An iterative multidisciplinary analysis for rotor blade shape determination
NASA Technical Reports Server (NTRS)
Mahajan, Aparajit J.; Stefko, George L.
1993-01-01
A CFD solver called ADPAC-APES is coupled with a NASTRAN structural analysis and a MARC thermal/heat transfer analysis to determine rotor blade shape. Nonlinear blade displacements due to centrifugal loads, aerodynamic pressures, and nonuniform temperature distribution are determined simultaneously. The effect of blade displacements on aerodynamic pressures and temperatures is then analyzed. These calculations are iterated till a steady state is reached across all the disciplines. This iterative procedure is applied to a ducted fan rotor blade and the manufactured shape is determined from a given operating shape. Effect of a part-span shroud on blade deflections is also analyzed.
Shape reanalysis and sensitivities utilizing preconditioned iterative boundary solvers
NASA Technical Reports Server (NTRS)
Guru Prasad, K.; Kane, J. H.
1992-01-01
The computational advantages associated with the utilization of preconditined iterative equation solvers are quantified for the reanalysis of perturbed shapes using continuum structural boundary element analysis (BEA). Both single- and multi-zone three-dimensional problems are examined. Significant reductions in computer time are obtained by making use of previously computed solution vectors and preconditioners in subsequent analyses. The effectiveness of this technique is demonstrated for the computation of shape response sensitivities required in shape optimization. Computer times and accuracies achieved using the preconditioned iterative solvers are compared with those obtained via direct solvers and implicit differentiation of the boundary integral equations. It is concluded that this approach employing preconditioned iterative equation solvers in reanalysis and sensitivity analysis can be competitive with if not superior to those involving direct solvers.
Estimated spectrum adaptive postfilter and the iterative prepost filtering algirighms
NASA Technical Reports Server (NTRS)
Linares, Irving (Inventor)
2004-01-01
The invention presents The Estimated Spectrum Adaptive Postfilter (ESAP) and the Iterative Prepost Filter (IPF) algorithms. These algorithms model a number of image-adaptive post-filtering and pre-post filtering methods. They are designed to minimize Discrete Cosine Transform (DCT) blocking distortion caused when images are highly compressed with the Joint Photographic Expert Group (JPEG) standard. The ESAP and the IPF techniques of the present invention minimize the mean square error (MSE) to improve the objective and subjective quality of low-bit-rate JPEG gray-scale images while simultaneously enhancing perceptual visual quality with respect to baseline JPEG images.
NASA Astrophysics Data System (ADS)
Iotti, Robert
2015-04-01
been present at the beginning, ITER would be in far better shape. As is, it can provide good lessons to avoid the same problems in the future. The ITER Council is now applying those lessons. A very experienced new Director General has just been appointed. He has instituted a number of drastic changes, but still within the governance of the JIA. Will there changes be effective? Only time will tell, but I am optimistic.
NASA Astrophysics Data System (ADS)
Widdle, Richard D., Jr.; Grimshaw, Matthew T.; Shome, Moushumi
2009-03-01
A method is described for solving an inverse design problem to find the unassembled, stress-free component shapes of a structure thatis integrally actuated with shape memory alloy (SMA) actuators. Morphing and multifunctional structures are of interest in the aerospace industry becasue of the potential for improving structural and aerodynamic performance across multiple operating conditions. The focus of this work is on structures that are morphed with SMA flexural actuators. For the case where the geometry is known for unassembled components, assembly can be simulated to find the assembled shapes of the morphing structure. In the usual design case, however, only the desired shapes as assembled are known in multiple actuation states, and the corresponding unassembled shapes must be determined by an iterative solution process. An iterative finite element analysis approach to this problem is reported here. First an initial guess for the unassembled shapes is made and assembly is simulated with the finite element method. The resulting shapes are found for both SMA phases and compared with the desired shapes. A gradient-based optimization method is employed to update the initial geometry and iteration continues until the desired shapes are achieved. A simplified method of modeling the SMA material behavior is used for computational efficiently. It is found that this approach provides a practical way to solve the inverse design problem for structures that are integrally actuated with SMA material.
Cochlea segmentation using iterated random walks with shape prior
NASA Astrophysics Data System (ADS)
Ruiz Pujadas, Esmeralda; Kjer, Hans Martin; Vera, Sergio; Ceresa, Mario; González Ballester, Miguel Ángel
2016-03-01
Cochlear implants can restore hearing to deaf or partially deaf patients. In order to plan the intervention, a model from high resolution µCT images is to be built from accurate cochlea segmentations and then, adapted to a patient-specific model. Thus, a precise segmentation is required to build such a model. We propose a new framework for segmentation of µCT cochlear images using random walks where a region term is combined with a distance shape prior weighted by a confidence map to adjust its influence according to the strength of the image contour. Then, the region term can take advantage of the high contrast between the background and foreground and the distance prior guides the segmentation to the exterior of the cochlea as well as to less contrasted regions inside the cochlea. Finally, a refinement is performed preserving the topology using a topological method and an error control map to prevent boundary leakage. We tested the proposed approach with 10 datasets and compared it with the latest techniques with random walks and priors. The experiments suggest that this method gives promising results for cochlea segmentation.
Toward a design for the ITER plasma shape and stability control system
Humphreys, D.A.; Leuer, J.A.; Kellman, A.G.; Haney, S.W.; Bulmer, R.H.; Pearlstein, L.D.; Portone, A.
1994-07-01
A design strategy for an integrated shaping and stability control algorithm for ITER is described. This strategy exploits the natural multivariable nature of the system so that all poloidal field coils are used to simultaneously control all regulated plasma shape and position parameters. A nonrigid, flux-conserving linearized plasma response model is derived using a variational procedure analogous to the ideal MHD Extended Energy Principle. Initial results are presented for the non-rigid plasma response model approach applied to an example DIII-D equilibrium. For this example, the nonrigid model is found to yield a higher passive growth rate than a rigid current-conserving plasma response model. Multivariable robust controller design methods are discussed and shown to be appropriate for the ITER shape control problem.
Design of computer-generated beam-shaping holograms by iterative finite-element mesh adaption.
Dresel, T; Beyerlein, M; Schwider, J
1996-12-10
Computer-generated phase-only holograms can be used for laser beam shaping, i.e., for focusing a given aperture with intensity and phase distributions into a pregiven intensity pattern in their focal planes. A numerical approach based on iterative finite-element mesh adaption permits the design of appropriate phase functions for the task of focusing into two-dimensional reconstruction patterns. Both the hologram aperture and the reconstruction pattern are covered by mesh mappings. An iterative procedure delivers meshes with intensities equally distributed over the constituting elements. This design algorithm adds new elementary focuser functions to what we call object-oriented hologram design. Some design examples are discussed.
RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities
NASA Astrophysics Data System (ADS)
Evans, T. E.; Fenstermacher, M. E.; Moyer, R. A.; Osborne, T. H.; Watkins, J. G.; Gohil, P.; Joseph, I.; Schaffer, M. J.; Baylor, L. R.; Bécoulet, M.; Boedo, J. A.; Burrell, K. H.; de Grassie, J. S.; Finken, K. H.; Jernigan, T.; Jakubowski, M. W.; Lasnier, C. J.; Lehnen, M.; Leonard, A. W.; Lonnroth, J.; Nardon, E.; Parail, V.; Schmitz, O.; Unterberg, B.; West, W. P.
2008-02-01
Large Type-I edge localized modes (ELMs) are completely eliminated with small n = 3 resonant magnetic perturbations (RMP) in low average triangularity, \\bar {\\delta }=0.26 , plasmas and in ITER similar shaped (ISS) plasmas, \\bar {\\delta }=0.53 , with ITER relevant collisionalities v_e^\\ast \\le 0.2 . Significant differences in the RMP requirements and in the properties of the ELM suppressed plasmas are found when comparing the two triangularities. In ISS plasmas, the current required to suppress ELMs is approximately 25% higher than in low average triangularity plasmas. It is also found that the width of the resonant q95 window required for ELM suppression is smaller in ISS plasmas than in low average triangularity plasmas. An analysis of the positions and widths of resonant magnetic islands across the pedestal region, in the absence of resonant field screening or a self-consistent plasma response, indicates that differences in the shape of the q profile may explain the need for higher RMP coil currents during ELM suppression in ISS plasmas. Changes in the pedestal profiles are compared for each plasma shape as well as with changes in the injected neutral beam power and the RMP amplitude. Implications of these results are discussed in terms of requirements for optimal ELM control coil designs and for establishing the physics basis needed in order to scale this approach to future burning plasma devices such as ITER.
The Normalized-Rate Iterative Algorithm: A Practical Dynamic Spectrum Management Method for DSL
NASA Astrophysics Data System (ADS)
Statovci, Driton; Nordström, Tomas; Nilsson, Rickard
2006-12-01
We present a practical solution for dynamic spectrum management (DSM) in digital subscriber line systems: the normalized-rate iterative algorithm (NRIA). Supported by a novel optimization problem formulation, the NRIA is the only DSM algorithm that jointly addresses spectrum balancing for frequency division duplexing systems and power allocation for the users sharing a common cable bundle. With a focus on being implementable rather than obtaining the highest possible theoretical performance, the NRIA is designed to efficiently solve the DSM optimization problem with the operators' business models in mind. This is achieved with the help of two types of parameters: the desired network asymmetry and the desired user priorities. The NRIA is a centralized DSM algorithm based on the iterative water-filling algorithm (IWFA) for finding efficient power allocations, but extends the IWFA by finding the achievable bitrates and by optimizing the bandplan. It is compared with three other DSM proposals: the IWFA, the optimal spectrum balancing algorithm (OSBA), and the bidirectional IWFA (bi-IWFA). We show that the NRIA achieves better bitrate performance than the IWFA and the bi-IWFA. It can even achieve performance almost as good as the OSBA, but with dramatically lower requirements on complexity. Additionally, the NRIA can achieve bitrate combinations that cannot be supported by any other DSM algorithm.
A noise power spectrum study of a new model-based iterative reconstruction system: Veo 3.0.
Li, Guang; Liu, Xinming; Dodge, Cristina T; Jensen, Corey T; Rong, X John
2016-01-01
The purpose of this study was to evaluate performance of the third generation of model-based iterative reconstruction (MBIR) system, Veo 3.0, based on noise power spectrum (NPS) analysis with various clinical presets over a wide range of clinically applicable dose levels. A CatPhan 600 surrounded by an oval, fat-equivalent ring to mimic patient size/shape was scanned 10 times at each of six dose levels on a GE HD 750 scanner. NPS analysis was performed on images reconstructed with various Veo 3.0 preset combinations for comparisons of those images reconstructed using Veo 2.0, filtered back projection (FBP) and adaptive statistical iterative reconstruc-tion (ASiR). The new Target Thickness setting resulted in higher noise in thicker axial images. The new Texture Enhancement function achieved a more isotropic noise behavior with less image artifacts. Veo 3.0 provides additional reconstruction options designed to allow the user choice of balance between spatial resolution and image noise, relative to Veo 2.0. Veo 3.0 provides more user selectable options and in general improved isotropic noise behavior in comparison to Veo 2.0. The overall noise reduction performance of both versions of MBIR was improved in comparison to FBP and ASiR, especially at low-dose levels. PMID:27685118
Billings, Seth D; Boctor, Emad M; Taylor, Russell H
2015-01-01
We present a probabilistic registration algorithm that robustly solves the problem of rigid-body alignment between two shapes with high accuracy, by aptly modeling measurement noise in each shape, whether isotropic or anisotropic. For point-cloud shapes, the probabilistic framework additionally enables modeling locally-linear surface regions in the vicinity of each point to further improve registration accuracy. The proposed Iterative Most-Likely Point (IMLP) algorithm is formed as a variant of the popular Iterative Closest Point (ICP) algorithm, which iterates between point-correspondence and point-registration steps. IMLP's probabilistic framework is used to incorporate a generalized noise model into both the correspondence and the registration phases of the algorithm, hence its name as a most-likely point method rather than a closest-point method. To efficiently compute the most-likely correspondences, we devise a novel search strategy based on a principal direction (PD)-tree search. We also propose a new approach to solve the generalized total-least-squares (GTLS) sub-problem of the registration phase, wherein the point correspondences are registered under a generalized noise model. Our GTLS approach has improved accuracy, efficiency, and stability compared to prior methods presented for this problem and offers a straightforward implementation using standard least squares. We evaluate the performance of IMLP relative to a large number of prior algorithms including ICP, a robust variant on ICP, Generalized ICP (GICP), and Coherent Point Drift (CPD), as well as drawing close comparison with the prior anisotropic registration methods of GTLS-ICP and A-ICP. The performance of IMLP is shown to be superior with respect to these algorithms over a wide range of noise conditions, outliers, and misalignments using both mesh and point-cloud representations of various shapes.
Billings, Seth D.; Boctor, Emad M.; Taylor, Russell H.
2015-01-01
We present a probabilistic registration algorithm that robustly solves the problem of rigid-body alignment between two shapes with high accuracy, by aptly modeling measurement noise in each shape, whether isotropic or anisotropic. For point-cloud shapes, the probabilistic framework additionally enables modeling locally-linear surface regions in the vicinity of each point to further improve registration accuracy. The proposed Iterative Most-Likely Point (IMLP) algorithm is formed as a variant of the popular Iterative Closest Point (ICP) algorithm, which iterates between point-correspondence and point-registration steps. IMLP’s probabilistic framework is used to incorporate a generalized noise model into both the correspondence and the registration phases of the algorithm, hence its name as a most-likely point method rather than a closest-point method. To efficiently compute the most-likely correspondences, we devise a novel search strategy based on a principal direction (PD)-tree search. We also propose a new approach to solve the generalized total-least-squares (GTLS) sub-problem of the registration phase, wherein the point correspondences are registered under a generalized noise model. Our GTLS approach has improved accuracy, efficiency, and stability compared to prior methods presented for this problem and offers a straightforward implementation using standard least squares. We evaluate the performance of IMLP relative to a large number of prior algorithms including ICP, a robust variant on ICP, Generalized ICP (GICP), and Coherent Point Drift (CPD), as well as drawing close comparison with the prior anisotropic registration methods of GTLS-ICP and A-ICP. The performance of IMLP is shown to be superior with respect to these algorithms over a wide range of noise conditions, outliers, and misalignments using both mesh and point-cloud representations of various shapes. PMID:25748700
Impact of a narrow limiter SOL heat flux channel on the ITER first wall panel shaping
NASA Astrophysics Data System (ADS)
Kocan, M.; Pitts, R. A.; Arnoux, G.; Balboa, I.; de Vries, P. C.; Dejarnac, R.; Furno, I.; Goldston, R. J.; Gribov, Y.; Horacek, J.; Komm, M.; Labit, B.; LaBombard, B.; Lasnier, C. J.; Mitteau, R.; Nespoli, F.; Pace, D.; Panek, R.; Stangeby, P. C.; Terry, J. L.; Tsui, C.; Vondracek, P.
2015-03-01
The inboard limiters for ITER were initially designed on the assumption that the parallel heat flux density in the scrape-off layer (SOL) could be approximated by a single exponential with decay length λq. This assumption was found not to be adequate in 2012, when infra-red (IR) thermography measurements on the inner column during JET limiter discharges clearly revealed the presence of a narrow heat flux channel adjacent to the last closed flux surface. This near-SOL decay occurs with λq ∼ few mm, much shorter than the main SOL λq, and can raise the heat flux at the limiter apex a factor up to ∼4 above the value expected from a single, broader exponential. The original logarithmically shaped ITER inner wall first wall panels (FWPs) would be unsuited to handling the power loads produced by such a narrow feature. A multi-machine study involving the C-Mod, COMPASS, DIII-D and TCV tokamaks, employing inner wall IR measurements and/or inner wall reciprocating probes, was initiated to investigate the narrow limiter SOL heat flux channel. This paper describes the new results which have provided an experimental database for the narrow feature and presents an ITER inner wall FWP toroidal shape optimized for a double-exponential profile with λq = 4 (narrow feature) and 50 mm (main-SOL), the latter also derived from a separate multi-machine database constituted recently within the International Tokamak Physics Activity. It is shown that the new shape allows the power handling capability of the original shape design to be completely recovered for a wide variety of limiter start-up equilibria in the presence of a narrow feature, even taking assembly tolerances into account. It is, moreover, further shown that the new shape has the interesting property of both mitigating the impact of the narrow feature and resulting in only a very modest increase in heat load, compared to the current design, if the narrow feature is not eventually found on ITER.
Fractal Spectrum Technique for Quantitative Analysis of Volcanic Particle Shapes
NASA Astrophysics Data System (ADS)
Maria, A. H.; Carey, S. N.
2001-12-01
The shapes of volcanic particles reflect numerous eruptive parameters (e.g. magma viscosity, volatile content, degree of interaction with water) and are useful for understanding fragmentation and transport processes associated with volcanic eruptions. However, quantitative analysis of volcanic particle shapes has proven difficult due to their morphological complexity and variability. Shape analysis based on fractal geometry has been successfully applied to a wide variety of particles and appears to be well suited for describing complex features. The technique developed and applied to volcanic particles in this study uses fractal data produced by dilation of the 2-D particle boundary to produce a full spectrum of fractal dimensions over a range of scales for each particle. Multiple fractal dimensions, which can be described as a fractal spectrum curve, are calculated by taking the first derivative of data points on a standard Richardson plot. Quantitative comparisons are carried out using multivariate statistical techniques such as cluster and principal components analysis. Compared with previous fractal methods that express shape in terms of only one or two fractal dimensions, use of multiple fractal dimensions results in more effective discrimination between samples. In addition, the technique eliminates the subjectivity associated with selecting linear segments on Richardson plots for fractal dimension calculation, and allows direct comparison of particles as long as instantaneous dimensions used as input to multivariate analyses are selected at the same scales for each particle. Applications to samples from well documented eruptions (e.g. Mt. St. Helens, Tambora, Surtsey) indicate that the fractal spectrum technique provides a useful means of characterizing volcanic particles and can be helpful for identifying the products of specific fragmentation processes (volatile exsolution, phreatomagmatic, quench granulation) and modes of volcanic deposition (tephra fall
Hybrid iterative wavefront shaping for high-speed focusing through scattering media
NASA Astrophysics Data System (ADS)
Hemphill, Ashton S.; Wang, Lihong V.
2016-03-01
A major limiting factor of optical imaging in biological applications is the diffusion of light by tissue, preventing focusing at depths greater than ~1 mm in the body. To overcome this issue, phase-based wavefront shaping alters the phase of sections of the incident wavefront to counteract aberrations in phase caused by scattering. This enables focusing through scattering media beyond the optical diffusion limit and increases signal compared to amplitude-based compensation. However, in previous studies, speed of optimization has typically been limited by the use of a liquid crystal spatial light modulator (SLM) for measurement and display. SLMs usually have refresh rates of less than 100 Hz and require much longer than the speckle correlation time of tissue in vivo, usually on the order of milliseconds, to determine the optimal wavefront. Here, we present a phase-based iterative wavefront shaping method based on an onaxis digital micromirror device (DMD) in conjunction with an electro-optic modulator (EOM) for measurement and a fast SLM for display. By combining phase modulation from an EOM with the modal selection of the DMD, we take advantage of DMDs higher refresh rate, approximately 23 kHz, for iterative phase measurement. The slower SLM requires one update for display following the rapid determination of the optimal wavefront via the DMD, allowing for high-speed wavefront shaping. Using this system, we are able to focus through scattering media using 64 modes in under 8 milliseconds, on the order of the speckle correlation time for tissue in vivo.
NASA Astrophysics Data System (ADS)
Yu, Biin; Peng, Xiang; Tian, Jindong; Niu, Hanben
2006-01-01
A cascaded iterative angular spectrum approach (CIASA) based on the methodology of virtual optics is presented for optical security applications. The technique encodes the target image into two different phase only masks (POM) using a concept of free-space angular spectrum propagation. The two phase-masks are designed and located in any two arbitrary planes interrelated through the free space propagation domain in order to implement the optical encryption or authenticity verification. And both phase masks can serve as enciphered texts. Compared with previous methods, the proposed algorithm employs an improved searching strategy: modifying the phase-distributions of both masks synchronously as well as enlarging the searching space. And with such a scheme, we make use of a high performance floating-point Digital Signal Processor (DSP) to accomplish a design of multiple-locks and multiple-keys optical image encryption system. An evaluation of the system performance is made and it is shown that the algorithm results in much faster convergence and better image quality for the recovered image. And two masks and system parameters can be used to design keys for image encryption, therefore the decrypted image can be obtained only when all these keys are under authorization. This key-assignment strategy may reduce the risk of being intruded and show a high security level. These characters may introduce a high level security that makes the encrypted image more difficult to be decrypted by an unauthorized person.
The Neutron-Gamma Pulse Shape Discrimination Method for Neutron Flux Detection in the ITER
NASA Astrophysics Data System (ADS)
Xu, Xiufeng; Li, Shiping; Cao, Hongrui; Yuan, Guoliang; Yang, Qingwei; Yin, Zejie
2013-05-01
The neutron flux monitor (NFM), as a significant diagnostic system in the International Thermonuclear Experimental Reactor (ITER), will play an important role in the readings of a series of key parameters in the fusion reaction process. As the core of the main electronic system of the NFM, the neutron-gamma pulse shape discrimination (n-γ PSD) can distinguish the neutron pulse from the gamma pulse and other disturbing pulses according to the thresholds of the rising time and the amplitude pre-installed on the board, the double timing point CFD method is used to get the rising time of the pulse. The n-γ PSD can provide an accurate neutron count.
NASA Astrophysics Data System (ADS)
Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.
2013-07-01
In this work the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetry with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures, in neural
Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solis Sanches, L. O.; Miranda, R. Castaneda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.
2013-07-03
In this work the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetry with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures, in neural
Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand
2015-04-21
A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phasemore » distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.« less
Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand
2015-04-21
A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phase distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.
Shaping the Future for Children with Foetal Alcohol Spectrum Disorders
ERIC Educational Resources Information Center
Blackburn, Carolyn; Carpenter, Barry; Egerton, Jo
2010-01-01
This article describes work undertaken in connection with an ongoing research project funded by the Training and Development Agency for Schools. It illustrates the educational implications of foetal alcohol spectrum disorders (FASD) and its implications for the educational workforce in seeking to meet the needs of those children who are affected.
Infrared spectrum of nitric acid dihydrate: Influence of particle shape.
Wagner, Robert; Möhler, Ottmar; Saathoff, Harald; Stetzer, Olaf; Schurath, Ulrich
2005-03-24
In situ Fourier transform infrared (FTIR) extinction spectra of airborne alpha-NAD microparticles generated by two different methods were recorded in the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. The extinction spectrum of alpha-NAD crystals obtained by shock freezing of a HNO3/H2O gas mixture could be accurately reproduced using Mie theory with published refractive indices of alpha-NAD as input. In contrast, Mie theory proved to be inadequate to properly reproduce the infrared extinction spectrum of alpha-NAD crystals which were formed via homogeneous nucleation of supercooled HNO3/H2O solution droplets, evaporating slowly on a time scale of several hours at about 195 K. Much better agreement between measured and calculated extinction spectra was obtained by T-matrix calculations assuming oblate particles with aspect ratios greater than five. This indicates that strongly aspherical alpha-NAD crystals are obtained when supercooled nitric acid solution droplets freeze and grow slowly, a process which has been discussed as a potential pathway to the formation of crystalline polar stratospheric cloud (PSC) particles. PMID:16833561
Operating Characteristics in DIII-D ELM-Suppressed RMP H-modes with ITER Similar Shapes
Evans, T E; Fenstermacher, M E; Jakubowski, M; Moyer, R A; Osborne, T H; Schaffer, M J; Schmitz, O; Watkins, J G; Zeng, L; Baylor, L R; Boedo, J A; Burrell, K H; deGrassie, J S; Gohil, P; Joseph, I; Lasnier, C J; Leonard, A W; Mordijck, S; Petty, C C; Pinsker, R I; Rhodes, T L; Rost, J C; Snyder, P B; Unterberg, E; West, W P
2008-10-13
Fast energy transients, incident on the DIII-D divertors due to Type-I edge localized modes (ELMs), are eliminated using small dc currents in a simple set of non-axisymmetric coils that produce edge resonant magnetic perturbations (RMP). In ITER similar shaped (ISS) plasmas, with electron pedestal collisionalities matched to those expected in ITER a sharp resonant window in the safety factor at the 95 percent normalized poloidal flux surface is observed for ELM suppression at q{sub 95}=3.57 with a minimum width {delta}q{sub 95} of {+-}0.05. The size of this resonant window has been increased by a factor of 4 in ISS plasmas by increasing the magnitude of the current in an n=3 coil set along with the current in a separate n=1 coil set. The resonant ELM-suppression window is highly reproducible for a given plasma shape, coil configuration and coil current but can vary with other operating conditions such as {beta}{sub N}. Isolated resonant windows have also been found at other q95 values when using different RMP coil configurations. For example, when the I-coil is operated in an n=3 up-down asymmetric configuration rather than an up-down symmetric configuration a resonant window is found near q{sub 95}=7.4. A Fourier analysis of the applied vacuum magnetic field demonstrates a statistical correlation between the Chirikov island overlap parameter and ELM suppression. These results have been used as a guide for RMP coil design studies in various ITER operating scenarios.
Iterated intracochlear reflection shapes the envelopes of basilar-membrane click responses.
Shera, Christopher A
2015-12-01
Multiple internal reflection of cochlear traveling waves has been argued to provide a plausible explanation for the waxing and waning and other temporal structures often exhibited by the envelopes of basilar-membrane (BM) and auditory-nerve responses to acoustic clicks. However, a recent theoretical analysis of a BM click response measured in chinchilla concludes that the waveform cannot have arisen via any equal, repetitive process, such as iterated intracochlear reflection [Wit and Bell (2015), J. Acoust. Soc. Am. 138, 94-96]. Reanalysis of the waveform contradicts this conclusion. The measured BM click response is used to derive the frequency-domain transfer function characterizing every iteration of the loop. The selfsame transfer function that yields waxing and waning of the BM click response also captures the spectral features of ear-canal stimulus-frequency otoacoustic emissions measured in the same animal, consistent with the predictions of multiple internal reflection. Small shifts in transfer-function phase simulate results at different measurement locations and reproduce the heterogeneity of BM click response envelopes observed experimentally. PMID:26723327
NASA Astrophysics Data System (ADS)
Feng, Zhipeng; Chen, Xiaowang; Liang, Ming
2016-08-01
Planetary gearbox vibration signals under nonstationary conditions are characterized by time-varying nature and complex multi-components, making it very difficult to extract features for fault diagnosis. Order spectrum analysis is one of the effective approaches for nonstationary signal analysis of rotating machinery. The main idea of order analysis is to map the time-varying frequency components into constant ones. Inspired by this idea, we propose a new order spectrum analysis method to exploit the unique property of iterative generalized demodulation in converting arbitrary instantaneous frequency trajectories of multi-component signals into constant frequency lines on the time-frequency plane. This new method is completely algorithm-based and tachometer/encoder-free, thus easy to implement. It does not involve equi-angular resampling commonly required by most order tracking methods and is hence free from the decimation and/or interpolation error. The proposed order analysis method can eliminate the time-variation effect of frequency and thus can effectively reveal the harmonic order constituents of nonstationary multi-component signals. However, the planetary gearbox vibration signals also lead to complex sideband orders. As such, we further propose to analyze the order spectrum of amplitude envelope. This will eliminate the complex sideband orders in the order spectrum of original signals, leading to a substantially simplified and more reliable gear characteristic frequency identification process. Nevertheless, the gear and/or planet carrier rotating frequency orders, which are irrelevant to gear fault, may still exist. To avoid possible misleading results due to such frequency orders, we also propose to analyze the order spectrum of instantaneous frequency. Theoretically, the peaks present in frequency order spectrum directly correspond to the gear characteristic frequency orders, which can be used to extract gear fault signature more explicitly. The proposed
NASA Astrophysics Data System (ADS)
Cherkasov, M. R.
2014-07-01
The theory of relaxation parameters of the spectrum shape in the impact approximation is constructed as a limit case of the Fano general relaxation theory of pressure broadening. The Fano binary collision relaxation matrix is presented in the integral form and after the impact approximation is introduced it is expressed through the scattering matrix in the Liouville space of the absorbing molecule and the bath particle. By means of introducing the scattering matrix eigenvectors and solving the evolution equation in the matrix form, the method suitable for the calculation of the whole set of impact relaxation parameters of the spectrum shape has been developed.
NASA Astrophysics Data System (ADS)
Gouesbet, Gérard; Mees, Loic; Gréhan, Gérard; Ren, Kuan Fang
1999-03-01
The description of arbitrary shaped beams in elliptical cylinder coordinates is presented by using a plane wave spectrum approach. It is demonstrated and exemplified that this approach is equivalent to a formally more rigorous approach in terms of distributions. Beam shape coefficients are evaluated by using quadratures. The behavior of these quadratures is discussed in the case of a first-order Davis beam which does not exactly satisfy Maxwell's equations.
Potrzeba, Emily R; Fein, Deborah; Naigles, Letitia
2015-01-01
Young typically developing (TD) children have been observed to utilize word learning strategies such as the noun bias and shape bias; these improve their efficiency in acquiring and categorizing novel terms. Children using the shape bias extend object labels to new objects of the same shape; thus, the shape bias prompts the categorization of object words based on the global characteristic of shape over local, discrete details. Individuals with autism spectrum disorders (ASDs) frequently attend to minor details of objects rather than their global structure. Therefore, children with ASD may not use shape bias to acquire new words. Previous research with children with ASD has provided evidence that they parallel TD children in showing a noun bias, but not a shape bias (Tek et al., 2008). However, this sample was small and individual and item differences were not investigated in depth. In an extension of Tek et al. (2008) with twice the sample size and a wider developmental timespan, we tested 32 children with ASD and 35 TD children in a longitudinal study across 20 months using the intermodal preferential looking paradigm. Children saw five triads of novel objects (target, shape-match, color-match) in both NoName and Name trials; those who looked longer at the shape-match during the Name trials than the NoName trials demonstrated a shape bias. The TD group showed a significant shape bias at all visits, beginning at 20 months of age while the language-matched ASD group did not show a significant shape bias at any visit. Within the ASD group, though, some children did show a shape bias; these children had larger vocabularies concurrently and longitudinally. Degree of shape bias elicitation varied by item, but did not seem related to perceptual complexity. We conclude that shape does not appear to be an organizing factor for word learning by children with ASD. PMID:25954219
Potrzeba, Emily R.; Fein, Deborah; Naigles, Letitia
2015-01-01
Young typically developing (TD) children have been observed to utilize word learning strategies such as the noun bias and shape bias; these improve their efficiency in acquiring and categorizing novel terms. Children using the shape bias extend object labels to new objects of the same shape; thus, the shape bias prompts the categorization of object words based on the global characteristic of shape over local, discrete details. Individuals with autism spectrum disorders (ASDs) frequently attend to minor details of objects rather than their global structure. Therefore, children with ASD may not use shape bias to acquire new words. Previous research with children with ASD has provided evidence that they parallel TD children in showing a noun bias, but not a shape bias (Tek et al., 2008). However, this sample was small and individual and item differences were not investigated in depth. In an extension of Tek et al. (2008) with twice the sample size and a wider developmental timespan, we tested 32 children with ASD and 35 TD children in a longitudinal study across 20 months using the intermodal preferential looking paradigm. Children saw five triads of novel objects (target, shape-match, color-match) in both NoName and Name trials; those who looked longer at the shape-match during the Name trials than the NoName trials demonstrated a shape bias. The TD group showed a significant shape bias at all visits, beginning at 20 months of age while the language-matched ASD group did not show a significant shape bias at any visit. Within the ASD group, though, some children did show a shape bias; these children had larger vocabularies concurrently and longitudinally. Degree of shape bias elicitation varied by item, but did not seem related to perceptual complexity. We conclude that shape does not appear to be an organizing factor for word learning by children with ASD. PMID:25954219
ERIC Educational Resources Information Center
Qiu, Anqi; Adler, Marcy; Crocetti, Deana; Miller, Michael I.; Mostofsky, Stewart H.
2010-01-01
Objective: Basal ganglia abnormalities have been suggested as contributing to motor, social, and communicative impairments in autism spectrum disorder (ASD). Volumetric analyses offer limited ability to detect localized differences in basal ganglia structure. Our objective was to investigate basal ganglia shape abnormalities and their association…
Gaps in the essential spectrum of infinite periodic necklace-shaped elastic waveguide
NASA Astrophysics Data System (ADS)
Nazarov, Sergey A.; Ruotsalainen, Keijo; Taskinen, Jari
2009-03-01
We describe a periodic homogeneous elastic waveguide of a particular shape of beads connected by ligaments of diameter O(h) such that the essential spectrum contains gaps, the number of which grows unboundedly when h tends to +0. To cite this article: S.A. Nazarov et al., C. R. Mecanique 337 (2009).
Palm-shaped spectrum generation for dual-band millimeter wave and baseband signals over fiber
NASA Astrophysics Data System (ADS)
Lin, R.; Feng, Z.; Tang, M.; Wang, R.; Fu, S.; Shum, P.; Liu, D.; Chen, J.
2016-05-01
In order to offer abundant available bandwidth for radio access networks satisfying future 5G requirements on capacity, this paper proposes a simple and cost-effective palm-shaped spectrum generation scheme that can be used for high capacity radio over fiber (RoF) system. The proposed scheme can simultaneously generate an optical carrier used for upstream and two bands of millimeter wave (MMW) that are capable of carrying different downstream data. The experiment results show that the proposed palm-shaped spectrum generation scheme outperforms optical frequency comb (OFC) based multi-band MMW generation in terms of upstream transmission performance. Furthermore, simulation is carried out with different dual-band MMW configurations to verify the feasibility of using the proposed spectrum generation scheme in the RoF system.
Do Children with Autism Spectrum Disorders Show a Shape Bias in Word Learning?
Tek, Saime; Jaffery, Gul; Fein, Deborah; Naigles, Letitia R.
2009-01-01
Many children with autism spectrum disorders (ASD) acquire a sizeable lexicon. However, these children also seem to understand and/or store the meanings of words differently from typically developing children. One of the mechanisms that helps typically developing children learn novel words is the shape bias, in which the referent of a noun is mapped onto the shape of an object, rather than onto its color, texture, or size. We hypothesized that children with Autistic Disorder would show reduced or absent shape bias. Using the Intermodal Preferential Looking Paradigm (IPL), we compared the performance of young children with ASD and typically developing children (TYP), across four time points, in their use of shape bias. Neither group showed a shape bias at Visit 1, when half of the children in both groups produced fewer than 50 count nouns. Only the TYP group showed a shape bias at Visits 2, 3, and 4. According to growth curve analyses, the rate of increase in the shape bias scores over time was significant for the TYP children. The fact that the TYP group showed a shape bias at 24 months of age, whereas children with ASD did not demonstrate a shape bias despite a sizeable vocabulary, supports a dissociation between vocabulary size and principles governing acquisition in ASD children from early in language development. PMID:19360671
NASA Astrophysics Data System (ADS)
Messiaen, A.; Swain, D.; Ongena, J.; Vervier, M.
2015-12-01
The paper analyses how the phasing of the ITER ICRH 24 strap array evolves from the power sources up to the strap currents of the antenna. The study of the phasing control and coherence through the feeding circuits with prematching and automatic matching and decoupling network is made by modeling starting from the TOPICA matrix of the antenna array for a low coupling plasma profile and for current drive phasing (worst case for mutual coupling effects). The main results of the analysis are: (i) the strap current amplitude is well controlled by the antinode Vmax amplitude of the feeding lines, (ii) the best toroidal phasing control is done by the adjustment of the mean phase of Vmax of each poloidal straps column, (iii) with well adjusted system the largest strap current phasing error is ±20°, (iv) the effect on load resilience remains well below the maximum affordable VSWR of the generators, (v) the effect on the radiated power spectrum versus k// computed by means of the coupling code ANTITER II remains small for the considered cases.
Messiaen, A. Ongena, J.; Vervier, M.; Swain, D.
2015-12-10
The paper analyses how the phasing of the ITER ICRH 24 strap array evolves from the power sources up to the strap currents of the antenna. The study of the phasing control and coherence through the feeding circuits with prematching and automatic matching and decoupling network is made by modeling starting from the TOPICA matrix of the antenna array for a low coupling plasma profile and for current drive phasing (worst case for mutual coupling effects). The main results of the analysis are: (i) the strap current amplitude is well controlled by the antinode V{sub max} amplitude of the feeding lines, (ii) the best toroidal phasing control is done by the adjustment of the mean phase of V{sub max} of each poloidal straps column, (iii) with well adjusted system the largest strap current phasing error is ±20°, (iv) the effect on load resilience remains well below the maximum affordable VSWR of the generators, (v) the effect on the radiated power spectrum versus k{sub //} computed by means of the coupling code ANTITER II remains small for the considered cases.
Messiaen, Andre; Swain, David W; Ongena, Jef; Vervier, Michael
2015-01-01
The paper analyses how the phasing of the ITER ICRH 24 strap array evolves from the power sources up to the strap currents of the antenna. The study of the phasing control and coherence through the feeding circuits with prematching and automatic matching and decoupling network is made by modeling starting from the TOPICA matrix of the antenna array for a low coupling plasma profile and for current drive phasing (worst case for mutual coupling effects). The main results of the analysis are: (i) the strap current amplitude is well controlled by the antinode V-max amplitude of the feeding lines, (ii) the best toroidal phasing control is done by the adjustment of the mean phase of V-max of each poloidal straps column, (iii) with well adjusted system the largest strap current phasing error is +/- 20 degrees, (iv) the effect on load resilience remains well below the maximum affordable VSWR of the generators, (v) the effect on the radiated power spectrum versus k//computed by means of the coupling code ANTITER II remains small for the considered cases. [GRAPHICS] .
On the Phase-Averaged Spectrum of Pulsars and Shape of Their Cutoffs
NASA Technical Reports Server (NTRS)
Celik, O.; Thomas, T. J.
2010-01-01
All gamma ray pulsars exhibit an exponential cutoff in their spectra and for bright pulsars the statistics are sufficiently high to study the detailed shape of the cutoff. The phase averaged spectra of some pulsars exhibit a sub-exponential cutoff, not predicted by any single physical mechanism. Further studies clarified that (his gentler average cutoff is a consequence of having significant variations of the cutoff energy in the phase-resolved spectrum. In conclusion, the phase-averaged spectrum of a pulsar is not a physical quantity to test high-energy emission models.
NASA Astrophysics Data System (ADS)
Kikuchi, Tsuneo; Nakazawa, Toshihiro; Furukawa, Tetsuo; Higuchi, Toshiyuki; Maruyama, Yukio; Sato, Sojun
1995-05-01
This paper describes the quantitative measurement of the amount of fibrosis in the rat liver using the fractal dimension of the shape of power spectrum. The shape of the power spectrum of the scattered echo from biotissues is strongly affected by its internal structure. The fractal dimension, which is one of the important parameters of the fractal theory, is useful to express the complexity of shape of figures such as the power spectrum. From in vitro experiments using rat liver, it was found that this method can be used to quantitatively measure the amount of fibrosis in the liver, and has the possibility for use in the diagnosis of human liver cirrhosis.
NASA Astrophysics Data System (ADS)
Ge, Xinmin; Wang, Hua; Fan, Yiren; Cao, Yingchang; Chen, Hua; Huang, Rui
2016-01-01
With more information than the conventional one dimensional (1D) longitudinal relaxation time (T1) and transversal relaxation time (T2) spectrums, a two dimensional (2D) T1-T2 spectrum in a low field nuclear magnetic resonance (NMR) is developed to discriminate the relaxation components of fluids such as water, oil and gas in porous rock. However, the accuracy and efficiency of the T1-T2 spectrum are limited by the existing inversion algorithms and data acquisition schemes. We introduce a joint method to inverse the T1-T2 spectrum, which combines iterative truncated singular value decomposition (TSVD) and a parallel particle swarm optimization (PSO) algorithm to get fast computational speed and stable solutions. We reorganize the first kind Fredholm integral equation of two kernels to a nonlinear optimization problem with non-negative constraints, and then solve the ill-conditioned problem by the iterative TSVD. Truncating positions of the two diagonal matrices are obtained by the Akaike information criterion (AIC). With the initial values obtained by TSVD, we use a PSO with parallel structure to get the global optimal solutions with a high computational speed. We use the synthetic data with different signal to noise ratio (SNR) to test the performance of the proposed method. The result shows that the new inversion algorithm can achieve favorable solutions for signals with SNR larger than 10, and the inversion precision increases with the decrease of the components of the porous rock.
Obtaining the Bunch Shape in a Linac from Beam Spectrum Measurements
Bane, Karl LF
1999-04-14
In linacs with high single-bunch charge, and tight tolerances for energy spread and emittance growth, controlling the short-range wakefield effects becomes extremely important. The effects of the wakefields, in turn, depend on the bunch length and also on the bunch shape. It was shown in the linac of the Stanford Linear Collider (SLC), for example, that by shaping the bunch, the final rms energy spread could be greatly reduced, compared to for the standard Gaussian bunch shape[1]. Therefore, in machines with high single-bunch charge, a method of measuring bunch shape can be an important beam diagnostic. In a linac with low single-bunch charge, the longitudinal bunch shape can be obtained relatively easily from a single measurement of the beam's final energy spectrum, provided that the final to initial energy ratio is large. One merely shifts the average phase of the beam, so that it rides off-crest sufficiently to induce an energy variation that is monotonic with longitudinal position. Then, by knowing the initial and final energies, the rf wave number, and the average beam phase, one can directly map the spectrum into the bunch shape. In a linac with high single-bunch charge, however, due to the effect of the longitudinal wakefield, this method either does not work at all, or it requires such a large shift in beam phase as to become impractical. In earlier work[2],[3] it was shown that, even when wakefields are important, if one measures the final beam spectrum for two different (properly chosen) values of beam phase, then one can again obtain the bunch shape, and--as a by-product--also the form of the wakefield induced voltage; this method was then illustrated using data from the linac of the SLC. These SLC measurements, however, had been performed with the machine in a special configuration, where the current was low; in addition, the noise the data was low and the measured spectra were smooth distributions. Under normal SLC conditions, however, the currents
Long, Zac; Maltas, Jeff; Zatt, Michael C; Cheng, Jun; Alquist, Erik J; Brest, Alex; Urayama, Paul
2015-03-01
The cellular proportion of free and protein-bound NADH complexes is increasingly recognized as a metabolic indicator and biomarker. Because free and bound forms exhibit different fluorescence spectra, we consider whether autofluorescence shape sufficiently correlates with mitochondrial metabolism to be useful for monitoring in cellular suspensions. Several computational approaches for rapidly quantifying spectrum shape are used to detect Saccharomyces cereviseae response to oxygenation, and to the addition of mitochondrial functional modifiers and metabolic substrates. Observed changes appear consistent with previous studies probing free/protein-bound proportions, making this a potentially useful approach for the real-time monitoring of metabolism. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim).
Spectrum shape-analysis techniques applied to the Hanford Tank Farms spectral gamma logs
Wilson, R.D.
1997-05-01
Gamma-ray spectra acquired with high-energy resolution by the spectral gamma logging systems (SGLSs) at the U.S. Department of Energy Hanford Tank Farms, Richland, Washington, are being analyzed for spectral shape characteristics. These spectral shapes, together with a conventional peak-area analysis, enable an analyst not only to identify the gamma-emitting species but also to determine in many instances its spatial distribution around a borehole and to identify the presence of the bremsstrahlung-producing contaminant {sup 90}Sr. The analysis relies primarily on the results of computer simulations of gamma spectra from the predominant radionuclide {sup 137}Cs for various spatial distributions. This log analysis methodology has evolved through an examination of spectral features from spectral logs taken at the SX, BY, and U Tank Farms at the Hanford Site. Initial results determined with this technique show it is possible, in most cases, to distinguish between concentrations of {sup 137}Cs. Work is continuing by experimentally measuring shape factors, incorporating spectrum shape processing in routine log analysis, and extending the techniques to additional radionuclides.
ERIC Educational Resources Information Center
Field, Charlotte; Allen, Melissa L.; Lewis, Charlie
2016-01-01
The shape bias--generalising labels to same shaped objects--has been linked to attentional learning or referential intent. We explore these origins in children with typical development (TD), autism spectrum disorders (ASD) and other developmental disorders (DD). In two conditions, a novel object was presented and either named or described.…
Dolly, S; Chen, H; Anastasio, M; Mutic, S; Li, H
2014-06-15
Purpose: To quantitatively assess the noise power spectrum (NPS) of the new, commercially released CT iterative reconstruction technique, iDose{sup 4} from Philips, to compare it with filtered back-projection techniques (FBP), and to provide clinical practice suggestions for radiation therapy. Methods: A uniform phantom was CT imaged with 120kVp tube potential over a range of mAs (250-3333). The image sets were reconstructed using two reconstruction algorithms (FBP and iDose{sup 4} with noise reduction levels 1, 3, and 6) and three reconstruction filters (standard B, smooth A, and sharp C), after which NPS variations were analyzed and compared on region of interest (ROI) sizes (16×16 to 128×128 pixels), ROI radii (0–65 mm), reconstruction algorithms, reconstruction filters, and mAs. Results: The NPS magnitude and shape depended considerably on ROI size and location for both reconstruction algorithms. Regional noise variance became more stationary as ROI size decreased, minimizing NPS artifacts. The optimal 32×32-pixel ROI size balanced the trade-off between stationary noise and adequate sampling. NPS artifacts were greatest at the center of reconstruction space and decreased with increasing ROI distance from the center. The optimal ROI position was located near the phantom's radial midpoint (∼40mm). For sharper filters, the NPS magnitude and the maximum magnitude frequency increased. Higher dose scans yielded lower NPS magnitudes for both reconstruction algorithms and all filters. Compared to FBP, the iDose{sup 4} algorithm reduced the NPS magnitude while preferentially reducing noise at mid-range spatial frequencies, altering noise texture. This reduction was more significant with increasing iDose{sup 4} noise reduction level. Conclusion: Compared to pixel standard deviation, NPS has greater clinical potential for task-based image quality assessment, describing both the magnitude and spatial frequency characteristics of image noise. While iDose{sup 4
The shape of the extragalactic cosmic ray spectrum from galaxy clusters
NASA Astrophysics Data System (ADS)
Harari, Diego; Mollerach, Silvia; Roulet, Esteban
2016-08-01
We study the diffusive escape of cosmic rays from a central source inside a galaxy cluster to obtain the suppression in the outgoing flux appearing when the confinement times get comparable or larger than the age of the sources. We also discuss the attenuation of the flux due to the interactions of the cosmic rays with the cluster medium, which can be sizeable for heavy nuclei. The overall suppression in the total cosmic ray flux expected on Earth is important to understand the shape of the extragalactic contribution to the cosmic ray spectrum for E/Z < 1 EeV . This suppression can also be relevant to interpret the results of fits to composition-sensitive observables measured at ultra-high energies.
The mutation spectrum in genomic late replication domains shapes mammalian GC content
Kenigsberg, Ephraim; Yehuda, Yishai; Marjavaara, Lisette; Keszthelyi, Andrea; Chabes, Andrei; Tanay, Amos; Simon, Itamar
2016-01-01
Genome sequence compositions and epigenetic organizations are correlated extensively across multiple length scales. Replication dynamics, in particular, is highly correlated with GC content. We combine genome-wide time of replication (ToR) data, topological domains maps and detailed functional epigenetic annotations to study the correlations between replication timing and GC content at multiple scales. We find that the decrease in genomic GC content at large scale late replicating regions can be explained by mutation bias favoring A/T nucleotide, without selection or biased gene conversion. Quantification of the free dNTP pool during the cell cycle is consistent with a mechanism involving replication-coupled mutation spectrum that favors AT nucleotides at late S-phase. We suggest that mammalian GC content composition is shaped by independent forces, globally modulating mutation bias and locally selecting on functional element. Deconvoluting these forces and analyzing them on their native scales is important for proper characterization of complex genomic correlations. PMID:27085808
Robust 9-QAM digital recovery for spectrum shaped coherent QPSK signal.
Huang, Bo; Zhang, Junwen; Yu, Jianjun; Dong, Ze; Li, Xinying; Ou, Haiyan; Chi, Nan; Liu, Wen
2013-03-25
We propose 9-ary quadrature amplitude modulation (9-QAM) data recovery for polarization multiplexing-quadrature phase shift keying (PM-QPSK) signal in presence of strong filtering to approach Nyquist bandwidth. The decision-directed least radius distance (DD-LRD) algorithm for blind equalization is used for 9-QAM recovery and intersymbol interference (ISI) compression. It shows the robustness under strong filtering to recover 9-QAM signal rather than QPSK. We demonstrate 112 Gb/s spectrum shaped PM-QPSK signal by wavelength selective switch (WSS) in a 25-GHz channel spacing Nyquist wavelength division multiplexing (NWDM). The final equalized signal is detected by maximum likelihood sequence decision (MLSD) for data bit-error-ratio (BER) measurement. Optical signal-to-noise ratio (OSNR) tolerance is improved by 0.5 dB at a BER of 1x10(-3) compared to constant modulus algorithm (CMA) plus post-filter algorithm.
