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Interface Model (interface + model)

Distribution by Scientific Domains

Engineering	62%

Selected Abstracts

A Human,Automation Interface Model to Guide Automation Design of System Functions

NAVAL ENGINEERS JOURNAL, Issue 1 2007
JOSHUA S. KENNEDY
A major component of the US Army's Future Combat Systems (FCS) will be a fleet of eight different manned ground vehicles (MGV). There are promises that "advanced automation" will accomplish many of the tasks formerly performed by soldiers in legacy vehicle systems. However, the current approach to automation design does not relieve the soldier operator of tasks; rather, it changes the role of the soldiers and the work they must do, often in ways unintended and unanticipated. This paper proposes a coherent, top-down, overarching approach to the design of a human,automation interaction model. First, a qualitative model is proposed to drive the functional architecture and human,automation interface scheme for the MGV fleet. Second, the proposed model is applied to a portion of the functional flow of the common crew station on the MGV fleet. Finally, the proposed model is demonstrated quantitatively via a computational task-network modeling program (Improved Performance Research and Integration Tool). The modeling approach offers insights into the impacts on human task-loading, workload, and human performance. Implications for human systems integration domains are discussed, including Manpower and Personnel, Human Factors Engineering, Training, System Safety, and Soldier Survivability. The proposed model gives engineers and scientists a top-down approach to explicitly define and design the interactions between proposed automation schemes and the human crew. Although this paper focuses on the Army's FCS MGV fleet, the model and analytical processes proposed, or similar approaches, are appropriate for many manned systems in multiple domains (aviation, space, maritime, ground transportation, manufacturing, etc.). [source]

Velocity/interface model building in a thrust belt by tomographic inversion of global offset seismic data

GEOPHYSICAL PROSPECTING, Issue 1 2003
P. Dell'Aversana
Between September and November 1999, two test seismic lines were recorded in the southern Apennine region of southern Italy using the global offset technique, which involves the acquisition of a wide offset range using two simultaneously active seismic spreads. One consisted of a symmetrical spread moving along the line, with geophone arrays every 30 m and a maximum offset of 3.6 km. The other one consisted of fixed geophone arrays every 90 m with a maximum offset of 18 km. This experimental acquisition project was carried out as part of the enhanced seismic in thrust belt (ESIT) research project, funded by the European Union, Enterprise Oil and Eni-Agip. An iterative and interactive tomographic inversion of refraction/reflection arrivals was carried out on the data from line ESIT700 to produce a velocity/interface model in depth, which used all the available offsets. The tomographic models allowed the reconstruction of layer interface geometries and interval velocities for the target carbonate platform (Apula) and the overburden sequence. The value of this technique is highlighted by the fact that the standard approach, based on near-vertical reflection seismic and a conventional processing flow, produced poor seismic images in both stack and migrated sections. [source]

Monotonic and cyclic modeling of interface between geotextile and gravelly soil

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2010
Ga Zhang
Abstract This paper describes a modified elasto-plasticity damage model to capture monotonic and cyclic behavior of the interface between a geotextile and gravelly soil. New damage variable and shear strength criterion are introduced on the basis of test observations. The formulations of the modified model are obtained by extending those of the original interface model. The model parameters with physical meaning are easily determined from a group of cyclic shear tests and a confining compression test. The model predictions are compared with the results of a series of direct shear tests and large-scale pullout tests. The comparison results demonstrate that the model accurately describes the monotonic and cyclic stress,strain relationship of the interface between a geotextile and gravelly soil while capturing new characteristics: (1) the strength that is nonlinearly dependent on the normal stress; (2) significant shear strain-softening; (3) the comprehensive volumetric strain response with dependency on the shear direction; and (4) the evolution of behavior associated with the changes in the physical state that includes the geotextile damage. This model is used in a finite element analysis of pullout tests, indicating that the tensile modulus of a geotextile has a significant effect on the response of the geotextile,gravel system. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Direct assessment of structural resistance against pressurized fracture

