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Sample records for 3d magnetic inversion

  1. 3D Magnetic inversion and remanence: solving the problem

    NASA Astrophysics Data System (ADS)

    Thomson, V.; Morris, W.

    2003-04-01

    3D inversion of surface magnetic data is a common processing technique when used in mineral exploration. The major drawback of most 3D inversion algorithms is that they assume that the surface magnetic anomaly is produced by induced magnetization and that there are no remanent magnetization or demagnetization effects present. This has a significant impact when modeling magnetic data that has remanent magnetization. The magnetic anomaly produced by a dipping subsurface body will be identical for a consistent relationship between the dip of the body and the dip of the magnetic vector, regardless of the actual dip of the magnetic body. For example, in the case where a subsurface body is dipping, such as a dipping dike, the dip estimated by the inversion routine will be correct only if induced magnetization is present. This has serious implications for mineral exploration. A solution to the remanence problem is to model the surface magnetic anomaly using a constrained 2D approach rather than 3D. Using a priori information on dip and strike length of a source body, it is possible to approximate the remanence direction and intensity. The 2D solutions can then be rendered into a 3D imaging package to create a model in 3D. A case study was performed on a mafic-ultramafic layered igneous intrusion located in Big Trout Lake, northwestern Ontario, Canada. Large layered igneous intrusions are known to have significant remanence. Like many other layered igneous intrusions such as the Bushveld Complex in South Africa, the Big Trout Lake Complex is highly prospective for Platinum Group Elements (PGEs). Intruded during Archean time, the Big Trout Lake Complex has been subsequently folded and faulted to near vertical. As a consequence of limited surface exposures, knowledge of layering within the pluton and the extent of deformation of the pluton is very limited. Newly acquired high-resolution aeromagnetic data shows a strongly mineralized horizon within the intrusion that

  2. Joint inversions of two VTEM surveys using quasi-3D TDEM and 3D magnetic inversion algorithms

    NASA Astrophysics Data System (ADS)

    Kaminski, Vlad; Di Massa, Domenico; Viezzoli, Andrea

    2016-05-01

    In the current paper, we present results of a joint quasi-three-dimensional (quasi-3D) inversion of two versatile time domain electromagnetic (VTEM) datasets, as well as a joint 3D inversion of associated aeromagnetic datasets, from two surveys flown six years apart from one another (2007 and 2013) over a volcanogenic massive sulphide gold (VMS-Au) prospect in northern Ontario, Canada. The time domain electromagnetic (TDEM) data were inverted jointly using the spatially constrained inversion (SCI) approach. In order to increase the coherency in the model space, a calibration parameter was added. This was followed by a joint inversion of the total magnetic intensity (TMI) data extracted from the two surveys. The results of the inversions have been studied and matched with the known geology, adding some new valuable information to the ongoing mineral exploration initiative.

  3. 3D stochastic joint inversion of gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Shamsipour, Pejman; Marcotte, Denis; Chouteau, Michel

    2012-04-01

    A novel stochastic joint inversion method based on cokriging is applied to estimate density and magnetic susceptibility distributions from gravity and total magnetic field data. The method fully integrates the physical relations between density-gravity, on one hand, and magnetic susceptibility-total magnetic field, on the other hand. As a consequence, when the data are considered noise-free, the responses from the inverted density and susceptibility data exactly reproduce the observed data. The required density and magnetic susceptibility auto- and cross covariance are assumed to follow a linear model of coregionalization (LCM). The parameters of the LCM are estimated from v-v plot fitting of the gravity and total magnetic experimental covariances. The model is tested on two synthetic cases and one real data set, the Perseverance mine (Quebec, Canada). Joint inversions are compared to separate inversions. The joint inversions better recover the known models in the synthetic cases. With the real data set, better definition and location of the mineralized lenses are achieved by joint inversion.

  4. Lithologic identification & mapping test based on 3D inversion of magnetic and gravity

    NASA Astrophysics Data System (ADS)

    Yan, Jiayong; Lv, Qingtian; Qi, Guang; Zhao, Jinhua; Zhang, Yongqian

    2016-04-01

    Though lithologic identification & mapping to achieve ore concentration district transparent within 5km depth is the main way to realize deep fine structures study, to explore deep mineral resources and to reveal metallogenic regularity of large-scale ore district . Owing to the wide covered area, high sampling density and mature three-dimensional inversion algorithm of gravity and magnetic data, so gravity and magnetic inversion become the most likely way to achieve three-dimensional lithologic mapping at the present stage. In this paper, we take Lu-zong(Lujiang county to Zongyang county in Anhui province ,east China) ore district as a case, we proposed lithologic mapping flow based 3D inversion of gravity magnetic and then carry out the lithologic mapping test. Lithologic identification & mapping flow is as follows: 1. Analysis relations between lithology and density and magnetic susceptibility by cross plot. 2.Extracting appropriate residual anomalies from high-precision Bourger gravity and aeromagnetic. 3.Use same mesh, do 3D magnetic and gravity inversion respectively under prior information constrained, and then invert susceptibility and density 3D model. 4. According setp1, construct logical topology operations between density 3D model and susceptibility. 5.Use the logical operations, identify lithogies cell by cell in 3D mesh, and then get 3D lithological model. According this flow, we obtained three-dimensional distribution of five main type lithologies in the Lu-Zong ore district within 5km depth. The result of lithologic mapping not only showed that the shallow characteristics and surface geological mapping are basically Coincide,more importantly ,it reveals the deeper lithologic changes.The lithlogical model make up the insufficient of surface geological mapping. The lithologic mapping test results in Lu-Zong ore concentration district showed that lithological mapping using 3D inversion of gravity and magnetic is a effective method to reveal the

  5. 3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

    NASA Astrophysics Data System (ADS)

    Tietze, Kristina; Ritter, Oliver; Egbert, Gary D.

    2015-11-01

    With advancing computational resources, 3-D inversion techniques have become feasible in recent years and are now a more widely used tool for magnetotelluric (MT) data interpretation. Galvanic distortion caused by small-scale near-surface inhomogeneities remains an obstacle for 3-D MT inversion which so far has experienced little attention. If not considered properly, the effect on 3-D inversion can be immense and result in erroneous subsurface models and interpretations. To tackle the problem we implemented inversion of the distortion-free phase tensor into the ModEM inversion package. The dimensionless phase tensor components describe only variations of the conductivity structure. When inverting these data, particular care has to be taken of the conductivity structure in the a priori model, which provides the reference frame when transferring the information from phase tensors into absolute conductivity values. Our results obtained with synthetic data show that phase tensor inversion can recover the regional conductivity structure in presence of galvanic distortion if the a priori model provides a reasonable assumption for the regional resistivity average. Joint inversion of phase tensor data and vertical magnetic transfer functions improves recovery of the absolute resistivity structure and is less dependent on the prior model. We also used phase tensor inversion for a data set of more than 250 MT sites from the central San Andreas fault, California, where a number of sites showed significant galvanic distortion. We find the regional structure of the phase tensor inversion results compatible with previously obtained models from impedance inversion. In the vicinity of distorted sites, phase tensor inversion models exhibit more homogeneous/smoother conductivity structures.

  6. 3D linear inversion of magnetic susceptibility data acquired by frequency domain EMI

    NASA Astrophysics Data System (ADS)

    Thiesson, J.; Tabbagh, A.; Simon, F.-X.; Dabas, M.

    2017-01-01

    Low induction number EMI instruments are able to simultaneously measure a soil's apparent magnetic susceptibility and electrical conductivity. This family of dual measurement instruments is highly useful for the analysis of soils and archeological sites. However, the electromagnetic properties of soils are found to vary over considerably different ranges: whereas their electrical conductivity varies from ≤ 0.1 to ≥ 100 mS/m, their relative magnetic permeability remains within a very small range, between 1.0001 and 1.01 SI. Consequently, although apparent conductivity measurements need to be inverted using non-linear processes, the variations of the apparent magnetic susceptibility can be approximated through the use of linear processes, as in the case of the magnetic prospection technique. Our proposed 3D inversion algorithm starts from apparent susceptibility data sets, acquired using different instruments over a given area. A reference vertical profile is defined by considering the mode of the vertical distributions of both the electrical resistivity and of the magnetic susceptibility. At each point of the mapped area, the reference vertical profile response is subtracted to obtain the apparent susceptibility variation dataset. A 2D horizontal Fourier transform is applied to these variation datasets and to the dipole (impulse) response of each instrument, a (vertical) 1D inversion is performed at each point in the spectral domain, and finally the resulting dataset is inverse transformed to restore the apparent 3D susceptibility variations. It has been shown that when applied to synthetic results, this method is able to correct the apparent deformations of a buried object resulting from the geometry of the instrument, and to restore reliable quantitative susceptibility contrasts. It also allows the thin layer solution, similar to that used in magnetic prospection, to be implemented. When applied to field data it initially delivers a level of contrast

  7. New 3D parallel GILD electromagnetic modeling and nonlinear inversion using global magnetic integral and local differential equation

    SciTech Connect

    Xie, G.; Li, J.; Majer, E.; Zuo, D.

    1998-07-01

    This paper describes a new 3D parallel GILD electromagnetic (EM) modeling and nonlinear inversion algorithm. The algorithm consists of: (a) a new magnetic integral equation instead of the electric integral equation to solve the electromagnetic forward modeling and inverse problem; (b) a collocation finite element method for solving the magnetic integral and a Galerkin finite element method for the magnetic differential equations; (c) a nonlinear regularizing optimization method to make the inversion stable and of high resolution; and (d) a new parallel 3D modeling and inversion using a global integral and local differential domain decomposition technique (GILD). The new 3D nonlinear electromagnetic inversion has been tested with synthetic data and field data. The authors obtained very good imaging for the synthetic data and reasonable subsurface EM imaging for the field data. The parallel algorithm has high parallel efficiency over 90% and can be a parallel solver for elliptic, parabolic, and hyperbolic modeling and inversion. The parallel GILD algorithm can be extended to develop a high resolution and large scale seismic and hydrology modeling and inversion in the massively parallel computer.

  8. 3D non-linear inversion of magnetic anomalies caused by prismatic bodies using differential evolution algorithm

    NASA Astrophysics Data System (ADS)

    Balkaya, Çağlayan; Ekinci, Yunus Levent; Göktürkler, Gökhan; Turan, Seçil

    2017-01-01

    3D non-linear inversion of total field magnetic anomalies caused by vertical-sided prismatic bodies has been achieved by differential evolution (DE), which is one of the population-based evolutionary algorithms. We have demonstrated the efficiency of the algorithm on both synthetic and field magnetic anomalies by estimating horizontal distances from the origin in both north and east directions, depths to the top and bottom of the bodies, inclination and declination angles of the magnetization, and intensity of magnetization of the causative bodies. In the synthetic anomaly case, we have considered both noise-free and noisy data sets due to two vertical-sided prismatic bodies in a non-magnetic medium. For the field case, airborne magnetic anomalies originated from intrusive granitoids at the eastern part of the Biga Peninsula (NW Turkey) which is composed of various kinds of sedimentary, metamorphic and igneous rocks, have been inverted and interpreted. Since the granitoids are the outcropped rocks in the field, the estimations for the top depths of two prisms representing the magnetic bodies were excluded during inversion studies. Estimated bottom depths are in good agreement with the ones obtained by a different approach based on 3D modelling of pseudogravity anomalies. Accuracy of the estimated parameters from both cases has been also investigated via probability density functions. Based on the tests in the present study, it can be concluded that DE is a useful tool for the parameter estimation of source bodies using magnetic anomalies.

  9. Interpretation of Magnetic Anomalies in Salihli (Turkey) Geothermal Area Using 3-D Inversion and Edge Detection Techniques

    NASA Astrophysics Data System (ADS)

    Timur, Emre

    2016-04-01

    There are numerous geophysical methods used to investigate geothermal areas. The major purpose of this magnetic survey is to locate the boudaries of active hydrothermal system in the South of Gediz Graben in Salihli (Manisa/Turkey). The presence of the hydrothermal system had already been inferred from surface evidence of hydrothermal activity and drillings. Firstly, 3-D prismatic models were theoretically investigated and edge detection methods were utilized with an iterative inversion method to define the boundaries and the parameters of the structure. In the first step of the application, it was necessary to convert the total field anomaly into a pseudo-gravity anomaly map. Then the geometric boudaries of the structures were determined by applying a MATLAB based software with 3 different edge detection algorithms. The exact location of the structures were obtained by using these boundary coordinates as initial geometric parameters in the inversion process. In addition to these methods, reduction to pole and horizontal gradient methods were applied to the data to achieve more information about the location and shape of the possible reservoir. As a result, the edge detection methods were found to be successful, both in the field and as theoretical data sets for delineating the boundaries of the possible geothermal reservoir structure. The depth of the geothermal reservoir was determined as 2,4 km from 3-D inversion and 2,1 km from power spectrum methods.

  10. 3D modeling inversion calculation of magnetic data using iterative reweighted least squares at the Lau basin, Southwest Pacific

    NASA Astrophysics Data System (ADS)

    Choi, S.; Kim, C.; Kim, H. R.; Park, C.; Park, H. Y.

    2015-12-01

    We performed the marine magnetic and the bathymetry survey in the Lau basin for finding the submarine hydrothermal deposits in October 2009. We acquired magnetic and bathymetry datasets by using Overhouser Proton Magnetometer SeaSPY(Marine Magnetics Co.) and Multi-Beam Echo Sounder EM120(Kongsberg Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly and reduction to the pole(RTP). The Lau basin is one of the youngest back-arc basins in the Southwest Pacific. This region was a lot of hydrothermal activities and hydrothermal deposits. In particular, Tofua Arc(TA) in the Lau basin consists of various and complex stratovolcanos(from Massoth et al., 2007).), We calculated the magnetic susceptibility distribution of the TA19-1 seamount(longitude:176°23.5'W, latitude: 22°42.5'W)area using the RTP data by 3-D magnetic inversion from Jung's previous study(2013). Based on 2D 'compact gravity inversion' by Last & Kubik(1983), we expend it to the 3D algorithm using iterative reweighted least squares method with some weight matrices. The used weight matrices are two types: 1) the minimum gradient support(MGS) that controls the spatial distribution of the solution from Porniaguine and Zhdanov(1999); 2) the depth weight that are used according to the shape of subsurface structures. From the modeling, we derived the appropriate scale factor for the use of depth weight and setting magnetic susceptibility. Furthermore, we have to enter a very small error value to control the computation of the singular point of the inversion model that was able to be easily calculated for modeling. In addition, we applied separately weighted value for the correct shape and depth of the magnetic source. We selected the best results model by change to converge of RMS. Compared between the final modeled result and RTP values in this study, they are generally similar to the each other. But the input values and the modeled values have slightly little difference

  11. 3D Gravity Inversion using Tikhonov Regularization

    NASA Astrophysics Data System (ADS)

    Toushmalani, Reza; Saibi, Hakim

    2015-08-01

    Subsalt exploration for oil and gas is attractive in regions where 3D seismic depth-migration to recover the geometry of a salt base is difficult. Additional information to reduce the ambiguity in seismic images would be beneficial. Gravity data often serve these purposes in the petroleum industry. In this paper, the authors present an algorithm for a gravity inversion based on Tikhonov regularization and an automatically regularized solution process. They examined the 3D Euler deconvolution to extract the best anomaly source depth as a priori information to invert the gravity data and provided a synthetic example. Finally, they applied the gravity inversion to recently obtained gravity data from the Bandar Charak (Hormozgan, Iran) to identify its subsurface density structure. Their model showed the 3D shape of salt dome in this region.

  12. 3D Electromagnetic inversion using conjugate gradients

    SciTech Connect

    Newman, G.A.; Alumbaugh, D.L.

    1997-06-01

    In large scale 3D EM inverse problems it may not be possible to directly invert a full least-squares system matrix involving model sensitivity elements. Thus iterative methods must be employed. For the inverse problem, we favor either a linear or non-linear (NL) CG scheme, depending on the application. In a NL CG scheme, the gradient of the objective function is required at each relaxation step along with a univariate line search needed to determine the optimum model update. Solution examples based on both approaches will be presented.

  13. 3D structural cartography based on magnetic and gravity data inversion - Case of South-West Algeria

    NASA Astrophysics Data System (ADS)

    Hichem, Boubekri; Mohamed, Hamoudi; Abderrahmane, Bendaoud; Ivan, Priezzhev; Karim, Allek

    2015-12-01

    This article presents the results of 3D aeromagnetic and gravity data inversion across the West African Craton (WAC) in South West Algeria. Although the used data have different origins and resolutions, the performed manual and automatic interpretation for each dataset shows a good correlation with some earlier geological studies of the region, major structural aspects of the locality, as well as other new structural features. Many curved faults parallel to the suture zone indicate the presence of terranes or the metacratonization of the WAC and a related fault network of great importance with NE-SW and NW-SE directions. The mega shear zones from north to south, which are visible at the surface in the Hoggar, are also observed along the Saharan Platform. The fact that these faults are observed since the Cambro-Ordovician in all crust (including the Saharan Basins) indicates that this area, which is situated on the border of the WAC, remained active during the entire period of time.

  14. 3-D radial gravity gradient inversion

    NASA Astrophysics Data System (ADS)

    Oliveira, Vanderlei C.; Barbosa, Valéria C. F.

    2013-11-01

    We have presented a joint inversion of all gravity-gradient tensor components to estimate the shape of an isolated 3-D geological body located in subsurface. The method assumes the knowledge about the depth to the top and density contrast of the source. The geological body is approximated by an interpretation model formed by an ensemble of vertically juxtaposed 3-D right prisms, each one with known thickness and density contrast. All prisms forming the interpretation model have a polygonal horizontal cross-section that approximates a depth slice of the body. Each polygon defining a horizontal cross-section has the same fixed number of vertices, which are equally spaced from 0° to 360° and have their horizontal locations described in polar coordinates referred to an arbitrary origin inside the polygon. Although the number of vertices forming each polygon is known, the horizontal coordinates of these vertices are unknown. To retrieve a set of juxtaposed depth slices of the body, and consequently, its shape, our method estimates the radii of all vertices and the horizontal Cartesian coordinates of all arbitrary origins defining the geometry of all polygons describing the horizontal cross-sections of the prisms forming the interpretation model. To obtain a stable estimate that fits the observed data, we impose constraints on the shape of the estimated body. These constraints are imposed through the well-known zeroth- and first-order Tikhonov regularizations allowing, for example, the estimate of vertical or dipping bodies. If the data do not have enough in-depth resolution, the proposed inverse method can obtain a set of stable estimates fitting the observed data with different maximum depths. To analyse the data resolution and deal with this possible ambiguity, we plot the ℓ2-norm of the residuals (s) against the estimated volume (vp) produced by a set of estimated sources having different maximum depths. If this s × vp curve (s as a function of vp) shows a well

  15. Magnetic Properties of 3D Printed Toroids

    NASA Astrophysics Data System (ADS)

    Bollig, Lindsey; Otto, Austin; Hilpisch, Peter; Mowry, Greg; Nelson-Cheeseman, Brittany; Renewable Energy; Alternatives Lab (REAL) Team

    Transformers are ubiquitous in electronics today. Although toroidal geometries perform most efficiently, transformers are traditionally made with rectangular cross-sections due to the lower manufacturing costs. Additive manufacturing techniques (3D printing) can easily achieve toroidal geometries by building up a part through a series of 2D layers. To get strong magnetic properties in a 3D printed transformer, a composite filament is used containing Fe dispersed in a polymer matrix. How the resulting 3D printed toroid responds to a magnetic field depends on two structural factors of the printed 2D layers: fill factor (planar density) and fill pattern. In this work, we investigate how the fill factor and fill pattern affect the magnetic properties of 3D printed toroids. The magnetic properties of the printed toroids are measured by a custom circuit that produces a hysteresis loop for each toroid. Toroids with various fill factors and fill patterns are compared to determine how these two factors can affect the magnetic field the toroid can produce. These 3D printed toroids can be used for numerous applications in order to increase the efficiency of transformers by making it possible for manufacturers to make a toroidal geometry.

  16. Image Appraisal for 2D and 3D Electromagnetic Inversion

    SciTech Connect

    Alumbaugh, D.L.; Newman, G.A.

    1999-01-28

    Linearized methods are presented for appraising image resolution and parameter accuracy in images generated with two and three dimensional non-linear electromagnetic inversion schemes. When direct matrix inversion is employed, the model resolution and posterior model covariance matrices can be directly calculated. A method to examine how the horizontal and vertical resolution varies spatially within the electromagnetic property image is developed by examining the columns of the model resolution matrix. Plotting the square root of the diagonal of the model covariance matrix yields an estimate of how errors in the inversion process such as data noise and incorrect a priori assumptions about the imaged model map into parameter error. This type of image is shown to be useful in analyzing spatial variations in the image sensitivity to the data. A method is analyzed for statistically estimating the model covariance matrix when the conjugate gradient method is employed rather than a direct inversion technique (for example in 3D inversion). A method for calculating individual columns of the model resolution matrix using the conjugate gradient method is also developed. Examples of the image analysis techniques are provided on 2D and 3D synthetic cross well EM data sets, as well as a field data set collected at the Lost Hills Oil Field in Central California.

  17. Improved border sharpness of post-infarct scar by a novel self-navigated free-breathing high-resolution 3D whole-heart inversion recovery magnetic resonance approach.

    PubMed

    Rutz, Tobias; Piccini, Davide; Coppo, Simone; Chaptinel, Jerome; Ginami, Giulia; Vincenti, Gabriella; Stuber, Matthias; Schwitter, Juerg

    2016-12-01

    The border zone of post-infarction myocardial scar as identified by late gadolinium enhancement (LGE) has been identified as a substrate for arrhythmias and consequently, high-resolution 3D scar information is potentially useful for planning of electrophysiological interventions. This study evaluates the performance of a novel high-resolution 3D self-navigated free-breathing inversion recovery magnetic resonance pulse sequence (3D-SN-LGE) vs. conventional 2D breath-hold LGE (2D-LGE) with regard to sharpness of borders (SBorder) of post-infarction scar. Patients with post-infarction scar underwent two magnetic resonance examinations for conventional 2D-LGE and high-resolution 3D-SN-LGE acquisitions (both 15 min after 0.2 mmol/kg Gadobutrol IV) at 1.5T. In the prototype 3D-SN-LGE sequence, each ECG-triggered radial steady-state-free-precession read-out segment is preceded by a non-slice-selective inversion pulse. Scar volume and SBorder were assessed on 2D-LGE and matching reconstructed high-resolution 3D-SN-LGE short-axis slices. In 16 patients (four females, 58 ± 10y) all scars visualized by 2D-LGE could be identified on 3D-SN-LGE (time between 2D-LGE and 3D-SN-LGE 48 ± 53 days). A good agreement of scar volume by 3D-SN-LGE vs. 2D-LGE was found (Bland-Altman: -3.7 ± 3.4 ml, correlation: r = 0.987, p < 0.001) with a small difference in scar volume (20.5 (15.8, 35.2) ml vs. 24.5 (20.0, 41.9)) ml, respectively, p = 0.002] and a good intra- and interobserver variability (1.1 ± 4.1 and -1.1 ± 11.9 ml, respectively). SBorder of border "scar to non-infarcted myocardium" was superior on 3D-SN-LGE vs. 2D-LGE: 0.180 ± 0.044 vs. 0.083 ± 0.038, p < 0.001. Detection and quantification of myocardial scar by 3D-SN-LGE is feasible and accurate in comparison to 2D-LGE. The high spatial resolution of the 3D sequence improves delineation of scar borders.

  18. The novel high-performance 3-D MT inverse solver

    NASA Astrophysics Data System (ADS)

    Kruglyakov, Mikhail; Geraskin, Alexey; Kuvshinov, Alexey

    2016-04-01

    We present novel, robust, scalable, and fast 3-D magnetotelluric (MT) inverse solver. The solver is written in multi-language paradigm to make it as efficient, readable and maintainable as possible. Separation of concerns and single responsibility concepts go through implementation of the solver. As a forward modelling engine a modern scalable solver extrEMe, based on contracting integral equation approach, is used. Iterative gradient-type (quasi-Newton) optimization scheme is invoked to search for (regularized) inverse problem solution, and adjoint source approach is used to calculate efficiently the gradient of the misfit. The inverse solver is able to deal with highly detailed and contrasting models, allows for working (separately or jointly) with any type of MT responses, and supports massive parallelization. Moreover, different parallelization strategies implemented in the code allow optimal usage of available computational resources for a given problem statement. To parameterize an inverse domain the so-called mask parameterization is implemented, which means that one can merge any subset of forward modelling cells in order to account for (usually) irregular distribution of observation sites. We report results of 3-D numerical experiments aimed at analysing the robustness, performance and scalability of the code. In particular, our computational experiments carried out at different platforms ranging from modern laptops to HPC Piz Daint (6th supercomputer in the world) demonstrate practically linear scalability of the code up to thousands of nodes.

  19. 3D-spectral CDIs: a fast alternative to 3D inversion?

    NASA Astrophysics Data System (ADS)

    Macnae, James

    2015-09-01

    Virtually all airborne electromagnetic (AEM) data is interpreted using stitched 1D conductivity sections, derived from constrained inversion or fast but fairly accurate approximations. A small subset of this AEM data recently has been inverted using either block 3D models or thin plates, which processes have limitations in terms of cost and accuracy, and the results are in general strongly biased by the choice of starting models. Recent developments in spectral modelling have allowed fast 3D approximations of the EM response of both vortex induction and current gathering for simple geological target geometries. Fitting these spectral responses to AEM data should be sufficient to accurately locate current systems within the ground, and the behaviour of these local current systems can in theory approximately define a conductivity structure in 3D. This paper describes the results of initial testing of the algorithm in fitting vortex induction in a small target at the Forrestania test range, Western Australia, using results from a versatile time-domain electromagnetic (VTEM)-Max survey.

  20. Computational and methodological developments towards 3D full waveform inversion

    NASA Astrophysics Data System (ADS)

    Etienne, V.; Virieux, J.; Hu, G.; Jia, Y.; Operto, S.

    2010-12-01

    Full waveform inversion (FWI) is one of the most promising techniques for seismic imaging. It relies on a formalism taking into account every piece of information contained in the seismic data as opposed to more classical techniques such as travel time tomography. As a result, FWI is a high resolution imaging process able to reach a spatial accuracy equal to half a wavelength. FWI is based on a local optimization scheme and therefore the main limitation concerns the starting model which has to be closed enough to the real one in order to converge to the global minimum. Another counterpart of FWI is the required computational resources when considering models and frequencies of interest. The task becomes even more tremendous when one tends to perform the inversion using the elastic equation instead of using the acoustic approximation. This is the reason why until recently most studies were limited to 2D cases. In the last few years, due to the increase of the available computational power, FWI has focused a lot of interests and continuous efforts towards inversion of 3D models, leading to remarkable applications up to the continental scale. We investigate the computational burden induced by FWI in 3D elastic media and propose some strategic features leading to the reduction of the numerical cost while providing a great flexibility in the inversion parametrization. First, in order to release the memory requirements, we developed our FWI algorithm in the frequency domain and take benefit of the wave-number redundancy in the seismic data to process a quite reduced number of frequencies. To do so, we extract frequency solutions from time marching techniques which are efficient for 3D structures. Moreover, this frequency approach permits a multi-resolution strategy by proceeding from low to high frequencies: the final model at one frequency is used as the starting model for the next frequency. This procedure overcomes partially the non-linear behavior of the inversion

  1. Inverse Tomo-Lithography for Making Microscopic 3D Parts

    NASA Technical Reports Server (NTRS)

    White, Victor; Wiberg, Dean

    2003-01-01

    According to a proposal, basic x-ray lithography would be extended to incorporate a technique, called inverse tomography, that would enable the fabrication of microscopic three-dimensional (3D) objects. The proposed inverse tomo-lithographic process would make it possible to produce complex shaped, submillimeter-sized parts that would be difficult or impossible to make in any other way. Examples of such shapes or parts include tapered helices, paraboloids with axes of different lengths, and even Archimedean screws that could serve as rotors in microturbines. The proposed inverse tomo-lithographic process would be based partly on a prior microfabrication process known by the German acronym LIGA (lithographie, galvanoformung, abformung, which means lithography, electroforming, molding). In LIGA, one generates a precise, high-aspect ratio pattern by exposing a thick, x-ray-sensitive resist material to an x-ray beam through a mask that contains the pattern. One can electrodeposit metal into the developed resist pattern to form a precise metal part, then dissolve the resist to free the metal. Aspect ratios of 100:1 and patterns into resist thicknesses of several millimeters are possible.

  2. 3D inversion of land-based CSEM data from the Ketzin CO2 storage formation

    NASA Astrophysics Data System (ADS)

    Grayver, Alexander; Streich, Rita; Ritter, Oliver

    2013-04-01

    We present 3D inversion of land controlled-source electromagnetic (CSEM) data collected across the CO2 storage test site at Ketzin, Germany. The CSEM data were generated by injecting currents into the earth at eight locations using a newly developed transmitter equipped with three grounded electrodes. Electric and magnetic field responses were recorded by 39 receivers along a line approximately perpendicular to the main geological trend. The survey aimed at imaging large-scale resistivity structure beyond the near-well region monitored by higher-resolution electrical techniques. Infrastructure present in the survey area, such as pipelines with impressed-current cathodic protection systems, power lines, and wind power plants cause strong noise in the data. The noise is effectively suppressed by adopting statistically robust processing techniques known from passive magnetotellurics. A newly developed Gauss-Newton type parallel distributed inversion scheme, which is based on a direct forward solver and explicitly calculates the full sensitivity matrix, is applied to recover subsurface conductivity images. As 3D inversion is demanding on computer time and memory, we run inversions on parallel distributed machines. We achieve good scalability by distributing computations and memory uniformly among the processes involved. We carry out cumulative sensitivity and resolution analyses for the sparse CSEM acquisition geometry. These studies indicate reasonable spatial coverage along the main survey line. Synthetic studies calculated for the real survey layout and representative conductivity models indicate that the magnetic field components are practically insensitive to resistive structures, whereas the electric field components resolve resistors and conductors similarly well. Because the magnetic field contributes little subsurface information, we concentrate on inverting the electric field, which is also more computer-efficient than inverting all components. We test

  3. A cut-&-paste strategy for the 3-D inversion of helicopter-borne electromagnetic data - II. Combining regional 1-D and local 3-D inversion

    NASA Astrophysics Data System (ADS)

    Ullmann, A.; Scheunert, M.; Afanasjew, M.; Börner, R.-U.; Siemon, B.; Spitzer, K.

    2016-07-01

    As a standard procedure, multi-frequency helicopter-borne electromagnetic (HEM) data are inverted to conductivity-depth models using 1-D inversion methods, which may, however, fail in areas of strong lateral conductivity contrasts (so-called induction anomalies). Such areas require more realistic multi-dimensional modelling. Since the full 3-D inversion of an entire HEM data set is still extremely time consuming, our idea is to combine fast 1-D and accurate but numerically expensive 3-D inversion of HEM data in such a way that the full 3-D inversion is only carried out for those parts of a HEM survey which are affected by induction anomalies. For all other parts, a 1-D inversion method is sufficient. We present a newly developed algorithm for identification, selection, and extraction of induction anomalies in HEM data sets and show how the 3-D inversion model of the anomalous area is re-integrated into the quasi-1-D background. Our proposed method is demonstrated to work properly on a synthetic and a field HEM data set from the Cuxhaven tunnel valley in Germany. We show that our 1-D/3-D approach yields better results compared to 1-D inversions in areas where 3-D effects occur.

  4. Sensitivity study of 3-D modeling for multi-D inversion of surface NMR

    NASA Astrophysics Data System (ADS)

    Warsa, Grandis, Hendra

    2012-06-01

    Geophysical field method of surface nuclear magnetic resonance (SNMR) allows a direct determination of hydrogeological parameters of the subsurface. The amplitude of the SNMR signal is directly linked to the amount of mobile water. The relaxation behaviour of the signal correlates with pore sizes and hydraulic conductivities of an aquifer. For improving capability and reliability of SNMR method we have presented a forward modeling scheme of 3-D water content and decay time structures that can be used for multi-D interpretation. Currently SNMR is carried out mainly with a 1-D working scheme using coinciding loops. For each sounding point using a coincident circular loop antenna, the amplitudes and decay times of the SNMR signal are the product of a three dimensional distribution of the water content and decay time in the subsurface and their sensitivity to the receiver. The antenna is moved at the surface and the SNMR relaxation signal are plotted as a function of the pulse moment and sounding point. The errors might be very large by neglecting the 2-D or even 3-D geometry of the structures which have to be considered in the analysis and inversion in the future. The results show that the 3-D modeling is reliable and flexible to be integrated into the 2-D/3-D inversion scheme for inverting surface NMR data to recover a multi-D distribution of water content and decay time of an aquifer.

  5. 3-D magnetic field calculations for wiggglers using MAGNUS-3D

    SciTech Connect

    Pissanetzky, S.; Tompkins, P.

    1988-01-01

    The recent but steady trend toward increased magnetic and geometric complexity in the design of wigglers and undulators, of which tapered wigglers, hybrid structures, laced electromagnetic wigglers, magnetic cladding, twisters and magic structures are examples, has caused a need for reliable 3-D computer models and a better understanding of the behavior of magnetic systems in three dimensions. The capabilities of the MAGNUS-3D Group of Programs are ideally suited to solve this class of problems and provide insight into 3-D effects. MAGNUS-3D can solve any problem of Magnetostatics involving permanent magnets, linear or nonlinear ferromagnetic materials and electric conductors of any shape in space. The magnetic properties of permanent magnets are described by the complete nonlinear demagnetization curve as provided by the manufacturer, or, at the user's choice, by a simpler approximation involving the coercive force, the residual induction and the direction of magnetization. The ferromagnetic materials are described by a magnetization table and an accurate interpolation relation. An internal library with properties of common industrial steels is available. The conductors are independent of the mesh and are described in terms of conductor elements from an internal library.

  6. 3D and 4D magnetic susceptibility tomography based on complex MR images

    DOEpatents

    Chen, Zikuan; Calhoun, Vince D

    2014-11-11

    Magnetic susceptibility is the physical property for T2*-weighted magnetic resonance imaging (T2*MRI). The invention relates to methods for reconstructing an internal distribution (3D map) of magnetic susceptibility values, .chi. (x,y,z), of an object, from 3D T2*MRI phase images, by using Computed Inverse Magnetic Resonance Imaging (CIMRI) tomography. The CIMRI technique solves the inverse problem of the 3D convolution by executing a 3D Total Variation (TV) regularized iterative convolution scheme, using a split Bregman iteration algorithm. The reconstruction of .chi. (x,y,z) can be designed for low-pass, band-pass, and high-pass features by using a convolution kernel that is modified from the standard dipole kernel. Multiple reconstructions can be implemented in parallel, and averaging the reconstructions can suppress noise. 4D dynamic magnetic susceptibility tomography can be implemented by reconstructing a 3D susceptibility volume from a 3D phase volume by performing 3D CIMRI magnetic susceptibility tomography at each snapshot time.

  7. Direct inversion of digital 3D Fraunhofer holography maps.

    PubMed

    Podorov, Sergei G; Förster, Eckhart

    2016-01-20

    Differential Fourier holography (DFH) gives an exact mathematical solution of the inverse problem of diffraction in the Fraunhofer regime. After the first publication [Opt. Express15, 9954 (2007)], DFH was successfully applied in many experiments to obtain amplitude and phase information about two-dimensional images. In this paper, we demonstrate numerically the possibility to apply DFH also for investigation of unknown three-dimensional objects. The first simulation is made for a double-spiral structure plus a line as a reference object.

  8. 3D parallel inversion of time-domain airborne EM data

    NASA Astrophysics Data System (ADS)

    Liu, Yun-He; Yin, Chang-Chun; Ren, Xiu-Yan; Qiu, Chang-Kai

    2016-12-01

    To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM "footprint" concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.

  9. Structure of the Rambler Rhyolite, Baie Verte Peninsula, Newfoundland: Inversions using UBC-GIF Grav3D and Mag3D

    NASA Astrophysics Data System (ADS)

    Spicer, B.; Morris, B.; Ugalde, H.

    2011-09-01

    Hosted within the Pacquet Harbour Group (PHG) on the Baie Verte Peninsula of north-central Newfoundland, the Rambler rhyolite is a 487 Ma unit of felsic tuffs, flows and subvolcanic intrusive rocks. The PHG has been affected by multiple phases of deformation with the youngest D4 deformation event producing broad northeast plunging upright cross folds in the Rambler rhyolite. Fold culminations on the upper bounding surface of the rhyolite host Cu +/- Au volcanogenic massive sulfide deposits (e.g. Rambler and Ming mines). Geophysical inversions of recently acquired high resolution gravity and magnetic data have been implemented to determine the extent of the fold axis (dome) at depth. To direct the outcome of the inversion process towards a more geologically reasonable solution this study outlines a procedure which permits the inclusion of known geological and geophysical constraints into the input (reference) model for inversion using the MAG3D and GRAV3D algorithms provided by the University of British Columbia Geophysical Inversion Facility. Reference model constraints included surficial geological contacts as defined by aeromagnetic data, and subsurface distribution of physical property variations from a series of drill-hole logs. The output (computed) model images the surface of the rhyolite dome as dipping roughly 40° to the northeast as a series of voxels with density values ranging from 2.71 to 2.75 g/cm3. While previously published ore deposit models parallel this structure in the near surface, results from these inversions suggest deeper exploration may be favorable. Magnetic inversion modeling has not provided any insight into dome morphology however it outlines the distribution of gabbroic dykes surrounding the dome.

  10. 3D print of polymer bonded rare-earth magnets, and 3D magnetic field scanning with an end-user 3D printer

    NASA Astrophysics Data System (ADS)

    Huber, C.; Abert, C.; Bruckner, F.; Groenefeld, M.; Muthsam, O.; Schuschnigg, S.; Sirak, K.; Thanhoffer, R.; Teliban, I.; Vogler, C.; Windl, R.; Suess, D.

    2016-10-01

    3D print is a recently developed technique, for single-unit production, and for structures that have been impossible to build previously. The current work presents a method to 3D print polymer bonded isotropic hard magnets with a low-cost, end-user 3D printer. Commercially available isotropic NdFeB powder inside a PA11 matrix is characterized, and prepared for the printing process. An example of a printed magnet with a complex shape that was designed to generate a specific stray field is presented, and compared with finite element simulation solving the macroscopic Maxwell equations. For magnetic characterization, and comparing 3D printed structures with injection molded parts, hysteresis measurements are performed. To measure the stray field outside the magnet, the printer is upgraded to a 3D magnetic flux density measurement system. To skip an elaborate adjusting of the sensor, a simulation is used to calibrate the angles, sensitivity, and the offset of the sensor. With this setup, a measurement resolution of 0.05 mm along the z-axes is achievable. The effectiveness of our calibration method is shown. With our setup, we are able to print polymer bonded magnetic systems with the freedom of having a specific complex shape with locally tailored magnetic properties. The 3D scanning setup is easy to mount, and with our calibration method we are able to get accurate measuring results of the stray field.

  11. Contribution of 3D inversion of Electrical Resistivity Tomography data applied to volcanic structures

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2016-04-01

    The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out

  12. Obtaining valid geologic models from 3-D resistivity inversion of magnetotelluric data at Pahute Mesa, Nevada

    USGS Publications Warehouse

    Rodriguez, Brian D.; Sweetkind, Donald S.

    2015-01-01

    The 3-D inversion was generally able to reproduce the gross resistivity structure of the “known” model, but the simulated conductive volcanic composite unit horizons were often too shallow when compared to the “known” model. Additionally, the chosen computation parameters such as station spacing appear to have resulted in computational artifacts that are difficult to interpret but could potentially be removed with further refinements of the 3-D resistivity inversion modeling technique.

  13. Reducing Non-Uniqueness in Satellite Gravity Inversion using 3D Object Oriented Image Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Fadel, I.; van der Meijde, M.; Kerle, N.

    2013-12-01

    Non-uniqueness of satellite gravity interpretation has been usually reduced by using a priori information from various sources, e.g. seismic tomography models. The reduction in non-uniqueness has been based on velocity-density conversion formulas or user interpretation for 3D subsurface structures (objects) in seismic tomography models. However, these processes introduce additional uncertainty through the conversion relations due to the dependency on the other physical parameters such as temperature and pressure, or through the bias in the interpretation due to user choices and experience. In this research, a new methodology is introduced to extract the 3D subsurface structures from 3D geophysical data using a state-of-art 3D Object Oriented Image Analysis (OOA) technique. 3D OOA is tested using a set of synthetic models that simulate the real situation in the study area of this research. Then, 3D OOA is used to extract 3D subsurface objects from a real 3D seismic tomography model. The extracted 3D objects are used to reconstruct a forward model and its response is compared with the measured satellite gravity. Finally, the result of the forward modelling, based on the extracted 3D objects, is used to constrain the inversion process of satellite gravity data. Through this work, a new object-based approach is introduced to interpret and extract the 3D subsurface objects from 3D geophysical data. This can be used to constrain modelling and inversion of potential field data using the extracted 3D subsurface structures from other methods. In summary, a new approach is introduced to constrain inversion of satellite gravity measurements and enhance interpretation capabilities.

  14. Fast 3D Focusing Inversion of Gravity Data Using Reweighted Regularized Lanczos Bidiagonalization Method

    NASA Astrophysics Data System (ADS)

    Rezaie, Mohammad; Moradzadeh, Ali; Kalate, Ali Nejati; Aghajani, Hamid

    2017-01-01

    Inversion of gravity data is one of the important steps in the interpretation of practical data. One of the most interesting geological frameworks for gravity data inversion is the detection of sharp boundaries between orebody and host rocks. The focusing inversion is able to reconstruct a sharp image of the geological target. This technique can be efficiently applied for the quantitative interpretation of gravity data. In this study, a new reweighted regularized method for the 3D focusing inversion technique based on Lanczos bidiagonalization method is developed. The inversion results of synthetic data show that the new method is faster than common reweighted regularized conjugate gradient method to produce an acceptable solution for focusing inverse problem. The new developed inversion scheme is also applied for inversion of the gravity data collected over the San Nicolas Cu-Zn orebody in Zacatecas State, Mexico. The inversion results indicate a remarkable correlation with the true structure of the orebody that is achieved from drilling data.

  15. 3D Propagation and Geoacoustic Inversion Studies in the Mid-Atlantic Bight

    DTIC Science & Technology

    2016-06-07

    3D Propagation and Geoacoustic Inversion Studies in the Mid-Atlantic Bight Kevin B. Smith Code PH/Sk, Department of Physics Naval Postgraduate...properties and measured transmission loss. Results from this analysis will be considered in the context of geoacoustic inversions . OBJECTIVES To...bathymetric features and ocean fronts near the shelf break of the mid-Atlantic Bight, and use of various data for geoacoutic inversion studies. The results

  16. Multimaterial magnetically assisted 3D printing of composite materials

    PubMed Central

    Kokkinis, Dimitri; Schaffner, Manuel; Studart, André R.

    2015-01-01

    3D printing has become commonplace for the manufacturing of objects with unusual geometries. Recent developments that enabled printing of multiple materials indicate that the technology can potentially offer a much wider design space beyond unusual shaping. Here we show that a new dimension in this design space can be exploited through the control of the orientation of anisotropic particles used as building blocks during a direct ink-writing process. Particle orientation control is demonstrated by applying low magnetic fields on deposited inks pre-loaded with magnetized stiff platelets. Multimaterial dispensers and a two-component mixing unit provide additional control over the local composition of the printed material. The five-dimensional design space covered by the proposed multimaterial magnetically assisted 3D printing platform (MM-3D printing) opens the way towards the manufacturing of functional heterogeneous materials with exquisite microstructural features thus far only accessible by biological materials grown in nature. PMID:26494528

  17. Multimaterial magnetically assisted 3D printing of composite materials

    NASA Astrophysics Data System (ADS)

    Kokkinis, Dimitri; Schaffner, Manuel; Studart, André R.

    2015-10-01

    3D printing has become commonplace for the manufacturing of objects with unusual geometries. Recent developments that enabled printing of multiple materials indicate that the technology can potentially offer a much wider design space beyond unusual shaping. Here we show that a new dimension in this design space can be exploited through the control of the orientation of anisotropic particles used as building blocks during a direct ink-writing process. Particle orientation control is demonstrated by applying low magnetic fields on deposited inks pre-loaded with magnetized stiff platelets. Multimaterial dispensers and a two-component mixing unit provide additional control over the local composition of the printed material. The five-dimensional design space covered by the proposed multimaterial magnetically assisted 3D printing platform (MM-3D printing) opens the way towards the manufacturing of functional heterogeneous materials with exquisite microstructural features thus far only accessible by biological materials grown in nature.

  18. Free-Standing Magnetic Nanopillars for 3D Nanomagnet Logic

    PubMed Central

    2014-01-01

    Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-controlled nanomagnets to enable digital processing. Currently, conventional resist-based lithographic processes limit the design of NML circuitry to planar nanostructures with homogeneous thicknesses. Here, we demonstrate the focused electron beam induced deposition of Fe-based nanomaterial for magnetic in-plane nanowires and out-of-plane nanopillars. Three-dimensional (3D) NML was achieved based on the magnetic coupling between nanowires and nanopillars in a 3D array. Additionally, the same Fe-based nanomaterial was used to produce tilt-corrected high-aspect-ratio probes for the accurate magnetic force microscopy (MFM) analysis of the fabricated 3D NML gate arrays. The interpretation of the MFM measurements was supported by magnetic simulations using the Object Oriented MicroMagnetic Framework. Introducing vertical out-of-plane nanopillars not only increases the packing density of 3D NML but also introduces an extra magnetic degree of freedom, offering a new approach to input/output and processing functionalities in nanomagnetic computing. PMID:25296008

  19. Semiautomatic approaches to account for 3-D distortion of the electric field from local, near-surface structures in 3-D resistivity inversions of 3-D regional magnetotelluric data

    USGS Publications Warehouse

    Rodriguez, Brian D.

    2017-03-31

    This report summarizes the results of three-dimensional (3-D) resistivity inversion simulations that were performed to account for local 3-D distortion of the electric field in the presence of 3-D regional structure, without any a priori information on the actual 3-D distribution of the known subsurface geology. The methodology used a 3-D geologic model to create a 3-D resistivity forward (“known”) model that depicted the subsurface resistivity structure expected for the input geologic configuration. The calculated magnetotelluric response of the modeled resistivity structure was assumed to represent observed magnetotelluric data and was subsequently used as input into a 3-D resistivity inverse model that used an iterative 3-D algorithm to estimate 3-D distortions without any a priori geologic information. A publicly available inversion code, WSINV3DMT, was used for all of the simulated inversions, initially using the default parameters, and subsequently using adjusted inversion parameters. A semiautomatic approach of accounting for the static shift using various selections of the highest frequencies and initial models was also tested. The resulting 3-D resistivity inversion simulation was compared to the “known” model and the results evaluated. The inversion approach that produced the lowest misfit to the various local 3-D distortions was an inversion that employed an initial model volume resistivity that was nearest to the maximum resistivities in the near-surface layer.

  20. Solution of 3D inverse scattering problems by combined inverse equivalent current and finite element methods

    SciTech Connect

    Kılıç, Emre Eibert, Thomas F.

    2015-05-01

    An approach combining boundary integral and finite element methods is introduced for the solution of three-dimensional inverse electromagnetic medium scattering problems. Based on the equivalence principle, unknown equivalent electric and magnetic surface current densities on a closed surface are utilized to decompose the inverse medium problem into two parts: a linear radiation problem and a nonlinear cavity problem. The first problem is formulated by a boundary integral equation, the computational burden of which is reduced by employing the multilevel fast multipole method (MLFMM). Reconstructed Cauchy data on the surface allows the utilization of the Lorentz reciprocity and the Poynting's theorems. Exploiting these theorems, the noise level and an initial guess are estimated for the cavity problem. Moreover, it is possible to determine whether the material is lossy or not. In the second problem, the estimated surface currents form inhomogeneous boundary conditions of the cavity problem. The cavity problem is formulated by the finite element technique and solved iteratively by the Gauss–Newton method to reconstruct the properties of the object. Regularization for both the first and the second problems is achieved by a Krylov subspace method. The proposed method is tested against both synthetic and experimental data and promising reconstruction results are obtained.

  1. 3-D inversion of synthetic marine magnetotelluric data: resolution and sensitivity

    NASA Astrophysics Data System (ADS)

    Tada, N.; Baba, K.; Siripunvaraporn, W.; Uyeshima, M.; Utada, H.

    2010-12-01

    In recent years, seafloor magnetotelluric (MT) observation is carried out by using an increasing number of ocean bottom electromagnetometers (OBEMs) not only along a line but also in 2-D array. Thus, imaging electrical conductivity structures under the seafloor in 3-D is now feasible. A 3-D approach is indispensable especially for marine MT data, because the electric and magnetic fields observed at the seafloor are heavily distorted by the rugged seafloor topography and the distribution of land and sea which are generally 3-D. It is very important to incorporate the topography in a 3-D model for an accurate estimation of the conductivity structure beneath seafloor that is generally more resistive than seawater by several orders of magnitude. WSINV3DMT (Siripunvaraporn et al., 2005) is one of 3-D inversion codes that are now of practical use, but the original WSINV3DMT is not applicable to marine MT data because of two reasons. 1) MT responses are calculated only at the boundary corresponding to the Earth surface. 2) We have to use fine mesh design because an observation site must locate exactly at the center of the top surface of a block, which needs large memory that even a highest performance computer can not handle. We propose an extended version of the WSINV3DMT by solving the two problems shown above so that it can be applied to the marine MT data. The extended version of the WSINV3DMT is tested using synthetic models including a 3-D anomaly, seawater and topographic variation. Here shown is an example of a checkerboard test by using a model in which 10 ohm-m and 100 ohm-m blocks are put alternately in both horizontal and vertical directions. The model is composed of 5 blocks in horizontal directions and of 4 blocks in vertical direction with a background of a 31.6 ohm-m half-space below actual topography. The calculation area in the inversion is 7440 × 7440 × 1008 km, and is discretized at 35 blocks in the x and y directions, and 69 blocks in the z

  2. 3-D Inversion of MT Data for Imaging Deformation Fronts in NW Poland

    NASA Astrophysics Data System (ADS)

    Ślęzak, Katarzyna; Jóźwiak, Waldemar; Nowożyński, Krzysztof; Brasse, Heinrich

    2016-07-01

    The Pomerania region (northwest part of Poland) occupies a significant position, where the largest European tectonic boundary is situated. This is the area of the contact between the East European Craton (EEC) and the Paleozoic Platform (PP) and it is known as the Trans-European Suture Zone (TESZ). The TESZ was formed during Paleozoic time as a consequence of the collision of several crustal units and it extends from the Black Sea in the southeast to the British Isles in the northwest. It is a region of key importance for our understanding of the tectonic history of Europe. Previous magnetotelluric (MT) results, based on 2-D inverse modeling, show that the contact zone is of lithospheric discontinuity character and there are distinct differences in geoelectric structures between the Precambrian EEC, transitional zone (TESZ), and the younger PP. The presence of a significant conductor at mid and lower crustal depths was also shown. Thus, the main aim of the research presented here was to obtain detailed, 3-D images of electrical conductivity in the crust and upper mantle and its regional distribution below the TESZ in the northwest part of Poland. To accomplish this task we applied the latest 3-D inversion codes, which allowed us to get more realistic model geometries. Additionally, to confirm and complement the study, the Horizontal Magnetic Tensor (HMT) analysis was realized. This method gives us an opportunity to efficiently locate the position of well-conducting structures. As a result we obtain a clearer, three-dimensional model of conductivity distribution, where highly conductive rock complexes appear which we tentatively connected to deformation fronts.

  3. Seismic source inversion using Green's reciprocity and a 3-D structural model for the Japanese Islands

    NASA Astrophysics Data System (ADS)

    Simutė, S.; Fichtner, A.

    2015-12-01

    We present a feasibility study for seismic source inversions using a 3-D velocity model for the Japanese Islands. The approach involves numerically calculating 3-D Green's tensors, which is made efficient by exploiting Green's reciprocity. The rationale for 3-D seismic source inversion has several aspects. For structurally complex regions, such as the Japan area, it is necessary to account for 3-D Earth heterogeneities to prevent unknown structure polluting source solutions. In addition, earthquake source characterisation can serve as a means to delineate existing faults. Source parameters obtained for more realistic Earth models can then facilitate improvements in seismic tomography and early warning systems, which are particularly important for seismically active areas, such as Japan. We have created a database of numerically computed 3-D Green's reciprocals for a 40°× 40°× 600 km size area around the Japanese Archipelago for >150 broadband stations. For this we used a regional 3-D velocity model, recently obtained from full waveform inversion. The model includes attenuation and radial anisotropy and explains seismic waveform data for periods between 10 - 80 s generally well. The aim is to perform source inversions using the database of 3-D Green's tensors. As preliminary steps, we present initial concepts to address issues that are at the basis of our approach. We first investigate to which extent Green's reciprocity works in a discrete domain. Considering substantial amounts of computed Green's tensors we address storage requirements and file formatting. We discuss the importance of the initial source model, as an intelligent choice can substantially reduce the search volume. Possibilities to perform a Bayesian inversion and ways to move to finite source inversion are also explored.

  4. Spontaneous mirror-symmetry breaking induces inverse energy cascade in 3D active fluids

    PubMed Central

    Słomka, Jonasz; Dunkel, Jörn

    2017-01-01

    Classical turbulence theory assumes that energy transport in a 3D turbulent flow proceeds through a Richardson cascade whereby larger vortices successively decay into smaller ones. By contrast, an additional inverse cascade characterized by vortex growth exists in 2D fluids and gases, with profound implications for meteorological flows and fluid mixing. The possibility of a helicity-driven inverse cascade in 3D fluids had been rejected in the 1970s based on equilibrium-thermodynamic arguments. Recently, however, it was proposed that certain symmetry-breaking processes could potentially trigger a 3D inverse cascade, but no physical system exhibiting this phenomenon has been identified to date. Here, we present analytical and numerical evidence for the existence of an inverse energy cascade in an experimentally validated 3D active fluid model, describing microbial suspension flows that spontaneously break mirror symmetry. We show analytically that self-organized scale selection, a generic feature of many biological and engineered nonequilibrium fluids, can generate parity-violating Beltrami flows. Our simulations further demonstrate how active scale selection controls mirror-symmetry breaking and the emergence of a 3D inverse cascade. PMID:28193853

  5. Magnetism In 3d Transition Metals at High Pressures

    SciTech Connect

    Iota, V

    2006-02-09

    This research project examined the changes in electronic and magnetic properties of transition metals and oxides under applied pressures, focusing on complex relationship between magnetism and phase stability in these correlated electron systems. As part of this LDRD project, we developed new measurement techniques and adapted synchrotron-based electronic and magnetic measurements for use in the diamond anvil cell. We have performed state-of-the-art X-ray spectroscopy experiments at the dedicated high-pressure beamline HP-CAT (Sector 16 Advanced Photon Source, Argonne National Laboratory), maintained in collaboration with of University of Nevada, Las Vegas and Geophysical Laboratory of The Carnegie Institution of Washington. Using these advanced measurements, we determined the evolution of the magnetic order in the ferromagnetic 3d transition metals (Fe, Co and Ni) under pressure, and found that at high densities, 3d band broadening results in diminished long range magnetic coupling. Our experiments have allowed us to paint a unified picture of the effects of pressure on the evolution of magnetic spin in 3d electron systems. The technical and scientific advances made during this LDRD project have been reported at a number of scientific meetings and conferences, and have been submitted for publication in technical journals. Both the technical advances and the physical understanding of correlated systems derived from this LDRD are being applied to research on the 4f and 5f electron systems under pressure.

  6. Voltage controlled magnetism in 3d transitional metals

    NASA Astrophysics Data System (ADS)

    Wang, Weigang

    2015-03-01

    Despite having attracted much attention in multiferroic materials and diluted magnetic semiconductors, the impact of an electric field on the magnetic properties remains largely unknown in 3d transitional ferromagnets (FMs) until recent years. A great deal of effort has been focused on the voltage-controlled magnetic anisotropy (VCMA) effect where the modulation of anisotropy field is understood by the change of electron density among different d orbitals of FMs in the presence of an electric field. Here we demonstrate another approach to alter the magnetism by electrically controlling the oxidation state of the 3d FM at the FM/oxide interface. The thin FM film sandwiched between a heavy metal layer and a gate oxide can be reversibly changed from an optimally-oxidized state with a strong perpendicular magnetic anisotropy to a metallic state with an in-plane magnetic anisotropy, or to a fully-oxidized state with nearly zero magnetization, depending on the polarity and time duration of the applied electric fields. This is a voltage controlled magnetism (VCM) effect, where both the saturation magnetization and anisotropy field of the 3d FM layer can be simultaneously controlled by voltage in a non-volatile fashion. We will also discuss the impact of this VCM effect on magnetic tunnel junctions and spin Hall switching experiments. This work, in collaboration with C. Bi, Y.H. Liu, T. Newhouse-Illige, M. Xu, M. Rosales, J.W. Freeland, O. Mryasov, S. Zhang, and S.G.E. te Velthuis, was supported in part by NSF (ECCS-1310338) and by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  7. 3D Airborne Electromagnetic Inversion: A case study from the Musgrave Region, South Australia

    NASA Astrophysics Data System (ADS)

    Cox, L. H.; Wilson, G. A.; Zhdanov, M. S.; Sunwall, D. A.

    2012-12-01

    Geophysicists know and accept that geology is inherently 3D, and is resultant from complex, overlapping processes related to genesis, metamorphism, deformation, alteration, weathering, and/or hydrogeology. Yet, the geophysics community has long relied on qualitative analysis, conductivity depth imaging (CDIs), 1D inversion, and/or plate modeling. There are many reasons for this deficiency, not the least of which has been the lack of capacity for historic 3D AEM inversion algorithms to invert entire surveys so as to practically affect exploration decisions. Our recent introduction of a moving sensitivity domain (footprint) methodology has been a paradigm shift in AEM interpretation. The basis of this method is that one needs only to calculate the responses and sensitivities for that part of the 3D earth model that is within the AEM system's sensitivity domain (footprint), and then superimpose all sensitivity domains into a single, sparse sensitivity matrix for the entire 3D earth model which is then updated in a regularized inversion scheme. This has made it practical to rigorously invert entire surveys with thousands of line kilometers of AEM data to mega-cell 3D models in hours using multi-processor workstations. Since 2010, over eighty individual projects have been completed for Aerodat, AEROTEM, DIGHEM, GEOTEM, HELITEM, HoisTEM, MEGATEM, RepTEM, RESOLVE, SkyTEM, SPECTREM, TEMPEST, and VTEM data from Australia, Brazil, Canada, Finland, Ghana, Peru, Tanzania, the US, and Zambia. Examples of 3D AEM inversion have been published for a variety of applications, including mineral exploration, oil sands exploration, salinity, permafrost, and bathymetry mapping. In this paper, we present a comparison of 3D inversions for SkyTEM, SPECTREM, TEMPET and VTEM data acquired over the same area in the Musgrave region of South Australia for exploration under cover.

  8. 3D Modeling of Iran and Surrounding Areas From Simultaneous Inversion of Multiple Geophysical Datasets

    DTIC Science & Technology

    2010-09-01

    lithosphere elude us. We have been able to surmise that geologic variations here are substantial, and we know that they frustrate attempts to use robust...concepts are summarized conceptually in Figure 2, which shows the regions of the lithosphere most sensitive to the different data that we employ. To...construct an approximate 3D model of the lithosphere , we use a hybrid 1D-3D inversion. In many tomography analyses, dispersion variations are

  9. High-resolution imaging and inversion of 3D GPR data for layered media

    NASA Astrophysics Data System (ADS)

    Slob, Evert

    2013-04-01

    Ground penetrating radar is increasingly being used to provide quantitative information of layered structures. For application in civil engineering these can be roads, highway pavements, airport runways, bridges, tunnels, or buildings. Monitoring is important for the management and safety of these structures. Standard imaging uses a modeled wavefield extrapolator to image the data and the quality of the image depends heavily on the quality of the modeled extrapolator. Usually, data inversion is implemented by minimizing a cost function involving the measured data and the modeled data. The model is modified such that data computed from the model fits to the measured data. The data itself is not used, except as a measure of the model data fit. A recently developed alternative method is to use results from inverse scattering theory to first construct an image while all multiple reflections are simultaneously eliminated from the data. This image can be constructed from surface reflection data if the data allows separating the subsurface reflection response from the down going emitted field. For 3D waves in a layered medium this requires knowledge of all horizontal electric and magnetic field components. If the data is properly sampled the solution is unique. In layered media the plane wave decomposition allows computing the image for each angle of incidence separately as a function of image time that is equal to the one-way intercept time. Once the image is constructed for all available angles of incidence a simple matrix inversion leads to the desired electric permittivity and magnetic permeability values in each layer. Finally these values provide interval velocities that can be used to convert image time to depth and the inverse problem is solved. The theory requires infinite bandwidth frequency domain data, which is equivalent to measuring the true impulse response. This is not possible in practice and numerical results show that data with finite bandwidths can be

  10. Inverse cascades sustained by the transfer rate of angular momentum in a 3D turbulent flow.

    PubMed

    López-Caballero, Miguel; Burguete, Javier

    2013-03-22

    The existence of energy cascades as signatures of conserved magnitudes is one of the universal characteristics of turbulent flows. In homogeneous 3D turbulence, the energy conservation produces a direct cascade from large to small scales, although in 2D, it produces an inverse cascade pointing towards small wave numbers. In this Letter, we present the first evidence of an inverse cascade in a fully developed 3D experimental turbulent flow where the conserved magnitude is the angular momentum. Two counterrotating flows collide in a central region where very large fluctuations are produced, generating a turbulent drag that transfers the external torque between different fluid layers.

  11. Inverse Cascades Sustained by the Transfer Rate of Angular Momentum in a 3D Turbulent Flow

    NASA Astrophysics Data System (ADS)

    López-Caballero, Miguel; Burguete, Javier

    2013-03-01

    The existence of energy cascades as signatures of conserved magnitudes is one of the universal characteristics of turbulent flows. In homogeneous 3D turbulence, the energy conservation produces a direct cascade from large to small scales, although in 2D, it produces an inverse cascade pointing towards small wave numbers. In this Letter, we present the first evidence of an inverse cascade in a fully developed 3D experimental turbulent flow where the conserved magnitude is the angular momentum. Two counterrotating flows collide in a central region where very large fluctuations are produced, generating a turbulent drag that transfers the external torque between different fluid layers.

  12. Kinetic shielding of magnetic islands in 3-D equilibria

    NASA Astrophysics Data System (ADS)

    Hegna, C. C.

    2010-11-01

    Kinetic theory is employed to calculate corrections to analytic predictions of saturated magnetic islands due to pressure gradients in 3-D magnetic configurations. The theory calculates the dominant trapped particle response to 3-D field induced net bounce averaged radial drifts. The associated kinetic response describes plasma currents that flow within magnetic surfaces. In general, these currents have a component that resonates with the helical angle of the magnetic island and affect saturated island sizes through the parallel currents generated to satisfy quasineutrality. The resulting kinetic response generally opposes the effects of singular Pfirsch-Schlüter currents that arise at the rational surfaces of general 3-D MHD equilibria. Accounting for both the MHD and kinetic responses, self-consistent magnetic island widths are calculated using Ampere's law. The kinetic effect is largest at lowest collisionality suggesting high-β stellarators are more resilient to retaining flux surface integrity at high-temperatures than predictions from conventional MHD based theory would imply.

  13. Laplace-domain waveform modeling and inversion for the 3D acoustic-elastic coupled media

    NASA Astrophysics Data System (ADS)

    Shin, Jungkyun; Shin, Changsoo; Calandra, Henri

    2016-06-01

    Laplace-domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-domain waveform inversion over conventional frequency-domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-domain waveform modeling and inversion algorithm for 3D acoustic-elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.

  14. Development of direct-inverse 3-D methods for applied aerodynamic design and analysis

    NASA Technical Reports Server (NTRS)

    Carlson, Leland A.

    1988-01-01

    Several inverse methods have been compared and initial results indicate that differences in results are primarily due to coordinate systems and fuselage representations and not to design procedures. Further, results from a direct-inverse method that includes 3-D wing boundary layer effects, wake curvature, and wake displacement are presented. These results show that boundary layer displacements must be included in the design process for accurate results.

  15. 3-D Display Of Magnetic Resonance Imaging Of The Spine

    NASA Astrophysics Data System (ADS)

    Nelson, Alan C.; Kim, Yongmin; Haralick, Robert M.; Anderson, Paul A.; Johnson, Roger H.; DeSoto, Larry A.

    1988-06-01

    The original data is produced through standard magnetic resonance imaging (MRI) procedures with a surface coil applied to the lower back of a normal human subject. The 3-D spine image data consists of twenty-six contiguous slices with 256 x 256 pixels per slice. Two methods for visualization of the 3-D spine are explored. One method utilizes a verifocal mirror system which creates a true 3-D virtual picture of the object. Another method uses a standard high resolution monitor to simultaneously show the three orthogonal sections which intersect at any user-selected point within the object volume. We discuss the application of these systems in assessment of low back pain.

  16. Particle acceleration at 3D reconnecting magnetic separators

    NASA Astrophysics Data System (ADS)

    Threlfall, James; Neukirch, Thomas; Parnell, Clare; Stevenson, Julie

    2015-04-01

    We present results of test particle orbit calculations in three different environments which model separator reconnection in three dimensions. The test particle (electron and proton) orbits are calculated using the relativistic guiding centre approximation. We investigate test particle orbits in a time-dependent (analytical) electro-magnetic field configuration [detailed in Threlfall et al. (A&A, in press); arXiv:1410.6465]. These results are also compared with orbits based upon large-scale 3D MHD simulations of both a single reconnecting magnetic separator and an observationally driven 3D model of a solar active region which contains several topological features of interest, including separators. We discuss how the test-particle orbits and the energy gain depend on the initial conditions, and how observations (for example, of solar flares) may be used to constrain model parameters.