Shlemov, Alex; Golyandina, Nina; Holloway, David; Spirov, Alexander
2015-01-01
In recent years, with the development of automated microscopy technologies, the volume and complexity of image data on gene expression have increased tremendously. The only way to analyze quantitatively and comprehensively such biological data is by developing and applying new sophisticated mathematical approaches. Here, we present extensions of 2D singular spectrum analysis (2D-SSA) for application to 2D and 3D datasets of embryo images. These extensions, circular and shaped 2D-SSA, are applied to gene expression in the nuclear layer just under the surface of the Drosophila (fruit fly) embryo. We consider the commonly used cylindrical projection of the ellipsoidal Drosophila embryo. We demonstrate how circular and shaped versions of 2D-SSA help to decompose expression data into identifiable components (such as trend and noise), as well as separating signals from different genes. Detection and improvement of under- and overcorrection in multichannel imaging is addressed, as well as the extraction and analysis of 3D features in 3D gene expression patterns.
Holloway, David
2015-01-01
In recent years, with the development of automated microscopy technologies, the volume and complexity of image data on gene expression have increased tremendously. The only way to analyze quantitatively and comprehensively such biological data is by developing and applying new sophisticated mathematical approaches. Here, we present extensions of 2D singular spectrum analysis (2D-SSA) for application to 2D and 3D datasets of embryo images. These extensions, circular and shaped 2D-SSA, are applied to gene expression in the nuclear layer just under the surface of the Drosophila (fruit fly) embryo. We consider the commonly used cylindrical projection of the ellipsoidal Drosophila embryo. We demonstrate how circular and shaped versions of 2D-SSA help to decompose expression data into identifiable components (such as trend and noise), as well as separating signals from different genes. Detection and improvement of under- and overcorrection in multichannel imaging is addressed, as well as the extraction and analysis of 3D features in 3D gene expression patterns. PMID:25945341
Ahn, Wonmi; Boriskina, Svetlana V; Hong, Yan; Reinhard, Björn M
2012-01-11
We introduce a new design approach for surface-enhanced Raman spectroscopy (SERS) substrates that is based on molding the optical powerflow through a sequence of coupled nanoscale optical vortices "pinned" to rationally designed plasmonic nanostructures, referred to as Vortex Nanogear Transmissions (VNTs). We fabricated VNTs composed of Au nanodiscs by electron beam lithography on quartz substrates and characterized their near- and far-field responses through combination of computational electromagnetism, and elastic and inelastic scattering spectroscopy. Pronounced dips in the far-field scattering spectra of VNTs provide experimental evidence for an efficient light trapping and circulation within the nanostructures. Furthermore, we demonstrate that VNT integration into periodic arrays of Au nanoparticles facilitates the generation of high E-field enhancements in the VNTs at multiple defined wavelengths. We show that spectrum shaping in nested VNT structures is achieved through an electromagnetic feed-mechanism driven by the coherent multiple scattering in the plasmonic arrays and that this process can be rationally controlled by tuning the array period. The ability to generate high E-field enhancements at predefined locations and frequencies makes nested VNTs interesting substrates for challenging SERS applications.
Field, Charlotte; Allen, Melissa L; Lewis, Charlie
2016-10-01
The shape bias-generalising labels to same shaped objects-has been linked to attentional learning or referential intent. We explore these origins in children with typical development (TD), autism spectrum disorders (ASD) and other developmental disorders (DD). In two conditions, a novel object was presented and either named or described. Children selected another from a shape, colour or texture match. TD children choose the shape match in both conditions, children with DD and 'high-verbal mental age' (VMA) children with ASD (language age > 4.6) did so in the name condition and 'low-VMA' children with ASD never showed the heuristic. Thus, the shape bias arises from attentional learning in atypically developing children and is delayed in ASD. PMID:25733159
Field, Charlotte; Allen, Melissa L; Lewis, Charlie
2016-10-01
The shape bias-generalising labels to same shaped objects-has been linked to attentional learning or referential intent. We explore these origins in children with typical development (TD), autism spectrum disorders (ASD) and other developmental disorders (DD). In two conditions, a novel object was presented and either named or described. Children selected another from a shape, colour or texture match. TD children choose the shape match in both conditions, children with DD and 'high-verbal mental age' (VMA) children with ASD (language age > 4.6) did so in the name condition and 'low-VMA' children with ASD never showed the heuristic. Thus, the shape bias arises from attentional learning in atypically developing children and is delayed in ASD.
NASA Astrophysics Data System (ADS)
Nazarov, Sergey A.
2007-12-01
The spectra of the elasticity and piezo-electricity systems for a solid with a sharp peak point on the boundary, which is free of traction, are not discrete. An algebraic criterion of non-empty continuous spectrum is found for the Neumann problem for rather arbitrary formally self-adjoint elliptic systems of second-order differential equations on a sharp peak-shaped domain. To cite this article: S.A. Nazarov, C. R. Mecanique 335 (2007).
Spacing and shape of random peaks in non-parametric spectrum estimates.
Thomson, D J; Haley, C L
2014-07-01
In this paper, expressions are derived for the expected number of spurious peaks in a spectrum estimate, that is, crossings above a given significance level per frequency unit, as well as the expected width of these peaks. In numerous scientific applications, spectrum estimates are used for the purpose of identifying sinusoidal or modal components, often thinning large sets of candidate frequencies with coincidence detection. Because one always expects numerous false peaks in a spectrum estimate, knowing the expected rate of false peaks helps to decide whether the number observed is abnormal and hence determine the true nature of the process. An example using solar wind data from the Advanced Composition Explorer is given where spectra display pathological numbers of significant peaks, while temporally permuted versions of the data possess spectra with the number expected for a white, Gaussian process. The permutation test is a valuable diagnostic for processes suspected to contain many line components.
The shape of the primary cosmic ray electron spectrum above 10 GeV
NASA Technical Reports Server (NTRS)
Silverberg, R. F.; Ormes, J. F.; Balasubrahmanyan, V. K.
1974-01-01
A balloon borne measurement of the cosmic ray electron spectrum above 10 GeV is reported in which two new techniques have been used to remove proton background contamination. First, the depth of the spectrometer on one of the flights was more than 40 radiation lengths, enabling hadronically and electromagnetically induced cascades to be differentiated for a subset of the data. Second, electromagnetic cascade starting points were determined to within about 0.1 radiation lengths based upon a calibration with electrons from 5.4 to 18 GeV at the Stanford Linear Accelerator. The resulting spectrum, when fitted with a power law, is steep, but the fit is marginal. A significantly better fit is achieved by assuming a model in which the spectrum is steepening in the measured region.
Evidence for cluster shape effects on the kinetic energy spectrum in thermionic emission.
Calvo, F; Lépine, F; Baguenard, B; Pagliarulo, F; Concina, B; Bordas, C; Parneix, P
2007-11-28
Experimental kinetic energy release distributions obtained for the thermionic emission from C(n) (-) clusters, 10< or =n< or =20, exhibit significant non-Boltzmann variations. Using phase space theory, these different features are analyzed and interpreted as the consequence of contrasting shapes in the daughter clusters; linear and nonlinear isomers have clearly distinct signatures. These results provide a novel indirect structural probe for atomic clusters associated with their thermionic emission spectra.
Zakari-Issoufou, A-A; Fallot, M; Porta, A; Algora, A; Tain, J L; Valencia, E; Rice, S; Bui, V M; Cormon, S; Estienne, M; Agramunt, J; Äystö, J; Bowry, M; Briz, J A; Caballero-Folch, R; Cano-Ott, D; Cucoanes, A; Elomaa, V-V; Eronen, T; Estévez, E; Farrelly, G F; Garcia, A R; Gelletly, W; Gomez-Hornillos, M B; Gorlychev, V; Hakala, J; Jokinen, A; Jordan, M D; Kankainen, A; Karvonen, P; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Molina, F; Moore, I; Perez-Cerdán, A B; Podolyák, Zs; Penttilä, H; Regan, P H; Reponen, M; Rissanen, J; Rubio, B; Shiba, T; Sonzogni, A A; Weber, C
2015-09-01
The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed. PMID:26382674
NASA Astrophysics Data System (ADS)
Zakari-Issoufou, A.-A.; Fallot, M.; Porta, A.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; ńystö, J.; Bowry, M.; Briz, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucoanes, A.; Elomaa, V.-V.; Eronen, T.; Estévez, E.; Farrelly, G. F.; Garcia, A. R.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Karvonen, P.; Kolhinen, V. S.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez-Cerdán, A. B.; Podolyák, Zs.; Penttilä, H.; Regan, P. H.; Reponen, M.; Rissanen, J.; Rubio, B.; Shiba, T.; Sonzogni, A. A.; Weber, C.
2015-09-01
The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. 92Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied 92Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.
Excitation function shape and neutron spectrum of the 7Li(p ,n )7Be reaction near threshold
NASA Astrophysics Data System (ADS)
Martín-Hernández, Guido; Mastinu, Pierfrancesco; Maggiore, Mario; Pranovi, Lorenzo; Prete, Gianfranco; Praena, Javier; Capote-Noy, Roberto; Gramegna, Fabiana; Lombardi, Augusto; Maran, Luca; Scian, Carlo; Munaron, Enrico
2016-09-01
The forward-emitted low energy tail of the neutron spectrum generated by the 7Li(p ,n )7Be reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for s -wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the 197Au(n ,γ ) cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988), 10.1103/PhysRevC.37.595] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given.
Toward a fractal spectrum approach for neutron and gamma pulse shape discrimination
NASA Astrophysics Data System (ADS)
Liu, Ming-Zhe; Liu, Bing-Qi; Zuo, Zhuo; Wang, Lei; Zan, Gui-Bin; Tuo, Xian-Guo
2016-06-01
Accurately selecting neutron signals and discriminating γ signals from a mixed radiation field is a key research issue in neutron detection. This paper proposes a fractal spectrum discrimination approach by means of different spectral characteristics of neutrons and γ rays. Figure of merit and average discriminant error ratio are used together to evaluate the discrimination effects. Different neutron and γ signals with various noise and pulse pile-up are simulated according to real data in the literature. The proposed approach is compared with the digital charge integration and pulse gradient methods. It is found that the fractal approach exhibits the best discrimination performance, followed by the digital charge integration method and the pulse gradient method, respectively. The fractal spectrum approach is not sensitive to high frequency noise and pulse pile-up. This means that the proposed approach has superior performance for effective and efficient anti-noise and high discrimination in neutron detection. Supported by the National Natural Science Foundation of China (41274109), Sichuan Youth Science and Technology Innovation Research Team (2015TD0020), Scientific and Technological Support Program of Sichuan Province (2013FZ0022), and the Creative Team Program of Chengdu University of Technology.
Gury-BenAri, Meital; Thaiss, Christoph A; Serafini, Nicolas; Winter, Deborah R; Giladi, Amir; Lara-Astiaso, David; Levy, Maayan; Salame, Tomer Meir; Weiner, Assaf; David, Eyal; Shapiro, Hagit; Dori-Bachash, Mally; Pevsner-Fischer, Meirav; Lorenzo-Vivas, Erika; Keren-Shaul, Hadas; Paul, Franziska; Harmelin, Alon; Eberl, Gérard; Itzkovitz, Shalev; Tanay, Amos; Di Santo, James P; Elinav, Eran; Amit, Ido
2016-08-25
Innate lymphoid cells (ILCs) are critical modulators of mucosal immunity, inflammation, and tissue homeostasis, but their full spectrum of cellular states and regulatory landscapes remains elusive. Here, we combine genome-wide RNA-seq, ChIP-seq, and ATAC-seq to compare the transcriptional and epigenetic identity of small intestinal ILCs, identifying thousands of distinct gene profiles and regulatory elements. Single-cell RNA-seq and flow and mass cytometry analyses reveal compartmentalization of cytokine expression and metabolic activity within the three classical ILC subtypes and highlight transcriptional states beyond the current canonical classification. In addition, using antibiotic intervention and germ-free mice, we characterize the effect of the microbiome on the ILC regulatory landscape and determine the response of ILCs to microbial colonization at the single-cell level. Together, our work characterizes the spectrum of transcriptional identities of small intestinal ILCs and describes how ILCs differentially integrate signals from the microbial microenvironment to generate phenotypic and functional plasticity.
NASA Astrophysics Data System (ADS)
Li, Bangyu; Zhang, Hui; Xu, Fanjiang
2014-03-01
This paper addresses the problem of water extraction from high resolution remote sensing images (including R, G, B, and NIR channels), which draws considerable attention in recent years. Previous work on water extraction mainly faced two difficulties. 1) It is difficult to obtain accurate position of water boundary because of using low resolution images. 2) Like all other image based object classification problems, the phenomena of "different objects same image" or "different images same object" affects the water extraction. Shadow of elevated objects (e.g. buildings, bridges, towers and trees) scattered in the remote sensing image is a typical noise objects for water extraction. In many cases, it is difficult to discriminate between water and shadow in a remote sensing image, especially in the urban region. We propose a water extraction method with two hierarchies: the statistical feature of spectral characteristic based on image segmentation and the shape feature based on shadow removing. In the first hierarchy, the Statistical Region Merging (SRM) algorithm is adopted for image segmentation. The SRM includes two key steps: one is sorting adjacent regions according to a pre-ascertained sort function, and the other one is merging adjacent regions based on a pre-ascertained merging predicate. The sort step is done one time during the whole processing without considering changes caused by merging which may cause imprecise results. Therefore, we modify the SRM with dynamic sort processing, which conducts sorting step repetitively when there is large adjacent region changes after doing merging. To achieve robust segmentation, we apply the merging region with six features (four remote sensing image bands, Normalized Difference Water Index (NDWI), and Normalized Saturation-value Difference Index (NSVDI)). All these features contribute to segment image into region of object. NDWI and NSVDI are discriminate between water and some shadows. In the second hierarchy, we adopt
Shlemov, Alex; Golyandina, Nina; Holloway, David; Spirov, Alexander
2015-01-01
Recent progress in microscopy technologies, biological markers, and automated processing methods is making possible the development of gene expression atlases at cellular-level resolution over whole embryos. Raw data on gene expression is usually very noisy. This noise comes from both experimental (technical/methodological) and true biological sources (from stochastic biochemical processes). In addition, the cells or nuclei being imaged are irregularly arranged in 3D space. This makes the processing, extraction, and study of expression signals and intrinsic biological noise a serious challenge for 3D data, requiring new computational approaches. Here, we present a new approach for studying gene expression in nuclei located in a thick layer around a spherical surface. The method includes depth equalization on the sphere, flattening, interpolation to a regular grid, pattern extraction by Shaped 3D singular spectrum analysis (SSA), and interpolation back to original nuclear positions. The approach is demonstrated on several examples of gene expression in the zebrafish egg (a model system in vertebrate development). The method is tested on several different data geometries (e.g., nuclear positions) and different forms of gene expression patterns. Fully 3D datasets for developmental gene expression are becoming increasingly available; we discuss the prospects of applying 3D-SSA to data processing and analysis in this growing field.
Preconditioned iterations to calculate extreme eigenvalues
Brand, C.W.; Petrova, S.
1994-12-31
Common iterative algorithms to calculate a few extreme eigenvalues of a large, sparse matrix are Lanczos methods or power iterations. They converge at a rate proportional to the separation of the extreme eigenvalues from the rest of the spectrum. Appropriate preconditioning improves the separation of the eigenvalues. Davidson`s method and its generalizations exploit this fact. The authors examine a preconditioned iteration that resembles a truncated version of Davidson`s method with a different preconditioning strategy.
Channeled spectropolarimetry using iterative reconstruction
NASA Astrophysics Data System (ADS)
Lee, Dennis J.; LaCasse, Charles F.; Craven, Julia M.
2016-05-01
Channeled spectropolarimeters (CSP) measure the polarization state of light as a function of wavelength. Conventional Fourier reconstruction suffers from noise, assumes the channels are band-limited, and requires uniformly spaced samples. To address these problems, we propose an iterative reconstruction algorithm. We develop a mathematical model of CSP measurements and minimize a cost function based on this model. We simulate a measured spectrum using example Stokes parameters, from which we compare conventional Fourier reconstruction and iterative reconstruction. Importantly, our iterative approach can reconstruct signals that contain more bandwidth, an advancement over Fourier reconstruction. Our results also show that iterative reconstruction mitigates noise effects, processes non-uniformly spaced samples without interpolation, and more faithfully recovers the ground truth Stokes parameters. This work offers a significant improvement to Fourier reconstruction for channeled spectropolarimetry.
ERIC Educational Resources Information Center
Field, Charlotte; Allen, Melissa L.; Lewis, Charlie
2016-01-01
We investigate the function bias--generalising words to objects with the same function--in typically developing (TD) children, children with autism spectrum disorder (ASD) and children with other developmental disorders. Across four trials, a novel object was named and its function was described and demonstrated. Children then selected the other…
Verzhbitskiy, I A; Kouzov, A P; Rachet, F; Chrysos, M
2011-06-14
A line-mixing shape analysis of the isotropic remnant Raman spectrum of the 2ν(3) overtone of CO(2) is reported at room temperature and for densities, ρ, rising up to tens of amagats. The analysis, experimental and theoretical, employs tools of non-resonant light scattering spectroscopy and uses the extended strong collision model (ESCM) to simulate the strong line mixing effects and to evidence motional narrowing. Excellent agreement at any pressure is observed between the calculated spectra and our experiment, which, along with the easy numerical implementation of the ESCM, makes this model stand out clearly above other semiempirical models for band shape calculations. The hitherto undefined, explicit ρ-dependence of the vibrational relaxation rate is given. Our study intends to improve the understanding of pressure-induced phenomena in a gas that is still in the forefront of the news.
The ITER project construction status
NASA Astrophysics Data System (ADS)
Motojima, O.
2015-10-01
The pace of the ITER project in St Paul-lez-Durance, France is accelerating rapidly into its peak construction phase. With the completion of the B2 slab in August 2014, which will support about 400 000 metric tons of the tokamak complex structures and components, the construction is advancing on a daily basis. Magnet, vacuum vessel, cryostat, thermal shield, first wall and divertor structures are under construction or in prototype phase in the ITER member states of China, Europe, India, Japan, Korea, Russia, and the United States. Each of these member states has its own domestic agency (DA) to manage their procurements of components for ITER. Plant systems engineering is being transformed to fully integrate the tokamak and its auxiliary systems in preparation for the assembly and operations phase. CODAC, diagnostics, and the three main heating and current drive systems are also progressing, including the construction of the neutral beam test facility building in Padua, Italy. The conceptual design of the Chinese test blanket module system for ITER has been completed and those of the EU are well under way. Significant progress has been made addressing several outstanding physics issues including disruption load characterization, prediction, avoidance, and mitigation, first wall and divertor shaping, edge pedestal and SOL plasma stability, fuelling and plasma behaviour during confinement transients and W impurity transport. Further development of the ITER Research Plan has included a definition of the required plant configuration for 1st plasma and subsequent phases of ITER operation as well as the major plasma commissioning activities and the needs of the accompanying R&D program to ITER construction by the ITER parties.
Sonzogni, A.; Zakari-Issoufou, A. -A.; Fallot, M.; Porta, A.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; et al
2015-03-09
The accurate determination of the emitted reactor antineutrino flux is still a major challenge for actual and future neutrino experiments at reactors, especially after the evidence of a disagreement between the measured antineutrino energy spectrum by Double Chooz, Daya Bay, and Reno and calculated antineutrino spectra obtained from the conversion of the unique integral beta spectra measured at the ILL reactor. Using nuclear data to compute reactor antineutrino spectra may help understanding this bias, with the study of the underlying nuclear physics. Summation calculations allow identifying a list of nuclei that contribute importantly to the antineutrino energy spectra emitted aftermore » the fission of ²³⁹,²⁴¹Pu and ²³⁵,²³⁸U, and whose beta decay properties might deserve new measurements. Among these nuclei, ⁹²Rb exhausts by itself about 16% of of the antineutrino energy spectrum emitted by Pressurized Water Reactors in the 5 to 8 MeV range. In this Letter, we report new Total Absorption Spectroscopy (TAS) results for this important contributor. The obtained beta feeding from ⁹²Rb shows beta intensity unobserved before in the 4.5 to 5.5 MeV energy region and gives a ground state to ground state branch of 87.5 % ± 3%. These new data induce a dramatic change in recent summation calculations where a 51% GS to GS branch was considered for ⁹²Rb, increasing the summation antineutrino spectrum in the region nearby the observed bias.The new data still have an important impact on other summation calculations in which more recent data were considered« less
Sonzogni, A.; Zakari-Issoufou, A. -A.; Fallot, M.; Porta, A.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Aysto, J.; Bowry, M.; Briz Monago, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucoanes, A.; Eloma, V.; Estvez, E.; Farrelly, G. F.; Garcia, A.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez, A.; Podolyak, Zs.; Penttil, H.; Regan, P. H.; Shiba, T.; Rissanen, J.; Rubio, B.; Weber, C.
2015-03-09
The accurate determination of the emitted reactor antineutrino flux is still a major challenge for actual and future neutrino experiments at reactors, especially after the evidence of a disagreement between the measured antineutrino energy spectrum by Double Chooz, Daya Bay, and Reno and calculated antineutrino spectra obtained from the conversion of the unique integral beta spectra measured at the ILL reactor. Using nuclear data to compute reactor antineutrino spectra may help understanding this bias, with the study of the underlying nuclear physics. Summation calculations allow identifying a list of nuclei that contribute importantly to the antineutrino energy spectra emitted after the fission of ²³⁹^{,}²⁴¹Pu and ²³⁵^{,}²³⁸U, and whose beta decay properties might deserve new measurements. Among these nuclei, ⁹²Rb exhausts by itself about 16% of of the antineutrino energy spectrum emitted by Pressurized Water Reactors in the 5 to 8 MeV range. In this Letter, we report new Total Absorption Spectroscopy (TAS) results for this important contributor. The obtained beta feeding from ⁹²Rb shows beta intensity unobserved before in the 4.5 to 5.5 MeV energy region and gives a ground state to ground state branch of 87.5 % ± 3%. These new data induce a dramatic change in recent summation calculations where a 51% GS to GS branch was considered for ⁹²Rb, increasing the summation antineutrino spectrum in the region nearby the observed bias.The new data still have an important impact on other summation calculations in which more recent data were considered
NASA Astrophysics Data System (ADS)
Cerdeño, D. G.; Peiró, M.; Robles, S.
2016-04-01
We study spectral features in the gamma-ray emission from dark matter (DM) annihilation in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), with either neutralino or right-handed (RH) sneutrino DM . We perform a series of scans over the NMSSM parameter space, compute the DM annihilation cross section into two photons and the contribution of box-shaped features, and compare them with the limits derived from the Fermi-LAT search for gamma-ray lines using the latest Pass 8 data. We implement the LHC bounds on the Higgs sector and on the masses of supersymmetric particles as well as the constraints on low-energy observables. We also consider the recent upper limits from the Fermi-LAT satellite on the continuum gamma-ray emission from dwarf spheroidal galaxies (dSphs). We show that in the case of the RH sneutrino the constraint on gamma-ray spectral features can be more stringent than the dSph bounds. This is due to the Breit-Wigner enhancement near the ubiquitous resonances with a CP even Higgs and the contribution of scalar and pseudoscalar Higgs final states to box-shaped features. By contrast, for neutralino DM, the di-photon final state is only enhanced in the resonance with a Z boson and box-shaped features are even more suppressed. Therefore, the observation of spectral features could constitute a discriminating factor between both models. In addition, we compare our results with direct DM searches, including the SuperCDMS and LUX limits on the elastic DM-nucleus scattering cross section and show that some of these scenarios would be accessible to next generation experiments. Thus, our findings strengthen the idea of complementarity among distinct DM search strategies.
NASA Astrophysics Data System (ADS)
Kumara, N. T. R. N.; Chou Chau, Yuan-Fong; Huang, Jin-Wei; Huang, Hung Ji; Lin, Chun-Ting; Chiang, Hai-Pang
2016-11-01
Simulations of surface plasmon resonance (SPR) on the near field intensity and absorption spectra of one-dimensional (1D) and two-dimensional (2D) periodic arrays of rod-shape metal nanoparticle (MNP) pairs using the finite element method (FEM) and taking into account the different core patterns for biosensor and solar cell applications are investigated. A tunable optical spectrum corresponding to the transverse SPR modes is observed. The peak resonance wavelength (λ res) can be shifted to red as the core patterns in rod-shape MNPs have been changed. We find that the 2D periodic array of core–shell MNP pairs (case 2) exhibit a red shifted SPR that can be tuned the gap enhancement and absorption efficiency simultaneously over an extended wavelength range. The tunable optical performances give us a qualitative idea of the geometrical properties of the periodic array of rod-shape MNP pairs on SPRs that can be as a promising candidate for plasmonic biosensor and solar cell applications.
Iterative consolidation of unorganized point clouds.
Liu, Shengjun; Chan, Kwan-Chung; Wang, Charlie C L
2012-01-01
Unorganized point clouds obtained from 3D shape acquisition devices usually present noise, outliers, and nonuniformities. The proposed framework consolidates unorganized points through an iterative procedure of interlaced downsampling and upsampling. Selection operations remove outliers while preserving geometric details. The framework improves the uniformity of points by moving the downsampled particles and refining point samples. Surface extrapolation fills missed regions. Moreover, an adaptive sampling strategy speeds up the iterations. Experimental results demonstrate the framework's effectiveness.
US ITER / ORNL
2016-07-12
US ITER Project Manager Ned Sauthoff, joined by Wayne Reiersen, Team Leader Magnet Systems, and Jan Berry, Team Leader Tokamak Cooling System, discuss the U.S.'s role in the ITER international collaboration.
Chen, H; Cormack, R; Bhagwat, M; Berbeco, R
2015-06-15
Purpose: Gold nanoparticles (AuNP) are multifunctional platforms ideal for drug delivery, targeted imaging and radiosensitization. We have investigated quantitative imaging of AuNPs using on board imager (OBI) cone beam computed tomography (CBCT). To this end, we also present, for the first time, a novel method for k-edge imaging of AuNP by filter-based spectral shaping. Methods: We used a digital 25 cm diameter water phantom, embedded with 3 cm spheres filled with AuNPs of different concentrations (0 mg/ml – 16 mg/ml). A poly-energetic X-ray spectrum of 140 kVp from a conventional X-ray tube is shaped by balanced K-edge filters to create an excess of photons right above the K-edge of gold at 80.7 keV. The filters consist of gold, tin, copper and aluminum foils. The phantom with appropriately assigned attenuation coefficients is forward projected onto a detector for each energy bin and then integrated. FKD reconstruction is performed on the integrated projections. Scatter, detector efficiency and noise are included. Results: We found that subtracting the results of two filter sets (Filter A:127 µm gold foil with 254 µm tin, 330 µm copper and 1 mm aluminum, and Filter B: 635 µm tin with 264 µm copper and 1 mm aluminum), provides substantial image contrast. The resulting filtered spectra match well below 80.7 keV, while maintaining sufficient X-ray quanta just above that. Voxel intensities of AuNP containing spheres increase linearly with AuNP concentration. K-edge imaging provides 18% more sensitivity than the tin filter alone, and 38% more sensitivity than the gold filter alone. Conclusion: We have shown that it is feasible to quantitatively detect AuNP distributions in a patient-sized phantom using clinical CBCT and K-edge spectral shaping.
G. Douglas Loesser, et. al.
2012-09-21
The ITER Diagnostic Division is responsible for designing and procuring the First Wall Blankets that are mounted on the vacuum vessel port plugs at both the upper and equatorial levels This paper will discuss the effects of the diagnostic aperture shape and configuration on the coolant circuit design. The DFW design is driven in large part by the need to conform the coolant arrangement to a wide variety of diagnostic apertures combined with the more severe heating conditions at the surface facing the plasma, the first wall. At the first wall, a radiant heat flux of 35W/cm2 combines with approximate peak volumetric heating rates of 8W/cm3 (equatorial ports) and 5W/cm3 (upper ports). Here at the FW, a fast thermal response is desirable and leads to a thin element between the heat flux and coolant. This requirement is opposed by the wish for a thicker FW element to accommodate surface erosion and other off-normal plasma events.
NASA Astrophysics Data System (ADS)
Abdou, M.; Baker, C.; Casini, G.
1991-07-01
The International Thermonuclear Experimental Reactor (ITER) was designed to operate in two phases. The first phase, which lasts for 6 years, is devoted to machine checkout and physics testing. The second phase lasts for 8 years and is devoted primarily to technology testing. This report describes the technology test program development for ITER, the ancillary equipment outside the torus necessary to support the test modules, the international collaboration aspects of conducting the test program on ITER, the requirements on the machine major parameters and the R and D program required to develop the test modules for testing in ITER.
ITER Plasma Control System Development
NASA Astrophysics Data System (ADS)
Snipes, Joseph; ITER PCS Design Team
2015-11-01
The development of the ITER Plasma Control System (PCS) continues with the preliminary design phase for 1st plasma and early plasma operation in H/He up to Ip = 15 MA in L-mode. The design is being developed through a contract between the ITER Organization and a consortium of plasma control experts from EU and US fusion laboratories, which is expected to be completed in time for a design review at the end of 2016. This design phase concentrates on breakdown including early ECH power and magnetic control of the poloidal field null, plasma current, shape, and position. Basic kinetic control of the heating (ECH, ICH, NBI) and fueling systems is also included. Disruption prediction, mitigation, and maintaining stable operation are also included because of the high magnetic and kinetic stored energy present already for early plasma operation. Support functions for error field topology and equilibrium reconstruction are also required. All of the control functions also must be integrated into an architecture that will be capable of the required complexity of all ITER scenarios. A database is also being developed to collect and manage PCS functional requirements from operational scenarios that were defined in the Conceptual Design with links to proposed event handling strategies and control algorithms for initial basic control functions. A brief status of the PCS development will be presented together with a proposed schedule for design phases up to DT operation.
ERIC Educational Resources Information Center
Dobbs, David E.
2009-01-01
The main purpose of this note is to present and justify proof via iteration as an intuitive, creative and empowering method that is often available and preferable as an alternative to proofs via either mathematical induction or the well-ordering principle. The method of iteration depends only on the fact that any strictly decreasing sequence of…
Shapes of Interacting RNA Complexes
Fu, Benjamin M.M.
2014-01-01
Abstract Shapes of interacting RNA complexes are studied using a filtration via their topological genus. A shape of an RNA complex is obtained by (iteratively) collapsing stacks and eliminating hairpin loops. This shape projection preserves the topological core of the RNA complex, and for fixed topological genus there are only finitely many such shapes. Our main result is a new bijection that relates the shapes of RNA complexes with shapes of RNA structures. This allows for computing the shape polynomial of RNA complexes via the shape polynomial of RNA structures. We furthermore present a linear time uniform sampling algorithm for shapes of RNA complexes of fixed topological genus. PMID:25075750
Perl Modules for Constructing Iterators
NASA Technical Reports Server (NTRS)
Tilmes, Curt
2009-01-01
The Iterator Perl Module provides a general-purpose framework for constructing iterator objects within Perl, and a standard API for interacting with those objects. Iterators are an object-oriented design pattern where a description of a series of values is used in a constructor. Subsequent queries can request values in that series. These Perl modules build on the standard Iterator framework and provide iterators for some other types of values. Iterator::DateTime constructs iterators from DateTime objects or Date::Parse descriptions and ICal/RFC 2445 style re-currence descriptions. It supports a variety of input parameters, including a start to the sequence, an end to the sequence, an Ical/RFC 2445 recurrence describing the frequency of the values in the series, and a format description that can refine the presentation manner of the DateTime. Iterator::String constructs iterators from string representations. This module is useful in contexts where the API consists of supplying a string and getting back an iterator where the specific iteration desired is opaque to the caller. It is of particular value to the Iterator::Hash module which provides nested iterations. Iterator::Hash constructs iterators from Perl hashes that can include multiple iterators. The constructed iterators will return all the permutations of the iterations of the hash by nested iteration of embedded iterators. A hash simply includes a set of keys mapped to values. It is a very common data structure used throughout Perl programming. The Iterator:: Hash module allows a hash to include strings defining iterators (parsed and dispatched with Iterator::String) that are used to construct an overall series of hash values.
Donne, A. J. H.; Hellermann, M. G. von; Barnsley, R.
2008-10-22
After an introduction into the specific challenges in the field of diagnostics for ITER (specifically high level of nuclear radiation, long pulses, high fluxes of particles to plasma facing components, need for reliability and robustness), an overview will be given of the spectroscopic diagnostics foreseen for ITER. The paper will describe both active neutral-beam based diagnostics as well as passive spectroscopic diagnostics operating in the visible, ultra-violet and x-ray spectral regions.
ITER convertible blanket evaluation
Wong, C.P.C.; Cheng, E.
1995-09-01
Proposed International Thermonuclear Experimental Reactor (ITER) convertible blankets were reviewed. Key design difficulties were identified. A new particle filter concept is introduced and key performance parameters estimated. Results show that this particle filter concept can satisfy all of the convertible blanket design requirements except the generic issue of Be blanket lifetime. If the convertible blanket is an acceptable approach for ITER operation, this particle filter option should be a strong candidate.
NASA Astrophysics Data System (ADS)
Stambaugh, R. D.
2006-04-01
Stars are powered by fusion, the energy released by fusing together light nuclei, using gravitational confinement of plasma. Fusion on earth will be done in a 100 million degree plasma made of deuterium and tritium and confined by magnetic fields or inertia. The worldwide fusion research community will construct ITER, the first experiment that will burn a DT plasma by copious fusion reactions. ITER's nominal goal is to create 500 MW of fusion power. An energy gain of 10 will mean the plasma is dominantly self-heated by the fusion-produced alpha particles. ITER's all superconducting magnet technology and steady-state heat removal technology will enable nominal 400 s pulses to allow the study of burning plasmas on the longest intrinsic timescale of the confined plasma - diffusive redistribution of the electrical currents in the plasma. The advances in magnetic confinement physics that have led to this opportunity will be described, as well as the research opportunities afforded by ITER. The physics of confining stable plasmas and heating them will produce the high gain state in ITER. Sustained burn will come from the physics of controlling currents in plasmas and how the hot plasma is interfaced to its room temperature surroundings. ITER will provide our first experience with how fusion plasma self-heating will profoundly affect the complex, interlinked physical processes that occur in confined plasmas.
NASA Astrophysics Data System (ADS)
Shimomura, Yasuo
The ITER Project has been significantly developed in the past years in preparation for its construction. The ITER Negotiators have developed a draft Joint Implementation Agreement (JIA), ready for completion following the nomination of the Project’s Director General (DG). The ITER International Team and Participant Teams have continued technical and organizational preparations. The actual construction will be able to start immediately after the international ITER organization will be established, following signature of the JIA. The Project is now strongly supported by all the participants as well as by the scientific community with the final high-level negotiations, focused on siting and the concluding details of cost sharing, started in December 2003. The EU, with Cadarache, and Japan, with Rokkasho, have both promised large contributions to the project to strongly support their construction site proposals. The extent to which they both wish to host the ITER facility is such that large contributions to a broader collaboration among the Parties are also proposed by them. This covers complementary activities to help accelerate fusion development towards a viable power source, as well as may allow the Participants to reach a conclusion on ITER siting.
Lanczos iterated time-reversal.
Oberai, Assad A; Feijóo, Gonzalo R; Barbone, Paul E
2009-02-01
A new iterative time-reversal algorithm capable of identifying and focusing on multiple scatterers in a relatively small number of iterations is developed. It is recognized that the traditional iterated time-reversal method is based on utilizing power iterations to determine the dominant eigenpairs of the time-reversal operator. The convergence properties of these iterations are known to be suboptimal. Motivated by this, a new method based on Lanczos iterations is developed. In several illustrative examples it is demonstrated that for the same number of transmitted and received signals, the Lanczos iterations based approach is substantially more accurate. PMID:19206835
Saadd, Y.
1994-12-31
In spite of the tremendous progress achieved in recent years in the general area of iterative solution techniques, there are still a few obstacles to the acceptance of iterative methods in a number of applications. These applications give rise to very indefinite or highly ill-conditioned non Hermitian matrices. Trying to solve these systems with the simple-minded standard preconditioned Krylov subspace methods can be a frustrating experience. With the mathematical and physical models becoming more sophisticated, the typical linear systems which we encounter today are far more difficult to solve than those of just a few years ago. This trend is likely to accentuate. This workshop will discuss (1) these applications and the types of problems that they give rise to; and (2) recent progress in solving these problems with iterative methods. The workshop will end with a hopefully stimulating panel discussion with the speakers.
Rescheduling with iterative repair
NASA Technical Reports Server (NTRS)
Zweben, Monte; Davis, Eugene; Daun, Brian; Deale, Michael
1992-01-01
This paper presents a new approach to rescheduling called constraint-based iterative repair. This approach gives our system the ability to satisfy domain constraints, address optimization concerns, minimize perturbation to the original schedule, produce modified schedules, quickly, and exhibits 'anytime' behavior. The system begins with an initial, flawed schedule and then iteratively repairs constraint violations until a conflict-free schedule is produced. In an empirical demonstration, we vary the importance of minimizing perturbation and report how fast the system is able to resolve conflicts in a given time bound. We also show the anytime characteristics of the system. These experiments were performed within the domain of Space Shuttle ground processing.
Fourier mode analysis of source iteration in spatially periodic media
Zika, M.R.; Larsen, E.W.
1998-12-31
The standard Fourier mode analysis is an indispensable tool when designing acceleration techniques for transport iterations; however, it requires the assumption of a homogeneous infinite medium. For problems of practical interest, material heterogeneities may significantly impact iterative performance. Recent work has applied a Fourier analysis to the discretized two-dimensional transport operator with heterogeneous material properties. The results of these analyses may be difficult to interpret because the heterogeneity effects are inherently coupled to the discretization effects. Here, the authors describe a Fourier analysis of source iteration (SI) that allows the calculation of the eigenvalue spectrum for the one-dimensional continuous transport operator with spatially periodic heterogeneous media.
Dr. Norbert Holtkamp
2016-07-12
ITER (in Latin âthe wayâ) is designed to demonstrate the scientific and technological feasibility of fusion energy. Fusion is the process by which two light atomic nuclei combine to form a heavier over one and thus release energy. In the fusion process two isotopes of hydrogen â deuterium and tritium â fuse together to form a helium atom and a neutron. Thus fusion could provide large scale energy production without greenhouse effects; essentially limitless fuel would be available all over the world. The principal goals of ITER are to generate 500 megawatts of fusion power for periods of 300 to 500 seconds with a fusion power multiplication factor, Q, of at least 10. Q ? 10 (input power 50 MW / output power 500 MW). The ITER Organization was officially established in Cadarache, France, on 24 October 2007. The seven members engaged in the project â China, the European Union, India, Japan, Korea, Russia and the United States â represent more than half the worldâs population. The costs for ITER are shared by the seven members. The cost for the construction will be approximately 5.5 billion Euros, a similar amount is foreseen for the twenty-year phase of operation and the subsequent decommissioning.
ERIC Educational Resources Information Center
Muench, Donald L.
2007-01-01
The problem of angle trisection continues to fascinate people even though it has long been known that it can't be done with straightedge and compass alone. However, for practical purposes, a good iterative procedure can get you as close as you want. In this note, we present such a procedure. Using only straightedge and compass, our procedure…
Duff, I.
1994-12-31
This workshop focuses on kernels for iterative software packages. Specifically, the three speakers discuss various aspects of sparse BLAS kernels. Their topics are: `Current status of user lever sparse BLAS`; Current status of the sparse BLAS toolkit`; and `Adding matrix-matrix and matrix-matrix-matrix multiply to the sparse BLAS toolkit`.
Hogan, J.T.; Uckan, N.A.
1990-01-01
The MHD stability limits to the ITER operational space have been examined with the PEST ideal stability code. Constraints on ITER operation have been examined for the nominal operational scenarios and for possible design variants. Rather than rely on evaluation of a relatively small number of sample cases, the approach has been to construct an approximation to the overall operational space, and to compare this with the observed limits in high-{beta} tokamaks. An extensive database with {approximately}20,000 stability results has been compiled for use by the ITER design team. Results from these studies show that the design values of the Troyon factor (g {approximately} 2.5 for ignition studies, and g {approximately} 3 for the technology phase) which are based on present experiments, are also expected to be attainable for ITER conditions, for which the configuration and wall-stabilisation environment differ from those in present experiments. Strongly peaked pressure profiles lead to degraded high-{beta} performance. Values of g {approximately} 4 are found for higher safety factor (q {sub {Psi}} {le} 4) than that of the present design (q{sub {Psi}} {approximately} 3). Profiles with q(0) < 1 are shown to give g {approximately} 2.5, if the current density profile provides optimum shear. The overall operational spaces are presented for g-q{sub {Psi}}, q{sub {Psi}}-1{sub i}, q-{alpha}{sub p} and l{sub i}-q{sub {psi}}.
None
2016-07-12
There are many voices calling for a future of abundant clean energy. The choices are difficult and the challenges daunting. How will we get there? The National Renewable Energy Laboratory integrates the entire spectrum of innovation including fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. The innovation process at NREL is interdependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.
Barnes, C.W.; Loughlin, M.J.; Nishitani, Takeo
1996-04-29
There are three primary goals for the Neutron Activation system for ITER: maintain a robust relative measure of fusion power with stability and high dynamic range (7 orders of magnitude); allow an absolute calibration of fusion power (energy); and provide a flexible and reliable system for materials testing. The nature of the activation technique is such that stability and high dynamic range can be intrinsic properties of the system. It has also been the technique that demonstrated (on JET and TFTR) the highest accuracy neutron measurements in DT operation. Since the gamma-ray detectors are not located on the tokamak and are therefore amenable to accurate characterization, and if material foils are placed very close to the ITER plasma with minimum scattering or attenuation, high overall accuracy in the fusion energy production (7--10%) should be achievable on ITER. In the paper, a conceptual design is presented. A system is shown to be capable of meeting these three goals, also detailed design issues remain to be solved.
Neutron Flux Spectra Determination by Multiple Foil Activation - Iterative Method.
1994-07-08
Version 00 Neutron energy spectra are determined by an analysis of experimental activation detector data. As with the original CCC-112/SAND-II program, which was developed at Air Force Weapons Laboratory, this code system consists of four modules, CSTAPE, SLACTS, SLATPE, and SANDII. The first three modules pre-process the dosimetry cross sections and the trial function spectrum library. The last module, SANDII, actually performs the iterative spectrum characterization.
Dixon, William V.; Chayer, Pierre E-mail: chayer@stsci.edu
2013-08-10
The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Ly{beta}, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 A and a deep absorption feature at 1072 A; none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s {sup 2} 2p {sup 3} {sup 2} D {sup 0} and {sup 2} P {sup 0}). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.
NASA Astrophysics Data System (ADS)
Dixon, William V.; Chayer, Pierre
2013-08-01
The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Lyβ, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 Å and a deep absorption feature at 1072 Å none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s 2 2p 3 2 D 0 and 2 P 0). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.
Iterative most likely oriented point registration.
Billings, Seth; Taylor, Russell
2014-01-01
A new algorithm for model based registration is presented that optimizes both position and surface normal information of the shapes being registered. This algorithm extends the popular Iterative Closest Point (ICP) algorithm by incorporating the surface orientation at each point into both the correspondence and registration phases of the algorithm. For the correspondence phase an efficient search strategy is derived which computes the most probable correspondences considering both position and orientation differences in the match. For the registration phase an efficient, closed-form solution provides the maximum likelihood rigid body alignment between the oriented point matches. Experiments by simulation using human femur data demonstrate that the proposed Iterative Most Likely Oriented Point (IMLOP) algorithm has a strong accuracy advantage over ICP and has increased ability to robustly identify a successful registration result.
Electrical optimization of the ICH antenna array for ITER
Ryan, P.M.; Swain, D.W.; Carter, M.D.; Taylor, D.J.; Bosia, G.
1997-08-01
The present design of the ITER ICH antenna array comprises two poloidal by four toroidal current elements in each of four ports.Each current element forms a resonant double loop (RDL) with power fed to a pretuned matchpoint on the strap; the matching is accomplished using slow-wave transmission lines as adjustable shorted-stub tuners on either end of the current strap. The power requirement is 12.5 MW per port over the frequency range of 40--70 MHz, with extended operation to 80 MHz desirable. The antenna design optimization process includes (1) strap shaping to minimize strap voltages and rf E-fields along B-field lines and (2) frame/Faraday shield geometry design to improve plasma coupling, wave spectrum directivity, and phase control. For the ignited plasma parameters, the optimized array design delivers full power over the ranges of 40--80 MHz in frequency and 0{degree} to 180{degree} in phase. The maximum strap voltage is 41 kV and the maximum parallel E-field is 16 kV/cm for the worst case over these ranges. The array directivity for current drive operation is calculated to be close to 80%.
Adaptive iterative reconstruction
NASA Astrophysics Data System (ADS)
Bruder, H.; Raupach, R.; Sunnegardh, J.; Sedlmair, M.; Stierstorfer, K.; Flohr, T.
2011-03-01
It is well known that, in CT reconstruction, Maximum A Posteriori (MAP) reconstruction based on a Poisson noise model can be well approximated by Penalized Weighted Least Square (PWLS) minimization based on a data dependent Gaussian noise model. We study minimization of the PWLS objective function using the Gradient Descent (GD) method, and show that if an exact inverse of the forward projector exists, the PWLS GD update equation can be translated into an update equation which entirely operates in the image domain. In case of non-linear regularization and arbitrary noise model this means that a non-linear image filter must exist which solves the optimization problem. In the general case of non-linear regularization and arbitrary noise model, the analytical computation is not trivial and might lead to image filters which are computationally very expensive. We introduce a new iteration scheme in image space, based on a regularization filter with an anisotropic noise model. Basically, this approximates the statistical data weighting and regularization in PWLS reconstruction. If needed, e.g. for compensation of the non-exactness of backprojector, the image-based regularization loop can be preceded by a raw data based loop without regularization and statistical data weighting. We call this combined iterative reconstruction scheme Adaptive Iterative Reconstruction (AIR). It will be shown that in terms of low-contrast visibility, sharpness-to-noise and contrast-to-noise ratio, PWLS and AIR reconstruction are similar to a high degree of accuracy. In clinical images the noise texture of AIR is also superior to the more artificial texture of PWLS.
Quantum iterated function systems.
Łoziński, Artur; Zyczkowski, Karol; Słomczyński, Wojciech
2003-10-01
An iterated function system (IFS) is defined by specifying a set of functions in a classical phase space, which act randomly on an initial point. In an analogous way, we define a quantum IFS (QIFS), where functions act randomly with prescribed probabilities in the Hilbert space. In a more general setting, a QIFS consists of completely positive maps acting in the space of density operators. This formalism is designed to describe certain problems of nonunitary quantum dynamics. We present exemplary classical IFSs, the invariant measure of which exhibits fractal structure, and study properties of the corresponding QIFSs and their invariant states.
Iterative Magnetometer Calibration
NASA Technical Reports Server (NTRS)
Sedlak, Joseph
2006-01-01
This paper presents an iterative method for three-axis magnetometer (TAM) calibration that makes use of three existing utilities recently incorporated into the attitude ground support system used at NASA's Goddard Space Flight Center. The method combines attitude-independent and attitude-dependent calibration algorithms with a new spinning spacecraft Kalman filter to solve for biases, scale factors, nonorthogonal corrections to the alignment, and the orthogonal sensor alignment. The method is particularly well-suited to spin-stabilized spacecraft, but may also be useful for three-axis stabilized missions given sufficient data to provide observability.
MLP iterative construction algorithm
NASA Astrophysics Data System (ADS)
Rathbun, Thomas F.; Rogers, Steven K.; DeSimio, Martin P.; Oxley, Mark E.
1997-04-01
The MLP Iterative Construction Algorithm (MICA) designs a Multi-Layer Perceptron (MLP) neural network as it trains. MICA adds Hidden Layer Nodes one at a time, separating classes on a pair-wise basis, until the data is projected into a linear separable space by class. Then MICA trains the Output Layer Nodes, which results in an MLP that achieves 100% accuracy on the training data. MICA, like Backprop, produces an MLP that is a minimum mean squared error approximation of the Bayes optimal discriminant function. Moreover, MICA's training technique yields novel feature selection technique and hidden node pruning technique
NASA Astrophysics Data System (ADS)
Shibata, Hiroshi; Ozaki, Nobuhiko; Yasuda, Takuma; Ohkouchi, Shunsuke; Ikeda, Naoki; Ohsato, Hirotaka; Watanabe, Eiichiro; Sugimoto, Yoshimasa; Furuki, Kenji; Miyaji, Kunio; Hogg, Richard A.
2015-04-01
We developed a low-coherence light source based on self-assembled InAs quantum dots (QDs) with controlled emission wavelengths and applied it to optical coherence tomography (OCT) imaging. A current-driven superluminescent diode (SLD) light source including four layers of QDs exhibits a broadband (80-nm-bandwidth) emission centered at approximately 1.2 µm with a Gaussian-like spectral shape at room temperature. Spectral-domain OCT (SD-OCT) using the QD-SLD as a light source was developed and imaging with the SD-OCT was demonstrated. The axial resolution was estimated to be approximately 8 µm in air and no apparent side lobes appeared beside the point spread function, indicating the effectiveness of the QD-SLD for high-resolution, noise-reduced OCT imaging.
Conformal mapping and convergence of Krylov iterations
Driscoll, T.A.; Trefethen, L.N.
1994-12-31
Connections between conformal mapping and matrix iterations have been known for many years. The idea underlying these connections is as follows. Suppose the spectrum of a matrix or operator A is contained in a Jordan region E in the complex plane with 0 not an element of E. Let {phi}(z) denote a conformal map of the exterior of E onto the exterior of the unit disk, with {phi}{infinity} = {infinity}. Then 1/{vert_bar}{phi}(0){vert_bar} is an upper bound for the optimal asymptotic convergence factor of any Krylov subspace iteration. This idea can be made precise in various ways, depending on the matrix iterations, on whether A is finite or infinite dimensional, and on what bounds are assumed on the non-normality of A. This paper explores these connections for a variety of matrix examples, making use of a new MATLAB Schwarz-Christoffel Mapping Toolbox developed by the first author. Unlike the earlier Fortran Schwarz-Christoffel package SCPACK, the new toolbox computes exterior as well as interior Schwarz-Christoffel maps, making it easy to experiment with spectra that are not necessarily symmetric about an axis.
