Reference Domain Research Articles

From reference ontologies to ontology patterns and back

Building proper reference ontologies is a hard task. There are a number of methods and tools that traditionally have been used to support this task. These include the use of foundational theories, the reuse of domain and core ontologies, the adoption of development methods, as well as the support of proper software tools. In this context, an approach that has gained increasing attention in recent years is the systematic application of ontology patterns. However, a pattern-based approach to ontology engineering requires: the existence of a set of suitable patterns that can be reused in the construction of new ontologies; a proper methodological support for eliciting these patterns, as well as for applying them in the construction of these new models. The goal of this paper is twofold: (i) firstly, we present an approach for deriving conceptual ontology patterns from ontologies. These patterns are derived from ontologies of different generality levels, ranging from foundational to domain ontologies; (ii) secondly, we present guidelines that describe how these patterns can be applied in combination for building reference domain ontologies in a reuse-oriented process. In summary, this paper is about the construction of ontology patterns from ontologies, as well as the construction of ontologies from ontology patterns.

A Numerical Investigation on the Natural Frequencies of FGM Sandwich Shells with Variable Thickness by the Local Generalized Differential Quadrature Method

The main aim of the present paper is to solve numerically the free vibration problem of sandwich shell structures with variable thickness and made of Functionally Graded Materials (FGMs). Several Higher-order Shear Deformation Theories (HSDTs), defined by a unified formulation, are employed in the study. The FGM structures are characterized by variable mechanical properties due to the through-the-thickness variation of the volume fraction distribution of the two constituents and the arbitrary thickness profile. A four-parameter power law expression is introduced to describe the FGMs, whereas general relations are used to define the thickness variation, which can affect both the principal coordinates of the shell reference domain. A local scheme of the Generalized Differential Quadrature (GDQ) method is employed as numerical tool. The natural frequencies are obtained varying the exponent of the volume fraction distributions using higher-order theories based on a unified formulation. The structural models considered are two-dimensional and require less degrees of freedom when compared to the corresponding three-dimensional finite element (FE) models, which require a huge number of elements to describe the same geometries accurately. A comparison of the present results with the FE solutions is carried out for the isotropic cases only, whereas the numerical results available in the literature are used to prove the validity as well as accuracy of the current approach in dealing with FGM structures characterized by a variable thickness profile.

Homogenization of a fully coupled thermoelasticity problem for a highly heterogeneous medium with a priori known phase transformations

We investigate a linear, fully coupled thermoelasticity problem for a highly heterogeneous, two‐phase medium. The medium in question consists of a connected matrix with disconnected, initially periodically distributed inclusions separated by a sharp interface undergoing an a priori known interface movement because of phase transformations. After transforming the moving geometry to an ϵ‐periodic, fixed reference domain, we establish the well‐posedness of the model and derive a number of ϵ‐independent a priori estimates. Via a two‐scale convergence argument, we then show that the ϵ‐dependent solutions converge to solutions of a corresponding upscaled model with distributed time‐dependent microstructures. Copyright © 2017 John Wiley & Sons, Ltd.

Fréchet Differentiability of Unsteady Incompressible Navier--Stokes Flow with Respect to Domain Variations of Low Regularity by Using a General Analytical Framework

We consider shape optimization problems governed by the unsteady Navier--Stokes equations by applying the method of mappings, where the problem is transformed to a reference domain ${\Omega_{{ref}}}$ and the physical domain is given by $\Omega=\tau({\Omega_{{ref}}})$ with a domain transformation $\tau\in W^{1,\infty}({\Omega_{{ref}}})$. We show the Frechet differentiability of $\tau\mapsto (v,p)(\tau)$ in a neighborhood of $\tau={id}$ under as low regularity requirements on ${\Omega_{{ref}}}$ and $\tau$ as possible. We propose a general analytical framework beyond the implicit function theorem to show the Frechet differentiability of the transformation-to-state mapping conveniently. It can be applied to other shape optimization or optimal control problems and takes care of the usual norm discrepancy needed for nonlinear problems to show differentiability of the state equation and invertibility of the linearized operator. By applying the framework to the unsteady Navier--Stokes equations, we show that for ...

