separated from surrounding tissues by only considering pixel grey-intensity values. For this reason, an image enhancement is usually necessary in order to properly segment tooth geometries. In this paper, an anatomy-driven methodology to reconstruct individual 3D tooth anatomies by processing CBCT data is presented. The main concept is to generate a small set of multi-planar reformation images along significant views for each target tooth, driven by the individual anatomical geometry of a specific patient. The reformation images greatly enhance the clearness of the target tooth contours. A set of meaningful 2D tooth contours is extracted and used to automatically model the overall 3D tooth shape through a B-spline representation. The effectiveness of the methodology has been verified by comparing some anatomy-driven reconstructions of anterior and premolar teeth with those obtained by using standard tooth segmentation tools. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Shaping old age: Innovation partnerships, senior centres and billiards tables as active ageing technologies

    DEFF Research Database (Denmark)

    Lassen, Aske Juul

    2015-01-01

    During the past decade active ageing has been positioned as a solution to the problem of global ageing. While the scientific, economic and even moral arguments for pursuing a more active old age has been many, the integration of active ageing in everyday practices face challenges. This chapter...... explores the ways that active ageing policies become part of everyday practices, by proposing the concept of active ageing technologies. Active ageing technologies are material and immaterial condensations of knowledge that form old age in specific ways. Through the cases of an innovation partnership, two...... this constellation to explore how technologies bridge policy and practice, and concludes that active ageing is transformed in everyday practices, and that the good old age is formed through a negotiation between ambiguous and contrasting practices and ideologies....

  17. Modeling Students' Units Coordinating Activity

    OpenAIRE

    Boyce, Steven James

    2014-01-01

    Primarily via constructivist teaching experiment methodology, units coordination (Steffe, 1992) has emerged as a useful construct for modeling students' psychological constructions pertaining to several mathematical domains, including counting sequences, whole number multiplicative conceptions, and fractions schemes. I describe how consideration of units coordination as a Piagetian (1970b) structure is useful for modeling units coordination across contexts. In this study, I extend teaching ...

  18. Shape Memory Alloy Modeling and Applications to Porous and Composite Structures

    Science.gov (United States)

    Zhu, Pingping

    There has been a growing concern about an exciting class of advanced material -- shape memory alloys (SMAs) since their discovery several decades ago. SMAs exhibit large reversible stresses and strains owing to a thermoelastic phase transformation. They have been widely used in many engineering fields including aerospace, biomedical, and automotive engineering, especially as sensors, actuators, bone implants and deployable switches. The behavior of SMAs is very complex due to the coupling between thermal and mechanical effects. Theoretical and computational tools are used in this dissertation to investigate the mechanical behavior of SMA and its related structures for seeking better and wider application of this material. In the first part of this dissertation, we proposed an improved macroscopic phenomenological constitutive model of SMA that accounts for all major mechanical behaviors including elasticity, phase transformation, reorientation and plasticity. The model is based on some previous work developed in the Brinson group, and the current efforts are focused on plasticity, the application of a pre-defined strain, unification of notations, and other coding-related work. A user subroutine script VUMAT is developed to implement the constitutive model to the commercial finite element software Abaqus. Typical simulation results based on the model are presented, as well as verification with some experimental results. In the second part, we apply the developed constitutive model to a series of two-dimensional SMA plates with structured arrays of pores to investigate the structural response, especially the stress, strain, phase transformation, and plastic fields. Results are documented about the coupling of the elastic, transformation and plastic fields about the arrays of pores. Theoretical and experimental DIC results are also utilized to validate some simulation results. Conclusions are then drawn to provide understanding in the effect of pores and the

  19. Modeling Workflow Using UML Activity Diagram

    Institute of Scientific and Technical Information of China (English)

    Wei Yinxing(韦银星); Zhang Shensheng

    2004-01-01

    An enterprise can improve its adaptability in the changing market by means of workflow technologies. In the build time, the main function of Workflow Management System (WFMS) is to model business process. Workflow model is an abstract representation of the real-world business process. The Unified Modeling Language (UML) activity diagram is an important visual process modeling language proposed by the Object Management Group (OMG). The novelty of this paper is representing workflow model by means of UML activity diagram. A translation from UML activity diagram to π-calculus is established. Using π-calculus, the deadlock property of workflow is analyzed.

  20. Gleason grading of prostate histology utilizing manifold regularization via statistical shape model of manifolds

    Science.gov (United States)

    Sparks, Rachel; Madabhushi, Anant

    2012-03-01

    Gleason patterns of prostate cancer histopathology, characterized primarily by morphological and architectural attributes of histological structures (glands and nuclei), have been found to be highly correlated with disease aggressiveness and patient outcome. Gleason patterns 4 and 5 are highly correlated with more aggressive disease and poorer patient outcome, while Gleason patterns 1-3 tend to reflect more favorable patient outcome. Because Gleason grading is done manually by a pathologist visually examining glass (or digital) slides, subtle morphologic and architectural differences of histological attributes may result in grading errors and hence cause high inter-observer variability. Recently some researchers have proposed computerized decision support systems to automatically grade Gleason patterns by using features pertaining to nuclear architecture, gland morphology, as well as tissue texture. Automated characterization of gland morphology has been shown to distinguish between intermediate Gleason patterns 3 and 4 with high accuracy. Manifold learning (ML) schemes attempt to generate a low dimensional manifold representation of a higher dimensional feature space while simultaneously preserving nonlinear relationships between object instances. Classification can then be performed in the low dimensional space with high accuracy. However ML is sensitive to the samples contained in the dataset; changes in the dataset may alter the manifold structure. In this paper we present a manifold regularization technique to constrain the low dimensional manifold to a specific range of possible manifold shapes, the range being determined via a statistical shape model of manifolds (SSMM). In this work we demonstrate applications of the SSMM in (1) identifying samples on the manifold which contain noise, defined as those samples which deviate from the SSMM, and (2) accurate out-of-sample extrapolation (OSE) of newly acquired samples onto a manifold constrained by the SSMM. We