Darbos, C.; Henderson, M.; Gandini, F.; Albajar, F.; Bomcelli, T.; Heidinger, R.; Saibene, G.; Chavan, R.; Goodman, T.; Hogge, J. P.; Sauter, O.; Denisov, G.; Farina, D.; Kajiwara, K.; Kasugai, A.; Kobayashi, N.; Oda, Y.; Ramponi, G.
2009-11-26
A 26 MW Electron Cyclotron Heating and Current Drive (EC H and CD) system is to be installed for ITER. The main objectives are to provide, start-up assist, central H and CD and control of MHD activity. These are achieved by a combination of two types of launchers, one located in an equatorial port and the second type in four upper ports. The physics applications are partitioned between the two launchers, based on the deposition location and driven current profiles. The equatorial launcher (EL) will access from the plasma axis to mid radius with a relatively broad profile useful for central heating and current drive applications, while the upper launchers (ULs) will access roughly the outer half of the plasma radius with a very narrow peaked profile for the control of the Neoclassical Tearing Modes (NTM) and sawtooth oscillations. The EC power can be switched between launchers on a time scale as needed by the immediate physics requirements. A revision of all injection angles of all launchers is under consideration for increased EC physics capabilities while relaxing the engineering constraints of both the EL and ULs. A series of design reviews are being planned with the five parties (EU, IN, JA, RF, US) procuring the EC system, the EC community and ITER Organization (IO). The review meetings qualify the design and provide an environment for enhancing performances while reducing costs, simplifying interfaces, predicting technology upgrades and commercial availability. In parallel, the test programs for critical components are being supported by IO and performed by the Domestic Agencies (DAs) for minimizing risks. The wide participation of the DAs provides a broad representation from the EC community, with the aim of collecting all expertise in guiding the EC system optimization. Still a strong relationship between IO and the DA is essential for optimizing the design of the EC system and for the installation and commissioning of all ex-vessel components when several
Iterated crowdsourcing dilemma game
NASA Astrophysics Data System (ADS)
Oishi, Koji; Cebrian, Manuel; Abeliuk, Andres; Masuda, Naoki
2014-02-01
The Internet has enabled the emergence of collective problem solving, also known as crowdsourcing, as a viable option for solving complex tasks. However, the openness of crowdsourcing presents a challenge because solutions obtained by it can be sabotaged, stolen, and manipulated at a low cost for the attacker. We extend a previously proposed crowdsourcing dilemma game to an iterated game to address this question. We enumerate pure evolutionarily stable strategies within the class of so-called reactive strategies, i.e., those depending on the last action of the opponent. Among the 4096 possible reactive strategies, we find 16 strategies each of which is stable in some parameter regions. Repeated encounters of the players can improve social welfare when the damage inflicted by an attack and the cost of attack are both small. Under the current framework, repeated interactions do not really ameliorate the crowdsourcing dilemma in a majority of the parameter space.
Technology Tips: Using the Iterate Command to Construct Recursive Geometric Sketches
ERIC Educational Resources Information Center
Harper, Suzanne R.; Driskell, Shannon
2006-01-01
How to iterate geometric shapes to construct Baravelle spirals and Pythagorean trees is demonstrated in this article. The "Surfing Note" sends readers to a site with applets that will generate fractals such as the Sierpinski gasket or the Koch snowflake.
Optimization of tungsten castellated structures for the ITER divertor
NASA Astrophysics Data System (ADS)
Litnovsky, A.; Hellwig, M.; Matveev, D.; Komm, M.; van den Berg, M.; De Temmerman, G.; Rudakov, D.; Ding, F.; Luo, G.-N.; Krieger, K.; Sugiyama, K.; Pitts, R. A.; Petersson, P.
2015-08-01
In ITER, the plasma-facing components (PFCs) of the first wall and the divertor armor will be castellated to improve their thermo-mechanical stability and to limit forces due to induced currents. The fuel accumulation in the gaps may significantly contribute to the in-vessel fuel inventory. Castellation shaping may be the most straightforward way to minimize the fuel inventory and to alleviate the thermal loads onto castellations. A new castellation shape was proposed and comparative modeling of conventional (rectangular) and shaped castellation was performed for ITER conditions. Shaped castellation was predicted to be capable to operate under stationary heat load of 20 MW/m2. An 11-fold decrease of beryllium (Be) content in the gaps of the shaped cells alone with a 7-fold decrease of carbon content was predicted. In order to validate the predictive capabilities of modeling tools used for ITER conditions, the dedicated modeling with the same codes was made for existing tokamaks and benchmarked with the results of multi-machine experiments. For the castellations exposed in TEXTOR and DIII-D, the carbon amount in the gaps of shaped cells was 1.9-2.3 times smaller than that of rectangular ones. Modeling for TEXTOR conditions yielded to 1.5-fold decrease of carbon content in the gaps of shaped castellation outlining fair agreement with the experiment. At the same time, a number of processes, like enhanced erosion of molten layer yet need to be implemented in the codes in order to increase the accuracy of predictions for ITER.
A study of core Thomson scattering measurements in ITER using a multi-laser approach
NASA Astrophysics Data System (ADS)
Kurskiev, G. S.; Sdvizhenskii, P. A.; Bassan, M.; Andrew, P.; Bazhenov, A. N.; Bukreev, I. M.; Chernakov, P. V.; Kochergin, M. M.; Kukushkin, A. B.; Kukushkin, A. S.; Mukhin, E. E.; Razdobarin, A. G.; Samsonov, D. S.; Semenov, V. V.; Tolstyakov, S. Yu.; Kajita, S.; Masyukevich, S. V.
2015-05-01
The electron component is the main channel for anomalous power loss and the main indicator of transient processes in the tokamak plasma. The electron temperature and density profiles mainly determine the operational mode of the machine. This imposes demanding requirements on the precision and on the spatial and temporal resolution of the Thomson scattering (TS) measurements. Measurements of such high electron temperature with good accuracy in a large fusion device such as ITER using TS encounter a number of physical problems. The 40 keV TS spectrum has a significant blue shift. Due to the transmission functions of the fibres and to their darkening that can occur under a strong neutron irradiation, the operational wavelength range is bounded on the blue side. For example, high temperature measurements become impossible with the 1064 nm probing wavelength since the TS signal within the boundaries of the operational window weakly depends on Te. The second problem is connected with the TS calibration. The TS system for a large fusion machine like ITER will have a set of optical components inaccessible for maintenance, and their spectral characteristics may change with time. Since the present concept of the TS system for ITER relies on the classical approach to measuring the shape of the scattered spectra using wide spectral channels, the diagnostic will be very sensitive to the changes in the optical transmission. The third complication is connected with the deviation of the electron velocity distribution function from a Maxwellian that can happen under a strong ECRH/ECCD, and it may additionally hamper the measurements. This paper analyses the advantages of a ‘multi-laser approach’ implementation for the current design of the core TS system. Such an approach assumes simultaneous plasma probing with different wavelengths that allows the measurement accuracy to be improved significantly and to perform the spectral calibration of the TS system. Comparative analysis
NASA Astrophysics Data System (ADS)
Jaeger, E. F.; Berry, L. A.; Myra, J. R.
2006-10-01
Fast magnetosonic waves in the ion cyclotron range of frequencies (ICRF) can convert to much shorter wavelength modes such as ion Bernstein waves (IBW) and ion cyclotron waves (ICW) [1]. These modes are potentially useful for plasma control through the generation of localized currents and sheared flows. As part of the SciDAC Center for Simulation of Wave-Plasma Interactions project, the AORSA global-wave solver [2] has been ported to the new, dual-core Cray XT-3 (Jaguar) at ORNL where it demonstrates excellent scaling with the number of processors. Preliminary calculations using 4096 processors have allowed the first full-wave simulations of mode conversion in ITER. Mode conversion from the fast wave to the ICW is observed in mixtures of deuterium, tritium and helium3 at 53 MHz. The resulting flow velocity and electric field shear will be calculated. [1] F.W. Perkins, Nucl. Fusion 17, 1197 (1977). [2] E.F. Jaeger, L.A. Berry, J.R. Myra, et al., Phys. Rev. Lett. 90, 195001-1 (2003).
Gamma ray spectrometer for ITER
Gin, D.; Chugunov, I.; Shevelev, A.; Khilkevitch, E.; Doinikov, D.; Naidenov, V.; Pasternak, A.; Polunovsky, I.; Kiptily, V.
2014-08-21
Gamma diagnostics is considered to be primary for the confined α-particles and runaway electrons measurements on ITER. The gamma spectrometer will be embedded into a neutron dump of the ITER Neutral Particle Analyzer diagnostic complex. It will supplement NPA measurements on the fuel isotope ratio and confined alphas/fast ions. In this paper an update on ITER gamma spectrometer developments is given. A new geometry of the system is described and detailed analysis of expected signals for the spectrometer is presented.
... the Zellweger spectrum result from defects in the assembly of a cellular structure called the peroxisome, and ... Zellweger spectrum are caused by defects in the assembly of the peroxisome. There are at least 12 ...
Evaluation of ITER MSE Viewing Optics
Allen, S; Lerner, S; Morris, K; Jayakumar, J; Holcomb, C; Makowski, M; Latkowski, J; Chipman, R
2007-03-26
image that then was relayed out of the port plug with more ideal (dielectric) mirrors. Engineering models of the optics, port plug, and neutral beam geometry were also created, using the CATIA ITER models. Two video conference calls with the USIPO provided valuable design guidelines, such as the minimum distance of the first optic from the plasma. A second focus of the project was the calibration of the system. Several different techniques are proposed, both before and during plasma operation. Fixed and rotatable polarizers would be used to characterize the system in the no-plasma case. Obtaining the full modulation spectrum from the polarization analyzer allows measurement of polarization effects and also MHD plasma phenomena. Light from neutral beam interaction with deuterium gas (no plasma) has been found useful to determine the wavelength of each spatial channel. The status of the optical design for the edge (upper) and core (lower) systems is included in the following figure. Several issues should be addressed by a follow-on study, including whether the optical labyrinth has sufficient neutron shielding and a detailed polarization characterization of actual mirrors.
NASA Astrophysics Data System (ADS)
Hasselmann, Klaus; Hasselmann, Susanne
1991-06-01
A new, closed nonlinear integral transformation relation is derived describing the mapping of a two-dimensional ocean wave spectrum into a synthetic aperture radar (SAR) image spectrum. The general integral relation is expanded in a power series with respect to orders of nonlinearity and velocity bunching. The individual terms of the series can be readily computed using fast Fourier transforms. The convergence of the series is rapid. The series expansion is also useful in identifying the different contributions to the net imaging process, consisting of the real aperture radar (RAR) cross-section modulation, the nonlinear motion (velocity bunching) effects, and their various interaction products. The lowest term of the expansion with respect to nonlinearity order yields a simple quasi-linear approximate mapping relation consisting of the standard linear SAR modulation expression multiplied by an additional nonlinear Gaussian azimuthal cutoff factor. The cutoff scale is given by the rms azimuthal (velocity bunching) displacement. The same cutoff factor applies to all terms of the power series expansion. The nonlinear mapping relation is inverted using a standard first-guess wave spectrum as regularization term. This is needed to overcome the basic 180° mapping ambiguity and the loss of information beyond the azimuthal cutoff. The inversion is solved numerically using an iteration technique based on the successive application of the explicit solution for the quasi-linear mapping approximation, with interposed corrections invoking the full nonlinear mapping expression. A straightforward application of this technique, however, generally yields unrealistic discontinuities of the best fit wave spectrum in the transition region separating the low azimuthal wave number domain, in which useful SAR information is available and the wave spectrum is modified, from the high azimuthal wave number region beyond the azimuthal cutoff, where the first-guess wave spectrum is retained
Nuclear Analysis of an ITER Blanket Module
NASA Astrophysics Data System (ADS)
Chiovaro, P.; Di Maio, P. A.; Parrinello, V.
2013-08-01
ITER blanket system is the reactor's plasma-facing component, it is mainly devoted to provide the thermal and nuclear shielding of the Vacuum Vessel and external ITER components, being intended also to act as plasma limiter. It consists of 440 individual modules which are located in the inboard, upper and outboard regions of the reactor. In this paper attention has been focused on to a single outboard blanket module located in the equatorial zone, whose nuclear response under irradiation has been investigated following a numerical approach based on the Monte Carlo method and adopting the MCNP5 code. The main features of this blanket module nuclear behaviour have been determined, paying particular attention to energy and spatial distribution of the neutron flux and deposited nuclear power together with the spatial distribution of its volumetric density. Moreover, the neutronic damage of the structural material has also been investigated through the evaluation of displacement per atom and helium and hydrogen production rates. Finally, an activation analysis has been performed with FISPACT inventory code using, as input, the evaluated neutron spectrum to assess the module specific activity and contact dose rate after irradiation under a specific operating scenario.
Ablikim, M; Achasov, M N; Ahmed, S; Ai, X C; Albayrak, O; Albrecht, M; Ambrose, D J; Amoroso, A; An, F F; An, Q; Bai, J Z; Baldini Ferroli, R; Ban, Y; Bennett, D W; Bennett, J V; Berger, N; Bertani, M; Bettoni, D; Bian, J M; Bianchi, F; Boger, E; Boyko, I; Briere, R A; Cai, H; Cai, X; Cakir, O; Calcaterra, A; Cao, G F; Cetin, S A; Chang, J F; Chelkov, G; Chen, G; Chen, H S; Chen, H Y; Chen, J C; Chen, M L; Chen, S; Chen, S J; Chen, X; Chen, X R; Chen, Y B; Cheng, H P; Chu, X K; Cibinetto, G; Dai, H L; Dai, J P; Dbeyssi, A; Dedovich, D; Deng, Z Y; Denig, A; Denysenko, I; Destefanis, M; De Mori, F; Ding, Y; Dong, C; Dong, J; Dong, L Y; Dong, M Y; Dou, Z L; Du, S X; Duan, P F; Fan, J Z; Fang, J; Fang, S S; Fang, X; Fang, Y; Farinelli, R; Fava, L; Fedorov, O; Feldbauer, F; Felici, G; Feng, C Q; Fioravanti, E; Fritsch, M; Fu, C D; Gao, Q; Gao, X L; Gao, X Y; Gao, Y; Gao, Z; Garzia, I; Goetzen, K; Gong, L; Gong, W X; Gradl, W; Greco, M; Gu, M H; Gu, Y T; Guan, Y H; Guo, A Q; Guo, L B; Guo, R P; Guo, Y; Guo, Y P; Haddadi, Z; Hafner, A; Han, S; Hao, X Q; Harris, F A; He, K L; Heinsius, F H; Held, T; Heng, Y K; Holtmann, T; Hou, Z L; Hu, C; Hu, H M; Hu, J F; Hu, T; Hu, Y; Huang, G S; Huang, Y P; Huang, J S; Huang, X T; Huang, X Z; Huang, Y; Huang, Z L; Hussain, T; Ji, Q; Ji, Q P; Ji, X B; Ji, X L; Jiang, L W; Jiang, X S; Jiang, X Y; Jiao, J B; Jiao, Z; Jin, D P; Jin, S; Johansson, T; Julin, A; Kalantar-Nayestanaki, N; Kang, X L; Kang, X S; Kavatsyuk, M; Ke, B C; Kiese, P; Kliemt, R; Kloss, B; Kolcu, O B; Kopf, B; Kornicer, M; Kupsc, A; Kühn, W; Lange, J S; Lara, M; Larin, P; Leithoff, H; Leng, C; Li, C; Li, Cheng; Li, D M; Li, F; Li, F Y; Li, G; Li, H B; Li, H J; Li, J C; Li, Jin; Li, K; Li, K; Li, Lei; Li, P R; Li, Q Y; Li, T; Li, W D; Li, W G; Li, X L; Li, X N; Li, X Q; Li, Y B; Li, Z B; Liang, H; Liang, Y F; Liang, Y T; Liao, G R; Lin, D X; Liu, B; Liu, B J; Liu, C X; Liu, D; Liu, F H; Liu, Fang; Liu, Feng; Liu, H B; Liu, H H; Liu, H H; Liu, H M; Liu, J; Liu, J B; Liu, J P; Liu, J Y; Liu, K; Liu, K Y; Liu, L D; Liu, P L; Liu, Q; Liu, S B; Liu, X; Liu, Y B; Liu, Y Y; Liu, Z A; Liu, Zhiqing; Loehner, H; Lou, X C; Lu, H J; Lu, J G; Lu, Y; Lu, Y P; Luo, C L; Luo, M X; Luo, T; Luo, X L; Lyu, X R; Ma, F C; Ma, H L; Ma, L L; Ma, M M; Ma, Q M; Ma, T; Ma, X N; Ma, X Y; Ma, Y M; Maas, F E; Maggiora, M; Malik, Q A; Mao, Y J; Mao, Z P; Marcello, S; Messchendorp, J G; Mezzadri, G; Min, J; Min, T J; Mitchell, R E; Mo, X H; Mo, Y J; Morales Morales, C; Muchnoi, N Yu; Muramatsu, H; Musiol, P; Nefedov, Y; Nerling, F; Nikolaev, I B; Ning, Z; Nisar, S; Niu, S L; Niu, X Y; Olsen, S L; Ouyang, Q; Pacetti, S; Pan, Y; Patteri, P; Pelizaeus, M; Peng, H P; Peters, K; Pettersson, J; Ping, J L; Ping, R G; Poling, R; Prasad, V; Qi, H R; Qi, M; Qian, S; Qiao, C F; Qin, L Q; Qin, N; Qin, X S; Qin, Z H; Qiu, J F; Rashid, K H; Redmer, C F; Ripka, M; Rong, G; Rosner, Ch; Ruan, X D; Sarantsev, A; Savrié, M; Schnier, C; Schoenning, K; Schumann, S; Shan, W; Shao, M; Shen, C P; Shen, P X; Shen, X Y; Sheng, H Y; Shi, M; Song, W M; Song, X Y; Sosio, S; Spataro, S; Sun, G X; Sun, J F; Sun, S S; Sun, X H; Sun, Y J; Sun, Y Z; Sun, Z J; Sun, Z T; Tang, C J; Tang, X; Tapan, I; Thorndike, E H; Tiemens, M; Uman, I; Varner, G S; Wang, B; Wang, B L; Wang, D; Wang, D Y; Wang, K; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, S G; Wang, W; Wang, W P; Wang, X F; Wang, Y; Wang, Y D; Wang, Y F; Wang, Y Q; Wang, Z; Wang, Z G; Wang, Z H; Wang, Z Y; Wang, Z Y; Weber, T; Wei, D H; Wei, J B; Weidenkaff, P; Wen, S P; Wiedner, U; Wolke, M; Wu, L H; Wu, L J; Wu, Z; Xia, L; Xia, L G; Xia, Y; Xiao, D; Xiao, H; Xiao, Z J; Xie, Y G; Xiu, Q L; Xu, G F; Xu, J J; Xu, L; Xu, Q J; Xu, Q N; Xu, X P; Yan, L; Yan, W B; Yan, W C; Yan, Y H; Yang, H J; Yang, H X; Yang, L; Yang, Y X; Ye, M; Ye, M H; Yin, J H; Yu, B X; Yu, C X; Yu, J S; Yuan, C Z; Yuan, W L; Yuan, Y; Yuncu, A; Zafar, A A; Zallo, A; Zeng, Y; Zeng, Z; Zhang, B X; Zhang, B Y; Zhang, C; Zhang, C C; Zhang, D H; Zhang, H H; Zhang, H Y; Zhang, J; Zhang, J J; Zhang, J L; Zhang, J Q; Zhang, J W; Zhang, J Y; Zhang, J Z; Zhang, K; Zhang, L; Zhang, S Q; Zhang, X Y; Zhang, Y; Zhang, Y H; Zhang, Y N; Zhang, Y T; Zhang, Yu; Zhang, Z H; Zhang, Z P; Zhang, Z Y; Zhao, G; Zhao, J W; Zhao, J Y; Zhao, J Z; Zhao, Lei; Zhao, Ling; Zhao, M G; Zhao, Q; Zhao, Q W; Zhao, S J; Zhao, T C; Zhao, Y B; Zhao, Z G; Zhemchugov, A; Zheng, B; Zheng, J P; Zheng, W J; Zheng, Y H; Zhong, B; Zhou, L; Zhou, X; Zhou, X K; Zhou, X R; Zhou, X Y; Zhu, K; Zhu, K J; Zhu, S; Zhu, S H; Zhu, X L; Zhu, Y C; Zhu, Y S; Zhu, Z A; Zhuang, J; Zotti, L; Zou, B S; Zou, J H
2016-07-22
Using 1.09×10^{9} J/ψ events collected by the BESIII experiment in 2012, we study the J/ψ→γη^{'}π^{+}π^{-} process and observe a significant abrupt change in the slope of the η^{'}π^{+}π^{-} invariant mass distribution at the proton-antiproton (pp[over ¯]) mass threshold. We use two models to characterize the η^{'}π^{+}π^{-} line shape around 1.85 GeV/c^{2}: one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV/c^{2} with strong couplings to the pp[over ¯] final states or a narrow state just below the pp[over ¯] mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a pp[over ¯] moleculelike state or bound state with greater than 7σ significance.
Ablikim, M; Achasov, M N; Ahmed, S; Ai, X C; Albayrak, O; Albrecht, M; Ambrose, D J; Amoroso, A; An, F F; An, Q; Bai, J Z; Baldini Ferroli, R; Ban, Y; Bennett, D W; Bennett, J V; Berger, N; Bertani, M; Bettoni, D; Bian, J M; Bianchi, F; Boger, E; Boyko, I; Briere, R A; Cai, H; Cai, X; Cakir, O; Calcaterra, A; Cao, G F; Cetin, S A; Chang, J F; Chelkov, G; Chen, G; Chen, H S; Chen, H Y; Chen, J C; Chen, M L; Chen, S; Chen, S J; Chen, X; Chen, X R; Chen, Y B; Cheng, H P; Chu, X K; Cibinetto, G; Dai, H L; Dai, J P; Dbeyssi, A; Dedovich, D; Deng, Z Y; Denig, A; Denysenko, I; Destefanis, M; De Mori, F; Ding, Y; Dong, C; Dong, J; Dong, L Y; Dong, M Y; Dou, Z L; Du, S X; Duan, P F; Fan, J Z; Fang, J; Fang, S S; Fang, X; Fang, Y; Farinelli, R; Fava, L; Fedorov, O; Feldbauer, F; Felici, G; Feng, C Q; Fioravanti, E; Fritsch, M; Fu, C D; Gao, Q; Gao, X L; Gao, X Y; Gao, Y; Gao, Z; Garzia, I; Goetzen, K; Gong, L; Gong, W X; Gradl, W; Greco, M; Gu, M H; Gu, Y T; Guan, Y H; Guo, A Q; Guo, L B; Guo, R P; Guo, Y; Guo, Y P; Haddadi, Z; Hafner, A; Han, S; Hao, X Q; Harris, F A; He, K L; Heinsius, F H; Held, T; Heng, Y K; Holtmann, T; Hou, Z L; Hu, C; Hu, H M; Hu, J F; Hu, T; Hu, Y; Huang, G S; Huang, Y P; Huang, J S; Huang, X T; Huang, X Z; Huang, Y; Huang, Z L; Hussain, T; Ji, Q; Ji, Q P; Ji, X B; Ji, X L; Jiang, L W; Jiang, X S; Jiang, X Y; Jiao, J B; Jiao, Z; Jin, D P; Jin, S; Johansson, T; Julin, A; Kalantar-Nayestanaki, N; Kang, X L; Kang, X S; Kavatsyuk, M; Ke, B C; Kiese, P; Kliemt, R; Kloss, B; Kolcu, O B; Kopf, B; Kornicer, M; Kupsc, A; Kühn, W; Lange, J S; Lara, M; Larin, P; Leithoff, H; Leng, C; Li, C; Li, Cheng; Li, D M; Li, F; Li, F Y; Li, G; Li, H B; Li, H J; Li, J C; Li, Jin; Li, K; Li, K; Li, Lei; Li, P R; Li, Q Y; Li, T; Li, W D; Li, W G; Li, X L; Li, X N; Li, X Q; Li, Y B; Li, Z B; Liang, H; Liang, Y F; Liang, Y T; Liao, G R; Lin, D X; Liu, B; Liu, B J; Liu, C X; Liu, D; Liu, F H; Liu, Fang; Liu, Feng; Liu, H B; Liu, H H; Liu, H H; Liu, H M; Liu, J; Liu, J B; Liu, J P; Liu, J Y; Liu, K; Liu, K Y; Liu, L D; Liu, P L; Liu, Q; Liu, S B; Liu, X; Liu, Y B; Liu, Y Y; Liu, Z A; Liu, Zhiqing; Loehner, H; Lou, X C; Lu, H J; Lu, J G; Lu, Y; Lu, Y P; Luo, C L; Luo, M X; Luo, T; Luo, X L; Lyu, X R; Ma, F C; Ma, H L; Ma, L L; Ma, M M; Ma, Q M; Ma, T; Ma, X N; Ma, X Y; Ma, Y M; Maas, F E; Maggiora, M; Malik, Q A; Mao, Y J; Mao, Z P; Marcello, S; Messchendorp, J G; Mezzadri, G; Min, J; Min, T J; Mitchell, R E; Mo, X H; Mo, Y J; Morales Morales, C; Muchnoi, N Yu; Muramatsu, H; Musiol, P; Nefedov, Y; Nerling, F; Nikolaev, I B; Ning, Z; Nisar, S; Niu, S L; Niu, X Y; Olsen, S L; Ouyang, Q; Pacetti, S; Pan, Y; Patteri, P; Pelizaeus, M; Peng, H P; Peters, K; Pettersson, J; Ping, J L; Ping, R G; Poling, R; Prasad, V; Qi, H R; Qi, M; Qian, S; Qiao, C F; Qin, L Q; Qin, N; Qin, X S; Qin, Z H; Qiu, J F; Rashid, K H; Redmer, C F; Ripka, M; Rong, G; Rosner, Ch; Ruan, X D; Sarantsev, A; Savrié, M; Schnier, C; Schoenning, K; Schumann, S; Shan, W; Shao, M; Shen, C P; Shen, P X; Shen, X Y; Sheng, H Y; Shi, M; Song, W M; Song, X Y; Sosio, S; Spataro, S; Sun, G X; Sun, J F; Sun, S S; Sun, X H; Sun, Y J; Sun, Y Z; Sun, Z J; Sun, Z T; Tang, C J; Tang, X; Tapan, I; Thorndike, E H; Tiemens, M; Uman, I; Varner, G S; Wang, B; Wang, B L; Wang, D; Wang, D Y; Wang, K; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, S G; Wang, W; Wang, W P; Wang, X F; Wang, Y; Wang, Y D; Wang, Y F; Wang, Y Q; Wang, Z; Wang, Z G; Wang, Z H; Wang, Z Y; Wang, Z Y; Weber, T; Wei, D H; Wei, J B; Weidenkaff, P; Wen, S P; Wiedner, U; Wolke, M; Wu, L H; Wu, L J; Wu, Z; Xia, L; Xia, L G; Xia, Y; Xiao, D; Xiao, H; Xiao, Z J; Xie, Y G; Xiu, Q L; Xu, G F; Xu, J J; Xu, L; Xu, Q J; Xu, Q N; Xu, X P; Yan, L; Yan, W B; Yan, W C; Yan, Y H; Yang, H J; Yang, H X; Yang, L; Yang, Y X; Ye, M; Ye, M H; Yin, J H; Yu, B X; Yu, C X; Yu, J S; Yuan, C Z; Yuan, W L; Yuan, Y; Yuncu, A; Zafar, A A; Zallo, A; Zeng, Y; Zeng, Z; Zhang, B X; Zhang, B Y; Zhang, C; Zhang, C C; Zhang, D H; Zhang, H H; Zhang, H Y; Zhang, J; Zhang, J J; Zhang, J L; Zhang, J Q; Zhang, J W; Zhang, J Y; Zhang, J Z; Zhang, K; Zhang, L; Zhang, S Q; Zhang, X Y; Zhang, Y; Zhang, Y H; Zhang, Y N; Zhang, Y T; Zhang, Yu; Zhang, Z H; Zhang, Z P; Zhang, Z Y; Zhao, G; Zhao, J W; Zhao, J Y; Zhao, J Z; Zhao, Lei; Zhao, Ling; Zhao, M G; Zhao, Q; Zhao, Q W; Zhao, S J; Zhao, T C; Zhao, Y B; Zhao, Z G; Zhemchugov, A; Zheng, B; Zheng, J P; Zheng, W J; Zheng, Y H; Zhong, B; Zhou, L; Zhou, X; Zhou, X K; Zhou, X R; Zhou, X Y; Zhu, K; Zhu, K J; Zhu, S; Zhu, S H; Zhu, X L; Zhu, Y C; Zhu, Y S; Zhu, Z A; Zhuang, J; Zotti, L; Zou, B S; Zou, J H
2016-07-22
Using 1.09×10^{9} J/ψ events collected by the BESIII experiment in 2012, we study the J/ψ→γη^{'}π^{+}π^{-} process and observe a significant abrupt change in the slope of the η^{'}π^{+}π^{-} invariant mass distribution at the proton-antiproton (pp[over ¯]) mass threshold. We use two models to characterize the η^{'}π^{+}π^{-} line shape around 1.85 GeV/c^{2}: one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV/c^{2} with strong couplings to the pp[over ¯] final states or a narrow state just below the pp[over ¯] mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a pp[over ¯] moleculelike state or bound state with greater than 7σ significance. PMID:27494467
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Baldini Ferroli, R.; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Berger, N.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Cibinetto, G.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Dou, Z. L.; Du, S. X.; Duan, P. F.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Farinelli, R.; Fava, L.; Fedorov, O.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. L.; Gao, X. Y.; Gao, Y.; Gao, Z.; Garzia, I.; Goetzen, K.; Gong, L.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Hao, X. Q.; Harris, F. A.; He, K. L.; Heinsius, F. H.; Held, T.; Heng, Y. K.; Holtmann, T.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. S.; Huang, Y. P.; Huang, J. S.; Huang, X. T.; Huang, X. Z.; Huang, Y.; Huang, Z. L.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. W.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kiese, P.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kupsc, A.; Kühn, W.; Lange, J. S.; Lara, M.; Larin, P.; Leithoff, H.; Leng, C.; Li, C.; Li, Cheng; Li, D. M.; Li, F.; Li, F. Y.; Li, G.; Li, H. B.; Li, H. J.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, Q. Y.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, Y. B.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B.; Liu, B. J.; Liu, C. X.; Liu, D.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. B.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Y. Y.; Liu, Z. A.; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, T.; Ma, X. N.; Ma, X. Y.; Ma, Y. M.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Mezzadri, G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales Morales, C.; Muchnoi, N. Yu.; Muramatsu, H.; Musiol, P.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, Y.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Poling, R.; Prasad, V.; Qi, H. R.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Rosner, Ch.; Ruan, X. D.; Sarantsev, A.; Savrié, M.; Schnier, C.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Shi, M.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. H.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, B. L.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, S. G.; Wang, W.; Wang, W. P.; Wang, X. F.; Wang, Y.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, L. J.; Wu, Z.; Xia, L.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, H.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, J. J.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zeng, Z.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, S. Q.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. N.; Zhang, Y. T.; Zhang, Yu; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zotti, L.; Zou, B. S.; Zou, J. H.; Besiii Collaboration
2016-07-01
Using 1.09 ×109 J /ψ events collected by the BESIII experiment in 2012, we study the J /ψ →γ η'π+π- process and observe a significant abrupt change in the slope of the η'π+π- invariant mass distribution at the proton-antiproton (p p ¯) mass threshold. We use two models to characterize the η'π+π- line shape around 1.85 GeV /c2: one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV /c2 with strong couplings to the p p ¯ final states or a narrow state just below the p p ¯ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a p p ¯ moleculelike state or bound state with greater than 7 σ significance.
ITER Scenario Performance Simulations Assessing Control and Vertical Stability
Casper, T; Ferron, J; Humphreys, D; Jackson, G; Leuer, J; LoDestro, L; Luce, T; Meyer, W; Pearlstein, L; Welander, A
2008-05-20
In simulating reference scenarios proposed for ITER operation, we also explore performance of the poloidal field (PF) and central solenoid (CS) coil systems using a controller to maintain plasma shape and vertical stability during the discharge evolution. We employ a combination of techniques to evaluate system constraints and stability using time-dependent transport simulations of ITER discharges. We have begun the process of benchmarking these simulations with experiments on the DIII-D tokamak. Simulations include startup on the outside limiter, X-point formation and current ramp up to full power, plasma burn conditions at 15MA and 17MA, and ramp down at the end of the pulse. We also simulate perturbative events such as H-to-L back transitions. Our results indicate the viability of proposed ITER operating modes.
Experimental studies of ITER demonstration discharges
NASA Astrophysics Data System (ADS)
Sips, A. C. C.; Casper, T. A.; Doyle, E. J.; Giruzzi, G.; Gribov, Y.; Hobirk, J.; Hogeweij, G. M. D.; Horton, L. D.; Hubbard, A. E.; Hutchinson, I.; Ide, S.; Isayama, A.; Imbeaux, F.; Jackson, G. L.; Kamada, Y.; Kessel, C.; Kochl, F.; Lomas, P.; Litaudon, X.; Luce, T. C.; Marmar, E.; Mattei, M.; Nunes, I.; Oyama, N.; Parail, V.; Portone, A.; Saibene, G.; Sartori, R.; Stober, J. K.; Suzuki, T.; Wolfe, S. M.; C-Mod Team; ASDEX Upgrade Team; DIII-D Team; JET EFDA Contributors
2009-08-01
Key parts of the ITER scenarios are determined by the capability of the proposed poloidal field (PF) coil set. They include the plasma breakdown at low loop voltage, the current rise phase, the performance during the flat top (FT) phase and a ramp down of the plasma. The ITER discharge evolution has been verified in dedicated experiments. New data are obtained from C-Mod, ASDEX Upgrade, DIII-D, JT-60U and JET. Results show that breakdown for Eaxis < 0.23-0.33 V m-1 is possible unassisted (ohmic) for large devices like JET and attainable in devices with a capability of using ECRH assist. For the current ramp up, good control of the plasma inductance is obtained using a full bore plasma shape with early X-point formation. This allows optimization of the flux usage from the PF set. Additional heating keeps li(3) < 0.85 during the ramp up to q95 = 3. A rise phase with an H-mode transition is capable of achieving li(3) < 0.7 at the start of the FT. Operation of the H-mode reference scenario at q95 ~ 3 and the hybrid scenario at q95 = 4-4.5 during the FT phase is documented, providing data for the li (3) evolution after the H-mode transition and the li (3) evolution after a back-transition to L-mode. During the ITER ramp down it is important to remain diverted and to reduce the elongation. The inductance could be kept <=1.2 during the first half of the current decay, using a slow Ip ramp down, but still consuming flux from the transformer. Alternatively, the discharges can be kept in H-mode during most of the ramp down, requiring significant amounts of additional heating.
ITER safety challenges and opportunities
Piet, S.J.
1991-01-01
Results of the Conceptual Design Activity (CDA) for the International Thermonuclear Experimental Reactor (ITER) suggest challenges and opportunities. ITER is capable of meeting anticipated regulatory dose limits,'' but proof is difficult because of large radioactive inventories needing stringent radioactivity confinement. We need much research and development (R D) and design analysis to establish that ITER meets regulatory requirements. We have a further opportunity to do more to prove more of fusion's potential safety and environmental advantages and maximize the amount of ITER technology on the path toward fusion power plants. To fulfill these tasks, we need to overcome three programmatic challenges and three technical challenges. The first programmatic challenge is to fund a comprehensive safety and environmental ITER R D plan. Second is to strengthen safety and environment work and personnel in the international team. Third is to establish an external consultant group to advise the ITER Joint Team on designing ITER to meet safety requirements for siting by any of the Parties. The first of the three key technical challenges is plasma engineering -- burn control, plasma shutdown, disruptions, tritium burn fraction, and steady state operation. The second is the divertor, including tritium inventory, activation hazards, chemical reactions, and coolant disturbances. The third technical challenge is optimization of design requirements considering safety risk, technical risk, and cost. Some design requirements are now too strict; some are too lax. Fuel cycle design requirements are presently too strict, mandating inappropriate T separation from H and D. Heat sink requirements are presently too lax; they should be strengthened to ensure that maximum loss of coolant accident temperatures drop.
The ITER Radial Neutron Camera Detection System
Marocco, D.; Belli, F.; Esposito, B.; Petrizzi, L.; Riva, M.; Bonheure, G.; Kaschuck, Y.
2008-03-12
A multichannel neutron detection system (Radial Neutron Camera, RNC) will be installed on the ITER equatorial port plug 1 for total neutron source strength, neutron emissivity/ion temperature profiles and n{sub t}/n{sub d} ratio measurements [1]. The system is composed by two fan shaped collimating structures: an ex-vessel structure, looking at the plasma core, containing tree sets of 12 collimators (each set lying on a different toroidal plane), and an in-vessel structure, containing 9 collimators, for plasma edge coverage. The RNC detecting system will work in a harsh environment (neutron fiux up to 10{sup 8}-10{sup 9} n/cm{sup 2} s, magnetic field >0.5 T or in-vessel detectors), should provide both counting and spectrometric information and should be flexible enough to cover the high neutron flux dynamic range expected during the different ITER operation phases. ENEA has been involved in several activities related to RNC design and optimization [2,3]. In the present paper the up-to-date design and the neutron emissivity reconstruction capabilities of the RNC will be described. Different options for detectors suitable for spectrometry and counting (e.g. scintillators and diamonds) focusing on the implications in terms of overall RNC performance will be discussed. The increase of the RNC capabilities offered by the use of new digital data acquisition systems will be also addressed.
Iterative reconstruction of volumetric particle distribution
NASA Astrophysics Data System (ADS)
Wieneke, Bernhard
2013-02-01
For tracking the motion of illuminated particles in space and time several volumetric flow measurement techniques are available like 3D-particle tracking velocimetry (3D-PTV) recording images from typically three to four viewing directions. For higher seeding densities and the same experimental setup, tomographic PIV (Tomo-PIV) reconstructs voxel intensities using an iterative tomographic reconstruction algorithm (e.g. multiplicative algebraic reconstruction technique, MART) followed by cross-correlation of sub-volumes computing instantaneous 3D flow fields on a regular grid. A novel hybrid algorithm is proposed here that similar to MART iteratively reconstructs 3D-particle locations by comparing the recorded images with the projections calculated from the particle distribution in the volume. But like 3D-PTV, particles are represented by 3D-positions instead of voxel-based intensity blobs as in MART. Detailed knowledge of the optical transfer function and the particle image shape is mandatory, which may differ for different positions in the volume and for each camera. Using synthetic data it is shown that this method is capable of reconstructing densely seeded flows up to about 0.05 ppp with similar accuracy as Tomo-PIV. Finally the method is validated with experimental data.
ITER Construction--Plant System Integration
Tada, E.; Matsuda, S.
2009-02-19
This brief paper introduces how the ITER will be built in the international collaboration. The ITER Organization plays a central role in constructing ITER and leading it into operation. Since most of the ITER components are to be provided in-kind from the member countries, integral project management should be scoped in advance of real work. Those include design, procurement, system assembly, testing, licensing and commissioning of ITER.
ITER project and fusion technology
NASA Astrophysics Data System (ADS)
Takatsu, H.
2011-09-01
In the sessions of ITR, FTP and SEE of the 23rd IAEA Fusion Energy Conference, 159 papers were presented in total, highlighted by the remarkable progress of the ITER project: ITER baseline has been established and procurement activities have been started as planned with a target of realizing the first plasma in 2019; ITER physics basis is sound and operation scenarios and operational issues have been extensively studied in close collaboration with the worldwide physics community; the test blanket module programme has been incorporated into the ITER programme and extensive R&D works are ongoing in the member countries with a view to delivering their own modules in a timely manner according to the ITER master schedule. Good progress was also reported in the areas of a variety of complementary activities to DEMO, including Broader Approach activities and long-term technology. This paper summarizes the highlights of the papers presented in the ITR, FTP and SEE sessions with a minimum set of background information.
Construction Safety Forecast for ITER
cadwallader, lee charles
2006-11-01
The International Thermonuclear Experimental Reactor (ITER) project is poised to begin its construction activity. This paper gives an estimate of construction safety as if the experiment was being built in the United States. This estimate of construction injuries and potential fatalities serves as a useful forecast of what can be expected for construction of such a major facility in any country. These data should be considered by the ITER International Team as it plans for safety during the construction phase. Based on average U.S. construction rates, ITER may expect a lost workday case rate of < 4.0 and a fatality count of 0.5 to 0.9 persons per year.
Error Field Correction in ITER
Park, Jong-kyu; Boozer, Allen H.; Menard, Jonathan E.; Schaffer, Michael J.
2008-05-22
A new method for correcting magnetic field errors in the ITER tokamak is developed using the Ideal Perturbed Equilibrium Code (IPEC). The dominant external magnetic field for driving islands is shown to be localized to the outboard midplane for three ITER equilibria that represent the projected range of operational scenarios. The coupling matrices between the poloidal harmonics of the external magnetic perturbations and the resonant fields on the rational surfaces that drive islands are combined for different equilibria and used to determine an ordered list of the dominant errors in the external magnetic field. It is found that efficient and robust error field correction is possible with a fixed setting of the correction currents relative to the currents in the main coils across the range of ITER operating scenarios that was considered.
Attaya, H.; Gohar, Y.; Smith, D.
1990-09-01
Activation analysis has been made for the US ITER design. The radioactivity and the decay heat have been calculated, during operation and after shutdown for the two ITER phases, the Physics Phase and the Technology Phase. The Physics Phase operates about 24 full power days (FPDs) at fusion power level of 1100 MW and the Technology Phase has 860 MW fusion power and operates for about 1360 FPDs. The point-wise gamma sources have been calculated everywhere in the reactor at several times after shutdown of the two phases and are then used to calculate the biological dose everywhere in the reactor. Activation calculations have been made also for ITER divertor. The results are presented for different continuous operation times and for only one pulse. The effect of the pulsed operation on the radioactivity is analyzed. 6 refs., 12 figs., 1 tab.
Wurden, G A
2009-01-01
For future machines, the plasma stored energy is going up by factors of 20-40x, and plasma currents by 2-3x, while the surface to volume ratio is at the same time decreasing. Therefore the disruption forces, even for constant B, (which scale like IxB), and associated possible localized heating on machine components, are more severe. Notably, Tore Supra has demonstrated removal of more than 1 GJ of input energy, over nearly a 400 second period. However, the instantaneous stored energy in the Tore Supra system (which is most directly related to the potential for disruption damage) is quite small compared to other large tokamaks. The goal of ITER is routinely described as studying DT burning plasmas with a Q {approx} 10. In reality, ITER has a much more important first order mission. In fact, if it fails at this mission, the consequences are that ITER will never get to the eventual stated purpose of studying a burning plasma. The real mission of ITER is to study (and demonstrate successfully) plasma control with {approx}10-17 MA toroidal currents and {approx}100-400 MJ plasma stored energy levels in long-pulse scenarios. Before DT operation is ever given a go-ahead in ITER, the reality is that ITER must demonstrate routine and reliable control of high energy hydrogen (and deuterium) plasmas. The difficulty is that ITER must simultaneously deal with several technical problems: (1) heat removal at the plasma/wall interface, (2) protection of the wall components from off-normal events, and (3) generation of dust/redeposition of first wall materials. All previous tokamaks have encountered hundred's of major disruptions in the course of their operation. The consequences of a few MA of runaway electrons (at 20-50 MeV) being generated in ITER, and then being lost to the walls are simply catastrophic. They will not be deposited globally, but will drift out (up, down, whatever, depending on control system), and impact internal structures, unless 'ameliorated'. Basically, this
Selective Iterative Waterfilling for Digital Subscriber Lines
NASA Astrophysics Data System (ADS)
Xu, Yang; Le-Ngoc, Tho; Panigrahi, Saswat
2007-12-01
This paper presents a high-performance, low-complexity, quasi-distributed dynamic spectrum management (DSM) algorithm suitable for DSL systems. We analytically demonstrate that the rate degradation of the distributed iterative waterfilling (IW) algorithm in near-far scenarios is caused by the insufficient utilization of all available frequency and power resources due to its nature of noncooperative game theoretic formulation. Inspired by this observation, we propose the selective IW (SIW) algorithm that can considerably alleviate the performance degradation of IW by applying IW selectively to different groups of users over different frequency bands so that all the available resources can be fully utilized. For [InlineEquation not available: see fulltext.] users, the proposed SIW algorithm needs at most [InlineEquation not available: see fulltext.] times the complexity of the IW algorithm, and is much simpler than the centralized optimal spectrum balancing (OSB), while it can offer a rate performance much better than that of the IW and close to the maximum possible rate region computed by the OSB in realistic near-far DSL scenarios. Furthermore, its predominantly distributed structure makes it suitable for DSL implementation.
Iterated binomial sums and their associated iterated integrals
NASA Astrophysics Data System (ADS)
Ablinger, J.; Blümlein, J.; Raab, C. G.; Schneider, C.
2014-11-01
We consider finite iterated generalized harmonic sums weighted by the binomial binom{2k}{k} in numerators and denominators. A large class of these functions emerges in the calculation of massive Feynman diagrams with local operator insertions starting at 3-loop order in the coupling constant and extends the classes of the nested harmonic, generalized harmonic, and cyclotomic sums. The binomially weighted sums are associated by the Mellin transform to iterated integrals over square-root valued alphabets. The values of the sums for N → ∞ and the iterated integrals at x = 1 lead to new constants, extending the set of special numbers given by the multiple zeta values, the cyclotomic zeta values and special constants which emerge in the limit N → ∞ of generalized harmonic sums. We develop algorithms to obtain the Mellin representations of these sums in a systematic way. They are of importance for the derivation of the asymptotic expansion of these sums and their analytic continuation to N in {C}. The associated convolution relations are derived for real parameters and can therefore be used in a wider context, as, e.g., for multi-scale processes. We also derive algorithms to transform iterated integrals over root-valued alphabets into binomial sums. Using generating functions we study a few aspects of infinite (inverse) binomial sums.
Delayed Over-Relaxation for iterative methods
NASA Astrophysics Data System (ADS)
Antuono, M.; Colicchio, G.
2016-09-01
We propose a variant of the relaxation step used in the most widespread iterative methods (e.g. Jacobi Over-Relaxation, Successive Over-Relaxation) which combines the iteration at the predicted step, namely (n + 1), with the iteration at step (n - 1). We provide a theoretical analysis of the proposed algorithm by applying such a delayed relaxation step to a generic (convergent) iterative scheme. We prove that, under proper assumptions, this significantly improves the convergence rate of the initial iterative method. As a relevant example, we apply the proposed algorithm to the solution of the Poisson equation, highlighting the advantages in comparison with classical iterative models.
ODE System Solver W. Krylov Iteration & Rootfinding
1991-09-09
LSODKR is a new initial value ODE solver for stiff and nonstiff systems. It is a variant of the LSODPK and LSODE solvers, intended mainly for large stiff systems. The main differences between LSODKR and LSODE are the following: (a) for stiff systems, LSODKR uses a corrector iteration composed of Newton iteration and one of four preconditioned Krylov subspace iteration methods. The user must supply routines for the preconditioning operations, (b) Within the corrector iteration,more » LSODKR does automatic switching between functional (fixpoint) iteration and modified Newton iteration, (c) LSODKR includes the ability to find roots of given functions of the solution during the integration.« less
ERIC Educational Resources Information Center
Greenslade, Thomas B., Jr.
1984-01-01
Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)
Continued Fractions and Iterative Processes.
ERIC Educational Resources Information Center
Bevis, Jean H.; Boal, Jan L.
1982-01-01
Continued fractions and associated sequences are viewed to constitute a rich area of study for mathematics students, by supporting instruction on algebraic and computational skills, mathematical induction, convergence of sequences, and interpretation of function graphs. An iterative method of approximating square roots opens suggestions for…
Energetic ions in ITER plasmas
NASA Astrophysics Data System (ADS)
Pinches, S. D.; Chapman, I. T.; Lauber, Ph. W.; Oliver, H. J. C.; Sharapov, S. E.; Shinohara, K.; Tani, K.
2015-02-01
This paper discusses the behaviour and consequences of the expected populations of energetic ions in ITER plasmas. It begins with a careful analytic and numerical consideration of the stability of Alfvén Eigenmodes in the ITER 15 MA baseline scenario. The stability threshold is determined by balancing the energetic ion drive against the dominant damping mechanisms and it is found that only in the outer half of the plasma ( r / a > 0.5 ) can the fast ions overcome the thermal ion Landau damping. This is in spite of the reduced numbers of alpha-particles and beam ions in this region but means that any Alfvén Eigenmode-induced redistribution is not expected to influence the fusion burn process. The influence of energetic ions upon the main global MHD phenomena expected in ITER's primary operating scenarios, including sawteeth, neoclassical tearing modes and Resistive Wall Modes, is also reviewed. Fast ion losses due to the non-axisymmetric fields arising from the finite number of toroidal field coils, the inclusion of ferromagnetic inserts, the presence of test blanket modules containing ferromagnetic material, and the fields created by the Edge Localised Mode (ELM) control coils in ITER are discussed. The greatest losses and associated heat loads onto the plasma facing components arise due to the use of the ELM control coils and come from neutral beam ions that are ionised in the plasma edge.