  17. Research on Joint Parameter Inversion for an Integrated Underground Displacement 3D Measuring Sensor

    PubMed Central

    Shentu, Nanying; Qiu, Guohua; Li, Qing; Tong, Renyuan; Shentu, Nankai; Wang, Yanjie

    2015-01-01

    Underground displacement monitoring is a key means to monitor and evaluate geological disasters and geotechnical projects. There exist few practical instruments able to monitor subsurface horizontal and vertical displacements simultaneously due to monitoring invisibility and complexity. A novel underground displacement 3D measuring sensor had been proposed in our previous studies, and great efforts have been taken in the basic theoretical research of underground displacement sensing and measuring characteristics by virtue of modeling, simulation and experiments. This paper presents an innovative underground displacement joint inversion method by mixing a specific forward modeling approach with an approximate optimization inversion procedure. It can realize a joint inversion of underground horizontal displacement and vertical displacement for the proposed 3D sensor. Comparative studies have been conducted between the measured and inversed parameters of underground horizontal and vertical displacements under a variety of experimental and inverse conditions. The results showed that when experimentally measured horizontal displacements and vertical displacements are both varied within 0 ~ 30 mm, horizontal displacement and vertical displacement inversion discrepancies are generally less than 3 mm and 1 mm, respectively, under three kinds of simulated underground displacement monitoring circumstances. This implies that our proposed underground displacement joint inversion method is robust and efficient to predict the measuring values of underground horizontal and vertical displacements for the proposed sensor. PMID:25871714

  18. Chern insulators without band inversion in Mo S2 monolayers with 3 d adatoms

    NASA Astrophysics Data System (ADS)

    Wei, Xinyuan; Zhao, Bao; Zhang, Jiayong; Xue, Yang; Li, Yun; Yang, Zhongqin

    2017-02-01

    Electronic and topological properties of Mo S2 monolayers endowed with 3 d transition metal (TM) adatoms (V-Fe) are explored by using ab initio methods and k .p models. Without the consideration of the Hubbard U interaction, the V, Cr, and Fe adatoms tend to locate on the top of the Mo atoms, while the most stable site for the Mn atom is at the hollow position of the Mo-S hexagon. After the Hubbard U is applied, the most stable sites of all the systems become the top of the Mo atoms. Chern insulators without band inversion are achieved in these systems. The V and Fe adsorption systems are the best candidates to produce the topological states. The k .p model calculations indicate that these topological states are determined by the TM magnetism, the C3 v crystal field from the Mo S2 substrate, and the TM atomic spin-orbit coupling (SOC). The special two-meron pseudospin texture is found to contribute to the topology. The apparent difference between the Berry curvatures for the V and Fe adsorption systems is also explored. Our results widen the understanding of the Chern insulators and are helpful for the applications of the Mo S2 monolayers in the future electronics and spintronics.

  19. Note: 3D printed spheroid for uniform magnetic field generation

    NASA Astrophysics Data System (ADS)

    Öztürk, Y.; Aktaş, B.

    2016-10-01

    This article is focused on a novel and practical production method for a uniform magnetic field generator. The method involves building of a surface coil template using a desktop 3D printer and winding of a conducting wire onto the structure using surface grooves as a guide. Groove pattern was based on the parametric spheroidal helical coil formula. The coil was driven by a current source and the magnetic field inside was measured using a Hall probe placed into the holes on the printed structure. The measurements are found to be in good agreement with our finite element analysis results and indicate a fairly uniform field inside.

  20. 3-D Inverse Teleseismic Scattered Wave Imaging using the Kirchhoff Approximation

    NASA Astrophysics Data System (ADS)

    Liu, K.; Levander, A.

    2012-04-01

    We have developed a 3-D teleseismic imaging technique for scattered elastic wavefields using the Kirchhoff approximation. Kirchhoff migration/inversion have been well developed in exploration seismology within the inverse scattering framework (e.g. Miller et al., 1987; Beylkin and Burridge, 1990) to image subsurface structure that generates secondary wavefields caused by localized heterogeneities. Application of this method in global seismology has been largely limited to 2-D images made with 1-D reference models due to high computational cost and the lack of adequately dense receiver arrays (Bostock, 2002, Poppeliers and Pavlis, 2003; Frederiksen and Revenaugh, 2004; Cao et al., 2010). The deployment of the USArray Transportable and Flexible arrays in the United States and dense array recordings in other countries motivate developing teleseismic scattered wavefield imaging with the Kirchhoff approximation for 3-D velocity models for both scalar and vector wavefields to improve upper mantle imaging. Following Bostock's development of the 2-D problem (2002), we derive the 3-D P-to-S scattering inversion formula by phrasing the inverse problem in terms of the generalized Radon transform (GRT) and singular functions of discontinuity surfaces. In the forward scattering modeling, we extend the method to utilize a 3-D migration velocity model by calculating 3-D finite-difference traveltimes, backprojected from the receivers using an eikonal solver. To demonstrate the relative accuracy of the inversion, we examine several synthetic cases with a variety of discontinuity surfaces (sinuous, dipping, dome- and crater-shaped discontinuity interfaces, point scatterers, etc.). The Kirchhoff GRT imaging can successfully recover the shapes of these structures very well. We compare our Kirchhoff approximation imaging with the Born-approximate results, as well as the common-conversion point (CCP) stacked receiver function imaging for the various synthetic cases, and show a field

  1. Magnetism in a graphene-4 f -3 d hybrid system

    NASA Astrophysics Data System (ADS)

    Huttmann, Felix; Klar, David; Atodiresei, Nicolae; Schmitz-Antoniak, Carolin; Smekhova, Alevtina; Martínez-Galera, Antonio J.; Caciuc, Vasile; Bihlmayer, Gustav; Blügel, Stefan; Michely, Thomas; Wende, Heiko

    2017-02-01

    We create an interface of graphene with a metallic and magnetic support that leaves its electronic structure largely intact. This is achieved by exposing epitaxial graphene on ferromagnetic thin films of Co and Ni to vapor of the rare earth metal Eu at elevated temperatures, resulting in the intercalation of an Eu monolayer in between graphene and its substrate. The system is atomically well defined, with the Eu monolayer forming a (√{3 }×√{3 }) R 30∘ superstructure with respect to the graphene lattice. Thereby, we avoid the strong hybridization with the (Ni,Co) substrate 3 d states that otherwise drastically modify the electronic structure of graphene. This picture is suggested by our x-ray absorption spectroscopy measurements which show that after Eu intercalation the empty 2 p states of C atoms resemble more the ones measured for graphite in contrast to graphene directly bound to 3 d ferromagnetic substrates. We use x-ray magnetic circular dichroism at the Co and Ni L2 ,3 and Eu M4 ,5 as an element-specific probe to investigate magnetism in these systems. An antiferromagnetic coupling between Eu and Co/Ni moments is found, which is so strong that a magnetic moment of the Eu layer can be detected at room temperature. Density functional theory calculations confirm the antiferromagnetic coupling and provide an atomic insight into the magnetic coupling mechanism.

  2. 3D LBFGS inversion of controlled source extremely low frequency electromagnetic data

    NASA Astrophysics Data System (ADS)

    Cao, Meng; Tan, Han-Dong; Wang, Kun-Peng

    2016-12-01

    The controlled source extremely low frequency (CSELF) electromagnetic method is characterized by extremely long and powerful sources and a huge measurement range. Its electromagnetic field can therefore be affected by the ionosphere and displacement current. Research on 3D forward modeling and inversion of CSELF electromagnetic data is currently in its infancy. This paper makes exploratory attempts to firstly calculate the 1D extremely low frequency electromagnetic field under ionosphere-air-earth coupling circumstances, and secondly analyze the propagation characteristics of the background electromagnetic field. The 3D staggered-grid finite difference scheme for solving for the secondary electric field is adopted and incorporated with the 1D modeling algorithm to complete 3D forward modeling. Considering that surveys can be carried out in the near field and transition zone for lower frequencies, the 3D Limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) inversion of CSELF electromagnetic data is presented (in which the sources, or primary fields, are included), with the aim of directly inverting the impedance data, regardless of where it is acquired. Derivation of the objective functional gradient is the core component in the inversion. Synthetic tests indicate that the well-chosen approximation to the Hessian can significantly speed up the inversion. The model responses corresponding to the coexistence of conductive and resistive blocks show that the off-diagonal components of tensor impedance are much more sensitive to the resistivity variation than the diagonal components. In comparison with conventional scalar inversion, tensor inversion is superior in the recoveries of electric anomalies and background resistivity.

  3. 3D inversion of aeromagnetic Data on Las Tablas District, Panama

    NASA Astrophysics Data System (ADS)

    Batista-Rodríguez, José A.; Caballero, Alberto; Pérez-Flores, Marco A.; Almaguer-Carmenates, Yuri

    2017-03-01

    We present a 3D model of Las Tablas District, Panama, obtained from the 3D inversion of aeromagnetic data, and constrained with information from surface geology, water wells and topography. The 3D model suggests the location, boundary, shape and depths of the sedimentary basin where the Mensabé and Salados rivers hydrogeological sub-basin is located. The model shows the connections between tectonics and the sedimentary basin, suggesting the probable areas for aquifers, the relations between them, their zone of recharge and discharge, and the probable zone of pollution. The inferred faults in the model may be the main recharge and discharge conduits for the groundwater and anthropogenic pollution. The geological and geometric characteristics shown in the 3D model are fundamental data for further hydrogeological and geophysical studies such as the location for future drinking water wells.

  4. 3-D wavelet compression and progressive inverse wavelet synthesis rendering of concentric mosaic.

    PubMed

    Luo, Lin; Wu, Yunnan; Li, Jin; Zhang, Ya-Qin

    2002-01-01

    Using an array of photo shots, the concentric mosaic offers a quick way to capture and model a realistic three-dimensional (3-D) environment. We compress the concentric mosaic image array with a 3-D wavelet transform and coding scheme. Our compression algorithm and bitstream syntax are designed to ensure that a local view rendering of the environment requires only a partial bitstream, thereby eliminating the need to decompress the entire compressed bitstream before rendering. By exploiting the ladder-like structure of the wavelet lifting scheme, the progressive inverse wavelet synthesis (PIWS) algorithm is proposed to maximally reduce the computational cost of selective data accesses on such wavelet compressed datasets. Experimental results show that the 3-D wavelet coder achieves high-compression performance. With the PIWS algorithm, a 3-D environment can be rendered in real time from a compressed dataset.

  5. Computation of inverse magnetic cascades

    NASA Technical Reports Server (NTRS)

    Montgomery, D.

    1981-01-01

    Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.

  6. Probabilistic 3-D time-lapse inversion of magnetotelluric data: application to an enhanced geothermal system

    NASA Astrophysics Data System (ADS)

    Rosas-Carbajal, M.; Linde, N.; Peacock, J.; Zyserman, F. I.; Kalscheuer, T.; Thiel, S.

    2015-12-01

    Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved. We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.

  7. Anisotropic 3D inversion of towed streamer EM data from the Troll West oil province (Invited)

    NASA Astrophysics Data System (ADS)

    Mattsson, J.; Midgley, J.; Zhdanov, M. S.; ENDO, M.

    2013-12-01

    Obviating the need for ocean bottom receivers, the towed streamer EM system enables CSEM data to be acquired simultaneously with seismic over very large areas in frontier and mature basins for higher production rates and more cost effective than conventional marine CSEM. The towed streamer EM data are currently processed and delivered as a spectrum of frequency-domain responses. We apply a 3D anisotropic inversion methodology for towed streamer EM data that includes a moving sensitivity domain. Our implementation is based on the 3D contraction integral equation method for computing the EM responses and Fréchet derivatives, and uses the re-weighted regularized conjugate gradient method for minimizing the objective functional with focusing regularization. We present an actual case study for the 3D anisotropic inversion of towed streamer EM data from the Troll West oil province in the North Sea, and demonstrate our ability to image the Troll West Oil and Gas Provinces. We conclude that 3D anisotropic inversion of the data from the current generation of towed streamer EM system can adequately recover both the vertical and horizontal resistivities in anisotropic hydrocarbon-bearing formations.

  8. 3-D inversion of gravity data in spherical coordinates with application to the GRAIL data

    NASA Astrophysics Data System (ADS)

    Liang, Qing; Chen, Chao; Li, Yaoguo

    2014-06-01

    Three-dimensional (3-D) inversion of gravity data has been widely used to reconstruct the density distributions of ore bodies, basins, crust, lithosphere, and upper mantle. For global model of 3-D density structures of planetary interior, such as the Earth, the Moon, or Mars, it is necessary to use an inversion algorithm that operates in the spherical coordinates. We develop a 3-D inversion algorithm formulated with specially designed model objective function and radial weighting function in the spherical coordinates. We present regional and global synthetic examples to illustrate the capability of the algorithm. The inverted results show density distribution features consistent with the true models. We also apply the algorithm to a set of lunar Bouguer gravity anomaly derived from the Gravity Recovery and Interior Laboratory (GRAIL) gravity field and obtain a lunar 3-D density distribution. High-density anomalies are clearly identified underlying lunar basins, a wide region of the lateral density heterogeneities that exist beneath the South Pole-Aitken basin are found, and low-density anomalies are distributed beneath the Feldspathic Highlands Terrane on the lunar far-side. The consistency of these results with those obtained independently from other existing methods verifies the newly developed algorithm.

  9. 3D gravity inversion and uncertainty assessment of basement relief via Particle Swarm Optimization

    NASA Astrophysics Data System (ADS)

    Pallero, J. L. G.; Fernández-Martínez, J. L.; Bonvalot, S.; Fudym, O.

    2017-04-01

    Nonlinear gravity inversion in sedimentary basins is a classical problem in applied geophysics. Although a 2D approximation is widely used, 3D models have been also proposed to better take into account the basin geometry. A common nonlinear approach to this 3D problem consists in modeling the basin as a set of right rectangular prisms with prescribed density contrast, whose depths are the unknowns. Then, the problem is iteratively solved via local optimization techniques from an initial model computed using some simplifications or being estimated using prior geophysical models. Nevertheless, this kind of approach is highly dependent on the prior information that is used, and lacks from a correct solution appraisal (nonlinear uncertainty analysis). In this paper, we use the family of global Particle Swarm Optimization (PSO) optimizers for the 3D gravity inversion and model appraisal of the solution that is adopted for basement relief estimation in sedimentary basins. Synthetic and real cases are illustrated, showing that robust results are obtained. Therefore, PSO seems to be a very good alternative for 3D gravity inversion and uncertainty assessment of basement relief when used in a sampling while optimizing approach. That way important geological questions can be answered probabilistically in order to perform risk assessment in the decisions that are made.

  10. Fast 3D inversion of airborne gravity-gradiometry data using Lanczos bidiagonalization method

    NASA Astrophysics Data System (ADS)

    Meng, Zhaohai; Li, Fengting; Zhang, Dailei; Xu, Xuechun; Huang, Danian

    2016-09-01

    We developed a new fast inversion method for to process and interpret airborne gravity gradiometry data, which was based on Lanczos bidiagonalization algorithm. Here, we describe the application of this new 3D gravity gradiometry inversion method to recover a subsurface density distribution model from the airborne measured gravity gradiometry anomalies. For this purpose, the survey area is divided into a large number of rectangular cells with each cell possessing a constant unknown density. It is well known that the solution of large linear gravity gradiometry is an ill-posed problem since using the smoothest inversion method is considerably time consuming. We demonstrate that the Lanczos bidiagonalization method can be an appropriate algorithm to solve a Tikhonov solver time cost function for resolving the large equations within a short time. Lanczos bidiagonalization is designed to make the very large gravity gradiometry forward modeling matrices to become low-rank, which will considerably reduce the running time of the inversion method. We also use a weighted generalized cross validation method to choose the appropriate Tikhonov parameter to improve inversion results. The inversion incorporates a model norm that allows us to attain the smoothing and depth of the solution; in addition, the model norm counteracts the natural decay of the kernels, which concentrate at shallow depths. The method is applied on noise-contaminated synthetic gravity gradiometry data to demonstrate its suitability for large 3D gravity gradiometry data inversion. The airborne gravity gradiometry data from the Vinton Salt Dome, USE, were considered as a case study. The validity of the new method on real data is discussed with reference to the Vinton Dome inversion result. The intermediate density values in the constructed model coincide well with previous results and geological information. This demonstrates the validity of the gravity gradiometry inversion method.

  11. Fast 3D inversion of gravity data using solution space priorconditioned lanczos bidiagonalization

    NASA Astrophysics Data System (ADS)

    Rezaie, Mohammad; Moradzadeh, Ali; Kalateh, Ali Nejati

    2017-01-01

    Inversion of gravity data is one of the most important steps in the quantitative interpretation of practical data. Inversion is a mathematical technique that automatically constructs a subsurface geophysical model from measured data, incorporating some priori information. Inversion of gravity data is time consuming because of increase in data and model parameters. Some efforts have been made to deal with this problem, one of them is using fast algorithms for solving system of equations in inverse problem. Lanczos bidiagonalization method is a fast algorithm that works based on Krylov subspace iterations and projection method, but cannot always provide a good basis for a projection method. So in this study, we combined the Krylov method with a regularization method applied to the low-dimensional projected problem. To achieve the goal, the orthonormal basis vectors of the discrete cosine transform (DCT) were used to build the low-dimensional subspace. The forward operator matrix replaced with a matrix of lower dimension, thus, the required memory and running time of the inverse modeling is decreased by using the proposed algorithm. It is shown that this algorithm can be appropriate to solve a Tikhonov cost function for inversion of gravity data. The proposed method has been applied on a noise-corrupted synthetic data and field gravity data (Mobrun gravity data) to demonstrate its reliability for three dimensional (3D) gravity inversion. The obtained results of 3D inversion both synthetic and field gravity data (Mobrun gravity data) indicate the proposed inversion algorithm could produce density models consistent with true structures.

  12. Analysis and 3D inversion of magnetotelluric crooked profile data from central Svalbard for geothermal application

    NASA Astrophysics Data System (ADS)

    Beka, Thomas I.; Smirnov, Maxim; Birkelund, Yngve; Senger, Kim; Bergh, Steffen G.

    2016-08-01

    Broadband (0.001-1000 s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS = 1.05). The final 3D resistivity model displays a complex geology of the near surface region (< 1.5 km), which suggests fractures, localized and regional fault systems and igneous intrusions in the Mesozoic platform cover deposits. The Billefjorden fault zone is revealed as a consistent and deep rooted (> 2 km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (> 1000 Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (< 10 Ωm) below the Paleozoic-Mesozoic succession in the western part of the 3D model are interpreted as part of a Devonian basin fill. These conductors are laterally and vertically bounded by resistive rocks, suggesting a conducive environment for deep geothermal heat storage. Having this scenario in an area of a known high heat-flow, deep faults and a thinned lithosphere makes the hypothesis on finding a technologically exploitable geothermal resource

  13. Large scale 3-D modeling by integration of resistivity models and borehole data through inversion

    NASA Astrophysics Data System (ADS)

    Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.

    2014-02-01

    We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing for geological models or as direct input to groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay-units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity dataset and the borehole dataset in one variable. Finally, we use k means clustering to generate a 3-D model of the subsurface structures. We apply the concept to the Norsminde survey in Denmark integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high resistive materials from information held in resistivity model and borehole observations respectively.

  14. Large-scale 3-D modeling by integration of resistivity models and borehole data through inversion

    NASA Astrophysics Data System (ADS)

    Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.

    2014-11-01

    We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing of geological models, or as direct input into groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity data set and the borehole data set in one variable. Finally, we use k-means clustering to generate a 3-D model of the subsurface structures. We apply the procedure to the Norsminde survey in Denmark, integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high-resistivity materials from information held in the resistivity model and borehole observations, respectively.

  15. Two reconstruction procedures for a 3D phaseless inverse scattering problem for the generalized Helmholtz equation

    NASA Astrophysics Data System (ADS)

    Klibanov, Michael V.; Romanov, Vladimir G.

    2016-01-01

    The 3D inverse scattering problem of the reconstruction of the unknown dielectric permittivity in the generalized Helmholtz equation is considered. Applications are in imaging of nanostructures and biological cells. The main difference with the conventional inverse scattering problems is that only the modulus of the scattering wave field is measured. The phase is not measured. The initializing wave field is the incident plane wave. On the other hand, in the previous recent works of the authors about the ‘phaseless topic’ the case of the point source was considered (Klibanov and Romanov 2015 J. Inverse Ill-Posed Problem 23 415-28 J. Inverse Ill-Posed Problem 23 187-93). Two reconstruction procedures are developed.

  16. Supramolecular 3d-4f single-molecule magnet architectures.

    PubMed

    Schmitz, Sebastian; van Leusen, Jan; Izarova, Natalya V; Lan, Yanhua; Wernsdorfer, Wolfgang; Kögerler, Paul; Monakhov, Kirill Yu

    2016-10-18

    The nanosized self-assemblies {[{Ln(III)}{H2O⊂CrLn}]2(H2O)} (Ln = Dy, 1 and Tb, 2) based on new 3d-4f mixed-metal coordination topologies are formed via extensive intramolecular hydrogen bonding that is directed by enclosed water molecules. Compounds 1 and 2 show single-molecule magnet characteristics manifested by hysteresis loops up to 1.6 K (Ueff = 8.3 cm(-1)) and 1 K (Ueff = 3.4 cm(-1)), respectively.

  17. 3D Motion Planning Algorithms for Steerable Needles Using Inverse Kinematics

    PubMed Central

    Duindam, Vincent; Xu, Jijie; Alterovitz, Ron; Sastry, Shankar; Goldberg, Ken

    2010-01-01

    Steerable needles can be used in medical applications to reach targets behind sensitive or impenetrable areas. The kinematics of a steerable needle are nonholonomic and, in 2D, equivalent to a Dubins car with constant radius of curvature. In 3D, the needle can be interpreted as an airplane with constant speed and pitch rate, zero yaw, and controllable roll angle. We present a constant-time motion planning algorithm for steerable needles based on explicit geometric inverse kinematics similar to the classic Paden-Kahan subproblems. Reachability and path competitivity are analyzed using analytic comparisons with shortest path solutions for the Dubins car (for 2D) and numerical simulations (for 3D). We also present an algorithm for local path adaptation using null-space results from redundant manipulator theory. Finally, we discuss several ways to use and extend the inverse kinematics solution to generate needle paths that avoid obstacles. PMID:21359051

  18. Recovering physical property information from subduction plate boundaries using 3D full-waveform seismic inversion

    NASA Astrophysics Data System (ADS)

    Bell, R. E.; Morgan, J. V.; Warner, M.

    2013-12-01

    Our understanding of subduction margin seismogenesis has been revolutionised in the last couple of decades with the discovery that the size of the seismogenic zone may not be controlled simply by temperature and a broad spectrum of seismic behaviour exists from stick-slip to stable sliding. Laboratory and numerical experiments suggest that physical properties, particularly fluid pressure may play an important role in controlling the seismic behaviour of subduction margins. Although drilling can provide information on physical properties along subduction thrust faults at point locations at relatively shallow depths, correlations between physical properties and seismic velocity using rock physics relationships are required to resolve physical properties along the margin and down-dip. Therefore, high resolution seismic velocity models are key to recovering physical property information at subduction plate boundaries away from drill sites. 3D Full waveform inversion (FWI) is a technique pioneered by the oil industry to obtain high-resolution high-fidelity models of physical properties in the sub-surface. 3D FWI involves the inversion of low-frequency (>2 to <7 Hz), early arriving (principally transmitted) seismic data, to recover the macro (intermediate to long-wavelength) velocity structure. Although 2D FWI has been used to improve velocity models of subduction plate boundaries before, 3D FWI has not yet been attempted. 3D inversions have superior convergence and accuracy, as they sample the subsurface with multi-azimuth multiply-crossing wavefields. In this contribution we perform a suite of synthetic tests to investigate if 3D FWI could be used to better resolve physical property information along subduction margin plate boundaries using conventionally collected 3D seismic data. We base our analysis on the Muroto Basin area of the Nankai margin and investigate if the acquisition parameters and geometry of the subduction margin render 3D seismic data collected across

  19. 3-D Sound Propagation and Acoustic Inversions in Shallow Water Oceans

    DTIC Science & Technology

    2011-09-01

    method is used to study canonical environmental models of shelfbreak front systems and nonlinear internal wave ducts. The WHOI 3D Parabolic-Equation...localization methods with normal mode theory have been established for localizing low frequency, broadband signals in a shallow water environment. Gauss ...approach for low-frequency broadband sound source localization in a shallow-water ocean is established. Gauss -Markov inverse theory is used in both

  20. 3D resistivity inversion using an improved Genetic Algorithm based on control method of mutation direction

    NASA Astrophysics Data System (ADS)

    Liu, B.; Li, S. C.; Nie, L. C.; Wang, J.; L, X.; Zhang, Q. S.

    2012-12-01

    Traditional inversion method is the most commonly used procedure for three-dimensional (3D) resistivity inversion, which usually takes the linearization of the problem and accomplish it by iterations. However, its accuracy is often dependent on the initial model, which can make the inversion trapped in local optima, even cause a bad result. Non-linear method is a feasible way to eliminate the dependence on the initial model. However, for large problems such as 3D resistivity inversion with inversion parameters exceeding a thousand, main challenges of non-linear method are premature and quite low search efficiency. To deal with these problems, we present an improved Genetic Algorithm (GA) method. In the improved GA method, smooth constraint and inequality constraint are both applied on the object function, by which the degree of non-uniqueness and ill-conditioning is decreased. Some measures are adopted from others by reference to maintain the diversity and stability of GA, e.g. real-coded method, and the adaptive adjustment of crossover and mutation probabilities. Then a generation method of approximately uniform initial population is proposed in this paper, with which uniformly distributed initial generation can be produced and the dependence on initial model can be eliminated. Further, a mutation direction control method is presented based on the joint algorithm, in which the linearization method is embedded in GA. The update vector produced by linearization method is used as mutation increment to maintain a better search direction compared with the traditional GA with non-controlled mutation operation. By this method, the mutation direction is optimized and the search efficiency is improved greatly. The performance of improved GA is evaluated by comparing with traditional inversion results in synthetic example or with drilling columnar sections in practical example. The synthetic and practical examples illustrate that with the improved GA method we can eliminate

  1. Magnetically Defined Qubits on 3D Topological Insulators

    NASA Astrophysics Data System (ADS)

    Ferreira, Gerson J.; Loss, Daniel

    2013-09-01

    We explore potentials that break time-reversal symmetry to confine the surface states of 3D topological insulators into quantum wires and quantum dots. A magnetic domain wall on a ferromagnet insulator cap layer provides interfacial states predicted to show the quantum anomalous Hall effect (QAHE). Here, we show that confinement can also occur at magnetic domain heterostructures, with states extended in the inner domain, as well as interfacial QAHE states at the surrounding domain walls. The proposed geometry allows the isolation of the wire and dot from spurious circumventing surface states. For the quantum dots, we find that highly spin-polarized quantized QAHE states at the dot edge constitute a promising candidate for quantum computing qubits.

  2. Magnetically Defined Qubits on 3D Topological Insulators

    NASA Astrophysics Data System (ADS)

    Ferreira, Gerson J.; Loss, Daniel

    2014-03-01

    We explore potentials that break time-reversal symmetry to confine the surface states of 3D topological insulators into quantum wires and quantum dots. A magnetic domain wall on a ferromagnet insulator cap layer provides interfacial states predicted to show the quantum anomalous Hall effect. Here, we show that confinement can also occur at magnetic domain heterostructures, with states extended in the inner domain, as well as interfacial QAHE states at the surrounding domain walls. The proposed geometry allows the isolation of the wire and dot from spurious circumventing surface states. For the quantum dots, we find that highly spin-polarized quantized QAHE states at the dot edge constitute a promising candidate for quantum computing qubits. See [Ferreira and Loss, Phys. Rev. Lett. 111, 106802 (2013)]. We explore potentials that break time-reversal symmetry to confine the surface states of 3D topological insulators into quantum wires and quantum dots. A magnetic domain wall on a ferromagnet insulator cap layer provides interfacial states predicted to show the quantum anomalous Hall effect. Here, we show that confinement can also occur at magnetic domain heterostructures, with states extended in the inner domain, as well as interfacial QAHE states at the surrounding domain walls. The proposed geometry allows the isolation of the wire and dot from spurious circumventing surface states. For the quantum dots, we find that highly spin-polarized quantized QAHE states at the dot edge constitute a promising candidate for quantum computing qubits. See [Ferreira and Loss, Phys. Rev. Lett. 111, 106802 (2013)]. We acknowledge support from the Swiss NSF, NCCR Nanoscience, NCCR QSIT, and the Brazillian Research Support Center Initiative (NAP Q-NANO) from Pró-Reitoria de Pesquisa (PRP/USP).

  3. Observation of a 3D Magnetic Null Point

    NASA Astrophysics Data System (ADS)

    Romano, P.; Falco, M.; Guglielmino, S. L.; Murabito, M.

    2017-03-01

    We describe high-resolution observations of a GOES B-class flare characterized by a circular ribbon at the chromospheric level, corresponding to the network at the photospheric level. We interpret the flare as a consequence of a magnetic reconnection event that occurred at a three-dimensional (3D) coronal null point located above the supergranular cell. The potential field extrapolation of the photospheric magnetic field indicates that the circular chromospheric ribbon is cospatial with the fan footpoints, while the ribbons of the inner and outer spines look like compact kernels. We found new interesting observational aspects that need to be explained by models: (1) a loop corresponding to the outer spine became brighter a few minutes before the onset of the flare; (2) the circular ribbon was formed by several adjacent compact kernels characterized by a size of 1″–2″ (3) the kernels with a stronger intensity emission were located at the outer footpoint of the darker filaments, departing radially from the center of the supergranular cell; (4) these kernels started to brighten sequentially in clockwise direction; and (5) the site of the 3D null point and the shape of the outer spine were detected by RHESSI in the low-energy channel between 6.0 and 12.0 keV. Taking into account all these features and the length scales of the magnetic systems involved in the event, we argue that the low intensity of the flare may be ascribed to the low amount of magnetic flux and to its symmetric configuration.

  4. Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri; Werner, Gregory; Zhdankin, Vladimir

    2016-10-01

    Magnetic reconnection is a fundamental plasma process that converts magnetic energy into particle kinetic energy. ``Relativistic'' reconnection is of interest in astrophysical contexts because it can accelerate particles to relativistic energies high enough for synchrotron (or inverse Compton) emission to explain observed high-energy radiation. After several 2D particle-in-cell (PIC) simulations of reconnection in pair plasmas demonstrated power-law electron-energy spectra extending to high energies, a few 3D simulations surprisingly confirmed the robustness of nonthermal particle acceleration, despite fundamental differences, such as the development of the relativistic drift-kink instability (RDKI) in 3D. We present a comprehensive PIC study of 3D relativistic pair-plasma reconnection characterizing the effect of the third dimension. We investigate how reconnection dynamics and particle acceleration depend on guide magnetic field Bz and on the simulation box length Lz in the third dimension. We find that, while the RDKI does indeed grow in 3D reconnection, it does not inhibit particle acceleration, even in the absence of guide field. This work was funded by NSF, DOE, and NASA.

  5. Complex Crustal Structure Beneath Western Turkey Revealed by 3D Seismic Full Waveform Inversion (FWI)

    NASA Astrophysics Data System (ADS)

    Cubuk-Sabuncu, Yesim; Taymaz, Tuncay; Fichtner, Andreas

    2016-04-01

    We present a 3D radially anisotropic velocity model of the crust and uppermost mantle structure beneath the Sea of Marmara and surroundings based on the full waveform inversion method. The intense seismic activity and crustal deformation are observed in the Northwest Turkey due to transition tectonics between the strike-slip North Anatolian Fault (NAF) and the extensional Aegean region. We have selected and simulated complete waveforms of 62 earthquakes (Mw > 4.0) occurred during 2007-2015, and recorded at (Δ < 10°) distances. Three component earthquake data is obtained from broadband seismic stations of Kandilli Observatory and Earthquake Research Center (KOERI, Turkey), Hellenic Unified Seismic Network (HUSN, Greece) and Earthquake Research Center of Turkey (AFAD-DAD). The spectral-element solver of the wave equation, SES3D algorithm, is used to simulate seismic wave propagation in 3D spherical coordinates (Fichtner, 2009). The Large Scale Seismic Inversion Framework (LASIF) workflow tool is also used to perform full seismic waveform inversion (Krischer et al., 2015). The initial 3D Earth model is implemented from the multi-scale seismic tomography study of Fichtner et al. (2013). Discrepancies between the observed and simulated synthetic waveforms are determined using the time-frequency misfits which allows a separation between phase and amplitude information (Fichtner et al., 2008). The conjugate gradient optimization method is used to iteratively update the initial Earth model when minimizing the misfit. The inversion is terminated after 19 iterations since no further advances are observed in updated models. Our analysis revealed shear wave velocity variations of the shallow and deeper crustal structure beneath western Turkey down to depths of ~35-40 km. Low shear wave velocity anomalies are observed in the upper and mid crustal depths beneath major fault zones located in the study region. Low velocity zones also tend to mark the outline of young volcanic

  6. Simultaneous elastic parameter inversion in 2-D/3-D TTI medium combined later arrival times

    NASA Astrophysics Data System (ADS)

    Bai, Chao-ying; Wang, Tao; Yang, Shang-bei; Li, Xing-wang; Huang, Guo-jiao

    2016-04-01

    Traditional traveltime inversion for anisotropic medium is, in general, based on a "weak" assumption in the anisotropic property, which simplifies both the forward part (ray tracing is performed once only) and the inversion part (a linear inversion solver is possible). But for some real applications, a general (both "weak" and "strong") anisotropic medium should be considered. In such cases, one has to develop a ray tracing algorithm to handle with the general (including "strong") anisotropic medium and also to design a non-linear inversion solver for later tomography. Meanwhile, it is constructive to investigate how much the tomographic resolution can be improved by introducing the later arrivals. For this motivation, we incorporated our newly developed ray tracing algorithm (multistage irregular shortest-path method) for general anisotropic media with a non-linear inversion solver (a damped minimum norm, constrained least squares problem with a conjugate gradient approach) to formulate a non-linear inversion solver for anisotropic medium. This anisotropic traveltime inversion procedure is able to combine the later (reflected) arrival times. Both 2-D/3-D synthetic inversion experiments and comparison tests show that (1) the proposed anisotropic traveltime inversion scheme is able to recover the high contrast anomalies and (2) it is possible to improve the tomographic resolution by introducing the later (reflected) arrivals, but not as expected in the isotropic medium, because the different velocity (qP, qSV and qSH) sensitivities (or derivatives) respective to the different elastic parameters are not the same but are also dependent on the inclination angle.

  7. The multi-scale 3D-1D compatibility scoring for inverse protein folding problem

    SciTech Connect

    Oniuka, Kentaro; Asai, Kiyoshi

    1994-12-31

    The applicability of the Multi-Scale Structure Description (MSSD) scheme to the inverse-folding problems was investigated. An MSSD represents a 3D protein structure with multiple symbolic sequences, where fine structures are represented with the sequence at low levels, the middle scale structural motifs at middle levels, and global topology at high levels. Each symbol in the symbolic sequence denotes a type of local structure of the level scale. The structure fragments are classified at each scale level respectively according to the shape and the environment around the fragments: how the structure is exposed to the solvent or buried in the molecule. I modeled the propensity of an amino-acid sequence to the structure fragment type (i.e., primary constraint) at each scale level. The local propensity is, therefore, modeled at small scale (low) levels, while the global propensity modeled at large scale (high) levels. Thus, superposing all the primary constraints, a 3D protein structure yields an amino-acid sequence profile. Evaluating the fit of an amino acid sequence to the profile derived from the known 3D protein structure, we can identify which 3D structure the given amino-acid sequence would fold into. I checked whether a sequence identifies its own structure over two hundred protein sequences. In many cases, an amino acid sequence identified its own 3D protein structure.

  8. Integrated gravity and gravity gradient 3D inversion using the non-linear conjugate gradient

    NASA Astrophysics Data System (ADS)

    Qin, Pengbo; Huang, Danian; Yuan, Yuan; Geng, Meixia; Liu, Jie

    2016-03-01

    Gravity data, which are critical in mineral, oil, and gas exploration, are obtained from the vertical component of the gravity field, while gravity gradient data are measured from changes in the gravity field in three directions. However, few studies have sought to improve exploration techniques by integrating gravity and gravity gradient data using inversion methods. In this study, we developed a new method to integrate gravity and gravity gradient data in a 3D density inversion using the non-linear conjugate gradient (NLCG) method and the minimum gradient support (MGS) functional to regularize the 3D inverse problem and to obtain a clear and accurate image of the anomalous body. The NLCG algorithm, which is suitable for solving large-scale nonlinear optimization problems and requires no memory storage, was compared to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton algorithm and the results indicated that the convergence rate of NLCG is slower, but that the storage requirement and computation time is lower. To counteract the decay in kernel function, we introduced a depth weighting function for anomalous bodies at the same depth, with information about anomalous body depth obtained from well log and seismic exploration data. For anomalous bodies at different depths, we introduced a spatial gradient weighting function to incorporate additional information obtained in the inversion. We concluded that the spatial gradient weighting function enhanced the spatial resolution of the recovered model. Furthermore, our results showed that including multiple components for inversion increased the resolution of the recovered model. We validated our model by applying our inversion method to survey data from Vinton salt dome, Louisiana, USA. The results showed good agreement with known geologic information; thus confirming the accuracy of this approach.

  9. Probabilistic 3-D time-lapse inversion of magnetotelluric data: Application to an enhanced geothermal system

    USGS Publications Warehouse

    Rosas-Carbajal, Marina; Linde, Nicolas; Peacock, Jared R.; Zyserman, F. I.; Kalscheuer, Thomas; Thiel, Stephan

    2015-01-01

    Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved.We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.

  10. 3D Inversion of complex resistivity data: Case study on Mineral Exploration Site.

    NASA Astrophysics Data System (ADS)

    Son, Jeong-Sul; Kim, Jung-ho; Park, Sam-gyu; Park, My-Kyung

    2016-04-01

    Complex resistivity (CR) method is a frequency domain induced polarization (IP) method. It is also known as Spectral IP (SIP) method, if wider frequencies are used in data acquisition and interpretation. Although it takes more times than conventional time domain IP method, its data quality is more stable because its data acquisition which measures amplitude and phase is done when the source current is being injected. Our research group has been studying the modeling and inversion algorithms of complex resistivity (CR) method since several years ago and recently applied developed algorithms to various real field application. Due to tough terrain in our country, Profile survey and 2D interpretation were generally used. But to get more precise interpretation, three dimensional modeling and inversion algorithm is required. We developed three dimensional inversion algorithm for this purpose. In the inversion, we adopt the method of adaptive lagraingian multiplier which is automatically set based on the size of error misfit and model regularization norm. It was applied on the real data acquired for mineral exploration sites. CR data was acquired with the Zeta system, manufactured by Zonge Co. In the inversion, only the lower frequency data is used considering its quality and developed 3D inversion algorithm was applied to the acquired data set. Its results were compared to those of time domain IP data conducted at the same site. Resistivity image sections of CR and conventional resistivity method were almost identical. Phase anomalies were well matched with chargeability anomalies and the mining history of the test site. Each anomalies were well discriminated in 3D interpretation than those of 2D. From those experiments, we know that CR method was very effective for the mineral exploration.

  11. Earthquake source tensor inversion with the gCAP method and 3D Green's functions

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Ben-Zion, Y.; Zhu, L.; Ross, Z.

    2013-12-01

    We develop and apply a method to invert earthquake seismograms for source properties using a general tensor representation and 3D Green's functions. The method employs (i) a general representation of earthquake potency/moment tensors with double couple (DC), compensated linear vector dipole (CLVD), and isotropic (ISO) components, and (ii) a corresponding generalized CAP (gCap) scheme where the continuous wave trains are broken into Pnl and surface waves (Zhu & Ben-Zion, 2013). For comparison, we also use the waveform inversion method of Zheng & Chen (2012) and Ammon et al. (1998). Sets of 3D Green's functions are calculated on a grid of 1 km3 using the 3-D community velocity model CVM-4 (Kohler et al. 2003). A bootstrap technique is adopted to establish robustness of the inversion results using the gCap method (Ross & Ben-Zion, 2013). Synthetic tests with 1-D and 3-D waveform calculations show that the source tensor inversion procedure is reasonably reliable and robust. As initial application, the method is used to investigate source properties of the March 11, 2013, Mw=4.7 earthquake on the San Jacinto fault using recordings of ~45 stations up to ~0.2Hz. Both the best fitting and most probable solutions include ISO component of ~1% and CLVD component of ~0%. The obtained ISO component, while small, is found to be a non-negligible positive value that can have significant implications for the physics of the failure process. Work on using higher frequency data for this and other earthquakes is in progress.

  12. Joint earthquake source inversions using seismo-geodesy and 3-D earth models

    NASA Astrophysics Data System (ADS)

    Weston, J.; Ferreira, A. M. G.; Funning, G. J.

    2014-08-01

    A joint earthquake source inversion technique is presented that uses InSAR and long-period teleseismic data, and, for the first time, takes 3-D Earth structure into account when modelling seismic surface and body waves. Ten average source parameters (Moment, latitude, longitude, depth, strike, dip, rake, length, width and slip) are estimated; hence, the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets. Unwrapped interferograms and long-period seismic data are jointly inverted for the location, fault geometry and seismic moment, using a hybrid downhill Powell-Monte Carlo algorithm. While the InSAR data are modelled assuming a rectangular dislocation in a homogeneous half-space, seismic data are modelled using the spectral element method for a 3-D earth model. The effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude (Mw 6.0-6.6). Synthetic tests highlight the improvement in the constraint of fault geometry (strike, dip and rake) and moment when InSAR and seismic data are combined. Tests comparing the effect of using a 1-D or 3-D earth model show that long-period surface waves are more sensitive than long-period body waves to the change in earth model. Incorrect source parameters, particularly incorrect fault dip angles, can compensate for systematic errors in the assumed Earth structure, leading to an acceptable data fit despite large discrepancies in source parameters. Three real earthquakes are also investigated: Eureka Valley, California (1993 May 17, Mw 6.0), Aiquile, Bolivia (1998 February 22, Mw 6.6) and Zarand, Iran (2005 May 22, Mw 6.5). These events are located in different tectonic environments and show large discrepancies between InSAR and seismically determined source models. Despite the 40-50 km discrepancies in location between previous geodetic and

  13. MagicFinger: 3D Magnetic Fingerprints for Indoor Location

    PubMed Central

    Carrillo, Daniel; Moreno, Victoria; Úbeda, Benito; Skarmeta, Antonio F.

    2015-01-01

    Given the indispensable role of mobile phones in everyday life, phone-centric sensing systems are ideal candidates for ubiquitous observation purposes. This paper presents a novel approach for mobile phone-centric observation applied to indoor location. The approach involves a location fingerprinting methodology that takes advantage of the presence of magnetic field anomalies inside buildings. Unlike existing work on the subject, which uses the intensity of magnetic field for fingerprinting, our approach uses all three components of the measured magnetic field vectors to improve accuracy. By using adequate soft computing techniques, it is possible to adequately balance the constraints of common solutions. The resulting system does not rely on any infrastructure devices and therefore is easy to manage and deploy. The proposed system consists of two phases: the offline phase and the online phase. In the offline phase, magnetic field measurements are taken throughout the building, and 3D maps are generated. Then, during the online phase, the user's location is estimated through the best estimator for each zone of the building. Experimental evaluations carried out in two different buildings confirm the satisfactory performance of indoor location based on magnetic field vectors. These evaluations provided an error of (11.34 m, 4.78 m) in the (x, y) components of the estimated positions in the first building where the experiments were carried out, with a standard deviation of (3.41 m, 4.68 m); and in the second building, an error of (4 m, 2.98 m) with a deviation of (2.64 m, 2.33 m). PMID:26184230

  14. Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Maceira, M.; Zhang, H.; Rowe, C. A.

    2009-12-01

    We focus on the development and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets. Building on previous efforts of joint invesion using surface wave dispersion measurements, gravity data, and receiver functions, we have added a fourth dataset, seismic body wave P and S travel times, to the simultaneous joint inversion method. We present a 3D seismic velocity model of the crust and upper mantle of northwest China resulting from the simultaneous, joint inversion of these four data types. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations. Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of the fourth dataset, consisting of seismic travel-time data, helps to constrain the shear wave velocities both vertically and horizontally in the model cells crossed by the ray paths. Incorporation of both P and S body wave travel times allows us to invert for both P and S velocity structure, capitalizing on empirical relationships between both wave types’ seismic velocities with rock densities, thus eliminating the need for ad hoc assumptions regarding the Poisson ratios. Our new tomography algorithm is a modification of the Maceira and Ammon joint inversion code, in combination with the Zhang and Thurber TomoDD (double-difference tomography) program.

  15. Finite Element Based Anisotropic 3D Inversion of Marine CSEM Data

    NASA Astrophysics Data System (ADS)

    Chung, Y.; Byun, J.

    2015-12-01

    In order to interpret three-dimensional (3D) marine controlled-source electromagnetic (MCSEM) data, it is critical to accurately determine electrical anisotropy because ignoring anisotropy can produce misleading artifacts. In this study, we present an inversion method for 3D subsurface imaging in media with an inhomogeneous and anisotropic conductivity distribution. Direct solvers are incorporated both in the forward and inverse problems, For the forward problem, the vector Helmholtz equation for the secondary electric field is discretized on a hexahedral mesh using edge finite elements, then a direct sparse-matrix solver is chosen to effectively reuse its factorization both in the survey simulation and Jacobian computation. The inversion method is formulated as a functional optimization with an objective functional containing terms measuring data misfit and model structure by means of smoothness and anisotropy. These measures are efficiently incorporated through the use of an iteratively reweighted least-squares scheme. The objective functional is minimized by a Gauss-Newton approach using a direct dense-matrix solver. We demonstrate the accuracy and applicability of the algorithm by testing it on synthetic data sets.

  16. 3D inversion of time-lapse CSEM data for reservoir monitoring

    NASA Astrophysics Data System (ADS)

    Black, N.; Wilson, G. A.; Zhdanov, M. S.

    2010-12-01

    Effective reservoir monitoring requires time-lapse reservoir information throughout the interwell volume. The ability to understand and control reservoir behavior over the course of production allows for optimization of reservoir performance and production strategies. Good monitoring information makes it possible to improve the timing and location of new drilling (for both production and injection wells), to recognize flow paths, and to map oil that has been bypassed. Recent studies have inferred the feasibility of time-lapse marine controlled-source electromagnetic (CSEM) methods for the monitoring of offshore oil and gas fields. However, quantitative interpretations to ascertain what reservoir information may be recovered have not been performed. The time-lapse CSEM inverse problem can be highly constrained since the geometry of the reservoir is established prior from high resolution seismic surveys, rock and fluid properties are measured from well logs, and multiple history matched production scenarios are contained in dynamic reservoir models. We present a 3D inversion study of synthetic time-lapse CSEM data modeled from dynamic reservoir simulations. We demonstrate that even with few constraints on the model, the hydrocarbon-water front can be recovered from 3D inversion.

  17. A hybrid method for inversion of 3D DC resistivity logging measurements.

    PubMed

    Gajda-Zagórska, Ewa; Schaefer, Robert; Smołka, Maciej; Paszyński, Maciej; Pardo, David

    This paper focuses on the application of hp hierarchic genetic strategy (hp-HGS) for solution of a challenging problem, the inversion of 3D direct current (DC) resistivity logging measurements. The problem under consideration has been formulated as the global optimization one, for which the objective function (misfit between computed and reference data) exhibits multiple minima. In this paper, we consider the extension of the hp-HGS strategy, namely we couple the hp-HGS algorithm with a gradient based optimization method for a local search. Forward simulations are performed with a self-adaptive hp finite element method, hp-FEM. The computational cost of misfit evaluation by hp-FEM depends strongly on the assumed accuracy. This accuracy is adapted to the tree of populations generated by the hp-HGS algorithm, which makes the global phase significantly cheaper. Moreover, tree structure of demes as well as branch reduction and conditional sprouting mechanism reduces the number of expensive local searches up to the number of minima to be recognized. The common (direct and inverse) accuracy control, crucial for the hp-HGS efficiency, has been motivated by precise mathematical considerations. Numerical results demonstrate the suitability of the proposed method for the inversion of 3D DC resistivity logging measurements.

  18. Designing bioinspired composite reinforcement architectures via 3D magnetic printing

    NASA Astrophysics Data System (ADS)

    Martin, Joshua J.; Fiore, Brad E.; Erb, Randall M.

    2015-10-01

    Discontinuous fibre composites represent a class of materials that are strong, lightweight and have remarkable fracture toughness. These advantages partially explain the abundance and variety of discontinuous fibre composites that have evolved in the natural world. Many natural structures out-perform the conventional synthetic counterparts due, in part, to the more elaborate reinforcement architectures that occur in natural composites. Here we present an additive manufacturing approach that combines real-time colloidal assembly with existing additive manufacturing technologies to create highly programmable discontinuous fibre composites. This technology, termed as `3D magnetic printing', has enabled us to recreate complex bioinspired reinforcement architectures that deliver enhanced material performance compared with monolithic structures. Further, we demonstrate that we can now design and evolve elaborate reinforcement architectures that are not found in nature, demonstrating a high level of possible customization in discontinuous fibre composites with arbitrary geometries.

  19. Unsupervised fuzzy segmentation of 3D magnetic resonance brain images

    NASA Astrophysics Data System (ADS)

    Velthuizen, Robert P.; Hall, Lawrence O.; Clarke, Laurence P.; Bensaid, Amine M.; Arrington, J. A.; Silbiger, Martin L.

    1993-07-01

    Unsupervised fuzzy methods are proposed for segmentation of 3D Magnetic Resonance images of the brain. Fuzzy c-means (FCM) has shown promising results for segmentation of single slices. FCM has been investigated for volume segmentations, both by combining results of single slices and by segmenting the full volume. Different strategies and initializations have been tried. In particular, two approaches have been used: (1) a method by which, iteratively, the furthest sample is split off to form a new cluster center, and (2) the traditional FCM in which the membership grade matrix is initialized in some way. Results have been compared with volume segmentations by k-means and with two supervised methods, k-nearest neighbors and region growing. Results of individual segmentations are presented as well as comparisons on the application of the different methods to a number of tumor patient data sets.

  20. Designing bioinspired composite reinforcement architectures via 3D magnetic printing

    PubMed Central

    Martin, Joshua J.; Fiore, Brad E.; Erb, Randall M.

    2015-01-01

    Discontinuous fibre composites represent a class of materials that are strong, lightweight and have remarkable fracture toughness. These advantages partially explain the abundance and variety of discontinuous fibre composites that have evolved in the natural world. Many natural structures out-perform the conventional synthetic counterparts due, in part, to the more elaborate reinforcement architectures that occur in natural composites. Here we present an additive manufacturing approach that combines real-time colloidal assembly with existing additive manufacturing technologies to create highly programmable discontinuous fibre composites. This technology, termed as ‘3D magnetic printing', has enabled us to recreate complex bioinspired reinforcement architectures that deliver enhanced material performance compared with monolithic structures. Further, we demonstrate that we can now design and evolve elaborate reinforcement architectures that are not found in nature, demonstrating a high level of possible customization in discontinuous fibre composites with arbitrary geometries. PMID:26494282

  1. Solving Dirac equations on a 3D lattice with inverse Hamiltonian and spectral methods

    NASA Astrophysics Data System (ADS)

    Ren, Z. X.; Zhang, S. Q.; Meng, J.

    2017-02-01

    A new method to solve the Dirac equation on a 3D lattice is proposed, in which the variational collapse problem is avoided by the inverse Hamiltonian method and the fermion doubling problem is avoided by performing spatial derivatives in momentum space with the help of the discrete Fourier transform, i.e., the spectral method. This method is demonstrated in solving the Dirac equation for a given spherical potential in a 3D lattice space. In comparison with the results obtained by the shooting method, the differences in single-particle energy are smaller than 10-4 MeV, and the densities are almost identical, which demonstrates the high accuracy of the present method. The results obtained by applying this method without any modification to solve the Dirac equations for an axial-deformed, nonaxial-deformed, and octupole-deformed potential are provided and discussed.

  2. High-resolution imaging of crustal melts using 3D full-waveform seismic inversion

    NASA Astrophysics Data System (ADS)

    Warner, M.; Morgan, J. V.

    2013-12-01

    A newly practical seismic imaging technique, 3D full-waveform inversion (FWI), now has the ability to image zones of melt and melt pathways throughout the crust with a better resolution than any other geophysical method. 3D FWI has recently changed practice within the petroleum industry where it is used to obtain high-resolution high-fidelity models of physical properties in the sub-surface that are both interpreted directly and used to improve the migration of deeper reflections. This technology has been spectacularly successful in improving the imaging of reservoirs beneath shallow heterogeneities produced by, for example, gas clouds, buried fluvial channels, carbonate reefs and salt bodies. During FWI, the sub-surface model is recovered principally by using the low-frequency transmitted, refracted portion of the wavefield which is most sensitive to the macro-velocity structure. In the petroleum industry, these inversions are now routinely performed using long-offset surface-streamer and ocean-bottom data to maximum source-receiver offsets of about 15 km, leading to a maximum penetration depth of around 5 km. Using longer offsets, it is possible to extend this technology to image deeper crustal targets. Localised zones of partial melt produce large changes in p-wave and s-wave properties that are restricted in their spatial extent, and that therefore form ideal targets for 3D FWI. We have performed a suite of tests to explore the use of 3D FWI in imaging melt distribution beneath the active volcano of Montserrat. We built a model of the subsurface using a 3D travel-time tomographic model obtained from the SEA CALIPSO experiment. We added two magma chambers in accordance with a model obtained using surface-elevation changes and geochemical data. We used a wide-angle, wide-azimuth acquisition geometry to generate a fully-elastic synthetic seismic dataset, added noise, and inverted the windowed transmitted arrivals only. We used an elastic code for the forward

  3. Towards Automated Seismic Moment Tensor Inversion in Australia Using 3D Structural Model

    NASA Astrophysics Data System (ADS)

    Hingee, M.; Tkalcic, H.; Fichtner, A.; Sambridge, M.; Kennett, B. L.; Gorbatov, A.

    2009-12-01

    There is significant seismic activity in the region around Australia, largely due to the plate boundaries to the north and to the east of the mainland. This seismicity poses serious seismic and tsunamigenic hazard in a wider region, and risk to coastal areas of Australia, and is monitored by Geoscience Australia (GA) using a network of permanent broadband seismometers within Australia. Earthquake and tsunami warning systems were established by the Australian Government and have been using the waveforms from the GA seismological network. The permanent instruments are augmented by non-GA seismic stations based both within and outside of Australia. In particular, seismic moment tensor (MT) solutions for events around Australia as well as local distances are useful for both warning systems and geophysical studies in general. These monitoring systems, however, currently use only one dimensional, spherically-symmetric models of the Earth for source parameter determination. Recently, a novel 3D model of Australia and the surrounding area has been developed from spectral element simulations [1], taking into account not only velocity heterogeneities, but also radial anisotropy and seismic attenuation. This development, inter alia, introduces the potential of providing significant improvements in MT solution accuracy. Allowing reliable MT solutions with reduced dependence on non-GA stations is a secondary advantage. We studied the feasibility of using 1D versus 3D structural models. The accuracy of the 3D model has been investigated, confirming that these models are in most cases superior to the 1D models. A full MT inversion method using a point source approximation was developed as the first step, keeping in mind that for more complex source time functions, a finite source inversion will be needed. Synthetic experiments have been performed with random noise added to the signal to test the code in the both 1D and 3D setting, using a precomputed library of structural Greens

  4. 3-D inversion of airborne electromagnetic data parallelized and accelerated by local mesh and adaptive soundings

    NASA Astrophysics Data System (ADS)

    Yang, Dikun; Oldenburg, Douglas W.; Haber, Eldad

    2014-03-01

    Airborne electromagnetic (AEM) methods are highly efficient tools for assessing the Earth's conductivity structures in a large area at low cost. However, the configuration of AEM measurements, which typically have widely distributed transmitter-receiver pairs, makes the rigorous modelling and interpretation extremely time-consuming in 3-D. Excessive overcomputing can occur when working on a large mesh covering the entire survey area and inverting all soundings in the data set. We propose two improvements. The first is to use a locally optimized mesh for each AEM sounding for the forward modelling and calculation of sensitivity. This dedicated local mesh is small with fine cells near the sounding location and coarse cells far away in accordance with EM diffusion and the geometric decay of the signals. Once the forward problem is solved on the local meshes, the sensitivity for the inversion on the global mesh is available through quick interpolation. Using local meshes for AEM forward modelling avoids unnecessary computing on fine cells on a global mesh that are far away from the sounding location. Since local meshes are highly independent, the forward modelling can be efficiently parallelized over an array of processors. The second improvement is random and dynamic down-sampling of the soundings. Each inversion iteration only uses a random subset of the soundings, and the subset is reselected for every iteration. The number of soundings in the random subset, determined by an adaptive algorithm, is tied to the degree of model regularization. This minimizes the overcomputing caused by working with redundant soundings. Our methods are compared against conventional methods and tested with a synthetic example. We also invert a field data set that was previously considered to be too large to be practically inverted in 3-D. These examples show that our methodology can dramatically reduce the processing time of 3-D inversion to a practical level without losing resolution

  5. 3D Self-Potential Inversion for Monitoring DNAPL Contaminant Distributions

    NASA Astrophysics Data System (ADS)

    Minsley, B. J.; Sogade, J.; Vichabian, Y.; Morgan, F. D.

    2005-05-01

    Self-potential (SP) data are collected over an area known to be contaminated with Dense Non-Aqueous Phase Liquids (DNAPLs) at the Savannah River Site in South Carolina. The field experiment consists of approximately 100 SP measurements on a surface grid and in four boreholes, and is repeated after one year. DNAPLs are known to undergo redox reactions during their degradation in the environment, which is often biologically mediated. Self-potential geophysics is employed in this study because of its sensitivity to the in-situ biochemical processes that degrade the contaminants. These reactions provide an electrochemical source that is manifested as an SP signature at the measurement locations remote from the contaminated areas. 3D inversion of the SP data is therefore needed to spatially locate the distribution of sources, which is related to contaminant presence. The inversion incorporates the 3D resistivity structure collected at the same site, and is better constrained in depth by using borehole data and regularization. Ground truth information taken after the first field experiment provides concentration data with depth for several DNAPL species in five boreholes. There is a good correlation between the ground truth data and SP source inversion, though this comparison is limited by several factors: the difference in resolution of the ground truth and inverted data, and the dependence of the redox processes on other constituents that were not measured during the ground truthing, such as oxygen content or microbial presence. Inversion of the second year's dataset provides information on the changes in the contaminant distribution, either due to natural degradation or ongoing remediation.

  6. Reconstructing the Vulcano Island evolution from 3D modeling of magnetic signatures

    NASA Astrophysics Data System (ADS)

    Napoli, Rosalba; Currenti, Gilda

    2016-06-01

    High-resolution ground and marine magnetic data are exploited for a detailed definition of a 3D model of the Vulcano Island volcanic complex. The resulting 3D magnetic imaging, obtained by 3-D inverse modeling technique, has delivered useful constraints both to reconstruct the Vulcano Island evolution and to be used as input data for volcanic hazard assessment models. Our results constrained the depth and geometry of the main geo-structural features revealing more subsurface volcanic structures than exposed ones and allowing to elucidate the relationships between them. The recognition of two different magnetization sectors, approximatively coincident with the structural depressions of Piano caldera, in the southern half of the island, and La Fossa caldera at the north, suggests a complex structural and volcanic evolution. Magnetic highs identified across the southern half of the island reflect the main crystallized feeding systems, intrusions and buried vents, whose NNW-SSE preferential alignment highlights the role of the NNW-SSE Tindari-Letojanni regional system from the initial activity of the submarine edifice, to the more recent activity of the Vulcano complex. The low magnetization area, in the middle part of the island may result from hydrothermally altered rocks. Their presence not only in the central part of the volcano edifice but also in other peripheral areas, is a sign of a more diffuse historical hydrothermal activity than in present days. Moreover, the high magnetization heterogeneity within the upper flanks of La Fossa cone edifice is an imprint of a composite distribution of unaltered and altered rocks with different mechanical properties, which poses in this area a high risk level for failure processes especially during volcanic or hydrothermal crisis.

  7. 3D inversion based on multi-grid approach of magnetotelluric data from Northern Scandinavia

    NASA Astrophysics Data System (ADS)

    Cherevatova, M.; Smirnov, M.; Korja, T. J.; Egbert, G. D.

    2012-12-01

    In this work we investigate the geoelectrical structure of the cratonic margin of Fennoscandian Shield by means of magnetotelluric (MT) measurements carried out in Northern Norway and Sweden during summer 2011-2012. The project Magnetotellurics in the Scandes (MaSca) focuses on the investigation of the crust, upper mantle and lithospheric structure in a transition zone from a stable Precambrian cratonic interior to a passive continental margin beneath the Caledonian Orogen and the Scandes Mountains in western Fennoscandia. Recent MT profiles in the central and southern Scandes indicated a large contrast in resistivity between Caledonides and Precambrian basement. The alum shales as a highly conductive layers between the resistive Precambrian basement and the overlying Caledonian nappes are revealed from this profiles. Additional measurements in the Northern Scandes were required. All together data from 60 synchronous long period (LMT) and about 200 broad band (BMT) sites were acquired. The array stretches from Lofoten and Bodo (Norway) in the west to Kiruna and Skeleftea (Sweden) in the east covering an area of 500x500 square kilometers. LMT sites were occupied for about two months, while most of the BMT sites were measured during one day. We have used new multi-grid approach for 3D electromagnetic (EM) inversion and modelling. Our approach is based on the OcTree discretization where the spatial domain is represented by rectangular cells, each of which might be subdivided (recursively) into eight sub-cells. In this simplified implementation the grid is refined only in the horizontal direction, uniformly in each vertical layer. Using multi-grid we manage to have a high grid resolution near the surface (for instance, to tackle with galvanic distortions) and lower resolution at greater depth as the EM fields decay in the Earth according to the diffusion equation. We also have a benefit in computational costs as number of unknowns decrease. The multi-grid forward

  8. 3-D, Impulsive Magnetic Reconnection in a Laboratory Plasma (Invited)

    NASA Astrophysics Data System (ADS)

    Dorfman, S. E.; Ji, H.; Yamada, M.; Yoo, J.; Myers, C. E.; Roytershteyn, V.; Daughton, W. S.; Jara-Almonte, J.

    2013-12-01

    Magnetic reconnection is a fundamental plasma process involving the efficient conversion of magnetic field energy to plasma kinetic energy through changing field line topology. In many space and astrophysical systems, including the solar surface and the Earth's magnetotail, reconnection is not only fast, but also impulsive; in other words, a slow buildup phase is followed by a comparatively quick release of magnetic energy. An important question in the literature is if these examples of impulsive reconnection can be described by a two-dimensional model with no variation in the out-of-plane direction or if impulsive reconnection is fundamentally three-dimensional. Events observed on the Magnetic Reconnection Experiment (MRX) are characterized by large local gradients in the third direction and cannot be explained by 2-D models [1]. Detailed measurements show that the ejection of flux rope structures from the current sheet plays a key role in these events. By contrast, even though electromagnetic fluctuations in the lower hybrid frequency range are also observed concurrently with the impulsive behavior, they are not the key physics responsible. Furthermore, an important discrepancy in the layer width and force balance between the collisionless regime of MRX and kinetic simulations [2-4] persists when the fluctuations are small or absent, implying that they are not the cause of the wider electron layers observed in the experiment [5]. These wider layers may instead be due to the formation of flux ropes with a wide range of sizes; consistent with this hypothesis, flux rope signatures are observed down to the smallest scales resolved by the diagnostics. Finally, a qualitative, 3-D, two-fluid model is proposed to explain the observed disruptions. Many of the features observed in MRX including current disruptions [6], flux ropes [7], and electromagnetic fluctuations [8] have analogues in space observations. Thus, further detailed comparisons may enhance our understanding

  9. Quantitative 3D magnetic resonance elastography: Comparison with dynamic mechanical analysis

    PubMed Central

    Rossman, Phillip J.; Arani, Arvin; Lake, David S.; Glaser, Kevin J.; Trzasko, Joshua D.; Manduca, Armando; McGee, Kiaran P.; Ehman, Richard L.; Araoz, Philip A.

    2016-01-01

    Purpose Magnetic resonance elastography (MRE) is a rapidly growing noninvasive imaging technique for measuring tissue mechanical properties in vivo. Previous studies have compared two‐dimensional MRE measurements with material properties from dynamic mechanical analysis (DMA) devices that were limited in frequency range. Advanced DMA technology now allows broad frequency range testing, and three‐dimensional (3D) MRE is increasingly common. The purpose of this study was to compare 3D MRE stiffness measurements with those of DMA over a wide range of frequencies and shear stiffnesses. Methods 3D MRE and DMA were performed on eight different polyvinyl chloride samples over 20–205 Hz with stiffness between 3 and 23 kPa. Driving frequencies were chosen to create 1.1, 2.2, 3.3, 4.4, 5.5, and 6.6 effective wavelengths across the diameter of the cylindrical phantoms. Wave images were analyzed using direct inversion and local frequency estimation algorithm with the curl operator and compared with DMA measurements at each corresponding frequency. Samples with sufficient spatial resolution and with an octahedral shear strain signal‐to‐noise ratio > 3 were compared. Results Consistency between the two techniques was measured with the intraclass correlation coefficient (ICC) and was excellent with an overall ICC of 0.99. Conclusions 3D MRE and DMA showed excellent consistency over a wide range of frequencies and stiffnesses. Magn Reson Med 77:1184–1192, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. PMID:27016276

  10. Combined registration of 3D tibia and femur implant models in 3D magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Englmeier, Karl-Hans; Siebert, Markus; von Eisenhart-Rothe, Ruediger; Graichen, Heiko

    2008-03-01

    The most frequent reasons for revision of total knee arthroplasty are loosening and abnormal axial alignment leading to an unphysiological kinematic of the knee implant. To get an idea about the postoperative kinematic of the implant, it is essential to determine the position and orientation of the tibial and femoral prosthesis. Therefore we developed a registration method for fitting 3D CAD-models of knee joint prostheses into an 3D MR image. This rigid registration is the basis for a quantitative analysis of the kinematics of knee implants. Firstly the surface data of the prostheses models are converted into a voxel representation; a recursive algorithm determines all boundary voxels of the original triangular surface data. Secondly an initial preconfiguration of the implants by the user is still necessary for the following step: The user has to perform a rough preconfiguration of both remaining prostheses models, so that the fine matching process gets a reasonable starting point. After that an automated gradient-based fine matching process determines the best absolute position and orientation: This iterative process changes all 6 parameters (3 rotational- and 3 translational parameters) of a model by a minimal amount until a maximum value of the matching function is reached. To examine the spread of the final solutions of the registration, the interobserver variability was measured in a group of testers. This variability, calculated by the relative standard deviation, improved from about 50% (pure manual registration) to 0.5% (rough manual preconfiguration and subsequent fine registration with the automatic fine matching process).