World class manufacturing in make-to-order batch-production SMEs: an exploratory analysis in northern Italy

The applicability of world class manufacturing (WCM) in small and medium enterprises (SMEs) is a hotly debated topic. This paper belongs to this stream of research and presents a statistical survey designed to assess which WCM practices, if any, are implemented by SMEs and their effects on operational performances. Specifically, a comprehensive questionnaire was submitted to a sample of North Italian make-to-order batch-production SMEs, in the furniture, precision mechanics and textile-fashion industries. To assure consistency, and to avoid subjective interpretations, practices included in the questionnaire were adequately contextualised and answers were measured with an innovative five-point Likert-type scale. Outcomes, relative to the reference domain, demonstrate that SMEs can overcome quality-cost-time tradeoffs, using an integrated set of WCM practices. Results also indicate that belonging to a formal business group is a powerful enabler for a successful implementation of WCM, in SMEs.

ROBUST GENERATION OF BIO-INSPIRED ULTRAHYDROPHOBIC METALLIC SURFACES BY NANOSECOND PULSED LASERS

The current availability of lasers with characteristic pulse lengths ranging from nanoseconds to femtoseconds and the development of the appropriate laser processing workstations granting the appropriate precision and repeatability have definitively consolidated laser surface microstructuring as a reference domain nowadays unavoidable for the design and manufacturing of microsystems: micro electro-mechanical systems (MEMSs), fluidic devices, advanced sensors, biomedical devices, etc., are all among the most well-known developments of laser micromanufacturing technology. In this line, the generation of surfaces with specific functional properties is becoming an important niche of applications. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is envisaged, the generation of super-hydrophobic self-cleaning extended functional surfaces being described.

Penerapan Principal Component Analysis untuk Mereduksi Dimensi Data Penerapan Teknologi Informasi dan Komunikasi untuk Pendidikan di Sekolah

This study aimed to analyze the most influential variable in the implementation of ICT in schools. Principal component analysis using linear algebra to reduce the dimension of data with variables that are interconnected into a new set of data with variables that are not related to each other, called the principal component. Principal component is used to save and calculate how much correlation within varian. The ICT data is collected from 50 schools, this data is grouped into five group based on reference domain of ICT for education indicator by UIS 2009. Dataset per group is used as input for principal component analysis algorithm with Matlab R2014a and produce principal component. Principal component analysis produce five variable with the most influence based on their domain, there are mean hour for individual using of ICT in curicculum domain, existence school in internet in infrastructure domain, learner proportion in using computer laboratory for learning in teacher development domain, learner propostion that computer basic skill course in participation domain.

Care of the self and power relations: female nurses taking care of other women.

to analyze the care of self of female nurses and the power relations established by them in the care of other women. integrative review of literature published between 2005 and 2015. There were 25 publications in the sample. qualitative state of the art with reference domain of a liberating perspective, based on humanization, autonomy and empowerment as a risk reduction strategy in the practice of care to women. The findings suggest solidified power relations among female nurses and women, focused on professional domain concentrated on nurse education under the patriarchal and society's normalization discourse. Some studies consider the importance of understanding power in a capillary way, operating on the bodies of individuals. there is little discussion about the care of self of nurses and the effects on their professional practice, indicating gaps in knowledge in this field.

Scalable joint segmentation and registration framework for infant brain images

The first year of life is the most dynamic and perhaps the most critical phase of postnatal brain development. The ability to accurately measure structure changes is critical in early brain development study, which highly relies on the performances of image segmentation and registration techniques. However, either infant image segmentation or registration, if deployed independently, encounters much more challenges than segmentation/registration of adult brains due to dynamic appearance change with rapid brain development. In fact, image segmentation and registration of infant images can assists each other to overcome the above challenges by using the growth trajectories (i.e., temporal correspondences) learned from a large set of training subjects with complete longitudinal data. Specifically, a one-year-old image with ground-truth tissue segmentation can be first set as the reference domain. Then, to register the infant image of a new subject at earlier age, we can estimate its tissue probability maps, i.e., with sparse patch-based multi-atlas label fusion technique, where only the training images at the respective age are considered as atlases since they have similar image appearance. Next, these probability maps can be fused as a good initialization to guide the level set segmentation. Thus, image registration between the new infant image and the reference image is free of difficulty of appearance changes, by establishing correspondences upon the reasonably segmented images. Importantly, the segmentation of new infant image can be further enhanced by propagating the much more reliable label fusion heuristics at the reference domain to the corresponding location of the new infant image via the learned growth trajectories, which brings image segmentation and registration to assist each other. It is worth noting that our joint segmentation and registration framework is also flexible to handle the registration of any two infant images even with significant age gap in the first year of life, by linking their joint segmentation and registration through the reference domain. Thus, our proposed joint segmentation and registration method is scalable to various registration tasks in early brain development studies. Promising segmentation and registration results have been achieved for infant brain MR images aged from 2-week-old to 1-year-old, indicating the applicability of our method in early brain development study.