Networking Theories by Iterative Unpacking
ERIC Educational Resources Information Center
Koichu, Boris
2014-01-01
An iterative unpacking strategy consists of sequencing empirically-based theoretical developments so that at each step of theorizing one theory serves as an overarching conceptual framework, in which another theory, either existing or emerging, is embedded in order to elaborate on the chosen element(s) of the overarching theory. The strategy is…
Active beam spectroscopy for ITER
NASA Astrophysics Data System (ADS)
von Hellermann, M. G.; Barnsley, R.; Biel, W.; Delabie, E.; Hawkes, N.; Jaspers, R.; Johnson, D.; Klinkhamer, F.; Lischtschenko, O.; Marchuk, O.; Schunke, B.; Singh, M. J.; Snijders, B.; Summers, H. P.; Thomas, D.; Tugarinov, S.; Vasu, P.
2010-11-01
Since the first feasibility studies of active beam spectroscopy on ITER in 1995 the proposed diagnostic has developed into a well advanced and mature system. Substantial progress has been achieved on the physics side including comprehensive performance studies based on an advanced predictive code, which simulates active and passive features of the expected spectral ranges. The simulation has enabled detailed specifications for an optimized instrumentation and has helped to specify suitable diagnostic neutral beam parameters. Four ITER partners share presently the task of developing a suite of ITER active beam diagnostics, which make use of the two 0.5 MeV/amu 18 MW heating neutral beams and a dedicated 0.1 MeV/amu, 3.6 MW diagnostic neutral beam. The IN ITER team is responsible for the DNB development and also for beam physics related aspects of the diagnostic. The RF will be responsible for edge CXRS system covering the outer region of the plasma (1> r/ a>0.4) using an equatorial observation port, and the EU will develop the core CXRS system for the very core (0< r/ a<0.7) using a top observation port. Thus optimum radial resolution is ensured for each system with better than a/30 resolution. Finally, the US will develop a dedicated MSE system making use of the HNBs and two equatorial ports. With appropriate modification, these systems could also potentially provide information on alpha particle slowing-down features. . On the engineering side, comprehensive preparations were made involving the development of an observation periscope, a neutron labyrinth optical system and design studies for remote maintenance including the exchange of the first mirror assembly, a critical issue for the operation of the CXRS diagnostic in the harsh ITER environment. Additionally, an essential change of the orientation of the DNB injection angle and specification of suitable blanket aperture has been made to avoid trapped particle damage to the first wall.
Reconstruction of missing data using iterative harmonic expansion
NASA Astrophysics Data System (ADS)
Nishizawa, Atsushi J.; Inoue, Kaiki Taro
2016-10-01
In the cosmic microwave background or galaxy density maps, missing fluctuations in masked regions can be reconstructed from fluctuations in the surrounding unmasked regions if the original fluctuations are sufficiently smooth. One reconstruction method involves applying a harmonic expansion iteratively to fluctuations in the unmasked region. In this paper, we discuss how well this reconstruction method can recover the original fluctuations depending on the prior of fluctuations and property of the masked region. The reconstruction method is formulated with an asymptotic expansion in terms of the size of mask for a fixed iteration number. The reconstruction accuracy depends on the mask size, the spectrum of the underlying density fluctuations, the scales of the fluctuations to be reconstructed and the number of iterations. For Gaussian fluctuations with the Harrison-Zel'dovich spectrum, the reconstruction method provides more accurate restoration than naive methods based on brute-force matrix inversion or the singular value decomposition. We also demonstrate that an isotropic non-Gaussian prior does not change the results but an anisotropic non-Gaussian prior can yield a higher reconstruction accuracy compared to the Gaussian prior case.
Enhanced compressive wideband frequency spectrum sensing for dynamic spectrum access
NASA Astrophysics Data System (ADS)
Liu, Yipeng; Wan, Qun
2012-12-01
Wideband spectrum sensing detects the unused spectrum holes for dynamic spectrum access (DSA). Too high sampling rate is the main challenge. Compressive sensing (CS) can reconstruct sparse signal with much fewer randomized samples than Nyquist sampling with high probability. Since survey shows that the monitored signal is sparse in frequency domain, CS can deal with the sampling burden. Random samples can be obtained by the analog-to-information converter. Signal recovery can be formulated as the combination of an L0 norm minimization and a linear measurement fitting constraint. In DSA, the static spectrum allocation of primary radios means the bounds between different types of primary radios are known in advance. To incorporate this a priori information, we divide the whole spectrum into sections according to the spectrum allocation policy. In the new optimization model, the minimization of the L2 norm of each section is used to encourage the cluster distribution locally, while the L0 norm of the L2 norms is minimized to give sparse distribution globally. Because the L2/L0 optimization is not convex, an iteratively re-weighted L2/L1 optimization is proposed to approximate it. Simulations demonstrate the proposed method outperforms others in accuracy, denoising ability, etc.
Boundary plasma modelling for ITER
Braams, B.J.
1993-01-01
Computer programs were developed to model the effect of nonaxisymmetric magnetic perturbations upon divertor heat load, and have explored what kind of externally applied perturbations are the most effective for heat load reduction without destroying core plasma confinement. We find that a carefully tuned set of coils located about 0.3 m outside the separatrix can be used to spread the heat load over about 0.1 m perpendicular to flux surfaces at the ITER divertor plate, even at a very low level of anomalous cross-field heat transport. As such a spreading would significantly extend the permissible regime of operation for ITER, we recommend that this study be pursued at the level of detail required for engineering design. In other work under this grant we are in the process of modifying the B2 code to handle correctly a non-orthogonal geometry.
Bioinspired Iterative Synthesis of Polyketides
NASA Astrophysics Data System (ADS)
Hong, Ran; Zheng, Kuan; Xie, Changmin
2015-05-01
Diverse array of biopolymers and second metabolites (particularly polyketide natural products) has been manufactured in nature through an enzymatic iterative assembly of simple building blocks. Inspired by this strategy, molecules with inherent modularity can be efficiently synthesized by repeated succession of similar reaction sequences. This privileged strategy has been widely adopted in synthetic supramolecular chemistry. Its value also has been reorganized in natural product synthesis. A brief overview of this approach is given with a particular emphasis on the total synthesis of polyol-embedded polyketides, a class of vastly diverse structures and biologically significant natural products. This viewpoint also illustrates the limits of known individual modules in terms of diastereoselectivity and enantioselectivity. More efficient and practical iterative strategies are anticipated to emerge in the future development.
Bioinspired iterative synthesis of polyketides
Zheng, Kuan; Xie, Changmin; Hong, Ran
2015-01-01
Diverse array of biopolymers and second metabolites (particularly polyketide natural products) has been manufactured in nature through an enzymatic iterative assembly of simple building blocks. Inspired by this strategy, molecules with inherent modularity can be efficiently synthesized by repeated succession of similar reaction sequences. This privileged strategy has been widely adopted in synthetic supramolecular chemistry. Its value also has been reorganized in natural product synthesis. A brief overview of this approach is given with a particular emphasis on the total synthesis of polyol-embedded polyketides, a class of vastly diverse structures and biologically significant natural products. This viewpoint also illustrates the limits of known individual modules in terms of diastereoselectivity and enantioselectivity. More efficient and practical iterative strategies are anticipated to emerge in the future development. PMID:26052510
Progress on US ITER Diagnostics
NASA Astrophysics Data System (ADS)
Johnson, David; Feder, Russ
2010-11-01
There have been significant advances in the design concepts for the 8 ITER diagnostic systems being provided by the US. Concepts for integration of the diagnostics into the port plugs have also evolved. A prerequisite for the signoff of the procurement arrangements for these each diagnostic is a Conceptual Design Review organized by the ITER Organization. US experts under contract with the USIPO have been assisting the IO to prepare for these Reviews. In addition, a design team at PPPL has been working with these experts and designers from other ITER parties to package diagnostic front-ends into the 5 US plugs. Modular diagnostic shield modules are now being considered in order to simplify the interfaces between the diagnostics within each plug. Diagnostic first wall elements are envisioned to be integral with these shield modules. This simplifies the remote handling of the diagnostics and provides flexibility for future removal of one diagnostic minimally affecting others. Front-end configurations will be presented, along with lists of issues needing resolution prior to the start of preliminary design.
Irradiation tests of ITER candidate Hall sensors using two types of neutron spectra
Duran, I.; Viererbl, L.; Lahodova, Z.; Sentkerestiova, J.; Bem, P.
2010-10-15
We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 10{sup 16} cm{sup -2} was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum.
Irradiation tests of ITER candidate Hall sensors using two types of neutron spectra.
Ďuran, I; Bolshakova, I; Viererbl, L; Sentkerestiová, J; Holyaka, R; Lahodová, Z; Bém, P
2010-10-01
We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 10(16) cm(-2) was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum.
Barantsev, K. A. Popov, E. N.; Litvinov, A. N.
2015-11-15
The theory of coherent population trapping resonance is developed for the finite linewidth of the laser radiation spectrum in an optically dense medium of Λ atoms in a cell with a buffer gas. Equations are derived for the atomic density matrix and laser emission spectrum transfer in a cell with working and buffer gases at a finite temperature. The dependence of the quality factor of coherent population trapping resonance on the linewidth of the laser radiation spectrum is studied by measuring transmitted radiation and fluorescence signals.
Iterative feedback algorithm for phase retrieval based on transport of intensity equation
NASA Astrophysics Data System (ADS)
Liu, Kaifeng; Cheng, Hong; Zhang, Cheng; Shen, Chuan; Zhang, Fen; Wei, Sui
2015-12-01
In this paper, a novel phase retrieval algorithm is presented which combines the advantages of the Transport of Intensity Equation (TIE) method and the iteration method. TIE method is fast, but its precision is not high. Though the convergence rate of iteration method is slow, its result is more accurate. This algorithm consists of Iterative Angular Spectrum (IAS) method to utilize the physical constraints between the object and the spectral domain, and the relationship between the intensity and phase among the wave propagation. Firstly, the phase at the object plane is calculated from two intensity images by TIE. Then this result is treated as the initial phase of the IAS. Finally, the phase information at the object plane is acquired according the reversibility of the optical path. During the iteration process, the feedback mechanism is imposed on it that improve the convergence rate and the precision of phase retrieval and the simulation results are given.
Decentralized Control of Sound Radiation Using Iterative Loop Recovery
NASA Technical Reports Server (NTRS)
Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.
2009-01-01
A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.
Decentralized control of sound radiation using iterative loop recovery.
Schiller, Noah H; Cabell, Randolph H; Fuller, Chris R
2010-10-01
A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.
Decentralized control of sound radiation using iterative loop recovery.
Schiller, Noah H; Cabell, Randolph H; Fuller, Chris R
2010-10-01
A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units. PMID:20968346
Lendlein, Andreas; Kelch, Steffen
2002-06-17
Material scientists predict a prominent role in the future for self-repairing and intelligent materials. Throughout the last few years, this concept has found growing interest as a result of the rise of a new class of polymers. These so-called shape-memory polymers by far surpass well-known metallic shape-memory alloys in their shape-memory properties. As a consequence of the relatively easy manufacture and programming of shape-memory polymers, these materials represent a cheap and efficient alternative to well-established shape-memory alloys. In shape-memory polymers, the consequences of an intended or accidental deformation caused by an external force can be ironed out by heating the material above a defined transition temperature. This effect can be achieved because of the given flexibility of the polymer chains. When the importance of polymeric materials in our daily life is taken into consideration, we find a very broad, additional spectrum of possible applications for intelligent polymers that covers an area from minimally invasive surgery, through high-performance textiles, up to self-repairing plastic components in every kind of transportation vehicles.
NREL Spectrum of Clean Energy Innovation (Brochure)
Not Available
2011-09-01
This brochure describes the NREL Spectrum of Clean Energy Innovation, which includes analysis and decision support, fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. Through deep technical expertise and an unmatched breadth of capabilities, the National Renewable Energy Laboratory (NREL) leads an integrated approach across the spectrum of renewable energy innovation. From scientific discovery to accelerating market deployment, NREL works in partnership with private industry to drive the transformation of our nation's energy systems. NREL integrates the entire spectrum of innovation, including fundamental science, market relevant research, systems integration, testing and validation, commercialization, and deployment. Our world-class analysis and decision support informs every point on the spectrum. The innovation process at NREL is inter-dependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies may come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.
Rater variables associated with ITER ratings.
Paget, Michael; Wu, Caren; McIlwrick, Joann; Woloschuk, Wayne; Wright, Bruce; McLaughlin, Kevin
2013-10-01
Advocates of holistic assessment consider the ITER a more authentic way to assess performance. But this assessment format is subjective and, therefore, susceptible to rater bias. Here our objective was to study the association between rater variables and ITER ratings. In this observational study our participants were clerks at the University of Calgary and preceptors who completed online ITERs between February 2008 and July 2009. Our outcome variable was global rating on the ITER (rated 1-5), and we used a generalized estimating equation model to identify variables associated with this rating. Students were rated "above expected level" or "outstanding" on 66.4 % of 1050 online ITERs completed during the study period. Two rater variables attenuated ITER ratings: the log transformed time taken to complete the ITER [β = -0.06, 95 % confidence interval (-0.10, -0.02), p = 0.002], and the number of ITERs that a preceptor completed over the time period of the study [β = -0.008 (-0.02, -0.001), p = 0.02]. In this study we found evidence of leniency bias that resulted in two thirds of students being rated above expected level of performance. This leniency bias appeared to be attenuated by delay in ITER completion, and was also blunted in preceptors who rated more students. As all biases threaten the internal validity of the assessment process, further research is needed to confirm these and other sources of rater bias in ITER ratings, and to explore ways of limiting their impact.
Rutherford, P.H.
1997-04-01
Experimental research on the International Thermonuclear Experimental Reactor (ITER) will go far beyond what is possible on present-day tokamaks to address new and challenging issues in the physics of reactor-like plasmas. First and foremost, experiments in ITER will explore the physics issues of burning plasmas--plasmas that are dominantly self-heated by alpha-particles created by the fusion reactions themselves. Such issues will include (i) new plasma-physical effects introduced by the presence within the plasma of an intense population of energetic alpha particles; (ii) the physics of magnetic confinement for a burning plasma, which will involve a complex interplay of transport, stability and an internal self-generated heat source; and (iii) the physics of very-long-pulse/steady-state burning plasmas, in which much of the plasma current is also self-generated and which will require effective control of plasma purity and plasma-wall interactions. Achieving and sustaining burning plasma regimes in a tokamak necessarily requires plasmas that are larger than those in present experiments and have higher energy content and power flow, as well as much longer pulse length. Accordingly, the experimental program on ITER will embrace the study of issues of plasma physics and plasma-materials interactions that are specific to a reactor-scale fusion experiment. Such issues will include (i) confinement physics for a tokamak in which, for the first time, the core-plasma and the edge-plasma are simultaneously in a reactor-like regime; (ii) phenomena arising during plasma transients, including so-called disruptions, in regimes of high plasma current and thermal energy; and (iii) physics of a radiative divertor designed for handling high power flow for long pulses, including novel plasma and atomic-physics effects as well as materials science of surfaces subject to intense plasma interaction. Experiments on ITER will be conducted by researchers in control rooms situated at major
Iterates of maps with symmetry
NASA Technical Reports Server (NTRS)
Chossat, Pascal; Golubitsky, Martin
1988-01-01
Fixed-point bifurcation, period doubling, and Hopf bifurcation (HB) for iterates of equivariant mappings are investigated analytically, with a focus on HB in the presence of symmetry. An algebraic formulation for the hypotheses of the theorem of Ruelle (1973) is derived, and the case of standing waves in a system of ordinary differential equations with O(2) symmetry is considered in detail. In this case, it is shown that HB can lead directly to motion on an invariant 3-torus, with an unexpected third frequency due to drift of standing waves along the torus.
Barr, W.L.; Bathke, C.G.; Brooks, J.N.; Bulmer, R.H.; Busigin, A.; DuBois, P.F.; Fenstermacher, M.E.; Fink, J.; Finn, P.A.; Galambos, J.D.; Gohar, Y.; Gorker, G.E.; Haines, J.R.; Hassanein, A.M.; Hicks, D.R.; Ho, S.K.; Kalsi, S.S.; Kalyanam, K.M.; Kerns, J.A.; Lee, J.D.; Miller, J.R.; Miller, R.L.; Myall, J.O.; Peng, Y-K.M.; Perkins, L.J.; Spampinato, P.T.; Strickler, D.J.; Thomson, S.L.; Wagner, C.E.; Willms, R.S.; Reid, R.L.
1988-04-01
A tokamak systems code capable of modeling experimental test reactors has been developed and is described in this document. The code, named TETRA (for Tokamak Engineering Test Reactor Analysis), consists of a series of modules, each describing a tokamak system or component, controlled by an optimizer/driver. This code development was a national effort in that the modules were contributed by members of the fusion community and integrated into a code by the Fusion Engineering Design Center. The code has been checked out on the Cray computers at the National Magnetic Fusion Energy Computing Center and has satisfactorily simulated the Tokamak Ignition/Burn Experimental Reactor II (TIBER) design. A feature of this code is the ability to perform optimization studies through the use of a numerical software package, which iterates prescribed variables to satisfy a set of prescribed equations or constraints. This code will be used to perform sensitivity studies for the proposed International Thermonuclear Experimental Reactor (ITER). 22 figs., 29 tabs.
ITER Port Interspace Pressure Calculations
Carbajo, Juan J; Van Hove, Walter A
2016-01-01
The ITER Vacuum Vessel (VV) is equipped with 54 access ports. Each of these ports has an opening in the bioshield that communicates with a dedicated port cell. During Tokamak operation, the bioshield opening must be closed with a concrete plug to shield the radiation coming from the plasma. This port plug separates the port cell into a Port Interspace (between VV closure lid and Port Plug) on the inner side and the Port Cell on the outer side. This paper presents calculations of pressures and temperatures in the ITER (Ref. 1) Port Interspace after a double-ended guillotine break (DEGB) of a pipe of the Tokamak Cooling Water System (TCWS) with high temperature water. It is assumed that this DEGB occurs during the worst possible conditions, which are during water baking operation, with water at a temperature of 523 K (250 C) and at a pressure of 4.4 MPa. These conditions are more severe than during normal Tokamak operation, with the water at 398 K (125 C) and 2 MPa. Two computer codes are employed in these calculations: RELAP5-3D Version 4.2.1 (Ref. 2) to calculate the blowdown releases from the pipe break, and MELCOR, Version 1.8.6 (Ref. 3) to calculate the pressures and temperatures in the Port Interspace. A sensitivity study has been performed to optimize some flow areas.
Iterated Stretching of Viscoelastic Jets
NASA Technical Reports Server (NTRS)
Chang, Hsueh-Chia; Demekhin, Evgeny A.; Kalaidin, Evgeny
1999-01-01
We examine, with asymptotic analysis and numerical simulation, the iterated stretching dynamics of FENE and Oldroyd-B jets of initial radius r(sub 0), shear viscosity nu, Weissenberg number We, retardation number S, and capillary number Ca. The usual Rayleigh instability stretches the local uniaxial extensional flow region near a minimum in jet radius into a primary filament of radius [Ca(1 - S)/ We](sup 1/2)r(sub 0) between two beads. The strain-rate within the filament remains constant while its radius (elastic stress) decreases (increases) exponentially in time with a long elastic relaxation time 3We(r(sup 2, sub 0)/nu). Instabilities convected from the bead relieve the tension at the necks during this slow elastic drainage and trigger a filament recoil. Secondary filaments then form at the necks from the resulting stretching. This iterated stretching is predicted to occur successively to generate high-generation filaments of radius r(sub n), (r(sub n)/r(sub 0)) = square root of 2[r(sub n-1)/r(sub 0)](sup 3/2) until finite-extensibility effects set in.
Iterative Beam Hardening Correction for Multi-Material Objects.
Zhao, Yunsong; Li, Mengfei
2015-01-01
In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum.
Design of the DEMO Fusion Reactor Following ITER
Garabedian, Paul R.; McFadden, Geoffrey B.
2009-01-01
Runs of the NSTAB nonlinear stability code show there are many three-dimensional (3D) solutions of the advanced tokamak problem subject to axially symmetric boundary conditions. These numerical simulations based on mathematical equations in conservation form predict that the ITER international tokamak project will encounter persistent disruptions and edge localized mode (ELMS) crashes. Test particle runs of the TRAN transport code suggest that for quasineutrality to prevail in tokamaks a certain minimum level of 3D asymmetry of the magnetic spectrum is required which is comparable to that found in quasiaxially symmetric (QAS) stellarators. The computational theory suggests that a QAS stellarator with two field periods and proportions like those of ITER is a good candidate for a fusion reactor. For a demonstration reactor (DEMO) we seek an experiment that combines the best features of ITER, with a system of QAS coils providing external rotational transform, which is a measure of the poloidal field. We have discovered a configuration with unusually good quasisymmetry that is ideal for this task. PMID:27504224
Experimental Evidence on Iterated Reasoning in Games
Grehl, Sascha; Tutić, Andreas
2015-01-01
We present experimental evidence on two forms of iterated reasoning in games, i.e. backward induction and interactive knowledge. Besides reliable estimates of the cognitive skills of the subjects, our design allows us to disentangle two possible explanations for the observed limits in performed iterated reasoning: Restrictions in subjects’ cognitive abilities and their beliefs concerning the rationality of co-players. In comparison to previous literature, our estimates regarding subjects’ skills in iterated reasoning are quite pessimistic. Also, we find that beliefs concerning the rationality of co-players are completely irrelevant in explaining the observed limited amount of iterated reasoning in the dirty faces game. In addition, it is demonstrated that skills in backward induction are a solid predictor for skills in iterated knowledge, which points to some generalized ability of the subjects in iterated reasoning. PMID:26312486
Divertor stray light analysis in JET-ILW and implications for the H-α diagnostic in ITER
NASA Astrophysics Data System (ADS)
Kukushkin, A. B.; Neverov, V. S.; Stamp, M. F.; Alekseev, A. G.; Brezinsek, S.; Gorshkov, A. V.; von Hellermann, M.; Kadomtsev, M. B.; Kotov, V.; Kukushkin, A. S.; Levashova, M. G.; Lisgo, S. W.; Lisitsa, V. S.; Shurygin, V. A.; Veshchev, E.; Vukolov, D. K.; Vukolov, K. Yu.; JET EFDA Contributors
2014-08-01
We report on the first results for the spectrum of divertor stray light (DSL) and the signal-to-background ratio for D-α light emitted from the far SOL and divertor in JET in the recent ITER-like wall (ILW) campaign. The results support the expectation of a strong impact of DSL upon the H-alpha (and Visible Light) Spectroscopy Diagnostic in ITER.
A fast poly-energetic iterative FBP algorithm
NASA Astrophysics Data System (ADS)
Lin, Yuan; Samei, Ehsan
2014-04-01
The beam hardening (BH) effect can influence medical interpretations in two notable ways. First, high attenuation materials, such as bones, can induce strong artifacts, which severely deteriorate the image quality. Second, voxel values can significantly deviate from the real values, which can lead to unreliable quantitative evaluation results. Some iterative methods have been proposed to eliminate the BH effect, but they cannot be widely applied for clinical practice because of the slow computational speed. The purpose of this study was to develop a new fast and practical poly-energetic iterative filtered backward projection algorithm (piFBP). The piFBP is composed of a novel poly-energetic forward projection process and a robust FBP-type backward updating process. In the forward projection process, an adaptive base material decomposition method is presented, based on which diverse body tissues (e.g., lung, fat, breast, soft tissue, and bone) and metal implants can be incorporated to accurately evaluate poly-energetic forward projections. In the backward updating process, one robust and fast FBP-type backward updating equation with a smoothing kernel is introduced to avoid the noise accumulation in the iteration process and to improve the convergence properties. Two phantoms were designed to quantitatively validate our piFBP algorithm in terms of the beam hardening index (BIdx) and the noise index (NIdx). The simulation results showed that piFBP possessed fast convergence speed, as the images could be reconstructed within four iterations. The variation range of the BIdx's of various tissues across phantom size and spectrum were reduced from [-7.5, 17.5] for FBP to [-0.1, 0.1] for piFBP while the NIdx's were maintained in the same low level (about [0.3, 1.7]). When a metal implant presented in a complex phantom, piFBP still had excellent reconstruction performance, as the variation range of the BIdx's of body tissues were reduced from [-2.9, 15.9] for FBP to [-0
Research at ITER towards DEMO: Specific reactor diagnostic studies to be carried out on ITER
Krasilnikov, A. V.; Kaschuck, Y. A.; Vershkov, V. A.; Petrov, A. A.; Petrov, V. G.; Tugarinov, S. N.
2014-08-21
In ITER diagnostics will operate in the very hard radiation environment of fusion reactor. Extensive technology studies are carried out during development of the ITER diagnostics and procedures of their calibration and remote handling. Results of these studies and practical application of the developed diagnostics on ITER will provide the direct input to DEMO diagnostic development. The list of DEMO measurement requirements and diagnostics will be determined during ITER experiments on the bases of ITER plasma physics results and success of particular diagnostic application in reactor-like ITER plasma. Majority of ITER diagnostic already passed the conceptual design phase and represent the state of the art in fusion plasma diagnostic development. The number of related to DEMO results of ITER diagnostic studies such as design and prototype manufacture of: neutron and γ–ray diagnostics, neutral particle analyzers, optical spectroscopy including first mirror protection and cleaning technics, reflectometry, refractometry, tritium retention measurements etc. are discussed.
Research at ITER towards DEMO: Specific reactor diagnostic studies to be carried out on ITER
NASA Astrophysics Data System (ADS)
Krasilnikov, A. V.; Kaschuck, Y. A.; Vershkov, V. A.; Petrov, A. A.; Petrov, V. G.; Tugarinov, S. N.
2014-08-01
In ITER diagnostics will operate in the very hard radiation environment of fusion reactor. Extensive technology studies are carried out during development of the ITER diagnostics and procedures of their calibration and remote handling. Results of these studies and practical application of the developed diagnostics on ITER will provide the direct input to DEMO diagnostic development. The list of DEMO measurement requirements and diagnostics will be determined during ITER experiments on the bases of ITER plasma physics results and success of particular diagnostic application in reactor-like ITER plasma. Majority of ITER diagnostic already passed the conceptual design phase and represent the state of the art in fusion plasma diagnostic development. The number of related to DEMO results of ITER diagnostic studies such as design and prototype manufacture of: neutron and γ-ray diagnostics, neutral particle analyzers, optical spectroscopy including first mirror protection and cleaning technics, reflectometry, refractometry, tritium retention measurements etc. are discussed.
Conditions for Lower Hybrid Current Drive in ITER
NASA Astrophysics Data System (ADS)
Cesario, R.; Amicucci, L.; Cardinali, A.; Castaldo, C.; Ceccuzzi, S.; Napoli, F.; Tuccillo, A. A.; Galli, A.; Schettini, G.
2012-12-01
To control the plasma current profile represents one of the most important problems of the research of nuclear fusion energy based on the tokamak concept, as in the plasma column the necessary conditions of stability and confinement should be satisfied. This problem can be solved by using the lower hybrid current drive (LHCD) effect, which was demonstrated to occur also at reactor grade high plasma densities provided that a proper method should be utilised, as assessed on FTU (Frascati Tokamak Upgrade). This method, based on theoretical predictions confirmed by experiment, produces relatively high electron temperature at the plasma periphery and scrape-off layer (SOL), consequently reducing the broadening of the spectrum launched by the antenna produced by parasitic wave physics of the edge, namely parametric instability (PI). The new results presented here show that, for kinetic profiles now foreseen for the SOL of ITER, PI is expected to hugely broaden the antenna spectrum and prevent any penetration in the core of the coupled LH power. However, considering the FTU method and assuming higher electron temperature at the edge (which would be however reasonable for ITER) the PI-produced spectral broadening would be mitigated, and enable the penetration of the coupled LH power in the main plasma. By successful LHCD effect, the control of the plasma current profile at normalised minor radius of about 0.8 would be possible, with much higher efficiency than that obtainable by other tools. A very useful reinforce of bootstrap current effects would be thus possible by LHCD in ITER.
Planning as an Iterative Process
NASA Technical Reports Server (NTRS)
Smith, David E.
2012-01-01
Activity planning for missions such as the Mars Exploration Rover mission presents many technical challenges, including oversubscription, consideration of time, concurrency, resources, preferences, and uncertainty. These challenges have all been addressed by the research community to varying degrees, but significant technical hurdles still remain. In addition, the integration of these capabilities into a single planning engine remains largely unaddressed. However, I argue that there is a deeper set of issues that needs to be considered namely the integration of planning into an iterative process that begins before the goals, objectives, and preferences are fully defined. This introduces a number of technical challenges for planning, including the ability to more naturally specify and utilize constraints on the planning process, the ability to generate multiple qualitatively different plans, and the ability to provide deep explanation of plans.
ITER Safety Analyses with ISAS
NASA Astrophysics Data System (ADS)
Gulden, W.; Nisan, S.; Porfiri, M.-T.; Toumi, I.; de Gramont, T. Boubée
1997-06-01
Detailed analyses of accident sequences for the International Thermonuclear Experimental Reactor (ITER), from an initiating event to the environmental release of activity, have involved in the past the use of different types of computer codes in a sequential manner. Since these codes were developed at different time scales in different countries, there is no common computing structure to enable automatic data transfer from one code to the other, and no possibility exists to model or to quantify the effect of coupled physical phenomena. To solve this problem, the Integrated Safety Analysis System of codes (ISAS) is being developed, which allows users to integrate existing computer codes in a coherent manner. This approach is based on the utilization of a command language (GIBIANE) acting as a “glue” to integrate the various codes as modules of a common environment. The present version of ISAS allows comprehensive (coupled) calculations of a chain of codes such as ATHENA (thermal-hydraulic analysis of transients and accidents), INTRA (analysis of in-vessel chemical reactions, pressure built-up, and distribution of reaction products inside the vacuum vessel and adjacent rooms), and NAUA (transport of radiological species within buildings and to the environment). In the near future, the integration of S AFALY (simultaneous analysis of plasma dynamics and thermal behavior of in-vessel components) is also foreseen. The paper briefly describes the essential features of ISAS development and the associated software architecture. It gives first results of a typical ITER accident sequence, a loss of coolant accident (LOCA) in the divertor cooling loop inside the vacuum vessel, amply demonstrating ISAS capabilities.
NASA Astrophysics Data System (ADS)
Xu, Shiyu; Zhang, Zhenxi; Chen, Ying
2014-03-01
Statistical iterative reconstruction exhibits particularly promising since it provides the flexibility of accurate physical noise modeling and geometric system description in transmission tomography system. However, to solve the objective function is computationally intensive compared to analytical reconstruction methods due to multiple iterations needed for convergence and each iteration involving forward/back-projections by using a complex geometric system model. Optimization transfer (OT) is a general algorithm converting a high dimensional optimization to a parallel 1-D update. OT-based algorithm provides a monotonic convergence and a parallel computing framework but slower convergence rate especially around the global optimal. Based on an indirect estimation on the spectrum of the OT convergence rate matrix, we proposed a successively increasing factor- scaled optimization transfer (OT) algorithm to seek an optimal step size for a faster rate. Compared to a representative OT based method such as separable parabolic surrogate with pre-computed curvature (PC-SPS), our algorithm provides comparable image quality (IQ) with fewer iterations. Each iteration retains a similar computational cost to PC-SPS. The initial experiment with a simulated Digital Breast Tomosynthesis (DBT) system shows that a total 40% computing time is saved by the proposed algorithm. In general, the successively increasing factor-scaled OT exhibits a tremendous potential to be a iterative method with a parallel computation, a monotonic and global convergence with fast rate.
The motional Stark effect diagnostic for ITER using a line-shift approach.
Foley, E L; Levinton, F M; Yuh, H Y; Zakharov, L E
2008-10-01
The United States has been tasked with the development and implementation of a motional Stark effect (MSE) system on ITER. In the harsh ITER environment, MSE is particularly susceptible to degradation, as it depends on polarimetry, and the polarization reflection properties of surfaces are highly sensitive to thin film effects due to plasma deposition and erosion of a first mirror. Here we present the results of a comprehensive study considering a new MSE-based approach to internal plasma magnetic field measurements for ITER. The proposed method uses the line shifts in the MSE spectrum (MSE-LS) to provide a radial profile of the magnetic field magnitude. To determine the utility of MSE-LS for equilibrium reconstruction, studies were performed using the ESC-ERV code system. A near-term opportunity to test the use of MSE-LS for equilibrium reconstruction is being pursued in the implementation of MSE with laser-induced fluorescence on NSTX. Though the field values and beam energies are very different from ITER, the use of a laser allows precision spectroscopy with a similar ratio of linewidth to line spacing on NSTX as would be achievable with a passive system on ITER. Simulation results for ITER and NSTX are presented, and the relative merits of the traditional line polarization approach and the new line-shift approach are discussed.
An accelerated subspace iteration for eigenvector derivatives
NASA Technical Reports Server (NTRS)
Ting, Tienko
1991-01-01
An accelerated subspace iteration method for calculating eigenvector derivatives has been developed. Factors affecting the effectiveness and the reliability of the subspace iteration are identified, and effective strategies concerning these factors are presented. The method has been implemented, and the results of a demonstration problem are presented.
Iterative methods for weighted least-squares
Bobrovnikova, E.Y.; Vavasis, S.A.
1996-12-31
A weighted least-squares problem with a very ill-conditioned weight matrix arises in many applications. Because of round-off errors, the standard conjugate gradient method for solving this system does not give the correct answer even after n iterations. In this paper we propose an iterative algorithm based on a new type of reorthogonalization that converges to the solution.
Rater Variables Associated with ITER Ratings
ERIC Educational Resources Information Center
Paget, Michael; Wu, Caren; McIlwrick, Joann; Woloschuk, Wayne; Wright, Bruce; McLaughlin, Kevin
2013-01-01
Advocates of holistic assessment consider the ITER a more authentic way to assess performance. But this assessment format is subjective and, therefore, susceptible to rater bias. Here our objective was to study the association between rater variables and ITER ratings. In this observational study our participants were clerks at the University of…
New concurrent iterative methods with monotonic convergence
Yao, Qingchuan
1996-12-31
This paper proposes the new concurrent iterative methods without using any derivatives for finding all zeros of polynomials simultaneously. The new methods are of monotonic convergence for both simple and multiple real-zeros of polynomials and are quadratically convergent. The corresponding accelerated concurrent iterative methods are obtained too. The new methods are good candidates for the application in solving symmetric eigenproblems.
Bayesian Vision for Shape Recovery
NASA Technical Reports Server (NTRS)
Jalobeanu, Andre
2004-01-01
We present a new Bayesian vision technique that aims at recovering a shape from two or more noisy observations taken under similar lighting conditions. The shape is parametrized by a piecewise linear height field, textured by a piecewise linear irradiance field, and we assume Gaussian Markovian priors for both shape vertices and irradiance variables. The observation process. also known as rendering, is modeled by a non-affine projection (e.g. perspective projection) followed by a convolution with a piecewise linear point spread function. and contamination by additive Gaussian noise. We assume that the observation parameters are calibrated beforehand. The major novelty of the proposed method consists of marginalizing out the irradiances considered as nuisance parameters, which is achieved by Laplace approximations. This reduces the inference to minimizing an energy that only depends on the shape vertices, and therefore allows an efficient Iterated Conditional Mode (ICM) optimization scheme to be implemented. A Gaussian approximation of the posterior shape density is computed, thus providing estimates both the geometry and its uncertainty. We illustrate the effectiveness of the new method by shape reconstruction results in a 2D case. A 3D version is currently under development and aims at recovering a surface from multiple images, reconstructing the topography by marginalizing out both albedo and shading.
DOE R&D Accomplishments Database
Bloch, F.; Staub, H.
1943-08-18
Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951
TRANSP simulations of ITER plasmas
Budny, R.V.; McCune, D.C.; Redi, M.H.; Schivell, J.; Wieland, R.M.
1995-12-01
The TRANSP code is used to construct comprehensive, self-consistent models for ITER discharges. Plasma parameters are studied for two discharges from the ITER ``Interim Design`` database producing 1.5 GW fusion power with a plasma current of 21 MA and 20 toroidal field coils generating 5.7 T Steady state profiles for T{sub ion}, T{sub e}, n{sub e}, Z{sub eff}, and P{sub rad} from the database are specified. TRANSP models the full up/down asymmetric plasma boundary within the separatrix. Effects of high-energy neutral beam injection, sawteeth mixing, toroidal field ripple, and helium ash transport are included. Results are given for the fusion rate profiles, and parameters describing effects such as alpha particle slowing down, the heating of electrons and thermal ions, and the thermalization rates. The deposition of 1 MeV neutral beam ions is predicted to peak near the plasma center, and the average beam ion energy is predicted to be half the injected energy. Sawtooth mixing is predicted to broaden the fast alpha profile. The toroidal ripple losses rate of alpha energy is estimated to be 3% before sawtooth crashes and to increase by a factor of three to four immediately following sawtooth crashes. Assumptions for the thermal He transport and the He recycling coefficient at the boundary are discussed. If the ratio of helium and energy confinement times, {tau}*{sub He}/{tau}{sub E} is less than 15, the steady state fusion power is predicted to 1.5 GW or greater. The values of the transport coefficients required for this fusion power depend on the He recycling coefficient at the separatrix. If R{sub rec} is near 1, the required He diffusivity must be much larger than that measured in tokamaks. If R{sub rec} {le} 0.50, and if the inward pinch is small, values comparable to those measured are compatible with 1.5 GW.
On the interplay between inner and outer iterations for a class of iterative methods
Giladi, E.
1994-12-31
Iterative algorithms for solving linear systems of equations often involve the solution of a subproblem at each step. This subproblem is usually another linear system of equations. For example, a preconditioned iteration involves the solution of a preconditioner at each step. In this paper, the author considers algorithms for which the subproblem is also solved iteratively. The subproblem is then said to be solved by {open_quotes}inner iterations{close_quotes} while the term {open_quotes}outer iteration{close_quotes} refers to a step of the basic algorithm. The cost of performing an outer iteration is dominated by the solution of the subproblem, and can be measured by the number of inner iterations. A good measure of the total amount of work needed to solve the original problem to some accuracy c is then, the total number of inner iterations. To lower the amount of work, one can consider solving the subproblems {open_quotes}inexactly{close_quotes} i.e. not to full accuracy. Although this diminishes the cost of solving each subproblem, it usually slows down the convergence of the outer iteration. It is therefore interesting to study the effect of solving each subproblem inexactly on the total amount of work. Specifically, the author considers strategies in which the accuracy to which the inner problem is solved, changes from one outer iteration to the other. The author seeks the `optimal strategy`, that is, the one that yields the lowest possible cost. Here, the author develops a methodology to find the optimal strategy, from the set of slowly varying strategies, for some iterative algorithms. This methodology is applied to the Chebychev iteration and it is shown that for Chebychev iteration, a strategy in which the inner-tolerance remains constant is optimal. The author also estimates this optimal constant. Then generalizations to other iterative procedures are discussed.
The Biokinetic Spectrum for Temperature
Corkrey, Ross; McMeekin, Tom A.; Bowman, John P.; Ratkowsky, David A.; Olley, June; Ross, Tom
2016-01-01
We identify and describe the distribution of temperature-dependent specific growth rates for life on Earth, which we term the biokinetic spectrum for temperature. The spectrum has the potential to provide for more robust modeling in thermal ecology since any conclusions derived from it will be based on observed data rather than using theoretical assumptions. It may also provide constraints for systems biology model predictions and provide insights in physiology. The spectrum has a Δ-shape with a sharp peak at around 42°C. At higher temperatures up to 60°C there was a gap of attenuated growth rates. We found another peak at 67°C and a steady decline in maximum rates thereafter. By using Bayesian quantile regression to summarise and explore the data we were able to conclude that the gap represented an actual biological transition between mesophiles and thermophiles that we term the Mesophile-Thermophile Gap (MTG). We have not identified any organism that grows above the maximum rate of the spectrum. We used a thermodynamic model to recover the Δ-shape, suggesting that the growth rate limits arise from a trade-off between activity and stability of proteins. The spectrum provides underpinning principles that will find utility in models concerned with the thermal responses of biological processes. PMID:27088362
Nonlinear photoluminescence spectrum of single gold nanostructures.
Knittel, Vanessa; Fischer, Marco P; de Roo, Tjaard; Mecking, Stefan; Leitenstorfer, Alfred; Brida, Daniele
2015-01-27
We investigate the multiphoton photoluminescence characteristics of gold nanoantennas fabricated from single crystals and polycrystalline films. By exciting these nanostructures with ultrashort pulses tunable in the near-infrared range, we observe distinct features in the broadband photoluminescence spectrum. By comparing antennas of different crystallinity and shape, we demonstrate that the nanoscopic geometry of plasmonic devices determines the shape of the emission spectra. Our findings rule out the contribution of the gold band structure in shaping the photoluminescence.
Modeling ITER ECH Waveguide Performance
NASA Astrophysics Data System (ADS)
Kaufman, M. C.; Lau, C. H.
2014-10-01
There are stringent requirements for mode purity and for on-target power as a percentage of source power for the ECH transmission lines on ITER. The design goal is less than 10% total power loss through the line and 95% HE11 mode at the diamond window. The dominant loss mechanism is mode conversion (MC) into higher order modes, and to maintain mode purity, these losses must be minimized. Miter bends and waveguide curvature are major sources of mode conversion. This work uses a code which calculates the mode conversion and attenuation of an arbitrary set of polarized waveguide modes in circular corrugated waveguide with non-zero axial curvature and miter bends. The transmission line is modeled as a structural beam with deformations due to misalignment of waveguide supports, tilts at the interfaces between waveguide sections, gravitational loading, and the extrusion and fabrication process. As these sources of curvature are statistical in nature, the resulting MC losses are found via Monte Carlo modeling. The results of this analysis will provide design guidance for waveguide support span lengths, requirements for minimum alignment offsets, and requirements for waveguide fabrication and quality control.
Progress on ITER Diagnostic Integration
NASA Astrophysics Data System (ADS)
Johnson, David; Feder, Russ; Klabacha, Jonathan; Loesser, Doug; Messineo, Mike; Stratton, Brentley; Wood, Rick; Zhai, Yuhu; Andrew, Phillip; Barnsley, Robin; Bertschinger, Guenter; Debock, Maarten; Reichle, Roger; Udintsev, Victor; Vayakis, George; Watts, Christopher; Walsh, Michael
2013-10-01
On ITER, front-end components must operate reliably in a hostile environment. Many will be housed in massive port plugs, which also shield the machine from radiation. Multiple diagnostics reside in a single plug, presenting new challenges for developers. Front-end components must tolerate thermally-induced stresses, disruption-induced mechanical loads, stray ECH radiation, displacement damage, and degradation due to plasma-induced coatings. The impact of failures is amplified due to the difficulty in performing robotic maintenance on these large structures. Motivated by needs to minimize disruption loads on the plugs, standardize the handling of shield modules, and decouple the parallel efforts of the many parties, the packaging strategy for diagnostics has recently focused on the use of 3 vertical shield modules inserted from the plasma side into each equatorial plug structure. At the front of each is a detachable first wall element with customized apertures. Progress on US equatorial and upper plugs will be used as examples, including the layout of components in the interspace and port cell regions. Supported by PPPL under contract DE-AC02-09CH11466 and UT-Battelle, LLC under contract DE-AC05-00OR22725 with the U.S. DOE.
Iterants, Fermions and Majorana Operators
NASA Astrophysics Data System (ADS)
Kauffman, Louis H.
Beginning with an elementary, oscillatory discrete dynamical system associated with the square root of minus one, we study both the foundations of mathematics and physics. Position and momentum do not commute in our discrete physics. Their commutator is related to the diffusion constant for a Brownian process and to the Heisenberg commutator in quantum mechanics. We take John Wheeler's idea of It from Bit as an essential clue and we rework the structure of that bit to a logical particle that is its own anti-particle, a logical Marjorana particle. This is our key example of the amphibian nature of mathematics and the external world. We show how the dynamical system for the square root of minus one is essentially the dynamics of a distinction whose self-reference leads to both the fusion algebra and the operator algebra for the Majorana Fermion. In the course of this, we develop an iterant algebra that supports all of matrix algebra and we end the essay with a discussion of the Dirac equation based on these principles.
Magnetic fusion and project ITER
Park, H.K.
1992-01-01
It has already been demonstrated that our economics and international relationship are impacted by an energy crisis. For the continuing prosperity of the human race, a new and viable energy source must be developed within the next century. It is evident that the cost will be high and will require a long term commitment to achieve this goal due to a high degree of technological and scientific knowledge. Energy from the controlled nuclear fusion is a safe, competitive, and environmentally attractive but has not yet been completely conquered. Magnetic fusion is one of the most difficult technological challenges. In modem magnetic fusion devices, temperatures that are significantly higher than the temperatures of the sun have been achieved routinely and the successful generation of tens of million watts as a result of scientific break-even is expected from the deuterium and tritium experiment within the next few years. For the practical future fusion reactor, we need to develop reactor relevant materials and technologies. The international project called International Thermonuclear Experimental Reactor (ITER)'' will fulfill this need and the success of this project will provide the most attractive long-term energy source for mankind.
Magnetic fusion and project ITER
Park, H.K.
1992-09-01
It has already been demonstrated that our economics and international relationship are impacted by an energy crisis. For the continuing prosperity of the human race, a new and viable energy source must be developed within the next century. It is evident that the cost will be high and will require a long term commitment to achieve this goal due to a high degree of technological and scientific knowledge. Energy from the controlled nuclear fusion is a safe, competitive, and environmentally attractive but has not yet been completely conquered. Magnetic fusion is one of the most difficult technological challenges. In modem magnetic fusion devices, temperatures that are significantly higher than the temperatures of the sun have been achieved routinely and the successful generation of tens of million watts as a result of scientific break-even is expected from the deuterium and tritium experiment within the next few years. For the practical future fusion reactor, we need to develop reactor relevant materials and technologies. The international project called ``International Thermonuclear Experimental Reactor (ITER)`` will fulfill this need and the success of this project will provide the most attractive long-term energy source for mankind.
Fu, Jian; Schleede, Simone; Tan, Renbo; Chen, Liyuan; Bech, Martin; Achterhold, Klaus; Gifford, Martin; Loewen, Rod; Ruth, Ronald; Pfeiffer, Franz
2013-09-01
Iterative reconstruction has a wide spectrum of proven advantages in the field of conventional X-ray absorption-based computed tomography (CT). In this paper, we report on an algebraic iterative reconstruction technique for grating-based differential phase-contrast CT (DPC-CT). Due to the differential nature of DPC-CT projections, a differential operator and a smoothing operator are added to the iterative reconstruction, compared to the one commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured at a two-grating interferometer setup. Since the algorithm is easy to implement and allows for the extension to various regularization possibilities, we expect a significant impact of the method for improving future medical and industrial DPC-CT applications.
Myers, N.J.
1994-12-31
The author gives a hybrid method for the iterative solution of linear systems of equations Ax = b, where the matrix (A) is nonsingular, sparse and nonsymmetric. As in a method developed by Starke and Varga the method begins with a number of steps of the Arnoldi method to produce some information on the location of the spectrum of A. This method then switches to an iterative method based on the Faber polynomials for an annular sector placed around these eigenvalue estimates. The Faber polynomials for an annular sector are used because, firstly an annular sector can easily be placed around any eigenvalue estimates bounded away from zero, and secondly the Faber polynomials are known analytically for an annular sector. Finally the author gives three numerical examples, two of which allow comparison with Starke and Varga`s results. The third is an example of a matrix for which many iterative methods would fall, but this method converges.
SPECIAL TOPIC: Global energy confinement H-mode database for ITER
NASA Astrophysics Data System (ADS)
Christiansen, J. P.; Cordey, J. G.; Thomsen, K.; Tanga, A.; DeBoo, J. C.; Schissel, D. P.; Taylor, T. S.; Kardaun, O. J. W. F.; Wagner, F.; Ryter, F.; Kaye, S. M.; Miura, Y.; Suzuki, N.; Mori, M.; Matsuda, T.; Tamai, H.; Takizuka, T.; Itoh, S.-I.; Itoh, K.
1992-02-01
Describes the content of an H-mode confinement database that has been assembled for the ITER project. Data were collected from six machines of different sizes and shapes: ASDEX, DIII-D, JET, JFT-2M, PBX-M and PDX. A detailed description of the criteria used in the selection of the data and the definition of each of the variables is given. The authors also present an analysis of the conditions of the database, the scalings (power law and offset linear) of the data with both dimensional and dimensionless variables, and predictions of the expected confinement time for ITER
High Precision Assembly Line Synthesis for Molecules with Tailored Shapes
Burns, Matthew; Essafi, Stephanie; Bame, Jessica R.; Bull, Stephanie P.; Webster, Matthew P.; Balieu, Sebastien; Dale, James W.; Butts, Craig P.; Harvey, Jeremy N.; Aggarwal, Varinder K.
2014-01-01
Molecular assembly lines, where molecules undergo iterative processes involving chain elongation and functional group manipulation are hallmarks of many processes found in Nature. We have sought to emulate Nature in the development of our own molecular assembly line through iterative homologations of boronic esters. Here we report a reagent (α-lithioethyl triispopropylbenzoate) which inserts into carbon-boron bonds with exceptionally high fidelity and stereocontrol. Through repeated iteration we have converted a simple boronic ester into a complex molecule (a carbon chain with ten contiguous methyl groups) with remarkably high precision over its length, its stereochemistry and therefore its shape. Different stereoisomers were targeted and it was found that they adopted different shapes (helical/linear) according to their stereochemistry. This work should now enable scientists to rationally design and create molecules with predictable shape, which could have an impact in all areas of molecular sciences where bespoke molecules are required. PMID:25209797
The Physics Basis of ITER Confinement
Wagner, F.