  11. 3D CSEM data inversion using Newton and Halley class methods

    NASA Astrophysics Data System (ADS)

    Amaya, M.; Hansen, K. R.; Morten, J. P.

    2016-05-01

    For the first time in 3D controlled source electromagnetic data inversion, we explore the use of the Newton and the Halley optimization methods, which may show their potential when the cost function has a complex topology. The inversion is formulated as a constrained nonlinear least-squares problem which is solved by iterative optimization. These methods require the derivatives up to second order of the residuals with respect to model parameters. We show how Green's functions determine the high-order derivatives, and develop a diagrammatical representation of the residual derivatives. The Green's functions are efficiently calculated on-the-fly, making use of a finite-difference frequency-domain forward modelling code based on a multi-frontal sparse direct solver. This allow us to build the second-order derivatives of the residuals keeping the memory cost in the same order as in a Gauss-Newton (GN) scheme. Model updates are computed with a trust-region based conjugate-gradient solver which does not require the computation of a stabilizer. We present inversion results for a synthetic survey and compare the GN, Newton, and super-Halley optimization schemes, and consider two different approaches to set the initial trust-region radius. Our analysis shows that the Newton and super-Halley schemes, using the same regularization configuration, add significant information to the inversion so that the convergence is reached by different paths. In our simple resistivity model examples, the convergence speed of the Newton and the super-Halley schemes are either similar or slightly superior with respect to the convergence speed of the GN scheme, close to the minimum of the cost function. Due to the current noise levels and other measurement inaccuracies in geophysical investigations, this advantageous behaviour is at present of low consequence, but may, with the further improvement of geophysical data acquisition, be an argument for more accurate higher-order methods like those

  12. Joint inversion of surface and borehole magnetic amplitude data

    NASA Astrophysics Data System (ADS)

    Li, Zelin; Yao, Changli; Zheng, Yuanman; Yuan, Xiaoyu

    2016-04-01

    3D magnetic inversion for susceptibility distribution is a powerful tool in quantitative interpretation of magnetic data in mineral exploration. However, the inversion and interpretation of such data are faced with two problems. One problem is the poor imaging results of deep sources when only surface data are inverted. The other is the unknown total magnetization directions of sources when strong remanence exists. To deal with these problems simultaneously, we propose a method through the joint inversion of surface and borehole magnetic amplitude data. In this method, we first transform both surface and borehole magnetic data to magnetic amplitude data that are less sensitive to the directions of total magnetization, and then preform a joint inversion of the whole amplitude data to generate a 3D susceptibility distribution. The amplitude inversion algorithm uses Tikhonov regularization and imposes a positivity constraint on the effective susceptibility defined as the ratio of magnetization magnitude over the geomagnetic field strength. In addition, a distance-based weighting function is used to make the algorithm applicable to joint data sets. To solve this positivity-constraint inversion problem efficiently, an appropriate optimization method must be chosen. We first use an interior-point method to incorporate the positivity constraint into the total objective function, and then minimize the objective function via a Gauss-Newton method due to the nonlinearity introduced by the positivity constraint and the amplitude data. To further improve the efficiency of the inversion algorithm, we use a conjugate gradient method to carry out the fast matrix-vector multiplication during the minimization. To verify the utility of the proposed method, we invert the synthetic and field data using three inversion methods, including the joint inversion of surface and borehole three-component magnetic data, the inversion of surface magnetic amplitude data, and the proposed joint

  13. 3D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface

    SciTech Connect

    Levander, Alan Richard; Zelt, Colin A.

    2015-03-17

    The work plan for this project was to develop and apply advanced seismic reflection and wide-angle processing and inversion techniques to high resolution seismic data for the shallow subsurface to seismically characterize the shallow subsurface at hazardous waste sites as an aid to containment and cleanup activities. We proposed to continue work on seismic data that we had already acquired under a previous DoE grant, as well as to acquire additional new datasets for analysis. The project successfully developed and/or implemented the use of 3D reflection seismology algorithms, waveform tomography and finite-frequency tomography using compressional and shear waves for high resolution characterization of the shallow subsurface at two waste sites. These two sites have markedly different near-surface structures, groundwater flow patterns, and hazardous waste problems. This is documented in the list of refereed documents, conference proceedings, and Rice graduate theses, listed below.

  14. The 3D inversion of airborne gamma-ray spectrometric data

    NASA Astrophysics Data System (ADS)

    Minty, Brian; Brodie, Ross

    2016-07-01

    We present a new method for the inversion of airborne gamma-ray spectrometric line data to a regular grid of radioelement concentration estimates on the ground. The method incorporates the height of the aircraft, the 3D terrain within the field of view of the spectrometer, the directional sensitivity of rectangular detectors, and a source model comprising vertical rectangular prisms with the same horizontal dimensions as the required grid cell size. The top of each prism is a plane surface derived from a best-fit plane to the digital elevation model of the earth's surface within each grid cell area. The method is a significant improvement on current methods, and gives superior interpolation between flight lines. It also eliminates terrain effects that would normally remain in the data after the conventional processing of these data assuming a flat-earth model.

  15. A review on the systematic formulation of 3-D multiparameter full waveform inversion in viscoelastic medium

    NASA Astrophysics Data System (ADS)

    Yang, Pengliang; Brossier, Romain; Métivier, Ludovic; Virieux, Jean

    2016-10-01

    In this paper, we study 3-D multiparameter full waveform inversion (FWI) in viscoelastic media based on the generalized Maxwell/Zener body including arbitrary number of attenuation mechanisms. We present a frequency-domain energy analysis to establish the stability condition of a full anisotropic viscoelastic system, according to zero-valued boundary condition and the elastic-viscoelastic correspondence principle: the real-valued stiffness matrix becomes a complex-valued one in Fourier domain when seismic attenuation is taken into account. We develop a least-squares optimization approach to linearly relate the quality factor with the anelastic coefficients by estimating a set of constants which are independent of the spatial coordinates, which supplies an explicit incorporation of the parameter Q in the general viscoelastic wave equation. By introducing the Lagrangian multipliers into the matrix expression of the wave equation with implicit time integration, we build a systematic formulation of multiparameter FWI for full anisotropic viscoelastic wave equation, while the equivalent form of the state and adjoint equation with explicit time integration is available to be resolved efficiently. In particular, this formulation lays the foundation for the inversion of the parameter Q in the time domain with full anisotropic viscoelastic properties. In the 3-D isotropic viscoelastic settings, the anelastic coefficients and the quality factors using bulk and shear moduli parametrization can be related to the counterparts using P and S velocity. Gradients with respect to any other parameter of interest can be found by chain rule. Pioneering numerical validations as well as the real applications of this most generic framework will be carried out to disclose the potential of viscoelastic FWI when adequate high-performance computing resources and the field data are available.

  16. Inverse modeling of InSAR and ground leveling data for 3D volumetric strain distribution

    NASA Astrophysics Data System (ADS)

    Gallardo, L. A.; Glowacka, E.; Sarychikhina, O.

    2015-12-01

    Wide availability of modern Interferometric Synthetic aperture Radar (InSAR) data have made possible the extensive observation of differential surface displacements and are becoming an efficient tool for the detailed monitoring of terrain subsidence associated to reservoir dynamics, volcanic deformation and active tectonism. Unfortunately, this increasing popularity has not been matched by the availability of automated codes to estimate underground deformation, since many of them still rely on trial-error subsurface model building strategies. We posit that an efficient algorithm for the volumetric modeling of differential surface displacements should match the availability of current leveling and InSAR data and have developed an algorithm for the joint inversion of ground leveling and dInSAR data in 3D. We assume the ground displacements are originated by a stress free-volume strain distribution in a homogeneous elastic media and determined the displacement field associated to an ensemble of rectangular prisms. This formulation is then used to develop a 3D conjugate gradient inversion code that searches for the three-dimensional distribution of the volumetric strains that predict InSAR and leveling surface displacements simultaneously. The algorithm is regularized applying discontinuos first and zero order Thikonov constraints. For efficiency, the resulting computational code takes advantage of the resulting convolution integral associated to the deformation field and some basic tools for multithreading parallelization. We extensively test our algorithm on leveling and InSAR test and field data of the Northwest of Mexico and compare to some feasible geological scenarios of underground deformation.

  17. Review on applications of 3D inverse design method for pump

    NASA Astrophysics Data System (ADS)

    Yin, Junlian; Wang, Dezhong

    2014-05-01

    The 3D inverse design method, which methodology is far superior to the conventional design method that based on geometrical description, is gradually applied in pump blade design. However, no complete description about the method is outlined. Also, there are no general rules available to set the two important input parameters, blade loading distribution and stacking condition. In this sense, the basic theory and the mechanism why the design method can suppress the formation of secondary flow are summarized. And also, several typical pump design cases with different specific speeds ranging from centrifugal pump to axial pump are surveyed. The results indicates that, for centrifugal pump and mixed pump or turbine, the ratio of blade loading on the hub to that on the shroud is more than unit in the fore part of the blade, whereas in the aft part, the ratio is decreased to satisfy the same wrap angle for hub and shroud. And the choice of blade loading type depends on the balancing of efficiency and cavitation. If the cavitation is more weighted, the better choice is aft-loaded, otherwise, the fore-loaded or mid-loaded is preferable to improve the efficiency. The stacking condition, which is an auxiliary to suppress the secondary flow, can have great effect on the jet-wake outflow and the operation range for pump. Ultimately, how to link the design method to modern optimization techniques is illustrated. With the know-how design methodology and the know-how systematic optimization approach, the application of optimization design is promising for engineering. This paper summarizes the 3D inverse design method systematically.

  18. 3D elastic full waveform inversion: case study from a land seismic survey

    NASA Astrophysics Data System (ADS)

    Kormann, Jean; Marti, David; Rodriguez, Juan-Esteban; Marzan, Ignacio; Ferrer, Miguel; Gutierrez, Natalia; Farres, Albert; Hanzich, Mauricio; de la Puente, Josep; Carbonell, Ramon

    2016-04-01

    Full Waveform Inversion (FWI) is one of the most advanced processing methods that is recently reaching a mature state after years of solving theoretical and technical issues such as the non-uniqueness of the solution and harnessing the huge computational power required by realistic scenarios. BSIT (Barcelona Subsurface Imaging Tools, www.bsc.es/bsit) includes a FWI algorithm that can tackle with very complex problems involving large datasets. We present here the application of this system to a 3D dataset acquired to constrain the shallow subsurface. This is where the wavefield is the most complicated, because most of the wavefield conversions takes place in the shallow region and also because the media is much more laterally heterogeneous. With this in mind, at least isotropic elastic approximation would be suitable as kernel engine for FWI. The current study explores the possibilities to apply elastic isotropic FWI using only the vertical component of the recorded seismograms. The survey covers an area of 500×500 m2, and consists in a receivers grid of 10 m×20 m combined with a 250 kg accelerated weight-drop as source on a displaced grid of 20 m×20 m. One of the main challenges in this case study is the costly 3D modeling that includes topography and substantial free surface effects. FWI is applied to a data subset (shooting lines 4 to 12), and is performed for 3 frequencies ranging from 15 to 25 Hz. The starting models are obtained from travel-time tomography and the all computation is run on 75 nodes of Mare Nostrum supercomputer during 3 days. The resulting models provide a higher resolution of the subsurface structures, and show a good correlation with the available borehole measurements. FWI allows to extend in a reliable way this 1D knowledge (borehole) to 3D.

  19. Inverse cascades sustained by the transfer rate of angular momentum in a 3D turbulent flow

    NASA Astrophysics Data System (ADS)

    Burguete, Javier; Lopez-Caballero, Miguel

    2013-11-01

    The existence of energy cascades as signatures of conserved magnitudes is one of the universal characteristics of turbulent flows. In this work we present the evidence of an inverse cascade in a fully developed 3D experimental turbulent flow where the conserved magnitude is the angular momentum. We analyze the behavior of a fluid in a closed cavity where two inhomogeneous and strongly turbulent flows collide in a thin region. The experimental volume is a closed cylinder (diameter of 20 cm) where two impellers rotate in opposite directions. A key characteristic of this setup the high stability of the propellers (the instantaneous fluctuations are below 0 . 1 %). We have performed PIV and LDA measurements of the velocity fields. Typical characteristics of the turbulent flow in this setup are: turbulence intensity 50 % , the Reλ = 900 , the Taylor microscale λT = 1 . 8 mm and the integral scale LI = 15 mm. The analysis of the data series reveal that below the injection scales an inverse cascade can be identified (-1/3 in time, -7/3 in space) that can be explained as the transfer of angular momentum between the diferent fluid layers. A. de la Torre, J. Burguete, Phys Rev Lett 99 (2007) 054101. M. Lopez-Caballero, J. Burguete, Phys Rev Lett 110 (2013) 124501.

  20. KOALA: 3-D shape of asteroids from multi-data inversion

    NASA Astrophysics Data System (ADS)

    Carry, B.; Kaasalainen, M.; Merline, W. J.; Drummond, J. D.; Durech, J.; Berthier, J.; Conrad, A.

    2011-10-01

    We describe our on-going observing program to determine the physical properties of asteroids from groundbased facilities. We combine disk-resolved images from adaptive optics, optical lightcurves, and stellar occultations to put tighter constraints on the spin, 3-D shape, and size of asteroids. We will discuss the relevance of the determination of physical properties to help understand the asteroid population (e.g., density, composition, and non-gravitational forces). We will then briefly describe our multi-data inversion algorithm KOALA (Carry et al. 2010a, Kaasalainen 2011, see also Kaasalainen et al., same meeting), which allows the determination of certain physical properties of an asteroid from the combination of different techniques of observation. A comparison of results obtained with KOALA on asteroid (21) Lutetia, prior to the ESA Rosetta flyby, with the high spatial resolution images returned from that flyby, will then be presented, showing the high accuracy of KOALA inversion. Finally, we will describe our current development of the algorithm, and focus on examples of other asteroids currently being studied with KOALA.

  1. An optimal transport approach for seismic tomography: application to 3D full waveform inversion

    NASA Astrophysics Data System (ADS)

    Métivier, L.; Brossier, R.; Mérigot, Q.; Oudet, E.; Virieux, J.

    2016-11-01

    the L 2 distance, in 2D and 3D contexts.

  2. Centroid Moment Tensor Inversion in a 3D heterogeneous Earth: Application to the Australasian region

    NASA Astrophysics Data System (ADS)

    Hejrani, B.; Tkalcic, H.; Fichtner, A.

    2015-12-01

    radially anisotropic structure: new insights into present and past states of the Australasian upper mantle. Earth Planet. Sci. Lett. 290, 270-280. Hingee, M., Tkalčić, H., Fichtner A., Sambridge, M., 2011. Moment tensor inversion using a 3-D structural model: Applications for the Australian region, Geophys. J. Int., 184(2), 949-964.

  3. Inverse magnetic/shear catalysis

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2016-05-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ;inverse magnetic catalysis;, signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials.

  4. A Compressive Sensing Approach for 3D Breast Cancer Microwave Imaging With Magnetic Nanoparticles as Contrast Agent.

    PubMed

    Bevacqua, Martina T; Scapaticci, Rosa

    2016-02-01

    In microwave breast cancer imaging magnetic nanoparticles have been recently proposed as contrast agent. Due to the non-magnetic nature of human tissues, magnetic nanoparticles make possible the overcoming of some limitations of conventional microwave imaging techniques, thus providing reliable and specific diagnosis of breast cancer. In this paper, a Compressive Sensing inspired inversion technique is introduced for the reconstruction of the magnetic contrast induced within the tumor. The applicability of Compressive Sensing theory is guaranteed by the fact that the underlying inverse scattering problem is linear and the searched magnetic perturbation is sparse. From the numerical analysis, performed in realistic conditions in 3D geometry, it has been pointed out that the adoption of this new tool allows improving resolution and accuracy of the reconstructions, as well as reducing the number of required measurements.

  5. New results on the resistivity structure of Merapi Volcano(Indonesia), derived from 3D restricted inversion of long-offsettransient electromagnetic data

    SciTech Connect

    Commer, Michael; Helwig, Stefan, L.; Hordt, Andreas; Scholl,Carsten; Tezkan, Bulent

    2006-06-14

    Three long-offset transient electromagnetic (LOTEM) surveyswerecarried out at the active volcano Merapi in Central Java (Indonesia)during the years 1998, 2000, and 2001. The measurements focused on thegeneral resistivity structure of the volcanic edifice at depths of 0.5-2km and the further investigation of a southside anomaly. The measurementswere insufficient for a full 3D inversion scheme, which could enable theimaging of finely discretized resistivity distributions. Therefore, astable, damped least-squares joint-inversion approach is used to optimize3D models with a limited number of parameters. The mode ls feature therealistic simulation of topography, a layered background structure, andadditional coarse 3D blocks representing conductivity anomalies.Twenty-eight LOTEM transients, comprising both horizontal and verticalcomponents of the magnetic induction time derivative, were analyzed. Inview of the few unknowns, we were able to achieve reasonable data fits.The inversion results indicate an upwelling conductor below the summit,suggesting hydrothermal activity in the central volcanic complex. Ashallow conductor due to a magma-filled chamber, at depths down to 1 kmbelow the summit, suggested by earlier seismic studies, is not indicatedby the inversion results. In conjunction with an anomalous-density model,derived from arecent gravity study, our inversion results provideinformation about the southern geological structure resulting from amajor sector collapse during the Middle Merapi period. The density modelallows to assess a porosity range andthus an estimated vertical salinityprofile to explain the high conductivities on a larger scale, extendingbeyond the foothills of Merapi.

  6. Improved water and lipid suppression for 3D PRESS CSI using RF band selective inversion with gradient dephasing (BASING).

    PubMed

    Star-Lack, J; Nelson, S J; Kurhanewicz, J; Huang, L R; Vigneron, D B

    1997-08-01

    A T1 insensitive solvent suppression technique-band selective inversion with gradient dephasing (BASING)-was developed to suppress water and lipids for 1H magnetic resonance spectroscopy (MRS). BASING, which consists of a frequency selective RF inversion pulse surrounded by spoiler gradient pulses of opposite signs, was used to dephase stopband resonances and minimally impact passband metabolites. Passband phase linearity was achieved with a dual BASING scheme. Using the Shinnar-Le Roux algorithm, a highpass filter was designed to suppress water and rephase the lactate methyl doublet independently of TE, and water/lipid bandstop filters were designed for the brain and prostate. Phantom and in vivo experimental 3D PRESS CSI data were acquired at 1.5 T to compare BASING with CHESS and STIR suppression. With BASING, the measured suppression factor was over 100 times higher than with CHESS or STIR causing baseline distortions to be removed. It was shown that BASING can be incorporated into a variety of sequences to offer improved suppression in the presence of B1 and T1 inhomogeneites.

  7. Understanding how Fault-bounded Blocks Deform in 3D by Inverse Modelling

    NASA Astrophysics Data System (ADS)

    Jouen, G.; White, N.

    2004-05-01

    Normal faults play a crucial role in modifying basin stratigraphy. At the exploration scale, the internal deformation of tilted blocks is governed by the three-dimensional geometry of large-scale faults which bound these blocks. At the reservoir scale, the geometry and growth of normal faulting control the deformation of strata and the compartmentalisation of reservoir intervals. Despite their importance, large-scale normal faults are often difficult to image. The purpose of structural validation is two-fold: to determine the 3D shape of normal faults and to investigate the relationship between fault geometry and deformed stratigraphy including the intra-block faults. We have developed methods for tackling structural validation at a variety of scales in two and three dimensions. The cornerstone of our approach is the use of geophysical inverse theory to calculate optimal fault geometries from deformed strata. This approach allows us to focus on key questions: does a solution exist? Are there several possible solutions or just one unique one? In a complex normal fault system, which part of the fault controls the motion responsible for the deformation in the hanging-wall? Traditional forward modelling cannot answer these fundamental issues. We have applied the inversion on seismic data in particularly complex areas in the northern North Sea. The aims of this project are to determine the geometry of the basin-bounding fault, to assess the likelihood of out-of-plane motion as well as understanding the mode of deformation leading to the complexity of the present structure. Closely spaced inverse models show that the basin-bounding fault on the UK side is steeper and more planar than previously thought. This method also helped us to have a better view of what could have been the cause of the organisation and density of the intra-block faulting where it occurs. The North Cormorant study has shown how inverse modelling can yield important, quantitative, insights. Our

  8. Dirac Circles and Quantum Hall Effect in 3D Inversion-Symmetric Crystals

    NASA Astrophysics Data System (ADS)

    Wieder, Benjamin J.; Kim, Youngkuk; Kane, C. L.

    2015-03-01

    In the presence of inversion and time-reversal symmetries, materials with weak spin-orbit coupling may host topologically protected Dirac line nodes. A band inversion transition in these systems can produce a line node which closes on itself and forms a protected Dirac circle. The surfaces parallel to this circle host zero-energy puddles in momentum space which are flat if the inverting bands have the same effective mass. In cases with differing effective masses, the surface modes disperse, but the bulk Dirac circle remains gapless. Adding an external magnetic field perpendicular to this circle creates surface Landau levels, whose number can be controlled by tuning the field strength. When a new level is created or destroyed, the bulk becomes gapless and the zero-temperature bulk conductivity displays a sharp peak. The sequence of conductivity peaks describes an unusual manifestation of the integer quantum hall effect. We characterize surface and bulk transport as a function of magnetic field strength and in the presence of disorder.

  9. Simultaneous inversion of 3D velocity structure, hypocenter locations, and reflector geometry in Cascadia

    NASA Astrophysics Data System (ADS)

    Preston, Leiph Alexander

    We develop and apply a non-linear inversion of direct and wide-angle reflection travel times for 3-D P-wave velocity structure, earthquake hypocenters, and reflector geometry under NW Washington focusing on the structure of the subducting Juan de Fuca plate. The first-arrival travel times are derived from both active-source experiments and from local earthquakes. The reflection arrivals were picked from data collected during the 1998 Wet SHIPS active-source experiment, which consisted of air-gun sources within the inland water-ways of NW Washington and SW British Columbia to land-based stations. Our inversion procedure reduces the well-known trade-off between reflector position and the velocities above it by the combination of simultaneous inversion and adequate crossing paths. We interpret the wide-angle reflector as the Moho of the subducting Juan de Fuca slab. The relocated intraslab earthquakes separate into two groups: those located up-dip of the 45km reflector depth contour generally lie below the reflector in material whose velocity exceeds 7.7km/s, placing them within the subducting mantle, while those down-dip of this contour occur within material whose velocities are 6.8--7.5km/s, placing them within subducted oceanic crust. We interpret these groups of earthquakes as resulting from serpentine dehydration in the subducted mantle and the basalt to eclogite transformation in the subducted crust. We have performed velocity checkerboard, slab velocity resolution, and parameter sensitivity tests to estimate our ability to resolve the relationship among the reflector, intraslab hypocenters, and slab velocity structure. These tests indicate we have the necessary resolvability and can distinguish the relative locations among the velocities, reflector, and intraslab hypocenters within the subducting slab to +/-2km. The occurrence of events within the subducted mantle geometrically allows for larger magnitude earthquakes than could occur if they were confined to

  10. Statistical Inverse Ray Tracing for Image-Based 3D Modeling.

    PubMed

    Liu, Shubao; Cooper, David B

    2014-10-01

    This paper proposes a new formulation and solution to image-based 3D modeling (aka "multi-view stereo") based on generative statistical modeling and inference. The proposed new approach, named statistical inverse ray tracing, models and estimates the occlusion relationship accurately through optimizing a physically sound image generation model based on volumetric ray tracing. Together with geometric priors, they are put together into a Bayesian formulation known as Markov random field (MRF) model. This MRF model is different from typical MRFs used in image analysis in the sense that the ray clique, which models the ray-tracing process, consists of thousands of random variables instead of two to dozens. To handle the computational challenges associated with large clique size, an algorithm with linear computational complexity is developed by exploiting, using dynamic programming, the recursive chain structure of the ray clique. We further demonstrate the benefit of exact modeling and accurate estimation of the occlusion relationship by evaluating the proposed algorithm on several challenging data sets.

  11. Magnetic reconnection in 3D magnetosphere models: magnetic separators and open flux production

    NASA Astrophysics Data System (ADS)

    Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P.

    2014-12-01

    There are multiple competing definitions of magnetic reconnection in 3D (e.g., Hesse and Schindler [1988], Lau and Finn [1990], and Boozer [2002]). In this work we focus on separator reconnection. A magnetic separator can be understood as the 3D analogue of a 2D x line with a guide field, and is defined by the line corresponding to the intersection of the separatrix surfaces associated with the magnetic nulls. A separator in the magnetosphere represents the intersection of four distinct magnetic topologies: solar wind, closed, open connected to the northern hemisphere, and open connected to the southern hemisphere. The integral of the parallel electric field along the separator defines the rate of open flux production, and is one measure of the reconnection rate. We present three methods for locating magnetic separators and apply them to 3D resistive MHD simulations of the Earth's magnetosphere using the BATS-R-US code. The techniques for finding separators and determining the reconnection rate are insensitive to IMF clock angle and can in principle be applied to any magnetospheric model. The present work examines cases of high and low resistivity, for two clock angles. We also examine the separator during Flux Transfer Events (FTEs) and Kelvin-Helmholtz instability.

  12. 3D near-to-surface conductivity reconstruction by inversion of VETEM data using the distorted Born iterative method

    USGS Publications Warehouse

    Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.

    2004-01-01

    Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.

  13. Optimization of a Hybrid Magnetic Bearing for a Magnetically Levitated Blood Pump via 3-D FEA

    PubMed Central

    Cheng, Shanbao; Olles, Mark W.; Burger, Aaron F.; Day, Steven W.

    2011-01-01

    In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, three-dimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified by experimental results. As compared with the original design, the optimized HMB had twice the axial stiffness with the resulting increase of negative radial stiffness partially compensated for by increased current stiffness. Accordingly, the performance of the maglev axial flow blood pump with the optimized HMBs was improved: the maximum pump speed was increased from 6000 rpm to 9000 rpm (50%). The radial, axial and current stiffness of the HMB was found to be linear at nominal operational position from both 3-D FEA and empirical measurements. Stiffness values determined by FEA and empirical measurements agreed well with one another. The magnetic flux density distribution and flux loop of the HMB were also visualized via 3-D FEA which confirms the designers’ initial assumption about the function of this HMB. PMID:22065892

  14. Optimization of a Hybrid Magnetic Bearing for a Magnetically Levitated Blood Pump via 3-D FEA.

    PubMed

    Cheng, Shanbao; Olles, Mark W; Burger, Aaron F; Day, Steven W

    2011-10-01

    In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, three-dimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified by experimental results. As compared with the original design, the optimized HMB had twice the axial stiffness with the resulting increase of negative radial stiffness partially compensated for by increased current stiffness. Accordingly, the performance of the maglev axial flow blood pump with the optimized HMBs was improved: the maximum pump speed was increased from 6000 rpm to 9000 rpm (50%). The radial, axial and current stiffness of the HMB was found to be linear at nominal operational position from both 3-D FEA and empirical measurements. Stiffness values determined by FEA and empirical measurements agreed well with one another. The magnetic flux density distribution and flux loop of the HMB were also visualized via 3-D FEA which confirms the designers' initial assumption about the function of this HMB.

  15. Effects of 3D Toroidally Asymmetric Magnetic Field on Tokamak Magnetic Surfaces

    NASA Astrophysics Data System (ADS)

    Lao, L. L.

    2005-10-01

    The effects of 3D error magnetic field on magnetic surfaces are investigated using the DIII-D internal coils (I-Coils). Slowly rotating n=1 traveling waves at 5 Hz and various amplitudes were applied to systematically perturb the edge surfaces by programming the I-Coil currents. The vertical separatrix location difference between EFIT magnetic reconstructions that assumes toroidal symmetry and Thomson scattering Te measurements responds in phase to the applied perturbed field. The oscillation amplitudes increase with the strength of the applied field but are much smaller than those expected from the applied field alone. The results indicate that plasma response is important. Various plasma response models based on results from the MHD codes MARS and GATO are being developed and compared to the experimental observations. To more accurately evaluate the effects of magnetic measurement errors, a new form of the magnetic uncertainty matrix is also being implemented into EFIT. Details will be presented.

  16. DIII-D Equilibrium Reconstructions with New 3D Magnetic Probes

    NASA Astrophysics Data System (ADS)

    Lao, Lang; Strait, E. J.; Ferraro, N. M.; Ferron, J. R.; King, J. D.; Lee, X.; Meneghini, O.; Turnbull, A. D.; Huang, Y.; Qian, J. G.; Wingen, A.

    2015-11-01

    DIII-D equilibrium reconstructions with the recently installed new 3D magnetic diagnostic are presented. In addition to providing information to allow more accurate 2D reconstructions, the new 3D probes also provide useful information to guide computation of 3D perturbed equilibria. A new more comprehensive magnetic compensation has been implemented. Algorithms are being developed to allow EFIT to reconstruct 3D perturbed equilibria making use of the new 3D probes and plasma responses from 3D MHD codes such as GATO and M3D-C1. To improve the computation efficiency, all inactive probes in one of the toroidal planes in EFIT have been replaced with new probes from other planes. Other 3D efforts include testing of 3D reconstructions using V3FIT and a new 3D variational moment equilibrium code VMOM3D. Other EFIT developments include a GPU EFIT version and new safety factor and MSE-LS constraints. The accuracy and limitation of the new probes for 3D reconstructions will be discussed. Supported by US DOE under DE-FC02-04ER54698 and DE-FG02-95ER54309.

  17. Regional conductivity structure of Cascadia from 3D inversion of USArray magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Egbert, G. D.; Patro, P. K.

    2008-12-01

    Magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental US through EMScope, a part of the USArray component of EarthScope. Initial deployments in 2006 and 2007 acquired data at 110 sites covering the US Pacific Northwest. The MT sites, distributed with the same nominal spacing as the USArray seismic transportable array (~75 km), produced data in the period range 10- 20,000s of very good to excellent quality. The most striking and robust feature revealed by 3D inversion of this dataset is an extensive lower crustal conductor covering most of the study area southeast of a line running from the California border at the coast to the Blue Mountains of Northeastern Oregon. The conductance of this layer, which is about 15 km thick with a top at roughly 20 km depth, exceeds 3000 S beneath the he Northwest Basin and Range (BR) province of southeastern Oregon. The high conductivity in this region is inferred to result from fluids - including possibly partial melt at depth - associated with magmatic underplating and BR extension. The lower crust is much more resistive beneath the Coast Range, Willamette Valley and Puget Lowlands of Western Washington and Oregon, and beneath the Columbia Plateau. This area of resistive crust, which was derived from a large fragment of thickened oceanic lithosphere that was accreted to North America at approximately 48 Ma ("Siletzia"), is revealed by geological and geodetic studies to be strong, accommodating tectonic stresses through rigid block rotations. In contrast, the area to the southeast characterized by high conductivity in the lower crust is actively deforming, consistent with an important role for fluids in weakening of continental crust. The resistive Siletzia crust is broken by an elongated N-S zone of high conductivity beneath the Cascade volcanoes. High conductivities beneath the volcanoes also most likely reflect the presence of interconnected fluids, in this case released

  18. Fast 3D fluid registration of brain magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Leporé, Natasha; Chou, Yi-Yu; Lopez, Oscar L.; Aizenstein, Howard J.; Becker, James T.; Toga, Arthur W.; Thompson, Paul M.

    2008-03-01

    Fluid registration is widely used in medical imaging to track anatomical changes, to correct image distortions, and to integrate multi-modality data. Fluid mappings guarantee that the template image deforms smoothly into the target, without tearing or folding, even when large deformations are required for accurate matching. Here we implemented an intensity-based fluid registration algorithm, accelerated by using a filter designed by Bro-Nielsen and Gramkow. We validated the algorithm on 2D and 3D geometric phantoms using the mean square difference between the final registered image and target as a measure of the accuracy of the registration. In tests on phantom images with different levels of overlap, varying amounts of Gaussian noise, and different intensity gradients, the fluid method outperformed a more commonly used elastic registration method, both in terms of accuracy and in avoiding topological errors during deformation. We also studied the effect of varying the viscosity coefficients in the viscous fluid equation, to optimize registration accuracy. Finally, we applied the fluid registration algorithm to a dataset of 2D binary corpus callosum images and 3D volumetric brain MRIs from 14 healthy individuals to assess its accuracy and robustness.

  19. Contiguous 3 d and 4 f Magnetism: Strongly Correlated 3 d Electrons in YbFe2Al10

    NASA Astrophysics Data System (ADS)

    Khuntia, P.; Peratheepan, P.; Strydom, A. M.; Utsumi, Y.; Ko, K.-T.; Tsuei, K.-D.; Tjeng, L. H.; Steglich, F.; Baenitz, M.

    2014-11-01

    We present magnetization, specific heat, and Al 27 NMR investigations on YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a ln (T0/T ) divergence of the low-T specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard-x-ray photoemission spectroscopy study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, Yb3 + carries a full and stable moment, and Fe carries a moment of about 3.1 μB. The enhanced value of the Sommerfeld-Wilson ratio and the dynamic scaling of the spin-lattice relaxation rate divided by T [(1 /T1T ) 27 ] with static susceptibility suggests admixed ferromagnetic correlations. (1 /T1T ) 27 simultaneously tracks the valence fluctuations from the 4 f Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe 3 d moments at low temperature; the latter evolve out of an Yb 4 f admixed conduction band.

  20. A 3D Current Loop Model of Magnetic Clouds

    NASA Astrophysics Data System (ADS)

    Chen, James

    1992-05-01

    A magnetohydrodynamic (MHD) model is developed to study magnetic clouds (Burlaga et al. 1981). In this model, magnetic clouds observed near 1 AU are treated as a consequence of eruptive solar current loops. It is shown that current loops intially in MHD equilibrium can be triggered to rise rapidly, propelling material of up to 10(16) g at up to ~ 1000 km s(-1) and dissipating ~ 10(32) erg of magnetic energy in tens of minutes. The initial rise profile is consistent with observed height-time profiles of erupting filaments (Kahler et al. 1988). Two triggering mechanisms for eruption are suggested: (1)subphotospheric energy storage and trigger and (2) in situ (coronal) energy storage and trigger. In the former, eruption occurs as a result of changes in the subphotospheric magnetic topology and subsequent relaxation to a new equilibrium. In the latter, the current loop can evolve to exceed a local maximum in the magnetic potential associated with the ambient magnetic fields. The former scenario leads to more energetic and longer-lasting eruption than the latter. Burlaga, L. F., Sittler, E., Mariani, F., and Schwenn, R. 1981, J. Geophys. Res., 86, 6673. Kahler, S. W., Moore, R. L., Kane, S. R., and Zirin, H. 1988, Ap. J., 328, 824.

  1. A symmetric, triply interlaced 3-D anionic MOF that exhibits both magnetic order and SMM behaviour.

    PubMed

    Campo, J; Falvello, L R; Forcén-Vázquez, E; Sáenz de Pipaón, C; Palacio, F; Tomás, M

    2016-11-14

    A newly prepared 3-D polymer of cobalt citrate cubanes bridged by high-spin Co(ii) centres displays both single-molecule magnet (SMM) behaviour and magnetic ordering. Triple interpenetration of the 3-D diamondoid polymers yields a crystalline solid with channels that host cations and free water molecules, with the SMM behaviour of the Co4O4 cores preserved. The octahedrally coordinated Co(ii) bridges are implicated in the onset of magnetic order at an experimentally accessible temperature.

  2. A Magnetic Diagnostic Code for 3D Fusion Equilibria

    SciTech Connect

    Samuel A. Lazerson, S. Sakakibara and Y. Suzuki

    2013-03-12

    A synthetic magnetic diagnostics code for fusion equilibria is presented. This code calculates the response of various magnetic diagnostics to the equilibria produced by the VMEC and PIES codes. This allows for treatment of equilibria with both good nested flux surfaces and those with stochastic regions. DIAGNO v2.0 builds upon previous codes through the implementation of a virtual casing principle. The code is validated against a vacuum shot on the Large Helical Device (LHD) where the vertical field was ramped. As an exercise of the code, the diagnostic response for various equilibria are calculated on the LHD.

  3. Creating bio-inspired hierarchical 3D-2D photonic stacks via planar lithography on self-assembled inverse opals.

    PubMed

    Burgess, Ian B; Aizenberg, Joanna; Lončar, Marko

    2013-12-01

    Structural hierarchy and complex 3D architecture are characteristics of biological photonic designs that are challenging to reproduce in synthetic materials. Top-down lithography allows for designer patterning of arbitrary shapes, but is largely restricted to planar 2D structures. Self-assembly techniques facilitate easy fabrication of 3D photonic crystals, but controllable defect-integration is difficult. In this paper we combine the advantages of top-down and bottom-up fabrication, developing two techniques to deposit 2D-lithographically-patterned planar layers on top of or in between inverse-opal 3D photonic crystals and creating hierarchical structures that resemble the architecture of the bright green wing scales of the butterfly, Parides sesostris. These fabrication procedures, combining advantages of both top-down and bottom-up fabrication, may prove useful in the development of omnidirectional coloration elements and 3D-2D photonic crystal devices.

  4. GPU-accelerated denoising of 3D magnetic resonance images

    SciTech Connect

    Howison, Mark; Wes Bethel, E.

    2014-05-29

    The raw computational power of GPU accelerators enables fast denoising of 3D MR images using bilateral filtering, anisotropic diffusion, and non-local means. In practice, applying these filtering operations requires setting multiple parameters. This study was designed to provide better guidance to practitioners for choosing the most appropriate parameters by answering two questions: what parameters yield the best denoising results in practice? And what tuning is necessary to achieve optimal performance on a modern GPU? To answer the first question, we use two different metrics, mean squared error (MSE) and mean structural similarity (MSSIM), to compare denoising quality against a reference image. Surprisingly, the best improvement in structural similarity with the bilateral filter is achieved with a small stencil size that lies within the range of real-time execution on an NVIDIA Tesla M2050 GPU. Moreover, inappropriate choices for parameters, especially scaling parameters, can yield very poor denoising performance. To answer the second question, we perform an autotuning study to empirically determine optimal memory tiling on the GPU. The variation in these results suggests that such tuning is an essential step in achieving real-time performance. These results have important implications for the real-time application of denoising to MR images in clinical settings that require fast turn-around times.

  5. A new model of the Arctic crustal thickness from 3D gravity inversion

    NASA Astrophysics Data System (ADS)

    Lebedeva-Ivanova, N. N.; Gaina, C.; Minakov, A.; Kashubin, S.

    2015-12-01

    The remarkable increase of new data collections and compilations for the Arctic region during the last decade motivate for a re-evaluation of our knowledge about the crustal structure and the tectonic evolution of the Arctic basins. 3D forward and inverse gravity modelling methods in the spectral domain (Minakov et al. 2012); lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density are integrated in the algorithm for derive the crustal thickness of the High Arctic region. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2015) was modified according to the most recent published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. Derived crustal thickness and Moho depth grids cover the area northward from 66° N and fit within a few kilometres with seismic crustal models for the most parts of the High Arctic region. Greater misfit in Moho depth between our results and seismic study (Chain & Lebedeva-Ivanova, 2015) under the northern Canada Basin suggest exceptional property of crust or/and mantel in this part of the Basin. Assumed mantle density of 3.25 kg/cm3provide the best fit for the region; it may indicate pervasive subcontinental lithospheric mantle (Goldstein et al., 2008) under the whole Arctic region. New results show a possible crustal connection between the Alpha and the Lomonosov ridges near the Canadian margin. The deepest Moho depth of c.34 km for Alpha-Mendeleev Ridge System is observed under the southern Mendeleev Ridge. The derived crustal thickness and Moho depth show a substantial improvement from the publicly available grids (CRUST1 (Laske et al., 2013

  6. 3D inversion of full gravity gradient tensor data using SL0 sparse recovery

    NASA Astrophysics Data System (ADS)

    Meng, Zhaohai

    2016-04-01

    We present a new method dedicated to the interpretation of full gravity gradient tensor data, based on SL0 sparse recovery inversion. The SL0 sparse recovery method aims to find out the minimum value of the objective function to fit the data function and to solve the non-zero solution to the objective function. Based on continuous iteration, we can easily obtain the final global minimum (namely the property and space attribute of the inversion target). We consider which type of tensor data combination produces the best inversion results based on the inversion results of different full gravity gradient tensor data combinations (separate tensor data and combined tensor data). We compare the recovered models obtained by inverting the different combinations of different gravity gradient tensor components to understand how different component combinations contribute to the resolution of the recovered model. Based on the comparison between the SL0 sparse recovery inversion results and the smoothest and focusing inversion results of the full gravity gradient tensor data, we show that SL0 sparse recovery inversion can obtain more stable and efficient inversion results with relatively sharp edge information, and that this method can also produce a stable solution of the inverse problem for complex geological structures. This new method to resolve very large full gravity gradient tensor datasets has the considerable advantage of being highly efficient; the full gravity gradient tensor inversion requires very little time. This new method is very effective in explaining the full gravity tensor which is very sensitive to small changes in local anomaly. The numerical simulation and inversion results of the compositional model indicates that including multiple components for inversion increases the resolution of the recovered density model and improves the structure delineation. We apply our inversion method to invert the gravity gradient tensor survey data from the Vinton salt

  7. Direct-write 3D printing of NdFeB bonded magnets

    DOE PAGES

    Compton, Brett Gibson; Kemp, James William; Novikov, Timofei V.; ...

    2016-08-17

    We report a method to fabricate Nd-Fe-B bonded magnets of complex shape via extrusion-based additive manufacturing (AM), also known as 3D-printing. We have successfully formulated a 3D-printable epoxy-based ink for direct-write AM with anisotropic MQA NdFeB magnet particles that can be deposited at room temperature. The new feedstocks contain up to 40 vol.% MQA anisotropic Nd-Fe-B magnet particles, and they are shown to remain uniformly dispersed in the thermoset matrix throughout the deposition process. Ring, bar, and horseshoe-type 3D magnet structures were printed and cured in air at 100°C without degrading the magnetic properties. Lastly, this study provides a newmore » pathway for fabricating Nd-Fe-B bonded magnets with complex geometry at low temperature, and presents new opportunities for fabricating multifunctional hybrid structures and devices.« less

  8. Direct-write 3D printing of NdFeB bonded magnets

    SciTech Connect

    Compton, Brett Gibson; Kemp, James William; Novikov, Timofei V.; Pack, Robert Cody; Nlebedim, Cajetan I.; Duty, Chad Edward; Rios, Orlando; Paranthaman, M. Parans

    2016-08-17

    We report a method to fabricate Nd-Fe-B bonded magnets of complex shape via extrusion-based additive manufacturing (AM), also known as 3D-printing. We have successfully formulated a 3D-printable epoxy-based ink for direct-write AM with anisotropic MQA NdFeB magnet particles that can be deposited at room temperature. The new feedstocks contain up to 40 vol.% MQA anisotropic Nd-Fe-B magnet particles, and they are shown to remain uniformly dispersed in the thermoset matrix throughout the deposition process. Ring, bar, and horseshoe-type 3D magnet structures were printed and cured in air at 100°C without degrading the magnetic properties. Lastly, this study provides a new pathway for fabricating Nd-Fe-B bonded magnets with complex geometry at low temperature, and presents new opportunities for fabricating multifunctional hybrid structures and devices.

  9. Statistical Flux Tube Properties of 3D Magnetic Carpet Fields

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Mackay, D. H.; Priest, E. R.

    2003-02-01

    The quiet-Sun photosphere consists of numerous magnetic flux fragments of both polarities that evolve with granular and supergranular flow fields. These concentrations give rise to a web of intermingled magnetic flux tubes which characterise the coronal magnetic field. Here, the nature of these flux tubes is studied. The photosphere is taken to be the source plane and each photospheric fragment is represented by a series of point sources. By analysing the potential field produced by these sources, it is found that the distribution of flux tube lengths obtained by (i) integrating forward from positive sources and (ii) tracing back from negative sources is highly dependent on the total flux imbalance within the region of interest. It is established that the relation between the footpoint separation of a flux tube and its height cannot be assumed to be linear. Where there is a significant imbalance of flux within a region, it is found that fragments of the dominant polarity will have noticeably more connections, on average, than the minority polarity fragments. Despite this difference, the flux from a single fragment of either polarity is typically divided such that (i) 60-70% connects to one opposite-polarity fragment, (ii) 25-30% goes to a further 1 to 2 opposite-polarity fragments, and (iii) any remaining flux may connect to as many as another 50 or more other opposite-polarity fragments. This is true regardless of any flux imbalance within the region. It is found that fragments connect preferentially to their nearest neighbours, with, on average, around 60-70% of flux closing down within 10 Mm of a typical fragment. Only 50% of the flux in a quiet region extends higher than 2.5 Mm above the solar surface and 5-10% extends higher than 25 Mm. The fragments that contribute to the field above this height cover a range of sizes, with even the smallest of fragments contributing to the field at heights of over 50 Mm.

  10. Imaging solar coronal magnetic structures in 3D

    NASA Astrophysics Data System (ADS)

    Cartledge, N. P.

    The study of solar coronal structures and, in particular prominences, is a key part of understanding the highly complex physical mechanisms occurring in the Sun's atmosphere. Solar prominences are important in their own right and some of the most puzzling questions in solar theory have arisen through their study. For example, how do they form and how is their mass continuously replenished? How can the magnetic field provide their continuous support against gravity over time periods of several months? How can such cool, dense material exist in thermal equilibrium in the surrounding coronal environment? Why do they erupt? A study of their structure and that of the surrounding medium is important in determining the nature of the coronal plasma and magnetic field. Also, prominences are closely associated with other key phenomena such as coronal mass ejections and eruptive solar flares which occur as a prominence loses equilibrium and rises from the solar surface. Our current understanding of these fascinating structures is extremely limited and we know very little about their basic global structure. In fact, recent prominence observations have caused our basic paradigms to be challenged (Priest, 1996) and so we must set up new models in order to gain even a fundamental understanding. Prominences are highly nonlinear, three-dimensional structures. Large feet (or barbs) reach out from the main body of a prominence and reach down to the photosphere where the dense material continuously drains away. These provide a real clue to the three-dimensional nature of the coronal field and its relation to the photospheric field. It is important, therefore, to make stereographic observations of prominences in order to gain a basic understanding of their essentially three-dimensional nature and attempt to formulate new paradigms for their structure and evolution. There is no doubt that the study of prominences in three dimensions is a crucial exercise if we are to develop a better

  11. Online reconstruction of 3D magnetic particle imaging data

    NASA Astrophysics Data System (ADS)

    Knopp, T.; Hofmann, M.

    2016-06-01

    Magnetic particle imaging is a quantitative functional imaging technique that allows imaging of the spatial distribution of super-paramagnetic iron oxide particles at high temporal resolution. The raw data acquisition can be performed at frame rates of more than 40 volumes s-1. However, to date image reconstruction is performed in an offline step and thus no direct feedback is available during the experiment. Considering potential interventional applications such direct feedback would be mandatory. In this work, an online reconstruction framework is implemented that allows direct visualization of the particle distribution on the screen of the acquisition computer with a latency of about 2 s. The reconstruction process is adaptive and performs block-averaging in order to optimize the signal quality for a given amount of reconstruction time.

  12. Computed inverse MRI for magnetic susceptibility map reconstruction

    PubMed Central

    Chen, Zikuan; Calhoun, Vince

    2015-01-01

    Objective This paper reports on a computed inverse magnetic resonance imaging (CIMRI) model for reconstructing the magnetic susceptibility source from MRI data using a two-step computational approach. Methods The forward T2*-weighted MRI (T2*MRI) process is decomposed into two steps: 1) from magnetic susceptibility source to fieldmap establishment via magnetization in a main field, and 2) from fieldmap to MR image formation by intravoxel dephasing average. The proposed CIMRI model includes two inverse steps to reverse the T2*MRI procedure: fieldmap calculation from MR phase image and susceptibility source calculation from the fieldmap. The inverse step from fieldmap to susceptibility map is a 3D ill-posed deconvolution problem, which can be solved by three kinds of approaches: Tikhonov-regularized matrix inverse, inverse filtering with a truncated filter, and total variation (TV) iteration. By numerical simulation, we validate the CIMRI model by comparing the reconstructed susceptibility maps for a predefined susceptibility source. Results Numerical simulations of CIMRI show that the split Bregman TV iteration solver can reconstruct the susceptibility map from a MR phase image with high fidelity (spatial correlation≈0.99). The split Bregman TV iteration solver includes noise reduction, edge preservation, and image energy conservation. For applications to brain susceptibility reconstruction, it is important to calibrate the TV iteration program by selecting suitable values of the regularization parameter. Conclusions The proposed CIMRI model can reconstruct the magnetic susceptibility source of T2*MRI by two computational steps: calculating the fieldmap from the phase image and reconstructing the susceptibility map from the fieldmap. The crux of CIMRI lies in an ill-posed 3D deconvolution problem, which can be effectively solved by the split Bregman TV iteration algorithm. PMID:22446372

  13. Joint Stochastic Inversion of Pre-Stack 3D Seismic Data and Well Logs for High Resolution Hydrocarbon Reservoir Characterization

    NASA Astrophysics Data System (ADS)

    Torres-Verdin, C.

    2007-05-01

    This paper describes the successful implementation of a new 3D AVA stochastic inversion algorithm to quantitatively integrate pre-stack seismic amplitude data and well logs. The stochastic inversion algorithm is used to characterize flow units of a deepwater reservoir located in the central Gulf of Mexico. Conventional fluid/lithology sensitivity analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generates typical Class III AVA responses. On the other hand, layer- dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution. Accordingly, AVA stochastic inversion, which combines the advantages of AVA analysis with those of geostatistical inversion, provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties (P-velocity, S-velocity, density), and lithotype (sand- shale) distributions. The quantitative use of rock/fluid information through AVA seismic amplitude data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, yields accurate 3D models of petrophysical properties such as porosity and permeability. Finally, by fully integrating pre-stack seismic amplitude data and well logs, the vertical resolution of inverted products is higher than that of deterministic inversions methods.

  14. 3-D explosions: a meditation on rotation (and magnetic fields)

    NASA Astrophysics Data System (ADS)

    Wheeler, J. C.

    This is the text of an introduction to a workshop on asymmetric explosions held in Austin in June, 2003. The great progress in supernova research over thirty-odd years is briefly reviewed. The context in which the meeting was called is then summarized. The theoretical success of the intrinsically multidimensional delayed detonation paradigm in explaining the nature of Type Ia supernovae coupled with new techniques of observations in the near IR and with spectropolarimetry promise great advances in understanding binary progenitors, the explosion physics, and the ever more accurate application to cosmology. Spectropolarimetry has also revealed the strongly asymmetric nature of core collapse and given valuable perspectives on the supernova - gamma-ray burst connection. The capability of the magneto-rotational instability to rapidly create strong toroidal magnetic fields in the core collapse ambiance is outlined. This physics may be the precursor to driving MHD jets that play a role in asymmetric supernovae. Welcome to the brave new world of three-dimensional explosions!

  15. Seismic moment tensor inversion using 3D velocity model and its application to the 2013 Lushan earthquake sequence

    NASA Astrophysics Data System (ADS)

    Zhu, Lupei; Zhou, Xiaofeng

    2016-10-01

    Source inversion of small-magnitude events such as aftershocks or mine collapses requires use of relatively high frequency seismic waveforms which are strongly affected by small-scale heterogeneities in the crust. In this study, we developed a new inversion method called gCAP3D for determining general moment tensor of a seismic source using Green's functions of 3D models. It inherits the advantageous features of the "Cut-and-Paste" (CAP) method to break a full seismogram into the Pnl and surface-wave segments and to allow time shift between observed and predicted waveforms. It uses grid search for 5 source parameters (relative strengths of the isotropic and compensated-linear-vector-dipole components and the strike, dip, and rake of the double-couple component) that minimize the waveform misfit. The scalar moment is estimated using the ratio of L2 norms of the data and synthetics. Focal depth can also be determined by repeating the inversion at different depths. We applied gCAP3D to the 2013 Ms 7.0 Lushan earthquake and its aftershocks using a 3D crustal-upper mantle velocity model derived from ambient noise tomography in the region. We first relocated the events using the double-difference method. We then used the finite-differences method and reciprocity principle to calculate Green's functions of the 3D model for 20 permanent broadband seismic stations within 200 km from the source region. We obtained moment tensors of the mainshock and 74 aftershocks ranging from Mw 5.2 to 3.4. The results show that the Lushan earthquake is a reverse faulting at a depth of 13-15 km on a plane dipping 40-47° to N46° W. Most of the aftershocks occurred off the main rupture plane and have similar focal mechanisms to the mainshock's, except in the proximity of the mainshock where the aftershocks' focal mechanisms display some variations.

  16. Relevance of 3D magnetic resonance imaging sequences in diagnosing basal subarachnoid neurocysticercosis.

    PubMed

    Carrillo Mezo, Roger; Lara García, Javier; Arroyo, Mariana; Fleury, Agnès

    2015-12-01

    Imagenological diagnosis of subarachnoid neurocysticercosis is usually difficult when classical magnetic resonance imaging (MRI) sequences are used. The purpose of this study was to evaluate the advantages of 3D MRI sequences (Fast Imaging Employing Steady-state Acquisition (FIESTA) and Spoiled Gradient Recalled Echo (SPGR)) with respect to classical sequences (Fluid Attenuation Inversion Recovery (FLAIR) and T1) in visualizing Taenia solium cyst in these locations. Forty-seven T. solium cysts located in the basal cisterns of the subarachnoid space were diagnosed in eighteen Mexican patients. A pre-treatment MRI was performed on all patients, and all four sequences (FIESTA, FLAIR, T1 SPGR, and T2) were evaluated independently by two neuroradiologists. The sensitivity of each sequence to detect the parasite membrane and scolex was evaluated, along with its capacity to detect differences in signal intensity between cerebrospinal fluid (CSF) and cysts. FIESTA sequences allowed the visualization of cyst membrane in 87.2% of the parasites evaluated, FLAIR in 38.3%, SPGR in 23.4%, and T2 in 17.0%. The superiority of FIESTA sequences over the other three imaging methods was statistically significant (P<0.001). Scolices were detected by FIESTA twice as much as the other sequences did, although this difference was not significant (P>0.05). Differences in signal intensity between CSF and parasite cysts were significant in FIESTA (P<0.0001), SPGR (P<0.0001), and FLAIR (P=0.005) sequences. For the first time, the usefulness of 3D MRI sequences to diagnose T. solium cysts located in the basal cisterns of the subarachnoid space was demonstrated. The routine use of these sequences could favor an earlier diagnosis and greatly improve the prognosis of patients affected by this severe form of the disease.

  17. Realistic 3D coherent transfer function inverse filtering of complex fields

    PubMed Central

    Cotte, Yann; Toy, Fatih M.; Arfire, Cristian; Kou, Shan Shan; Boss, Daniel; Bergoënd, Isabelle; Depeursinge, Christian

    2011-01-01

    We present a novel technique for three-dimensional (3D) image processing of complex fields. It consists in inverting the coherent image formation by filtering the complex spectrum with a realistic 3D coherent transfer function (CTF) of a high-NA digital holographic microscope. By combining scattering theory and signal processing, the method is demonstrated to yield the reconstruction of a scattering object field. Experimental reconstructions in phase and amplitude are presented under non-design imaging conditions. The suggested technique is best suited for an implementation in high-resolution diffraction tomography based on sample or illumination rotation. PMID:21833359

  18. Realistic 3D coherent transfer function inverse filtering of complex fields.

    PubMed

    Cotte, Yann; Toy, Fatih M; Arfire, Cristian; Kou, Shan Shan; Boss, Daniel; Bergoënd, Isabelle; Depeursinge, Christian

    2011-08-01

    We present a novel technique for three-dimensional (3D) image processing of complex fields. It consists in inverting the coherent image formation by filtering the complex spectrum with a realistic 3D coherent transfer function (CTF) of a high-NA digital holographic microscope. By combining scattering theory and signal processing, the method is demonstrated to yield the reconstruction of a scattering object field. Experimental reconstructions in phase and amplitude are presented under non-design imaging conditions. The suggested technique is best suited for an implementation in high-resolution diffraction tomography based on sample or illumination rotation.

  19. Interpretation of gravity and magnetic data with geological constraints for 3D structure of the Thuringian Basin, Germany

    NASA Astrophysics Data System (ADS)

    Prutkin, Ilya; Vajda, Peter; Jahr, Thomas; Bleibinhaus, Florian; Novák, Pavel; Tenzer, Robert

    2017-01-01

    We apply a novel method for the separation of potential field sources and their 3D inversion at the regional study area of Thuringian Basin in central Germany. The gravity and magnetic data are separated into long, medium and short wavelengths and then inverted separately. The main goal is to study uniqueness of the solution and its stability in all numerical steps of the interpretation process and to demonstrate, how geological constraints can diminish the degree of non-uniqueness by the interpretation of the gravity and magnetic anomalies. Our numerical experiments with medium wavelengths reveal that if we explain negative anomalies with the topography of near-surface layers, the obtained solution is not supported by borehole data. These negative anomalies are thus explained by restricted bodies (granitic intrusions) at the depths from 4 down to 10 km. These bodies are located above a density interface with topography at the depth of approximately 10 km. The 3D inversion of magnetic data (at short wavelengths) allows investigating a detailed structure of the upper boundary of the crystalline basement: two uplifts in the depths between 2.0 and 0.7 km are found. By using the residual negative anomalies we further study the salt tectonics, showing that the geometry of a salt pillow with a thickness of approximately 200 m closely agrees with borehole data.

  20. 3D Gravity Inversion of Northern Sinai Peninsula: A Case Study

    NASA Astrophysics Data System (ADS)

    Khalil, Mohamed A.; Santos, Fernando M.

    2014-07-01

    The Sinai Peninsula has attracted the attention of many geological and geophysical studies as it is influenced and bounded by major tectonic events. Those are (1) the Mesozoic to Early Cenozoic tectonically active opening of the Tethys, (2) the Late Cretaceous to Early Tertiary (Laramide) Syrian arc system, due to closing of the Tethys (3) the Oligo-Miocene Gulf of Suez rifted basin, and (4) the Late Miocene to Recent transform Dead Sea-Gulf of Aqaba rift. Additionally, the shear zones inside Sinai such as the Ragabet El-Naam and Minsherah-Abu Kandu Shear Zones. Each of these major tectonic events has affected dramatically the structure evolution of the northern Sinai area. The present paper estimates the 3D density contrast model using the gravity data of northern Sinai. The estimated 3D density contrast model elucidated the peculiarities of the main structural elements in the region. The estimated 3D density contrast model showed the high and low gravity anomalies that form the main mountains and main valleys in northern Sinai. The estimated low density zones are in agreement with the inferred faults resulting from the first horizontal derivative. Comparing the 3D model with the tectonic history of the region and the results of the first horizontal derivative and least square separation increased the reliability of the model.

  1. 3-D Sound Propagation and Acoustic Inversions in Shallow Water Oceans

    DTIC Science & Technology

    2012-12-19

    fixed arc-length grid.] 10 Modeling comparisons Propagate over seamount , off center Source at 250 m, 100Hz 4 cases - (1) Nx2D, (2) Cartesian, (3...cylindrical PE. Figure 2. PE model comparisons I Sound propagation over a seamount are computed by different 3-D PE models, including (1) Nx2- D (2

  2. Compartmentalization of the Coso East Flank geothermal field imaged by 3-D full-tensor MT inversion

    NASA Astrophysics Data System (ADS)

    Lindsey, Nathaniel J.; Kaven, Joern Ole; Davatzes, Nicholas; Newman, Gregory A.

    2017-02-01

    Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of low resistivity (2-5 Ohm m) and appreciable lateral extent (>1 km) in the producing zone of the East Flank field. However, these models could not reproduce gross 3-D effects in the recorded data. We perform 3-D full-tensor inversion and retrieve a resistivity model that out-performs previous 2-D and 3-D off-diagonal models in terms of its fit to the complete 3-D MT data set as well as the degree of modelling bias. Inclusion of secondary Zxx and Zyy data components leads to a robust east-dip (60†) to the previously identified conductive East Flank reservoir feature, which correlates strongly with recently mapped surface faults, downhole well temperatures, 3-D seismic reflection data, and local microseismicity. We perform synthetic forward modelling to test the best-fit dip of this conductor using the response at a nearby MT station. We interpret the dipping conductor as a fractured and fluidized compartment, which is structurally controlled by an unmapped blind East Flank fault zone.

  3. Compartmentalization of the Coso East Flank Geothermal Field Imaged by 3-D Full-tensor MT Inversion

    NASA Astrophysics Data System (ADS)

    Lindsey, Nathaniel J.; Kaven, Joern Ole; Davatzes, Nicholas; Newman, Gregory A.

    2016-11-01

    Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of low resistivity (2 - 5 Ohm-m) and appreciable lateral extent (>1 km) in the producing zone of the East Flank field. However, these models could not reproduce gross 3-D effects in the recorded data. We perform 3-D full-tensor inversion and retrieve a resistivity model that out-performs previous 2-D and 3-D off-diagonal models in terms of its fit to the complete 3-D MT dataset as well as the degree of modeling bias. Inclusion of secondary Zxx and Zyy data components leads to a robust east-dip (60o) to the previously identified conductive East Flank reservoir feature, which correlates strongly with recently mapped surface faults, downhole well temperatures, 3-D seismic reflection data, and local microseismicity. We perform synthetic forward modeling to test the best fit dip of this conductor using the response at a nearby MT station. We interpret the dipping conductor as a fractured and fluidized compartment, which is structurally-controlled by an unmapped blind East Flank fault zone.

  4. On the magnetotransport of 3D systems in quantizing magnetic field

    NASA Astrophysics Data System (ADS)

    Cheremisin, M. V.

    2014-12-01

    The resistivity components of 3D electron gas placed in quantizing magnetic field are calculated taking into account the correction caused by combined action of the Peltier and Seebeck thermoelectric effects. The longitudinal, transverse and the Hall magnetoresistivities exhibit familiar 1/B-period oscillations being universal functions of magnetic field and temperature.

  5. 3D Seismic and Magnetic characterization of the Borax Lake Hydrothermal System in the Alvord Desert, southeastern Oregon.

    NASA Astrophysics Data System (ADS)

    Hess, S.; Bradford, J.; Lyle, M.; Routh, P.; Liberty, L.; Donaldson, P.

    2004-05-01

    throughout the survey area. Time slices through the 3D seismic cube show evidence of semi-continuous linear features consistent with the trend of the hot springs. A large scale inversion has been performed on the magnetic data. The fit to the observed data is good given the noise assumption of 3 nT. After more extensive processing, we will compare structures in the inverted magnetic model with features in the seismic data and explore the connection between the subsurface geology and the surface geometry of the hot springs.

  6. Single cell detection using 3D magnetic rolled-up structures.

    PubMed

    Ger, Tzong-Rong; Huang, Hao-Ting; Huang, Chen-Yu; Lai, Mei-Feng

    2013-11-07

    A 3D rolled-up structure made of a SiO2 layer and a fishbone-like magnetic thin film was proposed here as a biosensor. The magnetoresistance (MR) measurement results of the sensor suggest that the presence of the stray field, which is induced by the magnetic nanoparticles, significantly increased the switching field. Comparing the performance of the 2D sensor and 3D sensor designed in this study, the response in switching field variation was 12.14% in the 2D sensor and 62.55% in the 3D sensor. The response in MR ratio variation was 4.55% in the 2D sensor and 82.32% in the 3D sensor. In addition, the design of the 3D sensor structure also helped to attract and trap a single magnetic cell due to its stronger stray field compared with the 2D structure. The 3D magnetic biosensor designed here can provide important information for future biochip research and applications.

  7. Investigation of geological structures with a view to HLRW disposal, as revealed through 3D inversion of aeromagnetic and gravity data and the results of CSAMT exploration

    NASA Astrophysics Data System (ADS)

    An, Zhiguo; Di, Qingyun

    2016-12-01

    The Alxa area in Inner Mongolia has been selected as a possible site for geological disposal of high-level radioactive waste (HLRW). Based on results of a previous study on crustal stability, the Tamusu rock mass has been chosen as the target. To determine the geological structure of this rock mass, aeromagnetic and gravity data are collected and inverted. Three-dimensional (3D) inversion horizontal slices show that the internal density of the rock mass and the distribution of magnetic properties are not uniform, with fractures and fragmentation being present. To confirm this result, the controlled source audio-frequency magnetotelluric method (CSAMT) was applied to explore the geological structures, the typical CSAMT sounding curve was analyzed, and the response characteristics of the geological structure and surrounding rock are distinguished. The original data were processed and interpreted in combination with data from surface geology and drilling and logging data. It is found that the CSAMT results were consistent with those from 3D inversion of the gravity and magnetic data, confirming the existence of fractures and fragmentation in the exploration area.

  8. 3D-xy critical properties of YBa2Cu4O8 and magnetic-field-induced 3D to 1D crossover

    NASA Astrophysics Data System (ADS)

    Weyeneth, S.; Schneider, T.; Bukowski, Z.; Karpinski, J.; Keller, H.

    2008-08-01

    We present reversible magnetization data of a YBa2Cu4O8 single crystal and analyze the evidence for 3D-xy critical behavior and a magnetic-field-induced 3D to 1D crossover. Remarkable consistency with these phenomena is observed in agreement with a magnetic-field-induced finite size effect, whereupon the correlation length transverse to the applied magnetic field cannot grow beyond the limiting magnetic length scale LH = (Φ0/(aH))1/2. By applying the appropriate scaling form we obtain the zero-field critical temperature, the 3D to 1D crossover, the vortex melting line and the universal ratios of the related scaling variables. Accordingly there is no continuous phase transition in the (H,T) plane along the Hc2 lines as predicted by the mean-field treatment.

  9. Influence of 3D Teleseismic Body Waves in the Finite-Fault Source Inversion of Subduction Earthquakes

    NASA Astrophysics Data System (ADS)

    Sladen, A.; Monteiller, V.

    2014-12-01

    Most large earthquakes are generated in subduction zones. To study the complexity of these events, teleseismic body waves offer many advantages over other types of data: they allow to study both the temporal and spatial evolution of slip during the rupture, they don't depend on the presence of nearby land and they allow to study earthquakes regardless of their location. Since the development of teleseismic finite-fault inversion in the 1980th, teleseismic body waves have been simulated using 1D velocity models to take into account propagation effects at the source. Yet, subduction zones are known to be highly heterogeneous: they are characterized by curved and dipping structures, strong seismic velocity contrasts, strong variations of topography and height of the water column. The main reason for relying on a 1D approximation is the computational cost of 3D simulations. And while forward simulations of teleseismic waves in a 3D Earth are only starting to be tractable on modern computers at the frequency range of interest (0.1Hz or shorter), finite-fault source studies require a large number of these simulations. In this work, we present a new and efficient approach to compute 3D teleseismic body waves, in which the full 3D propagation is only computed in a regional domain using discontinuous Galerkin finite-element method, while the rest of the seismic wave field is propagated in a background axisymmetric Earth. The regional and global wave fields are matched using the so-called Total-Field/Scattered-Field technique. This new simulation approach allows us to study the waveform complexities resulting from 3D propagation and investigate how they could improve the resolution and reduce the non-uniqueness of finite-fault inversions.

