3D Bodies Research Articles

3D magnetization inversion using fuzzyc-means clustering with application to geology differentiation

The presence of remanent magnetization has hindered the application of generalized 3D magnetic inversion in exploration geophysics because of the unknown and variable magnetization directions. Although many authors have developed different approaches to deal with this difficulty, it remains a challenge. We have developed a new approach for inverting the total-field magnetic anomaly to recover a 3D distribution of magnetization by using a fuzzy c-means clustering technique. The inversion approximates the variation of magnetization directions with a small number of possible orientations and thereby achieves stability in recovered magnetization directions and improves the spatial imaging of magnetization magnitude. We have also found that the inverted magnetization directions can yield more information than does a standard magnetic susceptibility inversion and provide a new opportunity for magnetic interpretation. The magnitude of magnetization helps to define the configuration and structure of causative bodies in 3D, whereas the magnetization directions can help distinguish between different causative bodies and thereby assist in efforts such as geology differentiation. Thus, 3D magnetization inversion enables the complete use of the magnetic anomaly in the presence of remanent magnetization. We have used synthetic and field data sets to illustrate the algorithm, demonstrate the feasibility of geology differentiation using recovered magnetization directions, and develop a means to quantify the confidence of differentiation results.

Boundary Element Analysis of Interior Thermoelastic Stresses in Three-Dimensional Generally Anisotropic Bodies

AbstractThis paper is to present the treatment of internal thermoelastic stress analysis in 3D anisotropic bodies by the boundary element method (BEM). Fundamentally, thermal effects will give rise to an additional volume integral in the boundary integral equation (BIE). By applying the fundamental solutions represented by Fourier series, the volume integral has been analytically transformed to the boundary. For the present work, spatial differentiations of the integral equation are performed to give displacement gradients at internal points of interest. This differentiated integral equation is further implemented to perform thermoelastic stress analysis inside 3D anisotropic bodies. This analysis is particularly important in engineering applications when thermoelastic stresses concentrations are present inside the bodies. The present work is the first BEM implementation for this study by the transformed BIE. In the end, two benchmark examples are tested to demonstrate the applicability of the present BEM treatment.

Visual biases in judging body weight.

There has been a steady rise in obesity levels in Western countries, and a contributory factor is people's failure to recognize weight gain. Two important visual perceptual biases, contraction bias and Weber's law, that have hitherto been ignored in the obesity literature could contribute to this problem. Contraction bias predicts that the weight of obese bodies will be underestimated and the degree of underestimation will increase as body mass index (BMI) increases. Weber's law predicts that change in the body size will become progressively harder to detect as their BMI increases. In Experiment 1, 29 women participants estimated the weight of 120 women varying in their body mass. In Experiment 2, 28 women participants judged which body was the heavier in a 2-alternative forced choice paradigm. In Experiment 1, as predicted the participants showed a progressive underestimation of overweight and obese bodies, β1 =0.71, t=26.96, p<.0001. For Experiment 2, there was a significant effect of the BMI of the bodies being judged on the just noticeable difference needed to discriminate between them: F(1,196)=89.39, p<.0001 for 3D bodies and F(1,86.5)=44.57, p<.0001 for digital photographs. Normal visual perceptual biases influence our ability to determine body size: contraction bias and Weber's law mean that as bodies become overweight and obese, it is harder to judge their weight and detect any increase in size. These effects may therefore compromise people's ability to recognize weight gain and undertake compensatory weight control behaviours. Statement of contribution What is already known on this subject? It is common knowledge that obesity levels in the West are rapidly rising and that people fail to recognize weight gain. What has not been widely recognized before is that there are sound perceptual reasons for this failure. Here, we identify two such perceptual biases. What does this study add? Weber's law and contraction bias compromise people's ability to recognize weight gain. It becomes progressively harder to discriminate the size of bodies as their body mass index increases. This compromises the ability to recognize weight gain and undertake compensatory behaviours.