2009-02-19
ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.
Designing Diagnostics to Survive in ITER
NASA Astrophysics Data System (ADS)
Watts, Christopher; ITER Team
2014-10-01
Adapting diagnostics to withstand the incredibly harsh environment of the ITER D-T plasma is a formidable engineering task. Hindrances include not only the nuclear environment, but also the high radiative heat fluxes, high particle fluxes and stray ECH radiation. Strategies to mitigate the impact of these run the gamut from shielding, through recessing, through appropriate materials selection, to refurbishment. Examples include the Langmuir probe system, where individual probes are protected by passive heat shields; retroreflectors recessed into the tokamak first wall in deep, baffled tunnels; plasma mirror cleaning systems; electronics components like piezo crystals and x-ray detectors vetted for the nuclear environment. These and other ITER diagnostic system designs will be highlighted to emphasize their strategies for dealing with the ITER environment. *The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.
Archimedes' Pi--An Introduction to Iteration.
ERIC Educational Resources Information Center
Lotspeich, Richard
1988-01-01
One method (attributed to Archimedes) of approximating pi offers a simple yet interesting introduction to one of the basic ideas of numerical analysis, an iteration sequence. The method is described and elaborated. (PK)
Anderson Acceleration for Fixed-Point Iterations
Walker, Homer F.
2015-08-31
The purpose of this grant was to support research on acceleration methods for fixed-point iterations, with applications to computational frameworks and simulation problems that are of interest to DOE.
On the safety of ITER accelerators.
Li, Ge
2013-01-01
Three 1 MV/40A accelerators in heating neutral beams (HNB) are on track to be implemented in the International Thermonuclear Experimental Reactor (ITER). ITER may produce 500 MWt of power by 2026 and may serve as a green energy roadmap for the world. They will generate -1 MV 1 h long-pulse ion beams to be neutralised for plasma heating. Due to frequently occurring vacuum sparking in the accelerators, the snubbers are used to limit the fault arc current to improve ITER safety. However, recent analyses of its reference design have raised concerns. General nonlinear transformer theory is developed for the snubber to unify the former snubbers' different design models with a clear mechanism. Satisfactory agreement between theory and tests indicates that scaling up to a 1 MV voltage may be possible. These results confirm the nonlinear process behind transformer theory and map out a reliable snubber design for a safer ITER.
Hierarchical cosmic shear power spectrum inference
NASA Astrophysics Data System (ADS)
Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2016-02-01
We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.
Novel aspects of plasma control in ITER
NASA Astrophysics Data System (ADS)
Humphreys, D.; Ambrosino, G.; de Vries, P.; Felici, F.; Kim, S. H.; Jackson, G.; Kallenbach, A.; Kolemen, E.; Lister, J.; Moreau, D.; Pironti, A.; Raupp, G.; Sauter, O.; Schuster, E.; Snipes, J.; Treutterer, W.; Walker, M.; Welander, A.; Winter, A.; Zabeo, L.
2015-02-01
ITER plasma control design solutions and performance requirements are strongly driven by its nuclear mission, aggressive commissioning constraints, and limited number of operational discharges. In addition, high plasma energy content, heat fluxes, neutron fluxes, and very long pulse operation place novel demands on control performance in many areas ranging from plasma boundary and divertor regulation to plasma kinetics and stability control. Both commissioning and experimental operations schedules provide limited time for tuning of control algorithms relative to operating devices. Although many aspects of the control solutions required by ITER have been well-demonstrated in present devices and even designed satisfactorily for ITER application, many elements unique to ITER including various crucial integration issues are presently under development. We describe selected novel aspects of plasma control in ITER, identifying unique parts of the control problem and highlighting some key areas of research remaining. Novel control areas described include control physics understanding (e.g., current profile regulation, tearing mode (TM) suppression), control mathematics (e.g., algorithmic and simulation approaches to high confidence robust performance), and integration solutions (e.g., methods for management of highly subscribed control resources). We identify unique aspects of the ITER TM suppression scheme, which will pulse gyrotrons to drive current within a magnetic island, and turn the drive off following suppression in order to minimize use of auxiliary power and maximize fusion gain. The potential role of active current profile control and approaches to design in ITER are discussed. Issues and approaches to fault handling algorithms are described, along with novel aspects of actuator sharing in ITER.
Programmable Iterative Optical Image And Data Processing
NASA Technical Reports Server (NTRS)
Jackson, Deborah J.
1995-01-01
Proposed method of iterative optical image and data processing overcomes limitations imposed by loss of optical power after repeated passes through many optical elements - especially, beam splitters. Involves selective, timed combination of optical wavefront phase conjugation and amplification to regenerate images in real time to compensate for losses in optical iteration loops; timing such that amplification turned on to regenerate desired image, then turned off so as not to regenerate other, undesired images or spurious light propagating through loops from unwanted reflections.
Iterative methods based upon residual averaging
NASA Technical Reports Server (NTRS)
Neuberger, J. W.
1980-01-01
Iterative methods for solving boundary value problems for systems of nonlinear partial differential equations are discussed. The methods involve subtracting an average of residuals from one approximation in order to arrive at a subsequent approximation. Two abstract methods in Hilbert space are given and application of these methods to quasilinear systems to give numerical schemes for such problems is demonstrated. Potential theoretic matters related to the iteration schemes are discussed.
Threshold power and energy confinement for ITER
Takizuka, T.
1996-12-31
In order to predict the threshold power for L-H transition and the energy confinement performance in ITER, assembling of database and analyses of them have been progressed. The ITER Threshold Database includes data from 10 divertor tokamaks. Investigation of the database gives a scaling of the threshold power of the form P{sub thr} {proportional_to} B{sub t} n{sub e}{sup 0.75} R{sup 2} {times} (n{sub e} R{sup 2}){sup +-0.25}, which predicts P{sub thr} = 100 {times} 2{sup 0{+-}1} MW for ITER at n{sub e} = 5 {times} 10{sup 19} m{sup {minus}3}. The ITER L-mode Confinement Database has also been expanded by data from 14 tokamaks. A scaling of the thermal energy confinement time in L-mode and ohmic phases is obtained; {tau}{sub th} {approximately} I{sub p} R{sup 1.8} n{sub e}{sup 0.4{sub P{sup {minus}0.73}}}. At the ITER parameter, it becomes about 2.2 sec. For the ignition in ITER, more than 2.5 times of improvement will be required from the L-mode. The ITER H-mode Confinement Database is expanded from data of 6 tokamaks to data of 11 tokamaks. A {tau}{sub th} scaling for ELMy H-mode obtained by a standard regression analysis predicts the ITER confinement time of {tau}{sub th} = 6 {times} (1 {+-} 0.3) sec. The degradation of {tau}{sub th} with increasing n{sub e} R{sup 2} (or decreasing {rho}{sub *}) is not found for ELMy H-mode. An offset linear law scaling with a dimensionally correct form also predicts nearly the same {tau}{sub th} value.
Novel aspects of plasma control in ITER
Humphreys, D.; Jackson, G.; Walker, M.; Welander, A.; Ambrosino, G.; Pironti, A.; Felici, F.; Kallenbach, A.; Raupp, G.; Treutterer, W.; Kolemen, E.; Lister, J.; Sauter, O.; Moreau, D.; Schuster, E.
2015-02-15
ITER plasma control design solutions and performance requirements are strongly driven by its nuclear mission, aggressive commissioning constraints, and limited number of operational discharges. In addition, high plasma energy content, heat fluxes, neutron fluxes, and very long pulse operation place novel demands on control performance in many areas ranging from plasma boundary and divertor regulation to plasma kinetics and stability control. Both commissioning and experimental operations schedules provide limited time for tuning of control algorithms relative to operating devices. Although many aspects of the control solutions required by ITER have been well-demonstrated in present devices and even designed satisfactorily for ITER application, many elements unique to ITER including various crucial integration issues are presently under development. We describe selected novel aspects of plasma control in ITER, identifying unique parts of the control problem and highlighting some key areas of research remaining. Novel control areas described include control physics understanding (e.g., current profile regulation, tearing mode (TM) suppression), control mathematics (e.g., algorithmic and simulation approaches to high confidence robust performance), and integration solutions (e.g., methods for management of highly subscribed control resources). We identify unique aspects of the ITER TM suppression scheme, which will pulse gyrotrons to drive current within a magnetic island, and turn the drive off following suppression in order to minimize use of auxiliary power and maximize fusion gain. The potential role of active current profile control and approaches to design in ITER are discussed. Issues and approaches to fault handling algorithms are described, along with novel aspects of actuator sharing in ITER.
Ocean color spectrum calculations
NASA Technical Reports Server (NTRS)
Mccluney, W. R.
1974-01-01
There is obvious value in developing the means for measuring a number of subsurface oceanographic parameters using remotely sensed ocean color data. The first step in this effort should be the development of adequate theoretical models relating the desired oceanographic parameters to the upwelling radiances to be observed. A portion of a contributory theoretical model can be described by a modified single scattering approach based on a simple treatment of multiple scattering. The resulting quasisingle scattering model can be used to predict the upwelling distribution of spectral radiance emerging from the sea. The shape of the radiance spectrum predicted by this model for clear ocean water shows encouraging agreement with measurements made at the edge of the Sargasso Sea off Cape Hatteras.
Shofner, W P; Yost, W A
1997-08-01
Iterated rippled noise having infinite iterations is generated when a flat-spectrum wideband noise is delayed T ms and the delayed version is added to the undelayed noise through positive feedback. The resulting signal has a rippled spectrum, and the perceived pitch of this iterated rippled noise by human listeners corresponds to a frequency of 1/T. We have previously demonstrated that chinchillas can discriminate the rippled-spectrum noise from the flat-spectrum noise. In the present study, chinchillas discriminated a bandpass filtered rippled-spectrum noise from a bandpass flat-spectrum noise in a psychophysical task. The passbands were set to be one octave wide. Psychometric functions were obtained for 5 chinchillas and performance was measured as d'. The best behavioral performance was obtained when the center frequency of the bandpass filter generally corresponded to the 3rd 5th harmonic peak of the rippled noise (i.e., at 3/T to 5/T), but the precise location of the dominant region varied with the delay of the rippled noise such that the dominance region tended to shift to lower harmonics as 1/T increased. These results indicate that not all spectral regions are weighted equally in the discrimination task. The spectral dominance region found in chinchillas is similar to that described for human pitch perception.
Progress and Design Status of the ITER MSE Diagnostic
Makowski, M A; Allen, S L; Holcomb, C T; Lerner, S; Morris, K; Wong, N
2008-05-07
The Motional Stark Effect (MSE) diagnostic will be essential for the study of advanced scenarios on ITER and its design is currently underway. In order meet the ITER MSE diagnostic design requirements, two approaches for the measurement are under consideration. The first is based on standard polarimeter techniques to measure the polarization of the emitted light, whereas the second measures the Stark splitting from which |B| can be inferred, where |B| is the magnitude of the total magnetic field. The baseline design of the optical system is centered on the first approach. Emphasis in this case is placed on minimizing the polarization aberrations of the optical relay system. Motivation for the second method results from concern that the optical properties of the plasma-facing mirror, particularly its diattenuation and retardance, will degrade with plasma exposure. The second approach, while less sensitive to aberrations induced by plasma exposure effects, requires greater optical throughput in order to measure the complete Stark spectrum. We have developed optimized designs for both techniques and will present a comparison of them and discuss the associated design trade-offs.
EDITORIAL: ECRH physics and technology in ITER
NASA Astrophysics Data System (ADS)
Luce, T. C.
2008-05-01
It is a great pleasure to introduce you to this special issue containing papers from the 4th IAEA Technical Meeting on ECRH Physics and Technology in ITER, which was held 6-8 June 2007 at the IAEA Headquarters in Vienna, Austria. The meeting was attended by more than 40 ECRH experts representing 13 countries and the IAEA. Presentations given at the meeting were placed into five separate categories EC wave physics: current understanding and extrapolation to ITER Application of EC waves to confinement and stability studies, including active control techniques for ITER Transmission systems/launchers: state of the art and ITER relevant techniques Gyrotron development towards ITER needs System integration and optimisation for ITER. It is notable that the participants took seriously the focal point of ITER, rather than simply contributing presentations on general EC physics and technology. The application of EC waves to ITER presents new challenges not faced in the current generation of experiments from both the physics and technology viewpoints. High electron temperatures and the nuclear environment have a significant impact on the application of EC waves. The needs of ITER have also strongly motivated source and launcher development. Finally, the demonstrated ability for precision control of instabilities or non-inductive current drive in addition to bulk heating to fusion burn has secured a key role for EC wave systems in ITER. All of the participants were encouraged to submit their contributions to this special issue, subject to the normal publication and technical merit standards of Nuclear Fusion. Almost half of the participants chose to do so; many of the others had been published in other publications and therefore could not be included in this special issue. The papers included here are a representative sample of the meeting. The International Advisory Committee also asked the three summary speakers from the meeting to supply brief written summaries (O. Sauter
Modelling the physics in iterative reconstruction for transmission computed tomography
Nuyts, Johan; De Man, Bruno; Fessler, Jeffrey A.; Zbijewski, Wojciech; Beekman, Freek J.
2013-01-01
There is an increasing interest in iterative reconstruction (IR) as a key tool to improve quality and increase applicability of X-ray CT imaging. IR has the ability to significantly reduce patient dose, it provides the flexibility to reconstruct images from arbitrary X-ray system geometries and it allows to include detailed models of photon transport and detection physics, to accurately correct for a wide variety of image degrading effects. This paper reviews discretisation issues and modelling of finite spatial resolution, Compton scatter in the scanned object, data noise and the energy spectrum. Widespread implementation of IR with highly accurate model-based correction, however, still requires significant effort. In addition, new hardware will provide new opportunities and challenges to improve CT with new modelling. PMID:23739261
NASA Astrophysics Data System (ADS)
Tanaka, Yasuyuki T.; Becerra Gonzalez, Josefa; Itoh, Ryosuke; Finke, Justin D.; Inoue, Yoshiyuki; Ojha, Roopesh; Carpenter, Bryce; Lindfors, Elina; Krauß, Felicia; Desiante, Rachele; Shiki, Kensei; Fukazawa, Yasushi; Longo, Francesco; McEnery, Julie E.; Buson, Sara; Nilsson, Kari; Fallah Ramazani, Vandad; Reinthal, Riho; Takalo, Leo; Pursimo, Tapio; Boschin, Walter
2016-08-01
We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1-compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ± 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous (<1 d) broad-band spectrum with a one-zone synchrotron plus inverse-Compton model revealed that GeV/TeV emission could be produced by inverse-Compton scattering of external photons from the dust torus. We emphasize that a flaring blazar showing high flux of ≳1.0 × 10-6 photons cm-2 s-1 (E > 100 MeV) and a hard spectral index of ΓGeV < 2.0 detected by Fermi-LAT on daily timescales is a promising target for TeV follow-up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.
Model coil for the international thermonuclear experimental reactor (ITER) magnet systems
NASA Astrophysics Data System (ADS)
Okuno, K.
1994-07-01
The model coil program for the ITER EDA includes the manufacture and testing of one Central Solenoid (CS) model coil and one Toroidal Field (TF) model coil, and test facility preparations. The CS model coil has an inner diameter of 1.6 m and produces a full field of 13 T. The TF model coil is race-track shaped with an outer dimension of 3 m x 4 m. It will be tested in conjunction with an LCT coil to simulate mechanical load conditions. Different kinds of conductors can be tested as inserts to be placed in the bore of the CS model coil. Two facilities at JAERI and KfK can provide ITER-relevant conditions for testing the model coils and inserts. The model coil program will validate the ITER magnet design and the manufacturing feasibility.
Continuous Spectrum of Trigonometric Rosen-Morse and Eckart Potentials from Free Particle Spectrum
NASA Astrophysics Data System (ADS)
Panahi, H.; Pouraram, H.
2011-06-01
The shape invariant symmetry of the Trigonometric Rosen-Morse and Eckart potentials has been studied through realization of so(3) and so(2,1) Lie algebras respectively. In this work, by using the free particle eigenfunction, we obtain continuous spectrum of these potentials by means of their shape invariance symmetry in an algebraic method.
PREFACE: Progress in the ITER Physics Basis
NASA Astrophysics Data System (ADS)
Ikeda, K.
2007-06-01
I would firstly like to congratulate all who have contributed to the preparation of the `Progress in the ITER Physics Basis' (PIPB) on its publication and express my deep appreciation of the hard work and commitment of the many scientists involved. With the signing of the ITER Joint Implementing Agreement in November 2006, the ITER Members have now established the framework for construction of the project, and the ITER Organization has begun work at Cadarache. The review of recent progress in the physics basis for burning plasma experiments encompassed by the PIPB will be a valuable resource for the project and, in particular, for the current Design Review. The ITER design has been derived from a physics basis developed through experimental, modelling and theoretical work on the properties of tokamak plasmas and, in particular, on studies of burning plasma physics. The `ITER Physics Basis' (IPB), published in 1999, has been the reference for the projection methodologies for the design of ITER, but the IPB also highlighted several key issues which needed to be resolved to provide a robust basis for ITER operation. In the intervening period scientists of the ITER Participant Teams have addressed these issues intensively. The International Tokamak Physics Activity (ITPA) has provided an excellent forum for scientists involved in these studies, focusing their work on the high priority physics issues for ITER. Significant progress has been made in many of the issues identified in the IPB and this progress is discussed in depth in the PIPB. In this respect, the publication of the PIPB symbolizes the strong interest and enthusiasm of the plasma physics community for the success of the ITER project, which we all recognize as one of the great scientific challenges of the 21st century. I wish to emphasize my appreciation of the work of the ITPA Coordinating Committee members, who are listed below. Their support and encouragement for the preparation of the PIPB were
Efficient iterative image reconstruction algorithm for dedicated breast CT
NASA Astrophysics Data System (ADS)
Antropova, Natalia; Sanchez, Adrian; Reiser, Ingrid S.; Sidky, Emil Y.; Boone, John; Pan, Xiaochuan
2016-03-01
Dedicated breast computed tomography (bCT) is currently being studied as a potential screening method for breast cancer. The X-ray exposure is set low to achieve an average glandular dose comparable to that of mammography, yielding projection data that contains high levels of noise. Iterative image reconstruction (IIR) algorithms may be well-suited for the system since they potentially reduce the effects of noise in the reconstructed images. However, IIR outcomes can be difficult to control since the algorithm parameters do not directly correspond to the image properties. Also, IIR algorithms are computationally demanding and have optimal parameter settings that depend on the size and shape of the breast and positioning of the patient. In this work, we design an efficient IIR algorithm with meaningful parameter specifications and that can be used on a large, diverse sample of bCT cases. The flexibility and efficiency of this method comes from having the final image produced by a linear combination of two separately reconstructed images - one containing gray level information and the other with enhanced high frequency components. Both of the images result from few iterations of separate IIR algorithms. The proposed algorithm depends on two parameters both of which have a well-defined impact on image quality. The algorithm is applied to numerous bCT cases from a dedicated bCT prototype system developed at University of California, Davis.
Chevron beam dump for ITER edge Thomson scattering system
NASA Astrophysics Data System (ADS)
Yatsuka, E.; Hatae, T.; Vayakis, G.; Bassan, M.; Itami, K.
2013-10-01
This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.
Chevron beam dump for ITER edge Thomson scattering system.
Yatsuka, E; Hatae, T; Vayakis, G; Bassan, M; Itami, K
2013-10-01
This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.
Comparison of Iterative and Non-Iterative Strain-Gage Balance Load Calculation Methods
NASA Technical Reports Server (NTRS)
Ulbrich, N.
2010-01-01
The accuracy of iterative and non-iterative strain-gage balance load calculation methods was compared using data from the calibration of a force balance. Two iterative and one non-iterative method were investigated. In addition, transformations were applied to balance loads in order to process the calibration data in both direct read and force balance format. NASA's regression model optimization tool BALFIT was used to generate optimized regression models of the calibration data for each of the three load calculation methods. This approach made sure that the selected regression models met strict statistical quality requirements. The comparison of the standard deviation of the load residuals showed that the first iterative method may be applied to data in both the direct read and force balance format. The second iterative method, on the other hand, implicitly assumes that the primary gage sensitivities of all balance gages exist. Therefore, the second iterative method only works if the given balance data is processed in force balance format. The calibration data set was also processed using the non-iterative method. Standard deviations of the load residuals for the three load calculation methods were compared. Overall, the standard deviations show very good agreement. The load prediction accuracies of the three methods appear to be compatible as long as regression models used to analyze the calibration data meet strict statistical quality requirements. Recent improvements of the regression model optimization tool BALFIT are also discussed in the paper.
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NASA Astrophysics Data System (ADS)
Izzo, Dario; Petazzi, Lorenzo
2006-08-01
We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.
Current status of the ITER MSE diagnostic
NASA Astrophysics Data System (ADS)
Yuh, Howard; Levinton, F.; La Fleur, H.; Foley, E.; Feder, R.; Zakharov, L.
2013-10-01
The U.S. is providing ITER with a Motional Stark Effect (MSE) diagnostic to provide a measurement to guide reconstructions of the plasma q-profile. The diagnostic design has gone through many iterations, driven primarily by the evolution of the ITER port plug design and the steering of the heating beams. The present two port, three view design viewing both heating beams and the DNB has recently passed a conceptual design review at the IO. The traditional line polarization (MSE-LP) technique employed on many devices around the world faces many challenges in ITER, including strong background light and mirror degradation. To mitigate these effects, a multi-wavelength polarimeter and high resolution spectrometer will be used to subtract polarized background, while retroreflecting polarizers will provide mirror calibration concurrent with MSE-LP measurements. However, without a proven plasma-facing mirror cleaning technique, inherent risks to MSE-LP remain. The high field and high beam energy on ITER offers optimal conditions for a spectroscopic measurement of the electric field using line splitting (MSE-LS), a technique which does not depend on mirror polarization properties. The current design is presented with a roadmap of the R&D needed to address remaining challenges. This work is supported by DOE contracts S009627-R and S012380-F.
Iterative scatter correction based on artifact assessment
NASA Astrophysics Data System (ADS)
Wiegert, Jens; Hohmann, Steffen; Bertram, Matthias
2008-03-01
In this paper we propose a novel scatter correction methodology for X-ray based cone-beam CT that allows to combine the advantages of projection-based and volume-based correction approaches. The basic idea is to use a potentially non-optimal projection-based scatter correction method and to iteratively optimize its performance by repeatedly assessing remaining scatter-induced artifacts in intermediately reconstructed volumes. The novel approach exploits the fact that due to the flatness of the scatter-background, compensation itself is most easily performed in the projection-domain, while the scatter-induced artifacts can be better observed in the reconstructed volume. The presented method foresees to evaluate the scatter correction efficiency after each iteration by means of a quantitative measure characterizing the amount of residual cupping and to adjust the parameters of the projection-based scatter correction for the next iteration accordingly. The potential of this iterative scatter correction approach is demonstrated using voxelized Monte Carlo scatter simulations as ground truth. Using the proposed iterative scatter correction method, remarkable scatter correction performance was achieved both using simple parametric heuristic techniques as well as by optimizing previously published scatter estimation schemes. For the human head, scatter induced artifacts were reduced from initially 148 HU to less than 8.1 HU to 9.1 HU for different studied methods, corresponding to an artifact reduction exceeding 93%.
Primordial power spectrum from Planck
Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org
2014-11-01
Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near ℓ ∼ 750–850 represents the most prominent feature in the data. Feature near ℓ ∼ 1800–2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ∼ 2.5%. In this context low-ℓ and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.
SPECIAL TOPIC: ITER H mode confinement database update
NASA Astrophysics Data System (ADS)
Thomsen, K.; Campbell, D. J.; Cordey, J. G.; Kardaun, O. J. W. F.; Ryter, F.; Stroth, U.; Kus, A.; DeBoo, J. C.; Schissel, D. P.; Miura, Y.; Suzuki, N.; Mori, M.; Matsuda, T.; Tamai, H.; Takizuka, T.; Itoh, S.-I.; Itoh, K.; Kaye, S. M.
1994-01-01
This paper describes an update of the H mode confinement database that has been assembled for the ITER project. Data were collected from six machines of different sizes and shapes: ASDEX, DIII-D, JET, JFT-2M, PBX-M and PDX. The updated database contains better estimates of fast ion energy content and thermal energy confinement times, discharges with RF heating, data using boronization, beryllium and pellets, more systematic parameter scans, and other features. The list of variables in the database has been expanded, and the selection criteria for the standard dataset have been modified. We also present simple scalings of the total and thermal energy confinement time to the new dataset
An iterative contractive framework for probe methods: LASSO
NASA Astrophysics Data System (ADS)
Potthast, R. W. E.
2011-10-01
We present a new iterative approach called Line Adaptation for the Singular Sources Objective (LASSO) to object or shape reconstruction based on the singular sources method (or probe method) for the reconstruction of scatterers from the far-field pattern of scattered acoustic or electromagnetic waves. The scheme is based on the construction of an indicator function given by the scattered field for incident point sources in its source point from the given far-field patterns for plane waves. The indicator function is then used to drive the contraction of a surface which surrounds the unknown scatterers. A stopping criterion for those parts of the surfaces that touch the unknown scatterers is formulated. A splitting approach for the contracting surfaces is formulated, such that scatterers consisting of several separate components can be reconstructed. Convergence of the scheme is shown, and its feasibility is demonstrated using a numerical study with several examples.
ITER Experts' meeting on density limits
Borrass, K.; Igitkhanov, Y.L.; Uckan, N.A.
1989-12-01
The necessity of achieving a prescribed wall load or fusion power essentially determines the plasma pressure in a device like ITER. The range of operation densities and temperatures compatible with this condition is constrained by the problems of power exhaust and the disruptive density limit. The maximum allowable heat loads on the divertor plates and the maximum allowable sheath edge temperature practically impose a lower limit on the operating densities, whereas the disruptive density limit imposes an upper limit. For most of the density limit scalings proposed in the past an overlap of the two constraints or at best a very narrow accessible density range is predicted for ITER. Improved understanding of the underlying mechanisms is therefore a crucial issue in order to provide a more reliable basis for extrapolation to ITER and to identify possible ways of alleviating the problem.
Accelerating an iterative process by explicit annihilation
NASA Technical Reports Server (NTRS)
Jespersen, D. C.; Buning, P. G.
1985-01-01
A slowly convergent stationary iterative process can be accelerated by explicitly annihilating (i.e., eliminating) the dominant eigenvector component of the error. The dominant eigenvalue or complex pair of eigenvalues can be estimated from the solution during the iteration. The corresponding eigenvector or complex pair of eigenvectors can then be annihilated by applying an explicit Richardson process over the basic iterative method. This can be done entirely in real arithmetic by analytically combining the complex conjugate annihilation steps. The technique is applied to an implicit algorithm for the calculation of two dimensional steady transonic flow over a circular cylinder using the equations of compressible inviscid gas dynamics. This demonstrates the use of explicit annihilation on a nonlinear problem.
Accelerating an iterative process by explicit annihilation
NASA Technical Reports Server (NTRS)
Jespersen, D. C.; Buning, P. G.
1983-01-01
A slowly convergent stationary iterative process can be accelerated by explicitly annihilating (i.e., eliminating) the dominant eigenvector component of the error. The dominant eigenvalue or complex pair of eigenvalues can be estimated from the solution during the iteration. The corresponding eigenvector or complex pair of eigenvectors can then be annihilated by applying an explicit Richardson process over the basic iterative method. This can be done entirely in real arithmetic by analytically combining the complex conjugate annihilation steps. The technique is applied to an implicit algorithm for the calculation of two dimensional steady transonic flow over a circular cylinder using the equations of compressible inviscid gas dynamics. This demonstrates the use of explicit annihilation on a nonlinear problem.
Re-starting an Arnoldi iteration
Lehoucq, R.B.
1996-12-31
The Arnoldi iteration is an efficient procedure for approximating a subset of the eigensystem of a large sparse n x n matrix A. The iteration produces a partial orthogonal reduction of A into an upper Hessenberg matrix H{sub m} of order m. The eigenvalues of this small matrix H{sub m} are used to approximate a subset of the eigenvalues of the large matrix A. The eigenvalues of H{sub m} improve as estimates to those of A as m increases. Unfortunately, so does the cost and storage of the reduction. The idea of re-starting the Arnoldi iteration is motivated by the prohibitive cost associated with building a large factorization.
Translating relational queries into iterative programs
Freytag, J.C.
1987-01-01
This book investigates the problem of translating relational queries into iterative programs using methods and techniques from the areas of functional programming and program transformation. The first part presents two algorithms which generate iterative programs from algebra-based query specifications. While the first algorithm is based on the transformation of recursive programs, the second uses functional expressions to generate the final iterative form. In the second part the same techniques generate efficient programs for the evaluation of aggregate functions in relational database systems. In several steps, programs which perform aggregation after sorting, are transformed into programs which perform aggregation while sorting. The third part then investigates the Lisp-dialect T as a possible implementation language for database systems.
Lousteau, D.C.
1994-09-01
The overall programmatic objective, as defined in the ITER Engineering Design Activities (EDA) Agreement, is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. The ITER EDA Phase, due to last until July 1998, will encompass the design of the device and its auxiliary systems and facilities, including the preparation of engineering drawings. The EDA also incorporates validating research and development (R&D) work, including the development and testing of key components. The purpose of this paper is to review the status of the design, as it has been developed so far, emphasizing the design and integration of those components contained within the vacuum vessel of the ITER device. The components included in the in-vessel systems are divertor and first wall; blanket and shield; plasma heating, fueling, and vacuum pumping equipment; and remote handling equipment.
NASA Astrophysics Data System (ADS)
Kandel, Yudhishthir; Denbeaux, Gregory
2016-08-01
We develop a novel iterative method to accurately measure electron beam shape (current density distribution) and monotonic material response as a function of position. A common method is to scan an electron beam across a knife edge along many angles to give an approximate measure of the beam profile, however such scans are not easy to obtain in all systems. The present work uses only an electron beam and multiple exposed regions of a thin film of photoresist to measure the complete beam profile for any beam shape, where the material response is characterized externally. This simplifies the setup of new experimental tools. We solve for self-consistent photoresist thickness loss response to dose and the electron beam profile simultaneously by optimizing a novel functional iteratively. We also show the successful implementation of the method in a real world data set corrupted by noise and other experimental variabilities.
Design finalization and material qualification towards procurement of the ITER vacuum vessel
NASA Astrophysics Data System (ADS)
Ioki, K.; Barabash, V.; Bachmann, C.; Chappuis, P.; Choi, C. H.; Cordier, J.-J.; Giraud, B.; Gribov, Y.; Heitzenroeder, Ph.; Her, N.; Johnson, G.; Jones, L.; Jun, C.; Kim, B. C.; Kuzmin, E.; Loesser, D.; Martin, A.; Merola, M.; Pathak, H.; Readman, P.; Sugihara, M.; Terasawa, A.; Utin, Yu.; Wang, X.; Wu, S.; Yu, J.; ITER Organization; ITER Parties
2011-10-01
Procurement arrangements for ITER key components including the vacuum vessel (VV) have been signed and the ITER activities are now fully devoted towards construction. Final design reviews have been carried out for the main vessel and ports. One of the design review topics is the selection of materials, material procurement, and assessment of material performance during operation. The width of the inner shell splice plates was increased from 120 mm to 160 mm to minimize risk during the assembly of the Thermal shields and the VV. Instead of facet shaping, 3D shaping was introduced for the outboard inner shell. The material qualification procedures have been started for VV structural materials such as 316L(N) IG for licensing as a nuclear pressure equipment component. In accordance with the regulatory requirements and quality requirements for operation, common material specifications have been prepared in collaboration with the domestic agencies.
Global Asymptotic Behavior of Iterative Implicit Schemes
NASA Technical Reports Server (NTRS)
Yee, H. C.; Sweby, P. K.
1994-01-01
The global asymptotic nonlinear behavior of some standard iterative procedures in solving nonlinear systems of algebraic equations arising from four implicit linear multistep methods (LMMs) in discretizing three models of 2 x 2 systems of first-order autonomous nonlinear ordinary differential equations (ODEs) is analyzed using the theory of dynamical systems. The iterative procedures include simple iteration and full and modified Newton iterations. The results are compared with standard Runge-Kutta explicit methods, a noniterative implicit procedure, and the Newton method of solving the steady part of the ODEs. Studies showed that aside from exhibiting spurious asymptotes, all of the four implicit LMMs can change the type and stability of the steady states of the differential equations (DEs). They also exhibit a drastic distortion but less shrinkage of the basin of attraction of the true solution than standard nonLMM explicit methods. The simple iteration procedure exhibits behavior which is similar to standard nonLMM explicit methods except that spurious steady-state numerical solutions cannot occur. The numerical basins of attraction of the noniterative implicit procedure mimic more closely the basins of attraction of the DEs and are more efficient than the three iterative implicit procedures for the four implicit LMMs. Contrary to popular belief, the initial data using the Newton method of solving the steady part of the DEs may not have to be close to the exact steady state for convergence. These results can be used as an explanation for possible causes and cures of slow convergence and nonconvergence of steady-state numerical solutions when using an implicit LMM time-dependent approach in computational fluid dynamics.
Challenges and status of ITER conductor production
NASA Astrophysics Data System (ADS)
Devred, A.; Backbier, I.; Bessette, D.; Bevillard, G.; Gardner, M.; Jong, C.; Lillaz, F.; Mitchell, N.; Romano, G.; Vostner, A.
2014-04-01
Taking the relay of the large Hadron collider (LHC) at CERN, ITER has become the largest project in applied superconductivity. In addition to its technical complexity, ITER is also a management challenge as it relies on an unprecedented collaboration of seven partners, representing more than half of the world population, who provide 90% of the components as in-kind contributions. The ITER magnet system is one of the most sophisticated superconducting magnet systems ever designed, with an enormous stored energy of 51 GJ. It involves six of the ITER partners. The coils are wound from cable-in-conduit conductors (CICCs) made up of superconducting and copper strands assembled into a multistage cable, inserted into a conduit of butt-welded austenitic steel tubes. The conductors for the toroidal field (TF) and central solenoid (CS) coils require about 600 t of Nb3Sn strands while the poloidal field (PF) and correction coil (CC) and busbar conductors need around 275 t of Nb-Ti strands. The required amount of Nb3Sn strands far exceeds pre-existing industrial capacity and has called for a significant worldwide production scale up. The TF conductors are the first ITER components to be mass produced and are more than 50% complete. During its life time, the CS coil will have to sustain several tens of thousands of electromagnetic (EM) cycles to high current and field conditions, way beyond anything a large Nb3Sn coil has ever experienced. Following a comprehensive R&D program, a technical solution has been found for the CS conductor, which ensures stable performance versus EM and thermal cycling. Productions of PF, CC and busbar conductors are also underway. After an introduction to the ITER project and magnet system, we describe the ITER conductor procurements and the quality assurance/quality control programs that have been implemented to ensure production uniformity across numerous suppliers. Then, we provide examples of technical challenges that have been encountered and
Tracking Solar Events through Iterative Refinement
NASA Astrophysics Data System (ADS)
Kempton, D. J.; Angryk, R. A.
2015-11-01
In this paper, we combine two approaches to multiple-target tracking: the first is a hierarchical approach to iteratively growing track fragments across gaps in detections; the second is a network flow based optimization method for data association. The network flow based optimization method is utilized for data association in an iteratively growing manner. This process is applied to solar data, retrieved from the Heliophysics Event Knowledge base (HEK) and utilizes precomputed image parameter values. These precomputed image parameter values are used to compare visual similarity of detected events, to determine the best matching track fragment associations, which leads to a globally optimal track fragment association hypothesis.
Fatigue tests on the ITER PF jacket
NASA Astrophysics Data System (ADS)
Qin, Jinggang; Weiss, Klaus-Peter; Wu, Yu; Wu, Zhixiong; Li, Laifeng; Liu, Sheng
2012-10-01
This paper focuses on fatigue tests on the ITER Poloidal Field (PF) jacket made of 316L stainless steel material. During manufacture, the conductor will be compacted and spooled after cable insertion. Therefore, sample jackets were prepared under compaction, bending and straightening in order to simulate the status of PF conductor during manufacturing and winding. The fatigue properties of materials were measured at T < 7 K, including S-N and fatigue crack growth rate (FCGR). The testing results show that the present Chinese PF jacket has good fatigue properties, which conclude that the results are accordant with the requirements of ITER.
Iterative method for generating correlated binary sequences
NASA Astrophysics Data System (ADS)
Usatenko, O. V.; Melnik, S. S.; Apostolov, S. S.; Makarov, N. M.; Krokhin, A. A.
2014-11-01
We propose an efficient iterative method for generating random correlated binary sequences with a prescribed correlation function. The method is based on consecutive linear modulations of an initially uncorrelated sequence into a correlated one. Each step of modulation increases the correlations until the desired level has been reached. The robustness and efficiency of the proposed algorithm are tested by generating sequences with inverse power-law correlations. The substantial increase in the strength of correlation in the iterative method with respect to single-step filtering generation is shown for all studied correlation functions. Our results can be used for design of disordered superlattices, waveguides, and surfaces with selective transport properties.
A novel resistance iterative algorithm for CCOS
NASA Astrophysics Data System (ADS)
Zheng, Ligong; Zhang, Xuejun
2006-08-01
CCOS (Computer Control Optical Surfacing) technology is widely used for making aspheric mirrors. For most manufacturers, dwell time algorithm is usually employed to determine the route and dwell time of the small tools to converge the errors. In this article, a novel damp iterative algorithm is proposed. We chose revolutions of the small tool instead of dwell time to determine fabrication stratagem. By using resistance iterative algorithm, we can solve these revolutions. Several mirrors have been manufactured by this method, all of them have fulfilled the demand of the designers, a 1m aspheric mirror was finished within 3 months.
Stability of a radiative mantle in ITER
Mahdavi, M.A.; Staebler, G.M.; Wood, R.D.; Whyte, D.G.; West, W.P.
1996-12-01
We report results of a study to evaluate the efficacy of various impurities for heat dispersal by a radiative mantle and radiative divertor(including SOL). We have derived a stability criterion for the mantle radiation which favors low Z impurities and low ratios of edge to core thermal conductivities. Since on the other hand the relative strength of boundary line radiation to core bremsstrahlung favors high Z impurities, we find that for the ITER physics phase argon is the best gaseous impurity for mantle radiation. For the engineering phase of ITER, more detailed analysis is needed to select between krypton and argon.
Scheduling and rescheduling with iterative repair
NASA Technical Reports Server (NTRS)
Zweben, Monte; Davis, Eugene; Daun, Brian; Deale, Michael
1992-01-01
This paper describes the GERRY scheduling and rescheduling system being applied to coordinate Space Shuttle Ground Processing. The system uses constraint-based iterative repair, a technique that starts with a complete but possibly flawed schedule and iteratively improves it by using constraint knowledge within repair heuristics. In this paper we explore the tradeoff between the informedness and the computational cost of several repair heuristics. We show empirically that some knowledge can greatly improve the convergence speed of a repair-based system, but that too much knowledge, such as the knowledge embodied within the MIN-CONFLICTS lookahead heuristic, can overwhelm a system and result in degraded performance.
Tritium Pumps for ITER Roughing System
Antipenkov, Alexander; Day, Christian; Mack, August; Wagner, Robert; Laesser, Rainer
2005-07-15
The ITER roughing system provides for both the initial pump-down of the vessel itself and the regular pump-out of the batch-regenerating cryopumps. This system must have a large pumping speed and cope with the radioactive gas tritium at the same time. The present paper shall highlight the results of the ITER roughing train optimization, discuss the modification of a Roots pump for tritium, and present the results of a ferrofluidic seal test and the first tests of a tailor-made tritium-proof Roots pump with inactive gases.
CORRIGENDUM: Main safety issues at the transition from ITER to fusion power plants
NASA Astrophysics Data System (ADS)
Gulden, W.; Ciattaglia, S.; Massaut, V.; Sardain, P.
2007-09-01
In parallel to the ITER design process and in close cooperation with the designers a fusion-specific safety approach was developed and implemented. Detailed safety assessments have been performed and documented in the ITER Generic Site Safety Report (GSSR). Following the decision on ITER construction in France, results from the GSSR and from on-going safety-related activities tailored to the Cadarache site and the French licensing process are now being used to write the ITER Preliminary Safety Analysis Report. In the most recent European fusion power plant conceptual study (PPCS) inherent fusion favourable features have been exploited, by appropriate design and choice of materials, to provide major safety and environmental advantages. The study focused on five power plant models, which are illustrative of a wider spectrum of possibilities. These span a range from relatively near-term concepts, based on limited technology and plasma physics extrapolations, to a more advanced conception. All five PPCS plant models differ substantially in their plasma physics, blanket and divertor technology, size, fusion power and materials compositions, and these differences lead to differences in economic performance and in the details of safety and environmental impacts. This paper uses the quite detailed information available from ITER safety documents and highlights the differences between ITER and future fusion power plants. The main areas investigated are releases and doses during normal operation and under accidental conditions, occupational radiation exposure and optimization and waste management, including recycling and/or final disposal in repositories. Due to an error, an incorrect version of this paper was published in issue 7. For the convenience of the reader we have included the correct full article below rather than a list of changes.
Wang, Jinguo; Zhao, Zhiqin Song, Jian; Chen, Guoping; Nie, Zaiping; Liu, Qing-Huo
2015-05-15
Purpose: An iterative reconstruction method has been previously reported by the authors of this paper. However, the iterative reconstruction method was demonstrated by solely using the numerical simulations. It is essential to apply the iterative reconstruction method to practice conditions. The objective of this work is to validate the capability of the iterative reconstruction method for reducing the effects of acoustic heterogeneity with the experimental data in microwave induced thermoacoustic tomography. Methods: Most existing reconstruction methods need to combine the ultrasonic measurement technology to quantitatively measure the velocity distribution of heterogeneity, which increases the system complexity. Different to existing reconstruction methods, the iterative reconstruction method combines time reversal mirror technique, fast marching method, and simultaneous algebraic reconstruction technique to iteratively estimate the velocity distribution of heterogeneous tissue by solely using the measured data. Then, the estimated velocity distribution is used subsequently to reconstruct the highly accurate image of microwave absorption distribution. Experiments that a target placed in an acoustic heterogeneous environment are performed to validate the iterative reconstruction method. Results: By using the estimated velocity distribution, the target in an acoustic heterogeneous environment can be reconstructed with better shape and higher image contrast than targets that are reconstructed with a homogeneous velocity distribution. Conclusions: The distortions caused by the acoustic heterogeneity can be efficiently corrected by utilizing the velocity distribution estimated by the iterative reconstruction method. The advantage of the iterative reconstruction method over the existing correction methods is that it is successful in improving the quality of the image of microwave absorption distribution without increasing the system complexity.
Plane wave spectrum of electromagnetic beams
NASA Astrophysics Data System (ADS)
Doicu, A.; Wriedt, T.
1997-02-01
A plane wave spectrum method of Gaussian beams can be derived by using Davis' approximations for the vector potential. An equivalent vector potential is introduced by considering the inverse Fourier transform of the spectrum function of the original vector potential in a given plane. The electromagnetic field, which corresponds to the equivalent vector potential, satisfies Maxwell's equations and can be written as a sum of plane waves. The beam shape coefficients, or the expansion coefficients in terms of regular spherical vector wave functions, are expressed as simple integrals. This version of the plane wave spectrum method offers the possibility to compute higher-order corrections for Gaussian beams.
Cathodoluminescence Spectrum Imaging Software
2011-04-07
The software developed for spectrum imaging is applied to the analysis of the spectrum series generated by our cathodoluminescence instrumentation. This software provides advanced processing capabilities s such: reconstruction of photon intensity (resolved in energy) and photon energy maps, extraction of the spectrum from selected areas, quantitative imaging mode, pixel-to-pixel correlation spectrum line scans, ASCII, output, filling routines, drift correction, etc.
Superordinate Shape Classification Using Natural Shape Statistics
ERIC Educational Resources Information Center
Wilder, John; Feldman, Jacob; Singh, Manish
2011-01-01
This paper investigates the classification of shapes into broad natural categories such as "animal" or "leaf". We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their parameters within each…
Iterative solution of the Helmholtz equation
Larsson, E.; Otto, K.
1996-12-31
We have shown that the numerical solution of the two-dimensional Helmholtz equation can be obtained in a very efficient way by using a preconditioned iterative method. We discretize the equation with second-order accurate finite difference operators and take special care to obtain non-reflecting boundary conditions. We solve the large, sparse system of equations that arises with the preconditioned restarted GMRES iteration. The preconditioner is of {open_quotes}fast Poisson type{close_quotes}, and is derived as a direct solver for a modified PDE problem.The arithmetic complexity for the preconditioner is O(n log{sub 2} n), where n is the number of grid points. As a test problem we use the propagation of sound waves in water in a duct with curved bottom. Numerical experiments show that the preconditioned iterative method is very efficient for this type of problem. The convergence rate does not decrease dramatically when the frequency increases. Compared to banded Gaussian elimination, which is a standard solution method for this type of problems, the iterative method shows significant gain in both storage requirement and arithmetic complexity. Furthermore, the relative gain increases when the frequency increases.
Constructing Easily Iterated Functions with Interesting Properties
ERIC Educational Resources Information Center
Sprows, David J.
2009-01-01
A number of schools have recently introduced new courses dealing with various aspects of iteration theory or at least have found ways of including topics such as chaos and fractals in existing courses. In this note, we will consider a family of functions whose members are especially well suited to illustrate many of the concepts involved in these…
First mirrors for diagnostic systems of ITER
NASA Astrophysics Data System (ADS)
Litnovsky, A.; Voitsenya, V. S.; Costley, A.; Donné, A. J. H.; SWG on First Mirrors of the ITPA Topical Group on Diagnostics
2007-08-01
The majority of optical diagnostics presently foreseen for ITER will implement in-vessel metallic mirrors as plasma-viewing components. Mirrors are used for the observation of the plasma radiation in a very wide wavelength range: from about 1 nm up to a few mm. In the hostile ITER environment, mirrors are subject to erosion, deposition, particle implantation and other adverse effects which will change their optical properties, affecting the entire performance of the respective diagnostic systems. The Specialists Working Group (SWG) on first mirrors was established under the wings of the International Tokamak Physics Activity (ITPA) Topical Group (TG) on Diagnostics to coordinate and guide the investigations on diagnostic mirrors towards the development of optimal, robust and durable solutions for ITER diagnostic systems. The results of tests of various ITER-candidate mirror materials, performed in Tore-Supra, TEXTOR, DIII-D, TCV, T-10, TRIAM-1M and LHD under various plasma conditions, as well as an overview of laboratory investigations of mirror performance and mirror cleaning techniques are presented in the paper. The current tasks in the R&D of diagnostic mirrors will be addressed.
Asymptotic iteration approach to supersymmetric bistable potentials
NASA Astrophysics Data System (ADS)
Ciftci, H.; Özer, O.; P., Roy
2012-01-01
We examine quasi exactly solvable bistable potentials and their supersymmetric partners within the framework of the asymptotic iteration method (AIM). It is shown that the AIM produces excellent approximate spectra and that sometimes it is found to be more useful to use the partner potential for computation. We also discuss the direct application of the AIM to the Fokker—Planck equation.
Matched filter based iterative adaptive approach
NASA Astrophysics Data System (ADS)
Nepal, Ramesh; Zhang, Yan Rockee; Li, Zhengzheng; Blake, William
2016-05-01
Matched Filter sidelobes from diversified LPI waveform design and sensor resolution are two important considerations in radars and active sensors in general. Matched Filter sidelobes can potentially mask weaker targets, and low sensor resolution not only causes a high margin of error but also limits sensing in target-rich environment/ sector. The improvement in those factors, in part, concern with the transmitted waveform and consequently pulse compression techniques. An adaptive pulse compression algorithm is hence desired that can mitigate the aforementioned limitations. A new Matched Filter based Iterative Adaptive Approach, MF-IAA, as an extension to traditional Iterative Adaptive Approach, IAA, has been developed. MF-IAA takes its input as the Matched Filter output. The motivation here is to facilitate implementation of Iterative Adaptive Approach without disrupting the processing chain of traditional Matched Filter. Similar to IAA, MF-IAA is a user parameter free, iterative, weighted least square based spectral identification algorithm. This work focuses on the implementation of MF-IAA. The feasibility of MF-IAA is studied using a realistic airborne radar simulator as well as actual measured airborne radar data. The performance of MF-IAA is measured with different test waveforms, and different Signal-to-Noise (SNR) levels. In addition, Range-Doppler super-resolution using MF-IAA is investigated. Sidelobe reduction as well as super-resolution enhancement is validated. The robustness of MF-IAA with respect to different LPI waveforms and SNR levels is also demonstrated.