  10. 3D Magnetic Induction Maps of Nanoscale Materials Revealed by Electron Holographic Tomography

    PubMed Central

    2015-01-01

    The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap and carries great potential to impact areas such as data storage, sensing, and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nm by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic nonplanar nanodevices. PMID:27182110

  11. Electromagnetic Response Inversion for a 3D Distribution of Conductivity/Dielect

    SciTech Connect

    Newman, Gregory

    2001-10-24

    NLCGCS inverts electromagnetic responses for a 3D distribution of electrical conductivity and dielectric permittivity within the earth for geophysical applications using single processor computers. The software comes bundled with a graphical user interface to aid in model construction and analysis and viewing of earth images. The solution employs both dipole and finite size source configurations for harmonic oscillatory sources. A new nonlinear preconditioner is included in the solution to speed up solution convergence.

  12. An inverse hyper-spherical harmonics-based formulation for reconstructing 3D volumetric lung deformations

    NASA Astrophysics Data System (ADS)

    Santhanam, Anand P.; Min, Yugang; Mudur, Sudhir P.; Rastogi, Abhinav; Ruddy, Bari H.; Shah, Amish; Divo, Eduardo; Kassab, Alain; Rolland, Jannick P.; Kupelian, Patrick

    2010-07-01

    A method to estimate the deformation operator for the 3D volumetric lung dynamics of human subjects is described in this paper. For known values of air flow and volumetric displacement, the deformation operator and subsequently the elastic properties of the lung are estimated in terms of a Green's function. A Hyper-Spherical Harmonic (HSH) transformation is employed to compute the deformation operator. The hyper-spherical coordinate transformation method discussed in this paper facilitates accounting for the heterogeneity of the deformation operator using a finite number of frequency coefficients. Spirometry measurements are used to provide values for the airflow inside the lung. Using a 3D optical flow-based method, the 3D volumetric displacement of the left and right lungs, which represents the local anatomy and deformation of a human subject, was estimated from 4D-CT dataset. Results from an implementation of the method show the estimation of the deformation operator for the left and right lungs of a human subject with non-small cell lung cancer. Validation of the proposed method shows that we can estimate the Young's modulus of each voxel within a 2% error level.

  13. Structural results for La Palma island using 3-D gravity inversion

    NASA Astrophysics Data System (ADS)

    Camacho, A. G.; FernáNdez, J.; GonzáLez, P. J.; Rundle, J. B.; Prieto, J. F.; Arjona, A.

    2009-05-01

    A recent gravity survey composed of 317 bench marks all over the island of La Palma (Canary Islands) is used, in combination with satellite data for regional aspects, to obtain results about structural properties of the island connected with the tectonic environment and local volcanism. To that end, a nonlinear three-dimensional gravity inversion approach is considered. The inversion scheme provides, in a nonsubjective form, the geometry of the anomalous bodies constructed in a random growth process. Results from the inversion can be interpreted in the framework of the geologic evolution of this ocean island volcano as a complex composite volcano with a large central body with high-density corresponding to the older intrusive part of the basalt complex. New unexpected features are enlightened, such as large thermal anomalies in the upper mantle southward of La Palma, as well as fracture en echelon zones associable to a slow active process of dislocation related to the recent volcanism in the southern half of the island. The results obtained for La Palma as a test site testify to the usefulness of the developed gravity inversion methodology for structural studies on islands in general.

  14. Magnetic Dissipation in Asymmetric Strong Guide 3D Simulations: Examples of Magnetic Diffusion and Reconnection

    NASA Astrophysics Data System (ADS)

    Scudder, J. D.; Karimabadi, H.; Daughton, W. S.

    2013-12-01

    Interpretations of 2D simulations of magnetic reconnection are greatly simplified by using the flux function, usually the out of plane component of the vector potential. This theoretical device is no longer available when simulations are analyzed in 3-D. We illustrate the results of determining the locale rates of flux slippage in simulations by a technique based on Maxwell's equations. The technique recovers the usual results obtained for the flux function in 2D simulations, but remains viable in 3D simulations where there is no flux function. The method has also been successfully tested for full PIC simulations where reconnection is geometrically forbiddden. While such layers possess measurable flux slippages (diffusion) their level is not as strong as recorded in known 2D PIC reconnection sites using the same methodology. This approach will be used to explore the spatial incidence and strength of flux slippages across a 3D, asymmetric, strong guide field run discussed previously in the literature. Regions of diffusive behavior are illustrated where LHDI has been previously identified out on the separatrices, while much stronger flux slippages, typical of the X-regions of 2D simulations, are shown to occur elsewhere throughout the simulation. These results suggest that reconnection requires sufficiently vigorous flux slippage to be self sustaining, while non-zero flux slippage can and does occur without being at the reconnection site. A cross check of this approach is provided by the mixing ratio of tagged simulation particles of known spatial origin discussed by Daughton et al., 2013 (this meeting); they provide an integral measure of flux slippage up to the present point in the simulation. We will discuss the correlations between our Maxwell based flux slippage rates and the inferred rates of change of this mixing ratio (as recorded in the local fluid frame).

  15. Reconstruction of 3D Coronal Magnetic Structures from THEMIS/MTR and Hinode/SOT Vector Maps

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Guo, Y.; Aulanier, G.; Démoulin, P.; Török, T.; Bommier, V.; Wiegelmann, T.; Gosain, S.

    2012-08-01

    Coordinated campaigns using THEMIS, Hinode, and other instruments have allowed us to study the magnetic fields of faculae, filaments, and active regions. In a first case, we modelled the 3D magnetic field in a flaring active region with a nonlinear force-free field extrapolation, using magnetic vectors observed by THEMIS/MTR as boundary condition. In order to construct a consistent bottom boundary for the model, we first removed the 180 degree ambiguity of the transverse fields and minimized the force and torque in the observed vector fields. We found a twisted magnetic flux rope, well aligned with the polarity inversion line and a part of an Hα filament, and located where a large flare is initiated about two hours later. In a second case, Hinode/SOT allowed us to detect fine flux concentrations in faculae, while MTR provided us with magnetic information at different levels in the atmosphere. The polarimetry analysis of the MTR and SOT data gave consistent results, using both UNNOFIT and MELANIE inversion codes.

  16. Analysis and measurement of the 3D magnetic field in a rotating magnetic field driven FRC

    NASA Astrophysics Data System (ADS)

    Velas, K. M.; Milroy, R. D.

    2012-10-01

    A translatable three-axis probe was installed on TCSU shortly before its shutdown. The probe has 90 windings that simultaneously measure Br, Bθ, and Bz at 30 radial positions. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Probe measurements are used to calculate the end-shorting torque and the rotating magnetic field (RMF) torque. The torque applied to the plasma is the RMF torque reduced by the shorting torque. An estimate of the plasma resistivity is made based on the steady state balance between the applied torque and the resistive torque. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Data from even- and odd-parity experiments will be presented. The NIMROD code has been adapted to simulate the TCSU experiment using boundary conditions adjusted to match both even- and odd-parity experimental conditions. A comparison of the n=0 components of the calculated fields to the 3-axis probe measurements shows agreement in the magnetic field structure of the FRC as well as in the jet region.

  17. Waveform inversion for 3-D earth structure using the Direct Solution Method implemented on vector-parallel supercomputer

    NASA Astrophysics Data System (ADS)

    Hara, Tatsuhiko

    2004-08-01

    We implement the Direct Solution Method (DSM) on a vector-parallel supercomputer and show that it is possible to significantly improve its computational efficiency through parallel computing. We apply the parallel DSM calculation to waveform inversion of long period (250-500 s) surface wave data for three-dimensional (3-D) S-wave velocity structure in the upper and uppermost lower mantle. We use a spherical harmonic expansion to represent lateral variation with the maximum angular degree 16. We find significant low velocities under south Pacific hot spots in the transition zone. This is consistent with other seismological studies conducted in the Superplume project, which suggests deep roots of these hot spots. We also perform simultaneous waveform inversion for 3-D S-wave velocity and Q structure. Since resolution for Q is not good, we develop a new technique in which power spectra are used as data for inversion. We find good correlation between long wavelength patterns of Vs and Q in the transition zone such as high Vs and high Q under the western Pacific.

  18. Experimental Studies on the 3D Macro- and Microphysics of Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Jara-Almonte, J.; Ji, H.; Yamada, M.; Yoo, J.; Fox, W. R., II

    2015-12-01

    Magnetic reconnection has been extensively studied in 2D geometries for many decades and considerable progress has been made in understating 2D reconnection physics, yet in real plasmas reconnection is fundamentally 3D in nature. Only recently has it become possible to study 3D reconnection using simulations, however some initial results have suggested that the inclusion of 3D effects does not strongly affect the basic properties of reconnection (e.g. reconnection rate or particle acceleration). Yet on the other hand, previous experiments, without direct 3D measurements, have implied that 3D effects could be important even in a quasi-2D system. Here we experimentally study both the (1) macro- and (2) microphysics of 3D reconnection in order to directly test the importance of 3D effects in a quasi-2D experiment. Using fully simultaneous 3D measurements, it is shown that during highly driven reconnection the macroscopic structure of the current sheet can become strongly 3D despite an essentially 2D upstream region. The correlation length along the current sheet is measured to be far shorter than suggested by kinetic simulations. Results from new experiments with stronger reconnection drive and diagnostics designed to estimate the 3D reconnection rate will be discussed. With regards to (2), the 3D microphysics, new diagnostics capable of measuring fluctuations at frequencies up to the electron cyclotron frequency (~ 300 MHz) have been developed and have identified the presence of very high frequency waves (~ 100 MHz) during asymmetric reconnection, localized to the low-density side. The detailed properties of these waves, including the measured power spectra and dispersion relation, will be discussed and compared with both previous satellite observations of high-frequency waves as well as with theoretical predictions on the generation of whistler waves during reconnection.

  19. Tuning the electronic and magnetic properties of borophene by 3d transition-metal atom adsorption

    NASA Astrophysics Data System (ADS)

    Li, J. Y.; Lv, H. Y.; Lu, W. J.; Shao, D. F.; Xiao, R. C.; Sun, Y. P.

    2016-12-01

    The electronic and magnetic properties of borophene functionalized by 3d transition metal (TM) atom adsorption are investigated by using first-principles calculations. The results show that the 3d TM atoms can be adsorbed on borophene with high binding energies ranging between 5.9 and 8.3 eV. Interestingly, the originally nonmagnetic borophene tends to be ferromagnetic when Ti, V, Cr, Mn, and Fe atoms are adsorbed, and the magnetic moments are dominated by the TM atoms. The origin of the ferromagnetism is discussed based on the Stoner criterion. Our results indicate that the magnetic properties of borophene can be effectively tuned through the adsorption of 3d TM atoms, which could have promising applications in spintronics and nanoelectronics.

  20. Multilevel-3D bit patterned magnetic media with 8 signal levels per nanocolumn.

    PubMed

    Amos, Nissim; Butler, John; Lee, Beomseop; Shachar, Meir H; Hu, Bing; Tian, Yuan; Hong, Jeongmin; Garcia, Davil; Ikkawi, Rabee M; Haddon, Robert C; Litvinov, Dmitri; Khizroev, Sakhrat

    2012-01-01

    This letter presents an experimental study that shows that a 3(rd) physical dimension may be used to further increase information packing density in magnetic storage devices. We demonstrate the feasibility of at least quadrupling the magnetic states of magnetic-based data storage devices by recording and reading information from nanopillars with three magnetically-decoupled layers. Magneto-optical Kerr effect microscopy and magnetic force microscopy analysis show that both continuous (thin film) and patterned triple-stack magnetic media can generate eight magnetically-stable states. This is in comparison to only two states in conventional magnetic recording. Our work further reveals that ferromagnetic interaction between magnetic layers can be reduced by combining Co/Pt and Co/Pd multilayers media. Finally, we are showing for the first time an MFM image of multilevel-3D bit patterned media with 8 discrete signal levels.

  1. Full-wave Moment Tensor and Tomographic Inversions Based on 3D Strain Green Tensor

    DTIC Science & Technology

    2010-01-31

    G. Jahnke, Wave propagation in 3D spherical sections: effects of subduction zones , Phys. Earth Planet. Inter., 132, 219-234, 2002. Komastitsch, D...is at scales smaller than the Fresnel zone . For example, a 1-Hz P/Pn wave recorded by a receiver ~1000 km from the source has a Fresnel zone width...approach, Eos Trans. AGU, 89(53), Fall Meet. Suppl., abstract T11E-06 Invited, 2008b. Sigloch, K., N. McQuarrie, G. Nolet, Two-stage subduction

  2. 3D fibre deposition and stereolithography techniques for the design of multifunctional nanocomposite magnetic scaffolds.

    PubMed

    De Santis, Roberto; D'Amora, Ugo; Russo, Teresa; Ronca, Alfredo; Gloria, Antonio; Ambrosio, Luigi

    2015-10-01

    Magnetic nanocomposite scaffolds based on poly(ε-caprolactone) and poly(ethylene glycol) were fabricated by 3D fibre deposition modelling (FDM) and stereolithography techniques. In addition, hybrid coaxial and bilayer magnetic scaffolds were produced by combining such techniques. The aim of the current research was to analyse some structural and functional features of 3D magnetic scaffolds obtained by the 3D fibre deposition technique and by stereolithography as well as features of multimaterial scaffolds in the form of coaxial and bilayer structures obtained by the proper integration of such methods. The compressive mechanical behaviour of these scaffolds was investigated in a wet environment at 37 °C, and the morphological features were analysed through scanning electron microscopy (SEM) and X-ray micro-computed tomography. The capability of a magnetic scaffold to absorb magnetic nanoparticles (MNPs) in water solution was also assessed. confocal laser scanning microscopy was used to assess the in vitro biological behaviour of human mesenchymal stem cells (hMSCs) seeded on 3D structures. Results showed that a wide range of mechanical properties, covering those spanning hard and soft tissues, can be obtained by 3D FDM and stereolithography techniques. 3D virtual reconstruction and SEM showed the precision with which the scaffolds were fabricated, and a good-quality interface between poly(ε-caprolactone) and poly(ethylene glycol) based scaffolds was observed for bilayer and coaxial scaffolds. Magnetised scaffolds are capable of absorbing water solution of MNPs, and a preliminary information on cell adhesion and spreading of hMSCs was obtained without the application of an external magnetic field.

  3. Development of direct-inverse 3-D methods for applied transonic aerodynamic wing design and analysis

    NASA Technical Reports Server (NTRS)

    Carlson, Leland A.

    1989-01-01

    An inverse wing design method was developed around an existing transonic wing analysis code. The original analysis code, TAWFIVE, has as its core the numerical potential flow solver, FLO30, developed by Jameson and Caughey. Features of the analysis code include a finite-volume formulation; wing and fuselage fitted, curvilinear grid mesh; and a viscous boundary layer correction that also accounts for viscous wake thickness and curvature. The development of the inverse methods as an extension of previous methods existing for design in Cartesian coordinates is presented. Results are shown for inviscid wing design cases in super-critical flow regimes. The test cases selected also demonstrate the versatility of the design method in designing an entire wing or discontinuous sections of a wing.

  4. 3D Kinetic Simulation of Plasma Jet Penetration in Magnetic Field

    NASA Astrophysics Data System (ADS)

    Galkin, Sergei A.; Bogatu, I. N.; Kim, J. S.

    2009-11-01

    A high velocity plasmoid penetration through a magnetic barrier is a problem of a great experimental and theoretical interest. Our LSP PIC code 3D fully kinetic numerical simulations of high density (10^16 cm-3) high velocity (30-140 km/sec) plasma jet/bullet, penetrating through the transversal magnetic field, demonstrate three different regimes: reflection by field, penetration by magnetic field expulsion and penetration by magnetic self-polarization. The behavior depends on plasma jet parameters and its composition: hydrogen, carbon (A=12) and C60-fullerene (A=720) plasmas were investigated. The 3D simulation of two plasmoid head-on injections along uniform magnetic field lines is analyzed. Mini rail plasma gun (accelerator) modeling is also presented and discussed.

  5. Development and Tuning of a 3-D Stochastic Inversion Methodology for the European Arctic

    DTIC Science & Technology

    2008-09-01

    Norway and is subdivided into four tectonic nappes. Obduction started in the Vendian to Middle Cambrian and lasted until the Silurian . 2008...10 and 150 s period were combined with existing data provided by the University of Colorado at Boulder. This new data set was inverted for maps...showing the 2D group-velocity distribution of Love and Rayleigh waves for specific periods . Using a Monte Carlo inversion technique (Shapiro and

  6. Optimization of computations for adjoint field and Jacobian needed in 3D CSEM inversion

    NASA Astrophysics Data System (ADS)

    Dehiya, Rahul; Singh, Arun; Gupta, Pravin K.; Israil, M.

    2017-01-01

    We present the features and results of a newly developed code, based on Gauss-Newton optimization technique, for solving three-dimensional Controlled-Source Electromagnetic inverse problem. In this code a special emphasis has been put on representing the operations by block matrices for conjugate gradient iteration. We show how in the computation of Jacobian, the matrix formed by differentiation of system matrix can be made independent of frequency to optimize the operations at conjugate gradient step. The coarse level parallel computing, using OpenMP framework, is used primarily due to its simplicity in implementation and accessibility of shared memory multi-core computing machine to almost anyone. We demonstrate how the coarseness of modeling grid in comparison to source (comp`utational receivers) spacing can be exploited for efficient computing, without compromising the quality of the inverted model, by reducing the number of adjoint calls. It is also demonstrated that the adjoint field can even be computed on a grid coarser than the modeling grid without affecting the inversion outcome. These observations were reconfirmed using an experiment design where the deviation of source from straight tow line is considered. Finally, a real field data inversion experiment is presented to demonstrate robustness of the code.

  7. Fast 3-D large-scale gravity and magnetic modeling using unstructured grids and an adaptive multilevel fast multipole method

    NASA Astrophysics Data System (ADS)

    Ren, Zhengyong; Tang, Jingtian; Kalscheuer, Thomas; Maurer, Hansruedi

    2017-01-01

    A novel fast and accurate algorithm is developed for large-scale 3-D gravity and magnetic modeling problems. An unstructured grid discretization is used to approximate sources with arbitrary mass and magnetization distributions. A novel adaptive multilevel fast multipole (AMFM) method is developed to reduce the modeling time. An observation octree is constructed on a set of arbitrarily distributed observation sites, while a source octree is constructed on a source tetrahedral grid. A novel characteristic is the independence between the observation octree and the source octree, which simplifies the implementation of different survey configurations such as airborne and ground surveys. Two synthetic models, a cubic model and a half-space model with mountain-valley topography, are tested. As compared to analytical solutions of gravity and magnetic signals, excellent agreements of the solutions verify the accuracy of our AMFM algorithm. Finally, our AMFM method is used to calculate the terrain effect on an airborne gravity data set for a realistic topography model represented by a triangular surface retrieved from a digital elevation model. Using 16 threads, more than 5800 billion interactions between 1,002,001 observation points and 5,839,830 tetrahedral elements are computed in 453.6 s. A traditional first-order Gaussian quadrature approach requires 3.77 days. Hence, our new AMFM algorithm not only can quickly compute the gravity and magnetic signals for complicated problems but also can substantially accelerate the solution of 3-D inversion problems.

  8. Spatial and temporal analysis of DIII-D 3D magnetic diagnostic data

    NASA Astrophysics Data System (ADS)

    Strait, E. J.; King, J. D.; Hanson, J. M.; Logan, N. C.

    2016-11-01

    An extensive set of magnetic diagnostics in DIII-D is aimed at measuring non-axisymmetric "3D" features of tokamak plasmas, with typical amplitudes ˜10-3 to 10-5 of the total magnetic field. We describe hardware and software techniques used at DIII-D to condition the individual signals and analysis to estimate the spatial structure from an ensemble of discrete measurements. Applications of the analysis include detection of non-rotating MHD instabilities, plasma control, and validation of MHD stability and 3D equilibrium models.

  9. Spatial and temporal analysis of DIII-D 3D magnetic diagnostic data.

    PubMed

    Strait, E J; King, J D; Hanson, J M; Logan, N C

    2016-11-01

    An extensive set of magnetic diagnostics in DIII-D is aimed at measuring non-axisymmetric "3D" features of tokamak plasmas, with typical amplitudes ∼10(-3) to 10(-5) of the total magnetic field. We describe hardware and software techniques used at DIII-D to condition the individual signals and analysis to estimate the spatial structure from an ensemble of discrete measurements. Applications of the analysis include detection of non-rotating MHD instabilities, plasma control, and validation of MHD stability and 3D equilibrium models.

  10. Spatial and temporal analysis of DIII-D 3D magnetic diagnostic data

    DOE PAGES

    Strait, E. J.; King, J. D.; Hanson, J. M.; ...

    2016-08-11

    An extensive set of magnetic diagnostics in DIII-D is aimed at measuring non-axisymmetric "3D" features of tokamak plasmas, with typical amplitudes ~10-3 to 10-5 of the total magnetic field. We describe hardware and software techniques used at DIII-D to condition the individual signals and analysis to estimate the spatial structure from an ensemble of discrete measurements. Lastly, applications of the analysis include detection of non-rotating MHD instabilities, plasma control, and validation of MHD stability and 3D equilibrium models.

  11. DIRECT DETECTION OF THE HELICAL MAGNETIC FIELD GEOMETRY FROM 3D RECONSTRUCTION OF PROMINENCE KNOT TRAJECTORIES

    SciTech Connect

    Zapiór, Maciej; Martinez-Gómez, David

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1–3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 10{sup 9} A.

  12. 3D Inversion of Gravity Anomalies for the Interpretation of Sedimentary Basins using Variable Density Contrast

    NASA Astrophysics Data System (ADS)

    Ekinci, Yunus Levent; Ertekin, Can

    2015-04-01

    Concern about sedimentary basins is generally related to their genetic and economic significance. Analysis of sedimentary basins requires the acquisition of data through outcrop studies and subsurface investigations that encompass drilling and geophysics. These data are commonly analysed by computer-assisted techniques. One of these methods is based on analysing gravity anomalies to compute the depth of sedimentary basin-basement rock interface. Sedimentary basins produce negative gravity anomalies, because they have mostly lower densities than that of the surrounding basement rocks. Density variations in a sedimentary fill increase rapidly at shallower depths then gradually reach the density of surrounding basement rocks due to the geostatic pressure i.e. compaction. The decrease of the density contrast can be easily estimated by a quadratic function. Hence, if the densities are chosen properly and the regional background is removed correctly, the topographical relief of the sedimentary basin-basement rock interface might be estimated by the inversion of the gravity data using an exponential density-depth relation. Three dimensional forward modelling procedure can be carried out by introducing a Cartesian coordinate system, and placing vertical prisms just below observation points on the grid plane. Depth to the basement, namely depths to the bottom of the vertical prisms are adjusted in an iterative manner by minimizing the differences between measured and calculated residual gravity anomalies. In this study, we present a MATLAB-based inversion code for the interpretation of sedimentary basins by approximating the topographical relief of sedimentary basin-basement rock interfaces. For a given gridded residual gravity anomaly map, the procedure estimates the bottom depths of vertical prisms by considering some published formulas and assumptions. The utility of the developed inversion code was successfully tested on theoretically produced gridded gravity data set

  13. 3D Geological Model of Nihe ore deposit Constrained by Gravity and Magnetic Modeling

    NASA Astrophysics Data System (ADS)

    Qi, Guang; Yan, Jiayong; Lv, Qingtan; Zhao, Jinhua

    2016-04-01

    We present a case study on using integrated geologic model in mineral exploration at depth. Nihe ore deposit in Anhui Province, is deep hidden ore deposit which was discovered in recent years, this finding is the major driving force of deep mineral exploration work in Luzong. Building 3D elaborate geological model has the important significance for prospecting to deep or surround in this area, and can help us better understand the metallogenic law and ore-controlling regularity. A 3D geological model, extending a depth from +200m to -1500m in Nihe ore deposit, has been compiled from surface geological map, cross-section, borehole logs and amounts of geological inference. And then the 3D geological models have been given physical property parameter for calculating the potential field. Modelling the potential response is proposed as means of evaluating the viability of the 3D geological models, and the evidence of making small changes to the uncertain parts of the original 3D geological models. It is expected that the final models not only reproduce supplied prior geological knowledge, but also explain the observed geophysical data. The workflow used to develop the 3D geologic model in this study includes the three major steps, as follows: (1) Determine the basic information of Model: Defining the 3D limits of the model area, the basic geological and structural unit, and the tectonic contact relations and the sedimentary sequences between these units. (2) 3D model construction: Firstly, a series of 2D geological cross sections over the model area are built by using all kinds of prior information, including surface geology, borehole data, seismic sections, and local geologists' knowledge and intuition. Lastly, we put these sections into a 3D environment according to their profile locations to build a 3D model by using geostatistics method. (3) 3D gravity and magnetic modeling: we calculate the potential field responses of the 3D model, and compare the predicted and

  14. 3-D imaging of large scale buried structure by 1-D inversion of very early time electromagnetic (VETEM) data

    USGS Publications Warehouse

    Aydmer, A.A.; Chew, W.C.; Cui, T.J.; Wright, D.L.; Smith, D.V.; Abraham, J.D.

    2001-01-01

    A simple and efficient method for large scale three-dimensional (3-D) subsurface imaging of inhomogeneous background is presented. One-dimensional (1-D) multifrequency distorted Born iterative method (DBIM) is employed in the inversion. Simulation results utilizing synthetic scattering data are given. Calibration of the very early time electromagnetic (VETEM) experimental waveforms is detailed along with major problems encountered in practice and their solutions. This discussion is followed by the results of a large scale application of the method to the experimental data provided by the VETEM system of the U.S. Geological Survey. The method is shown to have a computational complexity that is promising for on-site inversion.

  15. Relative stability of normal vs. inverse spinel for 3d transition metal oxides as lithium intercalation cathodes.

    PubMed

    Bhattacharya, Jishnu; Wolverton, C

    2013-05-07

    Spinel oxides represent an important class of cathode materials for Li-ion batteries. Two major variants of the spinel crystal structure are normal and inverse. The relative stability of normal and inverse ordering at different stages of lithiation has important consequences in lithium diffusivity, voltage, capacity retention and battery life. In this paper, we investigate the relative structural stability of normal and inverse structures of the 3d transition metal oxide spinels with first-principles DFT calculations. We have considered ternary spinel oxides LixM2O4 with M = Ti, V, Cr, Mn, Fe, Co and Ni in both lithiated (x = 1) and delithiated (x = 0) conditions. We find that for all lithiated spinels, the normal structure is preferred regardless of the metal. We observe that the normal structure for all these oxides has a lower size mismatch between octahedral cations compared to the inverse structure. With delithiation, many of the oxides undergo a change in stability with vanadium in particular, showing a tendency to occupy tetrahedral sites. We find that in the delithiated oxide, only vanadium ions can access a +5 oxidation state which prefers tetrahedral coordination. We have also calculated the average voltage of lithiation for these spinels. The calculated voltages agree well with the previously measured and calculated values, wherever available. For the yet to be characterized spinels, our calculation provides voltage values which can motivate further experimental attention. Lastly, we observe that all the normal spinel oxides of the 3d transition metal series have a driving force for a transformation to the non-spinel structure upon delithiation.

  16. Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Raghunathan, M.; Graves, J. P.; Cooper, W. A.; Pedro, M.; Sauter, O.

    2016-09-01

    We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D effects such as non-resonant internal kink modes. The first approach relies on known neoclassical coefficients in ideal MHD equilibria, using the Sauter (Sauter et al 1999 Phys. Plasmas 6 2834) expression valid for all collisionalities in axisymmetry, and the second approach being the quasi-analytic Shaing-Callen (Shaing and Callen 1983 Phys. Fluids 26 3315) model in the collisionless regime for 3D. Using the ideal free-boundary magnetohydrodynamic code VMEC, we compute the flux-surface averaged bootstrap current density, with the Sauter and Shaing-Callen expressions for 2D and 3D ideal MHD equilibria including an edge pressure barrier with the application of resonant magnetic perturbations, and equilibria possessing a saturated non-resonant 1/1 internal kink mode with a weak internal pressure barrier. We compare the applicability of the self-consistent iterative model on the 3D applications and discuss the limitations and advantages of each bootstrap current model for each type of equilibrium.

  17. A numerical method for the inverse problem of cell traction in 3D

    NASA Astrophysics Data System (ADS)

    Vitale, G.; Preziosi, L.; Ambrosi, D.

    2012-09-01

    Force traction microscopy is an inversion method that allows us to obtain the stress field applied by a living cell on the environment on the basis of a pointwise knowledge of the displacement produced by the cell itself. This classical biophysical problem, usually addressed in terms of Green’s functions, can be alternatively tackled in a variational framework. In such a case, a variation of the error functional under suitable regularization is operated in view of its minimization. This setting naturally suggests the introduction of a new equation, based on the adjoint operator of the elasticity problem. In this paper, we illustrate a numerical strategy of the inversion method that discretizes the partial differential equations associated with the optimal control problem by finite elements. A detailed discussion of the numerical approximation of a test problem (with known solution) that contains most of the mathematical difficulties of the real one allows a precise evaluation of the degree of confidence that one can achieve in the numerical results.

  18. Magnetic and Magnetoresistive Properties of 3D Interconnected NiCo Nanowire Networks

    NASA Astrophysics Data System (ADS)

    da Câmara Santa Clara Gomes, Tristan; De La Torre Medina, Joaquín; Lemaitre, Matthieu; Piraux, Luc

    2016-10-01

    Track-etched polymer membranes with crossed nanochannels have been revealed to be most suitable as templates to produce large surface area and mechanically stable 3D interconnected nanowire (NW) networks by electrodeposition. Geometrically controlled NW superstructures made of NiCo ferromagnetic alloys exhibit appealing magnetoresistive properties. The combination of exact alloy compositions with the spatial arrangement of NWs in the 3D network is decisive to obtain specific magnetic and magneto-transport behavior. A proposed simple model based on topological aspects of the 3D NW networks is used to accurately determine the anisotropic magnetoresistance ratios. Despite of their complex topology, the microstructure of Co-rich NiCo NW networks display mixed fcc-hcp phases with the c-axis of the hcp phase oriented perpendicular to their axis. These interconnected NW networks have high potential as reliable and stable magnetic field sensors.

  19. Ballooning Stability Of Tokamak Pedestals In The Presence Of Applied 3D Magnetic Perturbations

    NASA Astrophysics Data System (ADS)

    Cote, T. B.; Hegna, C. C.; Willensdorfer, M.; Strumberger, E.; Suttrop, W.; Zohm, H.

    2016-10-01

    Applied 3d magnetic perturbations can destabilize ideal mhd ballooning modes in tokamak pedestals. In this work, we describe techniques for studying infinite-n ballooning stability of 3d equilibria deduced from vmec calculations. Full magnetic profiles from vmec are used to construct local equilibria for flux surfaces in and around the edge pedestal region. These local equilibrium calculations are coupled with ideal ballooning stability analysis to determine stability of the system for given rmp configurations. This theoretical development is motivated by recent asdex-u experiments, where toroidally localized high-n mhd activity is observed in the presence of applied 3d fields. We will attempt to explain these observations. Supported by US DOE under Grant No. DE-FG02-86ER53218.

  20. Synthesis of 3D Model of a Magnetic Field-Influenced Body from a Single Image

    NASA Technical Reports Server (NTRS)

    Wang, Cuilan; Newman, Timothy; Gallagher, Dennis

    2006-01-01

    A method for recovery of a 3D model of a cloud-like structure that is in motion and deforming but approximately governed by magnetic field properties is described. The method allows recovery of the model from a single intensity image in which the structure's silhouette can be observed. The method exploits envelope theory and a magnetic field model. Given one intensity image and the segmented silhouette in the image, the method proceeds without human intervention to produce the 3D model. In addition to allowing 3D model synthesis, the method's capability to yield a very compact description offers further utility. Application of the method to several real-world images is demonstrated.

  1. Identification of groundwater parameters at Columbus, Mississippi, using a 3D inverse flow and transport model

    USGS Publications Warehouse

    Barlebo, H.C.; Rosbjerg, D.; Hill, M.C.

    1996-01-01

    An extensive amount of data including hydraulic heads, hydraulic conductivities and concentrations of several solutes from controlled injections have been collected during the MADE 1 and MADE 2 experiments at a heterogeneous site near Columbus, Mississippi. In this paper the use of three-dimensional inverse groundwater models including simultaneous estimation of flow and transport parameters is proposed to help identify the dominant characteristics at the site. Simulations show that using a hydraulic conductivity distribution obtained from 2187 borehole flowmeter tests directly in the model produces poor matches to the measured hydraulic heads and tritium concentrations. Alternatively, time averaged hydraulic head maps are used to define zones of constant hydraulic conductivity to be estimated. Preliminary simulations suggest that in the case of conservative transport many, but not all, of the major plume characteristics can be explained by large-scale heterogeneity in recharge and hydraulic conductivity.

  2. Development of direct-inverse 3-D methods for applied transonic aerodynamic wing design and analysis

    NASA Technical Reports Server (NTRS)

    Carlson, Leland A.

    1989-01-01

    Progress in the direct-inverse wing design method in curvilinear coordinates has been made. This includes the remedying of a spanwise oscillation problem and the assessment of grid skewness, viscous interaction, and the initial airfoil section on the final design. It was found that, in response to the spanwise oscillation problem that designing at every other spanwise station produced the best results for the cases presented, a smoothly varying grid is especially needed for the accurate design at the wing tip, the boundary layer displacement thicknesses must be included in a successful wing design, the design of high and medium aspect ratio wings is possible with this code, and the final airfoil section designed is fairly independent of the initial section.

  3. Hall-Effect Sign Inversion in a Realizable 3D Metamaterial

    NASA Astrophysics Data System (ADS)

    Kadic, Muamer; Schittny, Robert; Bückmann, Tiemo; Kern, Christian; Wegener, Martin

    2015-04-01

    In 2009, Briane and Milton proved mathematically the existence of three-dimensional isotropic metamaterials with a classical Hall coefficient that is negative with respect to that of all of the metamaterial constituents. Here, we significantly simplify their blueprint towards an architecture composed of only a single-constituent material in vacuum or air, which can be seen as a special type of porosity. We show numerically that the sign of the Hall voltage is determined by a separation parameter between adjacent tori. This qualitative behavior is robust even for only a small number of metamaterial unit cells. The combination of simplification and robustness brings experimental verification of this striking sign inversion into reach. Furthermore, we provide a simple intuitive explanation of the underlying physical mechanism.

  4. 3-D Localization Method for a Magnetically Actuated Soft Capsule Endoscope and Its Applications

    PubMed Central

    Yim, Sehyuk; Sitti, Metin

    2014-01-01

    In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0–3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis. PMID:25383064

  5. Analysis of a 3-D system function measured for magnetic particle imaging.

    PubMed

    Rahmer, Jürgen; Weizenecker, Jürgen; Gleich, Bernhard; Borgert, Jörn

    2012-06-01

    Magnetic particle imaging (MPI) is a new tomographic imaging approach that can quantitatively map magnetic nanoparticle distributions in vivo. It is capable of volumetric real-time imaging at particle concentrations low enough to enable clinical applications. For image reconstruction in 3-D MPI, a system function (SF) is used, which describes the relation between the acquired MPI signal and the spatial origin of the signal. The SF depends on the instrumental configuration, the applied field sequence, and the magnetic particle characteristics. Its properties reflect the quality of the spatial encoding process. This work presents a detailed analysis of a measured SF to give experimental evidence that 3-D MPI encodes information using a set of 3-D spatial patterns or basis functions that is stored in the SF. This resembles filling 3-D k-space in magnetic resonance imaging, but is faster since all information is gathered simultaneously over a broad acquisition bandwidth. A frequency domain analysis shows that the finest structures that can be encoded with the presented SF are as small as 0.6 mm. SF simulations are performed to demonstrate that larger particle cores extend the set of basis functions towards higher resolution and that the experimentally observed spatial patterns require the existence of particles with core sizes of about 30 nm in the calibration sample. A simple formula is presented that qualitatively describes the basis functions to be expected at a certain frequency.

  6. Extensions of 1d Bgk Electron Solitary Wave Solutions To 3d Magnetized and Unmagnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Chen, Li-Jen; Parks, George K.

    This paper will compare the key results for BGK electron solitary waves in 3D mag- netized and unmagnetized plasmas. For 3D magnetized plasmas with highly magnetic field-aligned electrons, our results predict that the parallel widths of the solitary waves can be smaller than one Debye length, the solitary waves can be large scale features of the magnetosphere, and the parallel width-amplitude relation has a dependence on the perpendicular size. We can thus obtain an estimate on the typical perpendicular size of the observed solitary waves assuming a series of consecutive solitary waves are in the same flux tude with a particular perpendicular span. In 3D unmagnetized plasma systems such as the neutral sheet and magnetic reconnection sites, our theory indi- cates that although mathematical solutions can be constructed as the time-stationary solutions for the nonlinear Vlasov-Poisson equations, there does not exist a param- eter range for the solutions to be physical. We conclude that single-humped solitary potential pulses cannot be self-consistently supported by charged particles in 3D un- magnetized plasmas.

  7. Inversion of multi-frequency electromagnetic induction data for 3D characterization of hydraulic conductivity

    USGS Publications Warehouse

    Brosten, T.R.; Day-Lewis, F. D.; Schultz, G.M.; Curtis, G.P.; Lane, J.W.

    2011-01-01

    Electromagnetic induction (EMI) instruments provide rapid, noninvasive, and spatially dense data for characterization of soil and groundwater properties. Data from multi-frequency EMI tools can be inverted to provide quantitative electrical conductivity estimates as a function of depth. In this study, multi-frequency EMI data collected across an abandoned uranium mill site near Naturita, Colorado, USA, are inverted to produce vertical distribution of electrical conductivity (EC) across the site. The relation between measured apparent electrical conductivity (ECa) and hydraulic conductivity (K) is weak (correlation coefficient of 0.20), whereas the correlation between the depth dependent EC obtained from the inversions, and K is sufficiently strong to be used for hydrologic estimation (correlation coefficient of -0.62). Depth-specific EC values were correlated with co-located K measurements to develop a site-specific ln(EC)-ln(K) relation. This petrophysical relation was applied to produce a spatially detailed map of K across the study area. A synthetic example based on ECa values at the site was used to assess model resolution and correlation loss given variations in depth and/or measurement error. Results from synthetic modeling indicate that optimum correlation with K occurs at ~0.5m followed by a gradual correlation loss of 90% at 2.3m. These results are consistent with an analysis of depth of investigation (DOI) given the range of frequencies, transmitter-receiver separation, and measurement errors for the field data. DOIs were estimated at 2.0??0.5m depending on the soil conductivities. A 4-layer model, with varying thicknesses, was used to invert the ECa to maximize available information within the aquifer region for improved correlations with K. Results show improved correlation between K and the corresponding inverted EC at similar depths, underscoring the importance of inversion in using multi-frequency EMI data for hydrologic estimation. ?? 2011.

  8. Enhanced imaging of CO2 at the Ketzin storage site: Inversion of 3D time-lapse seismic data

    NASA Astrophysics Data System (ADS)

    Gil, M.; Götz, J.; Ivanova, A.; Juhlin, C.; Krawczyk, C. M.; Lüth, S.; Yang, C.

    2012-04-01

    The Ketzin test site, located near Berlin, is Europe's longest-operating on-shore CO2 storage site. As of December 2011, more than 56,000 tons of food grade CO2 has been injected since June 2008 in an anticlinal structure of the Northeast German Basin. The target reservoir consists of porous, brine bearing sandstone units of the Upper Triassic Stuttgart Formation at approximately 630 to 650 m depth. In order to enhance the understanding of the structural geometry of the site and to investigate the extension of the CO2-plume, several geophysical monitoring methods are being applied at Ketzin, among these are active seismic measurements, geoelectrics and borehole measurements. Among the various seismic techniques (e.g. 2D reflection surveys, crosshole tomography, Vertical Seismic Profiling, 2D- and 3D-Moving Source Profiling) employed at this pilot site, 3D time-lapse reflection surveys are an important component. The baseline 3D survey was acquired in 2005 and the first repeat measurements were performed in 2009 after injection of about 22,000 tons of CO2. The second repeat survey is planned to be carried out in fall 2012. These measurements allow the time-lapse signature of the injected CO2 to be imaged. The time-lapse amplitude variation attributed to the injected CO2 in the reservoir matches, considering detection limits of seismic surface measurements, the expected distribution of the CO2 plume derived from reservoir simulations. Previous attempts towards a quantitative interpretation were based on integrative considerations of different types of geophysical measurements using strict assumptions and characterized by large error bars. In order to increase the resolution and reliability of the data and to improve estimation of rock properties and especially to enhance the imaging resolution of the CO2-plume, the time-lapse 3D seismic data have now been inverted for seismic impedances with different methods, which is the focus of this presentation. One difficulty

  9. Experimental onset threshold and magnetic pressure pileup for 3D Sweet-Parker reconnection

    SciTech Connect

    Intrator, Thomas P; Sun, Xuan; Lapenta, Giovanni; Furno, Ivo

    2008-01-01

    In space, astrophysical and laboratory plasmas, magnetic reconnect ion converts magnetic into particle energy during unsteady, explosive events. The abrupt onset and cessation has been a long standing puzzle. We show the first three-dimensional (3D) laboratory example of onset and stagnation of Sweet-Parker type magnetic reconnection between magnetized and parallel current (flux) ropes driven by magnetohydrodynamic (MHD) attraction and 3D instability. Mutually attracting flux ropes advect and merge oppositely directed magnetic fields. Magnetic flux is annihilated, but reaches soon a threshold where magnetic flux and pressure pile up, and reconnection magnetic topology appears. This occurs when inflow speeds exceed the SweetParker speed v{sub SP} = v{sub A} / S{sup 1/2}, where v{sub A} is the Alfven speed and S is the Lundquist number for the reconnection layer, as magnetic flux arrives faster than flux annihilation can process it. Finally piled up fields generate MHD reaction forces that stall the inflow and the reconnection process.

  10. Ultrasonic simulation—Imagine3D and SimScan: Tools to solve the inverse problem for complex turbine components

    NASA Astrophysics Data System (ADS)

    Mair, H. D.; Ciorau, P.; Owen, D.; Hazelton, T.; Dunning, G.

    2000-05-01

    Two ultrasonic simulation packages: Imagine 3D and SIMSCAN have specifically been developed to solve the inverse problem for blade root and rotor steeple of low-pressure turbine. The software was integrated with the 3D drawing of the inspected parts, and with the dimensions of linear phased-array probes. SIMSCAN simulates the inspection scenario in both optional conditions: defect location and probe movement/refracted angle range. The results are displayed into Imagine 3-D, with a variety of options: rendering, display 1:1, grid, generated UT beam. The results are very useful for procedure developer, training and to optimize the phased-array probe inspection sequence. A spreadsheet is generated to correlate the defect coordinates with UT data (probe position, skew and refracted angle, UT path, and probe movement). The simulation models were validated during experimental work with phased-array systems. The accuracy in probe position is ±1 mm, and the refracted/skew angle is within ±0.5°. Representative examples of phased array focal laws/probe movement for a specific defect location, are also included.

  11. Exact spectra of strong coulomb correlations of 3-D 2-e harmonic dots in magnetic field

    NASA Astrophysics Data System (ADS)

    Aggarwal, Priyanka; Sharma, Shivalika; Kaur, Harsimran; Singh, Sunny; Hazra, Ram Kuntal

    2017-01-01

    Applications of 3-D 2-e systems have proliferated very fast due to technological advancements in wide range of phenomena from atomic landscape to mesoscopic scale. The unusual properties of atomic/mesoscopic systems are the results of interplaying charge interactions among different bound states. The non-trivial e-e correlations in electrically and/or magnetically confined systems improvise wealth of intriguing challenges at fundamental level due to lack of exact solution of Schrödinger equations. For the first time, a novel methodology of exactly finite summed coulomb correlations invented by us is so handy that even usual programmable calculator can be used to examine the electronic structures of 3-D 2-e harmonic dots in perpendicular magnetic field (symmetric gauge). Statistics of electronic levels, heat capacity measurements and magnetization (T∼1 K) are also investigated in brief to probe the degree of disorderedness.

  12. 3D Simulation of Elastic Wave Propagation in Heterogeneous Anisotropic Media in Laplace Domain for Electromagnetic-Seismic Inverse Modeling

    NASA Astrophysics Data System (ADS)

    Petrov, P.; Newman, G. A.

    2011-12-01

    Recent developments in high resolution imaging technology of subsurface objects involves a combination of different geophysical measurements (gravity, EM and seismic). A joint image of the subsurface geophysical attributes (velocity, electrical conductivity and density) requires the consistent treatment of the different geophysical data due to their differing physical nature. For example, in conducting media, which is typical of the Earth's interior, EM energy propagation is defined by a diffusive mechanism and may be characterized by two specific length scales: wavelength and skin depth. However, the propagation of seismic signals is a multiwave process and is characterized by a set of wavelengths. Thus, to consistently treat seismic and electromagnetic data an additional length scale is needed for seismic data that does not directly depend on a wavelength and describes a diffusive process, similar to EM wave propagation in the subsurface. Works by Brown et al.(2005), Shin and Cha(2008), and Shin and Ha(2008) suggest that an artificial damping of seismic wave fields via Laplace-Fourier transformation can be an effective approach to obtain a seismic data that have similar spatial resolution to EM data. The key benefit of such transformation is that diffusive wave-field inversion works well for both data sets: seismic (Brown et al.,2005; Shin and Cha,2008) and electromagnetic (Commer and Newman,2008; Newman et al.,2010). With the recent interest in the Laplace-Fourier domain full waveform inversion, 3D fourth and second-order finite-difference schemes for modeling of seismic wave propagation have been developed (Petrov and Newman, 2010). Incorporation of attenuation and anisotropy into a velocity model is a necessary step for a more realistic description of subsurface media. Here we consider the extension of our method which includes attenuation and VTI anisotropy. Our approach is based on the integro-interpolation technique for velocity-stress formulation. Seven

  13. 3D imaging of soil apparent electrical conductivity from VERIS data using a 1D spatially constrained inversion algorithm

    NASA Astrophysics Data System (ADS)

    Jesús Moral García, Francisco; Rebollo Castillo, Francisco Javier; Monteiro Santos, Fernando

    2016-04-01

    Maps of apparent electrical conductivity of the soil are commonly used in precision agriculture to indirectly characterize some important properties like salinity, water, and clay content. Traditionally, these studies are made through an empirical relationship between apparent electrical conductivity and properties measured in soil samples collected at a few locations in the experimental area and at a few selected depths. Recently, some authors have used not the apparent conductivity values but the soil bulk conductivity (in 2D or 3D) calculated from measured apparent electrical conductivity through the application of an inversion method. All the published works used data collected with electromagnetic (EM) instruments. We present a new software to invert the apparent electrical conductivity data collected with VERIS 3100 and 3150 (or the more recent version with three pairs of electrodes) using the 1D spatially constrained inversion method (1D SCI). The software allows the calculation of the distribution of the bulk electrical conductivity in the survey area till a depth of 1 m. The algorithm is applied to experimental data and correlations with clay and water content have been established using soil samples collected at some boreholes. Keywords: Digital soil mapping; inversion modelling; VERIS; soil apparent electrical conductivity.

  14. The ITER 3D Magnetic Diagnostic Response to Applied n=3 and n=4 RMP's

    SciTech Connect

    Lazerson, S A

    2014-09-01

    The ITER magnetic diagnostic response to applied n=3 and n=4 RMPs has been calculated for the 15MA scenario. The VMEC code was utilized to calculate free boundary 3D ideal MHD equilibria, where the non-stellarator symmetric terms were included in the calculation. This allows an assessment to be made of the possible boundary displacements due to RMP application in ITER. As the VMEC code assumes a continuous set of nested flux surface, the possibility of island and stochastic region formation is ignored. At the start of the current at-top (L-Mode) application of n = 4 RMP's indicates approximately 1 cm peak-to-peak displacements on the low field side of the plasma while later in the shot (H-mode) perturbations as large as 3 cm are present. Forward modeling of the ITER magnetic diagnostics indicates significant non-axisymmetric plasma response, exceeding 10% the axisymmetric signal in many of the flux loops. Magnetic field probes seem to indicate a greater robustness to 3D effects but still indicate large sensitivities to 3D effects in a number of sensors. Forward modeling of the diagnostics response to 3D equilibria allows assessment of diagnostics design and control scenarios.

  15. The scattering potential of partial derivative wavefields in 3-D elastic orthorhombic media: an inversion prospective

    NASA Astrophysics Data System (ADS)

    Oh, Ju-Won; Alkhalifah, Tariq

    2016-09-01

    Multiparameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multicomponent sensors, the potential for trade-off between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22, and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23, and C12 suffer from strong trade-offs with C55, C44, and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.

  16. Bifurcation to 3D helical magnetic equilibrium in an axisymmetric toroidal device.

    PubMed

    Bergerson, W F; Auriemma, F; Chapman, B E; Ding, W X; Zanca, P; Brower, D L; Innocente, P; Lin, L; Lorenzini, R; Martines, E; Momo, B; Sarff, J S; Terranova, D

    2011-12-16

    We report the first direct measurement of the internal magnetic field structure associated with a 3D helical equilibrium generated spontaneously in the core of an axisymmetric toroidal plasma containment device. Magnetohydrodynamic equilibrium bifurcation occurs in a reversed-field pinch when the innermost resonant magnetic perturbation grows to a large amplitude, reaching up to 8% of the mean field strength. Magnetic topology evolution is determined by measuring the Faraday effect, revealing that, as the perturbation grows, toroidal symmetry is broken and a helical equilibrium is established.

  17. Anisotropic heat transport in integrable and chaotic 3-D magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B; Blazevski, D.; Chacon, Luis

    2012-01-01

    A study of anisotropic heat transport in 3-D chaotic magnetic fields is presented. The approach is based on the recently proposed Lagrangian-Green s function (LG) method in Ref. [1] that allows an efficient and accurate integration of the parallel transport equation applicable to general magnetic fields with local or non-local parallel flux closures. We focus on reversed shear magnetic field configurations known to exhibit separatrix reconnection and shearless transport barriers. The role of reconnection and magnetic field line chaos on temperature transport is studied. Numerical results are presented on the anomalous relaxation of radial temperature gradients in the presence of shearless Cantori partial barri- ers. Also, numerical evidence of non-local effective radial temperature transport in chaotic fields is presented. Going beyond purely parallel transport, the LG method is generalized to include finite perpendicular diffusivity, and the problem of temperature flattening inside a magnetic island is studied.

  18. Numerical simulation and inversion of MT fields in the 3D electric conductivity model of the Vesuvius volcano

    NASA Astrophysics Data System (ADS)

    Spichak, V. V.

    2011-01-01

    Possibilities for three-dimensional (3D) magnetotelluric (MT) sounding of local objects contained in the Earth's crust are estimated in a case study of the magma chamber of the Vesuvius volcano. Stochastic inversion of the model MT data by the Markov Chain Monte Carlo (MCMC) method has shown that the most efficient approach is not simultaneous but successive estimation of the geometry and the depth of the anomaly and the assessment of the conductivity distribution within the anomalous region. A zone of equivalence is revealed between the a priori estimate of the depth of the anomalous zone and the a posteriori distribution of electric conductivity within it. Based on the present estimation and previous results, an algorithm for determination of the parameters of local crustal anomaly is proposed.

  19. Magnetic and Electronic Phase Diagram of Sr2VFeAsO3-d

    NASA Astrophysics Data System (ADS)

    Tojo, Yujiro; Shibuya, Taizo; Nakamura, Tetsuro; Shoji, Koichiro; Matoba, Masanori; Yasui, Shintaro; Itoh, Mitsuru; Kitao, Shinji; Seto, Makoto; Kamihara, Yoichi; Research Grants From Keio Univ. Collaboration; Msl Collaborative Research Project Collaboration; Joint Usage in Krri Collaboration

    2014-03-01

    Ae2MFePnO3 (so-called 21113 systems) with perovskite-type layers such as Ae2MO3, where Ae denotes alkaline earth metals, M does Sc, Ti, Cr, V and other transition metal atoms and Pn does As and P shows superconductivity at T <46 K. Sr2VFeAsO3-d is a representative compound in 21113 systems. [Zhu et al, Phys. Rev. B (2009); Ogino et al, Supercond. Sci. Technol. (2009); Ogino et al, Supercond. Sci. Technol. (2009)] Although the oxygen deficiency (d) as a function of Tc is still controversial in Sr2VFeAsO3-d, many samples have been reported as superconductors with Tc = 24-37 K. In this study, a polycrystalline Sr2VFeAsO3-d (d = ~ 0.1- 0.6) were prepared by a solid state reaction using an alumina tube in a sealed silica tube. DC electrical resistivity was measured by a four-probe technique. Magnetization measurements were performed on a superconducting quantum interference device. 57Fe Mossbauer spectra were obtained using conventional equipment. The electronic and magnetic phase diagram of Sr2VFeAsO3-d is elucidated.

  20. 3-D Modeling of Magnetic Fields for the Lithium Tokamak eXperiment

    NASA Astrophysics Data System (ADS)

    Logan, N.; Berzak, L.; Kaita, R.; Majeski, R.; Menard, J.; Zakharov, L.

    2010-11-01

    The Lithium Tokamak eXperiment (LTX) is designed to investigate low-recycling operating regimes by surrounding 85% of the last closed flux surface with liquid lithium evaporated onto a copper and stainless steel shell conformal to the plasma. Fields generated by currents in this conducting shell have significant effects on magnetic configurations. To understand these effects, the commercially available code Aether [http://www.fieldp.com] is used to simulate time varying magnetic fields in a 3-D model of LTX. The model is built using LTX CAD files and divided into a regular mesh for computing the evolution of coupled electromagnetic vector quantities through time and space. Applicable boundary conditions and symmetries are analyzed. Comparisons with measured data, results from a 2-D code, and results from a 3-D code designed specifically for LTX demonstrate the possible benefits and limitations of using this commercial code.

  1. 3D position estimation using a single coil and two magnetic field sensors.

    PubMed

    Tadayon, P; Staude, G; Felderhoff, T

    2015-01-01

    This paper presents an algorithm which enables the estimation of relative 3D position of a sensor module with two magnetic sensors with respect to a magnetic field source using a single transmitting coil. Starting with the description of the ambiguity problem caused by using a single coil, a system concept comprising two sensors having a fixed spatial relation to each other is introduced which enables the unique determination of the sensors' position in 3D space. For this purpose, an iterative two-step algorithm is presented: In a first step, the data of one sensor is used to limit the number of possible position solutions. In a second step, the spatial relation between the sensors is used to determine the correct sensor position.

  2. A high-throughput in vitro ring assay for vasoactivity using magnetic 3D bioprinting

    PubMed Central

    Tseng, Hubert; Gage, Jacob A.; Haisler, William L.; Neeley, Shane K.; Shen, Tsaiwei; Hebel, Chris; Barthlow, Herbert G.; Wagoner, Matthew; Souza, Glauco R.

    2016-01-01

    Vasoactive liabilities are typically assayed using wire myography, which is limited by its high cost and low throughput. To meet the demand for higher throughput in vitro alternatives, this study introduces a magnetic 3D bioprinting-based vasoactivity assay. The principle behind this assay is the magnetic printing of vascular smooth muscle cells into 3D rings that functionally represent blood vessel segments, whose contraction can be altered by vasodilators and vasoconstrictors. A cost-effective imaging modality employing a mobile device is used to capture contraction with high throughput. The goal of this study was to validate ring contraction as a measure of vasoactivity, using a small panel of known vasoactive drugs. In vitro responses of the rings matched outcomes predicted by in vivo pharmacology, and were supported by immunohistochemistry. Altogether, this ring assay robustly models vasoactivity, which could meet the need for higher throughput in vitro alternatives. PMID:27477945

  3. Gravity data inversion to determine 3D topographycal density contrast of Banten area, Indonesia based on fast Fourier transform

    NASA Astrophysics Data System (ADS)

    Windhari, Ayuty; Handayani, Gunawan

    2015-04-01

    The 3D inversion gravity anomaly to estimate topographical density using a matlab source code from gridded data provided by Parker Oldenburg algorithm based on fast Fourier transform was computed. We extend and improved the source code of 3DINVERT.M invented by Gomez Ortiz and Agarwal (2005) using the relationship between Fourier transform of the gravity anomaly and the sum of the Fourier transform from the topography density. We gave density contrast between the two media to apply the inversion. FFT routine was implemented to construct amplitude spectrum to the given mean depth. The results were presented as new graphics of inverted topography density, the gravity anomaly due to the inverted topography and the difference between the input gravity data and the computed ones. It terminates when the RMS error is lower than pre-assigned value used as convergence criterion or until maximum of iterations is reached. As an example, we used the matlab program on gravity data of Banten region, Indonesia.

  4. Inverse current-source density method in 3D: reconstruction fidelity, boundary effects, and influence of distant sources.

    PubMed

    Łeski, Szymon; Wójcik, Daniel K; Tereszczuk, Joanna; Swiejkowski, Daniel A; Kublik, Ewa; Wróbel, Andrzej

    2007-01-01

    Estimation of the continuous current-source density in bulk tissue from a finite set of electrode measurements is a daunting task. Here we present a methodology which allows such a reconstruction by generalizing the one-dimensional inverse CSD method. The idea is to assume a particular plausible form of CSD within a class described by a number of parameters which can be estimated from available data, for example a set of cubic splines in 3D spanned on a fixed grid of the same size as the set of measurements. To avoid specificity of particular choice of reconstruction grid we add random jitter to the points positions and show that it leads to a correct reconstruction. We propose different ways of improving the quality of reconstruction which take into account the sources located outside the recording region through appropriate boundary treatment. The efficiency of the traditional CSD and variants of inverse CSD methods is compared using several fidelity measures on different test data to investigate when one of the methods is superior to the others. The methods are illustrated with reconstructions of CSD from potentials evoked by stimulation of a bunch of whiskers recorded in a slab of the rat forebrain on a grid of 4x5x7 positions.

  5. 3D multi-observable probabilistic inversion for the compositional and thermal structure of the lithosphere and sublithospheric upper mantle

    NASA Astrophysics Data System (ADS)

    Afonso, J. C.; Fullea, J.; Yang, Y.; Griffin, W. L.; Jones, A. G.; Connolly, J.; Lebedev, S.; O'Reilly, S. Y.

    2011-12-01

    High-resolution imaging and characterization of the thermal and compositional structure of the lithospheric and sublithospheric upper mantle are the basis for understanding the formation and evolution of the lithosphere and the interaction between the crust-mantle and lithosphere-asthenosphere systems. Unfortunately, such imaging and characterization using available geophysical-geochemical methods still present unsolved and technically challenging problems. In this contribution we present a new full-3D multi-observable inversion method particularly designed for high-resolution (regional) thermal and compositional mapping of the lithosphere and sublithospheric upper mantle. Ambient noise tomography, multiple plane wave earthquake tomography, magnetotelluric, thermal, thermodynamic, and potential field modelling are all combined in a single thermodynamic-geophysical framework and appraised within a general probabilistic (Bayesian) formulation. This circumvents the problems of strong non-linearity involved in traditional inversions, provides highly refined seismic information, minimizes the problem of trade-off between temperature and composition in wave speeds, offers critical insights into incompatibilities between traditional stand-alone methods, and takes advantage of a priori local geochemical information. Both synthetic models and preliminary results in real-case examples will be used to discuss the benefits, robustness, and limitations of this method.

  6. 3D low-beta magnetized plasma equilibria from external shaping

    NASA Astrophysics Data System (ADS)

    Hassam, A.; Tenbarge, J.; Landreman, M.; Dorland, W.; Sengupta, W.

    2016-10-01

    A 3D nonlinear dissipative MHD code is in development to allow relaxation to low-beta MHD equilibrium inside a shaped 3D conducting boundary with prescribed conserved axial magnetic flux and no external current. Formation of magnetic islands is expected. Heat sources would be eventually introduced to allow the possibility of non-stationary convection depending on the stability properties of the accessible MHD equilibria. The initial development will be done using the code UMHD. The initial emphasis will be on recovering expected physics in simpler 3D geometries. A primary objective is to minimize numerical boundary noise. In particular, codes which specify the normal magnetic field B.n on bounding surfaces are prone to noise generation. We plan to shape the boundary to conform to the desired field shape so that B.n is zero on the boundary. Non-orthogonal coordinates will be chosen to effect this. We will test noise reduction within the tangential field approach. Results obtained to date support this conjecture. Initial results from simple 2D code equilibria have been verified against analytic solution of equilibria in weak shaping. Initial results also recover the expected features of the Hahm- Kulsrud island formation solution. Work supported by US DOE.

  7. 3D Design, Contruction, and Field Analysis of CIS Main Dipole Magnets

    NASA Astrophysics Data System (ADS)

    Berg, G. P. A.; Fox, W.; Friesel, D. L.; Rinckel, T.

    1997-05-01

    The lattice for CIS ( Cooler Injection Synchroton ) requires four laminated 90^circ main dipole magnets with bending radius ρ = 1.273 m, EFL = 2 m, and an edge angle of 12^circ. Optimum Cooler injection and injection in the planned 15 GeV LISS ring requires operation up to about 1.75 T. Initial operation of 1 Hz, with later upgrade to 5 Hz is planned. We will present 2D and 3D field calculations used to optimize the shape of laminations and endpacks of the magnet. Endpacks are designed to determine edge angle and to compensate hexapole components, in particular above 1.4 T where saturation becomes significant. The large dipole curvature required a new type of dipole construction. Each magnet consists of wedge shaped blocks fabricated from stamped lamination of cold rolled low carbon iron. B-stage (dry) epopy was used for bonding and insulation. The end blocks are machined to include the calculated 3D shape of the endpacks. All four magnets were mapped in the field range from 0.3 T - 1.8 T. Comparison of calculations and data in terms of B(I) curves, EFL, edge angle, and hexapole component as function of field excitation will be presented. The constructed magnets are well within expected specifications.

  8. Crustal and Uppermost Mantle Structure of the Atlas Mountains of Morocco Revealed from 3-D Inversion of Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Kiyan, D.; Jones, A. G.; Fullea, J.; Ledo, J.; Siniscalchi, A.; Romano, G.

    2013-12-01

    The overarching objectives of the second phase of the PICASSO (Program to Investigate Convective Alboran Sea System Overturn) project and the concomitant TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROSCORES TOPO-EUROPE project) project are (i) to provide new electrical conductivity constraints on the crustal and lithospheric structures of the Atlas Mountains, and (ii) to test the hypotheses for explaining the observation of a 'missing' mantle root inferred from surface heat flow, gravity and geoid anomalies, elevation and seismic data modeling (i.e. Zeyen et al., 2005; Teixell et al., 2005; Fullea et al., 2010). We present the results from three-dimensional (3-D) MT inversion of data from two MT profiles employing the parallel version of Modular system for Electromagnetic inversion (ModEM; Egbert & Kelbert, 2012) code. For the profile in eastern Morocco, passing through Midelt, a distinct conductivity difference between the Middle-High Atlas (conductive) and Anti Atlas (resistive) correlates with the South Atlas Front fault, the depth extent of which appears to be limited to the uppermost mantle (approximately 55 km). In all inverse solutions, the crust and the upper mantle show a resistive signature (750 Ωm - 1,000 Ωm) beneath the Anti Atlas to a depth of 100 km, which is the part of stable West African Craton. Our results are at variance with the proposed thin lithosphere beneath the Middle-High Atlas as we see no evidence for a shallow asthenosphere. Our second profile lies in western Morocco traversing through Marrakech. For the first time, the electrical resistivity distribution in the crust and in the upper mantle of Western High Atlas has been studied. Our 3-D resistivity model shows that conductive (1-20 Ωm) western High Atlas is confined by two resistive basins (>1,000 Ωm), Souss basin to the south and Houz basin to the north. At the southern boundary of the western High Atlas

  9. OpenHVSR: imaging the subsurface 2D/3D elastic properties through multiple HVSR modeling and inversion

    NASA Astrophysics Data System (ADS)

    Bignardi, S.; Mantovani, A.; Abu Zeid, N.

    2016-08-01

    OpenHVSR is a computer program developed in the Matlab environment, designed for the simultaneous modeling and inversion of large Horizontal-to-Vertical Spectral Ratio (HVSR or H/V) datasets in order to construct 2D/3D subsurface models (topography included). The program is designed to provide a high level of interactive experience to the user and still to be of intuitive use. It implements several effective and established tools already present in the code ModelHVSR by Herak (2008), and many novel features such as: -confidence evaluation on lateral heterogeneity -evaluation of frequency dependent single parameter impact on the misfit function -relaxation of Vp/Vs bounds to allow for water table inclusion -a new cost function formulation which include a slope dependent term for fast matching of peaks, which greatly enhances convergence in case of low quality HVSR curves inversion -capability for the user of editing the subsurface model at any time during the inversion and capability to test the changes before acceptance. In what follows, we shall present many features of the program and we shall show its capabilities on both simulated and real data. We aim to supply a powerful tool to the scientific and professional community capable of handling large sets of HSVR curves, to retrieve the most from their microtremor data within a reduced amount of time and allowing the experienced scientist the necessary flexibility to integrate into the model their own geological knowledge of the sites under investigation. This is especially desirable now that microtremor testing has become routinely used. After testing the code over different datasets, both simulated and real, we finally decided to make it available in an open source format. The program is available by contacting the authors.

  10. Magnetic engineering in 3d transition metals on phosphorene by strain

    NASA Astrophysics Data System (ADS)

    Cai, Xiaolin; Niu, Chunyao; Wang, Jianjun; Yu, Weiyang; Ren, XiaoYan; Zhu, Zhili

    2017-04-01

    Using first-principles density functional theory (DFT) calculations, we systematically investigate the strain effects on the adsorption energies, magnetic ordering and electronic properties of 3d transition metal (TM) atoms (from Sc to Co) adsorbed on phosphorene (P). We find that the adsorption energy of TM can be enhanced by compressive strain whereas weakened by tensile strain. Our results show that strain plays a decisive role in the magnetic moments as well as the magnetic coupling states of TM adatoms. Importantly, the transitions from antiferromagnetic (AFM) state to ferromagnetic (FM) state or to another different AFM ordering can be induced by strain effect. In addition, we observe the semiconductor to metal or half-metal transitions in some TM@P systems by applying strain. Our findings shed a new light on precisely engineering the magnetic properties and electronic properties of the TM@P systems, which will have great potential applications in spin electronics and other related fields.