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2003
G. Bolzon
Abstract The determination of the load bearing capacity of hydraulic structures such as dams, reservoirs and retaining walls requires the consideration of mixed-mode fracture, possibly driven by the fluid pressure, in correspondence to artificial and natural joints (or cracks, in the latter case). A friction-cohesive softening interface model with coupled degradation of normal and tangential strength is introduced here to account for the essential features of the joint behaviour; its predictive capability is assessed through extensive calculations. Alternative numerical techniques resting on the discrete-crack approach are considered, focusing on simplified approaches for the direct appraisal of the structural resistance. Comparison is made with the results of evolutionary analyses, based on a priori piecewise linearization of the interface model and on ,exact integration'. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Application of thermodynamics to the global modelling of shallow foundations on frictional material

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2001
Y. Le Pape
Abstract Soil,shallow foundation interaction has been theoretically analysed within the framework of thermomechanics. The design of a global interaction model has been achieved with an original treatment of the Clausius,Duhem inequality. The role of the gravity volume forces is emphasized. The paper is focused on a strip footing based on dense sand and subjected to time-independent plastic processes. The theoretical approach has confirmed that an associated global flow rule cannot be expected to hold true. The analysis of the sources of dissipation has led to the development of a soil,footing interface model and a complete interaction model accounting for the interface constraints and the intrinsic frictional properties of the soil. Finally, the abilities of the complete model are checked by comparisons with experimental results found in the literature. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Variational approach to the free-discontinuity problem of inverse crack identification

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008
R. TsotsovaArticle first published online: 17 DEC 200
Abstract This work presents a computational strategy for identification of planar defects (cracks) in homogenous isotropic linear elastic solids. The underlying strategy is a regularizing variational approach based on the diffuse interface model proposed by Ambrosio and Tortorelli. With the help of this model, the sharp interface problem of crack identification is split into two coupled elliptic boundary value problems solved using the finite element method. Numerical examples illustrate the application of the proposed approach for effective reconstruction of the position and the shape of a single crack using only the information collected on the surface of the analyzed body. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Approximation of Cahn,Hilliard diffuse interface models using parallel adaptive mesh refinement and coarsening with C1 elements

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008
Roy H. Stogner
Abstract A variational formulation and C1 finite element scheme with adaptive mesh refinement and coarsening are developed for phase-separation processes described by the Cahn,Hilliard diffuse interface model of transport in a mixture or alloy. The adaptive scheme is guided by a Laplacian jump indicator based on the corresponding term arising from the weak formulation of the fourth-order non-linear problem, and is implemented in a parallel solution framework. It is then applied to resolve complex evolving interfacial solution behavior for 2D and 3D simulations of the classic spinodal decomposition problem from a random initial mixture and to other phase-transformation applications of interest. Simulation results and adaptive performance are discussed. The scheme permits efficient, robust multiscale resolution and interface characterization. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Combining interface damage and friction in a cohesive-zone model

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006
Giulio Alfano
Abstract A new method to combine interface damage and friction in a cohesive-zone model is proposed. Starting from the mesomechanical assumption, typically made in a damage-mechanics approach, whereby a representative elementary area of the interface can be additively decomposed into an undamaged and a fully damaged part, the main idea consists of assuming that friction occurs only on the fully damaged part. The gradual increase of the friction effect is then a natural outcome of the gradual increase of the interface damage from the initial undamaged state to the complete decohesion. Suitable kinematic and static hypotheses are made in order to develop the interface model whereas no special assumptions are required on the damage evolution equations and on the friction law. Here, the Crisfield's interface model is used for the damage evolution and a simple Coulomb friction relationship is adopted. Numerical and analytical results for two types of constitutive problem show the effectiveness of the model to capture all the main features of the combined effect of interface damage and friction. A finite-step interface law has then been derived and implemented in a finite-element code via interface elements. The results of the simulations made for a fibre push-out test and a masonry wall loaded in compression and shear are then presented and compared with available experimental results. They show the effectiveness of the proposed model to predict the failure mechanisms and the overall structural response for the analysed problems. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A cross-cultural test of the work-family interface in 48 countries