A posteriori error estimation for the steady Navier–Stokes equations in random domains

We consider finite element error approximations of the steady incompressible Navier–Stokes equations defined on a randomly perturbed domain, the perturbation being small. Introducing a random mapping, these equations are transformed into PDEs on a fixed reference domain with random coefficients. Under suitable assumptions on the random mapping and the input data, in particular the so-called small data assumption, we prove the well-posedness of the problem. We assume then that the mapping depends affinely on L independent random variables and adopt a perturbation approach expanding the solution with respect to a small parameter ε that controls the amount of randomness in the problem. We perform an a posteriori error analysis for the first order approximation error, namely the error between the exact (random) solution and the finite element approximation of the first term in the expansion with respect to ε. Numerical results are given to illustrate the theoretical results and the effectiveness of the error estimators.

An updated-Lagrangian damage mechanics formulation for modeling the creeping flow and fracture of ice sheets

An updated-Lagrangian formulation is developed to model the incompressible Stokes (creeping) flow and fracture of ice sheets using both explicit-integral and implicit-gradient nonlocal damage approaches. The governing equations of incompressible nonlinearly viscous Stokes flow assuming the plane strain approximation are discretized using high-order mixed finite elements over the current reference domain. The discretized nonlinear system is solved using a Picard iteration scheme, and a mesh update method is employed to obtain the updated reference domain at every time step. Fracture (crevasse) initiation and propagation is modeled using a scalar (isotropic) damage variable, and damage control or element removal strategies are implemented to avoid numerical accuracy and convergence issues arising from fully damaged finite elements near the crevasse tip. The formulation is implemented in the open-source finite element software FEniCS, and the relevant numerical algorithms are detailed. Numerical verification and benchmark studies based on manufactured nonlinear Stokes solutions and constant velocity and gravity-driven creep flow experiments are conducted to establish the viability of the formulation. We demonstrate that crevasse propagation rates obtained from nonlinear Stokes and Maxwell viscoelastic models are in good agreement over short time scales (days), so it is reasonable to neglect the elastic effects and employ the Stokes model to simulate iceberg calving. Furthermore, we demonstrate that over long time scales (months) the updated-Lagrangian Stokes formulation is more physically accurate than the total Lagrangian Maxwell viscoelastic formulation because the former accounts for the domain geometry changes. To conclude, the merit of the proposed formulation is two-fold: first, it is computationally more efficient than the Maxwell viscoelastic model; and second, it accounts for finite strain creep deformations accruing over long time scales.

Partition of unity isogeometric analysis of two dimensional elliptic singular perturbation problems

The design basis functions on the reference domain in IGA are diversified and enhanced by extra enrichment functions and various local refinements with the use of partition of unity (PU) function with flat-top. These reconditioned and modified basis functions are pushed forward to the physical domain by the original design mapping for analysis. With this method, the corresponding stiffness matrix has a small bandwidth and local refinement is simple. Moreover, we construct the PU functions in the reference domain and then move them to a physical domain through a geometric mapping to be used for the generation of global basis functions on a physical domain. Therefore, we also have several advantages in calculating stiffness matrices and load vectors. Here we apply this method to various boundary layer problems.