Fourier forward modeling of vector and tensor gravity fields due to prismatic bodies with variable density contrast

Prismatic bodies with variable density contrasts are very useful in modeling and inversion of gravity anomalies for sedimentary basins, in which some simple mathematical functions offer better approximations for the density-depth relationship of the basin fill than a constant density model. We have explored Fourier-domain modeling of vector and tensor gravity anomalies due to 2D and 3D prismatic bodies following a wide class of variable density functions. We placed the emphasis on general polynomial models because they provided a flexible way to approximate arbitrary density functions. The recently proposed Gauss-fast Fourier transform method was applied to improve the accuracy of inverse Fourier transform. The numerical performance of the presented method was examined by comparing with space-domain analytical, seminumerical, or completely numerical solutions. Singularity and numerical stability of the algorithm were also analyzed with ranges of numerical stability for polynomial density models of different orders specified. Truncation errors of Fourier forward methods were estimated quantitatively using relevant model parameters, and the behavior was observed through theoretical analysis and model tests. Synthetic models, of 2D and 3D prisms with variable density contrasts, found the accuracy, efficiency, and flexibility of the method. We also interpreted a real data example of the gravity profile across the San Jacinto graben.

Data-driven three-dimensional reconstruction of human bodies using a mobile phone app

The advances and availability of technologies for the acquisition, registration and analysis of the three-dimensional (3D) shape of human bodies (or body parts) are resulting in the formation of large databases of parameterised meshes from which digital human body models can be derived. Such models can be used for the data-driven reconstruction of parameterised human body shapes from partial information such as one-dimensional (1D) measurements or 2D images. In this paper, we propose a new method for the reconstruction of 3D bodies from images gathered with a smartphone or tablet. Moreover, the method is implemented into a prototype app and tested at different levels through three experimental studies including synthetic models, 1:10 scale figurines and real children. The results demonstrate the feasibility of acquiring reliable anthropometric information easily at home by non-experts. This method and implementation have great potential for their application to the personalisation, size recommendation and virtual try-on simulation of wearable products.

Analysis of thermoelastic stress-concentration around oblate cavities in three-dimensional generally anisotropic bodies by the boundary element method

In this article, stress concentrations around cavities in 3D generally anisotropic bodies are investigated using the boundary element method (BEM), where the associated volume integral is analytically transformed to the boundary. All derivations are based upon the Fourier-series representations of the fundamental solutions, including Green's function of displacements and its derivatives. This approach of analytical transformation has fully restored the BEM's distinctive notion that only the boundary needs to be discretized. The goal of the present work is to investigate the thermoelastic stress-concentration around cavities in 3D anisotropic bodies by use of the analytically transformed boundary integral equation (BIE). The work has fully recovered the BEM's nature of boundary discretization for treating 3D generally anisotropic thermoelasticity. This is the first implemented work that successfully treats thermoelastic problems for 3D generally anisotropic solids by the analytically transformed BIE. In the paper, Interesting phenomena are observed from the analyses of stress concentrations around oblate cavities and some discussions are made.

3D Magnetotellurics for Mineral Exploration beneath Cover

As a consequence of diminishing shallow mineral resources, the exploration industry has turned its focus to deeper targets. For this reason, the magnetotelluric (MT) method has gained much attention due to its unique penetration in regions of thick cover sequences. As the setting and geometries of mineral deposits are often complex, 3D models are required for their interpretation.However, there has been little critical analysis of the ability of 3D MT surveys to recover structural geometry. A comparison of synthetic model responses demonstrate that while MT is greatly sensitive to conductive and symmetrical bodies at depth, its resolution for detecting finite 3D bodies is significantly reduced under conductive regolith cover. Although 2D inversions can recover the geometry of finite conductive bodies, it is possible to successfully interpret 2D survey data using 3D inversion algorithms. Utilising all components of the impedance tensor, off-profile 3D conductive structure can be obtained from 2D survey data alone.

3D parametric human modeling for warp-knitted seamless garment

Purpose – The purpose of this paper is to develop a parametric design method for 3D human bodies to be used in computer-aided style design and the 3D presentations of warp-knitted seamless garment. Design/methodology/approach – In order to obtain 3D human bodies of different sizes, all of which have been based on anthropometric measurement, a human body model template was constructed by importing vertices and facets information in an OBJ model file which had been exported from POSER. A parametric model was then established by extracting feature information from the template model using a method combining 3D geometry analysis and human semantic analysis; this information included the template model’s feature points and measurements. By applying a mesh deformation method, based on the radius basis function interpolation, to the template model, different size human bodies were then generated according to user-specific anthropometric measurements. Findings – The test results validated the method presented in this paper as a useful and effective approach to generate diffident size human models from a template model by modifying anthropometric measurements, which establishes a foundation for the style design and 3D presentations of warp-knitted seamless garments. Originality/value – This paper provides parametric design methods for generating bodies of varying size according to different anthropometric measurements in the 3D domain, which is the basis of style design and 3D presentation for warp-knitted seamless garments.