  11. A 3-D Magnetic Analysis of a Linear Alternator For a Stirling Power System

    NASA Technical Reports Server (NTRS)

    Geng, Steven M.; Schwarze, Gene E.; Niedra, Janis M.

    2000-01-01

    The NASA Glenn Research Center and the Department of Energy (DOE) are developing advanced radioisotope Stirling convertors, under contract with Stirling Technology Company (STC), for space applications. Of critical importance to the successful development of the Stirling convertor for space power applications is the development of a lightweight and highly efficient linear alternator. This paper presents a 3-D finite element method (FEM) approach for evaluating Stirling convertor linear alternators. Preliminary correlations with open-circuit voltage measurements provide an encouraging level of confidence in the model. Spatial plots of magnetic field strength (H) are presented in the region of the exciting permanent magnets. These plots identify regions of high H, where at elevated temperature and under electrical load, the potential to alter the magnetic moment of the magnets exists. This implies the need for further testing and analysis.

  12. Cross modality registration of video and magnetic tracker data for 3D appearance and structure modeling

    NASA Astrophysics Data System (ADS)

    Sargent, Dusty; Chen, Chao-I.; Wang, Yuan-Fang

    2010-02-01

    The paper reports a fully-automated, cross-modality sensor data registration scheme between video and magnetic tracker data. This registration scheme is intended for use in computerized imaging systems to model the appearance, structure, and dimension of human anatomy in three dimensions (3D) from endoscopic videos, particularly colonoscopic videos, for cancer research and clinical practices. The proposed cross-modality calibration procedure operates this way: Before a colonoscopic procedure, the surgeon inserts a magnetic tracker into the working channel of the endoscope or otherwise fixes the tracker's position on the scope. The surgeon then maneuvers the scope-tracker assembly to view a checkerboard calibration pattern from a few different viewpoints for a few seconds. The calibration procedure is then completed, and the relative pose (translation and rotation) between the reference frames of the magnetic tracker and the scope is determined. During the colonoscopic procedure, the readings from the magnetic tracker are used to automatically deduce the pose (both position and orientation) of the scope's reference frame over time, without complicated image analysis. Knowing the scope movement over time then allows us to infer the 3D appearance and structure of the organs and tissues in the scene. While there are other well-established mechanisms for inferring the movement of the camera (scope) from images, they are often sensitive to mistakes in image analysis, error accumulation, and structure deformation. The proposed method using a magnetic tracker to establish the camera motion parameters thus provides a robust and efficient alternative for 3D model construction. Furthermore, the calibration procedure does not require special training nor use expensive calibration equipment (except for a camera calibration pattern-a checkerboard pattern-that can be printed on any laser or inkjet printer).

  13. Evaluation of Gastric Volumes: Comparison of 3-D Ultrasound and Magnetic Resonance Imaging.

    PubMed

    Buisman, Wijnand J; Mauritz, Femke A; Westerhuis, Wouter E; Gilja, Odd Helge; van der Zee, David C; van Herwaarden-Lindeboom, Maud Y A

    2016-07-01

    To investigate gastric accommodation, accurate measurements of gastric volumes are necessary. An excellent technique to measure gastric volumes is dynamic magnetic resonance imaging (MRI). Unfortunately, dynamic MRI is expensive and not always available. A new 3-D ultrasound (US) method using a matrix transducer was developed to measure gastric volumes. In this prospective study, 14 healthy volunteers underwent a dynamic MRI and a 3-D US. Gastric volumes were calculated with intra-gastric liquid content and total gastric volume. Mean postprandial liquid gastric content was 397 ± 96.5 mL. Mean volume difference was 1.0 mL with limits of agreement of -8.9 to 10.9 mL. When gastric air was taken into account, mean total gastric volume was 540 ± 115.4 mL SD. Mean volume difference was 2.3 mL with limits of agreement of -21.1 to 26.4 mL. The matrix 3-D US showed excellent agreement with dynamic MRI. Therefore matrix 3-D US is a reliable alternative to measure gastric volumes.

  14. Steady state reconnection at a single 3D magnetic null point

    NASA Astrophysics Data System (ADS)

    Galsgaard, K.; Pontin, D. I.

    2011-05-01

    Aims: We systematically stress a rotationally symmetric 3D magnetic null point by advecting the opposite footpoints of the spine axis in opposite directions. This stress eventually concentrates in the vicinity of the null point, thereby forming a local current sheet through which magnetic reconnection takes place. The aim is to look for a steady state evolution of the current sheet dynamics, which may provide scaling relations for various characteristic parameters of the system. Methods: The evolution is followed by solving numerically the non-ideal MHD equations in a Cartesian domain. The null point is embedded in an initially constant density and temperature plasma. Results: It is shown that a quasi-steady reconnection process can be set up at a 3D null by continuous shear driving. It appears that a true steady state is unlikely to be realised because the current layer tends to grow until it is restricted by the geometry of the computational domain and the imposed driving profile. However, ratios between characteristic quantities clearly settle after some time to stable values, so that the evolution is quasi-steady. The experiments show a number of scaling relations, but they do not provide a clear consensus for extending to lower magnetic resistivity or faster driving velocities. More investigations are needed to fully clarify the properties of current sheets at magnetic null points.

  15. Magnetospheric Magnetic Reconnection with Southward IMF by a 3D EMPM Simulation

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Yan, X. Y.; Cai, D. S.; Lembege, B.

    2004-01-01

    We report our new simulation results on magnetospheric magnetic reconnection with southward IMF using a 3D EMPM model, with greater resolution and more particles using the parallelized 3D HPF TRISTAN code on VPP5000 supercomputer. Main parameters used in the new simulation are: domain size is 215 x 145 x 145, grid size = 0.5 Earth radius, initial particle number is 16 per cell, the IMF is southward. Arrival of southward IMF will cause reconnection in the magnetopause, thus allowing particles to enter into the inner magnetosphere. Sunward and tailward high particle flow are observed by satellites, and these phenomena are also observed in the simulation near the neutral line (X line) of the near-Earth magnetotail. This high particle flow goes along with the reconnected island. The magnetic reconnection process contributes to direct plasma entry between the magnetosheath to the inner magnetosphere and plasma sheet, in which the entry process eats the magnetosheath plasma to plasma sheet temperatures. We investigate magnetic, electric fields, density, and current during this magnetic reconnection with southward IMF. Further investigation with this simulation will provide insight into unsolved problems, such as the triggering of storms and substorms, and the storm-substorm relationship. New results will be presented at the meeting.

  16. An approach to 3D magnetic field calculation using numerical and differential algebra methods

    SciTech Connect

    Caspi, S.; Helm, M.; Laslett, L.J.; Brady, V.O.

    1992-07-17

    Motivated by the need for new means for specification and determination of 3D fields that are produced by electromagnetic lens elements in the region interior to coil windings and seeking to obtain techniques that will be convenient for accurate conductor placement and dynamical study of particle motion, we have conveniently gene the representation of a 2D magnetic field to 3D. We have shown that the 3 dimensioal magnetic field components of a multipole magnet in the curl-fire divergence-fire region near the axis r=0 can be derived from one dimensional functions A{sub n}(z) and their derivatives (part 1). In the region interior to coil windings of accelerator magnets the three spatial components of magnet fields can be expressed in terms of harmonic components'' proportional to functions sin (n{theta}) or cos (n{theta}) of the azimuthal angle. The r,z dependence of any such component can then be expressed in terms of powers of r times functions A{sub n}(z) and their derivatives. For twodimensional configurations B{sub z} of course is identically zero, the derivatives of A{sub n}(z) vanish, and the harmonic components of the transverse field then acquire a simple proportionality B{sub r,n} {proportional to} r{sup n-1} sin (n{theta}),B{sub {theta},n} {proportional to} r{sup n-1} cos (n{theta}), whereas in a 3-D configuration the more complex nature of the field gives rise to additional so-called psuedomultipole'' components as judged by additional powers of r required in the development of the field. Computation of the 3-D magnetic field arising at a sequence of field points, as a direct result of a specified current configuration or coil geometry, can be calculated explicitly through use of the Biot-Savart law and from such data the coefficients can then be derived for a general development of the type indicated above. We indicate, discuss, and illustrate two means by which this development may be performed.

  17. Effects of magnetic ripple on 3D equilibrium and alpha particle confinement in the European DEMO

    NASA Astrophysics Data System (ADS)

    Pfefferlé, D.; Cooper, W. A.; Fasoli, A.; Graves, J. P.

    2016-11-01

    An assessment of alpha particle confinement is performed in the European DEMO reference design. 3D MHD equilibria with nested flux-surfaces and single magnetic axis are obtained with the VMEC free-boundary code, thereby including the plasma response to the magnetic ripple created by the finite number of TF coils. Populations of fusion alphas that are consistent with the equilibrium profiles are evolved until slowing-down with the VENUS-LEVIS orbit code in the guiding-centre approximation. Fast ion losses through the last-closed flux-surface are numerically evaluated with two ripple models: (1) using the 3D equilibrium and (2) algebraically adding the non-axisymmetric ripple perturbation to the 2D equilibrium. By virtue of the small ripple field and its non-resonant nature, both models quantitatively agree. Differences are however noted in the toroidal location of particles losses on the last-closed flux-surface, which in the first case is 3D and in the second not. Superbanana transport, i.e. ripple-well trapping and separatrix crossing, is expected to be the dominant loss mechanism, the strongest effect on alphas being between 100-200 KeV. Above this, stochastic ripple diffusion is responsible for a rather weak loss rate, as the stochastisation threshold is observed numerically to be higher than analytic estimates. The level of ripple in the current 18 TF coil design of the European DEMO is not found to be detrimental to fusion alpha confinement.

  18. Inverse scattering problem in turbulent magnetic fluctuations

    NASA Astrophysics Data System (ADS)

    Treumann, Rudolf A.; Baumjohann, Wolfgang; Narita, Yasuhito

    2016-08-01

    We apply a particular form of the inverse scattering theory to turbulent magnetic fluctuations in a plasma. In the present note we develop the theory, formulate the magnetic fluctuation problem in terms of its electrodynamic turbulent response function, and reduce it to the solution of a special form of the famous Gelfand-Levitan-Marchenko equation of quantum mechanical scattering theory. The last of these applies to transmission and reflection in an active medium. The theory of turbulent magnetic fluctuations does not refer to such quantities. It requires a somewhat different formulation. We reduce the theory to the measurement of the low-frequency electromagnetic fluctuation spectrum, which is not the turbulent spectral energy density. The inverse theory in this form enables obtaining information about the turbulent response function of the medium. The dynamic causes of the electromagnetic fluctuations are implicit to it. Thus, it is of vital interest in low-frequency magnetic turbulence. The theory is developed until presentation of the equations in applicable form to observations of turbulent electromagnetic fluctuations as input from measurements. Solution of the final integral equation should be done by standard numerical methods based on iteration. We point to the possibility of treating power law fluctuation spectra as an example. Formulation of the problem to include observations of spectral power densities in turbulence is not attempted. This leads to severe mathematical problems and requires a reformulation of inverse scattering theory. One particular aspect of the present inverse theory of turbulent fluctuations is that its structure naturally leads to spatial information which is obtained from the temporal information that is inherent to the observation of time series. The Taylor assumption is not needed here. This is a consequence of Maxwell's equations, which couple space and time evolution. The inversion procedure takes advantage of a particular

  19. Analysis of the 3D magnetic field and its errors for undulators with iron poles

    SciTech Connect

    Ingold, G.; Bahrdt, J.; Gaupp, A.

    1995-12-31

    The attainable field strength and field quality, such as the optical phase error, the electron beam displacement within the undulator and higher order multipoles of the magnetic field, are discussed. These issues are critical to the design and construction of short period undulators for use in short wavelength FEL or for operation in third generation light sources. We discuss two approaches: (i) For superferric undulators the construction of a full length device would rely on the optimum sorting of precision machined undulator segments. Magnetic data on segments with 20 periods (period length 8.80mm) will be presented. (ii) For hybrid undulators the sorting has to be done on individual poles and magnets. For this approach typical error sources such as machining tolerances, magnetization errors of the permanent magnet material and assembly errors are modeled in 3D and compared to induced errors on an existing hybrid undulator segment. In case of undulators having a full length of hundred periods at least five times as many individual parts have to be characterized. This should be done automatically where both the mechanical and magnetic data before and after the assembly of the magnetic structure are recorded in one step. A CNC programmable measuring device suitable for this task will shortly be presented.

  20. On the Estimation Accuracy of the 3D Body Center of Mass Trajectory during Human Locomotion: Inverse vs. Forward Dynamics

    PubMed Central

    Pavei, Gaspare; Seminati, Elena; Cazzola, Dario; Minetti, Alberto E.

    2017-01-01

    The dynamics of body center of mass (BCoM) 3D trajectory during locomotion is crucial to the mechanical understanding of the different gaits. Forward Dynamics (FD) obtains BCoM motion from ground reaction forces while Inverse Dynamics (ID) estimates BCoM position and speed from motion capture of body segments. These two techniques are widely used by the literature on the estimation of BCoM. Despite the specific pros and cons of both methods, FD is less biased and considered as the golden standard, while ID estimates strongly depend on the segmental model adopted to schematically represent the moving body. In these experiments a single subject walked, ran, (uni- and bi-laterally) skipped, and race-walked at a wide range of speeds on a treadmill with force sensors underneath. In all conditions a simultaneous motion capture (8 cameras, 36 markers) took place. 3D BCoM trajectories computed according to five marker set models of ID have been compared to the one obtained by FD on the same (about 2,700) strides. Such a comparison aims to check the validity of the investigated models to capture the “true” dynamics of gaits in terms of distance between paths, mechanical external work and energy recovery. Results allow to conclude that: (1) among gaits, race walking is the most critical in being described by ID, (2) among the investigated segmental models, those capturing the motion of four limbs and trunk more closely reproduce the subtle temporal and spatial changes of BCoM trajectory within the strides of most gaits, (3) FD-ID discrepancy in external work is speed dependent within a gait in the most unsuccessful models, and (4) the internal work is not affected by the difference in BCoM estimates. PMID:28337148

  1. Modeling Coastal Salinity in Quasi 2D and 3D Using a DUALEM-421 and Inversion Software.

    PubMed

    Davies, Gareth; Huang, Jingyi; Monteiro Santos, Fernando Acacio; Triantafilis, John

    2015-01-01

    Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium-large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time-consuming. Alternatively, frequency-domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM-421 and EM4Soil inversion software package are used to develop a quasi two- (2D) and quasi three-dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (<10 mS/m) associated with the incipient dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium-large scale drivers including local wave climate and morphology along this wave-dominated beach. Further research is required to elucidate the influence of spring-neap tidal cycles, contrasting beach morphological states and sea level rise.

  2. On the Estimation Accuracy of the 3D Body Center of Mass Trajectory during Human Locomotion: Inverse vs. Forward Dynamics.

    PubMed

    Pavei, Gaspare; Seminati, Elena; Cazzola, Dario; Minetti, Alberto E

    2017-01-01

    The dynamics of body center of mass (BCoM) 3D trajectory during locomotion is crucial to the mechanical understanding of the different gaits. Forward Dynamics (FD) obtains BCoM motion from ground reaction forces while Inverse Dynamics (ID) estimates BCoM position and speed from motion capture of body segments. These two techniques are widely used by the literature on the estimation of BCoM. Despite the specific pros and cons of both methods, FD is less biased and considered as the golden standard, while ID estimates strongly depend on the segmental model adopted to schematically represent the moving body. In these experiments a single subject walked, ran, (uni- and bi-laterally) skipped, and race-walked at a wide range of speeds on a treadmill with force sensors underneath. In all conditions a simultaneous motion capture (8 cameras, 36 markers) took place. 3D BCoM trajectories computed according to five marker set models of ID have been compared to the one obtained by FD on the same (about 2,700) strides. Such a comparison aims to check the validity of the investigated models to capture the "true" dynamics of gaits in terms of distance between paths, mechanical external work and energy recovery. Results allow to conclude that: (1) among gaits, race walking is the most critical in being described by ID, (2) among the investigated segmental models, those capturing the motion of four limbs and trunk more closely reproduce the subtle temporal and spatial changes of BCoM trajectory within the strides of most gaits, (3) FD-ID discrepancy in external work is speed dependent within a gait in the most unsuccessful models, and (4) the internal work is not affected by the difference in BCoM estimates.

  3. An orientation measurement method based on Hall-effect sensors for permanent magnet spherical actuators with 3D magnet array.

    PubMed

    Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

    2014-10-24

    An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators.

  4. Magnetic helicity conservation and inverse energy cascade in electron magnetohydrodynamic wave packets.

    PubMed

    Cho, Jungyeon

    2011-05-13

    Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.

  5. 3D mapping of neuronal migration in the embryonic mouse brain with magnetic resonance microimaging.

    PubMed

    Deans, Abby E; Wadghiri, Youssef Zaim; Aristizábal, Orlando; Turnbull, Daniel H

    2015-07-01

    A prominent feature of the developing mammalian brain is the widespread migration of neural progenitor (NP) cells during embryogenesis. A striking example is provided by NP cells born in the ventral forebrain of mid-gestation stage mice, which subsequently migrate long distances to their final positions in the cortex and olfactory bulb. Previous studies have used two-dimensional histological methods, making it difficult to analyze three-dimensional (3D) migration patterns. Unlike histology, magnetic resonance microimaging (micro-MRI) is a non-destructive, quantitative and inherently 3D imaging method for analyzing mouse embryos. To allow mapping of migrating NP cells with micro-MRI, cells were labeled in situ in the medial (MGE) and lateral (LGE) ganglionic eminences, using targeted in utero ultrasound-guided injection of micron-sized particles of iron-oxide (MPIO). Ex vivo micro-MRI and histology were then performed 5-6days after injection, demonstrating that the MPIO had magnetically labeled the migrating NP populations, which enabled 3D visualization and automated segmentation of the labeled cells. This approach was used to analyze the distinct patterns of migration from the MGE and LGE, and to construct rostral-caudal migration maps from each progenitor region. Furthermore, abnormal migratory phenotypes were observed in Nkx2.1(-/-) embryos, most notably a significant increase in cortical neurons derived from the Nkx2.1(-/-) LGE. Taken together, these results demonstrate that MPIO labeling and micro-MRI provide an efficient and powerful approach for analyzing 3D cell migration patterns in the normal and mutant mouse embryonic brain.

  6. Treatment envelope evaluation in transcranial magnetic resonance-guided focused ultrasound utilizing 3D MR thermometry

    PubMed Central

    2014-01-01

    Background Current clinical targets for transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS) are all located close to the geometric center of the skull convexity, which minimizes challenges related to focusing the ultrasound through the skull bone. Non-central targets will have to be reached to treat a wider variety of neurological disorders and solid tumors. Treatment envelope studies utilizing two-dimensional (2D) magnetic resonance (MR) thermometry have previously been performed to determine the regions in which therapeutic levels of FUS can currently be delivered. Since 2D MR thermometry was used, very limited information about unintended heating in near-field tissue/bone interfaces could be deduced. Methods In this paper, we present a proof-of-concept treatment envelope study with three-dimensional (3D) MR thermometry monitoring of FUS heatings performed in a phantom and a lamb model. While the moderate-sized transducer used was not designed for transcranial geometries, the 3D temperature maps enable monitoring of the entire sonication field of view, including both the focal spot and near-field tissue/bone interfaces, for full characterization of all heating that may occur. 3D MR thermometry is achieved by a combination of k-space subsampling and a previously described temporally constrained reconstruction method. Results We present two different types of treatment envelopes. The first is based only on the focal spot heating—the type that can be derived from 2D MR thermometry. The second type is based on the relative near-field heating and is calculated as the ratio between the focal spot heating and the near-field heating. This utilizes the full 3D MR thermometry data achieved in this study. Conclusions It is shown that 3D MR thermometry can be used to improve the safety assessment in treatment envelope evaluations. Using a non-optimal transducer, it is shown that some regions where therapeutic levels of FUS can be delivered, as suggested by

  7. Effect of Resonant Magnetic Perturbations on 3D equilibria in the MST RFP

    NASA Astrophysics Data System (ADS)

    Munaretto, Stefano

    2015-11-01

    The orientation of 3D, stellarator-like equilibria in the MST RFP can now be controlled with application of an m = 1 RMP. This has led to greatly improved diagnosis, revealing enhancements in both the central electron temperature and density. Coupled to a recent advance in the V3FIT code, reconstructions of the 3D equilibria have also been dramatically improved. The RMP also inhibits the generation of high-energy >20 keV electrons that is otherwise common with the 3D state. This state occurs when the normally broad spectrum of core-resonant m = 1 tearing modes condenses, with the innermost resonant mode growing to large amplitude, reaching ~ 8% of the axisymmetric field strength. This occurs in plasmas of sufficiently large Lundquist number ~ IpTe3/2, and the duration of the state is maximized with zero applied Bt (infinite toroidal beta). As the dominant mode grows, eddy current in MST's conducting shell slows the mode's rotation. This leads to locking of the 3D structure, but with an orientation that varies randomly shot to shot, making diagnosis difficult. An m = 1 RMP can now be applied with an array of saddle coils at the vertical insulated cut in the shell. With an amplitude br/B ~ 10% and a tailored temporal waveform, the RMP can force the 3D structure into any desired orientation relative to MST's diagnostics. A recent advance in V3FIT allows calculation of the substantial helical image current flowing in MST's shell, which has in turn allowed self-consistent utilization of both external and internal (Faraday rotation) measurements of the magnetic field. The ORBIT code predicts reduced stochasticity and improved confinement of high-energy electrons within the 3D structure. The suppression of these electrons by the m = 1 RMP may reflect a change to the central magnetic topology. The generation of these electrons is unaffected by non-resonant perturbations, such as m = 3. Supported by the US DOE.

  8. 3-D magnetotelluric inversion including topography using deformed hexahedral edge finite elements and direct solvers parallelized on SMP computers - Part I: forward problem and parameter Jacobians

    NASA Astrophysics Data System (ADS)

    Kordy, M.; Wannamaker, P.; Maris, V.; Cherkaev, E.; Hill, G.

    2016-01-01

    We have developed an algorithm, which we call HexMT, for 3-D simulation and inversion of magnetotelluric (MT) responses using deformable hexahedral finite elements that permit incorporation of topography. Direct solvers parallelized on symmetric multiprocessor (SMP), single-chassis workstations with large RAM are used throughout, including the forward solution, parameter Jacobians and model parameter update. In Part I, the forward simulator and Jacobian calculations are presented. We use first-order edge elements to represent the secondary electric field (E), yielding accuracy O(h) for E and its curl (magnetic field). For very low frequencies or small material admittivities, the E-field requires divergence correction. With the help of Hodge decomposition, the correction may be applied in one step after the forward solution is calculated. This allows accurate E-field solutions in dielectric air. The system matrix factorization and source vector solutions are computed using the MKL PARDISO library, which shows good scalability through 24 processor cores. The factorized matrix is used to calculate the forward response as well as the Jacobians of electromagnetic (EM) field and MT responses using the reciprocity theorem. Comparison with other codes demonstrates accuracy of our forward calculations. We consider a popular conductive/resistive double brick structure, several synthetic topographic models and the natural topography of Mount Erebus in Antarctica. In particular, the ability of finite elements to represent smooth topographic slopes permits accurate simulation of refraction of EM waves normal to the slopes at high frequencies. Run-time tests of the parallelized algorithm indicate that for meshes as large as 176 × 176 × 70 elements, MT forward responses and Jacobians can be calculated in ˜1.5 hr per frequency. Together with an efficient inversion parameter step described in Part II, MT inversion problems of 200-300 stations are computable with total run times

  9. Structure of Alluvial Valleys from 3-D Gravity Inversion: The Low Andarax Valley (Almería, Spain) Test Case

    NASA Astrophysics Data System (ADS)

    Camacho, Antonio G.; Carmona, Enrique; García-Jerez, Antonio; Sánchez-Martos, Francisco; Prieto, Juan F.; Fernández, José; Luzón, Francisco

    2015-11-01

    This paper presents a gravimetric study (based on 382 gravimetric stations in an area about 32 km2) of a nearly flat basin: the Low Andarax valley. This alluvial basin, close to its river mouth, is located in the extreme south of the province of Almería and coincides with one of the existing depressions in the Betic Cordillera. The paper presents new methodological work to adapt a published inversion approach (GROWTH method) to the case of an alluvial valley (sedimentary stratification, with density increase downward). The adjusted 3D density model reveals several features in the topography of the discontinuity layers between the calcareous basement (2,700 kg/m3) and two sedimentary layers (2,400 and 2,250 kg/m3). We interpret several low density alignments as corresponding to SE faults striking about N140-145°E. Some detected basement elevations (such as the one, previously known by boreholes, in Viator village) are apparently connected with the fault pattern. The outcomes of this work are: (1) new gravimetric data, (2) new methodological options, and (3) the resulting structural conclusions.

  10. 3D density model of the upper mantle of Asia based on inversion of gravity and seismic tomography data

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; Stolk, Ward; Tesauro, Magdala; El Khrepy, Sami; Al-Arifi, Nassir; Beekman, Fred; Cloetingh, Sierd A. P. L.

    2016-11-01

    We construct a new-generation 3D density model of the upper mantle of Asia and its surrounding areas based on a joint interpretation of several data sets. A recent model of the crust combining nearly all available seismic data is employed to calculate the impact of the crust on the gravity anomalies and observed topography and to estimate the residual mantle anomalies and residual topography. These fields are jointly inverted to calculate the density variations in the lithosphere and upper mantle down to 325 km. As an initial approximation, we estimate density variations using a seismic tomography model. Seismic velocity variations are converted into temperatures and then to density variations based on mineral physics constraints. In the Occam-type inversion, we fit both the residual mantle gravity anomalies and residual topography by finding deviations to the initial model. The obtained corrections improve the resolution of the initial model and reflect important features of the mantle structure that are not well resolved by the seismic tomography. The most significant negative corrections of the upper mantle density, found in the Siberian and East European cratons, can be associated with depleted mantle material. The most pronounced positive density anomalies are found beneath the Tarim and South Caspian basins, Barents Sea, and Bay of Bengal. We attribute these anomalies to eclogites in the uppermost mantle, which have substantially affected the evolution of the basins. Furthermore, the obtained results provide evidence for the presence of eclogites in the oceanic subducting mantle lithosphere.

  11. Using 3D Simulation of Elastic Wave Propagation in Laplace Domain for Electromagnetic-Seismic Inverse Modeling

    NASA Astrophysics Data System (ADS)

    Petrov, P.; Newman, G. A.

    2010-12-01

    -Fourier domain we had developed 3D code for full-wave field simulation in the elastic media which take into account nonlinearity introduced by free-surface effects. Our approach is based on the velocity-stress formulation. In the contrast to conventional formulation we defined the material properties such as density and Lame constants not at nodal points but within cells. This second order finite differences method formulated in the cell-based grid, generate numerical solutions compatible with analytical ones within the range errors determinate by dispersion analysis. Our simulator will be embedded in an inversion scheme for joint seismic- electromagnetic imaging. It also offers possibilities for preconditioning the seismic wave propagation problems in the frequency domain. References. Shin, C. & Cha, Y. (2009), Waveform inversion in the Laplace-Fourier domain, Geophys. J. Int. 177(3), 1067- 1079. Shin, C. & Cha, Y. H. (2008), Waveform inversion in the Laplace domain, Geophys. J. Int. 173(3), 922-931. Commer, M. & Newman, G. (2008), New advances in three-dimensional controlled-source electromagnetic inversion, Geophys. J. Int. 172(2), 513-535. Newman, G. A., Commer, M. & Carazzone, J. J. (2010), Imaging CSEM data in the presence of electrical anisotropy, Geophysics, in press.

  12. Tuning the Origin of Magnetic Relaxation by Substituting the 3d or Rare-Earth Ions into Three Isostructural Cyano-Bridged 3d-4f Heterodinuclear Compounds.

    PubMed

    Zhang, Yan; Guo, Zhen; Xie, Shuang; Li, Hui-Li; Zhu, Wen-Hua; Liu, Li; Dong, Xun-Qing; He, Wei-Xun; Ren, Jin-Chao; Liu, Ling-Zhi; Powell, Annie K

    2015-11-02

    Three isostructural cyano-bridged 3d-4f compounds, [YFe(CN)6(hep)2(H2O)4] (1), [DyFe(CN)6(hep)2(H2O)4] (2), and [DyCo(CN)6(hep)2(H2O)4] (3), were successfully assembled by site-targeted substitution of the 3d or rare-earth ions. All compounds have been structurally characterized to display slightly distorted pentagonal-bipyramidal local coordination geometry around the rare-earth ions. Magnetic analyses revealed negligible magnetic coupling in compound 1, antiferromagnetic intradimer interaction in 2, and weak ferromagnetic coupling through dipolar-dipolar interaction in 3. Under an applied direct-current (dc) field, 1 (Hdc = 2.5 kOe, τ0 = 1.3 × 10(-7) s, and Ueff/kB = 23 K) and 3 (Hdc = 2.0 kOe, τ0 = 7.1 × 10(-11) s, and Ueff/kB = 63 K) respectively indicated magnetic relaxation behavior based on a single [Fe(III)]LS ion and a Dy(III) ion; nevertheless, 2 (Hdc = 2.0 kOe, τ0 = 9.7 × 10(-8) s, and Ueff/kB = 23 K) appeared to be a single-molecule magnet based on a cyano-bridged DyFe dimer. Compound 1, which can be regarded as a single-ion magnet of the [Fe(III)]LS ion linked to a diamagnetic Y(III) ion in a cyano-bridged heterodimer, represents one of the rarely investigated examples based on a single Fe(III) ion explored in magnetic relaxation behavior. It demonstrated that the introduction of intradimer magnetic interaction of 2 through a cyano bridge between Dy(III) and [Fe(III)]LS ions negatively affects the energy barrier and χ″(T) peak temperature compared to 3.

  13. Global 3-D imaging of mantle electrical conductivity based on inversion of observatory C-responses - I. An approach and its verification

    NASA Astrophysics Data System (ADS)

    Kuvshinov, Alexey; Semenov, Alexey

    2012-06-01

    We present a novel frequency-domain inverse solution to recover the 3-D electrical conductivity distribution in the mantle. The solution is based on analysis of local C-responses. It exploits an iterative gradient-type method - limited-memory quasi-Newton method - for minimizing the penalty function consisting of data misfit and regularization terms. The integral equation code is used as a forward engine to calculate responses and data misfit gradients during inversion. An adjoint approach is implemented to compute misfit gradients efficiently. Further improvements in computational load come from parallelizing the scheme with respect to frequencies, and from setting the most time-consuming part of the forward calculations - calculation of Green's tensors - apart from the inversion loop. Convergence, performance, and accuracy of our 3-D inverse solution are demonstrated with a synthetic numerical example. A companion paper applies the strategy set forth here to real data.

  14. Sawtooth mitigation in 3D MHD tokamak modelling with applied magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Bonfiglio, D.; Veranda, M.; Cappello, S.; Chacón, L.; Escande, D. F.

    2017-01-01

    The effect of magnetic perturbations (MPs) on the sawtoothing dynamics of the internal kink mode in the tokamak is discussed in the framework of nonlinear 3D MHD modelling. Numerical simulations are performed with the pixie3d code (Chacón 2008 Phys. Plasmas 15 056103) based on a D-shaped configuration in toroidal geometry. MPs are applied as produced by two sets of coils distributed along the toroidal direction, one set located above and the other set below the outboard midplane, like in experimental devices such as DIII-D and ASDEX Upgrade. The capability of n  =  1 MPs to affect quasi-periodic sawteeth is shown to depend on the toroidal phase difference Δ φ between the perturbations produced by the two sets of coils. In particular, sawtooth mitigation is obtained for the Δ φ =π phasing, whereas no significant effect is observed for Δ φ =0 . Numerical findings are explained by the interplay between different poloidal harmonics in the spectrum of applied MPs, and appear to be consistent with experiments performed in the DIII-D device. Sawtooth mitigation and stimulation of self-organized helical states by applied MPs have been previously demonstrated in both circular tokamak and reversed-field pinch (RFP) experiments in the RFX-mod device, and in related 3D MHD modelling.

  15. 3D Magnetic Measurements of Kink and Locked Modes in DIII-D

    NASA Astrophysics Data System (ADS)

    King, J. D.; Strait, E. J.; Hanson, J. M.; Paz-Soldan, C.; Logan, N. C.; Lanctot, M. J.; Shiraki, D.

    2013-10-01

    The DIII-D magnetics diagnostic has been greatly expanded to fully characterize non-axisymmetric ``3D'' fields. Five poloidal locations now recover n <= 3 , while new HFS arrays provide poloidal spectral resolution of 7.4 cm. Initial measurements suggest externally driven kink structures deviate from MARS-F and IPEC models. These variations extend to the ideal regime, where toroidal agreement is observed. The plasma response to an n = 3 RMP increases monotonically as beta increases and q95 decreases, contrary to predictions of a screening to kink valley. Finally, the temporal evolution of the 3D eigenstructure of a slowly rotating (5 Hz) quasi-static, born locked, tearing mode provides the first evidence of an appreciable n = 2 error field, and an estimate of the phase for future correction. This new 3D capability will be used to understand and optimize control of RWMs, NTV torque, ELMs, and error field correction to extend stable tokamak operation. Work supported in part by the US Department of Energy under DE-AC05-00OR22725, DE-FC02-04ER54698, DE-FG02-95ER54309, DE-AC02-09CH11466, DE-FG02-04ER54761 and DE-AC52-07NA27344.

  16. 3D kinematics of the tarsal joints from magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Hirsch, Bruce E.; Udupa, Jayaram K.; Okereke, Enyi; Hillstrom, Howard J.; Siegler, Sorin; Ringleb, Stacie I.; Imhauser, Carl W.

    2001-09-01

    We have developed a method for analyzing motion at skeletal joints based on the 3D reconstruction of magnetic resonance (MR) image data. Since the information about each voxel in MR images includes its location in the scanner, it follows that information is available for each organ whose 3D surface is computed from a series of MR slices. In addition, there is information on the shape and orientation of each organ, and the contact areas of adjacent bones. By collecting image data in different positions we can calculate the motion of the individual bones. We have used this method to study human foot bones, in order to understand normal and abnormal foot function. It has been used to evaluate patients with tarsal coalitions, various forms of pes planus, ankle sprains, and several other conditions. A newly described feature of this system is the ability to visualize the contact area at a joint, as determined by the region of minimum distance. The display of contact area helps understand abnormal joint function. Also, the use of 3D imaging reveals motions in joints which cannot otherwise be visualized, such as the subtalar joint, for more accurate diagnosis of joint injury.

  17. 3D In Vitro Model for Breast Cancer Research Using Magnetic Levitation and Bioprinting Method.

    PubMed

    Leonard, Fransisca; Godin, Biana

    2016-01-01

    Tumor microenvironment composition and architecture are known as a major factor in orchestrating the tumor growth and its response to various therapies. In this context, in vivo studies are necessary to evaluate the responses. However, while tumor cells can be of human origin, tumor microenvironment in the in vivo models is host-based. On the other hand, in vitro studies in a flat monoculture of tumor cells (the most frequently used in vitro tumor model) are unable to recapitulate the complexity of tumor microenvironment. Three-dimensional (3D) in vitro cell cultures of tumor cells have been proven to be an important experimental tool in understanding mechanisms of tumor growth, response to therapeutics, and transport of nutrients/drugs. We have recently described a novel tool to create 3D co-cultures of tumor cells and cells in the tumor microenvironment. Our method utilizes magnetic manipulation/levitation of the specific ratios of tumor cells and cells in the tumor microenvironment (from human or animal origin) aiding in the formation of tumor spheres with defined cellular composition and density, as quickly as within 24 h. This chapter describes the experimental protocols developed to model the 3D structure of the cancer environment using the above method.

  18. 3D in vitro model for breast cancer research using magnetic levitation and bioprinting method

    PubMed Central

    Leonard, Fransisca; Godin, Biana

    2016-01-01

    Summary Tumor microenvironment composition and architecture are known as a major factor in orchestrating the tumor growth and its response to various therapies. In this context, in vivo studies are necessary to evaluate the responses. However, while tumor cells can be of human origin, tumor microenvironment in the in vivo models is host-based. On the other hand, in vitro studies in a flat monoculture of tumor cells (the most frequently used in vitro tumor model) are unable to recapitulate the complexity of tumor microenvironment. Three-dimensional (3D) in vitro cell cultures of tumor cells have been proven to be an important experimental tool in understanding mechanisms of tumor growth, response to therapeutics and transport of nutrients/drugs. We have recently described a novel tool to create 3D co-cultures of tumor cells and cells in the tumor microenvironment. Our method utilizes magnetic manipulation/levitation of the specific ratios of tumor cells and cells in the tumor microenvironment (from human or animal origin) aiding in the formation of tumor spheres with defined cellular composition and density, as quickly as within 24 hours. This chapter describes the experimental protocols developed to model the 3D structure of the cancer environment using the above method. PMID:26820961

  19. Fast ion transport during applied 3D magnetic perturbations on DIII-D

    DOE PAGES

    Van Zeeland, Michael A.; Ferraro, N. M.; Grierson, Brian A.; ...

    2015-06-26

    In this paper, measurements show fast ion losses correlated with applied three-dimensional (3D) fields in a variety of plasmas ranging from L-mode to resonant magnetic perturbation (RMP) edge localized mode (ELM) suppressed H-mode discharges. In DIII-D L-mode discharges with a slowly rotatingmore » $n=2$ magnetic perturbation, scintillator detector loss signals synchronized with the applied fields are observed to decay within one poloidal transit time after beam turn-off indicating they arise predominantly from prompt loss orbits. Full orbit following using M3D-C1 calculations of the perturbed fields and kinetic profiles reproduce many features of the measured losses and points to the importance of the applied 3D field phase with respect to the beam injection location in determining the overall impact on prompt beam ion loss. Modeling of these results includes a self-consistent calculation of the 3D perturbed beam ion birth profiles and scrape-off-layer ionization, a factor found to be essential to reproducing the experimental measurements. Extension of the simulations to full slowing down timescales, including fueling and the effects of drag and pitch angle scattering, show the applied $n=3$ RMPs in ELM suppressed H-mode plasmas can induce a significant loss of energetic particles from the core. With the applied $n=3$ fields, up to 8.4% of the injected beam power is predicted to be lost, compared to 2.7% with axisymmetric fields only. These fast ions, originating from minor radii $$\\rho >0.7$$ , are predicted to be primarily passing particles lost to the divertor region, consistent with wide field-of-view infrared periscope measurements of wall heating in $n=3$ RMP ELM suppressed plasmas. Edge fast ion $${{\\text{D}}_{\\alpha}}$$ (FIDA) measurements also confirm a large change in edge fast ion profile due to the $n=3$ fields, where the effect was isolated by using short 50 ms RMP-off periods during which ELM suppression was maintained yet the fast ion profile

  20. Fast ion transport during applied 3D magnetic perturbations on DIII-D

    SciTech Connect

    Van Zeeland, Michael A.; Ferraro, N. M.; Grierson, Brian A.; Heidbrink, W. W.; Kramer, G. J.; Lasnier, C. J.; Pace, David C.; Allen, Steve L.; Chen, X.; Evans, T. E.; García-Muñoz, M.; Hanson, J. M.; Lanctot, M. J.; Lao, L. L.; Meyer, W. H.; Moyer, R. A.; Nazikian, R.; Orlov, D. M.; Paz-Soldan, C.; Wingen, A.

    2015-06-26

    In this paper, measurements show fast ion losses correlated with applied three-dimensional (3D) fields in a variety of plasmas ranging from L-mode to resonant magnetic perturbation (RMP) edge localized mode (ELM) suppressed H-mode discharges. In DIII-D L-mode discharges with a slowly rotating $n=2$ magnetic perturbation, scintillator detector loss signals synchronized with the applied fields are observed to decay within one poloidal transit time after beam turn-off indicating they arise predominantly from prompt loss orbits. Full orbit following using M3D-C1 calculations of the perturbed fields and kinetic profiles reproduce many features of the measured losses and points to the importance of the applied 3D field phase with respect to the beam injection location in determining the overall impact on prompt beam ion loss. Modeling of these results includes a self-consistent calculation of the 3D perturbed beam ion birth profiles and scrape-off-layer ionization, a factor found to be essential to reproducing the experimental measurements. Extension of the simulations to full slowing down timescales, including fueling and the effects of drag and pitch angle scattering, show the applied $n=3$ RMPs in ELM suppressed H-mode plasmas can induce a significant loss of energetic particles from the core. With the applied $n=3$ fields, up to 8.4% of the injected beam power is predicted to be lost, compared to 2.7% with axisymmetric fields only. These fast ions, originating from minor radii $\\rho >0.7$ , are predicted to be primarily passing particles lost to the divertor region, consistent with wide field-of-view infrared periscope measurements of wall heating in $n=3$ RMP ELM suppressed plasmas. Edge fast ion ${{\\text{D}}_{\\alpha}}$ (FIDA) measurements also confirm a large change in edge fast ion profile due to the $n=3$ fields, where the effect was isolated by using short 50 ms RMP-off periods during which ELM suppression was maintained yet the fast ion profile was allowed

  1. Magnetic Resonance Elastography: Inversions in Bounded Media

    PubMed Central

    Kolipaka, Arunark; McGee, Kiaran P.; Manduca, Armando; Romano, Anthony J.; Glaser, Kevin J.; Araoz, Philip A.; Ehman, Richard L.

    2009-01-01

    Magnetic resonance elastography (MRE) is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, MRE inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates and spherical shells using geometry-specific equations of motion. MRE and finite element modeling (FEM) of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from FEM and MRE data and a linear correlation of r2 ≥ 0.99 was observed between the stiffness values obtained using MRE and FEM data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. PMID:19780146

  2. Magnetic Damping of g-Jitter Driven Flows: 3-D Calculations

    NASA Technical Reports Server (NTRS)

    Shang, D. Y.; Li, B. Q.; deGroh, H. C.

    1997-01-01

    A 3-D numerical model is developed to represent the oscillating natural convection induced in a cylindrical cavity filled with Ga-doped germanium with and without the presence of an external magnetic field. The model is developed based on the penalty-finite element solution of the equations describing the transport of momentum, heat and solutal element as well as the electromagnetic field distribution in the melt pool. Automatic time step control is applied to help speed up the calculations. Numerical simulations are conducted to study the convection and magnetic damping effects as a function of frequency, directions and amplitudes of g-jitter and also the direction and magnitudes of the applied magnetic fields. The results show that the g-jitter driven flow is time dependent and exhibits a complex recirculating convection pattern in three dimensions and that an applied magnetic field can be employed to suppress this deleterious convective flow and both magnitude and orientation of the applied field are important in magnetic damping of the g-jitter induced convective flows.

  3. Heat Transfer Affected by Transverse Magnetic Field using 3D Modeling of Arc Plasma

    NASA Astrophysics Data System (ADS)

    Maeda, Yoshifumi; Tanaka, Tatsuro; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Gas shielded metal arc welding is used to join the various metal because this is the high quality joining technology. Thus, this welding is used for a welding of large buildings such as bridges and LNG tanks. However, the welding defect caused by the heat transfer decrement may occur with increasing the wind velocity. This is because that the convection loss increases because the arc deflects to leeward side with increasing the wind velocity. In order to prevent from the arc deflection, it is used that the transverse magnetic field is applied to the arc. However, the arc deflection occurs with increasing the transverse magnetic field excessively. The energy balance of the arc is changed with increasing the convection loss caused by the arc deflection, and the heat transfer to the anode decreases. Therefore, the analysis including the arc and anode is necessary to elucidate the heat transfer to the anode. In this paper, the heat transfer affected by the transverse magnetic field using 3D modeling of the arc plasma is elucidated. The heat transfer to the anode is calculated by using the EMTF(electromagnetic thermal fluid) simulation with increasing the transverse magnetic field. As a result, the heat transfer decreased with increasing the transverse magnetic field.

  4. 2D and 3D ordered arrays of Co magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Garcia, J.; Prida, V. M.; Vega, V.; Rosa, W. O.; Caballero-Flores, R.; Iglesias, L.; Hernando, B.

    2015-06-01

    Cobalt nanowire arrays spatially distributed in 2D and 3D arrangements have been performed by pulsed electrodeposition into the pores of planar and cylindrical nanoporous anodic alumina membranes, respectively. Morphological characterization points out the good filling factor reached by electroplated Co nanowires in both kinds of alumina membranes exhibiting hexagonally self-ordered porous structures. Co nanowires grown in both kinds of alumina templates exhibit the same crystalline phases. DC magnetometry and First Order Reversal Curve (FORC) analysis were carried out in order to determine the overall magnetic behavior for both nanowire array geometries. It is found that when the Co nanowires of two kinds of arrays are perpendicularly magnetized, both hysteresis loops are identical, suggesting that neither the intrinsic magnetic behavior of the nanowires nor the collective one depend on the arrays geometry. FORC analysis performed along the radial direction of the Co nanowire arrays embedded in the cylindrical alumina template reveals that the contribution of each nanowire to the magnetization reversal process involves its specific orientation with respect to the applied field direction. Furthermore, the comparison between the magnetic properties for both kinds of Co nanowire arrays allows discussing about the effect of the cylindrical geometry of the template on the magnetostatic interaction among nanowires.

  5. Calculating Pressure-Driven Current Near Magnetic Islands for 3D MHD Equilibria

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Dhanush; Reiman, Allan

    2016-10-01

    In general, 3D MHD equilibria in toroidal plasmas do not result in nested pressure surfaces. Instead, islands and chaotic regions appear in the equilibrium. Near small magnetic islands, the pressure varies within the flux surfaces, which has a significant effect on the pressure-driven current, introducing singularities. Previously, the MHD equilibrium current near a magnetic island was calculated, including the effect of ``stellarator symmetry,'' wherein the singular components of the pressure-driven current vanish [A. H. Reiman, Phys. Plasmas 23, 072502 (2016)]. Here we first solve for pressure in a cylindrical plasma from the heat diffusion equation, after adding a helical perturbation. We then numerically calculate the corresponding Pfirsch-Schluter current. At the small island limit, we compare the pressure-driven current with the previously calculated solution, and far from the island, we recover the solution for nested flux surfaces. Lastly, we compute the current for a toroidal plasma for symmetric and non-symmetric geometries.

  6. Study of the internal magnetic field of Mercury through 3D hybrid simulations

    NASA Astrophysics Data System (ADS)

    Leclercq, Ludivine; Marcel Chanteur, Gerard; Modolo, Ronan; Leblanc, Francois; Schmidt, Carl; Langlais, Benoît; Thebault, Erwan

    2016-10-01

    In 1974, Mariner 10 discovered the intrinsic magnetic field of Mercury which interacts with the solar wind, leading to the formation of a magnetosphere. In spite of the recent MESSENGER observations, this magnetosphere remains quite unknown, especially in the Southern hemisphere. In order to improve our understanding of the Hermean magnetosphere, and to prepare the Bepi-Colombo mission (ESA/JAXA), we simulated the magnetized environment of Mercury using the model named LatHyS (LATMOS Hybrid Simulation). LatHyS is a 3D parallel multi-species hybrid code which has been applied to Mars, Titan and Ganymede, which has recently be improved by the implementation of a multi-grid method allowing to refine the spatial resolution near the planetary object (40 km in the case of Mercury). In order to investigate the Hermean environment, several hybrid simulations have been performed considering different internal field models, and results are compared with MESSENGER observations.

  7. Improvements, Evaluation, and Application of 1D Vetem Inversion and Development and Application of 3D Vetem Inversion to Waste Pits at The Idaho National Engineering and Environmental Laboratory

    SciTech Connect

    Weng Cho Chew

    2004-10-27

    The project aim was the improvement, evaluation, and application of one dimensional (1D) inversion and development and application of three dimensional (3D) inversion to processing of data collected at waste pits at the Idaho National Engineering and Environmental Laboratory. The inversion methods were intended mainly for the Very Early Time Electromagnetic (VETEM) system which was designed to improve the state-of-the-art of electromagnetic imaging of the shallow (0 to about 5m) subsurface through electrically conductive soils.

  8. Effects of 2D and 3D Error Fields on the SAS Divertor Magnetic Topology

    NASA Astrophysics Data System (ADS)

    Trevisan, G. L.; Lao, L. L.; Strait, E. J.; Guo, H. Y.; Wu, W.; Evans, T. E.

    2016-10-01

    The successful design of plasma-facing components in fusion experiments is of paramount importance in both the operation of future reactors and in the modification of operating machines. Indeed, the Small Angle Slot (SAS) divertor concept, proposed for application on the DIII-D experiment, combines a small incident angle at the plasma strike point with a progressively opening slot, so as to better control heat flux and erosion in high-performance tokamak plasmas. Uncertainty quantification of the error fields expected around the striking point provides additional useful information in both the design and the modeling phases of the new divertor, in part due to the particular geometric requirement of the striking flux surfaces. The presented work involves both 2D and 3D magnetic error field analysis on the SAS strike point carried out using the EFIT code for 2D equilibrium reconstruction, V3POST for vacuum 3D computations and the OMFIT integrated modeling framework for data analysis. An uncertainty in the magnetic probes' signals is found to propagate non-linearly as an uncertainty in the striking point and angle, which can be quantified through statistical analysis to yield robust estimates. Work supported by contracts DE-FG02-95ER54309 and DE-FC02-04ER54698.

  9. New Era in 3-D Modeling of Convection and Magnetic Dynamos in Stellar Envelopes and Cores

    NASA Astrophysics Data System (ADS)

    Toomre, J.; Augustson, K. C.; Brown, B. P.; Browning, M. K.; Brun, A. S.; Featherstone, N. A.; Miesch, M. S.

    2012-09-01

    The recent advances in asteroseismology and spectropolarimetry are beginning to provide estimates of differential rotation and magnetic structures for a range of F and G-type stars possessing convective envelopes, and in A-type stars with convective cores. It is essential to complement such observational work with theoretical studies based on 3-D simulations of highly turbulent convection coupled to rotation, shear and magnetic fields in full spherical geometries. We have so employed the anelastic spherical harmonic (ASH) code, which deals with compressible magnetohydrodynamics (MHD) in spherical shells, to examine the manner in which the global-scale convection can establish differential rotation and meridional circulations under current solar rotation rates, and these make good contact with helioseismic findings. For younger G stars rotating 3 to 5 times faster than the current Sun, the convection establishes ever stronger angular velocity contrasts between their fast equators and slow poles, and these are accompanied by prominent latitudinal temperature contrasts as well. Turning to MHD simulation of magnetic dynamo action within these younger G stars, the resulting magnetism involves wreaths of strong toroidal magnetic fields (up to 50 to 100 kG strengths) in the bulk of the convection zone, typically of opposite polarity in the northern and southern hemispheres. These fields can persist for long intervals despite being pummeled by the fast convective downflows, but they can also exhibit field reversals and cycles. Turning to shallower convective envelopes in the more luminous F-type stars that range in mass from 1.2 to 1.4 solar masses and for various rotation rates, we find that the convection can again establish solar-like differential rotation profiles with a fast equator and slow poles, but the opposite is achieved at the slower rotation rates. The F stars are also capable of building strong magnetic fields, often as wreaths, through dynamo action. We also

  10. Three dimensional electrical conductivity model of the Northwestern US derived from 3-D inversion of USArray magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Meqbel, N. M.; Egbert, G. D.; Kelbert, A.

    2011-12-01

    Long period (10-20,000 s) magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental United States through the EMScope component of EarthScope. MT deployments in 2006-2011 have acquired data at 325 sites on an approximately regular grid, with the same nominal spacing as the USArray broadband seismic transportable array (~70 km). The MT sites span a rectangular area from NW Washington to NW Colorado. Here we present results of a 3-D inversion of the full data set. A number of conductive and resistive features appear consistently in the crust and upper mantle in essentially all of a large suite of 3-D inverse solutions. Extensive areas of high conductivity are found in the lower crust (up to a depth of ~ 40 km) beneath the Basin & Range in southeastern Oregon, as imaged by Patro and Egbert (2008). In our new model, this feature extends further to the south and to the east, where it merges with somewhat deeper (uppermost mantle) conductivities beneath the Yellowstone-Snake River Plain. This deeper feature, which extends from Yellowstone to the SW into northeastern Nevada, coincides with the track of the Yellowstone hotspot discussed e.g., in Smith et. al. (2008). The lower crust and the uppermost mantle in the northeastern part of the domain, covering the area from eastern Washington to Montana and continuing south to Wyoming, is generally resistive, with a few localized exceptions. This resistive zone coincides with high velocities discussed and interpreted, e.g., by Yang et. al. (2008) as thick, stable Proterozoic lithosphere. A number of large-scale anomalous features also appear consistently in the upper mantle, at depths of ~ 50 km to 300 km. Most striking is a zone of high resistivity on the western edge of the domain, beneath western Oregon, Washington and northern California in the area occupied by oceanic lithosphere of the Juan de Fuca Plate, which has subducted beneath the relatively more conductive

  11. A 3D model of crustal magnetization at the Pinacate Volcanic Field, NW Sonora, Mexico

    NASA Astrophysics Data System (ADS)

    García-Abdeslem, Juan; Calmus, Thierry

    2015-08-01

    The Pinacate Volcanic Field (PVF) is located near the western border of the southern Basin and Range province, in the State of Sonora NW Mexico, and within the Gulf of California Extensional Province. This volcanic field contains the shield volcano Santa Clara, which mainly consists of basaltic to trachytic volcanic rocks, and reaches an altitude of 1200 m. The PVF disrupts a series of discontinuous ranges of low topographic relief aligned in a NW direction, which consist mainly of Proterozoic metamorphic rocks and Proterozoic through Paleogene granitoids. The PVF covers an area of approximately 60 by 55 km, and includes more than 400 well-preserved cinder cones and vents and eight maar craters. It was active from about 1.7 Ma until about 13 ka. We have used the ages and magnetic polarities of the volcanic rocks, along with mapped magnetic anomalies and their inverse modeling to determine that the Pinacate Volcanic Field was formed during two volcanic episodes. The oldest one built the Santa Clara shield volcano of basaltic and trachytic composition, and occurred during the geomagnetic Matuyama Chron of reverse polarity, which also includes the normal polarity Jaramillo and Olduvai Subchrons, thus imprinting both normal and reverse magnetization in the volcanic products. The younger Pinacate series of basaltic composition represents monogenetic volcanic activity that extends all around the PVF and occurred during the subsequent geomagnetic Brunhes Chron of normal polarity. Magnetic anomalies toward the north of the Santa Clara volcano are the most intense in the PVF, and their inverse modeling indicates the presence of a large subsurface body magnetized in the present direction of the geomagnetic field. This suggests that the magma chambers at depth cooled below the Curie temperature during the Brunhes Chron.

  12. Particle energization in 3D magnetic reconnection of relativistic pair plasmas

    SciTech Connect

    Liu Wei; Yin Lin; Albright, B. J.; Bowers, K. J.; Liang, Edison P.; Li Hui

    2011-05-15

    We present large scale 3D particle-in-cell simulations to examine particle energization in magnetic reconnection of relativistic electron-positron (pair) plasmas. The initial configuration is set up as a relativistic Harris equilibrium without a guide field. These simulations are large enough to accommodate a sufficient number of tearing and kink modes. Contrary to the non-relativistic limit, the linear tearing instability is faster than the linear kink instability, at least in our specific parameters. We find that the magnetic energy dissipation is first facilitated by the tearing instability and followed by the secondary kink instability. Particles are mostly energized inside the magnetic islands during the tearing stage due to the spatially varying electric fields produced by the outflows from reconnection. Secondary kink instability leads to additional particle acceleration. Accelerated particles are, however, observed to be thermalized quickly. The large amplitude of the vertical magnetic field resulting from the tearing modes by the secondary kink modes further help thermalizing the non-thermal particles generated from the secondary kink instability. Implications of these results for astrophysics are briefly discussed.

  13. Stoner magnetism in an inversion layer

    NASA Astrophysics Data System (ADS)

    Golosov, D. I.

    2016-02-01

    Motivated by recent experimental work on magnetic properties of Si-MOSFETs, we report a calculation of magnetisation and susceptibility of electrons in an inversion layer, taking into account the co-ordinate dependence of electron wave function in the direction perpendicular to the plane. It is assumed that the inversion-layer carriers interact via a contact repulsive potential, which is treated at a mean-field level, resulting in a self-consistent change of profile of the wave functions. We find that the results differ significantly from those obtained in the pure 2DEG case (where no provision is made for a quantum motion in the transverse direction). Specifically, the critical value of interaction needed to attain the ferromagnetic (Stoner) instability is decreased and the Stoner criterion is therefore relaxed. This leads to an increased susceptibility and ultimately to a ferromagnetic transition deep in the high-density metallic regime. In the opposite limit of low carrier densities, a phenomenological treatment of the in-plane correlation effects suggests a ferromagnetic instability above the metal-insulator transition. Results are discussed in the context of the available experimental data.

  14. Coronal magnetic fields from the inversion of linear polarization measurements

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Lin, Haosheng; Kuhn, Jeff

    2010-02-01

    Real 3-D coronal magnetic field reconstruction is expected to be made based on the technologies of IR spectrometry and tomography, in which the data from other wavelengths can be used as critical reference. Our recent studies focused on this issue are briefly reviewed in this paper. Liu & Lin (2008) first evaluated the validity of potential field source surface model applied to one of five limb regions in the corona by comparing the theoretical polarization maps with SOLARC observations in the IR Fe XIII 10747 Å forbidden coronal emission line (CEL). The five limb coronal regions were then studied together in order to study the spatial relation between the bright EUV features on the solar disk and the inferred IR emission sources, which were obtained from the inversion of the SOLARC linear polarization (LP) measurements (Liu 2009). The inversion for each fiber data in the field of view was made by finding the best location where the difference between the synthesized and the observed polarizations reaches the minimum in the integration path along the line of sight. We found a close relationship between the inferred IR emission source locations and the EUV strong emission positions.

  15. Microscopic magnetic nature of K2NiF4-type 3d transition metal oxides

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Nozaki, H.; Umegaki, I.; Higemoto, W.; Ansaldo, E. J.; Brewer, J. H.; Sakurai, H.; Kao, T.-H.; Yang, H.-D.; Månsson, M.

    2014-12-01

    In order to elucidate the magnetic nature of K2NiF4-type 3d transition metal oxides, we have measured μ+SR spectra for Sr2VO4, LaSrVO4, and Sr2CrO4 using powder samples. ZF- and wTF-μ+SR measurements propose that Sr2VO4 enters into the static antiferromagnetic (AF) order phase below 8 K. In addition, TF-μ+SR measurements evidence that the transition at 105 K is not magnetic but structural and/or electronic in origin. For LaSrVO4, static long-range order has not been observed down to 20 K, while, as T decreases from 145 K, wTF asymmetry starts to decrease below 60 K, suggesting the appearance and evolution of localized magnetic moments below 60 K. For Sr2CrO4, by contrast, both ZF- and wTF-μ+SR have confirmed the presence of antiferromagnetic order below 117 K, as predicted in the χ(T) curve.

  16. 3D Equilibrium Reconstruction with Improved Magnetic Diagnostics on the Compact Toroidal Hybrid

    NASA Astrophysics Data System (ADS)

    Ma, Xinxing; Hanson, James D.; Hartwell, Gregory J.; Knowlton, Stephen F.; Maurer, David A.

    2013-10-01

    Equilibrium reconstructions using the three-dimensional V3FIT code [ 1 ] have been performed for low density (low β) current carrying plasmas on the Compact Toroidal Hybrid (CTH), a torsatron in which the magnetic configuration can be strongly modified by an ohmically-driven plasma current. These reconstructions use 50 external magnetic diagnostic measurements, including segmented and full Rogowski coils, saddle loops, poloidal and radial magnetic pickup coils. Time dependent 3D reconstructions document the evolution of the plasma cross section and current profile, with calculated value of βθ much less than the plasma internal inductance, li. Reconstructions typically show the plasma to move outward in major radius and become less elongated in poloidal cross section with increasing plasma current. In plasmas with low vacuum transform (ιvac ~ 0 . 04), the plasma current profile peaks with li above 0 . 84 when the total transform is 1 / 2 , which typically leads disruption. With values of ιvac >= 0 . 1 , li remains low (~ 0 . 7), and the discharges no longer disrupt. This work is supported by the USDoE under grant DE-FG02-00ER54610.

  17. Quiescence of magnetic braking and control of 3D non-resonance in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, J.-K.; in, Y.; Jeon, Y. M.; Logan, N. C.; Wang, Z. R.; Menard, J. E.; Kim, J. H.; Ko, W. H.; Kstar Team

    2016-10-01

    Magnetic braking using non-axisymmetric (3D) field is a promising tool to control rotation in tokamaks and thereby micro-to-macro instabilities. Ideally magnetic braking should induce only neoclassical momentum transport, without provoking resonant instabilities or unnecessary perturbations in particle or heat transport. Indeed in KSTAR, it was shown that the 3 rows of internal coils could be used to generate highly non-resonant n =1 with backward-helicity field distribution, called -90 phasing, and to change rotation without any perturbations to other transport channels. Recent KSTAR experiments, however, have also shown that the broad-wavelength field distribution, called 0 phasing, is rather more quiescent whereas -90 phasing can be highly degrading especially in high q95 plasmas. IPEC and NTV modeling are consistent with both observations, and further provide the optimal point in coil phasing and amplitude space. Additional experiments and comparisons with modeling all imply the sensitivity of plasma response to remnant resonant field, and thus importance of non-resonance control, to accomplish quiescent magnetic braking. This work was supported by DOE Contract DE-AC02-09CH11466.

  18. GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized Simulations

    NASA Astrophysics Data System (ADS)

    Wu, Benjamin; Tan, Jonathan C.; Nakamura, Fumitaka; Van Loo, Sven; Christie, Duncan; Collins, David

    2017-02-01

    We investigate giant molecular cloud collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of 3D, magnetohydrodynamics (MHD), adaptive mesh refinement simulations to study how cloud collisions trigger formation of dense filaments and clumps. Heating and cooling functions are implemented based on photo-dissociation region models that span the atomic-to-molecular transition and can return detailed diagnostic information. The clouds are initialized with supersonic turbulence and a range of magnetic field strengths and orientations. Collisions at various velocities and impact parameters are investigated. Comparing and contrasting colliding and non-colliding cases, we characterize morphologies of dense gas, magnetic field structure, cloud kinematic signatures, and cloud dynamics. We present key observational diagnostics of cloud collisions, especially: relative orientations between magnetic fields and density structures, like filaments; 13CO(J = 2-1), 13CO(J = 3-2), and 12CO(J = 8-7) integrated intensity maps and spectra; and cloud virial parameters. We compare these results to observed Galactic clouds.

  19. Denoising of 3D magnetic resonance images by using higher-order singular value decomposition.

    PubMed

    Zhang, Xinyuan; Xu, Zhongbiao; Jia, Nan; Yang, Wei; Feng, Qianjin; Chen, Wufan; Feng, Yanqiu

    2015-01-01

    The denoising of magnetic resonance (MR) images is important to improve the inspection quality and reliability of quantitative image analysis. Nonlocal filters by exploiting similarity and/or sparseness among patches or cubes achieve excellent performance in denoising MR images. Recently, higher-order singular value decomposition (HOSVD) has been demonstrated to be a simple and effective method for exploiting redundancy in the 3D stack of similar patches during denoising 2D natural image. This work aims to investigate the application and improvement of HOSVD to denoising MR volume data. The wiener-augmented HOSVD method achieves comparable performance to that of BM4D. For further improvement, we propose to augment the standard HOSVD stage by a second recursive stage, which is a repeated HOSVD filtering of the weighted summation of the residual and denoised image in the first stage. The appropriate weights have been investigated by experiments with different image types and noise levels. Experimental results over synthetic and real 3D MR data demonstrate that the proposed method outperforms current state-of-the-art denoising methods.

  20. Focused shape models for hip joint segmentation in 3D magnetic resonance images.

    PubMed

    Chandra, Shekhar S; Xia, Ying; Engstrom, Craig; Crozier, Stuart; Schwarz, Raphael; Fripp, Jurgen

    2014-04-01

    Deformable models incorporating shape priors have proved to be a successful approach in segmenting anatomical regions and specific structures in medical images. This paper introduces weighted shape priors for deformable models in the context of 3D magnetic resonance (MR) image segmentation of the bony elements of the human hip joint. The fully automated approach allows the focusing of the shape model energy to a priori selected anatomical structures or regions of clinical interest by preferentially ordering the shape representation (or eigen-modes) within this type of model to the highly weighted areas. This focused shape model improves accuracy of the shape constraints in those regions compared to standard approaches. The proposed method achieved femoral head and acetabular bone segmentation mean absolute surface distance errors of 0.55±0.18mm and 0.75±0.20mm respectively in 35 3D unilateral MR datasets from 25 subjects acquired at 3T with different limited field of views for individual bony components of the hip joint.

  1. Anatomical delineation of congenital heart disease using 3D magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Adams Bornemeier, Renee; Fellows, Kenneth E.; Fogel, Mark A.; Weinberg, Paul M.

    1994-05-01

    Anatomic delineation of the heart and great vessels is a necessity when managing children with congenital heart disease. Spatial orientation of the vessels and chambers in the heart and the heart itself may be quite abnormal. Though magnetic resonance imaging provides a noninvasive means for determining the anatomy, the intricate interrelationships between many structures are difficult to conceptualize from a 2-D format. Taking the 2-D images and using a volumetric analysis package allows for a 3-D replica of the heart to be created. This model can then be used to view the anatomy and spatial arrangement of the cardiac structures. This information may be utilized by the physicians to assist in the clinical management of these children.