Assessment of a one-way nesting procedure for obstacle resolved large eddy simulation of the ABL

Large Eddy Simulation (LES) of obstacle-resolved flow over extended urban areas is still extremely costly, compared to the common practice of modeling obstacles with a rough wall-function. In the current study we investigate whether a one-way nesting procedure, consisting of a highly-resolved, small-scale LES embedded inside a low-resolution, large-scale LES, can provide a good compromise between spatial extent, accuracy, and computational requirements. The nesting is achieved by blending the fields of the coarse-grained LES in the vicinity of the nested boundaries of the fine-grained LES. Our assessment of the nesting simulation focuses on two points. Firstly, we compare the vertical profiles of mean quantities and, Reynolds stresses, along with turbulence spectra, against those from a reference LES. Secondly, we check the capabilities of the nesting procedure to facilitate regeneration of the inertial-range turbulence structure by the small-scale LES. Good agreement is found between the mean profiles, but the vertical profiles of Reynolds shear stress from the nested simulation possess an overshoot of the peak values, compared to the reference case. Despite the lack of small- and low-energy eddies transferred from the large scale model to the small scale model, the energy spectra of the nested domain and the reference domain have similar contents. We show that the distance required to reconstruct small eddies depends on the parameters used for the blending between the coarse- and the fine-grained fields. These results show a promising potential for reduction of computational costs in wind engineering applications, where high accuracy is required and where the flow can be strongly dependent on large coherent structures.

An adjoint method for a high-order discretization of deforming domain conservation laws for optimization of flow problems

The fully discrete adjoint equations and the corresponding adjoint method are derived for a globally high-order accurate discretization of conservation laws on parametrized, deforming domains. The conservation law on the deforming domain is transformed into one on a fixed reference domain by the introduction of a time-dependent mapping that encapsulates the domain deformation and parametrization, resulting in an Arbitrary Lagrangian–Eulerian form of the governing equations. A high-order discontinuous Galerkin method is used to discretize the transformed equation in space and a high-order diagonally implicit Runge–Kutta scheme is used for the temporal discretization. Quantities of interest that take the form of space–time integrals are discretized in a solver-consistent manner. The corresponding fully discrete adjoint method is used to compute exact gradients of quantities of interest along the manifold of solutions of the fully discrete conservation law. These quantities of interest and their gradients are used in the context of gradient-based PDE-constrained optimization.The adjoint method is used to solve two optimal shape and control problems governed by the isentropic, compressible Navier–Stokes equations. The first optimization problem seeks the energetically optimal trajectory of a 2D airfoil given a required initial and final spatial position. The optimization solver, driven by gradients computed via the adjoint method, reduced the total energy required to complete the specified mission nearly an order of magnitude. The second optimization problem seeks the energetically optimal flapping motion and time-morphed geometry of a 2D airfoil given an equality constraint on the x-directed impulse generated on the airfoil. The optimization solver satisfied the impulse constraint to greater than 8 digits of accuracy and reduced the required energy between a factor of 2 and 10, depending on the value of the impulse constraint, as compared to the nominal configuration.

Free vibration analysis of arbitrarily shaped Functionally Graded Carbon Nanotube-reinforced plates

Abstract By means of Non-Uniform Rational B-Splines (NURBS) curves, it is possible to describe arbitrary shapes with holes and discontinuities. These peculiar shapes can be taken into account to describe the reference domain of several nanoplates, where a nanoplate refers to a flat structure reinforced with Carbon Nanotubes (CNTs). In the present paper, a micromechanical model based on the agglomeration of these nanoparticles is considered. Indeed, when this kind of reinforcing phase is inserted into a polymeric matrix, CNTs tend to increase their density in some regions. Nevertheless, some nanoparticles can be still scattered within the matrix. The proposed model allows to control the agglomeration by means of two parameters. In this way, several parametric studies are presented to show the influence of this agglomeration on the free vibrations. The considered structures are characterized also by a gradual variation of CNTs along the plate thickness. Thus, the term Functionally Graded Carbon Nanotubes (FG-CNTs) is introduced to specify these plates. Some additional parametric studies are also performed to analyze the effect of a mesh distortion, by considering several geometric and mechanical configurations. The validity of the current methodology is proven through a comparative assessment of our results with those available from the literature or obtained with different numerical approaches, such as the Finite Element Method (FEM). The strong form of the equations governing a plate is solved by means of the Generalized Differential Quadrature (GDQ) method.