Iteration of Complex Functions and Newton's Method
ERIC Educational Resources Information Center
Dwyer, Jerry; Barnard, Roger; Cook, David; Corte, Jennifer
2009-01-01
This paper discusses some common iterations of complex functions. The presentation is such that similar processes can easily be implemented and understood by undergraduate students. The aim is to illustrate some of the beauty of complex dynamics in an informal setting, while providing a couple of results that are not otherwise readily available in…
On the safety of ITER accelerators
Li, Ge
2013-01-01
Three 1 MV/40A accelerators in heating neutral beams (HNB) are on track to be implemented in the International Thermonuclear Experimental Reactor (ITER). ITER may produce 500 MWt of power by 2026 and may serve as a green energy roadmap for the world. They will generate −1 MV 1 h long-pulse ion beams to be neutralised for plasma heating. Due to frequently occurring vacuum sparking in the accelerators, the snubbers are used to limit the fault arc current to improve ITER safety. However, recent analyses of its reference design have raised concerns. General nonlinear transformer theory is developed for the snubber to unify the former snubbers' different design models with a clear mechanism. Satisfactory agreement between theory and tests indicates that scaling up to a 1 MV voltage may be possible. These results confirm the nonlinear process behind transformer theory and map out a reliable snubber design for a safer ITER. PMID:24008267
Solving Differential Equations Using Modified Picard Iteration
ERIC Educational Resources Information Center
Robin, W. A.
2010-01-01
Many classes of differential equations are shown to be open to solution through a method involving a combination of a direct integration approach with suitably modified Picard iterative procedures. The classes of differential equations considered include typical initial value, boundary value and eigenvalue problems arising in physics and…
ITER faces further five-year delay
NASA Astrophysics Data System (ADS)
Clery, Daniel
2016-06-01
The €14bn ITER fusion reactor currently under construction in Cadarache, France, will require an additional cash injection of €4.6bn if it is to start up in 2025 - a target date that is already five years later than currently scheduled.
Microtearing Instability In The ITER Pedestal
Wong, K. L.; Mikkelsen, D. R.; Rewoldt, G. M.; Budny, R.
2010-12-01
Unstable microtearing modes are discovered by the GS2 gyrokinetic siimulation code, in the pedestal region of a simulated ITER H-mode plasma with approximately 400 WM DT fusion power. Existing nonlinear theory indicates that these instabilities should produce stochastic magnetic fields and broaden the pedestal. The resulted electron thermal conductivity is estimated and the implications of these findings are discussed.
Iteration and Anxiety in Mathematical Literature
ERIC Educational Resources Information Center
Capezzi, Rita; Kinsey, L. Christine
2016-01-01
We describe our experiences in team-teaching an honors seminar on mathematics and literature. We focus particularly on two of the texts we read: Georges Perec's "How to Ask Your Boss for a Raise" and Alain Robbe-Grillet's "Jealousy," both of which make use of iterative structures.
Development of advanced inductive scenarios for ITER
NASA Astrophysics Data System (ADS)
Luce, T. C.; Challis, C. D.; Ide, S.; Joffrin, E.; Kamada, Y.; Politzer, P. A.; Schweinzer, J.; Sips, A. C. C.; Stober, J.; Giruzzi, G.; Kessel, C. E.; Murakami, M.; Na, Y.-S.; Park, J. M.; Polevoi, A. R.; Budny, R. V.; Citrin, J.; Garcia, J.; Hayashi, N.; Hobirk, J.; Hudson, B. F.; Imbeaux, F.; Isayama, A.; McDonald, D. C.; Nakano, T.; Oyama, N.; Parail, V. V.; Petrie, T. W.; Petty, C. C.; Suzuki, T.; Wade, M. R.; the ITPA Integrated Operation Scenario Topical Group Members; the ASDEX-Upgrade Team; the DIII-D Team; EFDA Contributors, JET; the JT-60U Team
2014-01-01
Since its inception in 2002, the International Tokamak Physics Activity topical group on Integrated Operational Scenarios (IOS) has coordinated experimental and modelling activity on the development of advanced inductive scenarios for applications in the ITER tokamak. The physics basis and the prospects for applications in ITER have been advanced significantly during that time, especially with respect to experimental results. The principal findings of this research activity are as follows. Inductive scenarios capable of higher normalized pressure (βN ⩾ 2.4) than the ITER baseline scenario (βN = 1.8) with normalized confinement at or above the standard H-mode scaling are well established under stationary conditions on the four largest diverted tokamaks (AUG, DIII-D, JET, JT-60U), demonstrated in a database of more than 500 plasmas from these tokamaks analysed here. The parameter range where high performance is achieved is broad in q95 and density normalized to the empirical density limit. MHD modes can play a key role in reaching stationary high performance, but also define the limits to achieved stability and confinement. Projection of performance in ITER from existing experiments uses empirical scalings and theory-based modelling. The status of the experimental validation of both approaches is summarized here. The database shows significant variation in the energy confinement normalized to standard H-mode confinement scalings, indicating the possible influence of additional physics variables absent from the scalings. Tests using the available information on rotation and the ratio of the electron and ion temperatures indicate neither of these variables in isolation can explain the variation in normalized confinement observed. Trends in the normalized confinement with the two dimensionless parameters that vary most from present-day experiments to ITER, gyroradius and collision frequency, are significant. Regression analysis on the multi-tokamak database has been
Modelling of hybrid scenario: from present-day experiments towards ITER
NASA Astrophysics Data System (ADS)
Litaudon, X.; Voitsekhovitch, I.; Artaud, J. F.; Belo, P.; Bizarro, João P. S.; Casper, T.; Citrin, J.; Fable, E.; Ferreira, J.; Garcia, J.; Garzotti, L.; Giruzzi, G.; Hobirk, J.; Hogeweij, G. M. D.; Imbeaux, F.; Joffrin, E.; Koechl, F.; Liu, F.; Lönnroth, J.; Moreau, D.; Parail, V.; Schneider, M.; Snyder, P. B.; the ASDEX-Upgrade Team; Contributors, JET-EFDA; the EU-ITM ITER Scenario Modelling Group
2013-07-01
The ‘hybrid’ scenario is an attractive operating scenario for ITER since it combines long plasma duration with the reliability of the reference H-mode regime. We review the recent European modelling effort carried out within the Integrated Scenario Modelling group which aims at (i) understanding the underlying physics of the hybrid regime in ASDEX-Upgrade and JET and (ii) extrapolating them towards ITER. JET and ASDEX-Upgrade hybrid scenarios performed under different experimental conditions have been simulated in an interpretative and predictive way in order to address the current profile dynamics and its link with core confinement, the relative importance of magnetic shear, s, and E × B flow shear on the core turbulence, pedestal stability and H-L transition. The correlation of the improved confinement with an increased s/q at outer radii observed in JET and ASDEX-Upgrade discharges is consistent with the predictions based on the GLF23 model applied in the simulations of the ion and electron kinetic profiles. Projections to ITER hybrid scenarios have been carried out focusing on optimization of the heating/current drive schemes to reach and ultimately control the desired plasma equilibrium using ITER actuators. Firstly, access condition to the hybrid-like q-profiles during the current ramp-up phase has been investigated. Secondly, from the interpreted role of the s/q ratio, ITER hybrid scenario flat-top performance has been optimized through tailoring the q-profile shape and pedestal conditions. EPED predictions of pedestal pressure and width have been used as constraints in the interpretative modelling while the core heat transport is predicted by GLF23. Finally, model-based approach for real-time control of advanced tokamak scenarios has been applied to ITER hybrid regime for simultaneous magnetic and kinetic profile control.
Testing Short Samples of ITER Conductors and Projection of Their Performance in ITER Magnets
Martovetsky, N N
2007-08-20
Qualification of the ITER conductor is absolutely necessary. Testing large scale conductors is expensive and time consuming. To test straight 3-4m long samples in a bore of a split solenoid is a relatively economical way in comparison with fabrication of a coil to be tested in a bore of a background field solenoid. However, testing short sample may give ambiguous results due to different constraints in current redistribution in the cable or other end effects which are not present in the large magnet. This paper discusses processes taking place in the ITER conductor, conditions when conductor performance could be distorted and possible signal processing to deduce behavior of ITER conductors in ITER magnets from the test data.
Object motion tracking in the NDE laboratory by random sample iterative closest point
NASA Astrophysics Data System (ADS)
Radkowski, Rafael; Wehr, David; Gregory, Elizabeth; Holland, Stephen D.
2016-02-01
We present a computationally efficient technique for real-time motion tracking in the NDE laboratory. Our goal is to track object shapes in an flash thermography test stand to determine the position and orientation of the specimen which facilitates to register thermography data to a 3D part model. Object shapes can be different specimens and fixtures. Specimens can be manually aligned at any test stand, the position and orientation of every a-priori known shape can be computed and forwarded to the data management software. Our technique relies on the random sample consensus (RANSAC) approach to the iterative closest point (ICP) problem for identifying object shapes, thus, it is robust in different situations. The paper introduces the computational techniques and experiments along with the results.
Reducing the latency of the Fractal Iterative Method to half an iteration
NASA Astrophysics Data System (ADS)
Béchet, Clémentine; Tallon, Michel
2013-12-01
The fractal iterative method for atmospheric tomography (FRiM-3D) has been introduced to solve the wavefront reconstruction at the dimensions of an ELT with a low-computational cost. Previous studies reported the requirement of only 3 iterations of the algorithm in order to provide the best adaptive optics (AO) performance. Nevertheless, any iterative method in adaptive optics suffer from the intrinsic latency induced by the fact that one iteration can start only once the previous one is completed. Iterations hardly match the low-latency requirement of the AO real-time computer. We present here a new approach to avoid iterations in the computation of the commands with FRiM-3D, thus allowing low-latency AO response even at the scale of the European ELT (E-ELT). The method highlights the importance of "warm-start" strategy in adaptive optics. To our knowledge, this particular way to use the "warm-start" has not been reported before. Futhermore, removing the requirement of iterating to compute the commands, the computational cost of the reconstruction with FRiM-3D can be simplified and at least reduced to half the computational cost of a classical iteration. Thanks to simulations of both single-conjugate and multi-conjugate AO for the E-ELT,with FRiM-3D on Octopus ESO simulator, we demonstrate the benefit of this approach. We finally enhance the robustness of this new implementation with respect to increasing measurement noise, wind speed and even modeling errors.
Overview on Experiments On ITER-like Antenna On JET And ICRF Antenna Design For ITER
Nightingale, M. P. S.; Blackman, T.; Edwards, D.; Fanthome, J.; Graham, M.; Hamlyn-Harris, C.; Hancock, D.; Jacquet, P.; Mayoral, M.-L.; Monakhov, I.; Nicholls, K.; Stork, D.; Whitehurst, A.; Wilson, D.; Wooldridge, E.
2009-11-26
Following an overview of the ITER Ion Cyclotron Resonance Frequency (ICRF) system, the JET ITER-like antenna (ILA) will be described. The ILA was designed to test the following ITER issues: (a) reliable operation at power densities of order 8 MW/m{sup 2} at voltages up to 45 kV using a close-packed array of straps; (b) powering through ELMs using an internal (in-vacuum) conjugate-T junction; (c) protection from arcing in a conjugate-T configuration, using both existing and novel systems; and (d) resilience to disruption forces. ITER-relevant results have been achieved: operation at high coupled power density; control of the antenna matching elements in the presence of high inter-strap coupling, use of four conjugate-T systems (as would be used in ITER, should a conjugate-T approach be used); operation with RF voltages on the antenna structures up to 42 kV; achievement of ELM tolerance with a conjugate-T configuration by operating at 3{omega} real impedance at the conjugate-T point; and validation of arc detection systems on conjugate-T configurations in ELMy H-mode plasmas. The impact of these results on the predicted performance and design of the ITER antenna will be reviewed. In particular, the implications of the RF coupling measured on JET will be discussed.
Iterative performance of various formulations of the SPN equations
NASA Astrophysics Data System (ADS)
Zhang, Yunhuang; Ragusa, Jean C.; Morel, Jim E.
2013-11-01
In this paper, the Standard, Composite, and Canonical forms of the Simplified PN (SPN) equations are reviewed and their corresponding iterative properties are compared. The Gauss-Seidel (FLIP), Explicit, and preconditioned Source Iteration iterative schemes have been analyzed for both isotropic and highly anisotropic (Fokker-Planck) scattering. The iterative performance of the various SPN forms is assessed using Fourier analysis, corroborated with numerical experiments.
He's iteration formulation for solving nonlinear algebraic equations
NASA Astrophysics Data System (ADS)
Qian, W.-X.; Ye, Y.-H.; Chen, J.; Mo, L.-F.
2008-02-01
Newton iteration method is sensitive to initial guess and its slope. To overcome the shortcoming, He's iteration method is used to solve nonlinear algebraic equations where Newton iteration method becomes invalid. Some examples are given, showing that the method is effective.
Lee, Seung Yup; Skolnick, Jeffrey
2007-07-01
To improve the accuracy of TASSER models especially in the limit where threading provided template alignments are of poor quality, we have developed the TASSER(iter) algorithm which uses the templates and contact restraints from TASSER generated models for iterative structure refinement. We apply TASSER(iter) to a large benchmark set of 2,773 nonhomologous single domain proteins that are < or = 200 in length and that cover the PDB at the level of 35% pairwise sequence identity. Overall, TASSER(iter) models have a smaller global average RMSD of 5.48 A compared to 5.81 A RMSD of the original TASSER models. Classifying the targets by the level of prediction difficulty (where Easy targets have a good template with a corresponding good threading alignment, Medium targets have a good template but a poor alignment, and Hard targets have an incorrectly identified template), TASSER(iter) (TASSER) models have an average RMSD of 4.15 A (4.35 A) for the Easy set and 9.05 A (9.52 A) for the Hard set. The largest reduction of average RMSD is for the Medium set where the TASSER(iter) models have an average global RMSD of 5.67 A compared to 6.72 A of the TASSER models. Seventy percent of the Medium set TASSER(iter) models have a smaller RMSD than the TASSER models, while 63% of the Easy and 60% of the Hard TASSER models are improved by TASSER(iter). For the foldable cases, where the targets have a RMSD to the native <6.5 A, TASSER(iter) shows obvious improvement over TASSER models: For the Medium set, it improves the success rate from 57.0 to 67.2%, followed by the Hard targets where the success rate improves from 32.0 to 34.8%, with the smallest improvement in the Easy targets from 82.6 to 84.0%. These results suggest that TASSER(iter) can provide more reliable predictions for targets of Medium difficulty, a range that had resisted improvement in the quality of protein structure predictions.
Precise and fast spatial-frequency analysis using the iterative local Fourier transform.
Lee, Sukmock; Choi, Heejoo; Kim, Dae Wook
2016-09-19
The use of the discrete Fourier transform has decreased since the introduction of the fast Fourier transform (fFT), which is a numerically efficient computing process. This paper presents the iterative local Fourier transform (ilFT), a set of new processing algorithms that iteratively apply the discrete Fourier transform within a local and optimal frequency domain. The new technique achieves 2^{10} times higher frequency resolution than the fFT within a comparable computation time. The method's superb computing efficiency, high resolution, spectrum zoom-in capability, and overall performance are evaluated and compared to other advanced high-resolution Fourier transform techniques, such as the fFT combined with several fitting methods. The effectiveness of the ilFT is demonstrated through the data analysis of a set of Talbot self-images (1280 × 1024 pixels) obtained with an experimental setup using grating in a diverging beam produced by a coherent point source.
Precise and fast spatial-frequency analysis using the iterative local Fourier transform.
Lee, Sukmock; Choi, Heejoo; Kim, Dae Wook
2016-09-19
The use of the discrete Fourier transform has decreased since the introduction of the fast Fourier transform (fFT), which is a numerically efficient computing process. This paper presents the iterative local Fourier transform (ilFT), a set of new processing algorithms that iteratively apply the discrete Fourier transform within a local and optimal frequency domain. The new technique achieves 2^{10} times higher frequency resolution than the fFT within a comparable computation time. The method's superb computing efficiency, high resolution, spectrum zoom-in capability, and overall performance are evaluated and compared to other advanced high-resolution Fourier transform techniques, such as the fFT combined with several fitting methods. The effectiveness of the ilFT is demonstrated through the data analysis of a set of Talbot self-images (1280 × 1024 pixels) obtained with an experimental setup using grating in a diverging beam produced by a coherent point source. PMID:27661946
Iterative Fourier transform algorithm: different approaches to diffractive optical element design
NASA Astrophysics Data System (ADS)
Skeren, Marek; Richter, Ivan; Fiala, Pavel
2002-10-01
This contribution focuses on the study and comparison of different design approaches for designing phase-only diffractive optical elements (PDOEs) for different possible applications in laser beam shaping. Especially, new results and approaches, concerning the iterative Fourier transform algorithm, are analyzed, implemented, and compared. Namely, various approaches within the iterative Fourier transform algorithm (IFTA) are analyzed for the case of phase-only diffractive optical elements with quantizied phase levels (either binary or multilevel structures). First, the general scheme of the IFTA iterative approach with partial quantization is briefly presented and discussed. Then, the special assortment of the general IFTA scheme is given with respect to quantization constraint strategies. Based on such a special classification, the three practically interesting approaches are chosen, further-analyzed, and compared to eachother. The performance of these algorithms is compared in detail in terms of the signal-to-noise ratio characteristic developments with respect to the numberof iterations, for various input diffusive-type objects chose. Also, the performance is documented on the complex spectra developments for typical computer reconstruction results. The advantages and drawbacks of all approaches are discussed, and a brief guide on the choice of a particular approach for typical design tasks is given. Finally, the two ways of amplitude elimination within the design procedure are considered, namely the direct elimination and partial elimination of the amplitude of the complex hologram function.
Limits to dose reduction from iterative reconstruction and the effect of through-slice blurring
NASA Astrophysics Data System (ADS)
Hsieh, Scott S.; Pelc, Norbert J.
2016-03-01
Iterative reconstruction methods have become very popular and show the potential to reduce dose. We present a limit to the maximum dose reduction possible with new reconstruction algorithms obtained by analyzing the information content of the raw data, assuming the reconstruction algorithm does not have a priori knowledge about the object or correlations between pixels. This limit applies to the task of estimating the density of a lesion embedded in a known background object, where the shape of the lesion is known but its density is not. Under these conditions, the density of the lesion can be estimated directly from the raw data in an optimal manner. This optimal estimate will meet or outperform the performance of any reconstruction method operating on the raw data, under the condition that the reconstruction method does not introduce a priori information. The raw data bound can be compared to the lesion density estimate from FBP in order to produce a limit on the dose reduction possible from new reconstruction algorithms. The possible dose reduction from iterative reconstruction varies with the object, but for a lesion embedded in the center of a water cylinder, it is less than 40%. Additionally, comparisons between iterative reconstruction and filtered backprojection are sometimes confounded by the effect of through-slice blurring in the iterative reconstruction. We analyzed the magnitude of the variance reduction brought about by through-slice blurring on scanners from two different vendors and found it to range between 11% and 48%.
Hesford, Andrew J.; Chew, Weng C.
2010-01-01
The distorted Born iterative method (DBIM) computes iterative solutions to nonlinear inverse scattering problems through successive linear approximations. By decomposing the scattered field into a superposition of scattering by an inhomogeneous background and by a material perturbation, large or high-contrast variations in medium properties can be imaged through iterations that are each subject to the distorted Born approximation. However, the need to repeatedly compute forward solutions still imposes a very heavy computational burden. To ameliorate this problem, the multilevel fast multipole algorithm (MLFMA) has been applied as a forward solver within the DBIM. The MLFMA computes forward solutions in linear time for volumetric scatterers. The typically regular distribution and shape of scattering elements in the inverse scattering problem allow the method to take advantage of data redundancy and reduce the computational demands of the normally expensive MLFMA setup. Additional benefits are gained by employing Kaczmarz-like iterations, where partial measurements are used to accelerate convergence. Numerical results demonstrate both the efficiency of the forward solver and the successful application of the inverse method to imaging problems with dimensions in the neighborhood of ten wavelengths. PMID:20707438
Weighted iterative reconstruction for magnetic particle imaging
NASA Astrophysics Data System (ADS)
Knopp, T.; Rahmer, J.; Sattel, T. F.; Biederer, S.; Weizenecker, J.; Gleich, B.; Borgert, J.; Buzug, T. M.
2010-03-01
Magnetic particle imaging (MPI) is a new imaging technique capable of imaging the distribution of superparamagnetic particles at high spatial and temporal resolution. For the reconstruction of the particle distribution, a system of linear equations has to be solved. The mathematical solution to this linear system can be obtained using a least-squares approach. In this paper, it is shown that the quality of the least-squares solution can be improved by incorporating a weighting matrix using the reciprocal of the matrix-row energy as weights. A further benefit of this weighting is that iterative algorithms, such as the conjugate gradient method, converge rapidly yielding the same image quality as obtained by singular value decomposition in only a few iterations. Thus, the weighting strategy in combination with the conjugate gradient method improves the image quality and substantially shortens the reconstruction time. The performance of weighting strategy and reconstruction algorithms is assessed with experimental data of a 2D MPI scanner.
The Cryostat and Subsystems Development at ITER
NASA Astrophysics Data System (ADS)
Sekachev, Igor; Meekins, Michael; Sborchia, Carlo; Vitupier, Guillaume; Xie, Han; Zhou, Caipin
ITER is a large experimental tokamak being built to research fusion power. The ITER cryostat is a multifunctional system which provides vacuum insulation for the superconducting magnets operating at 4.5 K and for the thermal shield operating at 80 K. It also serves as a structural support for the tokamak and provides access ways and corridors to the vacuum vessel for diagnostic lines of sight, additional heating beams and the deployment of remote handling equipment. The cryostat has feed-through penetrations for all the equipment connecting elements of systems outside the cryostat to the corresponding elements inside the cryostat. The cryostat is a vacuum containment vessel having a very large volume of ∼16000 m3 designed to be evacuated to a base pressure of 10-4 Pa. Design details of the cryostat and associated systems, including Torus Cryopump Housing (TCPH), are discussed. Status report of the cryostat developments is presented.
Main challenges for ITER optical diagnostics
Vukolov, K. Yu.; Orlovskiy, I. I.; Alekseev, A. G.; Borisov, A. A.; Andreenko, E. N.; Kukushkin, A. B.; Lisitsa, V. S.; Neverov, V. S.
2014-08-21
The review is made of the problems of ITER optical diagnostics. Most of these problems will be related to the intensive neutron radiation from hot plasma. At a high level of radiation loads the most types of materials gradually change their properties. This effect is most critical for optical diagnostics because of degradation of optical glasses and mirrors. The degradation of mirrors, that collect the light from plasma, basically will be induced by impurity deposition and (or) sputtering by charge exchange atoms. Main attention is paid to the search of glasses for vacuum windows and achromatic lens which are stable under ITER irradiation conditions. The last results of irradiation tests in nuclear reactor of candidate silica glasses KU-1, KS-4V and TF 200 are presented. An additional problem is discussed that deals with the stray light produced by multiple reflections from the first wall of the intense light emitted in the divertor plasma.
New iterative solvers for the NAG Libraries
Salvini, S.; Shaw, G.
1996-12-31
The purpose of this paper is to introduce the work which has been carried out at NAG Ltd to update the iterative solvers for sparse systems of linear equations, both symmetric and unsymmetric, in the NAG Fortran 77 Library. Our current plans to extend this work and include it in our other numerical libraries in our range are also briefly mentioned. We have added to the Library the new Chapter F11, entirely dedicated to sparse linear algebra. At Mark 17, the F11 Chapter includes sparse iterative solvers, preconditioners, utilities and black-box routines for sparse symmetric (both positive-definite and indefinite) linear systems. Mark 18 will add solvers, preconditioners, utilities and black-boxes for sparse unsymmetric systems: the development of these has already been completed.
Main challenges for ITER optical diagnostics
NASA Astrophysics Data System (ADS)
Vukolov, K. Yu.; Orlovskiy, I. I.; Alekseev, A. G.; Borisov, A. A.; Andreenko, E. N.; Kukushkin, A. B.; Lisitsa, V. S.; Neverov, V. S.
2014-08-01
The review is made of the problems of ITER optical diagnostics. Most of these problems will be related to the intensive neutron radiation from hot plasma. At a high level of radiation loads the most types of materials gradually change their properties. This effect is most critical for optical diagnostics because of degradation of optical glasses and mirrors. The degradation of mirrors, that collect the light from plasma, basically will be induced by impurity deposition and (or) sputtering by charge exchange atoms. Main attention is paid to the search of glasses for vacuum windows and achromatic lens which are stable under ITER irradiation conditions. The last results of irradiation tests in nuclear reactor of candidate silica glasses KU-1, KS-4V and TF 200 are presented. An additional problem is discussed that deals with the stray light produced by multiple reflections from the first wall of the intense light emitted in the divertor plasma.
High contrast laminography using iterative algorithms
NASA Astrophysics Data System (ADS)
Kroupa, M.; Jakubek, J.
2011-01-01
3D X-ray imaging of internal structure of large flat objects is often complicated by limited access to all viewing angles or extremely high absorption in certain directions, therefore the standard method of computed tomography (CT) fails. This problem can be solved by the method of laminography. During a laminographic measurement the imaging detector is placed close to the sample while the X-ray source irradiates both sample and detector at different angles. The application of the state-of-the-art pixel detector Medipix in laminography together with adapted tomographic iterative alghorithms for 3D reconstruction of sample structure has been investigated. Iterative algorithms such as EM (Expectation Maximization) and OSEM (Ordered Subset Expectation Maximization) improve the quality of the reconstruction and allow including more complex physical models. In this contribution results and proposed future approaches which could be used for resolution enhancement are presented.
Wideband digital spectrum analyzer
NASA Technical Reports Server (NTRS)
Morris, G. A., Jr.; Wilck, H. C.
1979-01-01
Modular spectrum analyzer consisting of RF receiver, fast fourier transform spectrum analyzer, and data processor samples stochastic signals in 220 channels. Construction reduces design and fabrication costs of assembled unit.
Autism Spectrum Disorder (ASD)
... spectrum disorder (ASD) is a group of developmental disabilities that can cause significant social, communication and behavioral ... for autism spectrum disorder (ASD) and other developmental disabilities. More E-mail Your Friends "Children with autism ...
Statistical properties of an iterated arithmetic mapping
Feix, M.R.; Rouet, J.L.
1994-07-01
We study the (3x = 1)/2 problem from a probabilistic viewpoint and show a forgetting mechanism for the last k binary digits of the seed after k iterations. The problem is subsequently generalized to a trifurcation process, the (lx + m)/3 problem. Finally the sequence of a set of seeds is empirically shown to be equivalent to a random walk of the variable log{sub 2}x (or log{sub 3} x) though computer simulations.
Iterative solutions to the Dirac equation
Ciftci, Hakan; Hall, Richard L.; Saad, Nasser
2005-08-15
We consider a single particle which is bound by a central potential and obeys the Dirac equation in d dimensions. We first apply the asymptotic iteration method to recover the known exact solutions for the pure Coulomb case. For a screened Coulomb potential and for a Coulomb plus linear potential with linear scalar confinement, the method is used to obtain accurate approximate solutions for both eigenvalues and wave functions.
Iterative solution of high order compact systems
Spotz, W.F.; Carey, G.F.
1996-12-31
We have recently developed a class of finite difference methods which provide higher accuracy and greater stability than standard central or upwind difference methods, but still reside on a compact patch of grid cells. In the present study we investigate the performance of several gradient-type iterative methods for solving the associated sparse systems. Both serial and parallel performance studies have been made. Representative examples are taken from elliptic PDE`s for diffusion, convection-diffusion, and viscous flow applications.
Iterates of a Berezin-type transform
NASA Astrophysics Data System (ADS)
Liu, Congwen
2007-05-01
Let be the open unit ball of and dV denote the Lebesgue measure on normalized so that the measure of equals 1. Suppose . The Berezin-type transform of f is defined by We prove that if then the iterates converge to the Poisson extension of the boundary values of f, as k-->[infinity]. This can be viewed as a higher dimensional generalization of a previous result obtained independently by Englis and Zhu.
Plasma shape experiments for an optimized tokamak
NASA Astrophysics Data System (ADS)
Hyatt, A. W.; Osborne, T. H.; Lazarus, E. A.
1994-07-01
In this paper we present results from recent experiments at DIII-D which measured the plasma stability and confinement performance product, beta(tau)(sub E), in one previously studied and three new plasma shapes. One important goal of these experiments was to identify performance vs. shape trends which would identify a shape compatible with both high performance and the planned effort to decrease the power flux to the divertor floor using a closed 'slot' divertor geometry. The closed divertor hardware must be designed for a reduced set of plasma shapes, so care must be taken to choose the shape that optimizes beta(tau)(sub E) and divertor performance. The four shapes studied form a matrix of moderate and high elongations (kappa congruent to 1.8 and 2.1) and low and high triangularities (delta congruent to 0.3 and 0.9). All configurations were double-null diverted (DND), held fixed during a shot, with neutral beam heating. The shapes span a range of X-point locations compatible with the envisioned closed divertor. We find that from shape to shape, a shot's transient normalized performance, beta(sub N)H, where beta(sub N) is equivalent to beta/(I(sup p)/aB(sub T)) and H is equivalent to tau(sub E)/tau(sub E)(sup ITER-89P), increases strongly with triangularity, but depends only weakly on elongation. However, the normalized performance during quasi stationary ELMing H-mode, to which these discharges eventually relax, is insensitive to both triangularity and elongation. The moderate elongation, high triangularity DND shape is shown to be near optimum for future studies on DIII-D.
Ice Shape Characterization Using Self-Organizing Maps
NASA Technical Reports Server (NTRS)
McClain, Stephen T.; Tino, Peter; Kreeger, Richard E.
2011-01-01
A method for characterizing ice shapes using a self-organizing map (SOM) technique is presented. Self-organizing maps are neural-network techniques for representing noisy, multi-dimensional data aligned along a lower-dimensional and possibly nonlinear manifold. For a large set of noisy data, each element of a finite set of codebook vectors is iteratively moved in the direction of the data closest to the winner codebook vector. Through successive iterations, the codebook vectors begin to align with the trends of the higher-dimensional data. In information processing, the intent of SOM methods is to transmit the codebook vectors, which contains far fewer elements and requires much less memory or bandwidth, than the original noisy data set. When applied to airfoil ice accretion shapes, the properties of the codebook vectors and the statistical nature of the SOM methods allows for a quantitative comparison of experimentally measured mean or average ice shapes to ice shapes predicted using computer codes such as LEWICE. The nature of the codebook vectors also enables grid generation and surface roughness descriptions for use with the discrete-element roughness approach. In the present study, SOM characterizations are applied to a rime ice shape, a glaze ice shape at an angle of attack, a bi-modal glaze ice shape, and a multi-horn glaze ice shape. Improvements and future explorations will be discussed.
Iterative pass optimization of sequence data
NASA Technical Reports Server (NTRS)
Wheeler, Ward C.
2003-01-01
The problem of determining the minimum-cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete. This "tree alignment" problem has motivated the considerable effort placed in multiple sequence alignment procedures. Wheeler in 1996 proposed a heuristic method, direct optimization, to calculate cladogram costs without the intervention of multiple sequence alignment. This method, though more efficient in time and more effective in cladogram length than many alignment-based procedures, greedily optimizes nodes based on descendent information only. In their proposal of an exact multiple alignment solution, Sankoff et al. in 1976 described a heuristic procedure--the iterative improvement method--to create alignments at internal nodes by solving a series of median problems. The combination of a three-sequence direct optimization with iterative improvement and a branch-length-based cladogram cost procedure, provides an algorithm that frequently results in superior (i.e., lower) cladogram costs. This iterative pass optimization is both computation and memory intensive, but economies can be made to reduce this burden. An example in arthropod systematics is discussed. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.
Iterative solution of the semiconductor device equations
Bova, S.W.; Carey, G.F.
1996-12-31
Most semiconductor device models can be described by a nonlinear Poisson equation for the electrostatic potential coupled to a system of convection-reaction-diffusion equations for the transport of charge and energy. These equations are typically solved in a decoupled fashion and e.g. Newton`s method is used to obtain the resulting sequences of linear systems. The Poisson problem leads to a symmetric, positive definite system which we solve iteratively using conjugate gradient. The transport equations lead to nonsymmetric, indefinite systems, thereby complicating the selection of an appropriate iterative method. Moreover, their solutions exhibit steep layers and are subject to numerical oscillations and instabilities if standard Galerkin-type discretization strategies are used. In the present study, we use an upwind finite element technique for the transport equations. We also evaluate the performance of different iterative methods for the transport equations and investigate various preconditioners for a few generalized gradient methods. Numerical examples are given for a representative two-dimensional depletion MOSFET.
Perturbation resilience and superiorization of iterative algorithms
NASA Astrophysics Data System (ADS)
Censor, Y.; Davidi, R.; Herman, G. T.
2010-06-01
Iterative algorithms aimed at solving some problems are discussed. For certain problems, such as finding a common point in the intersection of a finite number of convex sets, there often exist iterative algorithms that impose very little demand on computer resources. For other problems, such as finding that point in the intersection at which the value of a given function is optimal, algorithms tend to need more computer memory and longer execution time. A methodology is presented whose aim is to produce automatically for an iterative algorithm of the first kind a 'superiorized version' of it that retains its computational efficiency but nevertheless goes a long way toward solving an optimization problem. This is possible to do if the original algorithm is 'perturbation resilient', which is shown to be the case for various projection algorithms for solving the consistent convex feasibility problem. The superiorized versions of such algorithms use perturbations that steer the process in the direction of a superior feasible point, which is not necessarily optimal, with respect to the given function. After presenting these intuitive ideas in a precise mathematical form, they are illustrated in image reconstruction from projections for two different projection algorithms superiorized for the function whose value is the total variation of the image.
Recent ADI iteration analysis and results
Wachspress, E.L.
1994-12-31
Some recent ADI iteration analysis and results are discussed. Discovery that the Lyapunov and Sylvester matrix equations are model ADI problems stimulated much research on ADI iteration with complex spectra. The ADI rational Chebyshev analysis parallels the classical linear Chebyshev theory. Two distinct approaches have been applied to these problems. First, parameters which were optimal for real spectra were shown to be nearly optimal for certain families of complex spectra. In the linear case these were spectra bounded by ellipses in the complex plane. In the ADI rational case these were spectra bounded by {open_quotes}elliptic-function regions{close_quotes}. The logarithms of the latter appear like ellipses, and the logarithms of the optimal ADI parameters for these regions are similar to the optimal parameters for linear Chebyshev approximation over superimposed ellipses. W.B. Jordan`s bilinear transformation of real variables to reduce the two-variable problem to one variable was generalized into the complex plane. This was needed for ADI iterative solution of the Sylvester equation.
Modelling the ITER glow discharge plasma
NASA Astrophysics Data System (ADS)
Kogut, D.; Douai, D.; Hagelaar, G.; Pitts, R. A.
2015-08-01
The ITER glow discharge cleaning (GDC) system (Maruyama et al., 2012) is aimed to prepare in-vessel component surfaces prior to the machine start-up. In order to assess glow discharge uniformity and wall coverage, thus conditioning efficiency of the system, a new 2D multi-fluid model has been developed (Hagelaar, 2012). In this work the model is compared with published experimental data on GDC wall ion fluxes in JET and RFX (Douai et al., 2013; Canton et al., 2013). The simulations of H2-GDC in ITER for the case of 1 or 2 anodes indicate a good level of homogeneity of plasma parameters in the negative glow and of the wall ion flux in the common pressure domain for GDC: 0.1-0.5 Pa. Although the model geometry does not allow simulation of all seven ITER anodes operating simultaneously, the results can be extrapolated to the full system with an average ion current density of 0.21 A/m2, which is comparable to JET (0.10 A/m2).
ITER Creation Safety File Expertise Results
NASA Astrophysics Data System (ADS)
Perrault, D.
2013-06-01
In March 2010, the ITER operator delivered the facility safety file to the French "Autorité de Sûreté Nucléaire" (ASN) as part of its request for the creation decree, legally necessary before building works can begin on the site. The French "Institut de Radioprotection et de Sûreté Nucléaire" (IRSN), in support to the ASN, recently completed its expertise of the safety measures proposed for ITER, on the basis of this file and of additional technical documents from the operator. This paper presents the IRSN's main conclusions. In particular, they focus on the radioactive materials involved, the safety and radiation protection demonstration (suitability of risk management measures…), foreseeable accidents, building and safety important component design and, finally, wastes and effluents to be produced. This assessment was just the first legally-required step in on-going safety monitoring of the ITER project, which will include other complete regulatory re-evaluations.
The dynamics of iterated transportation simulations
Nagel, K.; Rickert, M.; Simon, P.M.
1998-12-01
Transportation-related decisions of people often depend on what everybody else is doing. For example, decisions about mode choice, route choice, activity scheduling, etc., can depend on congestion, caused by the aggregated behavior of others. From a conceptual viewpoint, this consistency problem causes a deadlock, since nobody can start planning because they do not know what everybody else is doing. It is the process of iterations that is examined in this paper as a method for solving the problem. In this paper, the authors concentrate on the aspect of the iterative process that is probably the most important one from a practical viewpoint, and that is the ``uniqueness`` or ``robustness`` of the results. Also, they define robustness more in terms of common sense than in terms of a mathematical formalism. For this, they do not only want a single iterative process to converge, but they want the result to be independent of any particular implementation. The authors run many computational experiments, sometimes with variations of the same code, sometimes with totally different code, in order to see if any of the results are robust against these changes.
Simplified Digital Spectrum Analyzer
NASA Technical Reports Server (NTRS)
Cole, Steven W.
1992-01-01
Spectrum analyzer computes approximate cross-correlations between noisy input signal and reference signal of known frequency, yielding measure of amplitude of sinusoidal component of input. Complexity and power consumed less than other digital spectrum analyzers. Performs no multiplications, and because processes data on each frequency independently, focuses on narrow spectral range without processing data on rest of spectrum.
2015-05-20
A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature
Shape prior modeling using sparse representation and online dictionary learning.
Zhang, Shaoting; Zhan, Yiqiang; Zhou, Yan; Uzunbas, Mustafa; Metaxas, Dimitris N
2012-01-01
The recently proposed sparse shape composition (SSC) opens a new avenue for shape prior modeling. Instead of assuming any parametric model of shape statistics, SSC incorporates shape priors on-the-fly by approximating a shape instance (usually derived from appearance cues) by a sparse combination of shapes in a training repository. Theoretically, one can increase the modeling capability of SSC by including as many training shapes in the repository. However, this strategy confronts two limitations in practice. First, since SSC involves an iterative sparse optimization at run-time, the more shape instances contained in the repository, the less run-time efficiency SSC has. Therefore, a compact and informative shape dictionary is preferred to a large shape repository. Second, in medical imaging applications, training shapes seldom come in one batch. It is very time consuming and sometimes infeasible to reconstruct the shape dictionary every time new training shapes appear. In this paper, we propose an online learning method to address these two limitations. Our method starts from constructing an initial shape dictionary using the K-SVD algorithm. When new training shapes come, instead of re-constructing the dictionary from the ground up, we update the existing one using a block-coordinates descent approach. Using the dynamically updated dictionary, sparse shape composition can be gracefully scaled up to model shape priors from a large number of training shapes without sacrificing run-time efficiency. Our method is validated on lung localization in X-Ray and cardiac segmentation in MRI time series. Compared to the original SSC, it shows comparable performance while being significantly more efficient. PMID:23286160
Iterative methods for symmetric ill-conditioned Toeplitz matrices
Huckle, T.
1996-12-31
We consider ill-conditioned symmetric positive definite, Toeplitz systems T{sub n}x = b. If we want to solve such a system iteratively with the conjugate gradient method, we can use band-Toeplitz-preconditioners or Sine-Transform-peconditioners M = S{sub n}{Lambda}S{sub n}, S{sub n} the Sine-Transform-matrix and {Lambda} a diagonal matrix. A Toeplitz matrix T{sub n} = (t{sub i-j)}{sub i}{sup n},{sub j=1} is often related to an underlying function f defined by the coefficients t{sub j}, j = -{infinity},..,-1,0, 1,.., {infinity}. There are four cases, for which we want to determine a preconditioner M: - T{sub n} is related to an underlying function which is given explicitly; - T{sub n} is related to an underlying function that is given by its Fourier coefficients; - T{sub n} is related to an underlying function that is unknown; - T{sub n} is not related to an underlying function. Especially for the first three cases we show how positive definite and effective preconditioners based on the Sine-Transform can be defined for general nonnegative underlying function f. To define M, we evaluate or estimate the values of f at certain positions, and build a Sine-transform matrix with these values as eigenvalues. Then, the spectrum of the preconditioned system is bounded from above and away from zero.
Current Control in ITER Steady State Plasmas With Neutral Beam Steering
R.V. Budny
2009-09-10
Predictions of quasi steady state DT plasmas in ITER are generated using the PTRANSP code. The plasma temperatures, densities, boundary shape, and total current (9 - 10 MA) anticipated for ITER steady state plasmas are specified. Current drive by negative ion neutral beam injection, lower-hybrid, and electron cyclotron resonance are calculated. Four modes of operation with different combinations of current drive are studied. For each mode, scans with the NNBI aimed at differing heights in the plasma are performed to study effects of current control on the q profile. The timeevolution of the currents and q are calculated to evaluate long duration transients. Quasi steady state, strongly reversed q profiles are predicted for some beam injection angles if the current drive and bootstrap currents are sufficiently large.
Guided Iterative Substructure Search (GI-SSS) - A New Trick for an Old Dog.
Weskamp, Nils
2016-07-01
Substructure search (SSS) is a fundamental technique supported by various chemical information systems. Many users apply it in an iterative manner: they modify their queries to shape the composition of the retrieved hit sets according to their needs. We propose and evaluate two heuristic extensions of SSS aimed at simplifying these iterative query modifications by collecting additional information during query processing and visualizing this information in an intuitive way. This gives the user a convenient feedback on how certain changes to the query would affect the retrieved hit set and reduces the number of trial-and-error cycles needed to generate an optimal search result. The proposed heuristics are simple, yet surprisingly effective and can be easily added to existing SSS implementations. PMID:27492243
Guided Iterative Substructure Search (GI-SSS) - A New Trick for an Old Dog.
Weskamp, Nils
2016-07-01
Substructure search (SSS) is a fundamental technique supported by various chemical information systems. Many users apply it in an iterative manner: they modify their queries to shape the composition of the retrieved hit sets according to their needs. We propose and evaluate two heuristic extensions of SSS aimed at simplifying these iterative query modifications by collecting additional information during query processing and visualizing this information in an intuitive way. This gives the user a convenient feedback on how certain changes to the query would affect the retrieved hit set and reduces the number of trial-and-error cycles needed to generate an optimal search result. The proposed heuristics are simple, yet surprisingly effective and can be easily added to existing SSS implementations.
Rajeev, K; Parameswaran, K
1998-07-20
Two iterative methods of inverting lidar backscatter signals to determine altitude profiles of aerosol extinction and altitude-resolved aerosol size distribution (ASD) are presented. The first method is for inverting two-wavelength lidar signals in which the shape of the ASD is assumed to be of power-law type, and the second method is for inverting multiwavelength lidar signals without assuming any a priori analytical form of ASD. An arbitrary value of the aerosol extinction-to-backscatter ratio (S(1)) is assumed initially to invert the lidar signals, and the ASD determined by use of the spectral dependence of the retrieved aerosol extinction coefficients is used to improve the value of S(1) iteratively. The methods are tested for different forms of altitude-dependent ASD's by use of simulated lidar-backscatter-signal profiles. The effect of random noise on the lidar backscatter signals is also studied.
Hutchinson incisors; Abnormal tooth shape; Peg teeth; Mulberry teeth; Conical teeth ... The appearance of normal teeth varies, especially the molars. ... conditions. Specific diseases can affect tooth shape, tooth ...
Carbon charge exchange analysis in the ITER-like wall environment
Menmuir, S.; Giroud, C.; Hawkes, N. C.; Biewer, T. M.; Coffey, I. H.; Delabie, E.; Sertoli, M.
2014-11-15
Charge exchange spectroscopy has long been a key diagnostic tool for fusion plasmas and is well developed in devices with Carbon Plasma-Facing Components. Operation with the ITER-like wall at JET has resulted in changes to the spectrum in the region of the Carbon charge exchange line at 529.06 nm and demonstrates the need to revise the core charge exchange analysis for this line. An investigation has been made of this spectral region in different plasma conditions and the revised description of the spectral lines to be included in the analysis is presented.
Carbon charge exchange analysis in the ITER-like wall environment.
Menmuir, S; Giroud, C; Biewer, T M; Coffey, I H; Delabie, E; Hawkes, N C; Sertoli, M
2014-11-01
Charge exchange spectroscopy has long been a key diagnostic tool for fusion plasmas and is well developed in devices with Carbon Plasma-Facing Components. Operation with the ITER-like wall at JET has resulted in changes to the spectrum in the region of the Carbon charge exchange line at 529.06 nm and demonstrates the need to revise the core charge exchange analysis for this line. An investigation has been made of this spectral region in different plasma conditions and the revised description of the spectral lines to be included in the analysis is presented.
NASA Astrophysics Data System (ADS)
Liu, Zi-Xin; Wen, Sheng-Hui; Li, Ming
2008-06-01
A combination of the iterative perturbation theory (ITP) of the dynamical mean field theory (DMFT) and coherent-potential approximation (CPA) is generalized to the double exchange model with orbital degeneracy. The Hubbard interaction and the off-diagonal components for the hopping matrix tmnij(m ≠ n) are considered in our calculation of spectrum and optical conductivity. The numerical results show that the effects of the non-diagonal hopping matrix elements are important.
Static shape of an acoustically levitated drop with wave-drop interaction
NASA Astrophysics Data System (ADS)
Lee, C. P.; Anilkumar, A. V.; Wang, T. G.
1994-11-01
The static shape of a drop levitated and flattened by an acoustic standing wave field in air is calculated, requiring self-consistency between the drop shape and the wave. The wave is calculated for a given shape using the boundary integral method. From the resulting radiation stress on the drop surface, the shape is determined by solving the Young-Laplace equation, completing an iteration cycle. The iteration is continued until both the shape and the wave converge. Of particular interest are the shapes of large drops that sustain equilibrium, beyond a certain degree of flattening, by becoming more flattened at a decreasing sound pressure level. The predictions for flattening versus acoustic radiation stress, for drops of different sizes, compare favorably with experimental data.
Research on JET in view of ITER
NASA Astrophysics Data System (ADS)
Pamela, Jerome; Ongena, Jef; Watkins, Michael
2004-11-01
Research on JET is focused on further development of the two ITER reference plasma scenarios. The ELMy H-Mode, has been extended to lower rho* at high and q_95=3, with simultaneously H_98=0.9, and f_GW=0.9 at I_p=3.5 MA. The dependence of confinement on beta and rho* has been found to be more favorable than given by the IPB98(y,2) scaling. Highlights in the development of Advanced Regimes with Internal Transport Barriers (ITB) and strong reversed shear (q_0=2-3, q_min=1.5-2.5) are : (i) operation at a core density close to the Greenwald limit and (ii) full current drive in 3T/1.8MA ITB plasmas extended to 20 seconds with a JET record injected energy of E≈ 330MJ; (iii) 7 keV Te≈ Ti ITB plasmas at low toroidal rotation, and (iv) wide radius ITB's (r/a=0.6). Furthermore, emphasis in JET is placed on (i) mitigating the impact of ELMs, (ii) understanding the phenomena leading to tritium retention and (iii) preparing burning plasma physics. Recent developments on JET in view of ITER are : (i) real-time control in both ELMy H-Mode and ITB plasmas and (ii) an upgrade of JET with: (a) increased NBI power (b) a new ELM-resilient ITER-like ICRH antenna (7MW) to be tested in 2006 (c) 16 new and upgraded diagnostics.
Corneal topography matching by iterative registration.
Wang, Junjie; Elsheikh, Ahmed; Davey, Pinakin G; Wang, Weizhuo; Bao, Fangjun; Mottershead, John E
2014-11-01
Videokeratography is used for the measurement of corneal topography in overlapping portions (or maps) which must later be joined together to form the overall topography of the cornea. The separate portions are measured from different viewpoints and therefore must be brought together by registration of measurement points in the regions of overlap. The central map is generally the most accurate, but all maps are measured with uncertainty that increases towards the periphery. It becomes the reference (or static) map, and the peripheral (or dynamic) maps must then be transformed by rotation and translation so that the overlapping portions are matched. The process known as registration, of determining the necessary transformation, is a well-understood procedure in image analysis and has been applied in several areas of science and engineering. In this article, direct search optimisation using the Nelder-Mead algorithm and several variants of the iterative closest/corresponding point routine are explained and applied to simulated and real clinical data. The measurement points on the static and dynamic maps are generally different so that it becomes necessary to interpolate, which is done using a truncated series of Zernike polynomials. The point-to-plane iterative closest/corresponding point variant has the advantage of releasing certain optimisation constraints that lead to persistent registration and alignment errors when other approaches are used. The point-to-plane iterative closest/corresponding point routine is found to be robust to measurement noise, insensitive to starting values of the transformation parameters and produces high-quality results when using real clinical data.
Shapes of sedimenting soft elastic capsules in a viscous fluid.