A new method based on compressive sensing for monostatic scattering analysis

ABSTRACTA new approach based on the Method of Moments (MoM) and the Compressive Sensing (CS) is proposed to efficiently analyze the electromagnetic monostatic scattering from an arbitrary three‐dimensional (3D) target in this article. The Nyquist–Shannon's sampling theorem must be satisfied when traditional MoM is utilized to solve monostatic scattering problems, which needs a large calculating quantity and is time consuming. Therefore, the CS technique is introduced into the MoM to decrease the sampling rate of the incident angles. Simulation results obtained from the proposed method are verified by comparison with traditional MoM results, which prove an excellent accuracy computation. And the comparison of the simulation time illustrates that the method we present has a very high efficiency in monostatic scattering from conducting 3D bodies. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2457–2461, 2015

The finite element method for fractional non-local thermal energy transfer in non-homogeneous rigid conductors

In a non-local fractional-order model of thermal energy transport recently introduced by the authors, it is assumed that local and non-local contributions coexist at a given observation scale: while the first is described by the classical Fourier transport law, the second involves couples of adjacent and non-adjacent elementary volumes, and is taken as proportional to the product of the masses of the interacting volumes and their relative temperature, through a material-dependent, distance-decaying power-law function. As a result, a fractional-order heat conduction equation is derived. This paper presents a pertinent finite element method for the solution of the proposed fractional-order heat conduction equation. Homogenous and non-homogeneous rigid bodies are considered. Numerical applications are carried out on 1D and 2D bodies, including a standard finite difference solution for validation.

Constant acceleration exit of two-dimensional free-surface-piercing bodies

The forced constant acceleration exit of two-dimensional bodies through a free-surface is computed for various 2D bodies (symmetric wedges, asymmetric wedges, truncated wedges and boxes). The calculations are based on the fully non-linear time-stepping complex-variable method of Vinje and Brevig (1981). The model was formulated as an initial boundary-value problem (IBVP) with boundary conditions specified on the boundaries (dynamic and kinematic free-surface boundary conditions) and initial conditions at time zero (initial velocity and position of the body and free-surface particles). The formulated problem was solved by means of a boundary-element method using collocation points on the boundary of the domain and stepped forward in time using Runge–Kutta and Hamming predictor–corrector methods. Numerical results for the deformed free-surface profile, pressure along the wetted region of the bodies and force experienced by the bodies are given for the exit. The analytical added-mass force is presented for the exit of symmetric wedges and boxes with constant acceleration using conformal mappings. To verify the numerical results, the added-mass force and the numerical force are compared and give good agreement for the exit of a symmetric wedge at a time zero (t=0) as expected but only moderate agreement for the box.

Isogeometric treatment of large deformation contact and debonding problems with T-splines: a review

Abstract Within a setting where the isogeometric analysis (IGA) has been successful at bringing two different research fields together, i.e. Computer Aided Design (CAD) and numerical analysis, T-spline IGA is applied in this work to frictionless contact and mode-I debonding problems between deformable bodies in the context of large deformations. Based on the concept of IGA, the smooth basis functions are adopted to describe surface geometries and approximate the numerical solutions, leading to higher accuracy in the contact integral evaluation. The isogeometric discretizations are here incorporated into an existing finite element framework by using Bézier extraction, i.e. a linear operator which maps the Bernstein polynomial basis on Bézier elements to the global isogeometric basis. A recently released commercial T-spline plugin for Rhino is herein used to build the analysis models adopted in this study. In such context, the continuum is discretized with cubic T-splines, as well as with Non Uniform Rational B-Splines (NURBS) and Lagrange polynomial elements for comparison purposes, and a Gauss-point-to-surface (GPTS) formulation is combined with the penalty method to treat the contact constraints. The purely geometric enforcement of the non-penetration condition in compression is generalized to encompass both contact and mode-I debonding of interfaces which is approached by means of cohesive zone (CZ) modeling, as commonly done by the scientific community to analyse the progressive damage of materials and interfaces. Based on these models, non-linear relationships between tractions and relative displacements are assumed. These relationships dictate both the work of separation per unit fracture surface and the peak stress that has to be reached for the crack formation. In the generalized GPTS formulation an automatic switching procedure is used to choose between cohesive and contact models, depending on the contact status. Some numerical results are first presented and compared in 2D for varying resolutions of the contact and/or cohesive zone, including frictionless sliding and cohesive debonding, all featuring the competitive accuracy and performance of T-spline IGA. The superior accuracy of T-spline interpolations with respect to NURBS and Lagrange interpolations for a given number of degrees of freedom (Dofs) is always verified. The isogeometric formulation is also extended to 3D bodies, where some examples in large deformations based on T-spline discretizations show an high smoothness of the reaction history curves.