  2. Internal structure and volcanic hazard potential of Mt Tongariro, New Zealand, from 3D gravity and magnetic models

    NASA Astrophysics Data System (ADS)

    Miller, Craig A.; Williams-Jones, Glyn

    2016-06-01

    A new 3D geophysical model of the Mt Tongariro Volcanic Massif (TgVM), New Zealand, provides a high resolution view of the volcano's internal structure and hydrothermal system, from which we derive implications for volcanic hazards. Geologically constrained 3D inversions of potential field data provides a greater level of insight into the volcanic structure than is possible from unconstrained models. A complex region of gravity highs and lows (± 6 mGal) is set within a broader, ~ 20 mGal gravity low. A magnetic high (1300 nT) is associated with Mt Ngauruhoe, while a substantial, thick, demagnetised area occurs to the north, coincident with a gravity low and interpreted as representing the hydrothermal system. The hydrothermal system is constrained to the west by major faults, interpreted as an impermeable barrier to fluid migration and extends to basement depth. These faults are considered low probability areas for future eruption sites, as there is little to indicate they have acted as magmatic pathways. Where the hydrothermal system coincides with steep topographic slopes, an increased likelihood of landslides is present and the newly delineated hydrothermal system maps the area most likely to have phreatic eruptions. Such eruptions, while small on a global scale, are important hazards at the TgVM as it is a popular hiking area with hundreds of visitors per day in close proximity to eruption sites. The model shows that the volume of volcanic material erupted over the lifespan of the TgVM is five to six times greater than previous estimates, suggesting a higher rate of magma supply, in line with global rates of andesite production. We suggest that our model of physical property distribution can be used to provide constraints for other models of dynamic geophysical processes occurring at the TgVM.

  3. 3D Characterization of the Magnetic Signature of a Medium Sized Impact Crater at Odessa, TX

    NASA Astrophysics Data System (ADS)

    Robinson, A.; Soule, D.; Everett, M.; Rodman, T.; Mangue Ndong, M.; Pereira, A.; Platt, P.; Trahan, A.

    2008-12-01

    Meteorite impacts are a common occurrence throughout Earth's geologic history. Many of the surface expressions of large ancient impacts have been subsequently erased by weathering and erosion processes. The study of preserved meteorite impacts is necessary to better understand this natural hazard which has been increasingly linked to rapid climate change and mass extinctions. The 60 ka Odessa meteorite crater located in Ector Co. Texas, is unique because it is not only well-preserved, but also has been the subject of extensive geologic examination. Geologic mapping and numeric models indicate that the crater was caused by a relatively small oblique impactor. The crater rim is remarkably well exposed. Much of the ejecta blanket is present, although deeply eroded. There has been considerable site disturbance due to drilling, shaft excavation, trenching, construction of a museum, trails, and the oil/gas activity in surrounding fields. Two previous geophysical investigations have shown that our data clearly corresponds to large-scale thrust deformation. With this in mind we have performed 3D high resolution magnetic gradiometer surveys that will allow us to quantify and characterize the magnetic signature of small to medium impacts. We will tie this data set to a 3D photorealistic outcrop image provided by laser scanning with coarser-scale, below-ground geophysical information. Our geophysical imagery provides a useful constraint on numerical simulations of the impact and its immediate regional-scale environmental effects. This information can be used to identify impact sites whose surface expression has been erased by natural erosional processes, allowing for improved frequency estimates and improved geo-hazard assessment.

  4. Synthesis, characterization, magnetic and electrochemical properties of a new 3D hexa-copper-substituted germanotungstate

    SciTech Connect

    Li, Yanzhou; Luo, Jie; Zhang, Yanting; Zhao, Junwei; Chen, Lijuan; Ma, Pengtao; Niu, Jingyang

    2013-09-15

    An inorganic–organic hybrid hexa-copper-substituted germanotungstate Na{sub 2}[Cu(dap){sub 2}]{sub 2}[Cu(dap){sub 2}] ([Cu{sub 6}(H{sub 2}O){sub 2}(dap){sub 2}][B-α-GeW{sub 9}O{sub 34}]{sub 2})·4H{sub 2}O (1) (dap=1,2-diaminopropane) has been hydrothermally prepared and characterized by elemental analyses, inductively coupled plasma atomic emission spectrometry (ICP–AES) analyses, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. 1 displays the six-connected 3D network with the long topological (O′Keefe) vertex symbol is 4·4·6{sub 4}·4·4·4·4·6{sub 4}·4·4·4·6{sub 4}·4·4·4 and the short vertex (Schläfli) symbol of 4{sup 12}6{sup 3}. Magnetic measurements indicate that there are the overall ferromagnetic exchange interactions in the belt-like hexa-Cu{sup II} cluster in 1. Furthermore, the electrochemical behavior and electrocatalysis of 1 modified carbon paste electrode (1-CPE) have been studied. The reductions of nitrite, bromate and hydrogen peroxide are principally mediated by the W{sup VI}-based wave. - Graphical abstract: A hexa-Cu{sup II} sandwiched germanotungstate has been synthesized and structurally characterized. The magnetic, solid-state electrochemical and electrocatalytic properties have been investigated. Display Omitted - Highlights: • Transition-metal substituted polyoxometalates. • Hexa-copper-substituted germanotungstate. • Six-connected 3D network. • Electrocatalytic reduction of nitrite, bromate and hydrogen peroxide.

  5. 3D gravity inversion and thermodynamic modelling reveal properties of shallow silicic magma reservoir beneath Laguna del Maule, Chile

    NASA Astrophysics Data System (ADS)

    Miller, Craig A.; Williams-Jones, Glyn; Fournier, Dominique; Witter, Jeff

    2017-02-01

    Active, large volume, silicic magma systems are potentially the most hazardous form of volcanism on Earth. Knowledge of the location, size, and physical properties of silicic magma reservoirs, is therefore important for providing context in which to accurately interpret monitoring data and make informed hazard assessments. Accordingly, we present the first geophysical image of the Laguna del Maule volcanic field magmatic system, using a novel 3D inversion of gravity data constrained by thermodynamic modelling. The joint analysis of gravity and thermodynamic data allows for a rich interpretation of the magma system, and highlights the importance of considering the full thermodynamic effects on melt density, when interpreting gravity models of active magmatic systems. We image a 30 km3, low density, volatile rich magma reservoir, at around 2 km depth, containing at least 85% melt, hosted within a broader 115 km3 body interpreted as wholly or partially crystallised (>70% crystal) cumulate mush. Our model suggests a magmatic system with shallow, crystal poor magma, overlying deeper, crystal rich magma. Even though a large density contrast (-600 kg/m3) with the surrounding crust exists, the lithostatic load is 50% greater than the magma buoyancy force, suggesting buoyancy alone is insufficient to trigger an eruption. The reservoir is adjacent to the inferred extension of the Troncoso fault and overlies the location of an intruding sill, driving present day deformation. The reservoir is in close proximity to the 2.0 km3 Nieblas (rln) eruption at 2-3 ka, which we calculate tapped approximately 7% of the magma reservoir. However, we suggest that the present day magma system is not large enough to have fed all post-glacial eruptions, and that the location, or size of the system may have migrated or varied over time, with each eruption tapping only a small aliquot of the available magma. The presence of a shallow reservoir of volatile rich, near liquidus magma, in close

  6. Deep electrical resistivity structure of the northwestern U.S. derived from 3-D inversion of USArray magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Meqbel, Naser M.; Egbert, Gary D.; Wannamaker, Philip E.; Kelbert, Anna; Schultz, Adam

    2014-09-01

    Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ˜70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Beneath the active extensional subprovinces in the south-central region, on average we see a resistive upper crust, and then extensive areas of low resistivity in the lower crust and uppermost mantle. Further below, much of the upper half of the upper mantle appears moderately resistive, then subsequently the lower upper mantle becomes moderately conductive. This column suggests a dynamic process of moderately hydrated and fertile deeper upper mantle upwelling during extension, intersection of that material with the damp solidus causing dehydration and melting, and upward exodus of generated mafic melts to pond and exsolve saline fluids near Moho levels. Lithosphere here is very thin. To the east and northeast, thick sections of resistive lithosphere are imaged under the Wyoming and Medicine Hat Cratons. These are punctuated with numerous electrically conductive sutures presumably containing graphitic or sulfide-bearing meta-sediments deeply underthrust and emplaced during ancient collisions. Below Cascadia, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Suspected oceanic lithosphere relicts in the central NW part of the model domain also are resistive, including the accreted “Siletzia” terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast “slab curtain” beneath

  7. The Donegal Sign Tree: A Local Legend Confirmed with Holographic Radar and 3-D Magnetics

    NASA Astrophysics Data System (ADS)

    Bechtel, T.; Cassidy, M.; Inagaki, M.; Windsor, C.; Capineri, L.; Falorni, P.; Bulleti, A.; Valentini, S.; Borgioli, G.; Ivashov, S.; Zhuravlev, A.; Razewig, V.; Vasiliev, I.; Bechtel, E.

    2009-05-01

    A tree at a crossroad in Historic Donegal, PA (founded 1722) bears unusual burls. Two are similar in size, and lie on opposite sides of the trunk at a height of six feet. Locals say that the tree engulfed an old road sign, and the geometry of the burls gives this appearance. However, the trunk between these two burls bears no welt where it sealed after swallowing the sign. In addition, there are other burls farther up the tree, which are not consistent with engulfed signs. Although the locals all know the legend of the swallowed sign, none ever actually saw the sign; not even an octogenarian who has lived at the crossroad his entire life, and recalls the tree as a child just as it is today. In order to test the veracity of the legend, this study performed subsurface imaging of the tree using holographic subsurface radar (Rascan), and 3-D measurements of the magnetic field about the tree using cesium vapor sensors. The Rascan system used is a continuous wave subsurface radar that operates at 5 discrete frequencies between 1.5 and 2.0 GHz. Reflections from subsurface objects are recorded as the phase difference pattern between an internal reference signal, and the reflected signal. Thus, it is a microwave analogy for optical holography. Rascan records reflections with two receiving antennae - parallel and perpendicular to the transmitter - so a single set of scans provides ten images; five frequencies at two polarizations. This ensures that an object at arbitrary depth will produce a strong phase difference in one of the images. As a consequence, elongate objects that are angled from the plane of scanning (e.g. a dipping sheet) produce "zebra stripes" of contrast values that vary cyclically with depth. The presence of stripes, and their relative positions in the different frequency images (the movement of which has been dubbed the "zebra shift") is useful for determining the relative depth of different portions of a dipping planar, or curved subsurface object. Rascan

  8. Polyethylenimine-interlayered core-shell-satellite 3D magnetic microspheres as versatile SERS substrates

    NASA Astrophysics Data System (ADS)

    Wang, Chongwen; Li, Ping; Wang, Junfeng; Rong, Zhen; Pang, Yuanfeng; Xu, Jiawen; Dong, Peitao; Xiao, Rui; Wang, Shengqi

    2015-11-01

    Precise fabrication of subtle nanogaps amid individual nanoparticles or between adjacent ones to obtain the highest SERS enhancement is still a challenge. Here, we reported a novel approach for fabricating core-shell-satellite 3D magnetic microspheres (CSSM), that easily form a porous 1.5 nm PEI interlayer to accommodate molecules and create sufficient hotspots between the inner Fe3O4@Ag core and outer assembled Au@Ag satellites. Experiments and finite-difference time-domain (FDTD) simulation demonstrated that the enhancement factor (EF) was about 2.03 × 108 and 6.25 × 106, respectively. In addition, the micro-scale magnetic core endowed the CSSM with a superior magnetic nature, which enabled easy separation and further enhanced Raman signals due to enrichment of targeted analytes and abundant interparticle hotspots created by magnetism-induced aggregation. Our results further demonstrated that the CSSM is expected to be a versatile SERS substrate, which has been verified by the detection of the adsorbed pesticide thiram and the non-adsorbed pesticide paraquat with a detection limit as low as 5 × 10-12 M and 1 × 10-10 M, respectively. The novel CSSM can overcome the long-standing limitations of SERS for the trace characterization of various analytes in different solutions and promises to transform SERS into a practical analytical technique.Precise fabrication of subtle nanogaps amid individual nanoparticles or between adjacent ones to obtain the highest SERS enhancement is still a challenge. Here, we reported a novel approach for fabricating core-shell-satellite 3D magnetic microspheres (CSSM), that easily form a porous 1.5 nm PEI interlayer to accommodate molecules and create sufficient hotspots between the inner Fe3O4@Ag core and outer assembled Au@Ag satellites. Experiments and finite-difference time-domain (FDTD) simulation demonstrated that the enhancement factor (EF) was about 2.03 × 108 and 6.25 × 106, respectively. In addition, the micro

  9. Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation

    NASA Astrophysics Data System (ADS)

    Bromberg, Omer; Tchekhovskoy, Alexander

    2016-02-01

    Relativistic jets are associated with extreme astrophysical phenomena, like the core collapse of massive stars in gamma-ray bursts (GRBs) and the accretion on to supermassive black holes in active galactic nuclei. It is generally accepted that these jets are powered electromagnetically, by the magnetized rotation of a central compact object (black hole or neutron star). However, how the jets produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven instabilities is the subject of active debate. We carry out time-dependent 3D relativistic magnetohydrodynamic (MHD) simulations of relativistic, Poynting-flux-dominated jets. The jets are launched self-consistently by the rotation of a strongly magnetized central object. This determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. We find that the jets are susceptible to two types of instability: (i) a global, external kink mode that grows on long time-scales. It bodily twists the jet, reducing its propagation velocity. We show analytically that in flat density profiles, like the ones associated with galactic cores, the external mode grows and may stall the jet. In the steep profiles of stellar envelopes the external kink weakens as the jet propagates outward. (ii) a local, internal kink mode that grows over short time-scales and causes small-angle magnetic reconnection and conversion of about half of the jet electromagnetic energy flux into heat. We suggest that internal kink instability is the main dissipation mechanism responsible for powering GRB prompt emission.

  10. A remark on the Beale-Kato-Majda criterion for the 3D MHD equations with zero magnetic diffusivity

    NASA Astrophysics Data System (ADS)

    Gala, Sadek; Ragusa, Maria Alessandra

    2016-06-01

    In this work, we show that a smooth solution of the 3D MHD equations with zero magnetic diffusivity in the whole space ℝ3 breaks down if and only if a certain norm of the magnetic field blows up at the same time.

  11. Ce 5d and Fe 3d magnetic profiles in CeH2/Fe multilayers probed by XRMS

    NASA Astrophysics Data System (ADS)

    Jaouen, N.; Tonnerre, J. M.; Raoux, D.; Ortega, L.; Bontempi, E.; Münzenberg, M.; Felsch, W.; Suzuki, M.; Maruyama, H.; Dürr, H. A.; Dudzik, E.; van der Laan, G.

    The element and electronic shell specificities of X-ray resonant magnetic scattering have been used to investigate the magnetization of Ce 5d and Fe 3d states in [CeH2(19.6 Å)/Fe(25.4 Å)]*38 a multilayer. We show that the measurement of the magnetic contribution to the intensities reflected at low angles at the Ce L2 and Fe L2,3 edges allows us to investigate the profile of the Ce 5d and Fe 3d magnetic polarization. The Fe 3d polarization is found to be uniform across the Fe layer and the Ce 5d polarization appears to be restricted close to the interface with Fe.

  12. Three-dimensional two-fluid investigation of 3D-localized magnetic reconnection and its relation to whistler waves

    NASA Astrophysics Data System (ADS)

    Yoon, Young Dae; Bellan, Paul M.

    2016-10-01

    A full three-dimensional computer code was developed in order to simulate a 3D-localized magnetic reconnection. We assume an incompressible two-fluid regime where the ions are stationary, and electron inertia and Hall effects are present. We solve a single dimensionless differential equation for perturbed magnetic fields with arbitrary background fields. The code has successfully reproduced both experimental and analytic solutions to resonance and Gendrin mode whistler waves in a uniform background field. The code was then modified to model 3D-localized magnetic reconnection as a 3D-localized perturbation on a hyperbolic-tangent background field. Three-dimensional properties that are asymmetric in the out-of-plane direction have been observed. These properties pertained to magnetic field lines, electron currents and their convection. Helicity and energy have also been examined, as well as the addition of a guide field.

  13. Accretion to magnetized stars through the Rayleigh-Taylor instability: global 3D simulations

    NASA Astrophysics Data System (ADS)

    Kulkarni, A. K.; Romanova, M. M.

    2008-05-01

    We present results of 3D simulations of magnetohydrodynamics (MHD) instabilities at the accretion disc-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It manifests itself in the form of tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner disc dynamical time-scale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, Θ <~ 30°, between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hotspots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermittent pulsations from accreting systems, as well as planet migration.

  14. Cation Exchange in Dynamic 3D Porous Magnets: Improvement of the Physical Properties.

    PubMed

    Grancha, Thais; Acosta, Alvaro; Cano, Joan; Ferrando-Soria, Jesús; Seoane, Beatriz; Gascon, Jorge; Pasán, Jorge; Armentano, Donatella; Pardo, Emilio

    2015-11-16

    We report two novel three-dimensional porous coordination polymers (PCPs) of formulas Li4{Mn4[Cu2(Me3mpba)2]3}·68H2O (2) and K4{Mn4[Cu2(Me3mpba)2]3}·69H2O (3) obtained-via alkali cation exchange in a single-crystal to single-crystal process-from the earlier reported anionic manganese(II)-copper(II) PCP of formula Na4{Mn4[Cu2(Me3mpba)2]3}·60H2O (1) [Me3mpba(4-) = N,N'-2,4,6-trimethyl-1,3-phenylenebis(oxamate)]. This postsynthetic process succeeds where the direct synthesis in solution from the corresponding building blocks fails and affords significantly more robust PCPs with enhanced magnetic properties [long-range 3D magnetic ordering temperatures for the dehydrated phases (1'-3') of 2.0 (1'), 12.0 (2'), and 20.0 K (3')]. Changes in the adsorptive properties upon postsynthetic exchange suggest that the nature, electrostatic properties, mobility, and location of the cations within the framework are crucial for the enhanced structural stability. Overall, these results further confirm the potential of postsynthetic methods (including cation exchange) to obtain PCPs with novel or enhanced physical properties while maintaining unaltered their open-framework structures.

  15. Local and Global 3-D Effects in the Magnetic Reconnection Experiment (MRX)

    NASA Astrophysics Data System (ADS)

    Dorfman, S.; Ji, H.; Yamada, M.; Oz, E.; Yoo, J.; Daughton, W.; Roytershteyn, V.

    2009-11-01

    One of the key open questions in Magnetic Reconnection is the nature of the mechanism that governs the reconnection rate in real astrophysical and laboratory systems. Comparisons between fully kinetic 2-D simulations of the Magnetic Reconnection Experiment (MRX) and experimental data show that the 2-D, collisionless expression for the electric field due to particle dynamics [1] does not match MRX data; related to this is a factor of 3-5 discrepancy in the layer width [2,3]. Adding collisions to the simulation leads to a broadening of the layer, but the level of collisionality present in MRX may not be high enough to resolve the discrepancy. Ongoing research on MRX explores the role of fluctuations and 3-D effects in the force balance. Significant toroidal asymmetries have been found, manifested by regions of high inductive electric field moving in the electron flow direction within the layer. Electromagnetic fluctuations in the lower hybrid frequency range [4] tend to occur in discharges with high local currents and a rapid local reconnection rate. The precise relation of these phenomena to fast reconnection is actively being investigated. [1] M. Hesse, et al., Phys. Plasmas, 6:1781 (1999). [2] Y. Ren, et al., Phys. Plasmas 15, 082113 (2008). [3] S. Dorfman, et al., Phys. Plasmas 15, 102107 (2008). [4] H. Ji, et al., Phys.Rev.Lett. 92 (2004) 115001. Supported by NDSEG, DOE, NASA, and NSF.

  16. The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

    NASA Astrophysics Data System (ADS)

    Campanyà, Joan; Ogaya, Xènia; Jones, Alan G.; Rath, Volker; Vozar, Jan; Meqbel, Naser

    2016-12-01

    As a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in 2-D and 3-D environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomalies surrounding the acquisition site. This behaviour complicates the characterization of the electrical resistivity distribution of the subsurface, particularly in complex areas. In this manuscript we assess the main advantages of complementing the standard MT impedance tensor (Z) data with interstation horizontal magnetic tensor (H) and geomagnetic transfer function (T) data in constraining the subsurface in a 3-D environment beneath a MT profile. Our analysis was performed using synthetic responses with added normally distributed and scattered random noise. The sensitivity of each type of data to different resistivity anomalies was evaluated, showing that the degree to which each site and each period is affected by the same anomaly depends on the type of data. A dimensionality analysis, using Z, H and T data, identified the presence of the 3-D anomalies close to the profile, suggesting a 3-D approach for recovering the electrical resistivity values of the subsurface. Finally, the capacity for recovering the geoelectrical structures of the subsurface was evaluated by performing joint inversion using different data combinations, quantifying the differences between the true synthetic model and the models from inversion process. Four main improvements were observed when performing joint inversion of Z, H and T data: (1) superior precision and accuracy at characterizing the electrical resistivity values of the anomalies below and outside the profile; (2) the potential to recover high electrical resistivity anomalies that are poorly recovered using Z data alone; (3) improvement in the characterization of the bottom and lateral boundaries of the anomalies with low

  17. Properties of the prominence magnetic field and plasma distributions as obtained from 3D whole-prominence fine structure modeling

    NASA Astrophysics Data System (ADS)

    Gunár, S.; Mackay, D. H.

    2016-07-01

    Aims: We analyze distributions of the magnetic field strength and prominence plasma (temperature, pressure, plasma β, and mass) using the 3D whole-prominence fine structure model. Methods: The model combines a 3D magnetic field configuration of an entire prominence, obtained from non-linear force-free field simulations, with a detailed semi-empirically derived description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Results: We show that in the modeled prominence, the variations of the magnetic field strength and its orientation are insignificant on scales comparable to the smallest dimensions of the observed prominence fine structures. We also show the ability of the 3D whole-prominence fine structure model to reveal the distribution of the prominence plasma with respect to its temperature within the prominence volume. This provides new insights into the composition of the prominence-corona transition region. We further demonstrate that the values of the plasma β are small throughout the majority of the modeled prominences when realistic photospheric magnetic flux distributions and prominence plasma parameters are assumed. While this is generally true, we also find that in the region with the deepest magnetic dips, the plasma β may increase towards unity. Finally, we show that the mass of the modeled prominence plasma is in good agreement with the mass of observed non-eruptive prominences.

  18. Electronic structure and local magnetism of 3d-5d impurity substituted CeFe2

    NASA Astrophysics Data System (ADS)

    Das, Rakesh; Das, G. P.; Srivastava, S. K.

    2016-04-01

    We present here a systematic first-principles study of electronic structure and local magnetic properties of Ce[Fe0.75M0.25]2 compounds, where M is a 3d, 4d or 5d transition or post-transition element, using the generalized gradient approximation of the density functional theory. The d-f band hybridizations existing in CeFe2 get modified by the impurity M in an orderly manner across a period for each impurity series: the hybridization is strongest for the Mn group impurity in the period and gets diminished on either side of it. The weakening of the d-f hybridization strength is also associated with a relative localization of the Ce 4f states with respect to the delocalized 4f states in CeFe2. The above effects are most prominent for 3d impurity series, while for 4d and 5d impurities, the hybridizations and relocalizations are relatively weak due primarily to the relatively extended nature of 4d and 5d wavefunctions. The Ce local moment is found to decrease from the CeFe2 value in proportion to the strength of relocalization, thus following almost the same orderly trend as obeyed by the d-f hybridization. Further, depending on the way the spin-up and spin-down densities of states of an impurity shift relative to the Fermi energy, the impurity local moments are highest for Mn or Fe group, reduce on either side, become zero for Ni to Ga, and are small but negative for V and Ti. The Ce hyperfine field is found to follow the M local moment in a linear fashion, and vice-versa.

  19. Magnetic field induced controllable self-assembly of maghemite nanocrystals: From 3D arrays to 1D nanochains

    NASA Astrophysics Data System (ADS)

    Tang, Yan; Chen, Qianwang; Chen, Rongsheng

    2015-08-01

    A hydrothermal process has been used to synthesize walnut-like maghemite superstructures which can be further self-assembled in a controllable manner into ordered three-dimensional (3D) architectures and one-dimensional (1D) nanochains in the presence of different external magnetic field. The assembly behavior of the maghemite nanoparticles isclosely related to the van der Waals interactions and external-field-induced magnetic dipole interactions. The magnetic properties of these nanostructures are also investigated.

  20. Deep electrical resistivity structure of the Northwestern U. S. derived from 3-D inversion of USArray Magnetotelluric data (Invited)

    NASA Astrophysics Data System (ADS)

    Meqbel, N. M.; Egbert, G. D.; Wannamaker, P. E.; Kelbert, A.; Schultz, A.

    2013-12-01

    Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ~70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Extensive areas of low resistivity are imaged in the lower crust and uppermost mantle beneath the extensional provinces, most plausibly explained by underplated, hybridized magmas and associated exsolved highly saline fluids. These pervasive low resistivities show aligned or 'streaky' textures roughly parallel to seismic fast-axes, possibly reflecting widespread flow induced alignment of melt in this area. Thick sections of resistive lithosphere imaged in the eastern and northeastern part of the domain coincide spatially with the Wyoming and Medicine Hat Cratons. Sutures bounding these cratonic blocks are electrically conductive most likely due to meta-sediments emplaced during ancient collisions. Below the Cascadia forearc, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Other resistive zones in the NW part of the domain may denote relict oceanic lithosphere: the accreted 'Siletzia' terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast 'slab curtain' beneath eastern Idaho interpreted by others as stranded Farallon lithosphere. Quasi-horizontal patches of low resistivity in the deep crust beneath the Cascade volcanic arc and fore-arc likely represent fluids evolved from breakdown of hydrous minerals in the down-going slab. In the backarc, low resistivities concentrate in

  1. Next-generation seismic experiments - II: wide-angle, multi-azimuth, 3-D, full-waveform inversion of sparse field data

    NASA Astrophysics Data System (ADS)

    Morgan, Joanna; Warner, Michael; Arnoux, Gillean; Hooft, Emilie; Toomey, Douglas; VanderBeek, Brandon; Wilcock, William

    2016-02-01

    3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2-4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI.

  2. Ising-like chain magnetism, Arrhenius magnetic relaxation, and case against 3D magnetic ordering in β-manganese phthalocyanine (C32H16MnN8)

    NASA Astrophysics Data System (ADS)

    Wang, Zhengjun; Seehra, Mohindar S.

    2016-04-01

    Previous magnetic studies in the organic semiconductor β-manganese phthalocyanine (β-MnPc) have reported it to be a canted ferromagnet below T C  ≈  8.6 K. However, the recent result of the lack of a λ-type anomaly in the specific heat versus temperature data near the quoted T C has questioned the presence of long-range 3-dimensional (3D) magnetic ordering in this system. In this paper, detailed measurements and analysis of the temperature (2 K-300 K) and magnetic field (up to 90 kOe) dependence of the dc and ac magnetic susceptibilities in a powder sample of β-MnPc leads us to conclude that 3D long-range magnetic ordering is absent in this material. This is supported by the Arrott plots and the lack of a peak in the ac susceptibilities, χ‧ and χ″, near the quoted T C. Instead, the system can be best described as an Ising-like chain magnet with Arrhenius relaxation of the magnetization governed by an intra-layer ferromagnetic exchange constant J/k B  =  2.6 K and the single ion anisotropy energy parameter |D|/k B  =  8.3 K. The absence of 3D long range order is consistent with the measured \\mid D\\mid   >  J.

  3. Three dimensional lithospheric magnetization structures beneath Australia derived by inverse modeling of CHAMP satellite magnetic field model

    NASA Astrophysics Data System (ADS)

    Du, Jinsong; Chen, Chao; Lesur, Vincent; Li, Yaoguo; Lane, Richard; Liang, Qing; Wang, Haoran

    2014-05-01

    We present an inversion algorithm for magnetic anomaly data in spherical coordinates to image the three dimensional (3-D) susceptibility distributions in the lithosphere. The method assumes that remanent magnetization is absent and that the magnetic anomalies are solely the result of lateral variations in magnetic susceptibility. To take into account the curvature of the Earth, the 3-D model is comprised of a set of spherical prisms (referred to as tesseroids), each of which has a constant isotropic susceptibility. The inversion method is formulated with a specifically designed model objective function and radial weighting function in spherical coordinates. A Tikhonov regularization technique is used to obtain an optimal solution with data misfit consistent with the estimated error level. Results for regional synthetic models with different magnetized inclinations and declinations are presented to demonstrate the capability of the method to recover large scale lithospheric magnetic structures. We have applied the algoithm to study the lithospheric susceptibility structures in the Australia region using magnetic anomaly data from the GRIMM_L120v0.0 model, which is based on ten years of CHAMP satellite data. As a self-constrained inversion, the maximum depths variation of magnetization layer is estimated first and then incorporated to the three dimensional (3-D) inversion. Results showed that the susceptibility anomalies concentrate in the depth range from 25 km to 45 km, i.e., focused in the lower crust. In addition, the results showed that the susceptibilities in continental lithosphere are higher than those in oceanic lithosphere. The inverted 3-D susceptibility distribution in the region of Australia reveals significant features related to tectonics, surface heat-flux, crustal thickness and Curie isotherm depths. In general, the higher susceptibility anomalies correlate with Precambrian rocks, and the lower susceptibility anomalies correlate with younger orogenic

  4. Effect of rosiglitazone on progression of atherosclerosis: insights using 3D carotid cardiovascular magnetic resonance

    PubMed Central

    Varghese, Anitha; Yee, Michael S; Chan, Cheuk F; Crowe, Lindsey A; Keenan, Niall G; Johnston, Desmond G; Pennell, Dudley J

    2009-01-01

    Background There is recent evidence suggesting that rosiglitazone increases death from cardiovascular causes. We investigated the direct effect of this drug on atheroma using 3D carotid cardiovascular magnetic resonance. Results A randomized, placebo-controlled, double-blind study was performed to evaluate the effect of rosiglitazone treatment on carotid atherosclerosis in subjects with type 2 diabetes and coexisting vascular disease or hypertension. The primary endpoint of the study was the change from baseline to 52 weeks of carotid arterial wall volume, reflecting plaque burden, as measured by carotid cardiovascular magnetic resonance. Rosiglitazone or placebo was allocated to 28 and 29 patients respectively. Patients were managed to have equivalent glycemic control over the study period, but in fact the rosiglitazone group lowered their HbA1c by 0.88% relative to placebo (P < 0.001). Most patients received a statin or fibrate as lipid control medication (rosiglitazone 78%, controls 83%). Data are presented as mean ± SD. At baseline, the carotid arterial wall volume in the placebo group was 1146 ± 550 mm3 and in the rosiglitazone group was 1354 ± 532 mm3. After 52 weeks, the respective volumes were 1134 ± 523 mm3 and 1348 ± 531 mm3. These changes (-12.1 mm3 and -5.7 mm3 in the placebo and rosiglitazone groups, respectively) were not statistically significant between groups (P = 0.57). Conclusion Treatment with rosiglitazone over 1 year had no effect on progression of carotid atheroma in patients with type 2 diabetes mellitus compared to placebo. PMID:19635160

  5. Joint 3D seismic travel time and full channel electrical resistivity inversion with cross gradient structure constraint

    NASA Astrophysics Data System (ADS)

    Gao, J.; Zhang, H.

    2015-12-01

    Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones

  6. 4D Magnetic Resonance Velocimetry in a 3D printed brain aneurysm

    NASA Astrophysics Data System (ADS)

    Amili, Omid; Schiavazzi, Daniele; Coletti, Filippo

    2016-11-01

    Cerebral aneurysms are of great clinical importance. It is believed that hemodynamics play a critical role in the development, growth, and rupture of brain arteries with such condition. The flow structure in the aneurysm sac is complex, unsteady, and three-dimensional. Therefore the time-resolved measurement of the three-dimensional three-component velocity field is crucial to predict the clinical outcome. In this study magnetic resonance velocimetry is used to assess the fluid dynamics inside a 3D printed model of a giant intracranial aneurysm. We reach sub-millimeter resolution while resolving sixteen instances within the cardiac cycle. The physiological flow waveform is imposed using an in-house built pump in a flow circuit where the cardiovascular impedance is matched. The flow evolution over time is reconstructed in detail. The complex flow structure is characterized by vortical and helical motions that reside in the aneurysm for most part of the cycle. The 4D pressured distribution is also reconstructed from the velocity field. The present case study was used in a previous CFD challenge, therefore these results may provide useful experimental comparison for simulations performed by other research groups.

  7. Connecting Global Measures of 3D Magnetic Reconnection to Local Kinetic Physics

    SciTech Connect

    Daughton, William Scott

    2015-07-16

    After giving the motivation for the work, slides present the topic under the following headings: Description of LAPD experiment; Actual simulation setup; Simple kinetic theory of ined-tied tearing; Diagnostics to characterizing 3D reconnection; Example #1 - short-tied system; and Example #2 - long line-tied system. Colorful simulations are shown for quasipotential vs field line exponentiation, field line integrated Ohms Law, and correlation with agyrotopy & energy conversion for example #1; and evolution of current density for largest case, field exponentiation vs quasi-potential, and time evolution of magnetic field lines for example #2. To satisfy line-tied boundary conditions, there is need for superposition of oblique modes--the simple two-mode approximation works surprisingly well. For force-free layers with bg >1, the fastest growing periodic modes are oblique with kxλ ~0.5. This implies a minimum length of Ly > 2πλbg. There are strong correlations between σ → Ξ → A0e (observable with spacecraft). Electron pressure tensor is the dominant non-ideal term.

  8. Craniosynostosis: prenatal diagnosis by 2D/3D ultrasound, magnetic resonance imaging and computed tomography.

    PubMed

    Helfer, Talita Micheletti; Peixoto, Alberto Borges; Tonni, Gabriele; Araujo Júnior, Edward

    2016-09-01

    Craniosynostosis is defined as the process of premature fusion of one or more of the cranial sutures. It is a common condition that occurs in about 1 to 2,000 live births. Craniosynostosis may be classified in primary or secondary. It is also classified as nonsyndromic or syndromic. According to suture commitment, craniosynostosis may affect a single suture or multiple sutures. There is a wide range of syndromes involving craniosynostosis and the most common are Apert, Pffeifer, Crouzon, Shaethre-Chotzen and Muenke syndromes. The underlying etiology of nonsyndromic craniosynostosis is unknown. Mutations in the fibroblast growth factor (FGF) signalling pathway play a crucial role in the etiology of craniosynostosis syndromes. Prenatal ultrasound`s detection rate of craniosynostosis is low. Nowadays, different methods can be applied for prenatal diagnosis of craniosynostosis, such as two-dimensional (2D) and three-dimensional (3D) ultrasound, magnetic resonance imaging (MRI), computed tomography (CT) scan and, finally, molecular diagnosis. The presence of craniosynostosis may affect the birthing process. Fetuses with craniosynostosis also have higher rates of perinatal complications. In order to avoid the risks of untreated craniosynostosis, children are usually treated surgically soon after postnatal diagnosis.

  9. Synthesis, characterization, magnetic and electrochemical properties of a new 3D hexa-copper-substituted germanotungstate

    NASA Astrophysics Data System (ADS)

    Li, Yanzhou; Luo, Jie; Zhang, Yanting; Zhao, Junwei; Chen, Lijuan; Ma, Pengtao; Niu, Jingyang

    2013-09-01

    An inorganic-organic hybrid hexa-copper-substituted germanotungstate Na2[Cu(dap)2]2[Cu(dap)2] {[Cu6(H2O)2(dap)2][B-α-GeW9O34]2}·4H2O (1) (dap=1,2-diaminopropane) has been hydrothermally prepared and characterized by elemental analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. 1 displays the six-connected 3D network with the long topological (O'Keefe) vertex symbol is 4·4·64·4·4·4·4·64·4·4·4·64·4·4·4 and the short vertex (Schläfli) symbol of 41263. Magnetic measurements indicate that there are the overall ferromagnetic exchange interactions in the belt-like hexa-CuII cluster in 1. Furthermore, the electrochemical behavior and electrocatalysis of 1 modified carbon paste electrode (1-CPE) have been studied. The reductions of nitrite, bromate and hydrogen peroxide are principally mediated by the WVI-based wave.

  10. A review of 3D first-pass, whole-heart, myocardial perfusion cardiovascular magnetic resonance.

    PubMed

    Fair, Merlin J; Gatehouse, Peter D; DiBella, Edward V R; Firmin, David N

    2015-08-01

    A comprehensive review is undertaken of the methods available for 3D whole-heart first-pass perfusion (FPP) and their application to date, with particular focus on possible acceleration techniques. Following a summary of the parameters typically desired of 3D FPP methods, the review explains the mechanisms of key acceleration techniques and their potential use in FPP for attaining 3D acquisitions. The mechanisms include rapid sequences, non-Cartesian k-space trajectories, reduced k-space acquisitions, parallel imaging reconstructions and compressed sensing. An attempt is made to explain, rather than simply state, the varying methods with the hope that it will give an appreciation of the different components making up a 3D FPP protocol. Basic estimates demonstrating the required total acceleration factors in typical 3D FPP cases are included, providing context for the extent that each acceleration method can contribute to the required imaging speed, as well as potential limitations in present 3D FPP literature. Although many 3D FPP methods are too early in development for the type of clinical trials required to show any clear benefit over current 2D FPP methods, the review includes the small but growing quantity of clinical research work already using 3D FPP, alongside the more technical work. Broader challenges concerning FPP such as quantitative analysis are not covered, but challenges with particular impact on 3D FPP methods, particularly with regards to motion effects, are discussed along with anticipated future work in the field.

  11. Synthesis and Application of Novel 3D Magnetic Chlorogenic Acid Imprinted Polymers Based on a Graphene-Carbon Nanotube Composite.

    PubMed

    Yan, Liang; Yin, Yuli; Lv, Piaopiao; Zhang, Zhaohui; Wang, Jing; Long, Fang

    2016-04-20

    A novel three-dimensional (3D) magnetic chlorogenic acid (CGA) imprinted polymer (MMIP) was prepared with novel carbon hybrid nanocomposite as the carrier, chlorogenic acid as the template molecule, and methacrylic acid as the functional monomer. The 3D MMIPs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, and UV spectrometry in detail. The results showed that the imprinted layer was attached successfully on the surface of a 3D magnetic carbon hybrid nanocomposite. The adsorption performance of the 3D MMIPs was investigated, and the results showed that the 3D MMIPs exhibited high adsorption capacity and fast adsorption rate toward CGA with a maximum adsorption capacity of 10.88 mg g(-1). The extraction conditions involving washing solvent, the pH of eluent solvent, elution volume, and desorption time were also investigated in detail. Combined with high-performance liquid chromatography, the 3D MMIPs have been applied to successfully extract CGA from Eucommia leaf extract samples.

  12. Advancement of 31P Magnetic Resonance Spectroscopy Using GRAPPA Reconstruction on a 3D Volume

    NASA Astrophysics Data System (ADS)

    Clevenger, Tony

    The overall objective of this research is to improve currently available metabolic imaging techniques for clinical use in monitoring and predicting treatment response to radiation therapy in liver cancer. Liver metabolism correlates with inflammatory and neoplastic liver diseases, which alter the intracellular concentration of phosphorus- 31 (31P) metabolites [1]. It is assumed that such metabolic changes occur prior to physical changes of the tissue. Therefore, information on regional changes of 31P metabolites in the liver, obtained by Magnetic Resonance Spectroscopic Imaging (MRSI) [1,2], can help in diagnosis and follow-up of various liver diseases. Specifically, there appears to be an immediate need of this technology for both the assessment of tumor response in patients with Hepatocellular Carcinoma (HCC) treated with Stereotactic Body Radiation Therapy (SBRT) [3--5], as well as assessment of radiation toxicity, which can result in worsening liver dysfunction [6]. Pilot data from our lab has shown that 31P MRSI has the potential to identify treatment response five months sooner than conventional methods [7], and to assess the biological response of liver tissue to radiation 24 hours post radiation therapy [8]. While this data is very promising, commonly occurring drawbacks for 31P MRSI are patient discomfort due to long scan times and prone positioning within the scanner, as well as reduced data quality due to patient motion and respiration. To further advance the full potential of 31P MRSI as a clinical diagnostic tool in the management of liver cancer, this PhD research project had the following aims: I) Reduce the long acquisition time of 3D 31P MRS by formulating and imple- menting an appropriate GRAPPA undersampling scheme and reconstruction on a clinical MRI scanner II) Testing and quantitative validation of GRAPPA reconstruction on 3D 31P MRSI on developmental phantoms and healthy volunteers At completion, this work should considerably advance 31P MRSI

  13. Breast Density Analysis with Automated Whole-Breast Ultrasound: Comparison with 3-D Magnetic Resonance Imaging.

    PubMed

    Chen, Jeon-Hor; Lee, Yan-Wei; Chan, Si-Wa; Yeh, Dah-Cherng; Chang, Ruey-Feng

    2016-05-01

    In this study, a semi-automatic breast segmentation method was proposed on the basis of the rib shadow to extract breast regions from 3-D automated whole-breast ultrasound (ABUS) images. The density results were correlated with breast density values acquired with 3-D magnetic resonance imaging (MRI). MRI images of 46 breasts were collected from 23 women without a history of breast disease. Each subject also underwent ABUS. We used Otsu's thresholding method on ABUS images to obtain local rib shadow information, which was combined with the global rib shadow information (extracted from all slice projections) and integrated with the anatomy's breast tissue structure to determine the chest wall line. The fuzzy C-means classifier was used to extract the fibroglandular tissues from the acquired images. Whole-breast volume (WBV) and breast percentage density (BPD) were calculated in both modalities. Linear regression was used to compute the correlation of density results between the two modalities. The consistency of density measurement was also analyzed on the basis of intra- and inter-operator variation. There was a high correlation of density results between MRI and ABUS (R(2) = 0.798 for WBV, R(2) = 0.825 for PBD). The mean WBV from ABUS images was slightly smaller than the mean WBV from MR images (MRI: 342.24 ± 128.08 cm(3), ABUS: 325.47 ± 136.16 cm(3), p < 0.05). In addition, the BPD calculated from MR images was smaller than the BPD from ABUS images (MRI: 24.71 ± 15.16%, ABUS: 28.90 ± 17.73%, p < 0.05). The intra-operator and inter-operator variant analysis results indicated that there was no statistically significant difference in breast density measurement variation between the two modalities. Our results revealed a high correlation in WBV and BPD between MRI and ABUS. Our study suggests that ABUS provides breast density information useful in the assessment of breast health.

  14. Design optimization of axial flow hydraulic turbine runner: Part I - an improved Q3D inverse method

    NASA Astrophysics Data System (ADS)

    Peng, Guoyi; Cao, Shuliang; Ishizuka, Masaru; Hayama, Shinji

    2002-06-01

    With the aim of constructing a comprehensive design optimization procedure of axial flow hydraulic turbine, an improved quasi-three-dimensional inverse method has been proposed from the viewpoint of system and a set of rotational flow governing equations as well as a blade geometry design equation has been derived. The computation domain is firstly taken from the inlet of guide vane to the far outlet of runner blade in the inverse method and flows in different regions are solved simultaneously. So the influence of wicket gate parameters on the runner blade design can be considered and the difficulty to define the flow condition at the runner blade inlet is surmounted. As a pre-computation of initial blade design on S2m surface is newly adopted, the iteration of S1 and S2m surfaces has been reduced greatly and the convergence of inverse computation has been improved. The present model has been applied to the inverse computation of a Kaplan turbine runner. Experimental results and the direct flow analysis have proved the validation of inverse computation. Numerical investigations show that a proper enlargement of guide vane distribution diameter is advantageous to improve the performance of axial hydraulic turbine runner. Copyright

  15. A 3D reconstruction algorithm for magneto-acoustic tomography with magnetic induction based on ultrasound transducer characteristics

    NASA Astrophysics Data System (ADS)

    Ma, Ren; Zhou, Xiaoqing; Zhang, Shunqi; Yin, Tao; Liu, Zhipeng

    2016-12-01

    In this study we present a three-dimensional (3D) reconstruction algorithm for magneto-acoustic tomography with magnetic induction (MAT-MI) based on the characteristics of the ultrasound transducer. The algorithm is investigated to solve the blur problem of the MAT-MI acoustic source image, which is caused by the ultrasound transducer and the scanning geometry. First, we established a transducer model matrix using measured data from the real transducer. With reference to the S-L model used in the computed tomography algorithm, a 3D phantom model of electrical conductivity is set up. Both sphere scanning and cylinder scanning geometries are adopted in the computer simulation. Then, using finite element analysis, the distribution of the eddy current and the acoustic source as well as the acoustic pressure can be obtained with the transducer model matrix. Next, using singular value decomposition, the inverse transducer model matrix together with the reconstruction algorithm are worked out. The acoustic source and the conductivity images are reconstructed using the proposed algorithm. Comparisons between an ideal point transducer and the realistic transducer are made to evaluate the algorithms. Finally, an experiment is performed using a graphite phantom. We found that images of the acoustic source reconstructed using the proposed algorithm are a better match than those using the previous one, the correlation coefficient of sphere scanning geometry is 98.49% and that of cylinder scanning geometry is 94.96%. Comparison between the ideal point transducer and the realistic transducer shows that the correlation coefficients are 90.2% in sphere scanning geometry and 86.35% in cylinder scanning geometry. The reconstruction of the graphite phantom experiment also shows a higher resolution using the proposed algorithm. We conclude that the proposed reconstruction algorithm, which considers the characteristics of the transducer, can obviously improve the resolution of the

  16. ORBXYZ: a 3D single-particle orbit code for following charged-particle trajectories in equilibrium magnetic fields

    SciTech Connect

    Anderson, D.V.; Cohen, R.H.; Ferguson, J.R.; Johnston, B.M.; Sharp, C.B.; Willmann, P.A.

    1981-06-30

    The single particle orbit code, TIBRO, has been modified extensively to improve the interpolation methods used and to allow use of vector potential fields in the simulation of charged particle orbits on a 3D domain. A 3D cubic B-spline algorithm is used to generate spline coefficients used in the interpolation. Smooth and accurate field representations are obtained. When vector potential fields are used, the 3D cubic spline interpolation formula analytically generates the magnetic field used to push the particles. This field has del.BETA = 0 to computer roundoff. When magnetic induction is used the interpolation allows del.BETA does not equal 0, which can lead to significant nonphysical results. Presently the code assumes quadrupole symmetry, but this is not an essential feature of the code and could be easily removed for other applications. Many details pertaining to this code are given on microfiche accompanying this report.

  17. ORBXYZ: A 3D single-particle orbit code for following charged particle trajectories in equilibrium magnetic fields

    NASA Astrophysics Data System (ADS)

    Anderson, D. V.; Cohen, R. H.; Ferguson, J. R.; Johnston, B. M.; Sharp, C. B.; Willmann, P. A.

    1981-06-01

    The single particle orbit code, TIBRO, was modified extensively to improve the interpolation methods used and to allow use of vector potential fields in the simulation of charged particle orbits on a 3D domain. A 3D cubic B-spline algorithm is used to generate spline coefficients used in the interpolation. Smooth and accurate field representations are obtained. When vector potential fields are used, the 3D cubic spline interpolation formula analytically generates the magnetic field used to push the particles. This field has del.BETA = 0 to computer roundoff. When magnetic induction is used the interpolation allows del.BETA does not equal 0, which can lead to significant nonphysical results. Presently the code assumes quadrupole symmetry, but this is not an essential feature of the code and could be easily removed for other applications.

  18. MO-F-CAMPUS-I-04: Magnetic Resonance Imaging of An in Vitro 3D Tumor Model

    SciTech Connect

    Veiga, C; Long, T; Siow, B; Loizidou, M; Royle, G; Ricketts, K

    2015-06-15

    Purpose: To investigate the use of an in vitro 3D tumor model (tumoroid) as a bio-phantom for repetitive and sequential magnetic resonance imaging (MRI) studies. Methods: The tissue engineered tumoroid comprised an artificial cancer mass (ACM) containing 30 million HT29 cancer cells seeded in a collagen type I matrix, whose density was increased by plastic compression (dry/wet weight=40%). The ACM was embedded in an uncompressed collagen gel that mimicked the tumor stroma, and the tumoroid was incubated for 24h before imaging. Images were acquired using the 1T ICON™ (Bruker Corporation, Billerica, MA) MRI scanner. T1 maps were calculated using an IR-RARE sequence (TE=12ms, TR=10000ms, 7 inversion times), while for T2 maps a MSME technique (TR=6000ms, 16 echoes) was used. T1 and T2 fittings were performed using a pixel-wise approach to produce relaxometric parametric maps. Results: The images acquired and corresponding T1 and T2 maps indicate contrast between the ACM and the stroma. T1 was 2500 and 2800ms, while T2 was 520 and 760ms, for the ACM and stroma respectively. The ACM construct was not homogenous and internal features were visible, which can be explained by local gradients of cell and/or collagen density. The viability of the cells was confirmed via confocal microscopy for several days after the imaging session, demonstrating the suitability of the tumoroid for sequential imaging studies. Conclusions: We have engineered a tumor model compatible with repetitive and sequential MRI. We found T1 and T2 contrast between the ACM and stroma using a pre-clinical MRI scanner. The model, which enables controllable cell and matrix densities, has potential for a wide range of applications in radiotherapy, such as to study tumor progression and to validate imaging biomarkers. Further work is necessary to understand the mechanisms behind the contrast achieved, and to correlate findings with biology and histology data.

  19. Depth-to-the-bottom optimization for magnetic data inversion: Magnetic structure of the Latium volcanic region, Italy

    NASA Astrophysics Data System (ADS)

    Caratori Tontini, F.; Cocchi, L.; Carmisciano, C.

    2006-11-01

    We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data to obtain 3-D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3-D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth-weighting function adapted from Li and Oldenburg (1996) to close the source toward the bottom. The main novelty of this method is a first-stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth-weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3-D source distribution.

  20. Comparison of publically available Moho depth and crustal thickness grids with newly derived grids by 3D gravity inversion for the High Arctic region.

    NASA Astrophysics Data System (ADS)

    Lebedeva-Ivanova, Nina; Gaina, Carmen; Minakov, Alexander; Kashubin, Sergey

    2016-04-01

    We derived Moho depth and crustal thickness for the High Arctic region by 3D forward and inverse gravity modelling method in the spectral domain (Minakov et al. 2012) using lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2013) was modified according to the most recently published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. The results are numerically compared with publically available grids of the Moho depth and crustal thickness for the High Arctic region (CRUST 1 and GEMMA global grids; the deep Arctic Ocean grids by Glebovsky et al., 2013) and seismic crustal scale profiles. The global grids provide coarser resolution of 0.5-1.0 geographic degrees and not focused on the High Arctic region. Our grids better capture all main features of the region and show smaller error in relation to the seismic crustal profiles compare to CRUST 1 and GEMMA grids. Results of 3D gravity modelling by Glebovsky et al. (2013) with separated geostructures approach show also good fit with seismic profiles; however these grids cover the deep part of the Arctic Ocean only. Alvey A, Gaina C, Kusznir NJ, Torsvik TH (2008). Integrated crustal thickness mapping and plate recon-structions for the high Arctic. Earth Planet Sci Lett 274:310-321. Gaina C, Werner SC, Saltus R, Maus S (2011). Circum-Arctic mapping project: new magnetic and gravity anomaly maps of the Arctic. Geol Soc Lond Mem 35, 39-48. Glebovsky V.Yu., Astafurova E.G., Chernykh A.A., Korneva M.A., Kaminsky V.D., Poselov V.A. (2013). Thickness of the Earth's crust in the

  1. The effect of particle size, morphology and C-rates on 3D structured Co3O4 inverse opal conversion mode anode materials

    NASA Astrophysics Data System (ADS)

    McNulty, David; Geaney, Hugh; Carroll, Elaine; Garvey, Shane; Lonergan, Alex; O’Dwyer, Colm

    2017-02-01

    Engineering Co3O4 nanoparticles into highly ordered, 3D inverse opal (IO) structures is shown to significantly improve their performance as more efficient conversion mode Li-ion anode materials. By comparison with Co3O4 microparticles, the advantages of the porous anode architecture are clearly shown. The inverse opal material markedly enhances specific capacity and capacity retention. The impact of various C rates on the rate of the initial charge demonstrates that higher rate charging (10 C) was much less destructive to the inverse opal structure than charging at a slow rate (0.1 C). Slower C rates that affect the IO structure resulted in higher specific capacities (more Li2O) as well as improved capacity retention. The IO structures cycle as CoO, which improves Coulombic efficiency and limits volumetric changes, allowing rate changes more efficiently. This work demonstrates how 3D IOs improve conversion mode anode material performance in the absence of additive or binders, thus enhancing mass transport of Li2O charge–discharge product through the open structure. This effect mitigates clogging by structural changes at slow rates (high capacity) and is beneficial to the overall electrochemical performance.

  2. A new approach for magnetic curves in 3D Riemannian manifolds

    SciTech Connect

    Bozkurt, Zehra Gök, Ismail Yaylı, Yusuf Ekmekci, F. Nejat

    2014-05-15

    A magnetic field is defined by the property that its divergence is zero in a three-dimensional oriented Riemannian manifold. Each magnetic field generates a magnetic flow whose trajectories are curves called as magnetic curves. In this paper, we give a new variational approach to study the magnetic flow associated with the Killing magnetic field in a three-dimensional oriented Riemann manifold, (M{sup 3}, g). And then, we investigate the trajectories of the magnetic fields called as N-magnetic and B-magnetic curves.

  3. 3D Electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Deca, J.; Lapenta, G.; Divin, A. V.; Lembege, B.; Markidis, S.

    2013-12-01

    Unlike the Earth and Mercury, our Moon has no global magnetic field and is therefore not shielded from the impinging solar wind by a magnetosphere. However, lunar magnetic field measurements made by the Apollo missions provided direct evidence that the Moon has regions of small-scale crustal magnetic fields, ranging up to a few 100km in scale size with surface magnetic field strengths up to hundreds of nanoTeslas. More recently, the Lunar Prospector spacecraft has provided high-resolution observations allowing to construct magnetic field maps of the entire Moon, confirming the earlier results from Apollo, but also showing that the lunar plasma environment is much richer than earlier believed. Typically the small-scale magnetic fields are non-dipolar and rather tiny compared to the lunar radius and mainly clustered on the far side of the moon. Using iPic3D we present the first 3D fully kinetic and electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies. We study the behaviour of a dipole model with variable surface magnetic field strength under changing solar wind conditions and confirm that lunar crustal magnetic fields may indeed be strong enough to stand off the solar wind and form a mini-magnetosphere, as suggested by MHD and hybrid simulations and spacecraft observations. 3D-PIC simulations reveal to be very helpful to analyze the diversion/braking of the particle flux and the characteristics of the resulting particles accumulation. The particle flux to the surface is significantly reduced at the magnetic anomaly, surrounded by a region of enhanced density due to the magnetic mirror effect. Second, the ability of iPic3D to resolve all plasma components (heavy ions, protons and electrons) allows to discuss in detail the electron physics leading to the highly non-adiabatic interactions expected as well as the implications for solar wind shielding of the lunar surface, depending on the scale size (solar wind protons

  4. Testing the Validity of the Neoclassical Toroidal Viscosity Model of Torque due to 3D Non-Resonant Magnetic Fields

    NASA Astrophysics Data System (ADS)

    McCubbin, A. J.; Smith, S. P.; Ferraro, N. M.; Callen, J. D.; Meneghini, O.

    2012-10-01

    Understanding the torque applied by resonant and non-resonant magnetic perturbations and its effect on rotation is essential to predict confinement and stability in burning plasmas. Non-axisymmetric 3D fields produced in the DIII-D tokamak apply a torque to the plasma, which can be evaluated through its effect on the plasma rotation. One explanation for this torque is Neoclassical Toroidal Viscosity (NTV) acting through non-resonant field components [1]. We have developed a software framework in which magnetic perturbations calculated by the state of the art two fluid MHD code M3D-C1 can be used in NTV calculations. For discharges with applied external magnetic fields in DIII-D, the experimentally determined torques will be analyzed and compared with NTV models.[4pt] [1] J.D. Callen, Nucl. Fusion 51, 094026 (2011).

  5. A supervisor for the successive 3D computations of magnetic, mechanical and acoustic quantities in power oil inductors and transformers

    SciTech Connect

    Reyne, G.; Magnin, H.; Berliat, G.; Clerc, C.

    1994-09-01

    A supervisor has been developed so as to allow successive 3D computations of different quantities by different softwares on the same physical problem. Noise of a given power oil transformer can be deduced from the surface vibrations of the tank. These vibrations are obtained through a mechanic computation whose Inputs are the electromagnetic forces provided . by an electromagnetic computation. Magnetic, mechanic and acoustic experimental data are compared with the results of the 3D computations. Stress Is put on the main characteristics of the supervisor such as the transfer of a given quantity from one mesh to the other.

  6. Joint inversion of 3-D seismic, gravimetric and magnetotelluric data for sub-basalt imaging in the Faroe-Shetland Basin

    NASA Astrophysics Data System (ADS)

    Heincke, B.; Moorkamp, M.; Jegen, M.; Hobbs, R. W.

    2012-12-01

    Imaging of sub-basalt sediments with reflection seismic techniques is limited due to absorption, scattering and transmission effects and the presence of peg-leg multiples. Although many of the difficulties facing conventional seismic profiles can be overcome by recording long offset data resolution of sub-basalt sediments in seismic sections is typically still largely restricted. Therefore multi-parametric approaches in general and joint inversion strategies in particular (e.g. Colombo et al., 2008, Jordan et al., 2012) are considered as alternative to gain additional information from sub-basalt structures. Here, we combine in a 3-D joint inversion first-arrival time tomography, FTG gravity and MT data to identify the base basalt and resolve potential sediments underneath. For sub-basalt exploration the three methods complement each other such that the null space is reduced and significantly better resolved models can be obtained than would be possible by the individual methods: The seismic data gives a robust model for the supra-basalt sediments whilst the gravity field is dominated by the high density basalt and basement features. The MT on the other hand is sensitive to the conductivity in both the supra- and sub-basalt sediments. We will present preliminary individual and joint inversion result for a FTG, seismic and MT data set located in the Faroe-Shetland basin. Because the investigated area is rather large (~75 x 40 km) and the individual data sets are relatively huge, we use a joint inversion framework (see Moorkamp et al., 2011) which is designed to handle large amount of data/model parameters. This program has moreover the options to link the individual parameter models either petrophysically using fixed parameter relationships or structurally using the cross-gradient approach. The seismic data set consists of a pattern of 8 intersecting wide-angle seismic profiles with maximum offsets of up to ~24 km. The 3-D gravity data set (size :~ 30 x 30 km) is

  7. Inverse Planning Approach for 3-D MRI-Based Pulse-Dose Rate Intracavitary Brachytherapy in Cervix Cancer

    SciTech Connect

    Chajon, Enrique; Dumas, Isabelle; Touleimat, Mahmoud B.Sc.; Magne, Nicolas; Coulot, Jeremy; Verstraet, Rodolfe; Lefkopoulos, Dimitri; Haie-Meder, Christine

    2007-11-01

    Purpose: The purpose of this study was to evaluate the inverse planning simulated annealing (IPSA) software for the optimization of dose distribution in patients with cervix carcinoma treated with MRI-based pulsed-dose rate intracavitary brachytherapy. Methods and Materials: Thirty patients treated with a technique using a customized vaginal mold were selected. Dose-volume parameters obtained using the IPSA method were compared with the classic manual optimization method (MOM). Target volumes and organs at risk were delineated according to the Gynecological Brachytherapy Group/European Society for Therapeutic Radiology and Oncology recommendations. Because the pulsed dose rate program was based on clinical experience with low dose rate, dwell time values were required to be as homogeneous as possible. To achieve this goal, different modifications of the IPSA program were applied. Results: The first dose distribution calculated by the IPSA algorithm proposed a heterogeneous distribution of dwell time positions. The mean D90, D100, and V100 calculated with both methods did not differ significantly when the constraints were applied. For the bladder, doses calculated at the ICRU reference point derived from the MOM differed significantly from the doses calculated by the IPSA method (mean, 58.4 vs. 55 Gy respectively; p = 0.0001). For the rectum, the doses calculated at the ICRU reference point were also significantly lower with the IPSA method. Conclusions: The inverse planning method provided fast and automatic solutions for the optimization of dose distribution. However, the straightforward use of IPSA generated significant heterogeneity in dwell time values. Caution is therefore recommended in the use of inverse optimization tools with clinical relevance study of new dosimetric rules.

  8. Solid-liquid phase transitions in 3D systems with the inverse-power and Yukawa potentials

    NASA Astrophysics Data System (ADS)

    Vaulina, O. S.; Koss, X. G.

    2016-03-01

    The melting of face-centered cubic (fcc) and body-centered cubic (bcc) crystal lattices was studied analytically and numerically for the systems of particles interacting via the inverse-power-law and Yukawa potentials. New approach is proposed for determination of the solid-liquid phase transitions in these systems. The suggested approach takes into account a nonlinearity (anharmonicity) of pair interaction forces and allows to correctly predict the conditions of melting of the systems with various isotropic pair interaction potentials. The obtained results are compared with the existing theoretical and numerical data.

  9. Inversion of Chelyabinsk Meteorite Micromagnetic Maps - Implication for Inversions of Mars Magnetic Maps

    NASA Astrophysics Data System (ADS)

    Mazanec, M.; Kletetschka, G.

    2014-12-01

    The largest fragment of Chelyabinsk meteorite fell into the Russian lake Chebarkul on February 15, 2013. We used magnetic scanner constructed by Youngwood Science and Engineering (YSE, see Kletetschka et al 2013) to obtain micromagnetic maps of one of the Chelyabinsk's meteorite fragment. Our instrument has a Hall effect magnetic sensor and maps vertical component of the magnetic field approximately 0.3 mm above the planar surface of meteorite sample. Advantage of this instrument is a constant background field due to static position of the sensor. We applied fast Fourier transform inversion technique developed by Lima et al (2013). This technique is tailored for scanning magnetic microscopy (SMM), but may be also modified for aeromagnetic or satellite survey. It retrieves planar unidirectional magnetization distribution from micromagnetic field map. With this technique we achieved verifiable information about the source of the magnetic anomalies in our meteorite sample. Specific areas of detected magnetization were used for compositional analyses by scanning electron microscopy (SEM). This way we obtain the ground truth for the source of magnetic anomalies of our meteorite thin section. Measurement of chemical composition of magnetic grains can be directly linked to the amount of magnetization for the specific magnetic mineralogy. The inversion technique was extended for interpretation of real magnetic anomalies on Mars. Lima, E. A., B. P. Weiss, L. Baratchart,D. P.Hardin, and E. B. Saff (2013), Fast inversion ofmagnetic field maps of unidirectional planar geological magnetization, J. Geophys. Res. Solid Earth, 118, 2723-2752, doi:10.1002/jgrb.50229.Kletetschka, G., Schnabl, P., Sifnerova, K., Tasaryova, Z., Manda, S., and Pruner, P., 2013, Magnetic scanning and interpretation of paleomagnetic data from Prague Synform's volcanics: Studia Geophysica Et Geodaetica, v. 57, no. 1, p. 103-117.

  10. 3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

    PubMed

    O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

    2013-08-01

    Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

  11. A method of inversion of satellite magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.

    1977-01-01

    A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier Series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.

  12. Inductively Driven, 3D Liner Compression of a Magnetized Plasma to Megabar Energy Densities

    SciTech Connect

    Slough, John

    2015-02-01

    modules. The additional energy and switching capability proposed will thus provide for optimal utilization of the liner energy. The following tasks were outlined for the three year effort: (1) Design and assemble the foil liner compression test structure and chamber including the compression bank and test foils [Year 1]. (2) Perform foil liner compression experiments and obtain performance data over a range on liner dimensions and bank parameters [Year 2]. (3) Carry out compression experiments of the FRC plasma to Megagauss fields and measure key fusion parameters [Year 3]. (4) Develop numerical codes and analyze experimental results, and determine the physics and scaling for future work [Year 1-3]. The principle task of the project was to design and assemble the foil liner FRC formation chamber, the full compression test structure and chamber including the compression bank. This task was completed successfully. The second task was to test foils in the test facility constructed in year one and characterize the performance obtained from liner compression. These experimental measurements were then compared with analytical predictions, and numerical code results. The liner testing was completed and compared with both the analytical results as well as the code work performed with the 3D structural dynamics package of ANSYS Metaphysics®. This code is capable of modeling the dynamic behavior of materials well into the non-linear regime (e.g. a bullet hit plate glass). The liner dynamic behavior was found to be remarkably close to that predicted by the 3D structural dynamics results. Incorporating a code that can also include the magnetics and plasma physics has also made significant progress at the UW. The remaining test bed construction and assembly task is was completed, and the FRC formation and merging experiments were carried out as planned. The liner compression of the FRC to Megagauss fields was not performed due to not obtaining a sufficiently long lived FRC during the

  13. Microfluidic Fabrication of Bio-Inspired Microfibers with Controllable Magnetic Spindle-Knots for 3D Assembly and Water Collection.

    PubMed

    He, Xiao-Heng; Wang, Wei; Liu, Ying-Mei; Jiang, Ming-Yue; Wu, Fang; Deng, Ke; Liu, Zhuang; Ju, Xiao-Jie; Xie, Rui; Chu, Liang-Yin

    2015-08-12

    A simple and flexible approach is developed for controllable fabrication of spider-silk-like microfibers with tunable magnetic spindle-knots from biocompatible calcium alginate for controlled 3D assembly and water collection. Liquid jet templates with volatile oil drops containing magnetic Fe3O4 nanoparticles are generated from microfluidics for fabricating spider-silk-like microfibers. The structure of jet templates can be precisely adjusted by simply changing the flow rates to tailor the structures of the resultant spider-silk-like microfibers. The microfibers can be well manipulated by external magnetic fields for controllably moving, and patterning and assembling into different 2D and 3D structures. Moreover, the dehydrated spider-silk-like microfibers, with magnetic spindle-knots for collecting water drops, can be controllably assembled into spider-web-like structures for excellent water collection. These spider-silk-like microfibers are promising as functional building blocks for engineering complex 3D scaffolds for water collection, cell culture, and tissue engineering.