Boltz, Horst-Holger; Kierfeld, Jan
2015-09-01
Soft elastic capsules which are driven through a viscous fluid undergo shape deformation coupled to their motion. We introduce an iterative solution scheme which couples hydrodynamic boundary integral methods and elastic shape equations to find the stationary axisymmetric shape and the velocity of an elastic capsule moving in a viscous fluid at low Reynolds numbers. We use this approach to systematically study dynamical shape transitions of capsules with Hookean stretching and bending energies and spherical rest shape sedimenting under the influence of gravity or centrifugal forces. We find three types of possible axisymmetric stationary shapes for sedimenting capsules with fixed volume: a pseudospherical state, a pear-shaped state, and buckled shapes. Capsule shapes are controlled by two dimensionless parameters, the Föppl-von-Kármán number characterizing the elastic properties and a Bond number characterizing the driving force. For increasing gravitational force the spherical shape transforms into a pear shape. For very large bending rigidity (very small Föppl-von-Kármán number) this transition is discontinuous with shape hysteresis. The corresponding transition line terminates, however, in a critical point, such that the discontinuous transition is not present at typical Föppl-von-Kármán numbers of synthetic capsules. In an additional bifurcation, buckled shapes occur upon increasing the gravitational force. This type of instability should be observable for generic synthetic capsules. All shape bifurcations can be resolved in the force-velocity relation of sedimenting capsules, where up to three capsule shapes with different velocities can occur for the same driving force. All three types of possible axisymmetric stationary shapes are stable with respect to rotation during sedimentation. Additionally, we study capsules pushed or pulled by a point force, where we always find capsule shapes to transform smoothly without bifurcations. PMID:26465552
Shapes of sedimenting soft elastic capsules in a viscous fluid
NASA Astrophysics Data System (ADS)
Boltz, Horst-Holger; Kierfeld, Jan
2015-09-01
Soft elastic capsules which are driven through a viscous fluid undergo shape deformation coupled to their motion. We introduce an iterative solution scheme which couples hydrodynamic boundary integral methods and elastic shape equations to find the stationary axisymmetric shape and the velocity of an elastic capsule moving in a viscous fluid at low Reynolds numbers. We use this approach to systematically study dynamical shape transitions of capsules with Hookean stretching and bending energies and spherical rest shape sedimenting under the influence of gravity or centrifugal forces. We find three types of possible axisymmetric stationary shapes for sedimenting capsules with fixed volume: a pseudospherical state, a pear-shaped state, and buckled shapes. Capsule shapes are controlled by two dimensionless parameters, the Föppl-von-Kármán number characterizing the elastic properties and a Bond number characterizing the driving force. For increasing gravitational force the spherical shape transforms into a pear shape. For very large bending rigidity (very small Föppl-von-Kármán number) this transition is discontinuous with shape hysteresis. The corresponding transition line terminates, however, in a critical point, such that the discontinuous transition is not present at typical Föppl-von-Kármán numbers of synthetic capsules. In an additional bifurcation, buckled shapes occur upon increasing the gravitational force. This type of instability should be observable for generic synthetic capsules. All shape bifurcations can be resolved in the force-velocity relation of sedimenting capsules, where up to three capsule shapes with different velocities can occur for the same driving force. All three types of possible axisymmetric stationary shapes are stable with respect to rotation during sedimentation. Additionally, we study capsules pushed or pulled by a point force, where we always find capsule shapes to transform smoothly without bifurcations.
Shapes of sedimenting soft elastic capsules in a viscous fluid.
Boltz, Horst-Holger; Kierfeld, Jan
2015-09-01
Soft elastic capsules which are driven through a viscous fluid undergo shape deformation coupled to their motion. We introduce an iterative solution scheme which couples hydrodynamic boundary integral methods and elastic shape equations to find the stationary axisymmetric shape and the velocity of an elastic capsule moving in a viscous fluid at low Reynolds numbers. We use this approach to systematically study dynamical shape transitions of capsules with Hookean stretching and bending energies and spherical rest shape sedimenting under the influence of gravity or centrifugal forces. We find three types of possible axisymmetric stationary shapes for sedimenting capsules with fixed volume: a pseudospherical state, a pear-shaped state, and buckled shapes. Capsule shapes are controlled by two dimensionless parameters, the Föppl-von-Kármán number characterizing the elastic properties and a Bond number characterizing the driving force. For increasing gravitational force the spherical shape transforms into a pear shape. For very large bending rigidity (very small Föppl-von-Kármán number) this transition is discontinuous with shape hysteresis. The corresponding transition line terminates, however, in a critical point, such that the discontinuous transition is not present at typical Föppl-von-Kármán numbers of synthetic capsules. In an additional bifurcation, buckled shapes occur upon increasing the gravitational force. This type of instability should be observable for generic synthetic capsules. All shape bifurcations can be resolved in the force-velocity relation of sedimenting capsules, where up to three capsule shapes with different velocities can occur for the same driving force. All three types of possible axisymmetric stationary shapes are stable with respect to rotation during sedimentation. Additionally, we study capsules pushed or pulled by a point force, where we always find capsule shapes to transform smoothly without bifurcations.
Iterative repair for scheduling and rescheduling
NASA Technical Reports Server (NTRS)
Zweben, Monte; Davis, Eugene; Deale, Michael
1991-01-01
An iterative repair search method is described called constraint based simulated annealing. Simulated annealing is a hill climbing search technique capable of escaping local minima. The utility of the constraint based framework is shown by comparing search performance with and without the constraint framework on a suite of randomly generated problems. Results are also shown of applying the technique to the NASA Space Shuttle ground processing problem. These experiments show that the search methods scales to complex, real world problems and reflects interesting anytime behavior.
Iterative phase retrieval strategy of transient events.
Ng, Tuck Wah; Chua, Adrian Sau Ling
2012-01-20
Important nuances of a process or processes in action can be obtained from the phase retrieval of diffraction patterns for analysis of transient events. A significant limitation associated with the iterative approach is that predictive input functions are needed and can result in situations of nonconvergence. In dealing with a transient event recorded as a series of Fourier magnitude patterns, such a hit-and-miss characteristic, on the surface, appears computationally daunting. We report and demonstrate a strategy here that effectively minimizes this by using a prior retrieved frame as the predictive function for the current retrieval process. PMID:22270666
Design of the ITER ICRF Antenna
NASA Astrophysics Data System (ADS)
Hancock, D.; Nightingale, M.; Bamber, R.; Dalton, N.; Durodie, F.; Firdaouss, M.; Lister, J.; Porton, M.; Shannon, M.; Wilson, D.; Winkler, K.; Wooldridge, E.
2011-12-01
The CYCLE consortium has been designing the ITER ICRF antenna since March 2010, supported by an F4E grant. Following a brief introduction to the consortium, this paper: describes the present status and layout of the design; highlights the key mechanical engineering features; shows the expected impact of cooling and radiation issues on the design and outlines the need for future R&D to support the design process. A key design requirement is the need for the mechanical design and analysis to be consistent with all requirements following from the RF physics and antenna layout optimisation. As such, this paper complements that of Durodie et al [1].
Adaptable Iterative and Recursive Kalman Filter Schemes
NASA Technical Reports Server (NTRS)
Zanetti, Renato
2014-01-01
Nonlinear filters are often very computationally expensive and usually not suitable for real-time applications. Real-time navigation algorithms are typically based on linear estimators, such as the extended Kalman filter (EKF) and, to a much lesser extent, the unscented Kalman filter. The Iterated Kalman filter (IKF) and the Recursive Update Filter (RUF) are two algorithms that reduce the consequences of the linearization assumption of the EKF by performing N updates for each new measurement, where N is the number of recursions, a tuning parameter. This paper introduces an adaptable RUF algorithm to calculate N on the go, a similar technique can be used for the IKF as well.
Accelerating Spectrum Sharing Technologies
Juan D. Deaton; Lynda L. Brighton; Rangam Subramanian; Hussein Moradi; Jose Loera
2013-09-01
Spectrum sharing potentially holds the promise of solving the emerging spectrum crisis. However, technology innovators face the conundrum of developing spectrum sharing technologies without the ability to experiment and test with real incumbent systems. Interference with operational incumbents can prevent critical services, and the cost of deploying and operating an incumbent system can be prohibitive. Thus, the lack of incumbent systems and frequency authorization for technology incubation and demonstration has stymied spectrum sharing research. To this end, industry, academia, and regulators all require a test facility for validating hypotheses and demonstrating functionality without affecting operational incumbent systems. This article proposes a four-phase program supported by our spectrum accountability architecture. We propose that our comprehensive experimentation and testing approach for technology incubation and demonstration will accelerate the development of spectrum sharing technologies.
In situ monitoring hydrogen isotope retention in ITER first wall
NASA Astrophysics Data System (ADS)
Mukhin, E. E.; Andrew, P.; Anthoine, A. D.; Bazhenov, A. N.; Barnsley, R.; Bukreev, I. M.; Bukhovets, V. L.; Chernakov, A. P.; Gorodetsky, A. E.; Kochergin, M. M.; Koval, A. N.; Kukushkin, A. B.; Kukushkin, A. S.; Kurskiev, G. S.; Levashova, M. G.; Litvinov, A. E.; Litunovsky, V. N.; Markin, A. V.; Mazul, I. V.; Masyukevich, S. V.; Miroshnikov, I. V.; Nemov, A. S.; Novokhatsky, A. N.; Razdobarin, A. G.; Sherstnev, E. V.; Samsonov, D. S.; Semenov, V. V.; Smirnov, A. S.; De Temmerman, G.; Tolstyakov, S. Yu.; Zalavutdinov, R. Kh.; Walsh, M. J.
2016-03-01
Tritium retention inside the vacuum vessel is a potentially serious constraint in the operation of large-scale fusion machines like ITER. An in situ diagnostics for first wall H/D/T retention by laser induced desorption spectroscopy (LIDS) is proposed for use between plasma discharges. The technique is based on local baking of the first wall by laser irradiation and subsequent analysis of the in-vessel gas by optical emission spectroscopy of plasma radiation. The local heating implementation, kinetics of H/D/T thermal extraction and the accuracy of optical emission spectroscopy measurements are analysed. To resolve the H/D/T lines spectroscopically, their thermal broadening should be minimized to prevent overlapping of the line shapes. A comparative performance analysis of several types of plasma sources with relatively cold ions is made including the following types of discharges: Penning, RF multipactor, laser torch and ECR. All these radiation sources require rather low power and could be used for remote in situ measurements of relative densities of the thermally extracted hydrogen isotopes.
3D modeling and optimization of the ITER ICRH antenna
NASA Astrophysics Data System (ADS)
Louche, F.; Dumortier, P.; Durodié, F.; Messiaen, A.; Maggiora, R.; Milanesio, D.
2011-12-01
The prediction of the coupling properties of the ITER ICRH antenna necessitates the accurate evaluation of the resistance and reactance matrices. The latter are mostly dependent on the geometry of the array and therefore a model as accurate as possible is needed to precisely compute these matrices. Furthermore simulations have so far neglected the poloidal and toroidal profile of the plasma, and it is expected that the loading by individual straps will vary significantly due to varying strap-plasma distance. To take this curvature into account, some modifications of the alignment of the straps with respect to the toroidal direction are proposed. It is shown with CST Microwave Studio® [1] that considering two segments in the toroidal direction, i.e. a "V-shaped" toroidal antenna, is sufficient. A new CATIA model including this segmentation has been drawn and imported into both MWS and TOPICA [2] codes. Simulations show a good agreement of the impedance matrices in vacuum. Various modifications of the geometry are proposed in order to further optimize the coupling. In particular we study the effect of the strap box parameters and the recess of the vertical septa.
Quantum Spread Spectrum Communication
Humble, Travis S
2011-01-01
We show that communication of single-photon quantum states in a multi-user environment is improved by using spread spectrum communication techniques. We describe a framework for spreading, transmitting, despreading, and detecting single-photon spectral states that mimics conventional spread spectrum techniques. We show in the cases of inadvertent detection, unintentional interference, and multi-user management, that quantum spread spectrum communications may minimize receiver errors by managing quantum channel access.
Wilson, Thomas S.; Bearinger, Jane P.
2015-06-09
New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.
Autism; Autistic disorder; Asperger syndrome; Childhood disintegrative disorder; Pervasive developmental disorder ... to better diagnosis and newer definitions of ASD. Autism spectrum disorder now includes syndromes that used to ...
Ionospheric wave spectrum measurements
NASA Technical Reports Server (NTRS)
Harker, K. J.; Ilic, D. B.; Crawford, F. W.
1979-01-01
The local spectrum S(k, omega) of either potential or electron-density fluctuations can be used to determine macroscopic-plasma characteristics such as the local density and temperature, transport coefficients, and drift current. This local spectrum can be determined by measuring the cross-power spectrum. The paper examines the practicality of using the cross-power spectrum analyzer on the Space Shuttle to measure ionospheric parameters. Particular attention is given to investigating the integration time required to measure the cross-power spectral density to a desired accuracy.
Adaptive self-calibrating iterative GRAPPA reconstruction.
Park, Suhyung; Park, Jaeseok
2012-06-01
Parallel magnetic resonance imaging in k-space such as generalized auto-calibrating partially parallel acquisition exploits spatial correlation among neighboring signals over multiple coils in calibration to estimate missing signals in reconstruction. It is often challenging to achieve accurate calibration information due to data corruption with noises and spatially varying correlation. The purpose of this work is to address these problems simultaneously by developing a new, adaptive iterative generalized auto-calibrating partially parallel acquisition with dynamic self-calibration. With increasing iterations, under a framework of the Kalman filter spatial correlation is estimated dynamically updating calibration signals in a measurement model and using fixed-point state transition in a process model while missing signals outside the step-varying calibration region are reconstructed, leading to adaptive self-calibration and reconstruction. Noise statistic is incorporated in the Kalman filter models, yielding coil-weighted de-noising in reconstruction. Numerical and in vivo studies are performed, demonstrating that the proposed method yields highly accurate calibration and thus reduces artifacts and noises even at high acceleration. PMID:21994010
Diverse Power Iteration Embeddings and Its Applications
Huang H.; Yoo S.; Yu, D.; Qin, H.
2014-12-14
Abstract—Spectral Embedding is one of the most effective dimension reduction algorithms in data mining. However, its computation complexity has to be mitigated in order to apply it for real-world large scale data analysis. Many researches have been focusing on developing approximate spectral embeddings which are more efficient, but meanwhile far less effective. This paper proposes Diverse Power Iteration Embeddings (DPIE), which not only retains the similar efficiency of power iteration methods but also produces a series of diverse and more effective embedding vectors. We test this novel method by applying it to various data mining applications (e.g. clustering, anomaly detection and feature selection) and evaluating their performance improvements. The experimental results show our proposed DPIE is more effective than popular spectral approximation methods, and obtains the similar quality of classic spectral embedding derived from eigen-decompositions. Moreover it is extremely fast on big data applications. For example in terms of clustering result, DPIE achieves as good as 95% of classic spectral clustering on the complex datasets but 4000+ times faster in limited memory environment.
Iterative Gaussianization: from ICA to random rotations.
Laparra, Valero; Camps-Valls, Gustavo; Malo, Jesús
2011-04-01
Most signal processing problems involve the challenging task of multidimensional probability density function (PDF) estimation. In this paper, we propose a solution to this problem by using a family of rotation-based iterative Gaussianization (RBIG) transforms. The general framework consists of the sequential application of a univariate marginal Gaussianization transform followed by an orthonormal transform. The proposed procedure looks for differentiable transforms to a known PDF so that the unknown PDF can be estimated at any point of the original domain. In particular, we aim at a zero-mean unit-covariance Gaussian for convenience. RBIG is formally similar to classical iterative projection pursuit algorithms. However, we show that, unlike in PP methods, the particular class of rotations used has no special qualitative relevance in this context, since looking for interestingness is not a critical issue for PDF estimation. The key difference is that our approach focuses on the univariate part (marginal Gaussianization) of the problem rather than on the multivariate part (rotation). This difference implies that one may select the most convenient rotation suited to each practical application. The differentiability, invertibility, and convergence of RBIG are theoretically and experimentally analyzed. Relation to other methods, such as radial Gaussianization, one-class support vector domain description, and deep neural networks is also pointed out. The practical performance of RBIG is successfully illustrated in a number of multidimensional problems such as image synthesis, classification, denoising, and multi-information estimation. PMID:21349790
Laser cleaning of ITER's diagnostic mirrors
NASA Astrophysics Data System (ADS)
Skinner, C. H.; Gentile, C. A.; Doerner, R.
2012-10-01
Practical methods to clean ITER's diagnostic mirrors and restore reflectivity will be critical to ITER's plasma operations. We report on laser cleaning of single crystal molybdenum mirrors coated with either carbon or beryllium films 150 - 420 nm thick. A 1.06 μm Nd laser system provided 220 ns pulses at 8 kHz with typical power densities of 1-2 J/cm^2. The laser beam was fiber optically coupled to a scanner suitable for tokamak applications. The efficacy of mirror cleaning was assessed with a new technique that combines microscopic imaging and reflectivity measurements [1]. The method is suitable for hazardous materials such as beryllium as the mirrors remain sealed in a vacuum chamber. Excellent restoration of reflectivity for the carbon coated Mo mirrors was observed after laser scanning under vacuum conditions. For the beryllium coated mirrors restoration of reflectivity has so far been incomplete and modeling indicates that a shorter duration laser pulse is needed. No damage of the molybdenum mirror substrates was observed.[4pt][1] C.H. Skinner et al., Rev. Sci. Instrum. at press.
Ordinal neural networks without iterative tuning.
Fernández-Navarro, Francisco; Riccardi, Annalisa; Carloni, Sante
2014-11-01
Ordinal regression (OR) is an important branch of supervised learning in between the multiclass classification and regression. In this paper, the traditional classification scheme of neural network is adapted to learn ordinal ranks. The model proposed imposes monotonicity constraints on the weights connecting the hidden layer with the output layer. To do so, the weights are transcribed using padding variables. This reformulation leads to the so-called inequality constrained least squares (ICLS) problem. Its numerical solution can be obtained by several iterative methods, for example, trust region or line search algorithms. In this proposal, the optimum is determined analytically according to the closed-form solution of the ICLS problem estimated from the Karush-Kuhn-Tucker conditions. Furthermore, following the guidelines of the extreme learning machine framework, the weights connecting the input and the hidden layers are randomly generated, so the final model estimates all its parameters without iterative tuning. The model proposed achieves competitive performance compared with the state-of-the-art neural networks methods for OR. PMID:25330430
Iterative CBCT reconstruction using Hessian penalty
NASA Astrophysics Data System (ADS)
Sun, Tao; Sun, Nanbo; Wang, Jing; Tan, Shan
2015-03-01
Statistical iterative reconstruction algorithms have shown potential to improve cone-beam CT (CBCT) image quality. Most iterative reconstruction algorithms utilize prior knowledge as a penalty term in the objective function. The penalty term greatly affects the performance of a reconstruction algorithm. The total variation (TV) penalty has demonstrated great ability in suppressing noise and improving image quality. However, calculated from the first-order derivatives, the TV penalty leads to the well-known staircase effect, which sometimes makes the reconstructed images oversharpen and unnatural. In this study, we proposed to use a second-order derivative penalty that involves the Frobenius norm of the Hessian matrix of an image for CBCT reconstruction. The second-order penalty retains some of the most favorable properties of the TV penalty like convexity, homogeneity, and rotation and translation invariance, and has a better ability in preserving the structures of gradual transition in the reconstructed images. An effective algorithm was developed to minimize the objective function with the majorization-minimization (MM) approach. The experiments on a digital phantom and two physical phantoms demonstrated the priority of the proposed penalty, particularly in suppressing the staircase effect of the TV penalty.
Thomson scattering diagnostic systems in ITER
NASA Astrophysics Data System (ADS)
Bassan, M.; Andrew, P.; Kurskiev, G.; Mukhin, E.; Hatae, T.; Vayakis, G.; Yatsuka, E.; Walsh, M.
2016-01-01
Thomson scattering (TS) is a proven diagnostic technique that will be implemented in ITER in three independent systems. The Edge TS will measure electron temperature Te and electron density ne profiles at high resolution in the region with r/a>0.8 (with a the minor radius). The Core TS will cover the region r/a<0.85 and shall be able to measure electron temperatures up to 40 keV . The Divertor TS will observe a segment of the divertor plasma more than 700 mm long and is designed to detect Te as low as 0.3 eV . The Edge and Core systems are primary contributors to Te and ne profiles. Both are installed in equatorial port 10 and very close together with the toroidal distance between the two laser beams of less than 600 mm at the first wall (~ 6° toroidal separation), a characteristic that should allow to reliably match the two profiles in the region 0.8
Adaptive self-calibrating iterative GRAPPA reconstruction.
Park, Suhyung; Park, Jaeseok
2012-06-01
Parallel magnetic resonance imaging in k-space such as generalized auto-calibrating partially parallel acquisition exploits spatial correlation among neighboring signals over multiple coils in calibration to estimate missing signals in reconstruction. It is often challenging to achieve accurate calibration information due to data corruption with noises and spatially varying correlation. The purpose of this work is to address these problems simultaneously by developing a new, adaptive iterative generalized auto-calibrating partially parallel acquisition with dynamic self-calibration. With increasing iterations, under a framework of the Kalman filter spatial correlation is estimated dynamically updating calibration signals in a measurement model and using fixed-point state transition in a process model while missing signals outside the step-varying calibration region are reconstructed, leading to adaptive self-calibration and reconstruction. Noise statistic is incorporated in the Kalman filter models, yielding coil-weighted de-noising in reconstruction. Numerical and in vivo studies are performed, demonstrating that the proposed method yields highly accurate calibration and thus reduces artifacts and noises even at high acceleration.
Iterative image reconstruction in spectral CT
NASA Astrophysics Data System (ADS)
Hernandez, Daniel; Michel, Eric; Kim, Hye S.; Kim, Jae G.; Han, Byung H.; Cho, Min H.; Lee, Soo Y.
2012-03-01
Scan time of spectral-CTs is much longer than conventional CTs due to limited number of x-ray photons detectable by photon-counting detectors. However, the spectral pixel information in spectral-CT has much richer information on physiological and pathological status of the tissues than the CT-number in conventional CT, which makes the spectral- CT one of the promising future imaging modalities. One simple way to reduce the scan time in spectral-CT imaging is to reduce the number of views in the acquisition of projection data. But, this may result in poorer SNR and strong streak artifacts which can severely compromise the image quality. In this work, spectral-CT projection data were obtained from a lab-built spectral-CT consisting of a single CdTe photon counting detector, a micro-focus x-ray tube and scan mechanics. For the image reconstruction, we used two iterative image reconstruction methods, the simultaneous iterative reconstruction technique (SIRT) and the total variation minimization based on conjugate gradient method (CG-TV), along with the filtered back-projection (FBP) to compare the image quality. From the imaging of the iodine containing phantoms, we have observed that SIRT and CG-TV are superior to the FBP method in terms of SNR and streak artifacts.
Critical Assessment of Pressure Gauges for ITER
Tabares, Francisco L.; Tafalla, David; Garcia-Cortes, Isabel
2008-03-12
The density and flux of molecular species in ITER, largely dominated by the molecular form of the main plasma components and the He ash, is a valuable parameter of relevance not only for operation purposes but also for validating existing neutral particle models of direct implications in divertor performance. An accurate and spatially resolved monitoring of this parameter implies the proper selection of pressure gauges able to cope with the very unique and aggressive environment to be expected in a fusion reactor. To date, there is no standard gauge fulfilling all the requirements, which encompass high neutron and gamma fluxes, together with strong magnetic field and temperature excursions and dusty environment. In the present work, a review of the challenges to face in the measurement of neutral pressure in ITER, together with existing technologies and developments to be made in some of them for their application to the task is presented. Particular attention is paid to R and D needs of existing concepts with potential use in future designs.
NASA Astrophysics Data System (ADS)
Resita Arum, Sari; A, Suparmi; C, Cari
2016-01-01
The Dirac equation for Eckart potential and trigonometric Manning Rosen potential with exact spin symmetry is obtained using an asymptotic iteration method. The combination of the two potentials is substituted into the Dirac equation, then the variables are separated into radial and angular parts. The Dirac equation is solved by using an asymptotic iteration method that can reduce the second order differential equation into a differential equation with substitution variables of hypergeometry type. The relativistic energy is calculated using Matlab 2011. This study is limited to the case of spin symmetry. With the asymptotic iteration method, the energy spectra of the relativistic equations and equations of orbital quantum number l can be obtained, where both are interrelated between quantum numbers. The energy spectrum is also numerically solved using the Matlab software, where the increase in the radial quantum number nr causes the energy to decrease. The radial part and the angular part of the wave function are defined as hypergeometry functions and visualized with Matlab 2011. The results show that the disturbance of a combination of the Eckart potential and trigonometric Manning Rosen potential can change the radial part and the angular part of the wave function. Project supported by the Higher Education Project (Grant No. 698/UN27.11/PN/2015).
The role of heating and current drive in ITER
Nevins, W.M.; Haney, S.
1993-10-18
This report discusses and summarize the role of heating and non-inductive current drive in ITER as: (1) ITER must have heating power sufficient for ignition. (2) The heating system must be capable of current drive. (3) Steady-state operation is an ``ultimate goal.`` It is recognized that additional heating and current drive power (beyond what is initially installed on ITER) may be required. (4) The ``Ultimate goal of steady-state operation`` means steady-state with Q{sub CD} {ge} 5. Unlike the ``Terms of Reference`` for the ITER CDA, the ``ITER Technical Objectives and Approaches`` for the EDA sets no goal for the neutron wall load during steady-state operation. (5) In addition to bulk current drive, the ITER heating and current drive system should be used for current profile control and for burn control.
A unified noise analysis for iterative image estimation
Qi, Jinyi
2003-07-03
Iterative image estimation methods have been widely used in emission tomography. Accurate estimate of the uncertainty of the reconstructed images is essential for quantitative applications. While theoretical approach has been developed to analyze the noise propagation from iteration to iteration, the current results are limited to only a few iterative algorithms that have an explicit multiplicative update equation. This paper presents a theoretical noise analysis that is applicable to a wide range of preconditioned gradient type algorithms. One advantage is that proposed method does not require an explicit expression of the preconditioner and hence it is applicable to some algorithms that involve line searches. By deriving fixed point expression from the iteration based results, we show that the iteration based noise analysis is consistent with the xed point based analysis. Examples in emission tomography and transmission tomography are shown.
Majorana approach to the stochastic theory of line shapes
NASA Astrophysics Data System (ADS)
Komijani, Yashar; Coleman, Piers
2016-08-01
Motivated by recent Mössbauer experiments on strongly correlated mixed-valence systems, we revisit the Kubo-Anderson stochastic theory of spectral line shapes. Using a Majorana representation for the nuclear spin we demonstrate how to recast the classic line-shape theory in a field-theoretic and diagrammatic language. We show that the leading contribution to the self-energy can reproduce most of the observed line-shape features including splitting and line-shape narrowing, while the vertex and the self-consistency corrections can be systematically included in the calculation. This approach permits us to predict the line shape produced by an arbitrary bulk charge fluctuation spectrum providing a model-independent way to extract the local charge fluctuation spectrum of the surrounding medium. We also derive an inverse formula to extract the charge fluctuation from the measured line shape.
Extending the physics basis of quiescent H-mode toward ITER relevant parameters
Solomon, W. M.; Burrell, K. H.; Fenstermacher, M. E.; Garofalo, A. M.; Grierson, B. A.; Loarte, A.; McKee, G. R.; Nazikian, R.; Osborne, T. H.; Snyder, P. B.
2015-06-26
Recent experiments on DIII-D have addressed several long-standing issues needed to establish quiescent H-mode (QH-mode) as a viable operating scenario for ITER. In the past, QH-mode was associated with low density operation, but has now been extended to high normalized densities compatible with operation envisioned for ITER. Through the use of strong shaping, QH-mode plasmas have been maintained at high densities, both absolute ($\\bar{n}$_{e} ≈ 7 × 10^{19} m^{₋3}) and normalized Greenwald fraction ($\\bar{n}$_{e}/n_{G} > 0.7). In these plasmas, the pedestal can evolve to very high pressure and edge current as the density is increased. High density QH-mode operation with strong shaping has allowed access to a previously predicted regime of very high pedestal dubbed “Super H-mode”. Calculations of the pedestal height and width from the EPED model are quantitatively consistent with the experimentally observed density evolution. The confirmation of the shape dependence of the maximum density threshold for QH-mode helps validate the underlying theoretical model of peeling- ballooning modes for ELM stability. In general, QH-mode is found to achieve ELM- stable operation while maintaining adequate impurity exhaust, due to the enhanced impurity transport from an edge harmonic oscillation, thought to be a saturated kink- peeling mode driven by rotation shear. In addition, the impurity confinement time is not affected by rotation, even though the energy confinement time and measured E×B shear are observed to increase at low toroidal rotation. Together with demonstrations of high beta, high confinement and low q_{95} for many energy confinement times, these results suggest QH-mode as a potentially attractive operating scenario for the ITER Q=10 mission.
Extending the physics basis of quiescent H-mode toward ITER relevant parameters
Solomon, W. M.; Burrell, K. H.; Fenstermacher, M. E.; Garofalo, A. M.; Grierson, B. A.; Loarte, A.; McKee, G. R.; Nazikian, R.; Osborne, T. H.; Snyder, P. B.
2015-06-26
Recent experiments on DIII-D have addressed several long-standing issues needed to establish quiescent H-mode (QH-mode) as a viable operating scenario for ITER. In the past, QH-mode was associated with low density operation, but has now been extended to high normalized densities compatible with operation envisioned for ITER. Through the use of strong shaping, QH-mode plasmas have been maintained at high densities, both absolute (more » $$\\bar{n}$$e ≈ 7 × 1019 m₋3) and normalized Greenwald fraction ($$\\bar{n}$$e/nG > 0.7). In these plasmas, the pedestal can evolve to very high pressure and edge current as the density is increased. High density QH-mode operation with strong shaping has allowed access to a previously predicted regime of very high pedestal dubbed “Super H-mode”. Calculations of the pedestal height and width from the EPED model are quantitatively consistent with the experimentally observed density evolution. The confirmation of the shape dependence of the maximum density threshold for QH-mode helps validate the underlying theoretical model of peeling- ballooning modes for ELM stability. In general, QH-mode is found to achieve ELM- stable operation while maintaining adequate impurity exhaust, due to the enhanced impurity transport from an edge harmonic oscillation, thought to be a saturated kink- peeling mode driven by rotation shear. In addition, the impurity confinement time is not affected by rotation, even though the energy confinement time and measured E×B shear are observed to increase at low toroidal rotation. Together with demonstrations of high beta, high confinement and low q95 for many energy confinement times, these results suggest QH-mode as a potentially attractive operating scenario for the ITER Q=10 mission.« less
A Novel Iterative Scheme and Its Application to Differential Equations
Khan, Yasir; Naeem, F.; Šmarda, Zdeněk
2014-01-01
The purpose of this paper is to employ an alternative approach to reconstruct the standard variational iteration algorithm II proposed by He, including Lagrange multiplier, and to give a simpler formulation of Adomian decomposition and modified Adomian decomposition method in terms of newly proposed variational iteration method-II (VIM). Through careful investigation of the earlier variational iteration algorithm and Adomian decomposition method, we find unnecessary calculations for Lagrange multiplier and also repeated calculations involved in each iteration, respectively. Several examples are given to verify the reliability and efficiency of the method. PMID:24757427
ITER Cryoplant Status and Economics of the LHe plants
NASA Astrophysics Data System (ADS)
Monneret, E.; Chalifour, M.; Bonneton, M.; Fauve, E.; Voigt, T.; Badgujar, S.; Chang, H.-S.; Vincent, G.
The ITER cryoplant is composed of helium and nitrogen refrigerators and generator combined with 80 K helium loop plants and external purification systems. Storage and recovery of the helium inventory is provided in warm and cold (80 K and 4.5 K) helium tanks.The conceptual design of the ITER cryoplant has been completed, the technical requirements defined for industrial procurement and contracts signed with industry. Each contract covers the design, manufacturing, installation and commissioning. Design is under finalization and manufacturing has started. First deliveries are scheduled by end of 2015.The various cryoplant systems are designed based on recognized codes and international standards to meet the availability, the reliability and the time between maintenance imposed by the long-term uninterrupted operation of the ITER Tokamak. In addition, ITER has to consider the constraint of a nuclear installation.ITER Organization (IO) is responsible for the liquid helium (LHe) Plants contract signed end of 2012 with industry. It is composed of three LHe Plants, working in parallel and able to provide a total average cooling capacity of 75 kW at 4.5 K. Based on concept designed developed with industries and the procurement phase, ITER has accumulated data to broaden the scaling laws for costing such systems.After describing the status of ITER cryoplant part of the cryogenic system, we shall present the economics of the ITER LHe Plants based on key design requirements, choice and challenges of this ITER Organization procurement.
Optimal parameters for linear second-degree stationary iterative methods
Manteuffel, T. A.
1980-11-01
It is shown that the optimal parameters for linear second-degree stationary iterative methods applied to nonsymmetric linear systems can be found by solving the same minimax problem used to find optimal parameters for the Tchebychev iteration. In fact, the Tchebychev iteration is asymptotically equivalent to a linear second-degree stationary method. The method of finding optimal parameters for the Tchebychev iteration given by Manteuffel (Numer. Math., 28, 307-27 (1977)) can be used to find optimal parameters for the stationary method as well. 1 figure.
A synopsis of collective alpha effects and implications for ITER
Sigmar, D.J.
1990-10-01
This paper discusses the following: Alpha Interaction with Toroidal Alfven Eigenmodes; Alpha Interaction with Ballooning Modes; Alpha Interaction with Fishbone Oscillations; and Implications for ITER.
Unsupervised iterative detection of land mines in highly cluttered environments.
Batman, Sinan; Goutsias, John
2003-01-01
An unsupervised iterative scheme is proposed for land mine detection in heavily cluttered scenes. This scheme is based on iterating hybrid multispectral filters that consist of a decorrelating linear transform coupled with a nonlinear morphological detector. Detections extracted from the first pass are used to improve results in subsequent iterations. The procedure stops after a predetermined number of iterations. The proposed scheme addresses several weaknesses associated with previous adaptations of morphological approaches to land mine detection. Improvement in detection performance, robustness with respect to clutter inhomogeneities, a completely unsupervised operation, and computational efficiency are the main highlights of the method. Experimental results reveal excellent performance.
Bounded-Angle Iterative Decoding of LDPC Codes
NASA Technical Reports Server (NTRS)
Dolinar, Samuel; Andrews, Kenneth; Pollara, Fabrizio; Divsalar, Dariush
2009-01-01
Bounded-angle iterative decoding is a modified version of conventional iterative decoding, conceived as a means of reducing undetected-error rates for short low-density parity-check (LDPC) codes. For a given code, bounded-angle iterative decoding can be implemented by means of a simple modification of the decoder algorithm, without redesigning the code. Bounded-angle iterative decoding is based on a representation of received words and code words as vectors in an n-dimensional Euclidean space (where n is an integer).
Tokamak plasma self-organization and the possibility to have the peaked density profile in ITER
NASA Astrophysics Data System (ADS)
Razumova, K. A.; Andreev, V. F.; Kislov, A. Ya.; Kirneva, N. A.; Lysenko, S. E.; Pavlov, Yu. D.; Shafranov, T. V.; T-10 Team; Donné, A. J. H.; Hogeweij, G. M. D.; Spakman, G. W.; Jaspers, R.; TEXTOR Team; Kantor, M.; Walsh, M.
2009-06-01
The self-organization of a tokamak plasma is a fundamental turbulent plasma phenomenon, which leads to the formation of a self-consistent pressure profile. This phenomenon has been investigated in several tokamaks with different methods of heating. It is shown that the normalized pressure profile has a universal shape for a wide class of tokamaks and regimes, if the normalized radius ρ = r/(IpR/κB)1/2 is used. The consequences of this phenomenon for low aspect ratio tokamaks, the optimal deposition of additional heating, fast velocity of heat/cold pulse propagation and the possibility of obtaining a peaked density profile in ITER are discussed.
NASA Astrophysics Data System (ADS)
Agoras, M.; Ponte Castañeda, P.
2013-03-01
Analytical estimates are obtained for the effective constitutive response of porous viscoplastic materials consisting of aligned ellipsoidal voids that are distributed randomly with "ellipsoidal" symmetry in the matrix material. These estimates are obtained by means of a novel iterative homogenization strategy recently proposed by Ponte Castañeda (2012), and can be shown to be bounds for certain classes of multi-scale microstructures. By design, the resulting constitutive model agrees exactly with the earlier "variational linear comparison" model at the first iteration (N=1), and provides estimates that get progressively more accurate as the number of iterations increases (N→∞), especially for high-triaxiality loading conditions, and low porosity and strain-rate sensitivity. However, in practice, a small number of iterations (N≈10) is sufficient to get very accurate results. It is important to emphasize that, unlike other models that have been proposed in the literature, the new model requires no fitting parameters, solely depending on the properties of the matrix phase and microstructural information, such as the porosity, the average void shape and orientation, as well as the generally different shape and orientation of their distribution. Results are given for the yield and gauge surfaces of ideally plastic and power-law viscoplastic porous materials for the special cases of aligned spheroidal and ellipsoidal voids, and the results are compared with available numerical results and with the results of other models. Compared to available numerical results, the new estimates are found to be quite accurate, while they also provide more flexibility than competing models in terms of the characterization of the microstructure. In particular, it was found that the effect of different shapes for the average pore shape and distribution on the yield surfaces of the porous materials can be significant at high triaxialities, even for very small porosities. In addition
Enhancing the cosmic shear power spectrum
NASA Astrophysics Data System (ADS)
Simpson, Fergus; Harnois-Déraps, Joachim; Heymans, Catherine; Jimenez, Raul; Joachimi, Benjamin; Verde, Licia
2016-02-01
Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However, substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the Ωm - σ8 plane by more than a factor of 3.
Fission Spectrum Related Uncertainties
G. Aliberti; I. Kodeli; G. Palmiotti; M. Salvatores
2007-10-01
The paper presents a preliminary uncertainty analysis related to potential uncertainties on the fission spectrum data. Consistent results are shown for a reference fast reactor design configuration and for experimental thermal configurations. However the results obtained indicate the need for further analysis, in particular in terms of fission spectrum uncertainty data assessment.
Radiation detector spectrum simulator
Wolf, Michael A.; Crowell, John M.
1987-01-01
A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.
Radiation detector spectrum simulator
Wolf, M.A.; Crowell, J.M.
1985-04-09
A small battery operated nuclear spectrum simulator having a noise source generates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith to generate several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.
Fetal Alcohol Spectrum Disorder
ERIC Educational Resources Information Center
Caley, Linda M.; Kramer, Charlotte; Robinson, Luther K.
2005-01-01
Fetal alcohol spectrum disorder (FASD) is a serious and widespread problem in this country. Positioned within the community with links to children, families, and healthcare systems, school nurses are a critical element in the prevention and treatment of those affected by fetal alcohol spectrum disorder. Although most school nurses are familiar…
Stebbins, A.
1997-05-01
Here we give an introduction to the observed spectrum of the Cosmic Microwave Background Radiation (CMBR) and discuss what can be learned about it. Particular attention will be given to how Compton scattering can distort the spectrum of the CMBR. An incomplete bibliography of relevant papers is also provided.
Shape analysis of corpus callosum in phenylketonuria using a new 3D correspondence algorithm
NASA Astrophysics Data System (ADS)
He, Qing; Christ, Shawn E.; Karsch, Kevin; Peck, Dawn; Duan, Ye
2010-03-01
Statistical shape analysis of brain structures has gained increasing interest from neuroimaging community because it can precisely locate shape differences between healthy and pathological structures. The most difficult and crucial problem is establishing shape correspondence among individual 3D shapes. This paper proposes a new algorithm for 3D shape correspondence. A set of landmarks are sampled on a template shape, and initial correspondence is established between the template and the target shape based on the similarity of locations and normal directions. The landmarks on the target are then refined by iterative thin plate spline. The algorithm is simple and fast, and no spherical mapping is needed. We apply our method to the statistical shape analysis of the corpus callosum (CC) in phenylketonuria (PKU), and significant local shape differences between the patients and the controls are found in the most anterior and posterior aspects of the corpus callosum.
The Optical Spectrum of the Geminga Pulsar
NASA Technical Reports Server (NTRS)
Martin, Christopher; Halpern, Jules P.; Schiminovich, David; Oliversen, Ronald (Technical Monitor)
2001-01-01
We obtained an optical spectrum of the isolated pulsar Geminga at the Keck Observatory. The optical object is at the limit of spectroscopic capability of any telescope, with a continuum flux that is approx. 0.5% of the dark sky on Mauna Kea. With particular attention paid to the dominant systematics of sky subtraction in our observing and analysis methods, we attained approx. 0.1% systematics in heavily binned spectra. The resulting spectrum spanning 3700 - 8000 A has a flat power-law shape f(sub nu) proportional to nu(exp -0.8) and a broad dip over 6300 - 6500 A. Thermal radiation cannot explain the optical spectrum of Geminga. The dominant component can be modeled as either electron synchrotron emission and ion (proton) cyclotron absorption, or ion cyclotron emission, the latter in a 10(exp 11) G magnetic field.
Gingold, E; Dave, J
2014-06-01
Purpose: The purpose of this study was to compare a new model-based iterative reconstruction with existing reconstruction methods (filtered backprojection and basic iterative reconstruction) using quantitative analysis of standard image quality phantom images. Methods: An ACR accreditation phantom (Gammex 464) and a CATPHAN600 phantom were scanned using 3 routine clinical acquisition protocols (adult axial brain, adult abdomen, and pediatric abdomen) on a Philips iCT system. Each scan was acquired using default conditions and 75%, 50% and 25% dose levels. Images were reconstructed using standard filtered backprojection (FBP), conventional iterative reconstruction (iDose4) and a prototype model-based iterative reconstruction (IMR). Phantom measurements included CT number accuracy, contrast to noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD), and noise power spectrum (NPS). Results: The choice of reconstruction method had no effect on CT number accuracy, or MTF (p<0.01). The CNR of a 6 HU contrast target was improved by 1–67% with iDose4 relative to FBP, while IMR improved CNR by 145–367% across all protocols and dose levels. Within each scan protocol, the CNR improvement from IMR vs FBP showed a general trend of greater improvement at lower dose levels. NPS magnitude was greatest for FBP and lowest for IMR. The NPS of the IMR reconstruction showed a pronounced decrease with increasing spatial frequency, consistent with the unusual noise texture seen in IMR images. Conclusion: Iterative Model Reconstruction reduces noise and improves contrast-to-noise ratio without sacrificing spatial resolution in CT phantom images. This offers the possibility of radiation dose reduction and improved low contrast detectability compared with filtered backprojection or conventional iterative reconstruction.
Iterative Voting for Inference of Structural Saliency andCharacterization of Subcellular Events
Parvin, Bahram; Yang, Qing; Han, Ju; Chang, Hang; Rydberg, Bjorn; Barcellos-Hoff, Mary Helen
2006-05-06
Saliency is an important perceptual cue that occurs at different levels of resolution. Important attributes of saliency are symmetry, continuity, and closure. Detection of these attributes is often hindered by noise, variation in scale, and incomplete information. This paper introduces the iterative voting method, which uses oriented kernels for inferring saliency as it relates to symmetry. A unique aspect of the technique is the kernel topography, which is refined and reoriented iteratively. The technique can cluster and group nonconvex perceptual circular symmetries along the radial line of an object's shape. It has an excellent noise immunity and is shown to be tolerant to perturbation in scale. The application of this technique to images obtained through various modes of microscopy is demonstrated. Furthermore, as a case example, the method has been applied to quantify kinetics of nuclear foci formation that are formed by phosphorylation of hislone {gamma}H2AX following ionizing radiation. Iterative voting has been implemented in both 2-D and 3-D for multi image analysis.
Some results concerning linear iterative (systolic) arrays
Ibarra, O.H.; Palis, M.A.; Kim, S.M.
1985-05-01
The authors have shown some new interesting results concerning the properties, power, and limitations of various types of linear iterative (systolic) arrays. The method they employed consisted of finding sequential machine characterizations of these array models, and then using the characterizations to prove the results. Because of the absence of any concurrency and synchronization problems, the authors obtained simple proofs to results which when proved directly on the arrays would seem very difficult. The characterizations, therefore, provide a novel and promising method which can be used to analyze other systolic systems. In the future they hope to extend this methodology to the study of two-dimensional and multidimensional systolic arrays, and other systolic systems with different interconnection networks.
Structural analysis of ITER magnet feeders
Ilyin, Yuri; Gung, Chen-Yu; Bauer, Pierre; Chen, Yonghua; Jong, Cornelis; Devred, Arnaud; Mitchell, Neil; Lorriere, Philippe; Farek, Jaromir; Nannini, Matthieu
2012-06-15
This paper summarizes the results of the static structural analyses, which were conducted in support of the ITER magnet feeder design with the aim of validating certain components against the structural design criteria. While almost every feeder has unique features, they all share many common constructional elements and the same functional specifications. The analysis approach to assess the load conditions and stresses that have driven the design is equivalent for all feeders, except for particularities that needed to be modeled in each case. The mechanical analysis of the feeders follows the sub-modeling approach: the results of the global mechanical model of a feeder assembly are used as input for the detailed models of the feeder' sub-assemblies or single components. Examples of such approach, including the load conditions, stress assessment criteria and solutions for the most critical components, are discussed. It has been concluded that the feeder system is safe in the referential operation scenarios. (authors)
Iterative methods for Toeplitz-like matrices
Huckle, T.
1994-12-31
In this paper the author will give a survey on iterative methods for solving linear equations with Toeplitz matrices, Block Toeplitz matrices, Toeplitz plus Hankel matrices, and matrices with low displacement rank. He will treat the following subjects: (1) optimal (w)-circulant preconditioners is a generalization of circulant preconditioners; (2) Optimal implementation of circulant-like preconditioners in the complex and real case; (3) preconditioning of near-singular matrices; what kind of preconditioners can be used in this case; (4) circulant preconditioning for more general classes of Toeplitz matrices; what can be said about matrices with coefficients that are not l{sub 1}-sequences; (5) preconditioners for Toeplitz least squares problems, for block Toeplitz matrices, and for Toeplitz plus Hankel matrices.
Exact iterative reconstruction for the interior problem
Zeng, Gengsheng L; Gullberg, Grant T
2010-01-01
There is a trend in single photon emission computed tomography (SPECT) that small and dedicated imaging systems are becoming popular. For example, many companies are developing small dedicated cardiac SPECT systems with different designs. These dedicated systems have a smaller field of view (FOV) than a full-size clinical system. Thus data truncation has become the norm rather than the exception in these systems. Therefore, it is important to develop region of interest (ROI) reconstruction algorithms using truncated data. This paper is a stepping stone toward this direction. This paper shows that the common generic iterative image reconstruction algorithms are able to exactly reconstruct the ROI under the conditions that the convex ROI is fully sampled and the image value in a sub-region within the ROI is known. If the ROI includes a sub-region that is outside the patient body, then the conditions can be easily satisfied. PMID:19741279
ITER CENTRAL SOLENOID COIL INSULATION QUALIFICATION
Martovetsky, N N; Mann, T L; Miller, J R; Freudenberg, K D; Reed, R P; Walsh, R P; McColskey, J D; Evans, D
2009-06-11
An insulation system for ITER Central Solenoid must have sufficiently high electrical and structural strength. Design efforts to bring stresses in the turn and layer insulation within allowables failed. It turned out to be impossible to eliminate high local tensile stresses in the winding pack. When high local stresses can not be designed out, the qualification procedure requires verification of the acceptable structural and electrical strength by testing. We built two 4 x 4 arrays of the conductor jacket with two options of the CS insulation and subjected the arrays to 1.2 million compressive cycles at 60 MPa and at 76 K. Such conditions simulated stresses in the CS insulation. We performed voltage withstand tests and after end of cycling we measured the breakdown voltages between in the arrays. After that we dissectioned the arrays and studied micro cracks in the insulation. We report details of the specimens preparation, test procedures and test results.
Robust tooth surface reconstruction by iterative deformation.
Jiang, Xiaotong; Dai, Ning; Cheng, Xiaosheng; Wang, Jun; Peng, Qingjin; Liu, Hao; Cheng, Cheng
2016-01-01
Digital design technologies have been applied extensively in dental medicine, especially in the field of dental restoration. The all-ceramic crown is an important restoration type of dental CAD systems. This paper presents a robust tooth surface reconstruction algorithm for all-ceramic crown design. The algorithm involves three necessary steps: standard tooth initial positioning and division; salient feature point extraction using Morse theory; and standard tooth deformation using iterative Laplacian Surface Editing and mesh stitching. This algorithm can retain the morphological features of the tooth surface well. It is robust and suitable for almost all types of teeth, including incisor, canine, premolar, and molar. Moreover, it allows dental technicians to use their own preferred library teeth for reconstruction. The algorithm has been successfully integrated in our Dental CAD system, more than 1000 clinical cases have been tested to demonstrate the robustness and effectiveness of the proposed algorithm.
Iterative restoration of SPECT projection images
Glick, S.J.; Xia, W.
1997-04-01
Photon attenuation and the limited nonstationary spatial resolution of the detector can reduce both qualitative and quantitative image quality in single photon emission computed tomography (SPECT). In this paper, a reconstruction approach is described which can compensate for both of these degradations. The approach involves processing the project data with Bellini`s method for attenuation compensation followed by an iterative deconvolution technique which uses the frequency distance principle (FDP) to model the distance-dependent camera blur. Modeling of the camera blur with the FDP allows an efficient implementation using fast Fourier transformation (FFT) methods. After processing of the project data, reconstruction is performed using filtered backprojections. Simulation studies using two different brain phantoms show that this approach gives reconstructions with a favorable bias versus noise tradeoff, provides no visually undesirable noise artifacts, and requires a low computational load.
Iterated Gate Teleportation and Blind Quantum Computation.