Construction of a 3D meso-structure and analysis of mechanical properties for deposit body medium

For deposit body medium, the internal structural properties may be the controlling factors for the strength of the material and the mechanical response. Based on the results of soil-rock meso-statistics using digital imaging, a simulated annealing algorithm is adopted to expand the meso-structural features of deposit bodies in 3D. The construction of the 3D meso-structure of a deposit body is achieved, and then the particle flow analysis program PFC3D is used to simulate the mechanical properties of the deposit body. It is shown that with a combination of the simulated annealing algorithm and the statistical feature functions, the randomness and heterogeneity of the rock distribution in the 3D inner structure of deposit body medium can be realized, and the reconstructed structural features of the deposit medium can match the features of the digital images well. The spatial utilizations and the compacting effects of the body-centered cubic, hexagonal close and face-centered packing models are high, so these structures can be applied in the simulations of the deposit structures. However, the shear features of the deposit medium vary depending on the different model constructive modes. Rocks, which are the backbone of the deposit, are the factors that determine the shear strength and deformation modulus of the deposit body. The modeling method proposed is useful for the construction of 3D meso-scope models from 2D meso-scope statistics and can be used for studying the mechanical properties of mixed media, such as deposit bodies.

Stem cell derived in vivo-like human cardiac bodies in a microfluidic device for toxicity testing by beating frequency imaging.

Beating in vivo-like human cardiac bodies (CBs) were used in a microfluidic device for testing cardiotoxicity. The CBs, cardiomyocyte cell clusters derived from induced pluripotent stem cells, exhibited typical structural and functional properties of the native human myocardium. The CBs were captured in niches along a perfusion channel in the device. Video imaging was utilized for automatic monitoring of the beating frequency of each individual CB. The device allowed assessment of cardiotoxic effects of drug substances doxorubicin, verapamil and quinidine on the 3D clustered cardiomyocytes. Beating frequency data recorded over a period of 6 hours are presented and compared to literature data. The results indicate that this microfluidic setup with imaging of CB characteristics provides a new opportunity for label-free, non-invasive investigation of toxic effects in a 3D microenvironment.

FEM‐Simulation of “Die‐Less Hydroforming”

AbstractThe following contribution focuses on the FEM‐simulation of “Die‐Less‐Hydroforming” using LS‐DYNA. That specific forming technology is used to create structures by inflating initial seal‐welded flat 2D blanks as well as 3D hollow bodies without using any die, mould or punch in contrast to conventional hydroforming (e.g. tube hydroforming or hydromechanical deep drawing). (© 2014 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Growth Properties and Pluripotency Marker Expression of Spontaneously Formed Three-dimensional Aggregates of Human Adipose-derived Stem Cells.

Background and Objectives:Recent findings suggest that therapeutic potential of mesenchymal stem cells (MSCs) could be increased through aggregation into three-dimensional (3D) bodies, and different culture methods have been employed to obtain 3D spheroids of MSCs. In the current study we report accidentally encountered spontaneous formation of adipose-derived stem cell (ASC) bodies in standard ASC culture of a single donor.Methods and Results:Human ASCs from passages 1 to 3, cultured in a medium containing 5% autologous serum (AS), spontaneously clustered and formed floating 3D bodies. After a transfer of floating ASC bodies onto new adherent plastic dish, they attached to the surface and gradual migration of spindle-shaped ASCs out of the bodies was detected. A substitution of AS with allogeneic sera did not hinder this ability, but commercial medium containing fetal bovine serum delayed the process. Substantial part of ASCs surrounding transferred ASC bodies showed alkaline phosphatase (AP) activity, while ASC aggregates were AP negative. Similar 3D bodies formed when ASCs were grown on an uncoated glass surface. These ASC aggregates as well as clusters of ASCs, where formation of the 3D bodies is initiated, expressed pluripotency marker NANOG, but the expression of OCT4A was not detected.Conclusions:Obtained results suggest that spontaneously formed ASC aggregates may represent a more primitive cell subpopulation within the individual ASC culture. The ability to form 3D aggregates, the expression of NANOG, and the lack of the AP activity may be used to enrich ASC cultures with potentially more primitive cells serving as an excellent basis for therapeutic applications.