  14. Towards 3D multi-scale teleseismic and gravity data inversion using hybrid DSM/SPECFEM technique : application to the Pyrenees

    NASA Astrophysics Data System (ADS)

    Martin, Roland; Monteiller, Vadim; Chevrot, Sébastien; Wang, Yi; Komatitsch, Dimitri; Dufréchou, Grégory

    2015-04-01

    We describe here a method of inversion applied to seismic data sets constrained by gravity data at the regional scale. This will allow us to obtain robust models of P and S wave velocities but also of density, providing key constraints on the composition and thermal state of the lithosphere. Our approach relies on teleseimic waves, which illuminate the medium from below. We have developped a hybrid method in which a wave propagation method at the global scale (DSM/Direct solution method) is coupled with a spectral element method at the regional scale (Monteiller et al. 2013). With the spectral element method, we are able to model the 3D wave propagation effects in a computational domain of 400km long x 400km wide and 200 km deep, for an incident teleseismic wavefront introduced at the boundaries of this domain with periods as short as 2 s. The DSM global method allows to compute this incident field for a spherical Earth model. We use a multi-scale joint inversion of both gravity and seismic waveform data, accounting for the long wavelengths of the gravity field taken from a global model. In terms of inversion technique, we have validated an adjoint method for the inversion of seismic waveforms. An optimized BFGS inversion technique is used to minimize the difference between observed and computed full waveforms. The gradient of the misfit function gives the direction over which the model must be perturbed to minimize this difference. At each step of the inversion procedure we choose an optimal step length that accelerates the minimization. This is the crucial ingredient that allows us to build an efficient iterative full waveform inversion. We have extended this method by incorporating gravity data provided by the BGI/Bureau Gravimétrique International into the inversion. If the waveforms allow us to constrain the seismic velocities, they are less sensitive to the structure in density, which gives independent and crucial information to constrain the nature of rocks

  15. Imaging the Roots of Geothermal Systems: 3-D Inversion of Magnetotelluric Array Data in the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Bertrand, E. A.; Caldwell, G.; Bannister, S. C.; Hill, G.; Bennie, S.

    2013-12-01

    The Taupo Volcanic Zone (TVZ), located in the central North Island of New Zealand, is a rifted arc that contains more than 20 liquid-dominated high-temperature geothermal systems, which together discharge ~4.2 GW of heat at the surface. The shallow (upper ~500 m) extent of these geothermal systems is marked by low-resistivity, mapped by tens-of-thousands of DC resistivity measurements collected throughout the 1970's and 80's. Conceptual models of heat transport through the brittle crust of the TVZ link these low-resistivity anomalies to the tops of vertically ascending plumes of convecting hydrothermal fluid. Recently, data from a 40-site array of broadband seismometers with ~4 km station spacing, and an array of 270 broadband magnetotelluric (MT) measurements with ~2 km station spacing, have been collected in the south-eastern part of the TVZ in an experiment to image the deep structure (or roots) of the geothermal systems in this region. Unlike DC resistivity, these MT measurements are capable of resolving the resistivity structure of the Earth to depths of 10 km or more. 2-D and 3-D models of subsets of these MT data have been used to provide the first-ever images of quasi-vertical low-resistivity zones (at depths of 3-7 km) that connect with the near-surface geothermal fields. These low-resistivity zones are interpreted to represent convection plumes of high-temperature fluids ascending within fractures, which supply heat to the overlying geothermal fields. At the Rotokawa, Ngatamariki and Ohaaki geothermal fields, these plumes extend to a broad layer of low-resistivity, inferred to represent a magmatic, basal heat source located below the seismogenic zone (at ~7-8 km depth) that drives convection in the brittle crust above. Little is known about the mechanisms that transfer heat into the hydrothermal regime. However, at Rotokawa, new 3-D resistivity models image a vertical low-resistivity zone that lies directly beneath the geothermal field. The top of this

  16. TU-F-BRF-04: Registration of 3D Transesophageal Echocardiography and X-Ray Fluoroscopy Using An Inverse Geometry X-Ray System

    SciTech Connect

    Speidel, M; Hatt, C; Tomkowiak, M; Raval, A; Funk, T

    2014-06-15

    Purpose: To develop a method for the fusion of 3D echocardiography and Scanning-Beam Digital X-ray (SBDX) fluoroscopy to assist with catheter device and soft tissue visualization during interventional procedures. Methods: SBDX is a technology for low-dose inverse geometry x-ray fluoroscopy that performs digital tomosynthesis at multiple planes in real time. In this study, transesophageal echocardiography (TEE) images were fused with SBDX images by estimating the 3D position and orientation (the “pose”) of the TEE probe within the x-ray coordinate system and then spatially transforming the TEE image data to match this pose. An initial pose estimate was obtained through tomosynthesis-based 3D localization of points along the probe perimeter. Position and angle estimates were then iteratively refined by comparing simulated projections of a 3D probe model against SBDX x-ray images. Algorithm performance was quantified by imaging a TEE probe in different known orientations and locations within the x-ray field (0-30 degree tilt angle, up to 50 mm translation). Fused 3D TEE/SBDX imaging was demonstrated by imaging a tissue-mimicking polyvinyl alcohol cylindrical cavity as a catheter was navigated along the cavity axis. Results: Detected changes in probe tilt angle agreed with the known changes to within 1.2 degrees. For a 50 mm translation along the source-detector axis, the detected translation was 50.3 mm. Errors for in-plane translations ranged from 0.1 to 0.9 mm. In a fused 3D TEE/SBDX display, the catheter device was well visualized and coincident with the device shadow in the TEE images. The TEE images portrayed phantom boundaries that were not evident under x-ray. Conclusion: Registration of soft tissue anatomy derived from TEE imaging and device imaging from SBDX x-ray fluoroscopy is feasible. The simultaneous 3D visualization of these two modalities may be useful in interventional procedures involving the navigation of devices to soft tissue anatomy.

  17. 3D-FIESTA Magnetic Resonance Angiography Fusion Imaging of Distal Segment of Occluded Middle Cerebral Artery.

    PubMed

    Kuribara, Tomoyoshi; Haraguchi, Koichi; Ogane, Kazumi; Matsuura, Nobuki; Ito, Takeo

    2015-01-01

    Middle cerebral artery (MCA) occlusion was examined with basi-parallel anatomical scanning (BPAS) using three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA), and 3D-FIESTA and magnetic resonance angiography (MRA) fusion images were created. We expected that an incidence of hemorrhagic complications due to vessel perforations would be decreased by obtaining vascular information beyond the occlusion and thus acute endovascular revascularization could be performed using such techniques. We performed revascularization for acute MCA occlusion for five patients who were admitted in our hospital from October 2012 to October 2014. Patients consisted of 1 man and 4 women with a mean age of 76.2 years (range: 59-86 years). Fusion images were created from three-dimensional time of flight (3D-TOF) MRA and 3D-FIESTA with phase cycling (3D-FIESTA-C). Then thrombectomy was performed in all the 5 patients. Merci retriever to 1 patient, Penumbra system to 1, urokinase infusion to 2, and Solitaire to 1 using such techniques. In all cases, a 3D-FIESTA-MRA fusion imaging could depict approximately clear vascular information to at least the M3 segment beyond the occlusion. And each acute revascularization was able to perform smoothly using these imaging techniques. In all cases, there was no symptomatic hemorrhagic complication. It showed that 3D-FIESTA MRA fusion imaging technique could obtain vascular information beyond the MCA occlusion. In this study, no symptomatic hemorrhagic complications were detected. It could imply that such techniques were useful not only to improve treatment efficiency but also to reduce the risk of development of hemorrhagic complications caused by vessel perforations in acute revascularization.

  18. Defect energetics and magnetic properties of 3 d-transition-metal-doped topological crystalline insulator SnTe

    NASA Astrophysics Data System (ADS)

    Wang, Na; Wang, JianFeng; Si, Chen; Gu, Bing-Lin; Duan, WenHui

    2016-08-01

    The introduction of magnetism in SnTe-class topological crystalline insulators is a challenging subject with great importance in the quantum device applications. Based on the first-principles calculations, we have studied the defect energetics and magnetic properties of 3 d transition-metal (TM)-doped SnTe. We find that the doped TM atoms prefer to stay in the neutral states and have comparatively high formation energies, suggesting that the uniform TMdoping in SnTe with a higher concentration will be difficult unless clustering. In the dilute doping regime, all the magnetic TMatoms are in the high-spin states, indicating that the spin splitting energy of 3 d TM is stronger than the crystal splitting energy of the SnTe ligand. Importantly, Mn-doped SnTe has relatively low defect formation energy, largest local magnetic moment, and no defect levels in the bulk gap, suggesting that Mn is a promising magnetic dopant to realize the magnetic order for the theoretically-proposed large-Chern-number quantum anomalous Hall effect (QAHE) in SnTe.

  19. 2-D and 3-D Magnetic Inversion Studies in the South Atlantic

    DTIC Science & Technology

    1988-01-01

    expression may be muted . SPREADING CENTER 1. Introduction Fig. 1. Nomenclature used at a ridge-transform intersection. At fast spreading ridges the axial...1979 Swan E 17 40 N 10 1.6 0.18 1.5 >600 >40 CAYTROUGH. 1979 Eastern Pacific: Blanco W 44 30 N 29 0.2 -0.3 340 11.7 Crane et al.. 1985 Tamayo E 23 00 N...subsidence (Kane E, Kane W, Meteor E. Meteor the magnitude of asymmetry and offset age, as W, Oriente, and Swan do; Cox E does not). At short shown by

  20. 3-D MHD modeling and stability analysis of jet and spheromak plasmas launched into a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick

    2016-10-01

    The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.

  1. Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin, NW Iberian Peninsula: 3D structural model and kinematic evolution

    NASA Astrophysics Data System (ADS)

    Uzkeda, Hodei; Bulnes, Mayte; Poblet, Josep; García-Ramos, José Carlos; Piñuela, Laura

    2016-09-01

    We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.

  2. Inverse magnetic catalysis in the linear sigma model

    NASA Astrophysics Data System (ADS)

    Ayala, A.; Loewe, M.; Zamora, R.

    2016-05-01

    We compute the critical temperature for the chiral transition in the background of a magnetic field in the linear sigma model, including the quark contribution and the thermo-magnetic effects induced on the coupling constants at one loop level. For the analysis, we go beyond mean field aproximation, by taking one loop thermo-magnetic corrections to the couplings as well as plasma screening effects for the boson's masses, expressed through the ring diagrams. We found inverse magnetic catalysis, i.e. a decreasing of the critical chiral temperature as function of the intensity of the magnetic field, which seems to be in agreement with recent results from the lattice community.

  3. Regional conductivity structures of the northwestern segment of the North American Plate derived from 3-D inversion of USArray magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Meqbel, N. M.; Egbert, G. D.; Kelbert, A.

    2010-12-01

    Long period (10-20,000 s) magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental United States through EMScope, a component of EarthScope, a multidisciplinary decade-long project to study the structure and evolution of the North American Continent. MT deployments in 2006-2010 have so far acquired data at 237 sites on an approximately regular grid, with the same nominal spacing as the USArray broadband seismic transportable array (~70 km), covering the Northwestern US, from the Oregon-Washington coast across the Rocky Mountains, into Montana and Wyoming. Preliminary 3-D inversion results (Patro and Egbert; 2008), based on data from the 110 westernmost “Cascadia” sites collected in the first two years, revealed extensive areas of high conductivity in the lower crust beneath the Northwest Basin and Range (NBR), inferred to result from fluids (including possibly partial melt at depth) associated with magmatic underplating, and beneath the Cascade Mountains, probably due to fluids released by the subducting Juan de Fuca slab. Here we extend this study, refining and further testing the preliminary results from Cascadia, and extending the inversion domain to the East, to include all of the EarthScope data. Although site spacing is very broad, distinct regional structures are clearly evident even in simple maps of apparent resistivity, phase and induction vectors. For the 3-D inversion we are using the parallelized version of our recently developed Modular Code (ModEM), which supports Non-Linear Conjugate Gradient and several Gauss-Newton type schemes. Our initial 3-D inversion results using 212 MT sites, fitting impedances and vertical field transfer functions (together and separately) suggest several conductive and resistive structures which appear to be stable and required by the measured data. These include: - A conductive structure elongated in the N-S direction underneath the volcanic arc of the Cascadia

  4. Effect of magnetism on the solubility of 3 d elements in BCC iron: Results of first-principle investigations

    NASA Astrophysics Data System (ADS)

    Gorbatov, O. I.; Okatov, S. V.; Gornostyrev, Yu. N.; Korzhavyi, P. A.; Ruban, A. V.

    2013-08-01

    The methods of quantum-mechanical simulation have been used to study alloys of bcc iron with 3 d transition metals in the ferromagnetic and paramagnetic states. It has been shown that the main factor that determines the solubility of the 3 d elements is their electronic structure. The energy of the solution, mixing, and effective interatomic interactions vary regularly depending on the position of the element in the Periodic Table and on the magnetic state of the matrix. In some cases, depending on the magnetic state, changes in these quantities lead to the violation of the Hume-Rothery rules that determine the solubility of substitutional elements in alloys. The results obtained help us to understand the microscopic mechanisms that determine the solubility of alloying elements and their effect on the phase stability and structural state of steels.

  5. First MMS Observations of High Time Resolution 3D Electric and Magnetic fields at the Dayside Magnetopause.

    NASA Astrophysics Data System (ADS)

    Torbert, R. B.; Burch, J. L.; Russell, C. T.; Magnes, W.; Ergun, R. E.; Lindqvist, P. A.; Le Contel, O.; Vaith, H.; Macri, J.; Myers, S.; Rau, D.; Needell, J.; King, B.; Granoff, M.; Chutter, M.; Dors, I.; Argall, M. R.; Shuster, J. R.; Olsson, G.; Marklund, G. T.; Khotyaintsev, Y. V.; Eriksson, A. I.; Kletzing, C.; Bounds, S. R.; Anderson, B. J.; Baumjohann, W.; Steller, M.; Bromund, K. R.; Le, G.; Nakamura, R.; Strangeway, R. J.; Leinweber, H. K.; Tucker, S.; Westfall, J.; Fischer, D.; Plaschke, F.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Mauk, B.; Fuselier, S. A.

    2015-12-01

    The electrodynamics at the magnetopause is key to our understanding of ion and electron acceleration within reconnection regions. The Magnetospheric Multiscale (MMS) fleet of four spacecraft was launched into its Phase-1 equatorial orbit of 12 Re apogee specifically to investigate these regions at the Earth's magnetopause. In addition to a comprehensive suite of particle measurements, MMS makes very high time resolution 3D electric and magnetic field measurements of high accuracy using flux-gate, search coil, 3-axis double probe, and electron drift sensors. In September 2015, the MMS fleet will begin to encounter the dusk-side magnetopause in its initial configuration of approximately 160 km separation, allowing investigation of the spatial and temporal characteristics of important electrodynamics during reconnection. Using these field and particle measurements, we present first observations of 3D magnetic and electric fields (including their parallel component), and inferred current sheets, during active magnetopause crossings using the highest time resolution data available on MMS.

  6. Magnetic properties of Pd atomic chains formed during submonolayer deposition of 3d metals on Pd(110)

    NASA Astrophysics Data System (ADS)

    Stepanyuk, O. V.; Ignatiev, P. A.; Negulyaev, N. N.; Saletsky, A. M.; Hergert, W.

    2012-06-01

    Recently, an unusual intermixing-driven scenario for the growth of atomic Pd chains on a Pd(110) surface during deposition of 3d metal atoms has been predicted (Stepanyuk 2009 Phys. Rev. B 79 155410) and confirmed by STM and STS experiments (Wie et al 2009 Phys. Rev. Lett. 103 225504). Performing ab initio calculations we demonstrate that Pd atomic chains grown above embedded Fe atoms exhibit magnetic properties which depend on the substrate mediated exchange interaction between the Fe atoms.

  7. Magnetic properties of Pd atomic chains formed during submonolayer deposition of 3d metals on Pd(110).

    PubMed

    Stepanyuk, O V; Ignatiev, P A; Negulyaev, N N; Saletsky, A M; Hergert, W

    2012-06-13

    Recently, an unusual intermixing-driven scenario for the growth of atomic Pd chains on a Pd(110) surface during deposition of 3d metal atoms has been predicted (Stepanyuk 2009 Phys. Rev. B 79 155410) and confirmed by STM and STS experiments (Wie et al 2009 Phys. Rev. Lett. 103 225504). Performing ab initio calculations we demonstrate that Pd atomic chains grown above embedded Fe atoms exhibit magnetic properties which depend on the substrate mediated exchange interaction between the Fe atoms.

  8. Imaging a 3D geological structure from HEM, airborne magnetic and ground ERT data in Kalat-e-Reshm area, Iran

    NASA Astrophysics Data System (ADS)

    Shirzaditabar, Farzad; Bastani, Mehrdad; Oskooi, Behrooz

    2011-11-01

    A set of geophysical data collected in an area in Iran are analyzed to check the validity of a geological map that was prepared in connection to a mineral prospecting project and also to image the spatial electrical resistivity distribution. The data set includes helicopter electromagnetic (HEM), airborne magnetic and ground electrical resistivity measurement. Occam approach was used to invert the HEM data to model the resistivity using a layered earth model with fixed thicknesses. The algorithm is based on a nonlinear inverse problem in a least-squares sense. The algorithm was tested on a part of an HEM dataset acquired with a DIGHEM helicopter EM system at Kalat-e-Reshm, Semnan in Iran. The area contains a resistive porphyry andesite that is covered by Eocene sedimentary units. The results are shown as resistivity sections and maps confirming the existence of an arc like resistive structure in the survey area. The resistive andesite seems to be thicker than it is indicated in the geological maps. The results are compared with the reduced to the pole (RTP) airborne magnetic anomaly field data as well as with two ground resistivity profiles. We found reasonable correlations between the HEM 1D resistivity models and 2D models from electrical resistivity tomography (ERT) inversions. A 3D visualization of the 1D models along all flight lines provided a useful tool for the study of spatial variations of the resistivity structure in the investigation area.

  9. Investigation of Plutonic Rocks in Biga Peninsula, NW Turkey, using 3D Normalized Full Gradient of Magnetic Data

    NASA Astrophysics Data System (ADS)

    Ekinci, Y. L.; Yiǧitbaş, E.

    2012-04-01

    Airborne magnetic data of Biga Peninsula were investigated by using 3D Normalized Full Gradient (NFG) technique. The NFG procedure is based on the downward continuation of the potential field data and the NFG amplitude is calculated by dividing the Analytic Signal (AS) of downward continued magnetic data by the average of AS. Application of NFG technique usually enhances the anomalies by computing the anomaly to a level close to the source bodies and points to the boundaries of causative bodies. To that end, a MATLAB based code consisting of a series of linked functions was developed and used for analyses. Study area covers an area of 120 km x 180 km and the data were collected with 1-2 km profile intervals and with about 70 m sampling from 625 m above the ground surface by MTA (General Directorate of Mineral Research and Exploration). 2 km sampling intervals for both north and east directions were used for gridding of the magnetic data. Regional anomalies were approximated by means of element shape functions used in finite element method and then residuals were computed. Prior to the application of 3D NFG, Reduction to the Pole (RTP) transformation was applied to residual data in order to remove the complexity due to the effects of the direction of magnetization and ambient field. RTP transformation process was performed using 55 and 4 degrees for inclination and declination angles, respectively. 3D NFG operation was performed to reduced to pole data for 6 different depth levels (-200, -400, -600, -800, -1000 and -1200 m). Analyzing the resulting anomaly maps of different depth levels together with the geological map (1/500.000) showed that the locations of maximum NFG amplitudes indicate the boundaries of plutonic rocks having high magnetization intensity. Additionally, horizontal and vertical extensions of plutonic rocks were also determined. Keywords: Airborne magnetic data, normalized full gradient, plutonic rocks, Biga Peninsula-Turkey

  10. Skyrmions in quasi-2D chiral magnets with broken bulk and surface inversion symmetry (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Randeria, Mohit; Banerjee, Sumilan; Rowland, James

    2015-09-01

    Most theoretical studies of chiral magnetism, and the resulting spin textures, have focused on 3D systems with broken bulk inversion symmetry, where skyrmions are stabilized by easy-axis anisotropy. In this talk I will describe our results on 2D and quasi-2D systems with broken surface inversion, where we find [1] that skyrmion crystals are much more stable than in 3D, especially for the case of easy-plane anisotropy. These results are of particular interest for thin films, surfaces, and oxide interfaces [2], where broken surface-inversion symmetry and Rashba spin-orbit coupling naturally lead to both the chiral Dzyaloshinskii-Moriya (DM) interaction and to easy-plane compass anisotropy. I will then turn to systems that break both bulk and surface inversion, resulting in two distinct DM terms arising from Dresselhaus and Rashba spin-orbit coupling. I will describe [3] the evolution of the skyrmion structure and of the phase diagram as a function of the ratio of Dresselhaus and Rashba terms, which can be tuned by varying film thickness and strain. [1] S. Banerjee, J. Rowland, O. Erten, and M. Randeria, PRX 4, 031045 (2014). [2] S. Banerjee, O. Erten, and M. Randeria, Nature Phys. 9, 626 (2013). [3] J. Rowland, S. Banerjee and M. Randeria, (unpublished).

  11. Simulation of the 3-D Evolution of Electron Scale Magnetic Reconnection - Motivated by Laboratory Experiments Predictions for MMS

    NASA Astrophysics Data System (ADS)

    Buechner, J.; Jain, N.; Sharma, A.

    2013-12-01

    The four s/c of the Magnetospheric Multiscale (MMS) mission, to be launched in 2014, will use the Earth's magnetosphere as a laboratory to study the microphysics of three fundamental plasma processes. One of them is magnetic reconnection, an essentially multi-scale process. While laboratory experiments and past theoretical investigations have shown that important processes necessary to understand magnetic reconnection take place at electron scales the MMS mission for the first time will be able to resolve these scales by in space observations. For the measurement strategy of MMS it is important to make specific predictions of the behavior of current sheets with a thickness of the order of the electron skin depth which play an important role in the evolution of collisionless magnetic reconnection. Since these processes are highly nonlinear and non-local numerical simulation is needed to specify the current sheet evolution. Here we present new results about the nonlinear evolution of electron-scale current sheets starting from the linear stage and using 3-D electron-magnetohydrodynamic (EMHD) simulations. The growth rates of the simulated instabilities compared well with the growth rates obtained from linear theory. Mechanisms and conditions of the formation of flux ropes and of current filamentation will be discussed in comparison with the results of fully kinetic simulations. In 3D the X- and O-point configurations of the magnetic field formed in reconnection planes alternate along the out-of-reconnection-plane direction with the wavelength of the unstable mode. In the presence of multiple reconnection sites, the out-of-plane magnetic field can develop nested structure of quadrupoles in reconnection planes, similar to the 2-D case, but now with variations in the out-of-plane direction. The structures of the electron flow and magnetic field in 3-D simulations will be compared with those in 2-D simulations to discriminate the essentially 3D features. We also discuss

  12. Finite Element Treatment of Vortex States in 3D Cubic Superconductors in a Tilted Magnetic Field

    NASA Astrophysics Data System (ADS)

    Peng, Lin; Cai, Chuanbing

    2017-03-01

    The time-dependent Ginzburg-Landau equations have been solved numerically by a finite element analysis for superconducting samples with a cubic shape in a tilted magnetic field. We obtain different vortex patterns as a function of the external magnetic field. With a magnetic field not parallel to the x- or y-axis, the vortices attempt to change their orientation accordingly. Our analysis of the corresponding changes in the magnetic response in different directions can provide information not only about vorticity but also about the three-dimensional vortex arrangement, even about the very subtle changes for the superconducting samples with a cubic shape in a tilted magnetic field.

  13. Analyses of Magnetic Structures of Active Region 11117 Evolution using a 3D Data-Driven Magnetohydrodynamic Model

    NASA Astrophysics Data System (ADS)

    Wu, Shi; Jiang, Chaowei; Feng, Xueshang

    We use the photospheric vector magnetograms obtained by Helioseismic and Magnetic Image (HMI) on-board the Solar Dynamic Observatory (SDO) as the boundary conditions for a Data-Driven CESE-MHD model (Jiang et al. 2012) to investigate the physical characteristics and evolution of magnetic field configurations in the corona before and after a solar eruptive event. Specifically, the evolution of AR11117 characteristics such as length of magnetic shear along the neutral line, current helicity, magnetic free energy and the energy flux across the photosphere due to flux emergence and surface flow are presented. The computed 3D magnetic field configuration are compared with AIA (Atmosphere Image Assembly) which shows remarkable resemblance. A topological analyses reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare is caused by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of flare, while the computed magnetic free energy drops during the flare by 10 (30) ergs which is adequate in providing the energy budget of a minor C-class confined flare as observed. Jiang, Chaowei, Xueshang, Feng, S. T Wu and Qiang Hu, Ap. J., 759:85, 2012 Nov 10

  14. Influence of Critical Current Density on Magnetic Force of Htsc Bulk above Pmr with 3D-MODELING Numerical Solutions

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Lu, Bingjuan; Ge, Yunwang; Chen, Wenqing

    Numerical electromagnetic field simulations of high-temperature superconductors (HTSC) bulk were carried out to calculate the magnetic force between the HTSC bulk and the permanent magnet railway (PMR). A 3D-modeling numerical calculation method is proposed using the finite element method. The model is formulated with the magnetic field vector (H-method). The resulting code was written with FORTRAN language. The electric field intensity E and the current density J constitutive relation of HTSC were described with E-J power law. The Kim macro-model is used to describe critical current density Jc of HTSC bulk. Two virtual HTSC bulks were used to solve the critical current density Jc anisotropic properties of HTSC materials. A superconducting levitation system composed of one HTSC bulk and PMR is successfully investigated using the proposed method. By this method, the influence of critical current density on magnetic levitation force of the superconducting levitation system is mathematically studied.

  15. Identification of source velocities on 3D structures in non-anechoic environments: Theoretical background and experimental validation of the inverse patch transfer functions method

    NASA Astrophysics Data System (ADS)

    Aucejo, M.; Totaro, N.; Guyader, J.-L.

    2010-08-01

    In noise control, identification of the source velocity field remains a major problem open to investigation. Consequently, methods such as nearfield acoustical holography (NAH), principal source projection, the inverse frequency response function and hybrid NAH have been developed. However, these methods require free field conditions that are often difficult to achieve in practice. This article presents an alternative method known as inverse patch transfer functions, designed to identify source velocities and developed in the framework of the European SILENCE project. This method is based on the definition of a virtual cavity, the double measurement of the pressure and particle velocity fields on the aperture surfaces of this volume, divided into elementary areas called patches and the inversion of impedances matrices, numerically computed from a modal basis obtained by FEM. Theoretically, the method is applicable to sources with complex 3D geometries and measurements can be carried out in a non-anechoic environment even in the presence of other stationary sources outside the virtual cavity. In the present paper, the theoretical background of the iPTF method is described and the results (numerical and experimental) for a source with simple geometry (two baffled pistons driven in antiphase) are presented and discussed.

  16. Full source tensor inversions of San Jacinto fault zone earthquakes using 3D Green's functions with the gCAP method

    NASA Astrophysics Data System (ADS)

    Ross, Z.; Ben-Zion, Y.; Zhu, L.; Graves, R. W.

    2015-12-01

    We perform a full source tensor inversion of several M > 4 earthquakes that occurred in the San Jacinto fault zone in southern California, with an emphasis on resolving signatures of volumetric source changes. A previous study on these events with Green's functions based on a 1D velocity model identified statistically significant explosive isotropic components (Ross et al. 2015). Here we use the SCEC 3D Community Velocity Model to derive Green's functions with source-receiver reciprocity and finite-difference calculations based on the code of Graves (1996). About 50 stations are used at epicentral distances of up to 55 km. The inversions are performed using the 'generalized Cut and Paste' method, which includes CLVD and isotropic components (Zhu and Ben-Zion 2013). The derived source tensors are compared to the results of the previous study based on the simplified 1D velocity model. The results are analyzed with bootstrap analysis to estimate uncertainties involved. Additional tests are performed using synthetic waveforms to study the effects of neglecting various features on the source inversions.

  17. Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells

    PubMed Central

    Navau, Carles; Mach-Batlle, Rosa; Parra, Albert; Prat-Camps, Jordi; Laut, Sergi; Del-Valle, Nuria; Sanchez, Alvaro

    2017-01-01

    Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio. When the applied field is non-uniform, as for dipolar magnetic field sources, field gradient is increased as well. A proof-of-concept experimental realization confirms the theoretical predictions. The metamaterial shell is also shown to concentrate time-dependent magnetic fields upto frequencies of 100 kHz. PMID:28303951

  18. Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells.

    PubMed

    Navau, Carles; Mach-Batlle, Rosa; Parra, Albert; Prat-Camps, Jordi; Laut, Sergi; Del-Valle, Nuria; Sanchez, Alvaro

    2017-03-17

    Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio. When the applied field is non-uniform, as for dipolar magnetic field sources, field gradient is increased as well. A proof-of-concept experimental realization confirms the theoretical predictions. The metamaterial shell is also shown to concentrate time-dependent magnetic fields upto frequencies of 100 kHz.

  19. Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells

    NASA Astrophysics Data System (ADS)

    Navau, Carles; Mach-Batlle, Rosa; Parra, Albert; Prat-Camps, Jordi; Laut, Sergi; Del-Valle, Nuria; Sanchez, Alvaro

    2017-03-01

    Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio. When the applied field is non-uniform, as for dipolar magnetic field sources, field gradient is increased as well. A proof-of-concept experimental realization confirms the theoretical predictions. The metamaterial shell is also shown to concentrate time-dependent magnetic fields upto frequencies of 100 kHz.

  20. Perineal body anatomy in living women: 3-D analysis using thin-slice magnetic resonance imaging

    PubMed Central

    Larson, Kindra A.; Yousuf, Aisha; Lewicky-Gaupp, Christina; Fenner, Dee E.; DeLancey, John O.L.

    2012-01-01

    Objective To describe a framework for visualizing the perineal body's complex anatomy using thin-slice MR imaging. Study Design Two mm-thick MR images were acquired in 11 women with normal pelvic support and no incontinence/prolapse symptoms. Anatomic structures were analyzed in axial, sagittal and coronal slices. 3-D models were generated from these images. Results Three distinct perineal body regions are visible on MRI: (1) a superficial region at the level of the vestibular bulb, (2) a mid region at the proximal end of the superficial transverse perineal muscle, and (3) a deep region at the level of the midurethra and puborectalis muscle. Structures are best visualized on axial scans while cranio-caudal relationships are appreciated on sagittal scans. The 3-D model further clarifies inter-relationships. Conclusion Advances in MR technology allow visualization of perineal body anatomy in living women and development of 3D models which enhance our understanding of its three different regions: superficial, mid and deep. PMID:21055513

  1. Mini-conference Poster: 3D Onset and Propagation of Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Lapenta, Giovanni; Ricci, P.; Brackbill, J. U.; Daughton, W.; Delzanno, G. L.

    2005-10-01

    A fundamental problem in reconnection physics is how to relate 2D and 3D reconnection. The great majority of studies of reconnection focus on 2D configurations. The state of affair is best described by the cave allegory of Plato. In 2D we look at the reconnection process as if we were studying the real world through its reflections on the walls of a cave [1]. We propose to turn our head away from the familiar wall and face the real world. We do 3D fully kinetic (i.e. both electrons and ions are kinetic) simulations of reconnection. We use the implicit PIC code CELESTE to achieve parameter ranges and system sizes inaccessible to traditional explicit codes. Our results will clarify the fundamental issue: if reconnection is started at one location, does it propagate in the system? How? And what coupling of microscopic and macroscopic processes causes the reconnection onset in the first place? All these effects can only be studied in 3D [2]. The crucial physics missing in 2D simulations is the role of macroscopic equilibrium changes induced by the microinstabilities [3].1) Plato, Republic, Book VII, Hackett Pub. Co., 1992. 2) P. Ricci, J.U. Brackbill, W.S. Daughton, G. Lapenta, Phys. Plasmas, 11, 4489, 2004.3) W. Daughton, G. Lapenta, P. Ricci, Phys. Rev. Lett., 93, 105004, 2004.

  2. Three-dimensional inverse modelling of magnetic anomaly sources based on a genetic algorithm

    NASA Astrophysics Data System (ADS)

    Montesinos, Fuensanta G.; Blanco-Montenegro, Isabel; Arnoso, José

    2016-04-01

    We present a modelling method to estimate the 3-D geometry and location of homogeneously magnetized sources from magnetic anomaly data. As input information, the procedure needs the parameters defining the magnetization vector (intensity, inclination and declination) and the Earth's magnetic field direction. When these two vectors are expected to be different in direction, we propose to estimate the magnetization direction from the magnetic map. Then, using this information, we apply an inversion approach based on a genetic algorithm which finds the geometry of the sources by seeking the optimum solution from an initial population of models in successive iterations through an evolutionary process. The evolution consists of three genetic operators (selection, crossover and mutation), which act on each generation, and a smoothing operator, which looks for the best fit to the observed data and a solution consisting of plausible compact sources. The method allows the use of non-gridded, non-planar and inaccurate anomaly data and non-regular subsurface partitions. In addition, neither constraints for the depth to the top of the sources nor an initial model are necessary, although previous models can be incorporated into the process. We show the results of a test using two complex synthetic anomalies to demonstrate the efficiency of our inversion method. The application to real data is illustrated with aeromagnetic data of the volcanic island of Gran Canaria (Canary Islands).

  3. Combined magnetic vector-scalar potential finite element computation of 3D magnetic field and performance of modified Lundell alternators in Space Station applications. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Wang, Ren H.

    1991-01-01

    A method of combined use of magnetic vector potential (MVP) based finite element (FE) formulations and magnetic scalar potential (MSP) based FE formulations for computation of three-dimensional (3D) magnetostatic fields is developed. This combined MVP-MSP 3D-FE method leads to considerable reduction by nearly a factor of 3 in the number of unknowns in comparison to the number of unknowns which must be computed in global MVP based FE solutions. This method allows one to incorporate portions of iron cores sandwiched in between coils (conductors) in current-carrying regions. Thus, it greatly simplifies the geometries of current carrying regions (in comparison with the exclusive MSP based methods) in electric machinery applications. A unique feature of this approach is that the global MSP solution is single valued in nature, that is, no branch cut is needed. This is again a superiority over the exclusive MSP based methods. A Newton-Raphson procedure with a concept of an adaptive relaxation factor was developed and successfully used in solving the 3D-FE problem with magnetic material anisotropy and nonlinearity. Accordingly, this combined MVP-MSP 3D-FE method is most suited for solution of large scale global type magnetic field computations in rotating electric machinery with very complex magnetic circuit geometries, as well as nonlinear and anisotropic material properties.

  4. Combined magnetic vector-scalar potential finite element computation of 3D magnetic field and performance of modified Lundell alternators in Space Station applications

    NASA Astrophysics Data System (ADS)

    Wang, Ren H.

    1991-02-01

    A method of combined use of magnetic vector potential (MVP) based finite element (FE) formulations and magnetic scalar potential (MSP) based FE formulations for computation of three-dimensional (3D) magnetostatic fields is developed. This combined MVP-MSP 3D-FE method leads to considerable reduction by nearly a factor of 3 in the number of unknowns in comparison to the number of unknowns which must be computed in global MVP based FE solutions. This method allows one to incorporate portions of iron cores sandwiched in between coils (conductors) in current-carrying regions. Thus, it greatly simplifies the geometries of current carrying regions (in comparison with the exclusive MSP based methods) in electric machinery applications. A unique feature of this approach is that the global MSP solution is single valued in nature, that is, no branch cut is needed. This is again a superiority over the exclusive MSP based methods. A Newton-Raphson procedure with a concept of an adaptive relaxation factor was developed and successfully used in solving the 3D-FE problem with magnetic material anisotropy and nonlinearity. Accordingly, this combined MVP-MSP 3D-FE method is most suited for solution of large scale global type magnetic field computations in rotating electric machinery with very complex magnetic circuit geometries, as well as nonlinear and anisotropic material properties.

  5. Structural, electronic and magnetic properties of 3d metal trioxide clusters-doped monolayer graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Rafique, Muhammad; Shuai, Yong; Tan, He-Ping; Hassan, Muhammad

    2017-03-01

    We present first-principles density-functional calculations for the structural, electronic and magnetic properties of monolayer graphene doped with 3d (Ti, V, Cr, Fe, Co, Mn and Ni) metal trioxide TMO3 halogen clusters. In this paper we used two approaches for 3d metal trioxide clusters (i) TMO3 halogen cluster was embedded in monolayer graphene substituting four carbon (C) atoms (ii) three C atoms were substituted by three oxygen (O) atoms in one graphene ring and TM atom was adsorbed at the hollow site of O atoms substituted graphene ring. All the impurities were tightly bonded in the graphene ring. In first case of TMO3 doped graphene layer, the bond length between Csbnd O atom was reduced and bond length between TM-O atom was increased. In case of Cr, Fe, Co and Ni atoms substitution in between the O atoms, leads to Fermi level shifting to conduction band thereby causing the Dirac cone to move into valence band, however a band gap appears at high symmetric K-point. In case of TiO3 and VO3 substitution, system exhibits semiconductor properties. Interestingly, TiO3-substituted system shows dilute magnetic semiconductor behavior with 2.00 μB magnetic moment. On the other hand, the substitution of CoO3, CrO3, FeO3 and MnO3 induced 1.015 μB, 2.347 μB, 2.084 μB and 3.584 μB magnetic moment, respectively. In second case of O atoms doped in graphene and TM atoms adsorbed at the hollow site, the O atom bulges out of graphene plane and bond length between TM-O atom is increased. After TM atoms adsorption at the O substituted graphene ring the Fermi level (EF) shifts into conduction band. In case of Cr and Ni adsorption, system displays indirect band gap semiconductor properties with 0.0 μB magnetic moment. Co adsorption exhibits dilute magnetic semiconductor behavior producing 0.916 μB magnetic moment. Fe, Mn, Ti and V adsorption introduces band gap at high symmetric K-point also inducing 1.54 μB, 0.9909 μB, 1.912 μB, and 0.98 μB magnetic moments, respectively

  6. A spheroid toxicity assay using magnetic 3D bioprinting and real-time mobile device-based imaging

    PubMed Central

    Tseng, Hubert; Gage, Jacob A.; Shen, Tsaiwei; Haisler, William L.; Neeley, Shane K.; Shiao, Sue; Chen, Jianbo; Desai, Pujan K.; Liao, Angela; Hebel, Chris; Raphael, Robert M.; Becker, Jeanne L.; Souza, Glauco R.

    2015-01-01

    An ongoing challenge in biomedical research is the search for simple, yet robust assays using 3D cell cultures for toxicity screening. This study addresses that challenge with a novel spheroid assay, wherein spheroids, formed by magnetic 3D bioprinting, contract immediately as cells rearrange and compact the spheroid in relation to viability and cytoskeletal organization. Thus, spheroid size can be used as a simple metric for toxicity. The goal of this study was to validate spheroid contraction as a cytotoxic endpoint using 3T3 fibroblasts in response to 5 toxic compounds (all-trans retinoic acid, dexamethasone, doxorubicin, 5′-fluorouracil, forskolin), sodium dodecyl sulfate (+control), and penicillin-G (−control). Real-time imaging was performed with a mobile device to increase throughput and efficiency. All compounds but penicillin-G significantly slowed contraction in a dose-dependent manner (Z’ = 0.88). Cells in 3D were more resistant to toxicity than cells in 2D, whose toxicity was measured by the MTT assay. Fluorescent staining and gene expression profiling of spheroids confirmed these findings. The results of this study validate spheroid contraction within this assay as an easy, biologically relevant endpoint for high-throughput compound screening in representative 3D environments. PMID:26365200

  7. 3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

    NASA Astrophysics Data System (ADS)

    Shimizu, T.

    2015-10-01

    The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.

  8. 3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

    SciTech Connect

    Shimizu, T.

    2015-10-15

    The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.

  9. Crystal, magnetic and electronic structures of 3d-5d ordered double perovskite Ba2CoReO6

    NASA Astrophysics Data System (ADS)

    Musa Saad H.-E., M.; Rammeh, N.

    2016-12-01

    A comprehensive study on crystal, magnetic and electronic structures of ordered double perovskite Ba2CoReO6 was carried out using X-ray powder diffraction (XRD) and superconducting quantum interference device (SQUID). Also, the density functional theory (DFT) calculations were performed by full potential linear muffin-tin orbital (FP-LMTO) method within the localized spin density approximation (LSDA+U) and generalized gradient approximation (GGA+U). At room temperature, the crystal structure of Ba2CoReO6 is face-centered cubic, space group Fm 3 bar m , containing an almost completely ordered arrangement of CoO6-ReO6 octahedra. Magnetic structure showed an antiferromagnetic (AF) behavior below TN=41 K. The magnetic and electronic structures are consistent with the electronic configurations Co2+(3d7)-Re6+(5d1) having a total spin magnetic moment of about 2.0 μB/f.u. DFT electronic structures predicted half-metallic yields from 3d-t2g↓ and 5d-t2g↓ through O2-.

  10. 3D positional control of magnetic levitation system using adaptive control: improvement of positioning control in horizontal plane

    NASA Astrophysics Data System (ADS)

    Nishino, Toshimasa; Fujitani, Yasuhiro; Kato, Norihiko; Tsuda, Naoaki; Nomura, Yoshihiko; Matsui, Hirokazu

    2012-01-01

    The objective of this paper is to establish a technique that levitates and conveys a hand, a kind of micro-robot, by applying magnetic forces: the hand is assumed to have a function of holding and detaching the objects. The equipment to be used in our experiments consists of four pole-pieces of electromagnets, and is expected to work as a 4DOF drive unit within some restricted range of 3D space: the three DOF are corresponding to 3D positional control and the remaining one DOF, rotational oscillation damping control. Having used the same equipment, Khamesee et al. had manipulated the impressed voltages on the four electric magnetics by a PID controller by the use of the feedback signal of the hand's 3D position, the controlled variable. However, in this system, there were some problems remaining: in the horizontal direction, when translating the hand out of restricted region, positional control performance was suddenly degraded. The authors propose a method to apply an adaptive control to the horizontal directional control. It is expected that the technique to be presented in this paper contributes not only to the improvement of the response characteristic but also to widening the applicable range in the horizontal directional control.

  11. A 3-D Magnetic Analysis of a Stirling Convertor Linear Alternator Under Load

    NASA Technical Reports Server (NTRS)

    Geng, Steven M.; Schwarze, Gene E.; Niedra, Janis M.; Regan, Timothy F.

    2001-01-01

    The NASA Glenn Research Center (GRC), the Department of Energy (DOE), and the Stirling Technology Company (STC) are developing Stirling convertors for Stirling Radioisotope Power Systems (SRPS) to provide electrical power for future NASA deep space missions. STC is developing the 55-We Technology Demonstration Convertor (TDC) under contract to DOE. Of critical importance to the successful development of the Stirling convertor for space power applications is the development of a lightweight and highly efficient linear alternator. This paper presents a 3-dimensional finite element method (FEM) approach for evaluating Stirling convertor linear alternators. The model extends a magnetostatic analysis previously reported at the 35th Intersociety Energy Conversion Engineering Conference (IECEC) to include the effects of the load current. STC's 55-We linear alternator design was selected to validate the model. Spatial plots of magnetic field strength (H) are presented in the region of the exciting permanent magnets. The margin for permanent magnet demagnetization is calculated at the expected magnet operating temperature for the near earth environment and for various average magnet temperatures. These thermal conditions were selected to represent a worst-case condition for the planned deep space missions. This paper presents plots that identify regions of high H where the potential to alter the magnetic moment of the magnets exists.

  12. Reproducing electric field observations during magnetic storms by means of rigorous 3-D modelling and distortion matrix co-estimation

    NASA Astrophysics Data System (ADS)

    Püthe, Christoph; Manoj, Chandrasekharan; Kuvshinov, Alexey

    2014-12-01

    Electric fields induced in the conducting Earth by geomagnetic disturbances drive currents in power transmission grids, telecommunication lines or buried pipelines, which can cause service disruptions. A key step in the prediction of the hazard to technological systems during magnetic storms is the calculation of the geoelectric field. To address this issue for mid-latitude regions, we revisit a method that involves 3-D modelling of induction processes in a heterogeneous Earth and the construction of a magnetospheric source model described by low-degree spherical harmonics from observatory magnetic data. The actual electric field, however, is known to be perturbed by galvanic effects, arising from very local near-surface heterogeneities or topography, which cannot be included in the model. Galvanic effects are commonly accounted for with a real-valued time-independent distortion matrix, which linearly relates measured and modelled electric fields. Using data of six magnetic storms that occurred between 2000 and 2003, we estimate distortion matrices for observatory sites onshore and on the ocean bottom. Reliable estimates are obtained, and the modellings are found to explain up to 90% of the measurements. We further find that 3-D modelling is crucial for a correct separation of galvanic and inductive effects and a precise prediction of the shape of electric field time series during magnetic storms. Since the method relies on precomputed responses of a 3-D Earth to geomagnetic disturbances, which can be recycled for each storm, the required computational resources are negligible. Our approach is thus suitable for real-time prediction of geomagnetically induced currents by combining it with reliable forecasts of the source field.

  13. A thermoresponsive and magnetic colloid for 3D cell expansion and reconfiguration.

    PubMed

    Saeed, Aram; Francini, Nora; White, Lisa; Dixon, James; Gould, Toby; Rashidi, Hassan; Al Ghanami, Racha Cheikh; Hruschka, Veronika; Redl, Heinz; Saunders, Brian R; Alexander, Cameron; Shakesheff, Kevin M

    2015-01-27

    A dual thermoresponsive and magnetic colloidal gel matrix is described for enhanced stem-cell culture. The combined properties of the material allow enzyme-free passaging and expansion of mesenchymal stem cells, as well as isolation of cells postculture by the simple process of lowering the temperature and applying an external magnetic field. The colloidal gel can be reconfigured with thermal and magnetic stimuli to allow patterning of cells in discrete zones and to control movement of cells within the porous matrix during culture.

  14. A 3D oxalate-based network as a precursor for the CoMn₂O₄ spinel: synthesis and structural and magnetic studies.

    PubMed

    Habjanič, Jelena; Jurić, Marijana; Popović, Jasminka; Molčanov, Krešimir; Pajić, Damir

    2014-09-15

    A novel heterometallic oxalate-based compound of the formula {[Co(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), and magnetization measurement. The molecular structure of 1 is made of a three-dimensional (3D) anionic network, [Mn2(C2O4)3]n(2n-), and tris-chelated cations [Co(bpy)3](2+) occupying the vacancies of the framework. Splitting between the zero-field-cooled (ZFC) and field-cooled (FC) branches of susceptibility below the small peak at 13 K indicates magnetic ordering. Compound 1 was used as a single-source precursor for the formation of the mixed-metal oxide CoMn2O4. This conversion via thermal decomposition was explored by thermal analysis (TGA and DTA), IR spectroscopy, powder XRD, and magnetic susceptibility measurement. From refined structural parameters, it could be seen that the spinel obtained by the thermal treatment of 1 at 800 °C is characterized by the inversion parameter δ = 21%, and therefore the structural formula at room temperature can be written as (tet)[Co(0.79)Mn(0.21)](oct)[Co(0.105)Mn(0.895)]2O4. The temperature dependence of magnetization for CoMn2O4 points to at least three magnetic phases: the ferrimagnetic state is observed below 83 K, and up to 180 K blocking of the magnetic moments of nanocrystallites of 31 nm appears, transforming to paramagnetic-like behavior above 180 K. Microstructural characterization of the CoMn2O4 sample was carried out by means of XRD line-broadening analysis.

  15. Electric current variations and 3D magnetic configuration of coronal jets

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Harra, Louise K.; Aulanier, Guillaume; Guo, Yang; Demoulin, Pascal; Moreno-Insertis, Fernando, , Prof

    Coronal jets (EUV) were observed by SDO/AIA on September 17, 2010. HMI and THEMIS measured the vector magnetic field from which we derived the magnetic flux, the phostospheric velocity and the vertical electric current. The magnetic configuration was computed with a non linear force-free approach. The phostospheric current pattern of the recurrent jets were associated with the quasi-separatrix layers deduced from the magnetic extrapolation. The large twisted near-by Eiffel-tower-shape jet was also caused by reconnection in current layers containing a null point. This jet cannot be classified precisely within either the quiescent or the blowout jet types. We will show the importance of the existence of bald patches in the low atmosphere

  16. 3D field calculation of the GEM prototype magnet and comparison with measurements

    SciTech Connect

    Lari, R.J.

    1983-10-28

    The proposed 4 GeV Electron Microtron (GEM) is designed to fill the existing buildings left vacant by the demise of the Zero Gradient Synchrotron (ZGS) accelerator. One of the six large dipole magnets is shown as well as the first 10 electron orbits. A 3-orbit prototype magnet has been built. The stepped edge of the magnet is to keep the beam exiting perpendicular to the pole. The end guards that wrap around the main coils are joined together by the 3 shield plates. The auxiliary coils are needed to keep the end guards and shield plates from saturating. A 0.3 cm Purcell filter air gap exists between the pole and the yoke. Can anyone question this being a truly three-dimensional magnetostatic problem. The computer program TOSCA, developed at the Rutherford Appleton Laboratory by the Computing Applications Group, was used to calculate this magnet and the results have been compared with measurements.

  17. 3-D RPIC Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Hededal, C. B.; Fishman, G. J.

    2006-01-01

    Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets into ambient plasmas show that acceleration occurs in relativistic shocks. The Weibel instability created in shocks is responsible for particle acceleration, and generation and amplification of highly inhomogeneous, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection in relativistic jets. The "jitter" radiation from deflected electrons has different properties than the synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understand the complex time evolution and spectral structure in relativistic jets and gamma-ray bursts. We will present recent PIC simulations which show particle acceleration and magnetic field generation. We will also calculate associated self-consistent emission from relativistic shocks.

  18. 3D magnetic interactions of stars with their close-in planets

    NASA Astrophysics Data System (ADS)

    Strugarek, Antoine; Brun, Allan Sacha; Matt, Sean; Réville, Victor

    2015-08-01

    Close-in planets generally orbit in a sub-alfv ´enic stellar wind, where the perturbations they excite in the corona are able to travel upwind to the stellar surface and potentially induce observable phenomena. The effective connection between the planet and its host takes the form of two Aflv ´en wings. Depending on the topology of the planetary and stellar magnetic fields, the rotation profile of the corona, and the orbital parameters, it is possible that none, one, or the two Aflv ´en wings connect together the star and the planet.We explore the formation and sustainment of Alfv ´en wings in global three dimensional simulations under the magneto-hydrodynamic formalism with the PLUTO code. We model the stellar wind of a typical cool star in which a close-in orbiting planet is introduced as a boundary condition. By varying the magnetic topologies of the planetary and stellar magnetic fields, we explore the variety of Alfv ´en wings that can develop and quantify the Poynting flux flowing through those wings. We thus provide estimates of the amount of magnetic energy these magnetic interactions can channel to the lower corona. We also quantify the phase and latitude offsets that can be expected between the planetary subpoint on the stellar surface and the actual location where energy is deposited. We summarize the typical situations (in terms of magnetic topology, stellar type, and orbital parameters) where the star-planet magnetic interaction could trigger observable flares. We conclude by extending our results to the cases of more complex, non-axisymmetric topologies of the observed magnetic fields for a few particular stars.

  19. 3D-Printed Permanent Magnets Outperform Conventional Versions, Conserve Rare Materials

    SciTech Connect

    Paranthaman, Parans

    2016-11-01

    Researchers at the Department of Energy’s Oak Ridge National Laboratory have demonstrated that permanent magnets produced by additive manufacturing can outperform bonded magnets made using traditional techniques while conserving critical materials. The project is part of DOE’s Critical Materials Institute (CMI), which seeks ways to eliminate and reduce reliance on rare earth metals and other materials critical to the success of clean energy technologies.

  20. 3D-Printed Permanent Magnets Outperform Conventional Versions, Conserve Rare Materials

    ScienceCinema

    Paranthaman, Parans

    2016-11-23

    Researchers at the Department of Energy’s Oak Ridge National Laboratory have demonstrated that permanent magnets produced by additive manufacturing can outperform bonded magnets made using traditional techniques while conserving critical materials. The project is part of DOE’s Critical Materials Institute (CMI), which seeks ways to eliminate and reduce reliance on rare earth metals and other materials critical to the success of clean energy technologies.

  1. Single crystalline cylindrical nanowires – toward dense 3D arrays of magnetic vortices

    PubMed Central

    Ivanov, Yurii P.; Chuvilin, Andrey; Vivas, Laura G.; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-01-01

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories. PMID:27030143

  2. Single crystalline cylindrical nanowires – toward dense 3D arrays of magnetic vortices

    NASA Astrophysics Data System (ADS)

    Ivanov, Yurii P.; Chuvilin, Andrey; Vivas, Laura G.; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-03-01

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

  3. Photonic bandgap extension of surface-disordered 3D photonic crystals based on the TiO2 inverse opal architecture.

    PubMed

    Wang, Aijun; Liu, Wenfang; Tang, Junjie; Chen, Sheng-Li; Dong, Peng

    2014-04-15

    A photonic bandgap (PBG) extension of surface-disordered 3D photonic crystals (PCs) based on the TiO2 inverse opal (TiO2-IO) architecture has been demonstrated. By using a liquid phase deposition (LPD) process based on the controlled hydrolysis of ammonium hexafluorotitanate and boric acid, an extra layer of TiO2 nanoparticles were deposited onto the internal surface of the air voids in the TiO2-IOs to increase their surface roughness, thereby introducing surface disorder in the 3D order structures. The PBG relative width of surface-disordered TiO2-IOs has been broadened significantly, and, compared to the original TiO2-IO, its largest rate of increase (27%) has been obtained. It was found that the PBG relative width increased rapidly at first and then to a much slower rate of change with increase of the duration of the LPD time. A possible cause for this finding is discussed in this Letter.

  4. Inverse-power-law behavior of cellular motility reveals stromal–epithelial cell interactions in 3D co-culture by OCT fluctuation spectroscopy

    PubMed Central

    Oldenburg, Amy L.; Yu, Xiao; Gilliss, Thomas; Alabi, Oluwafemi; Taylor, Russell M.; Troester, Melissa A.

    2015-01-01

    The progression of breast cancer is known to be affected by stromal cells within the local microenvironment. Here we study the effect of stromal fibroblasts on the in-place motions (motility) of mammary epithelial cells within organoids in 3D co-culture, inferred from the speckle fluctuation spectrum using optical coherence tomography (OCT). In contrast to Brownian motion, mammary cell motions exhibit an inverse power-law fluctuation spectrum. We introduce two complementary metrics for quantifying fluctuation spectra: the power-law exponent and a novel definition of the motility amplitude, both of which are signal- and position-independent. We find that the power-law exponent and motility amplitude are positively (p<0.001) and negatively (p<0.01) correlated with the density of stromal cells in 3D co-culture, respectively. We also show how the hyperspectral data can be visualized using these metrics to observe heterogeneity within organoids. This constitutes a simple and powerful tool for detecting and imaging cellular functional changes with OCT. PMID:26973862

  5. CONTINUUM INTENSITY AND [O i] SPECTRAL LINE PROFILES IN SOLAR 3D PHOTOSPHERIC MODELS: THE EFFECT OF MAGNETIC FIELDS

    SciTech Connect

    Fabbian, D.; Moreno-Insertis, F. E-mail: fmi@iac.es

    2015-04-01

    The importance of magnetic fields in three-dimensional (3D) magnetoconvection models of the Sun’s photosphere is investigated in terms of their influence on the continuum intensity at different viewing inclination angles and on the intensity profile of two [O i] spectral lines. We use the RH numerical radiative transfer code to perform a posteriori spectral synthesis on the same time series of magnetoconvection models used in our publications on the effect of magnetic fields on abundance determination. We obtain a good match of the synthetic disk-center continuum intensity to the absolute continuum values from the Fourier Transform Spectrometer (FTS) observational spectrum; the match of the center-to-limb variation synthetic data to observations is also good, thanks, in part, to the 3D radiation transfer capabilities of the RH code. The different levels of magnetic flux in the numerical time series do not modify the quality of the match. Concerning the targeted [O i] spectral lines, we find, instead, that magnetic fields lead to nonnegligible changes in the synthetic spectrum, with larger average magnetic flux causing both of the lines to become noticeably weaker. The photospheric oxygen abundance that one would derive if instead using nonmagnetic numerical models would thus be lower by a few to several centidex. The inclusion of magnetic fields is confirmed to be important for improving the current modeling of the Sun, here in particular in terms of spectral line formation and of deriving consistent chemical abundances. These results may shed further light on the still controversial issue regarding the precise value of the solar oxygen abundance.

  6. Reproducing Electric Field Observations during Magnetic Storms by means of Rigorous 3-D Modelling and Distortion Matrix Co-estimation

    NASA Astrophysics Data System (ADS)

    Püthe, Christoph; Manoj, Chandrasekharan; Kuvshinov, Alexey

    2015-04-01

    Electric fields induced in the conducting Earth during magnetic storms drive currents in power transmission grids, telecommunication lines or buried pipelines. These geomagnetically induced currents (GIC) can cause severe service disruptions. The prediction of GIC is thus of great importance for public and industry. A key step in the prediction of the hazard to technological systems during magnetic storms is the calculation of the geoelectric field. To address this issue for mid-latitude regions, we developed a method that involves 3-D modelling of induction processes in a heterogeneous Earth and the construction of a model of the magnetospheric source. The latter is described by low-degree spherical harmonics; its temporal evolution is derived from observatory magnetic data. Time series of the electric field can be computed for every location on Earth's surface. The actual electric field however is known to be perturbed by galvanic effects, arising from very local near-surface heterogeneities or topography, which cannot be included in the conductivity model. Galvanic effects are commonly accounted for with a real-valued time-independent distortion matrix, which linearly relates measured and computed electric fields. Using data of various magnetic storms that occurred between 2000 and 2003, we estimated distortion matrices for observatory sites onshore and on the ocean bottom. Strong correlations between modellings and measurements validate our method. The distortion matrix estimates prove to be reliable, as they are accurately reproduced for different magnetic storms. We further show that 3-D modelling is crucial for a correct separation of galvanic and inductive effects and a precise prediction of electric field time series during magnetic storms. Since the required computational resources are negligible, our approach is suitable for a real-time prediction of GIC. For this purpose, a reliable forecast of the source field, e.g. based on data from satellites

  7. 3D effects of edge magnetic field configuration on divertor/scrape-off layer transport and optimization possibilities for a future reactor

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Xu, Y.; Ida, K.; Corre, Y.; Feng, Y.; Schmitz, O.; Frerichs, H.; Tabares, F. L.; Evans, T. E.; Coenen, J. W.; Liang, Y.; Bader, A.; Itoh, K.; Yamada, H.; Ghendrih, Ph.; Ciraolo, G.; Tafalla, D.; Lopez-Fraguas, A.; Guo, H. Y.; Cui, Z. Y.; Reiter, D.; Asakura, N.; Wenzel, U.; Morita, S.; Ohno, N.; Peterson, B. J.; Masuzaki, S.

    2015-10-01

    This paper assesses the three-dimensional (3D) effects of the edge magnetic field structure on divertor/scrape-off layer transport, based on an inter-machine comparison of experimental data and on the recent progress of 3D edge transport simulation. The 3D effects are elucidated as a consequence of competition between transports parallel (\\parallel ) and perpendicular (\\bot ) to the magnetic field, in open field lines cut by divertor plates, or in magnetic islands. The competition has strong impacts on divertor functions, such as determination of the divertor density regime, impurity screening and detachment control. The effects of magnetic perturbation on the edge electric field and turbulent transport are also discussed. Parameterization to measure the 3D effects on the edge transport is attempted for the individual divertor functions. Based on the suggested key parameters, an operation domain of the 3D divertor configuration is discussed for future devices.

  8. Counting Magnetic Bipoles on the Sun by Polarity Inversion

    NASA Technical Reports Server (NTRS)

    Jones, Harrison P.

    2004-01-01

    This paper presents a simple and efficient algorithm for deriving images of polarity inversion from NSO/Kitt Peak magnetograms without use of contouring routines and shows by example how these maps depend upon the spatial scale for filtering the raw data. Smaller filtering scales produce many localized closed contours in mixed polarity regions while supergranular and larger filtering scales produce more global patterns. The apparent continuity of an inversion line depends on how the spatial filtering is accomplished, but its shape depends only on scale. The total length of the magnetic polarity inversion contours varies as a power law of the filter scale with fractal dimension of order 1.9. The amplitude but nut the exponent of this power-law relation varies with solar activity. The results are compared to similar analyses of areal distributions of bipolar magnetic regions.

  9. RKKY-like contributions to the magnetic anisotropy energy: 3 d adatoms on Pt(111) surface

    NASA Astrophysics Data System (ADS)

    Bouhassoune, Mohammmed; Dias, Manuel dos Santos; Zimmermann, Bernd; Dederichs, Peter H.; Lounis, Samir

    2016-09-01

    The magnetic anisotropy energy defines the energy barrier that stabilizes a magnetic moment. Utilizing density-functional-theory-based simulations and analytical formulations, we establish that this barrier is strongly modified by long-range contributions very similar to Friedel oscillations and Rudermann-Kittel-Kasuya-Yosida interactions. Thus, oscillations are expected and observed, with different decaying factors and highly anisotropic in realistic materials, which can switch nontrivially the sign of the magnetic anisotropy energy. This behavior is general, and for illustration we address the transition-metal adatoms, Cr, Mn, Fe, and Co deposited on a Pt(111) surface. We explain, in particular, the mechanisms leading to the strong site dependence of the magnetic anisotropy energy observed for Fe adatoms on a Pt(111) surface as revealed previously via first-principles-based simulations and inelastic scanning tunneling spectroscopy [A. A. Khajetoorians et al., Phys. Rev. Lett. 111, 157204 (2013), 10.1103/PhysRevLett.111.157204]. The same mechanisms are probably active for the site dependence of the magnetic anisotropy energy obtained for Fe adatoms on Pd or Rh(111) surfaces and for Co adatoms on a Rh(111) surface [P. Blonski et al., Phys. Rev. B 81, 104426 (2010), 10.1103/PhysRevB.81.104426].

  10. A novel method for assessing the 3-D orientation accuracy of inertial/magnetic sensors.

    PubMed

    Faber, Gert S; Chang, Chien-Chi; Rizun, Peter; Dennerlein, Jack T

    2013-10-18

    A novel method for assessing the accuracy of inertial/magnetic sensors is presented. The method, referred to as the "residual matrix" method, is advantageous because it decouples the sensor's error with respect to Earth's gravity vector (attitude residual error: pitch and roll) from the sensor's error with respect to magnetic north (heading residual error), while remaining insensitive to singularity problems when the second Euler rotation is close to ±90°. As a demonstration, the accuracy of an inertial/magnetic sensor mounted to a participant's forearm was evaluated during a reaching task in a laboratory. Sensor orientation was measured internally (by the inertial/magnetic sensor) and externally using an optoelectronic measurement system with a marker cluster rigidly attached to the sensor's enclosure. Roll, pitch and heading residuals were calculated using the proposed novel method, as well as using a common orientation assessment method where the residuals are defined as the difference between the Euler angles measured by the inertial sensor and those measured by the optoelectronic system. Using the proposed residual matrix method, the roll and pitch residuals remained less than 1° and, as expected, no statistically significant difference between these two measures of attitude accuracy was found; the heading residuals were significantly larger than the attitude residuals but remained below 2°. Using the direct Euler angle comparison method, the residuals were in general larger due to singularity issues, and the expected significant difference between inertial/magnetic sensor attitude and heading accuracy was not present.

  11. 3D hybrid simulations of the plasma penetration across a magnetic field

    NASA Astrophysics Data System (ADS)

    Omelchenko, Yuri

    2016-10-01

    The expansion of hot dense plasmas across ambient magnetic fields in physical systems with spatial scales comparable to the ion gyro and inertial lengths is of great interest to space physics and fusion. This work presents results from recent three-dimensional hybrid simulations (kinetic ions, fluid electrons) of experiments at the LAPD and Nevada Terawatt Facility where short-pulse lasers are used to ablate solid targets to produce plasmas that expand across external magnetic fields. The first simulation recreates flutelike density striations observed at the leading edge of the carbon plasma and predicts an early destruction of the magnetic cavity in agreement with experimental evidence. In the second simulation the plasma contains protons and carbon ions produced during the ablation of a polyethylene target. A mechanism is demonstrated that allows protons to penetrate the magnetic field in the form of a collimated flow while the carbon ion component forms a supporting magnetic structure. The role of ion kinetic and Hall effects in creating an electric field responsible for plasma transport is discussed and results are compared to experimental data. The hybrid simulations are performed with a massively parallel hybrid code, HYPERS that advances fields and particles asynchronously on time scales determined by local physical and geometric properties. Supported by US DOE Award DE-SC0012345.

  12. Locating magnetic reconnection x-lines in 3D PIC simulations

    NASA Astrophysics Data System (ADS)

    Olson, D. K.; Dorelli, J.; Daughton, W. S.; Karimabadi, H.

    2013-12-01

    In a three-dimensional PIC simulation of turbulent magnetic reconnection, a reconnection 'X-line' can be identified as a separator in the magnetic topology. From this x-line, it is possible to compute the reconnection rate by evaluating the line integral of the electric field along the separator. This technique is used in a reconnection simulation of a symmetric Harris sheet driven by inflow at the upstream boundaries with a strong guide field (such that the magnetic field is non-vanishing everywhere and there are no magnetic nulls). The results of this analysis are compared to the General Magnetic Reconnection theory (GMR) [Hesse and Schindler, 1998], showing that in this symmetric case GMR agrees with our topological approach to finding the location of the x-line. The parallel electric field is non-trivial along the entire length of the x-line, however, suggesting that the reconnection diffusion region cannot be identified by local measures of the breakdown of ideal MHD alone. We discuss the implications of these results for NASA's upcoming Magnetospheric Multiscale mission.

  13. Different scenarios for inverse estimation of soil hydraulic parameters from double-ring infiltrometer data using HYDRUS-2D/3D

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Parisa; Ghorbani-Dashtaki, Shoja; Mosaddeghi, Mohammad Reza; Shirani, Hossein; Nodoushan, Ali Reza Mohammadi

    2016-04-01

    In this study, HYDRUS-2D/3D was used to simulate ponded infiltration through double-ring infiltrometers into a hypothetical loamy soil profile. Twelve scenarios of inverse modelling (divided into three groups) were considered for estimation of Mualem-van Genuchten hydraulic parameters. In the first group, simulation was carried out solely using cumulative infiltration data. In the second group, cumulative infiltration data plus water content at h = -330 cm (field capacity) were used as inputs. In the third group, cumulative infiltration data plus water contents at h = -330 cm (field capacity) and h = -15 000 cm (permanent wilting point) were used simultaneously as predictors. The results showed that numerical inverse modelling of the double-ring infiltrometer data provided a reliable alternative method for determining soil hydraulic parameters. The results also indicated that by reducing the number of hydraulic parameters involved in the optimization process, the simulation error is reduced. The best one in infiltration simulation which parameters α, n, and Ks were optimized using the infiltration data and field capacity as inputs. Including field capacity as additional data was important for better optimization/definition of soil hydraulic functions, but using field capacity and permanent wilting point simultaneously as additional data increased the simulation error.