A moving bounds strategy for the parameterization of geometric design variables in the simultaneous shape optimization of curved shell structures and openings

A moving bounds strategy is proposed to implement simultaneous shape optimization of curved shell structures and openings. Design variables related to the hole shape are constrained in a planar reference domain by the moving bounds whose values are adaptively updated as functions of design variables related to the surface by an arc-length rule. It is shown that this strategy is essential not only to ensure the geometric consistence in the simultaneous design process but also to hold the shape-preserving of the mapped FE mesh from reference domains. Numerical results are presented to validate the proposed method.

The GDQ method for the free vibration analysis of arbitrarily shaped laminated composite shells using a NURBS-based isogeometric approach

A numerical procedure based on the Generalized Differential Quadrature (GDQ) method is presented to solve the strong form of the differential equations that govern the free vibration problem of some structural elements. The dynamic behavior of several laminated composite doubly-curved shells with arbitrary shape is investigated comparing the results achieved through different Higher-order Shear Deformation Theories (HSDTs) based on an Equivalent Single Layer (ESL) approach. The theoretical framework of the well-known Carrera Unified Formulation (CUF) represents the starting point to develop easily different higher-order models.Starting from regular domains described in principal curvilinear coordinates, a completely arbitrary shape is obtained by means of Non-Uniform Rational B-Splines (NURBS) due to the advantages shown in the well-known isogeometric analysis (IGA). The mapping technique based on the use of blending functions is illustrated to twist the original domain into the distorted one without subdividing the reference domain into sub-elements or finite element (FE). The procedure is extremely general and allows to deal with different boundary condition combinations and stacking sequences. Its validity is proven by the comparison with the results available in the literature concerning arbitrarily shaped plates or obtained through three-dimensional FE models.

A provably stable discontinuous Galerkin spectral element approximation for moving hexahedral meshes

We design a novel provably stable discontinuous Galerkin spectral element (DGSEM) approximation to solve systems of conservation laws on moving domains. To incorporate the motion of the domain, we use an arbitrary Lagrangian-Eulerian formulation to map the governing equations to a fixed reference domain. The approximation is made stable by a discretization of a skew-symmetric formulation of the problem. We prove that the discrete approximation is stable, conservative and, for constant coefficient problems, maintains the free-stream preservation property. We also provide details on how to add the new skew-symmetric ALE approximation to an existing discontinuous Galerkin spectral element code. Lastly, we provide numerical support of the theoretical results.

ELSE: an ontology-based system integrating semantic search and e-learning technologies

ABSTRACTELSE (E-Learning for the Semantic ECM) is an ontology-based system which integrates semantic search methodologies and e-learning technologies. It has been developed within a project of the CME (Continuing Medical Education) program – ECM (Educazione Continua nella Medicina) for Italian participants. ELSE allows the creation of e-learning courses which are customized according to the needs and learning preferences of the user. It relies on a reference domain ontology and teaching multimedial interactive modules, referred to as Reusable Learning Objects (RLOs), which are annotated according to the concepts of the ontology. The SemSim semantic search method allows the selection of the set of RLOs that satisfy the user request at best in efficient way. This set is successively reorganized according to the learning preferences of the user. ELSE has been validated and experimented in the domain of osteoporosis, and the overall judgment about it is very positive, both in terms of usability and effectiveness of customization.

An interpolation‐based fast multipole method for higher‐order boundary elements on parametric surfaces

SummaryIn this article, a black‐box higher‐order fast multipole method for solving boundary integral equations on parametric surfaces in three spatial dimensions is proposed. Such piecewise smooth surfaces are the topic of recent studies in isogeometric analysis. Due to the exact surface representation, the rate of convergence of higher‐order methods is not limited by approximation errors of the surface. An element‐wise clustering strategy yields a balanced cluster tree and an efficient numerical integration scheme for the underlying Galerkin method. By performing the interpolation for the fast multipole method directly on the reference domain, the cost complexity in the polynomial degree is reduced by one order. This gain is independent of the application of either ‐ or ‐matrices. In fact, several simplifications in the construction of ‐matrices are pointed out, which are a by‐product of the surface representation. Extensive numerical examples are provided in order to quantify and qualify the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.