Percolation of the interacting elastic stress fields of aligned cracks as an alternative explanation of critical crack densities

Abstract The concept that the lithosphere is in a general critical, or near-critical, mechanical state has previously assumed spatial intersection of fractures at the critical point. This paper provides an initial basis for an alternative mechanism in which elastic interactions between aligned, open, spatially separated (micro-)cracks in rock can, by themselves, lead to a continuous phase change at a critical threshold of crack density lower than that required for crack coalescence. The existence of a critical density of aligned cracks is first demonstrated on a regular 2D hexagonal grid when subjected to a central stress perturbation; at this critical density the elastic tensile stress interactions have a long-range effect. From the results of those calculations an approximation of the tensile stress field around a crack in 3D is provided. The percolation behaviour of such 3D bodies is discussed and a critical crack density in 3D for elastic interaction of 0.035 is deduced. This falls within the range of crack densities (0.015–0.045) interpreted from observations of shear-wave splitting in many different rocks. The possibility that critical crack interactions can be mostly elastic provides one explanation of the long-range nature of correlations in flowrate fluctuations in oilfields without large-scale seismicity.

Recognition of Symmetric 3D Bodies

The paper deals with the recognition of symmetric three-dimensional (3D) bodies that can be rotated and translated. We provide a complete list of all existing combinations of rotation and reflection symmetries in 3D. We define 3D complex moments by means of spherical harmonics, and the influence of individual symmetry groups on complex moment values is studied. Each particular symmetry pre-defines certain moment values. These moments can no longer differentiate between two objects of the same symmetry, which decreases the recognition power of the feature set. They should not be included when constructing the invariants. Translation and rotation invariants up to the fourth order are presented and their performance is studied on both artificial and real data.

Formulation of a new set of Simplified Conventional Burnett equations for computation of rarefied hypersonic flows

For computation of rarefied flows in continuum-transition regime with Knudsen number Kn of O(1), Burnett equations have been proposed about a century ago as a set of extended hydrodynamics equations (EHE) that represent the second-order departure from thermodynamic equilibrium in the Chapman–Enskog expansion of Boltzmann equation; the first order terms in the expansion result in the Navier–Stokes equations. Over the years, a number of variations of original Burnett equations have been proposed in the literature known as the Conventional Burnett equations, the Augmented Burnett equations and the BGK–Burnett equations. In this paper, another simpler set of Burnett equations is proposed by order of magnitude analysis in the limit of high Mach numbers for hypersonic flow applications. These equations, designated as ‘Simplified Conventional Burnett (SCB)’ equations are stable under small perturbations and do not violate the second law of thermodynamics. An implicit numerical solver is developed for the solution of SCB equations. The SCB equations are applied to compute the hypersonic flow past 2D and 3D blunt bodies for Kn in continuum and continuum-transition regime. The SCB solutions are compared with the Navier–Stokes and DSMC solutions. It is shown that the SCB equations can be employed to compute the hypersonic flow past bodies in continuum-transition regime with much less computational effort because of their simplicity compared to Conventional and Augmented Burnett equations.

Finite Element Simulation of Diffusion and Precipitation with Application to Internal Oxidation of Ni-Xwt%Cr Alloys at 950°C

For the simulation of internal oxidation phenomena, different numerical approaches are proposed in the literature based on 1D finite differences or on explicit time integration schemes which need small time-steps leading to very long computation times. The aim of this paper is to detail a multi-dimentional finite element approach which is coupled with an efficient implicit time integration algorithm. The thermodynamic activities and the total mass fractions are both used as principal nodal variables. The use of finite elements rather than finite differences greatly facilitates the meshing of 2D and 3D bodies. Its implicit time-integration allows using much larger time-steps without any degradation of the results. An application is proposed for the modeling of internal oxidation of chromia for Ni-Xwt%Cr alloys at 950°C by considering the barrier effect of precipitates.