  14. A high-order 3D spectral-element method for the forward modelling and inversion of gravimetric data - Application to the western Pyrenees

    NASA Astrophysics Data System (ADS)

    Martin, Roland; Chevrot, Sébastien; Komatitsch, Dimitri; Seoane, Lucia; Spangenberg, Hannah; Wang, Yi; Dufréchou, Grégory; Bonvalot, Sylvain; Bruinsma, Sean

    2017-01-01

    We image the internal density structure of the Pyrenees by inverting gravity data using an a priori density model derived by scaling a Vp model obtained by full waveform inversion of teleseismic P-waves. Gravity anomalies are computed via a 3D high-order finite-element integration in the same high-order spectral-element grid as the one used to solve the wave equation and thus to obtain the velocity model. The curvature of the Earth and surface topography are taken into account in order to obtain a density model as accurate as possible. The method is validated through comparisons with exact semi-analytical solutions. We show that the spectral element method drastically accelerates the computations when compared to other more classical methods. Different scaling relations between compressional velocity and density are tested, and the Nafe-Drake relation is the one that leads to the best agreement between computed and observed gravity anomalies. Gravity data inversion is then performed and the results allow us to put more constraints on the density structure of the shallow crust and on the deep architecture of the mountain range.

  15. The effect of anisotropic heat transport on magnetic islands in 3-D configurations

    SciTech Connect

    Schlutt, M. G.; Hegna, C. C.

    2012-08-15

    An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.

  16. Non-magnetic photospheric bright points in 3D simulations of the solar atmosphere

    NASA Astrophysics Data System (ADS)

    Calvo, F.; Steiner, O.; Freytag, B.

    2016-11-01

    Context. Small-scale bright features in the photosphere of the Sun, such as faculae or G-band bright points, appear in connection with small-scale magnetic flux concentrations. Aims: Here we report on a new class of photospheric bright points that are free of magnetic fields. So far, these are visible in numerical simulations only. We explore conditions required for their observational detection. Methods: Numerical radiation (magneto-)hydrodynamic simulations of the near-surface layers of the Sun were carried out. The magnetic field-free simulations show tiny bright points, reminiscent of magnetic bright points, only smaller. A simple toy model for these non-magnetic bright points (nMBPs) was established that serves as a base for the development of an algorithm for their automatic detection. Basic physical properties of 357 detected nMBPs were extracted and statistically evaluated. We produced synthetic intensity maps that mimic observations with various solar telescopes to obtain hints on their detectability. Results: The nMBPs of the simulations show a mean bolometric intensity contrast with respect to their intergranular surroundings of approximately 20%, a size of 60-80 km, and the isosurface of optical depth unity is at their location depressed by 80-100 km. They are caused by swirling downdrafts that provide, by means of the centripetal force, the necessary pressure gradient for the formation of a funnel of reduced mass density that reaches from the subsurface layers into the photosphere. Similar, frequently occurring funnels that do not reach into the photosphere, do not produce bright points. Conclusions: Non-magnetic bright points are the observable manifestation of vertically extending vortices (vortex tubes) in the photosphere. The resolving power of 4-m-class telescopes, such as the DKIST, is needed for an unambiguous detection of them. The movie associated to Fig. 1 is available at http://www.aanda.org

  17. Observation of Magnetic Reconnection at a 3D Null Point Associated with a Solar Eruption

    NASA Astrophysics Data System (ADS)

    Sun, J. Q.; Zhang, J.; Yang, K.; Cheng, X.; Ding, M. D.

    2016-10-01

    Magnetic null has long been recognized as a special structure serving as a preferential site for magnetic reconnection (MR). However, the direct observational study of MR at null-points is largely lacking. Here, we show the observations of MR around a magnetic null associated with an eruption that resulted in an M1.7 flare and a coronal mass ejection. The Geostationary Operational Environmental Satellites X-ray profile of the flare exhibited two peaks at ∼02:23 UT and ∼02:40 UT on 2012 November 8, respectively. Based on the imaging observations, we find that the first and also primary X-ray peak was originated from MR in the current sheet (CS) underneath the erupting magnetic flux rope (MFR). On the other hand, the second and also weaker X-ray peak was caused by MR around a null point located above the pre-eruption MFR. The interaction of the null point and the erupting MFR can be described as a two-step process. During the first step, the erupting and fast expanding MFR passed through the null point, resulting in a significant displacement of the magnetic field surrounding the null. During the second step, the displaced magnetic field started to move back, resulting in a converging inflow and subsequently the MR around the null. The null-point reconnection is a different process from the current sheet reconnection in this flare; the latter is the cause of the main peak of the flare, while the former is the cause of the secondary peak of the flare and the conspicuous high-lying cusp structure.

  18. Analysis of 3-D Tongue Motion from Tagged and Cine Magnetic Resonance Images

    ERIC Educational Resources Information Center

    Xing, Fangxu; Woo, Jonghye; Lee, Junghoon; Murano, Emi Z.; Stone, Maureen; Prince, Jerry L.

    2016-01-01

    Purpose: Measuring tongue deformation and internal muscle motion during speech has been a challenging task because the tongue deforms in 3 dimensions, contains interdigitated muscles, and is largely hidden within the vocal tract. In this article, a new method is proposed to analyze tagged and cine magnetic resonance images of the tongue during…

  19. Use of 3-D magnetic resonance electrical impedance tomography in detecting human cerebral stroke: a simulation study*

    PubMed Central

    Gao, Nuo; Zhu, Shan-an; He, Bin

    2005-01-01

    We have developed a new three dimensional (3-D) conductivity imaging approach and have used it to detect human brain conductivity changes corresponding to acute cerebral stroke. The proposed Magnetic Resonance Electrical Impedance Tomography (MREIT) approach is based on the J-Substitution algorithm and is expanded to imaging 3-D subject conductivity distribution changes. Computer simulation studies have been conducted to evaluate the present MREIT imaging approach. Simulations of both types of cerebral stroke, hemorrhagic stroke and ischemic stroke, were performed on a four-sphere head model. Simulation results showed that the correlation coefficient (CC) and relative error (RE) between target and estimated conductivity distributions were 0.9245±0.0068 and 8.9997%±0.0084%, for hemorrhagic stroke, and 0.6748±0.0197 and 8.8986%±0.0089%, for ischemic stroke, when the SNR (signal-to-noise radio) of added GWN (Gaussian White Noise) was 40. The convergence characteristic was also evaluated according to the changes of CC and RE with different iteration numbers. The CC increases and RE decreases monotonously with the increasing number of iterations. The present simulation results show the feasibility of the proposed 3-D MREIT approach in hemorrhagic and ischemic stroke detection and suggest that the method may become a useful alternative in clinical diagnosis of acute cerebral stroke in humans. PMID:15822161

  20. Sensitivity of a 3D fully-gapped topological superconductor to non-magnetic impurities

    NASA Astrophysics Data System (ADS)

    Ota, Yukihiro; Nagai, Yuki; Machida, Masahiko

    2015-03-01

    Topological superconductors (TSC) are notable materials, owing to the mathematical curiosity and the application potential. The bulk TSC can emerge by copper intercalation into topological insulator Bi2Se3. In this paper, we theoretically study the non-magnetic impurity effects in the mean-field model of CuxBi2Se3, focusing on the odd-parity fully-gapped superconducting state. Calculating the density of states with a self-consistent T-matrix approach, we test the presence of mid-gap states, leading to pair-breaking effects. Remarkably, the sensitivity to non-magnetic impurities strongly depend on a normal-state dispersion character, i.e., either non-relativistic or relativistic dispersion relations. We show unification picture for understanding this intriguing result, deriving a low-energy effective superconducting theory.

  1. The feasibility assessment of radiation dose of movement 3D NIPAM gel by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Hsieh, Chih-Ming; Leung, Joseph Hang; Ng, Yu-Bun; Cheng, Chih-Wu; Sun, Jung-Chang; Lin, Ping-Chin; Hsieh, Bor-Tsung

    2015-11-01

    NIPAM dosimeter is widely accepted and recommended for its 3D distribution and accuracy in dose absorption. Up to the moment, most research works on dose measurement are based on a fixed irradiation target without the consideration of the effect from physiological motion. We present a study to construct a respiratory motion simulating patient anatomical and dosimetry model for the study of dosimetic effect of organ motion. The dose on fixed and motion targets was measured by MRI after a dose adminstration of 1, 2, 5, 8, and 10 Gy from linear accelerator. Comparison of two situations is made. The average sensitivity of fixed NIPAM was 0.1356 s-1/Gy with linearity R2=0.998. The average sensitivity of movement NIPAM was 0.1366 s-1/Gy with linearity R2=0.998 both having only 0.001 of the sensitivity difference. The difference between the two based on dose rate dependency, position and depth was not significant. There was thus no apparent impact on NIPAM dosimeter from physiological motion. The high sensitivity, linearity and stability of NIPAM dosimeter proved to be an ideal apparatus in the dose measurement in these circumstances.

  2. Simulations of Gyrosynchrotron Microwave Emission from an Oscillating 3D Magnetic Loop

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. A.; Van Doorsselaere, T.; Reznikova, V. E.

    2015-04-01

    Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission. Interpreting the observations requires comparing them with simulations. We simulated the gyrosynchrotron radio emission from a semicircular (toroidal-shaped) magnetic loop containing sausage-mode MHD oscillations. The aim was to detect the observable signatures specific to the considered MHD mode and to study their dependence on the various source parameters. The MHD waves were simulated using a linear three-dimensional model of a magnetized plasma cylinder; both standing and propagating waves were considered. The curved loop was formed by replicating the MHD solutions along the plasma cylinder and bending the cylinder; this model allowed us to study the effect of varying the viewing angle along the loop. The radio emission was simulated using a three-dimensional model, and its spatial and temporal variations were analyzed. We considered several loop orientations and different parameters of the magnetic field, plasma, and energetic electrons in the loop. In the model with low plasma density, the intensity oscillations at all frequencies are synchronous (with the exception of a narrow spectral region below the spectral peak). In the model with high plasma density, the emission at low frequencies (where the Razin effect is important) oscillates in anti-phase with the emissions at higher frequencies. The oscillations at high and low frequencies are more pronounced in different parts of the loop (depending on the loop orientation). The layers where the line-of-sight component of the magnetic field changes sign can produce additional peculiarities in the oscillation patterns.

  3. Adsorbent 2D and 3D carbon matrices with protected magnetic iron nanoparticles.

    PubMed

    Carreño, N L V; Escote, M T; Valentini, A; McCafferty, L; Stolojan, V; Beliatis, M; Mills, C A; Rhodes, R; Smith, C T G; Silva, S R P

    2015-11-07

    We report on the synthesis of two and three dimensional carbonaceous sponges produced directly from graphene oxide (GO) into which functionalized iron nanoparticles can be introduced to render it magnetic. This simple, low cost procedure, wherein an iron polymeric resin precursor is introduced into the carbon framework, results in carbon-based materials with specific surface areas of the order of 93 and 66 m(2) g(-1), compared to approx. 4 m(2) g(-1) for graphite, decorated with ferromagnetic iron nanoparticles giving coercivity fields postulated to be 216 and 98 Oe, values typical for ferrite magnets, for 3.2 and 13.5 wt% Fe respectively. The strongly magnetic iron nanoparticles are robustly anchored to the GO sheets by a layer of residual graphite, on the order of 5 nm, formed during the pyrolysis of the precursor material. The applicability of the carbon sponges is demonstrated in their ability to absorb, store and subsequently elute an organic dye, Rhodamine B, from water as required. It is possible to regenerate the carbon-iron hybrid material after adsorption by eluting the dye with a solvent to which it has a high affinity, such as ethanol. The use of a carbon framework opens the hybrid materials to further chemical functionalization, for enhanced chemical uptake of contaminants, or co-decoration with, for example, silver nanoparticles for bactericidal properties. Such analytical properties, combined with the material's magnetic character, offer solutions for environmental decontamination at land and sea, wastewater purification, solvent extraction, and for the concentration of dilute species.

  4. Adsorbent 2D and 3D carbon matrices with protected magnetic iron nanoparticles

    NASA Astrophysics Data System (ADS)

    Carreño, N. L. V.; Escote, M. T.; Valentini, A.; McCafferty, L.; Stolojan, V.; Beliatis, M.; Mills, C. A.; Rhodes, R.; Smith, C. T. G.; Silva, S. R. P.

    2015-10-01

    We report on the synthesis of two and three dimensional carbonaceous sponges produced directly from graphene oxide (GO) into which functionalized iron nanoparticles can be introduced to render it magnetic. This simple, low cost procedure, wherein an iron polymeric resin precursor is introduced into the carbon framework, results in carbon-based materials with specific surface areas of the order of 93 and 66 m2 g-1, compared to approx. 4 m2 g-1 for graphite, decorated with ferromagnetic iron nanoparticles giving coercivity fields postulated to be 216 and 98 Oe, values typical for ferrite magnets, for 3.2 and 13.5 wt% Fe respectively. The strongly magnetic iron nanoparticles are robustly anchored to the GO sheets by a layer of residual graphite, on the order of 5 nm, formed during the pyrolysis of the precursor material. The applicability of the carbon sponges is demonstrated in their ability to absorb, store and subsequently elute an organic dye, Rhodamine B, from water as required. It is possible to regenerate the carbon-iron hybrid material after adsorption by eluting the dye with a solvent to which it has a high affinity, such as ethanol. The use of a carbon framework opens the hybrid materials to further chemical functionalization, for enhanced chemical uptake of contaminants, or co-decoration with, for example, silver nanoparticles for bactericidal properties. Such analytical properties, combined with the material's magnetic character, offer solutions for environmental decontamination at land and sea, wastewater purification, solvent extraction, and for the concentration of dilute species.

  5. Inverse magnetic catalysis in holographic models of QCD

    NASA Astrophysics Data System (ADS)

    Mamo, Kiminad A.

    2015-05-01

    We study the effect of magnetic field B on the critical temperature T c of the confinement-deconfinement phase transition in hard-wall AdS/QCD, and holographic duals of flavored and unflavored super-Yang Mills theories on . For all of the holographic models, we find that T c ( B) decreases with increasing magnetic field B ≪ T 2, consistent with the inverse magnetic catalysis recently observed in lattice QCD for B ≲ 1 GeV2. We also predict that, for large magnetic field B ≫ T 2, the critical temperature T c ( B), eventually, starts to increase with increasing magnetic field B ≫ T 2 and asymptotes to a constant value.

  6. Orbital driven impurity spin effect on the magnetic order of quasi-3D cupric oxide

    NASA Astrophysics Data System (ADS)

    Ganga, B. G.; Santhosh, P. N.; Nanda, B. R. K.

    2017-04-01

    Density functional calculations are performed to study the magnetic order of the severely distorted square planar cupric oxide (CuO) and local spin disorder in it in the presence of the transition metal impurities M (=Cr, Mn, Fe, Co and Ni). The distortion in the crystal structure, arisen to reduce the band energy by minimizing the covalent interaction, creates two crisscrossing zigzag spin-1/2 chains. From the spin dimer analysis we find that while the spin chain along ≤ft[1 0 \\bar{1}\\right] has strong Heisenberg type antiferromagnetic coupling (J ~ 127 meV), along ≤ft[1 0 1\\right] it exhibits weak, but robust, ferromagnetic coupling (J ~ 9 meV) mediated by reminiscent p-d covalent interactions. The impurity effect on the magnetic ordering is independent of M and purely orbital driven. If the given spin-state of M is such that the {{d}{{x2}-{{y}2}}} orbital is spin-polarized, then the original long-range ordering is maintained. However, if {{d}{{x2}-{{y}2}}} orbital is unoccupied, the absence of corresponding covalent interaction breaks the weak ferromagnetic coupling and a spin-flip takes place at the impurity site leading to breakdown of the long range magnetic ordering.

  7. 3-D Modelling of Magnetic Data from an Archaeological Site in Northwestern Tlaxcala State, Mexico

    NASA Astrophysics Data System (ADS)

    Chavez, R. E.; Argote, D. L.; Cifuentes, G.; Tejero, A.; Camara, E.

    2009-05-01

    In Archaeology, geophysical methods had been applied usually in a qualitative form, limited only to the use of filters that enhance the data display. The main objective in this work is the implementation of a modeling technique that allows us to reconstruct the geometry of buried bodies and the determination of their depths. This is done by means of the estimation of the magnetic moments of archaeological objects using a three- dimensional mesh of individual magnetic dipoles using the least squares method and the singular value decomposition of a weighted matrix to solve the linear problem. The distribution and shape of the underlying archaeological remains can be inferred. This methodology was applied to an archaeological site called Los Teteles de Ocotitla, in the state of Tlaxcala, Mexico. A high-resolution magnetic prospection was carried out in three selected areas (terraces). The most important total field anomalies found on each area were inverted, obtaining results that were corroborated by archaeological excavations. This investigation demonstrates the potential of quantitative geophysical methods for the characterization of archaeological structures, in extension and in depth.

  8. Orbital driven impurity spin effect on the magnetic order of quasi-3D cupric oxide.

    PubMed

    Ganga, B G; Santhosh, P N; Nanda, B R K

    2017-04-20

    Density functional calculations are performed to study the magnetic order of the severely distorted square planar cupric oxide (CuO) and local spin disorder in it in the presence of the transition metal impurities M (=Cr, Mn, Fe, Co and Ni). The distortion in the crystal structure, arisen to reduce the band energy by minimizing the covalent interaction, creates two crisscrossing zigzag spin-1/2 chains. From the spin dimer analysis we find that while the spin chain along [Formula: see text] has strong Heisenberg type antiferromagnetic coupling (J ~ 127 meV), along [Formula: see text] it exhibits weak, but robust, ferromagnetic coupling (J ~ 9 meV) mediated by reminiscent p-d covalent interactions. The impurity effect on the magnetic ordering is independent of M and purely orbital driven. If the given spin-state of M is such that the [Formula: see text] orbital is spin-polarized, then the original long-range ordering is maintained. However, if [Formula: see text] orbital is unoccupied, the absence of corresponding covalent interaction breaks the weak ferromagnetic coupling and a spin-flip takes place at the impurity site leading to breakdown of the long range magnetic ordering.

  9. The Effect of Dissipation Mechanism on X-line Spreading in 3D Magnetic

    NASA Astrophysics Data System (ADS)

    Shepherd, L. S.; Cassak, P.; Phan, T.; Shay, M. A.; Gosling, J. T.

    2012-12-01

    Naturally occurring magnetic reconnection generally begins in a spatially localized region and spreads in the direction perpendicular to the reconnection plane as time progresses. Reconnection spreading is associated with dawn-dusk asymmetries during substorms in the magnetotail and has been observed in two-ribbon flares (such as the Bastille Day flare) and laboratory experiments at the Versatile Toroidal Facility (VTF) and the Magnetic Reconnection eXperiment (MRX). It was suggested that X-line spreading is necessary to explain the existence of X-lines extending more than 390 Earth radii (Phan et al., Nature, 404, 848, 2006). Previous numerical studies exploring the spreading of localized magnetic reconnection exclusively addressed collisionless (Hall) reconnection. Here, we address the effect of dissipation mechanism has on X-line spreading with and without a guide field. We compare previous results with simulations using three alternate phases of reconnection - Sweet-Parker reconnection, collisional reconnection with secondary islands, and reconnection with anomalous resistivity. We present results from three-dimensional resistive magnetohydrodynamic numerical simulations to address the nature of X-line spreading. Applications to reconnection in the solar wind and corona will be discussed.

  10. Tunable electronic and magnetic properties in stanene by 3d transition metal atoms absorption

    NASA Astrophysics Data System (ADS)

    Xing, Dan-Xu; Ren, Ceng-Ceng; Zhang, Shu-Feng; Feng, Yong; Chen, Xin-Lian; Zhang, Chang-Wen; Wang, Pei-Ji

    2017-03-01

    The electronic and magnetic properties of transition metal (TM) atoms (V, Cr, Mn, Fe, Co, Ni) adsorption on stanene are investigated by first-principles calculations. The results indicate that the TM atoms prefer to be relaxed on a H site on stanene except V atom which lies on the valley site. Fe-absorbed stanene is a spin gapless semiconductor with up-spin electron and down-spin hole carriers allowing the coexistence of charge current and the pure spin current. Co-absorbed stanene lies in the half metal phase. The V-, Cr-, Mn-, and Cu-absorbed stanene turn the stanene into metal, while Ni- and Zn-absorbed stanene open a narrow band gap. For V-, Cr-, Mn-, Fe-, and Co-absorbed stanene, the magnetic moment of the TM will survive while the Ni-, Cu-, and Zn-absorbed stanene will be non-magnetic material. These findings may have great potential in the design of new electrically controllable spintronic devices.

  11. 3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing (relativistic) jets and shocks, e.g., supernova remnants, active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the .shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations which show particle acceleration in jets.

  12. Registration and real-time visualization of transcranial magnetic stimulation with 3-D MR images.

    PubMed

    Noirhomme, Quentin; Ferrant, Matthieu; Vandermeeren, Yves; Olivier, Etienne; Macq, Benoît; Cuisenaire, Olivier

    2004-11-01

    This paper describes a method for registering and visualizing in real-time the results of transcranial magnetic stimulations (TMS) in physical space on the corresponding anatomical locations in MR images of the brain. The method proceeds in three main steps. First, the patient scalp is digitized in physical space with a magnetic-field digitizer, following a specific digitization pattern. Second, a registration process minimizes the mean square distance between those points and a segmented scalp surface extracted from the magnetic resonance image. Following this registration, the physician can follow the change in coil position in real-time through the visualization interface and adjust the coil position to the desired anatomical location. Third, amplitude of motor evoked potentials can be projected onto the segmented brain in order to create functional brain maps. The registration has subpixel accuracy in a study with simulated data, while we obtain a point to surface root-mean-square error of 1.17+/-0.38 mm in a 24 subject study.

  13. Integration of 3D 1H-magnetic resonance spectroscopy data into neuronavigation systems for tumor biopsies

    NASA Astrophysics Data System (ADS)

    Kanberoglu, Berkay; Moore, Nina Z.; Frakes, David; Karam, Lina J.; Debbins, Josef P.; Preul, Mark C.

    2013-03-01

    Many important applications in clinical medicine can benefit from the fusion of spectroscopy data with anatomical images. For example, the correlation of metabolite profiles with specific regions of interest in anatomical tumor images can be useful in characterizing and treating heterogeneous tumors that appear structurally homogeneous. Such applications can build on the correlation of data from in-vivo Proton Magnetic Resonance Spectroscopy Imaging (1HMRSI) with data from genetic and ex-vivo Nuclear Magnetic Resonance spectroscopy. To establish that correlation, tissue samples must be neurosurgically extracted from specifically identified locations with high accuracy. Toward that end, this paper presents new neuronavigation technology that enhances current clinical capabilities in the context of neurosurgical planning and execution. The proposed methods improve upon the current state-of-the-art in neuronavigation through the use of detailed three dimensional (3D) 1H-MRSI data. MRSI spectra are processed and analyzed, and specific voxels are selected based on their chemical contents. 3D neuronavigation overlays are then generated and applied to anatomical image data in the operating room. Without such technology, neurosurgeons must rely on memory and other qualitative resources alone for guidance in accessing specific MRSI-identified voxels. In contrast, MRSI-based overlays provide quantitative visual cues and location information during neurosurgery. The proposed methods enable a progressive new form of online MRSI-guided neuronavigation that we demonstrate in this study through phantom validation and clinical application.

  14. Self-assembly of a 3d-5f trinuclear single-molecule magnet from a pentavalent uranyl complex.

    PubMed

    Chatelain, Lucile; Walsh, James P S; Pécaut, Jacques; Tuna, Floriana; Mazzanti, Marinella

    2014-12-01

    Mixed-metal uranium compounds are very attractive candidates in the design of single-molecule magnets (SMMs), but only one 3d-5f hetero-polymetallic SMM containing a uranium center is known. Herein, we report two trimeric heterodimetallic 3d-5f complexes self-assembled by cation-cation interactions between a uranyl(V) complex and a TPA-capped M(II)  complex (M=Mn (1), Cd (2); TPA=tris(2-pyridylmethyl)amine). The metal centers were strategically chosen to promote the formation of discrete molecules rather than extended chains. Compound 1, which contains an almost linear {MnOUOMn} core, exhibits SMM behavior with a relaxation barrier of 81±0.5 K-the highest reported for a mono-uranium system-arising from intramolecular Mn-U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. Compound 1 also exhibits an open magnetic hysteresis loop at temperatures less than 3 K, with a significant coercive field of 1.9 T at 1.8 K.

  15. Inverse magnetic catalysis in bottom-up holographic QCD

    NASA Astrophysics Data System (ADS)

    Evans, Nick; Miller, Carlisson; Scott, Marc

    2016-10-01

    We explore the effect of magnetic field on chiral condensation in QCD via a simple bottom-up holographic model which inputs QCD dynamics through the running of the anomalous dimension of the quark bilinear. Bottom-up holography is a form of effective field theory and we use it to explore the dependence on the coefficients of the two lowest order terms linking the magnetic field and the quark condensate. In the massless theory, we identify a region of parameter space where magnetic catalysis occurs at zero temperature but inverse magnetic catalysis at temperatures of order the thermal phase transition. The model shows similar nonmonotonic behavior in the condensate with B at intermediate T as the lattice data. This behavior is due to the separation of the transition at which a thermal width develops for the mesons and the chiral transition in the holographic framework. The introduction of quark mass raises the scale of B where inverse catalysis takes over from catalysis until the inverse catalysis lies outside the regime of validity of the effective description leaving just catalysis.

  16. Volume estimation of rift-related magmatic features using seismic interpretation and 3D inversion of gravity data on the Guinea Plateau, West Africa

    NASA Astrophysics Data System (ADS)

    Kardell, Dominik A.

    The two end-member concept of mantle plume-driven versus far field stress-driven continental rifting anticipates high volumes of magma emplaced close to the rift-initiating plume, whereas relatively low magmatic volumes are predicted at large distances from the plume where the rifting is thought to be driven by far field stresses. We test this concept at the Guinea Plateau, which represents the last area of separation between Africa and South America, by investigating for rift-related volumes of magmatism using borehole, 3D seismic, and gravity data to run structural 3D inversions in two different data areas. Despite our interpretation of igneous rocks spanning large areas of continental shelf covered by the available seismic surveys, the calculated volumes in the Guinea Plateau barely match the magmatic volumes of other magma-poor margins and thus endorse the aforementioned concept. While the volcanic units on the shelf seem to be characterized more dominantly by horizontally deposited extrusive volcanic flows distributed over larger areas, numerous paleo-seamounts pierce complexly deformed pre and syn-rift sedimentary units on the slope. As non-uniqueness is an omnipresent issue when using potential field data to model geologic features, our method faced some challenges in the areas exhibiting complicated geology. In this situation less rigid constraints were applied in the modeling process. The misfit issues were successfully addressed by filtering the frequency content of the gravity data according to the depth of the investigated geology. In this work, we classify and compare our volume estimates for rift-related magmatism between the Guinea Fracture Zone (FZ) and the Saint Paul's FZ while presenting the refinements applied to our modeling technique.

  17. 3-D Modelling of Stretched Solitary Waves along Magnetic Field Lines

    NASA Astrophysics Data System (ADS)

    Muschietti, L.; Roth, I.; Carlson, C. W.; Berthomier, M.

    2001-12-01

    A model is presented for a new type of fast solitary waves which is observed by FAST in downward current regions of the auroral zone. The three-dimensional, coherent structures are electrostatic, have a positive potential, and move along the ambient magnetic field lines with speeds on the order of the electron drift. Their potential profile in the parallel direction, which can be directly measured, is flat-top whereby it cannot fit to the Gaussian shape used in previous work. Their potential profile in the perpendicular direction can only be inferred from a measured unipolar electric signal. We develop an extended BGK model which includes a flattened potential and an assumed cylindrical symmetry around a centric magnetic field line. The model envisions concentric shells of trapped electrons slowly drifting azimuthally while bouncing back and forth in the parallel direction. The electron dynamics is analysed in terms of three basic motions that occur on different time scales. These are defined by the cyclotron frequency Ω e, the bounce frequency ω b, and the azimuthal drift frequency ω γ , for which explicit analytical expressions are obtained. Subject to the ordering ω γ <<ωb<< Ωe, we calculate self-consistent distribution functions in terms of approximate constants of motion. Constraints on the parameters characterizing the amplitude and shape of the stretched solitary wave are discussed.

  18. Mitigation of Alfvenic activity by 3D magnetic perturbations on NSTX

    SciTech Connect

    Kramer, G. J.; Bortolon, A.; Ferraro, N. M.; Spong, D. A.; Crocker, N. A.; Darrow, D. S.; Fredrickson, E. D.; Kubota, S.; Park, J. -K.; Podesta, M.; Heidbrink, W. W.

    2016-07-05

    Observations on the National Spherical Torus eXperiment (NSTX) indicate that externally applied non-axisymmetric magnetic perturbations (MP) can reduce the amplitude of Toroidal Alfven Eigenmodes (TAE) and Global Alfven Eigenmodes (GAE) in response to pulsed n=3 non-resonant fields. From full-orbit following Monte Carlo simulations with the 1- and 2-fluid resistive MHD plasma response to the magnetic perturbation included, it was found that in response to MP pulses the fast-ion losses increased and the fast-ion drive for the GAEs was reduced. The MP did not affect the fast-ion drive for the TAEs significantly but the Alfven continuum at the plasma edge was found to be altered due to the toroidal symmetry breaking which leads to coupling of different toroidal harmonics. The TAE gap was reduced at the edge creating enhanced continuum damping of the global TAEs, which is consistent with the observations. Furthermore, the results suggest that optimized non-axisymmetric MP might be exploited to control and mitigate Alfven instabilities by tailoring the fast-ion distribution function and/or continuum structure.

  19. Mitigation of Alfvenic activity by 3D magnetic perturbations on NSTX

    DOE PAGES

    Kramer, G. J.; Bortolon, A.; Ferraro, N. M.; ...

    2016-07-05

    Observations on the National Spherical Torus eXperiment (NSTX) indicate that externally applied non-axisymmetric magnetic perturbations (MP) can reduce the amplitude of Toroidal Alfven Eigenmodes (TAE) and Global Alfven Eigenmodes (GAE) in response to pulsed n=3 non-resonant fields. From full-orbit following Monte Carlo simulations with the 1- and 2-fluid resistive MHD plasma response to the magnetic perturbation included, it was found that in response to MP pulses the fast-ion losses increased and the fast-ion drive for the GAEs was reduced. The MP did not affect the fast-ion drive for the TAEs significantly but the Alfven continuum at the plasma edge wasmore » found to be altered due to the toroidal symmetry breaking which leads to coupling of different toroidal harmonics. The TAE gap was reduced at the edge creating enhanced continuum damping of the global TAEs, which is consistent with the observations. Furthermore, the results suggest that optimized non-axisymmetric MP might be exploited to control and mitigate Alfven instabilities by tailoring the fast-ion distribution function and/or continuum structure.« less

  20. Mitigation of Alfvénic activity by 3D magnetic perturbations on NSTX

    NASA Astrophysics Data System (ADS)

    Kramer, G. J.; Bortolon, A.; Ferraro, N. M.; Spong, D. A.; Crocker, N. A.; Darrow, D. S.; Fredrickson, E. D.; Kubota, S.; Park, J.-K.; Podestà, M.; Heidbrink, W. W.; the NSTX Team

    2016-08-01

    Observations on the National Spherical Torus Experiment (NSTX) indicate that externally applied non-axisymmetric magnetic perturbations (MP) can reduce the amplitude of toroidal Alfvén eigenmodes (TAE) and global Alfvén eigenmodes (GAE) in response to pulsed n  =  3 non-resonant fields. From full-orbit following Monte Carlo simulations with the one- and two-fluid resistive MHD plasma response to the magnetic perturbation included, it was found that in response to MP pulses the fast-ion losses increased and the fast-ion drive for the GAEs was reduced. The MP did not affect the fast-ion drive for the TAEs significantly but the Alfvén continuum at the plasma edge was found to be altered due to the toroidal symmetry breaking which leads to coupling of different toroidal harmonics. The TAE gap was reduced at the edge creating enhanced continuum damping of the global TAEs, which is consistent with the observations. The results suggest that optimized non-axisymmetric MP might be exploited to control and mitigate Alfvén instabilities by tailoring the fast-ion distribution function and/or continuum structure.

  1. 3D Magnetically Ordered Open Supramolecular Architectures Based on Ferrimagnetic Cu/Adenine/Hydroxide Heptameric Wheels.

    PubMed

    Pérez-Aguirre, Rubén; Beobide, Garikoitz; Castillo, Oscar; de Pedro, Imanol; Luque, Antonio; Pérez-Yáñez, Sonia; Rodríguez Fernández, Jesús; Román, Pascual

    2016-08-01

    The present work provides two new examples of supramolecular metal-organic frameworks consisting of three-dimensional extended noncovalent assemblies of wheel-shaped heptanuclear [Cu7(μ-H2O)6(μ3-OH)6(μ-adeninato-κN3:κN9)6](2+) entities. The heptanuclear entity consists of a central [Cu(OH)6](4-) core connected to six additional copper(II) metal centers in a radial and planar arrangement through the hydroxides. It generates a wheel-shaped entity in which water molecules and μ-κN3:κN9 adeninato ligands bridge the peripheral copper atoms. The magnetic characterization indicates the central copper(II) center is anti-ferromagnetically coupled to external copper(II) centers, which are ferromagnetically coupled among them leading to an S = 5/2 ground state. The packing of these entities is sustained by π-π stacking interactions between the adenine nucleobases and by hydrogen bonds established among the hydroxide ligands, sulfate anions, and adenine nucleobases. The sum of both types of supramolecular interactions creates a rigid synthon that in combination with the rigidity of the heptameric entity generates an open supramolecular structure (40-50% of available space) in which additional sulfate and triethylammonium ions are located altogether with solvent molecules. These compounds represent an interesting example of materials combining both porosity and magnetic relevant features.

  2. Modelling of plasma response to 3D external magnetic field perturbations in EAST

    NASA Astrophysics Data System (ADS)

    Yang, Xu; Sun, Youwen; Liu, Yueqiang; Gu, Shuai; Liu, Yue; Wang, Huihui; Zhou, Lina; Guo, Wenfeng

    2016-11-01

    Sustained mitigation and/or suppression of type-I edge localized modes (ELMs) has been achieved in EAST high-confinement plasmas, utilizing the resonant magnetic perturbation (RMP) fields produced by two rows of magnetic coils located just inside the vacuum vessel. Systematic toroidal modelling of the plasma response to these RMP fields with various coil configurations (with dominant toroidal mode number n  = 1, 2, 3, 4) in EAST is, for the first time, carried out by using the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), with results reported here. In particular, the plasma response is computed with varying coil phasing (the toroidal phase difference of the coil currents) between the upper and lower rows of coils, from 0 to 360°. Four figures of merit, constructed based on the MARS-F computations, are used to determine the optimal coil phasing. The modelled results, taking into account the plasma response, agree well with the experimental observations in terms of the coil phasing for both the mitigated and the suppressed ELM cases in EAST experiments. This study provides a crucial confirmation of the role of the plasma edge peeling response in ELM control, complementing similar studies carried out for other tokamak devices.

  3. Localization and propagation of the energy release during 3D kinetic magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Lapenta, Giovanni; Markidis, Stefano; Goldman, Marty; Newman, David

    2013-04-01

    Reconnection is a key processes where energy is released: magnetic field lines break, merge in a new configuration. In the process some of the energy is released. Recent work by Shay and collaborators has pointed out that energy is released far and moving fast away from the reconnection site, at a speed exceeding several times the Alfven speed. We revisit this point, considering the release of energy from reconnection and considering both laminar processes and turbulent reconnection. We analyse the energy budget and the processes of energy transfer via Poynting flux and particle flows. The results are compared with the recent findings by Shay. The effect of the guide field can be very significant at even relatively weak strength, as our recent analysis shows. The effect on the life cycle of energy is considered. The research leading to these results has received funding from the European Commission's Seventh Framework Programme (FP7/2007-2013) under the grant agreement SWIFF (project n° 263340, www.swiff.eu). [1] M. A. Shay, J. F. Drake, J. P. Eastwood, and T. D. Phan, Super-Alfvénic Propagation of Substorm Reconnection Signatures and Poynting Flux, Phys. Rev. Lett. 107, 089901, 2011. [2] M.V. Goldman, G. Lapenta, D. L. Newman, S. Markidis, H. Che, Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection, Physical Review Letters, 107, 135001, 2011.

  4. 3D calculations of the Superconducting Super Collider (SSC) 3 Tesla magnet

    SciTech Connect

    Lari, R.J.

    1984-01-01

    A 20 TeV Superconducting Super Collider (SSC) proton accelerator is being proposed by the High Energy Physics Community. One proposal would consist of a ring of magnets 164 km in circumference with a field strength of 3 Tesla and would cost 2.7 billion dollars. The magnet consists of stacked steel laminations with superconducting coils. The desired field uniformity is obtained for all fields from 0.2 to 3 Tesla by using three (or more) different pole shapes. These three different laminations are stacked in the order 1-2-3-1-2-3-... creating a truly three dimensional geometry. A three laminated stack 1-2-3 with periodic boundary conditions at 1 and 3 was assigned about 5000 finite elements per lamination and solved using the computer program TOSCA. To check the TOSCA results, the field of each of the three different shaped laminations was calculated separately using periodic boundary conditions and compared to the two dimensional field calculations using TRIM. This was done for a constant permeability of 2000 and using the B-H table for fully annealed 1010 steel. The difference of the field calculations in the region of interest was always less than +-.2%

  5. 3D imaging of magnetic particles using the 7-channel magnetoencephalography device without pre-magnetization or displacement of the sample

    NASA Astrophysics Data System (ADS)

    Polikarpov, M. A.; Ustinin, M. N.; Rykunov, S. D.; Yurenya, A. Y.; Naurzakov, S. P.; Grebenkin, A. P.; Panchenko, V. Y.

    2017-04-01

    SQUID-based magnetoencephalography device was used for the measurement of a magnetic noise generated by ferrofluid in the stationary standing vial. It was found that a free surface of the ferrofluid generates spontaneous magnetic field sufficient to detect the presence of nanoparticles in the experimental setup. The spatial distribution of elementary magnetic sources was reconstructed by the frequency-pattern analysis of multichannel time series. The localization of ferrofluids was performed based on the analysis of quasirandom time series in two cases of oscillation source. One of them was infrasound from outer noise, and another one was the human heartbeat. These results are prospective for 3D imaging of magnetic particles without pre-magnetization.

  6. Computation of load performance and other parameters of extra high speed modified Lundell alternators from 3D-FE magnetic field solutions

    NASA Technical Reports Server (NTRS)

    Wang, R.; Demerdash, N. A.

    1992-01-01

    The combined magnetic vector potential - magnetic scalar potential method of computation of 3D magnetic fields by finite elements, introduced in a companion paper, in combination with state modeling in the abc-frame of reference, are used for global 3D magnetic field analysis and machine performance computation under rated load and overload condition in an example 14.3 kVA modified Lundell alternator. The results vividly demonstrate the 3D nature of the magnetic field in such machines, and show how this model can be used as an excellent tool for computation of flux density distributions, armature current and voltage waveform profiles and harmonic contents, as well as computation of torque profiles and ripples. Use of the model in gaining insight into locations of regions in the magnetic circuit with heavy degrees of saturation is demonstrated. Experimental results which correlate well with the simulations of the load case are given.

  7. Protecting ITER walls: fast ion power loads in 3D magnetic field

    NASA Astrophysics Data System (ADS)

    Kurki-Suonio, T.; Särkimäki, K.; Äkäslompolo, S.; Varje, J.; Liu, Y.; Sipilä, S.; Asunta, O.; Hirvijoki, E.; Snicker, A.; Terävä, J.; Cavinato, M.; Gagliardi, M.; Parail, V.; Saibene, G.

    2017-01-01

    The fusion alpha and beam ion with steady-state power loads in all four main operating scenarios of ITER have been evaluated by the ASCOT code. For this purpose, high-fidelity magnetic backgrounds were reconstructed, taking into account even the internal structure of the ferritic inserts and tritium breeding modules (TBM). The beam ions were found to be almost perfectly confined in all scenarios, and only the so-called hybrid scenario featured alpha loads reaching 0.5 MW due to its more triangular plasma. The TBMs were not found to jeopardize the alpha confinement, nor cause any hot spots. Including plasma response did not bring dramatic changes to the load. The ELM control coils (ECC) were simulated in the baseline scenario and found to seriously deteriorate even the beam confinement. However, the edge perturbation in this case is so large that the sources have to be re-evaluated with plasma profiles that take into account the ECC perturbation.

  8. Development of 3-D magnetic nano-arrays by electrodeposition into mesoporous silica.

    SciTech Connect

    Campbell, R.; Manning, J.; Bakker, M.G.; Li, X.; Lee, D.R.; Wang, J.; X-Ray Science Division; Univ. of Alabama

    2006-01-01

    The development of periodic nanostructures fabricated by self-assembly of surfactants and block co-polymers has opened up the possibility of generating periodic magnetic nanostructures of types not accessible by self-assembly of nano-particles. The fabrication of mesoporous silica thin films around self-assembled block co-polymers is well established. Common structures for such films are SBA-15 which consists of hexagonal arrays of cylindrical pores and SBA-16 which has face centered arrays of spherical voids. These pores are connected by 1-2 nm thick flaws in the continuous silica phase producing an effectively continuous porous phase. After removal of the block co-polymer template, electrodeposition into the mesoporous silica thin films produces arrays of 5-10 nm diameter nano-wires and nano-particles. We have demonstrated that such materials can be fabricated on a wide range of metal substrates. Characterization by Scanning Electron Microscopies shows that the mesoporous silica is well ordered over micron scale areas. Grazing Incidence Small Angle X-ray Scattering (GISAXS) studies shows diffraction spots, consistent with the entire film being well ordered. GISAXS also shows that the mesoporous silica films survive removal of the template and electrodeposition of nickel and cobalt into the mesoporous silica films. Such films are of interest for their magnetic properties, as the nanophase and scale can be independently varied. Further, the presence of nanowires inside an insulator suggests that these films might also be of interest as the current confining element for Confined Current Path-Current Perpendicular to Plane GMR sensors.

  9. 3D magnetic resonance imaging as a non-invasive tool for investigating water-filled karst formations

    NASA Astrophysics Data System (ADS)

    Legchenko, A.; Ezersky, M.; Boucher, M.; Chevalier, A.; Vouillamoz, J.-M.

    2012-04-01

    Magnetic Resonance Sounding (MRS) is a geophysical technique developed for groundwater exploration. MRS can be used for reliable identification of karst aquifers because of the relaxation time of the magnetic resonance signal (T1) is longer for bulk water in karst caverns and channels (about 2 s) than for water in porous rock (few tens of ms). MRS is sensitive primary to groundwater volume but electrically conductive layers modify electromagnetic fields in the subsurface and thus may have an effect on MRS performance. Generally, the study of a karst requires a 3D field set-up and we developed a measuring procedure and interpretation software that makes it possible to image heterogeneous water-bearing geological formations down to about 80 m (3D-SNMR method). Numerical modeling results show that limited resolution of the method allows only identification of large karst formations. For example detectable karst should be larger than a few hundred cubic meters when karst is located close to the surface and a few thousand cubic meters when it is located at 60 m. Time Domain Electromagnetic method (TDEM) is known as an efficient tool for investigating electrical conductivity of rocks. TDEM results allow more accurate computing of the EM field in the subsurface and thus contribute for improving accuracy of MRS results. TDEM and 3D-SNMR methods were applied jointly in the Dead Sea coast of Israel (Nahal Hever South). The subsurface in this area is heterogeneous and composed of intercalated sand and clay layers over a salt rock, which is partly karstified. Groundwater is very saline, with a chloride concentration of 100-225 g/l thus rendering the resistivity of geological formations less than 1 ohm-m. We have shown numerically that under Dead Sea coast conditions, 3D-SNMR is able to detect and to locate the target within an error of a few tens of meters. In the investigated area (500×500 m2) our results reveal a very heterogeneous shallow aquifer that could be divided into

  10. Inverse photoelectron spectrometer with magnetically focused electron gun

    NASA Technical Reports Server (NTRS)

    Krainsky, Isay L.

    1991-01-01

    An inverse photoelectron spectrometer is described which is based on the design of a magnetically focused low energy electron gun. The magnetic lens extends its field over a relatively large segment of the electron trajectory, which could provide a better focusing effect on a high-current-density low-velocity electron beam, providing the magnetic field in the vicinity of the target is reduced sufficiently to preserve the collinearity of the beam. In order to prove the concept, ray tracing is conducted using the Herrmannsfeldt program for solving electron trajectories in electrostatic and magnetostatic focusing systems. The program allows the calculation of the angles of the electron trajectories with the z axis, at the target location. The results of the ray-tracing procedure conducted for this gun are discussed. Some of the advantages of the magnetic focusing are also discussed.

  11. Magnetic field of Jupiter: A generalized inverse approach

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.

    1981-01-01

    The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model nonuniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.

  12. Inverse cascade of magnetic helicity in magnetohydrodynamic turbulence.

    PubMed

    Müller, Wolf-Christian; Malapaka, Shiva Kumar; Busse, Angela

    2012-01-01

    The nonlinear dynamics of magnetic helicity HM, which is responsible for large-scale magnetic structure formation in electrically conducting turbulent media, is investigated in forced and decaying three-dimensional magnetohydrodynamic turbulence. This is done with the help of high-resolution direct numerical simulations and statistical closure theory. The numerically observed spectral scaling of HM is at variance with earlier work using a statistical closure model [Pouquet et al., J. Fluid Mech. 77, 321 (1976)]. By revisiting this theory, a universal dynamical balance relation is found that includes the effects of kinetic helicity as well as kinetic and magnetic energies on the inverse cascade of HM and explains the above-mentioned discrepancy. Consideration of the result in the context of mean-field dynamo theory suggests a nonlinear modification of the α-dynamo effect, which is important in the context of magnetic-field excitation in turbulent plasmas.

  13. Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging1[OPEN

    PubMed Central

    Kochs, Johannes; Pflugfelder, Daniel

    2016-01-01

    Precise measurements of root system architecture traits are an important requirement for plant phenotyping. Most of the current methods for analyzing root growth require either artificial growing conditions (e.g. hydroponics), are severely restricted in the fraction of roots detectable (e.g. rhizotrons), or are destructive (e.g. soil coring). On the other hand, modalities such as magnetic resonance imaging (MRI) are noninvasive and allow high-quality three-dimensional imaging of roots in soil. Here, we present a plant root imaging and analysis pipeline using MRI together with an advanced image visualization and analysis software toolbox named NMRooting. Pots up to 117 mm in diameter and 800 mm in height can be measured with the 4.7 T MRI instrument used here. For 1.5 l pots (81 mm diameter, 300 mm high), a fully automated system was developed enabling measurement of up to 18 pots per day. The most important root traits that can be nondestructively monitored over time are root mass, length, diameter, tip number, and growth angles (in two-dimensional polar coordinates) and spatial distribution. Various validation measurements for these traits were performed, showing that roots down to a diameter range between 200 μm and 300 μm can be quantitatively measured. Root fresh weight correlates linearly with root mass determined by MRI. We demonstrate the capabilities of MRI and the dedicated imaging pipeline in experimental series performed on soil-grown maize (Zea mays) and barley (Hordeum vulgare) plants. PMID:26729797

  14. Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging.

    PubMed

    van Dusschoten, Dagmar; Metzner, Ralf; Kochs, Johannes; Postma, Johannes A; Pflugfelder, Daniel; Bühler, Jonas; Schurr, Ulrich; Jahnke, Siegfried

    2016-03-01

    Precise measurements of root system architecture traits are an important requirement for plant phenotyping. Most of the current methods for analyzing root growth require either artificial growing conditions (e.g. hydroponics), are severely restricted in the fraction of roots detectable (e.g. rhizotrons), or are destructive (e.g. soil coring). On the other hand, modalities such as magnetic resonance imaging (MRI) are noninvasive and allow high-quality three-dimensional imaging of roots in soil. Here, we present a plant root imaging and analysis pipeline using MRI together with an advanced image visualization and analysis software toolbox named NMRooting. Pots up to 117 mm in diameter and 800 mm in height can be measured with the 4.7 T MRI instrument used here. For 1.5 l pots (81 mm diameter, 300 mm high), a fully automated system was developed enabling measurement of up to 18 pots per day. The most important root traits that can be nondestructively monitored over time are root mass, length, diameter, tip number, and growth angles (in two-dimensional polar coordinates) and spatial distribution. Various validation measurements for these traits were performed, showing that roots down to a diameter range between 200 μm and 300 μm can be quantitatively measured. Root fresh weight correlates linearly with root mass determined by MRI. We demonstrate the capabilities of MRI and the dedicated imaging pipeline in experimental series performed on soil-grown maize (Zea mays) and barley (Hordeum vulgare) plants.

  15. 3-D multiobservable probabilistic inversion for the compositional and thermal structure of the lithosphere and upper mantle: III. Thermochemical tomography in the Western-Central U.S.

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Rawlinson, Nicholas; Yang, Yingjie; Schutt, Derek L.; Jones, Alan G.; Fullea, Javier; Griffin, William L.

    2016-10-01

    We apply a novel 3-D multiobservable probabilistic tomography method that we have recently developed and benchmarked, to directly image the thermochemical structure of the Colorado Plateau and surrounding areas by jointly inverting P wave and S wave teleseismic arrival times, Rayleigh wave dispersion data, Bouguer anomalies, satellite-derived gravity gradients, geoid height, absolute (local and dynamic) elevation, and surface heat flow data. The temperature and compositional structures recovered by our inversion reveal a high level of correlation between recent basaltic magmatism and zones of high temperature and low Mg# (i.e., refertilized mantle) in the lithosphere, consistent with independent geochemical data. However, the lithospheric mantle is overall characterized by a highly heterogeneous thermochemical structure, with only some features correlating well with either Proterozoic and/or Cenozoic crustal structures. This suggests that most of the present-day deep lithospheric architecture reflects the superposition of numerous geodynamic events of different scale and nature to those that created major crustal structures. This is consistent with the complex lithosphere-asthenosphere system that we image, which exhibits a variety of multiscale feedback mechanisms (e.g., small-scale convection, magmatic intrusion, delamination, etc.) driving surface processes. Our results also suggest that most of the present-day elevation in the Colorado Plateau and surrounding regions is the result of thermochemical buoyancy sources within the lithosphere, with dynamic effects (from sublithospheric mantle flow) contributing only locally up to ˜15-35%.

  16. Interactive 3D segmentation of the prostate in magnetic resonance images using shape and local appearance similarity analysis

    NASA Astrophysics Data System (ADS)

    Shahedi, Maysam; Fenster, Aaron; Cool, Derek W.; Romagnoli, Cesare; Ward, Aaron D.

    2013-03-01

    3D segmentation of the prostate in medical images is useful to prostate cancer diagnosis and therapy guidance, but is time-consuming to perform manually. Clinical translation of computer-assisted segmentation algorithms for this purpose requires a comprehensive and complementary set of evaluation metrics that are informative to the clinical end user. We have developed an interactive 3D prostate segmentation method for 1.5T and 3.0T T2-weighted magnetic resonance imaging (T2W MRI) acquired using an endorectal coil. We evaluated our method against manual segmentations of 36 3D images using complementary boundary-based (mean absolute distance; MAD), regional overlap (Dice similarity coefficient; DSC) and volume difference (ΔV) metrics. Our technique is based on inter-subject prostate shape and local boundary appearance similarity. In the training phase, we calculated a point distribution model (PDM) and a set of local mean intensity patches centered on the prostate border to capture shape and appearance variability. To segment an unseen image, we defined a set of rays - one corresponding to each of the mean intensity patches computed in training - emanating from the prostate centre. We used a radial-based search strategy and translated each mean intensity patch along its corresponding ray, selecting as a candidate the boundary point with the highest normalized cross correlation along each ray. These boundary points were then regularized using the PDM. For the whole gland, we measured a mean+/-std MAD of 2.5+/-0.7 mm, DSC of 80+/-4%, and ΔV of 1.1+/-8.8 cc. We also provided an anatomic breakdown of these metrics within the prostatic base, mid-gland, and apex.

  17. Source inversion analysis of the 2011 Tohoku-Oki earthquake using Green's functions calculated from a 3-D heterogeneous structure model

    NASA Astrophysics Data System (ADS)

    Suzuki, W.; Aoi, S.; Maeda, T.; Sekiguchi, H.; Kunugi, T.

    2013-12-01

    Source inversion analysis using near-source strong-motion records with an assumption of 1-D underground structure models has revealed the overall characteristics of the rupture process of the 2011 Tohoku-Oki mega-thrust earthquake. This assumption for the structure model is acceptable because the seismic waves radiated during the Tohoku-Oki event were rich in the very-low-frequency contents lower than 0.05 Hz, which are less affected by the small-scale heterogeneous structure. The analysis using more reliable Green's functions even in the higher-frequency range considering complex structure of the subduction zone will illuminate more detailed rupture process in space and time and the transition of the frequency dependence of the wave radiation for the Tohoku-Oki earthquake. In this study, we calculate the near-source Green's functions using a 3-D underground structure model and perform the source inversion analysis using them. The 3-D underground structure model used in this study is the Japan Integrated Velocity Structure Model (Headquarters for Earthquake Research Promotion, 2012). A curved fault model on the Pacific plate interface is discretized into 287 subfaults at ~20 km interval. The Green's functions are calculated using GMS (Aoi et al., 2004), which is a simulation program package for the seismic wave field by the finite difference method using discontinuous grids (Aoi and Fujiwara, 1999). Computational region is 136-146.2E in longitude, 34-41.6N in latitude, and 0-100 km in depth. The horizontal and vertical grid intervals are 200 m and 100 m, respectively, for the shallower region and those for the deeper region are tripled. The number of the total grids is 2.1 billion. We derive 300-s records by calculating 36,000 steps with a time interval of 0.0083 second (120 Hz sampling). It takes nearly one hour to compute one case using 48 Graphics Processing Units (GPU) on TSUBAME2.0 supercomputer owned by Tokyo Institute of Technology. In total, 574 cases are

  18. 3-D laser confocal microscopy study of the oxidation of NdFeB magnets in atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Meakin, J. P.; Speight, J. D.; Sheridan, R. S.; Bradshaw, A.; Harris, I. R.; Williams, A. J.; Walton, A.

    2016-08-01

    Neodymium iron boron (NdFeB) magnets are used in a number of important applications, such as generators in gearless wind turbines, motors in electric vehicles and electronic goods (e.g.- computer hard disk drives, HDD). Hydrogen can be used as a processing gas to separate and recycle scrap sintered Nd-Fe-B magnets from end-of-life products to form a powder suitable for recycling. However, the magnets are likely to have been exposed to atmospheric conditions prior to processing, and any oxidation could lead to activation problems for the hydrogen decrepitation reaction. Many previous studies on the oxidation of NdFeB magnets have been performed at elevated temperatures; however, few studies have been formed under atmospheric conditions. In this paper a combination of 3-D laser confocal microscopy and Raman spectroscopy have been used to assess the composition, morphology and rate of oxidation/corrosion on scrap sintered NdFeB magnets. Confocal microscopy has been employed to measure the growth of surface reaction products at room temperature, immediately after exposure to air. The results showed that there was a significant height increase at the triple junctions of the Nd-rich grain boundaries. Using Raman spectroscopy, the product was shown to consist of Nd2O3 and formed only on the Nd-rich triple junctions. The diffusion coefficient of the triple junction reaction product growth at 20 °C was determined to be approximately 4 × 10-13 cm2/sec. This value is several orders of magnitude larger than values derived from the diffusion controlled oxide growth observations at elevated temperatures in the literature. This indicates that the growth of the room temperature oxidation products are likely defect enhanced processes at the NdFeB triple junctions.

  19. 3D PIC Simulations of Collisionless Shocks at Lunar Magnetic Anomalies and Their Role in Forming Lunar Swirls

    NASA Astrophysics Data System (ADS)

    Bamford, R. A.; Alves, E. P.; Cruz, F.; Kellett, B. J.; Fonseca, R. A.; Silva, L. O.; Trines, R. M. G. M.; Halekas, J. S.; Kramer, G.; Harnett, E.; Cairns, R. A.; Bingham, R.

    2016-10-01

    Investigation of the lunar crustal magnetic anomalies offers a comprehensive long-term data set of observations of small-scale magnetic fields and their interaction with the solar wind. In this paper a review of the observations of lunar mini-magnetospheres is compared quantifiably with theoretical kinetic-scale plasma physics and 3D particle-in-cell simulations. The aim of this paper is to provide a complete picture of all the aspects of the phenomena and to show how the observations from all the different and international missions interrelate. The analysis shows that the simulations are consistent with the formation of miniature (smaller than the ion Larmor orbit) collisionless shocks and miniature magnetospheric cavities, which has not been demonstrated previously. The simulations reproduce the finesse and form of the differential proton patterns that are believed to be responsible for the creation of both the “lunar swirls” and “dark lanes.” Using a mature plasma physics code like OSIRIS allows us, for the first time, to make a side-by-side comparison between model and space observations. This is shown for all of the key plasma parameters observed to date by spacecraft, including the spectral imaging data of the lunar swirls. The analysis of miniature magnetic structures offers insight into multi-scale mechanisms and kinetic-scale aspects of planetary magnetospheres.

  20. A series of rare earth complexes with novel non-interpenetrating 3D networks: synthesis, structures, magnetic and optical properties.

    PubMed

    Wei, Xiao-Hua; Yang, Lin-Yan; Liao, Sheng-Yun; Zhang, Ming; Tian, Jin-Lei; Du, Pei-Yao; Gu, Wen; Liu, Xin

    2014-04-21

    A series of metal-organic framework {Ln(BCPBA)(H2O)}n {Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5)}; {[Ln(BCPBA)(H2O)](H2O)}n {Ln = Pr (6), Gd (7)} have been synthesized through the hydrothermal synthesis method. These compounds possess non-interpenetrating 3D networks with 10.1438 Å× 17.9149 Å rhombic channels along the [001] direction. The results of temperature-dependent magnetic susceptibility measurements indicate that compounds 4 and 7 exhibit Ln(III)Ln(III) antiferromagnetic interactions, while compound 5 exhibits Ln(III)Ln(III) ferromagnetic interactions. Frequency dependent out-of-phase signals were observed in alternating current (ac) magnetic susceptibility measurements which indicate that they have slow magnetic relaxation characteristics. The luminescent properties of 1, 2, 3, 4, and 5 are also discussed. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, compound 4 has longer fluorescence lifetime (τ1 = 400.0000 ms, τ2 = 1143.469 ms) and higher quantum yield (Φ = 42%) compared with other compounds.

  1. 3D cine magnetic resonance imaging of rat lung ARDS using gradient-modulated SWIFT with retrospective respiratory gating

    NASA Astrophysics Data System (ADS)

    Kobayashi, Naoharu; Lei, Jianxun; Utecht, Lynn; Garwood, Michael; Ingbar, David H.; Bhargava, Maneesh

    2015-03-01

    SWeep Imaging with Fourier Transformation (SWIFT) with gradient modulation and DC navigator retrospective gating is introduced as a 3D cine magnetic resonance imaging (MRI) method for the lung. In anesthetized normal rats, the quasi-simultaneous excitation and acquisition in SWIFT enabled extremely high sensitivity to the fast-decaying parenchymal signals (TE=~4 μs), which are invisible with conventional MRI techniques. Respiratory motion information was extracted from DC navigator signals and the SWIFT data were reconstructed to 3D cine images with 16 respiratory phases. To test this technique's capabilities, rats exposed to > 95% O2 for 60 hours for induction of acute respiratory distress syndrome (ARDS), were imaged and compared with normal rat lungs (N=7 and 5 for ARDS and normal groups, respectively). SWIFT images showed lung tissue density differences along the gravity direction. In the cine SWIFT images, a parenchymal signal drop at the inhalation phase was consistently observed for both normal and ARDS rats due to lung inflation (i.e. decrease of the proton density), but the drop was less for ARDS rats. Depending on the respiratory phase and lung region, the lungs from the ARDS rats showed 1-24% higher parenchymal signal intensities relative to the normal rat lungs, likely due to accumulated extravascular water (EVLW). Those results demonstrate that SWIFT has high enough sensitivity for detecting the lung proton density changes due to gravity, different phases of respiration and accumulation of EVLW in the rat ARDS lungs.

  2. 3D Cine Magnetic Resonance Imaging of Rat Lung ARDS using Gradient-modulated SWIFT with Retrospective Respiratory Gating.

    PubMed

    Kobayashi, Naoharu; Lei, Jianxun; Utecht, Lynn; Garwood, Michael; Ingbar, David; Bhargava, Maneesh

    2015-02-21

    SWeep Imaging with Fourier Transformation (SWIFT) with gradient modulation and DC navigator retrospective gating is introduced as a 3D cine magnetic resonance imaging (MRI) method for the lung. The quasi-simultaneous excitation and acquisition in SWIFT enabled extremely high sensitivity to the fast-decaying parenchymal signals (TE=~4 μs), which are invisible with conventional MRI techniques. Based on respiratory motion information extracted from DC navigator signals, the SWIFT data were reconstructed to 3D cine images with 16 respiratory phases. To test the capability of the proposed technique, rats exposed to > 95% O2 for 60 hours for induction of acute respiratory distress syndrome (ARDS), were imaged and compared with normal rat lungs (N=7 and 5 for ARDS and normal group, respectively). SWIFT images showed lung tissue density difference along the gravity direction. In the cine SWIFT images, parenchymal signal drop at the inhalation phase was consistently observed for both normal and ARDS rats due to inflation of the lung (i.e. decrease of the proton density), but the drop was less for ARDS rats. Depending on the respiration phase and lung region, the lungs from the ARDS rats showed 1-24% higher parenchymal signal intensities relative to the normal rat lungs, which would be mainly from accumulation of extravascular water (EVLW). Those results demonstrate that SWIFT has high enough sensitivity for detecting the lung proton density changes due to gravity, different respiration phases and accumulation of EVLW in the rat ARDS lungs.

  3. 3D modelling of an aero-gravity and -magnetic survey as an first exploration step in a frontier basin

    NASA Astrophysics Data System (ADS)

    Köther, Nils; Eckard, Marcel; Götze, Hans-Jürgen

    2010-05-01

    The West African Taoudeni basin covers a desert area of about 1.8 million km² and is one of the last frontier basins worldwide. Here Wintershall Holding AG holds acreage of about 68000 km². During 2005-2007 geological surveys and an aero-gravity and -magnetic survey were conducted in this area. The potential field modelling should contribute first insight about the subsurface to plan an economic seismic survey. 2D models lead to poor results. 2008 the results of an internship (NK) were 3D subsurface models, which were enhanced during the following diploma thesis (Köther, 2009). Complex igneous rocks and sparsely distributed constraints lead to an ambiguous interpretation. Therefore, several simple 3D models were compiled with the in-house software IGMAS+, which base on geological ideas of the underground and fit well the measured data. These basic models allow a geophysical evaluation of different geological theories about the subsurface. Also, for a thorough interpretation field transformations (Euler, Curvature, and Derivatives) were calculated. These results led to new constraints for further interpretation of the basin structures and therefore they are important contributions for future exploration e.g. the planning of seismic surveys.

  4. A series of novel lanthanide carboxyphosphonates with a 3D framework structure: synthesis, structure, and luminescent and magnetic properties.

    PubMed

    Chen, Kai; Dong, Da-Peng; Sun, Zhen-Gang; Jiao, Cheng-Qi; Li, Chao; Wang, Cheng-Lin; Zhu, Yan-Yu; Zhao, Yan; Zhu, Jiang; Sun, Shou-Hui; Zheng, Ming-Jing; Tian, Hui; Chu, Wei

    2012-08-28

    By introduction of 1,4-benzenedicarboxylic acid as the second organic ligand, a series of novel lanthanide carboxyphosphonates with a 3D framework structure, namely, [Ln(3)(H(2)L)(HL)(2)(bdc)(2)(H(2)O)]·7H(2)O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8); H(3)L = H(2)O(3)PCH(2)NC(5)H(9)COOH; H(2)bdc = HOOCC(6)H(4)COOH) have been synthesized under hydrothermal conditions. Compounds are isostructural and feature a 3D framework in which Ln(III) polyhedra are interconnected by bridging {CPO(3)} tetrahedra into 2D inorganic layers parallel to the ab plane. The organic groups of H(2)L(-) are grafted on the two sides of the layer. These layers are further cross-linked by the bdc(2-) ligands from one layer to the Ln atoms from the other into a pillared-layered architecture with one-dimensional channel system along the a axis. The thermal stability of compounds has been investigated. Luminescent properties of compounds , and the magnetic properties of compound have also been studied.

  5. Novel methodology for 3D reconstruction of carotid arteries and plaque characterization based upon magnetic resonance imaging carotid angiography data.

    PubMed

    Sakellarios, Antonis I; Stefanou, Kostas; Siogkas, Panagiotis; Tsakanikas, Vasilis D; Bourantas, Christos V; Athanasiou, Lambros; Exarchos, Themis P; Fotiou, Evangelos; Naka, Katerina K; Papafaklis, Michail I; Patterson, Andrew J; Young, Victoria E L; Gillard, Jonathan H; Michalis, Lampros K; Fotiadis, Dimitrios I

    2012-10-01

    In this study, we present a novel methodology that allows reliable segmentation of the magnetic resonance images (MRIs) for accurate fully automated three-dimensional (3D) reconstruction of the carotid arteries and semiautomated characterization of plaque type. Our approach uses active contours to detect the luminal borders in the time-of-flight images and the outer vessel wall borders in the T(1)-weighted images. The methodology incorporates the connecting components theory for the automated identification of the bifurcation region and a knowledge-based algorithm for the accurate characterization of the plaque components. The proposed segmentation method was validated in randomly selected MRI frames analyzed offline by two expert observers. The interobserver variability of the method for the lumen and outer vessel wall was -1.60%±6.70% and 0.56%±6.28%, respectively, while the Williams Index for all metrics was close to unity. The methodology implemented to identify the composition of the plaque was also validated in 591 images acquired from 24 patients. The obtained Cohen's k was 0.68 (0.60-0.76) for lipid plaques, while the time needed to process an MRI sequence for 3D reconstruction was only 30 s. The obtained results indicate that the proposed methodology allows reliable and automated detection of the luminal and vessel wall borders and fast and accurate characterization of plaque type in carotid MRI sequences. These features render the currently presented methodology a useful tool in the clinic