JOURNAL OF MARRIAGE AND FAMILY, Issue 5 2004
E. Jeffrey Hill
This study tests a cross-cultural model of the work-family interface. Using multigroup structural equation modeling with IBM survey responses from 48 countries (N= 25,380), results show that the same work-family interface model that fits the data globally also fits the data in a four-group model composed of culturally related groups of countries, as well as a two-group gender model. This supports a transportable rather than a culturally specific or gender-specific work-family interface model: notably, job flexibility related to reduced work-family conflict, reduced family-work conflict, and enhanced work-family fit. Work-family fit related to increased job satisfaction. Findings suggest that investment by multinational companies in job flexibility initiatives may represent a dual-agenda way to benefit men, women, and businesses in diverse cultures. [source]

Non-homogeneous Navier,Stokes systems with order-parameter-dependent stresses

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 13 2010
Helmut Abels
Abstract We consider the Navier,Stokes system with variable density and variable viscosity coupled to a transport equation for an order-parameter c. Moreover, an extra stress depending on c and ,c, which describes surface tension like effects, is included in the Navier,Stokes system. Such a system arises, e.g. for certain models of granular flows and as a diffuse interface model for a two-phase flow of viscous incompressible fluids. The so-called density-dependent Navier,Stokes system is also a special case of our system. We prove short-time existence of strong solution in Lq -Sobolev spaces with q>d. We consider the case of a bounded domain and an asymptotically flat layer with a combination of a Dirichlet boundary condition and a free surface boundary condition. The result is based on a maximal regularity result for the linearized system. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Effect of marangoni stresses on the deformation and coalescence in compatibilized immiscible polymer blends

POLYMER ENGINEERING & SCIENCE, Issue 10 2002
Peter Van Puyvelde
The effect of physical compatibilization on the deformation and coalescence of droplets in immiscible polymer blends is discussed. Evidence is provided for the existence of concentration gradients in block copolymers along the interface during deformation. This causes complex changes in droplet shapes during deformation and relaxation. These concentration gradients also result in Marangoni stresses, which stabilize the droplets against deformation and breakup. Coalescence experiments have been performed, varying both the compatibilizer concentration and the shear rate. Existing coalescence models have been evaluated. An empirical extension of Chesters' partially mobile interface model is presented, that treats the effects of Marangoni stresses on the coalescence process as a higher effective viscosity ratio. [source]

A Finite Element Approach for the Simulation of Quasi-Brittle Fracture

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
Oliver Hilgert
In the context of a strong discontinuity approach, we propose a finite element formulation with an embedded displacement discontinuity. The basic assumption of the proposed approach is the additive split of the total displacement field in a continuous and a discontinuous part. An arbitrary crack splits the linear triangular finite element into two parts, namely a triangular and a quadrilateral part. The discontinuous part of the displacement field in the quadrilateral portion is approximated using linear shape functions. For these purposes, the quadrilateral portion is divided into two triangular parts which is in this way similar to the approach proposed in [5]. In contrast, the discretisation is different compared to formulations proposed in [1] and [3], where the discontinuous part of the displacement field is approximated using bilinear shape functions. The basic theory of the underlying finite element formulation and a cohesive interface model to simulate brittle fracture are presented. By means of representative numerical examples differences and similarities of the present formulation and the formulations proposed in [1] and [3] are highlighted. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

New model for the hydroxyapatite,octacalcium phosphate interface

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2003
M. E. Fernández
Some experimental results have indicated that hydroxyapatite (HA) and octacalcium phosphate (OCP) can form an epitaxic interface. Subsequently the OCP,HA interface has become of great biological interest in the context of mineralized tissue formation. In this work a new OCP,HA interface model based on Brown's proposed configuration [Brown (1962), Nature, 197, 1048,1050] and using the minimum interface free-energy optimization is presented. This new model is formed by half a unit cell of HA and one unit cell of OCP, as in Brown's model, but in our case [110] of HA is `glued' with [010] of OCP. Therefore, the relationship found was: [000]HA parallel to [001]OCP and [110]HA parallel to [010]OCP. Self-consistent field methods were used for the analysis of Brown's model and ours. It is shown that the atoms in our model have similar environments as in the HA and OCP unit cells and that, as a result of the differences between HA and OCP unit-cell parameters, this interface presents misfit-dislocation-like features. High-resolution transmission electron microscopy (HREM) simulated images for the new interface model have been included and, when they are compared with the experimental ones, the similarity is quite good. [source]