Pérez-Delgado, Carlos A; Fitzsimons, Joseph F
2015-06-01
Blind quantum computation allows a user to delegate a computation to an untrusted server while keeping the computation hidden. A number of recent works have sought to establish bounds on the communication requirements necessary to implement blind computation, and a bound based on the no-programming theorem of Nielsen and Chuang has emerged as a natural limiting factor. Here we show that this constraint only holds in limited scenarios, and show how to overcome it using a novel method of iterated gate teleportations. This technique enables drastic reductions in the communication required for distributed quantum protocols, extending beyond the blind computation setting. Applied to blind quantum computation, this technique offers significant efficiency improvements, and in some scenarios offers an exponential reduction in communication requirements. PMID:26196609
Learning to improve iterative repair scheduling
NASA Technical Reports Server (NTRS)
Zweben, Monte; Davis, Eugene
1992-01-01
This paper presents a general learning method for dynamically selecting between repair heuristics in an iterative repair scheduling system. The system employs a version of explanation-based learning called Plausible Explanation-Based Learning (PEBL) that uses multiple examples to confirm conjectured explanations. The basic approach is to conjecture contradictions between a heuristic and statistics that measure the quality of the heuristic. When these contradictions are confirmed, a different heuristic is selected. To motivate the utility of this approach we present an empirical evaluation of the performance of a scheduling system with respect to two different repair strategies. We show that the scheduler that learns to choose between the heuristics outperforms the same scheduler with any one of two heuristics alone.
Iterative Precise Conductivity Measurement with IDEs.
Hubálek, Jaromír
2015-05-22
The paper presents a new approach in the field of precise electrolytic conductivity measurements with planar thin- and thick-film electrodes. This novel measuring method was developed for measurement with comb-like electrodes called interdigitated electrodes (IDEs). Correction characteristics over a wide range of specific conductivities were determined from an interface impedance characterization of the thick-film IDEs. The local maximum of the capacitive part of the interface impedance is used for corrections to get linear responses. The measuring frequency was determined at a wide range of measured conductivity. An iteration mode of measurements was suggested to precisely measure the conductivity at the right frequency in order to achieve a highly accurate response. The method takes precise conductivity measurements in concentration ranges from 10(-6) to 1 M without electrode cell replacement.
ITER L-Mode Confinement Database
S.M. Kaye and the ITER Confinement Database Working Group
1997-10-01
This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated (OH) only. Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER. The L-mode thermal confinement time scaling was determined from a subset of 1312 entries for which the thermal confinement time scaling was provided.
ITER L-mode confinement database
Kaye, S.M.
1997-10-06
This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated only (OH). Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER.
Generating fracture networks using iterated function systems
NASA Astrophysics Data System (ADS)
Mohrlok, U.; Liedl, R.
In order to model flow and transport in fractured rocks it is important to know the geometry of the fracture network. A stochastic approach is commonly used to generate a synthetic fracture network from the statistics measured at a natural fracture network. The approach presented herein is able to incorporate the structures found in a natural fracture network into the synthetic fracture network. These synthetic fracture networks are the images generated by Iterated Function Systems (IFS) as introduced by Barnsley (1988). The conditions these IFS have to fulfil to determine images resembling fracture networks and the effects of their parameters on the images are discussed. It is possible to define the parameters of the IFS in order to generate some properties of a fracture network. The image of an IFS consists of many single points and has to be suitably processed for further use.
Orbit of an image under iterated system
NASA Astrophysics Data System (ADS)
Singh, S. L.; Mishra, S. N.; Jain, Sarika
2011-03-01
An orbital picture depicts the path of an object under semi-group of transformations. The concept initially given by Barnsley [3] has utmost importance in image compression, biological modeling and other areas of fractal geometry. In this paper, we introduce superior iterations to study the role of linear and nonlinear transformations on the orbit of an object. Various characteristics of the computed figures have been discussed to indicate the usefulness of study in mathematical analysis. Modified algorithms are given to compute the orbital picture and V-variable orbital picture. An algorithm to calculate the distance between images makes the study motivating. A brief discussion about the proof of the Cauchy sequence of images is also given.
Generating fracture networks using iterated function systems
NASA Astrophysics Data System (ADS)
Mohrlok, U.; Liedl, R.
1996-03-01
In order to model flow and transport in fractured rocks it is important to know the geometry of the fracture network. A stochastic approach is commonly used to generate a synthetic fracture network from the statistics measured at a natural fracture network. The approach presented herein is able to incorporate the structures found in a natural fracture network into the synthetic fracture network. These synthetic fracture networks are the images generated by Iterated Function Systems (IFS) as introduced by Barnsley (1988). The conditions these IFS have to fulfil to determine images resembling fracture networks and the effects of their parameters on the images are discussed. It is possible to define the parameters of the IFS in order to generate some properties of a fracture network. The image of an IFS consists of many single points and has to be suitably processed for further use.
Iterated Gate Teleportation and Blind Quantum Computation.
Pérez-Delgado, Carlos A; Fitzsimons, Joseph F
2015-06-01
Blind quantum computation allows a user to delegate a computation to an untrusted server while keeping the computation hidden. A number of recent works have sought to establish bounds on the communication requirements necessary to implement blind computation, and a bound based on the no-programming theorem of Nielsen and Chuang has emerged as a natural limiting factor. Here we show that this constraint only holds in limited scenarios, and show how to overcome it using a novel method of iterated gate teleportations. This technique enables drastic reductions in the communication required for distributed quantum protocols, extending beyond the blind computation setting. Applied to blind quantum computation, this technique offers significant efficiency improvements, and in some scenarios offers an exponential reduction in communication requirements.
Iterated upwind schemes for gas dynamics
Smolarkiewicz, Piotr K. Szmelter, Joanna
2009-01-10
A class of high-resolution schemes established in integration of anelastic equations is extended to fully compressible flows, and documented for unsteady (and steady) problems through a span of Mach numbers from zero to supersonic. The schemes stem from iterated upwind technology of the multidimensional positive definite advection transport algorithm (MPDATA). The derived algorithms employ standard and modified forms of the equations of gas dynamics for conservation of mass, momentum and either total or internal energy as well as potential temperature. Numerical examples from elementary wave propagation, through computational aerodynamics benchmarks, to atmospheric small- and large-amplitude acoustics with intricate wave-flow interactions verify the approach for both structured and unstructured meshes, and demonstrate its flexibility and robustness.
Electronic noise modeling in statistical iterative reconstruction.
Xu, Jingyan; Tsui, Benjamin M W
2009-06-01
We consider electronic noise modeling in tomographic image reconstruction when the measured signal is the sum of a Gaussian distributed electronic noise component and another random variable whose log-likelihood function satisfies a certain linearity condition. Examples of such likelihood functions include the Poisson distribution and an exponential dispersion (ED) model that can approximate the signal statistics in integration mode X-ray detectors. We formulate the image reconstruction problem as a maximum-likelihood estimation problem. Using an expectation-maximization approach, we demonstrate that a reconstruction algorithm can be obtained following a simple substitution rule from the one previously derived without electronic noise considerations. To illustrate the applicability of the substitution rule, we present examples of a fully iterative reconstruction algorithm and a sinogram smoothing algorithm both in transmission CT reconstruction when the measured signal contains additive electronic noise. Our simulation studies show the potential usefulness of accurate electronic noise modeling in low-dose CT applications.
Wind speed power spectrum analysis for Bushland, Texas
Eggleston, E.D.
1996-12-31
Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.
Nuclear Forensic Inferences Using Iterative Multidimensional Statistics
Robel, M; Kristo, M J; Heller, M A
2009-06-09
Nuclear forensics involves the analysis of interdicted nuclear material for specific material characteristics (referred to as 'signatures') that imply specific geographical locations, production processes, culprit intentions, etc. Predictive signatures rely on expert knowledge of physics, chemistry, and engineering to develop inferences from these material characteristics. Comparative signatures, on the other hand, rely on comparison of the material characteristics of the interdicted sample (the 'questioned sample' in FBI parlance) with those of a set of known samples. In the ideal case, the set of known samples would be a comprehensive nuclear forensics database, a database which does not currently exist. In fact, our ability to analyze interdicted samples and produce an extensive list of precise materials characteristics far exceeds our ability to interpret the results. Therefore, as we seek to develop the extensive databases necessary for nuclear forensics, we must also develop the methods necessary to produce the necessary inferences from comparison of our analytical results with these large, multidimensional sets of data. In the work reported here, we used a large, multidimensional dataset of results from quality control analyses of uranium ore concentrate (UOC, sometimes called 'yellowcake'). We have found that traditional multidimensional techniques, such as principal components analysis (PCA), are especially useful for understanding such datasets and drawing relevant conclusions. In particular, we have developed an iterative partial least squares-discriminant analysis (PLS-DA) procedure that has proven especially adept at identifying the production location of unknown UOC samples. By removing classes which fell far outside the initial decision boundary, and then rebuilding the PLS-DA model, we have consistently produced better and more definitive attributions than with a single pass classification approach. Performance of the iterative PLS-DA method
Error bounds from extra precise iterative refinement
Demmel, James; Hida, Yozo; Kahan, William; Li, Xiaoye S.; Mukherjee, Soni; Riedy, E. Jason
2005-02-07
We present the design and testing of an algorithm for iterative refinement of the solution of linear equations, where the residual is computed with extra precision. This algorithm was originally proposed in the 1960s [6, 22] as a means to compute very accurate solutions to all but the most ill-conditioned linear systems of equations. However two obstacles have until now prevented its adoption in standard subroutine libraries like LAPACK: (1) There was no standard way to access the higher precision arithmetic needed to compute residuals, and (2) it was unclear how to compute a reliable error bound for the computed solution. The completion of the new BLAS Technical Forum Standard [5] has recently removed the first obstacle. To overcome the second obstacle, we show how a single application of iterative refinement can be used to compute an error bound in any norm at small cost, and use this to compute both an error bound in the usual infinity norm, and a componentwise relative error bound. We report extensive test results on over 6.2 million matrices of dimension 5, 10, 100, and 1000. As long as a normwise (resp. componentwise) condition number computed by the algorithm is less than 1/max{l_brace}10,{radical}n{r_brace} {var_epsilon}{sub w}, the computed normwise (resp. componentwise) error bound is at most 2 max{l_brace}10,{radical}n{r_brace} {center_dot} {var_epsilon}{sub w}, and indeed bounds the true error. Here, n is the matrix dimension and w is single precision roundoff error. For worse conditioned problems, we get similarly small correct error bounds in over 89.4% of cases.
An iterative subaperture position correction algorithm
NASA Astrophysics Data System (ADS)
Lo, Weng-Hou; Lin, Po-Chih; Chen, Yi-Chun
2015-08-01
The subaperture stitching interferometry is a technique suitable for testing high numerical-aperture optics, large-diameter spherical lenses and aspheric optics. In the stitching process, each subaperture has to be placed at its correct position in a global coordinate, and the positioning precision would affect the accuracy of stitching result. However, the mechanical limitations in the alignment process as well as vibrations during the measurement would induce inevitable subaperture position uncertainties. In our previous study, a rotational scanning subaperture stitching interferometer has been constructed. This paper provides an iterative algorithm to correct the subaperture position without altering the interferometer configuration. Each subaperture is first placed at its geometric position estimated according to the F number of reference lens, the measurement zenithal angle and the number of pixels along the width of subaperture. By using the concept of differentiation, a shift compensator along the radial direction of the global coordinate is added into the stitching algorithm. The algorithm includes two kinds of compensators: one for the geometric null with four compensators of piston, two directional tilts and defocus, and the other for the position correction with the shift compensator. These compensators are computed iteratively to minimize the phase differences in the overlapped regions of subapertures in a least-squares sense. The simulation results demonstrate that the proposed method works to the position accuracy of 0.001 pixels for both the single-ring and multiple-ring configurations. Experimental verifications with the single-ring and multiple-ring data also show the effectiveness of the algorithm.
Los Alamos National Laboratory, Mailstop M888, Los Alamos, NM 87545, USA; Lawrence Berkeley National Laboratory, One Cyclotron Road, Building 64R0121, Berkeley, CA 94720, USA; Department of Haematology, University of Cambridge, Cambridge CB2 0XY, England; Terwilliger, Thomas; Terwilliger, T.C.; Grosse-Kunstleve, Ralf Wilhelm; Afonine, P.V.; Moriarty, N.W.; Zwart, P.H.; Hung, L.-W.; Read, R.J.; Adams, P.D.
2008-02-12
A procedure for carrying out iterative model-building, density modification and refinement is presented in which the density in an OMIT region is essentially unbiased by an atomic model. Density from a set of overlapping OMIT regions can be combined to create a composite 'Iterative-Build' OMIT map that is everywhere unbiased by an atomic model but also everywhere benefiting from the model-based information present elsewhere in the unit cell. The procedure may have applications in the validation of specific features in atomic models as well as in overall model validation. The procedure is demonstrated with a molecular replacement structure and with an experimentally-phased structure, and a variation on the method is demonstrated by removing model bias from a structure from the Protein Data Bank.
Preconditioned iterative methods for inhomogeneous acoustic scattering applications
NASA Astrophysics Data System (ADS)
Sifuentes, Josef
This thesis develops and analyzes efficient iterative methods for solving discretizations of the Lippmann--Schwinger integral equation for inhomogeneous acoustic scattering. Analysis and numerical illustrations of the spectral properties of the scattering problem demonstrate that a significant portion of the spectrum is approximated well on coarse grids. To exploit this, I develop a novel restarted GMRES method with adaptive deflation preconditioning based on spectral approximations on multiple grids. Much of the literature in this field is based on exact deflation, which is not feasible for most practical computations. This thesis provides an analytical framework for general approximate deflation methods and suggests a way to rigorously study a host of inexactly-applied preconditioners. Approximate deflation algorithms are implemented for scattering through thin inhomogeneities in photonic band gap problems. I also develop a short term recurrence for solving the one dimensional version of the problem that exploits the observation that the integral operator is a low rank perturbation of a self-adjoint operator. This method is based on strategies for solving Schur complement problems, and provides an alternative to a recent short term recurrence algorithm for matrices with such structure that we show to be numerically unstable for this application. The restarted GMRES method with adaptive deflation preconditioning over multiple grids, as well as the short term recurrence method for operators with low rank skew-adjoint parts, are very effective for reducing both the computational time and computer memory required to solve acoustic scattering problems. Furthermore, the methods are sufficiently general to be applicable to a wide class of problems.
Li, Ke; Tang, Jie; Chen, Guang-Hong
2014-01-01
Purpose: To reduce radiation dose in CT imaging, the statistical model based iterative reconstruction (MBIR) method has been introduced for clinical use. Based on the principle of MBIR and its nonlinear nature, the noise performance of MBIR is expected to be different from that of the well-understood filtered backprojection (FBP) reconstruction method. The purpose of this work is to experimentally assess the unique noise characteristics of MBIR using a state-of-the-art clinical CT system. Methods: Three physical phantoms, including a water cylinder and two pediatric head phantoms, were scanned in axial scanning mode using a 64-slice CT scanner (Discovery CT750 HD, GE Healthcare, Waukesha, WI) at seven different mAs levels (5, 12.5, 25, 50, 100, 200, 300). At each mAs level, each phantom was repeatedly scanned 50 times to generate an image ensemble for noise analysis. Both the FBP method with a standard kernel and the MBIR method (Veo®, GE Healthcare, Waukesha, WI) were used for CT image reconstruction. Three-dimensional (3D) noise power spectrum (NPS), two-dimensional (2D) NPS, and zero-dimensional NPS (noise variance) were assessed both globally and locally. Noise magnitude, noise spatial correlation, noise spatial uniformity and their dose dependence were examined for the two reconstruction methods. Results: (1) At each dose level and at each frequency, the magnitude of the NPS of MBIR was smaller than that of FBP. (2) While the shape of the NPS of FBP was dose-independent, the shape of the NPS of MBIR was strongly dose-dependent; lower dose lead to a “redder” NPS with a lower mean frequency value. (3) The noise standard deviation (σ) of MBIR and dose were found to be related through a power law of σ ∝ (dose)−β with the component β ≈ 0.25, which violated the classical σ ∝ (dose)−0.5 power law in FBP. (4) With MBIR, noise reduction was most prominent for thin image slices. (5) MBIR lead to better noise spatial uniformity when compared
Li, Ke; Tang, Jie; Chen, Guang-Hong
2014-04-15
Purpose: To reduce radiation dose in CT imaging, the statistical model based iterative reconstruction (MBIR) method has been introduced for clinical use. Based on the principle of MBIR and its nonlinear nature, the noise performance of MBIR is expected to be different from that of the well-understood filtered backprojection (FBP) reconstruction method. The purpose of this work is to experimentally assess the unique noise characteristics of MBIR using a state-of-the-art clinical CT system. Methods: Three physical phantoms, including a water cylinder and two pediatric head phantoms, were scanned in axial scanning mode using a 64-slice CT scanner (Discovery CT750 HD, GE Healthcare, Waukesha, WI) at seven different mAs levels (5, 12.5, 25, 50, 100, 200, 300). At each mAs level, each phantom was repeatedly scanned 50 times to generate an image ensemble for noise analysis. Both the FBP method with a standard kernel and the MBIR method (Veo{sup ®}, GE Healthcare, Waukesha, WI) were used for CT image reconstruction. Three-dimensional (3D) noise power spectrum (NPS), two-dimensional (2D) NPS, and zero-dimensional NPS (noise variance) were assessed both globally and locally. Noise magnitude, noise spatial correlation, noise spatial uniformity and their dose dependence were examined for the two reconstruction methods. Results: (1) At each dose level and at each frequency, the magnitude of the NPS of MBIR was smaller than that of FBP. (2) While the shape of the NPS of FBP was dose-independent, the shape of the NPS of MBIR was strongly dose-dependent; lower dose lead to a “redder” NPS with a lower mean frequency value. (3) The noise standard deviation (σ) of MBIR and dose were found to be related through a power law of σ ∝ (dose){sup −β} with the component β ≈ 0.25, which violated the classical σ ∝ (dose){sup −0.5} power law in FBP. (4) With MBIR, noise reduction was most prominent for thin image slices. (5) MBIR lead to better noise spatial
Li, Yangyang; Liu, Rui; Wang, Yang; Wen, Dong; Meng, Liangwei; Lu, Jinling; Li, Pengcheng
2016-04-18
Imaging through a scattering medium has been a main challenge in modern optical imaging field. Recently, imaging through scattering medium based on wavefront shaping has been reported. However, it has not been clearly investigated to apply the optical memory effect based iterative wavefront shaping technique in speed estimation of a moving object through scattering medium. Here, we proposed to combine the iterative wavefront shaping technique with laser speckle contrast analysis method to detect the relative speed changes of moving objects through scattering medium. Phantom experiments were performed to validate our method.
A Model and Simple Iterative Algorithm for Redundancy Analysis.
ERIC Educational Resources Information Center
Fornell, Claes; And Others
1988-01-01
This paper shows that redundancy maximization with J. K. Johansson's extension can be accomplished via a simple iterative algorithm based on H. Wold's Partial Least Squares. The model and the iterative algorithm for the least squares approach to redundancy maximization are presented. (TJH)
Lessons Drawn from ITER and Other Fusion International Collaborations
NASA Astrophysics Data System (ADS)
Dean, Stephen O.
1998-06-01
The international character of fusion research and development is described, with special emphasis on the ITER (International Thermonuclear Experimental Reactor) joint venture. The history of the ITER collaboration is traced. Lessons drawn that may prove useful for future ventures are presented.
An Iterative Method for Solving Variable Coefficient ODEs
ERIC Educational Resources Information Center
Deeba, Elias; Yoon, Jeong-Mi; Zafiris, Vasilis
2003-01-01
In this classroom note, the authors present a method to solve variable coefficients ordinary differential equations of the form p(x)y([squared])(x) + q(x)y([superscript 1])(x) + r(x)y(x) = 0. They propose an iterative method as an alternate method to solve the above equation. This iterative method is accessible to an undergraduate student studying…
Not so Complex: Iteration in the Complex Plane
ERIC Educational Resources Information Center
O'Dell, Robin S.
2014-01-01
The simple process of iteration can produce complex and beautiful figures. In this article, Robin O'Dell presents a set of tasks requiring students to use the geometric interpretation of complex number multiplication to construct linear iteration rules. When the outputs are plotted in the complex plane, the graphs trace pleasing designs…
Wall conditioning for ITER: Current experimental and modeling activities
NASA Astrophysics Data System (ADS)
Douai, D.; Kogut, D.; Wauters, T.; Brezinsek, S.; Hagelaar, G. J. M.; Hong, S. H.; Lomas, P. J.; Lyssoivan, A.; Nunes, I.; Pitts, R. A.; Rohde, V.; de Vries, P. C.
2015-08-01
Wall conditioning will be required in ITER to control fuel and impurity recycling, as well as tritium (T) inventory. Analysis of conditioning cycle on the JET, with its ITER-Like Wall is presented, evidencing reduced need for wall cleaning in ITER compared to JET-CFC. Using a novel 2D multi-fluid model, current density during Glow Discharge Conditioning (GDC) on the in-vessel plasma-facing components (PFC) of ITER is predicted to approach the simple expectation of total anode current divided by wall surface area. Baking of the divertor to 350 °C should desorb the majority of the co-deposited T. ITER foresees the use of low temperature plasma based techniques compatible with the permanent toroidal magnetic field, such as Ion (ICWC) or Electron Cyclotron Wall Conditioning (ECWC), for tritium removal between ITER plasma pulses. Extrapolation of JET ICWC results to ITER indicates removal comparable to estimated T-retention in nominal ITER D:T shots, whereas GDC may be unattractive for that purpose.
Experimental investigation of iterative reconstruction techniques for high resolution mammography
NASA Astrophysics Data System (ADS)
Vengrinovich, Valery L.; Zolotarev, Sergei A.; Linev, Vladimir N.
2014-02-01
The further development of the new iterative reconstruction algorithms to improve three-dimensional breast images quality restored from incomplete and noisy mammograms, is provided. The algebraic reconstruction method with simultaneous iterations - Simultaneous Algebraic Reconstruction Technique (SART) and the iterative method of statistical reconstruction Bayesian Iterative Reconstruction (BIR) are referred here as the preferable iterative methods suitable to improve the image quality. For better processing we use the Graphics Processing Unit (GPU). Method of minimizing the Total Variation (TV) is used as a priori support for regularization of iteration process and to reduce the level of noise in the reconstructed image. Preliminary results with physical phantoms show that all examined methods are capable to reconstruct structures layer-by-layer and to separate layers which images are overlapped in the Z- direction. It was found that the method of traditional Shift-And-Add tomosynthesis (SAA) is worse than iterative methods SART and BIR in terms of suppression of the anatomical noise and image blurring in between the adjacent layers. Despite of the fact that the measured contrast/noise ratio in the presence of low contrast internal structures is higher for the method of tomosynthesis SAA than for SART and BIR methods, its effectiveness in the presence of structured background is rather poor. In our opinion the optimal results can be achieved using Bayesian iterative reconstruction BIR.
Magnet design technical report---ITER definition phase
Henning, C.
1989-04-28
This report contains papers on the following topics: conceptual design; radiation damage of ITER magnet systems; insulation system of the magnets; critical current density and strain sensitivity; toroidal field coil structural analysis; stress analysis for the ITER central solenoid; and volt-second capabilities and PF magnet configurations.
Energy confinement scaling and the extrapolation to ITER
1997-11-01
The fusion performance of ITER is predicted using three different techniques; statistical analysis of the global energy confinement data, a dimensionless physics parameter similarity method and the full 1-D modeling of the plasma profiles. Although the three methods give overlapping predictions for the performance of ITER, the confidence interval of all of the techniques is still quite wide.
Validation of 1-D transport and sawtooth models for ITER
Connor, J.W.; Turner, M.F.; Attenberger, S.E.; Houlberg, W.A.
1996-12-31
In this paper the authors describe progress on validating a number of local transport models by comparing their predictions with relevant experimental data from a range of tokamaks in the ITER profile database. This database, the testing procedure and results are discussed. In addition a model for sawtooth oscillations is used to investigate their effect in an ITER plasma with alpha-particles.
The Effect of Iteration on the Design Performance of Primary School Children
ERIC Educational Resources Information Center
Looijenga, Annemarie; Klapwijk, Remke; de Vries, Marc J.
2015-01-01
Iteration during the design process is an essential element. Engineers optimize their design by iteration. Research on iteration in Primary Design Education is however scarce; possibly teachers believe they do not have enough time for iteration in daily classroom practices. Spontaneous playing behavior of children indicates that iteration fits in…
Fragment oriented molecular shapes.
Hain, Ethan; Camacho, Carlos J; Koes, David Ryan
2016-05-01
Molecular shape is an important concept in drug design and virtual screening. Shape similarity typically uses either alignment methods, which dynamically optimize molecular poses with respect to the query molecular shape, or feature vector methods, which are computationally less demanding but less accurate. The computational cost of alignment can be reduced by pre-aligning shapes, as is done with the Volumetric-Aligned Molecular Shapes (VAMS) method. Here, we introduce and evaluate fragment oriented molecular shapes (FOMS), where shapes are aligned based on molecular fragments. FOMS enables the use of shape constraints, a novel method for precisely specifying molecular shape queries that provides the ability to perform partial shape matching and supports search algorithms that function on an interactive time scale. When evaluated using the challenging Maximum Unbiased Validation dataset, shape constraints were able to extract significantly enriched subsets of compounds for the majority of targets, and FOMS matched or exceeded the performance of both VAMS and an optimizing alignment method of shape similarity search. PMID:27085751
ERIC Educational Resources Information Center
Markson, Lori; Diesendruck, Gil; Bloom, Paul
2008-01-01
When children learn the name of a novel object, they tend to extend that name to other objects similar in shape--a phenomenon referred to as the shape bias. Does the shape bias stem from learned associations between names and categories of objects, or does it derive from more general properties of children's understanding of language and the…
ERIC Educational Resources Information Center
Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo
2013-01-01
This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were not…
Image Restoration Using the Damped Richardson-Lucy Iteration
NASA Astrophysics Data System (ADS)
White, R. L.
The most widely used image restoration technique for optical astronomical data is the Richardson-Lucy (RL) iteration. The RL method is well-suited to optical and ultraviolet because it converges to the maximum likelihood solution for Poisson statistics in the data, which is appropriate for astronomical images taken with CCD or photon-counting detectors. Images restored using the RL iteration have good good photometric linearity and can be used for quantitative analysis, and typical RL restorations require a manageable amount of computer time. Despite its advantages, the RL method has some serious shortcomings. Noise amplification is a problem, as for all maximum likelihood techniques. If one performs many RL iterations on an image containing an extended object such as a galaxy, the extended emission develops a ``speckled'' appearance. The speckles are the result of fitting the noise in the data too closely. The only limit on the amount of noise amplification in the RL method is the requirement that the image not become negative. The usual practical approach to limiting noise amplification is simply to stop the iteration when the restored image appears to become too noisy. However, in most cases the number of iterations needed is different for different parts of the image. Hundreds of iterations may be required to get a good fit to the high signal-to-noise image of a bright star, while a smooth, extended object may be fitted well after only a few iterations. Thus, one would like to be able to slow or stop the iteration automatically in regions where a smooth model fits the data adequately, while continuing to iterate in regions where there are sharp features (edges or point sources). The need for a spatially adaptive convergence criterion is exacerbated when CCD readout noise is included in the RL algorithm (Snyder, Hammoud, & White, 1993, JOSA A , 10 , 1014), because the rate of convergence is then slower for faint stars than for bright stars. This paper will
A lower hybrid current drive system for ITER
NASA Astrophysics Data System (ADS)
Hoang, G. T.; Bécoulet, A.; Jacquinot, J.; Artaud, J. F.; Bae, Y. S.; Beaumont, B.; Belo, J. H.; Berger-By, G.; Bizarro, João P. S.; Bonoli, P.; Cho, M. H.; Decker, J.; Delpech, L.; Ekedahl, A.; Garcia, J.; Giruzzi, G.; Goniche, M.; Gormezano, C.; Guilhem, D.; Hillairet, J.; Imbeaux, F.; Kazarian, F.; Kessel, C.; Kim, S. H.; Kwak, J. G.; Jeong, J. H.; Lister, J. B.; Litaudon, X.; Magne, R.; Milora, S.; Mirizzi, F.; Namkung, W.; Noterdaeme, J. M.; Park, S. I.; Parker, R.; Peysson, Y.; Rasmussen, D.; Sharma, P. K.; Schneider, M.; Synakowski, E.; Tanga, A.; Tuccillo, A.; Wan, Y. X.
2009-07-01
A 20 MW/5 GHz lower hybrid current drive (LHCD) system was initially due to be commissioned and used for the second mission of ITER, i.e. the Q = 5 steady state target. Though not part of the currently planned procurement phase, it is now under consideration for an earlier delivery. In this paper, both physics and technology conceptual designs are reviewed. Furthermore, an appropriate work plan is also developed. This work plan for design, R&D, procurement and installation of a 20 MW LHCD system on ITER follows the ITER Scientific and Technical Advisory Committee (STAC) T13-05 task instructions. It gives more details on the various scientific and technical implications of the system, without presuming on any work or procurement sharing amongst the possible ITER partnersb The LHCD system of ITER is not part of the initial cost sharing.. This document does not commit the Institutions or Domestic Agencies of the various authors in that respect.
Preliminary consideration of CFETR ITER-like case diagnostic system
NASA Astrophysics Data System (ADS)
Li, G. S.; Yang, Y.; Wang, Y. M.; Ming, T. F.; Han, X.; Liu, S. C.; Wang, E. H.; Liu, Y. K.; Yang, W. J.; Li, G. Q.; Hu, Q. S.; Gao, X.
2016-11-01
Chinese Fusion Engineering Test Reactor (CFETR) is a new superconducting tokamak device being designed in China, which aims at bridging the gap between ITER and DEMO, where DEMO is a tokamak demonstration fusion reactor. Two diagnostic cases, ITER-like case and towards DEMO case, have been considered for CFETR early and later operating phases, respectively. In this paper, some preliminary consideration of ITER-like case will be presented. Based on ITER diagnostic system, three versions of increased complexity and coverage of the ITER-like case diagnostic system have been developed with different goals and functions. Version A aims only machine protection and basic control. Both of version B and version C are mainly for machine protection, basic and advanced control, but version C has an increased level of redundancy necessary for improved measurements capability. The performance of these versions and needed R&D work are outlined.
Final Report on ITER Task Agreement 81-10
Brad J. Merrill
2009-01-01
An International Thermonuclear Experimental Reactor (ITER) Implementing Task Agreement (ITA) on Magnet Safety was established between the ITER International Organization (IO) and the Idaho National Laboratory (INL) Fusion Safety Program (FSP) during calendar year 2004. The objectives of this ITA were to add new capabilities to the MAGARC code and to use this updated version of MAGARC to analyze unmitigated superconductor quench events for both poloidal field (PF) and toroidal field (TF) coils of the ITER design. This report documents the completion of the work scope for this ITA. Based on the results obtained for this ITA, an unmitigated quench event in an ITER larger PF coil does not appear to be as severe an accident as in an ITER TF coil.
Light shaping along 3D curves and particle manipulation
NASA Astrophysics Data System (ADS)
Rodrigo, José A.; Alieva, Tatiana
2015-03-01
We present a non-iterative holographic technique for efficient and versatile laser beam shaping along arbitrary 3D curves. Light beams with intensity shaped for several 3D curves: Tilted ring, Viviani's curve, Archimedean spiral, and trefoil-knotted curve have been experimentally generated and applied for optical trapping of micrometer-sized dielectric particles. The high intensity gradients and independent phase control prescribed along the curve make this kind of laser trap attractive for multiple particle manipulation and allow for forward and backward motion to the light source. Indeed, different configurations of tractor beam traps are experimentally demonstrated. This technique can also be applied for laser micro-machining.
Shape measurement of bubble in a liquid metal
NASA Astrophysics Data System (ADS)
Saito, Y.; Shen, X.; Mishima, K.; Matsubayashi, M.
2009-06-01
Dynamic behavior of a two-phase bubble, i.e. a steam bubble containing a droplet evaporating in the bubble, in the molten alloy was clearly visualized using high-frame-rate neutron radiography. In relation to some direct contact heat exchanger design with molten lead-bismuth (Pb-Bi), experiments have been done at JRR-3M of JAEA (Japan Atomic Energy Agency) with water droplets evaporating in a stable thermally stratified Newton's alloy pool. The instantaneous shape and size of the bubble has been iteratively estimated from the void fraction distributions and total void volume by assuming a symmetrical bubble shape.
Fetal Alcohol Spectrum Disorders
... alcohol can cause a group of conditions called fetal alcohol spectrum disorders (FASDs). Effects can include physical and behavioral problems such ... alcohol syndrome is the most serious type of FASD. People with fetal alcohol syndrome have facial abnormalities, ...
This video shows a line plot of the spectrum. The spectra here are shown for various locations on the Sun. The changes in the movie are caused by differing physical conditions in the locations. Cre...
Quantum Spread Spectrum Communication
Humble, Travis S
2010-01-01
We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.
Determination of Optimal Blank Shape by Radius Vector Method
NASA Astrophysics Data System (ADS)
Shim, Hyun Bo; Park, Jong Kyu; Kim, Yang Soo
2004-06-01
A new method of optimal blank shape design for stampings of arbitrary shapes has been proposed. Similar to the sensitivity method, a past work of the present author, the basic nature of this method is iterative modification of an undeformed blank shape by adjusting the nodal positions at the boundary of the blank, until the final shape satisfies a target shape. The main difference from the sensitivity method is that both shape error measure and blank shape modification is done along the normal to a boundary direction in the current method instead of nodal moving direction as in the sensitivity method. Even though the sensitivity method has been proven to be excellent through experiment, huge computational effort is still a problem since the method requires a couple of deformation process analyses per each design stage. Differently from the sensitivity method, the present radius vector method requires only a single deformation analysis per each design step and it can handle an extraordinary motion due to a rigid-body rotation during forming. Drawings of L-shaped cup and wheel housing have been chosen as the examples to verify the present method. In every cases the optimal blank shapes have been obtained after a few times of modification. Through the investigation, the present method, which incorporates normal to boundary is found to be an excellent, or better than the sensitivity method, which incorporates moving direction, for the optimal blank design.
Koenderink, Jan; van Doorn, Andrea
2015-01-01
Local solid shape applies to the surface curvature of small surface patches—essentially regions of approximately constant curvatures—of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution. PMID:27648217
Koenderink, Jan; van Doorn, Andrea
2015-01-01
Local solid shape applies to the surface curvature of small surface patches—essentially regions of approximately constant curvatures—of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution.
Koenderink, Jan; van Doorn, Andrea; Wagemans, Johan
2015-10-01
Local solid shape applies to the surface curvature of small surface patches-essentially regions of approximately constant curvatures-of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution. PMID:27648217
Eliminating Unpredictable Variation through Iterated Learning
ERIC Educational Resources Information Center
Smith, Kenny; Wonnacott, Elizabeth
2010-01-01
Human languages may be shaped not only by the (individual psychological) processes of language acquisition, but also by population-level processes arising from repeated language learning and use. One prevalent feature of natural languages is that they avoid unpredictable variation. The current work explores whether linguistic predictability might…
NASA Astrophysics Data System (ADS)
Murdin, P.
2000-11-01
In general terms, the distribution of intensity of electromagnetic radiation with wavelength. Thus when we examine the spectrum of star we are looking at a map of this brightness distribution. In the context of visible light, the visible spectrum is the band of colors produced when white light is passed through a glass prism, which has the effect of spreading out light according to wavelength. Fr...
Evaluating iterative reconstruction performance in computed tomography
Chen, Baiyu Solomon, Justin; Ramirez Giraldo, Juan Carlos; Samei, Ehsan
2014-12-15
Purpose: Iterative reconstruction (IR) offers notable advantages in computed tomography (CT). However, its performance characterization is complicated by its potentially nonlinear behavior, impacting performance in terms of specific tasks. This study aimed to evaluate the performance of IR with both task-specific and task-generic strategies. Methods: The performance of IR in CT was mathematically assessed with an observer model that predicted the detection accuracy in terms of the detectability index (d′). d′ was calculated based on the properties of the image noise and resolution, the observer, and the detection task. The characterizations of image noise and resolution were extended to accommodate the nonlinearity of IR. A library of tasks was mathematically modeled at a range of sizes (radius 1–4 mm), contrast levels (10–100 HU), and edge profiles (sharp and soft). Unique d′ values were calculated for each task with respect to five radiation exposure levels (volume CT dose index, CTDI{sub vol}: 3.4–64.8 mGy) and four reconstruction algorithms (filtered backprojection reconstruction, FBP; iterative reconstruction in imaging space, IRIS; and sinogram affirmed iterative reconstruction with strengths of 3 and 5, SAFIRE3 and SAFIRE5; all provided by Siemens Healthcare, Forchheim, Germany). The d′ values were translated into the areas under the receiver operating characteristic curve (AUC) to represent human observer performance. For each task and reconstruction algorithm, a threshold dose was derived as the minimum dose required to achieve a threshold AUC of 0.9. A task-specific dose reduction potential of IR was calculated as the difference between the threshold doses for IR and FBP. A task-generic comparison was further made between IR and FBP in terms of the percent of all tasks yielding an AUC higher than the threshold. Results: IR required less dose than FBP to achieve the threshold AUC. In general, SAFIRE5 showed the most significant dose reduction
General shape optimization capability
NASA Technical Reports Server (NTRS)
Chargin, Mladen K.; Raasch, Ingo; Bruns, Rudolf; Deuermeyer, Dawson
1991-01-01
A method is described for calculating shape sensitivities, within MSC/NASTRAN, in a simple manner without resort to external programs. The method uses natural design variables to define the shape changes in a given structure. Once the shape sensitivities are obtained, the shape optimization process is carried out in a manner similar to property optimization processes. The capability of this method is illustrated by two examples: the shape optimization of a cantilever beam with holes, loaded by a point load at the free end (with the shape of the holes and the thickness of the beam selected as the design variables), and the shape optimization of a connecting rod subjected to several different loading and boundary conditions.
A hierarchical Krylov-Bayes iterative inverse solver for MEG with physiological preconditioning
NASA Astrophysics Data System (ADS)
Calvetti, D.; Pascarella, A.; Pitolli, F.; Somersalo, E.; Vantaggi, B.
2015-12-01
The inverse problem of MEG aims at estimating electromagnetic cerebral activity from measurements of the magnetic fields outside the head. After formulating the problem within the Bayesian framework, a hierarchical conditionally Gaussian prior model is introduced, including a physiologically inspired prior model that takes into account the preferred directions of the source currents. The hyperparameter vector consists of prior variances of the dipole moments, assumed to follow a non-conjugate gamma distribution with variable scaling and shape parameters. A point estimate of both dipole moments and their variances can be computed using an iterative alternating sequential updating algorithm, which is shown to be globally convergent. The numerical solution is based on computing an approximation of the dipole moments using a Krylov subspace iterative linear solver equipped with statistically inspired preconditioning and a suitable termination rule. The shape parameters of the model are shown to control the focality, and furthermore, using an empirical Bayes argument, it is shown that the scaling parameters can be naturally adjusted to provide a statistically well justified depth sensitivity scaling. The validity of this interpretation is verified through computed numerical examples. Also, a computed example showing the applicability of the algorithm to analyze realistic time series data is presented.
Segmentation of the lumbar spine with knowledge-based shape models
NASA Astrophysics Data System (ADS)
Kohnen, Michael; Mahnken, Andreas H.; Brandt, Alexander S.; Steinberg, Stephan; Guenther, Rolf W.; Wein, Berthold B.
2002-05-01
A shape model for full automatic segmentation and recognition of lateral lumbar spine radiographs has been developed. The shape model is able to learn the shape variations from a training dataset by a principal component analysis of the shape information. Furthermore, specific image features at each contour point are added into models of gray value profiles. These models were computed from a training dataset consisting of 25 manually segmented lumbar spines. The application of the model containing both shape and image information is optimized on unknown images using a simulated annealing search first to acquire a coarse localization of the model. Further on, the shape points are iteratively moved towards image structures matching the gray value models. During optimization the shape information of the model assures that the segmented object boundary stays plausible. The shape model was tested on 65 unknown images achieving a mean segmentation accuracy of 88% measured from the percental cover of the resulting and manually drawn contours.
Iterative and variational homogenization methods for filled elastomers
NASA Astrophysics Data System (ADS)
Goudarzi, Taha
Elastomeric composites have increasingly proved invaluable in commercial technological applications due to their unique mechanical properties, especially their ability to undergo large reversible deformation in response to a variety of stimuli (e.g., mechanical forces, electric and magnetic fields, changes in temperature). Modern advances in organic materials science have revealed that elastomeric composites hold also tremendous potential to enable new high-end technologies, especially as the next generation of sensors and actuators featured by their low cost together with their biocompatibility, and processability into arbitrary shapes. This potential calls for an in-depth investigation of the macroscopic mechanical/physical behavior of elastomeric composites directly in terms of their microscopic behavior with the objective of creating the knowledge base needed to guide their bottom-up design. The purpose of this thesis is to generate a mathematical framework to describe, explain, and predict the macroscopic nonlinear elastic behavior of filled elastomers, arguably the most prominent class of elastomeric composites, directly in terms of the behavior of their constituents --- i.e., the elastomeric matrix and the filler particles --- and their microstructure --- i.e., the content, size, shape, and spatial distribution of the filler particles. This will be accomplished via a combination of novel iterative and variational homogenization techniques capable of accounting for interphasial phenomena and finite deformations. Exact and approximate analytical solutions for the fundamental nonlinear elastic response of dilute suspensions of rigid spherical particles (either firmly bonded or bonded through finite size interphases) in Gaussian rubber are first generated. These results are in turn utilized to construct approximate solutions for the nonlinear elastic response of non-Gaussian elastomers filled with a random distribution of rigid particles (again, either firmly
Electron cyclotron emission diagnostic for ITER
Rowan, W.; Austin, M.; Phillips, P.; Beno, J.; Ouroua, A.; Ellis, R.; Feder, R.; Patel, A.
2010-10-15
Electron temperature measurements and electron thermal transport inferences will be critical to the nonactive and deuterium phases of ITER operation and will take on added importance during the alpha heating phase. The diagnostic must meet stringent criteria on spatial coverage and spatial resolution during full field operation. During the early phases of operation, it must operate equally well at half field. The key to the diagnostic is the front end design. It consists of a quasioptical antenna and a pair of calibration sources. The radial resolution of the diagnostic is less than 0.06 m. The spatial coverage extends at least from the core to the separatrix with first harmonic O-mode being used for the core and second harmonic X-mode being used for the pedestal. The instrumentation used for the core measurement at full field can be used for detection at half field by changing the detected polarization. Intermediate fields are accessible. The electron cyclotron emission systems require in situ calibration, which is provided by a novel hot calibration source. The critical component for the hot calibration source, the emissive surface, has been successfully tested. A prototype hot calibration source has been designed, making use of extensive thermal and mechanical modeling.
Electron cyclotron emission diagnostic for ITER.
Rowan, W; Austin, M; Beno, J; Ellis, R; Feder, R; Ouroua, A; Patel, A; Phillips, P
2010-10-01
Electron temperature measurements and electron thermal transport inferences will be critical to the nonactive and deuterium phases of ITER operation and will take on added importance during the alpha heating phase. The diagnostic must meet stringent criteria on spatial coverage and spatial resolution during full field operation. During the early phases of operation, it must operate equally well at half field. The key to the diagnostic is the front end design. It consists of a quasioptical antenna and a pair of calibration sources. The radial resolution of the diagnostic is less than 0.06 m. The spatial coverage extends at least from the core to the separatrix with first harmonic O-mode being used for the core and second harmonic X-mode being used for the pedestal. The instrumentation used for the core measurement at full field can be used for detection at half field by changing the detected polarization. Intermediate fields are accessible. The electron cyclotron emission systems require in situ calibration, which is provided by a novel hot calibration source. The critical component for the hot calibration source, the emissive surface, has been successfully tested. A prototype hot calibration source has been designed, making use of extensive thermal and mechanical modeling.
Iterated conformal dynamics and Laplacian growth.
Barra, Felipe; Davidovitch, Benny; Procaccia, Itamar
2002-04-01
The method of iterated conformal maps for the study of diffusion limited aggregates (DLA) is generalized to the study of Laplacian growth patterns and related processes. We emphasize the fundamental difference between these processes: DLA is grown serially with constant size particles, while Laplacian patterns are grown by advancing each boundary point in parallel, proportional to the gradient of the Laplacian field. We introduce a two-parameter family of growth patterns that interpolates between DLA and a discrete version of Laplacian growth. The ultraviolet putative finite-time singularities are regularized here by a minimal tip size, equivalently for all the models in this family. With this we stress that the difference between DLA and Laplacian growth is not in the manner of ultraviolet regularization, but rather in their deeply different growth rules. The fractal dimensions of the asymptotic patterns depend continuously on the two parameters of the family, giving rise to a "phase diagram" in which DLA and discretized Laplacian growth are at the extreme ends. In particular, we show that the fractal dimension of Laplacian growth patterns is higher than the fractal dimension of DLA, with the possibility of dimension 2 for the former not excluded. PMID:12005963
Sequence analysis by iterated maps, a review.
Almeida, Jonas S
2014-05-01
Among alignment-free methods, Iterated Maps (IMs) are on a particular extreme: they are also scale free (order free). The use of IMs for sequence analysis is also distinct from other alignment-free methodologies in being rooted in statistical mechanics instead of computational linguistics. Both of these roots go back over two decades to the use of fractal geometry in the characterization of phase-space representations. The time series analysis origin of the field is betrayed by the title of the manuscript that started this alignment-free subdomain in 1990, 'Chaos Game Representation'. The clash between the analysis of sequences as continuous series and the better established use of Markovian approaches to discrete series was almost immediate, with a defining critique published in same journal 2 years later. The rest of that decade would go by before the scale-free nature of the IM space was uncovered. The ensuing decade saw this scalability generalized for non-genomic alphabets as well as an interest in its use for graphic representation of biological sequences. Finally, in the past couple of years, in step with the emergence of BigData and MapReduce as a new computational paradigm, there is a surprising third act in the IM story. Multiple reports have described gains in computational efficiency of multiple orders of magnitude over more conventional sequence analysis methodologies. The stage appears to be now set for a recasting of IMs with a central role in processing nextgen sequencing results.
SPECIAL TOPIC: ITER L mode confinement database
NASA Astrophysics Data System (ADS)
Kaye, S. M.; Greenwald, M.; Stroth, U.; Kardaun, O.; Kus, A.; Schissel, D.; DeBoo, J.; Bracco, G.; Thomsen, K.; Cordey, J. G.; Miura, Y.; Matsuda, T.; Tamai, H.; Takizuda, T.; Hirayama, T.; Kikuchi, H.; Naito, O.; Chudnovskij, A.; Ongena, J.; Hoang, G.
1997-09-01
This special topic describes the contents of an L mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR and Tore Supra. The database consists of a total of 2938 entries, 1881 of which are in the L phase while 922 are ohmically heated only (ohmic). Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning and configuration. The special topic presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER. The L mode thermal confinement time scaling, determined from a subset of 1312 entries for which the τE,th are provided, is τE,th = 0.023Ip0.96BT0.03R1.83(R/a)0.06 κ0.64ne0.40Meff0.20P-0.73 in units of seconds, megamps, teslas, metres, -, -, 10-9 m-1
Sequence analysis by iterated maps, a review.
Almeida, Jonas S
2014-05-01
Among alignment-free methods, Iterated Maps (IMs) are on a particular extreme: they are also scale free (order free). The use of IMs for sequence analysis is also distinct from other alignment-free methodologies in being rooted in statistical mechanics instead of computational linguistics. Both of these roots go back over two decades to the use of fractal geometry in the characterization of phase-space representations. The time series analysis origin of the field is betrayed by the title of the manuscript that started this alignment-free subdomain in 1990, 'Chaos Game Representation'. The clash between the analysis of sequences as continuous series and the better established use of Markovian approaches to discrete series was almost immediate, with a defining critique published in same journal 2 years later. The rest of that decade would go by before the scale-free nature of the IM space was uncovered. The ensuing decade saw this scalability generalized for non-genomic alphabets as well as an interest in its use for graphic representation of biological sequences. Finally, in the past couple of years, in step with the emergence of BigData and MapReduce as a new computational paradigm, there is a surprising third act in the IM story. Multiple reports have described gains in computational efficiency of multiple orders of magnitude over more conventional sequence analysis methodologies. The stage appears to be now set for a recasting of IMs with a central role in processing nextgen sequencing results. PMID:24162172
Mixed Confidence Estimation for Iterative CT Reconstruction.
Perlmutter, David S; Kim, Soo Mee; Kinahan, Paul E; Alessio, Adam M
2016-09-01
Dynamic (4D) CT imaging is used in a variety of applications, but the two major drawbacks of the technique are its increased radiation dose and longer reconstruction time. Here we present a statistical analysis of our previously proposed Mixed Confidence Estimation (MCE) method that addresses both these issues. This method, where framed iterative reconstruction is only performed on the dynamic regions of each frame while static regions are fixed across frames to a composite image, was proposed to reduce computation time. In this work, we generalize the previous method to describe any application where a portion of the image is known with higher confidence (static, composite, lower-frequency content, etc.) and a portion of the image is known with lower confidence (dynamic, targeted, etc). We show that by splitting the image space into higher and lower confidence components, MCE can lower the estimator variance in both regions compared to conventional reconstruction. We present a theoretical argument for this reduction in estimator variance and verify this argument with proof-of-principle simulations. We also propose a fast approximation of the variance of images reconstructed with MCE and confirm that this approximation is accurate compared to analytic calculations of and multi-realization image variance. This MCE method requires less computation time and provides reduced image variance for imaging scenarios where portions of the image are known with more certainty than others allowing for potentially reduced radiation dose and/or improved dynamic imaging. PMID:27008663
On different results for new three step iteration process in Banach spaces.
Ullah, Kifayat; Arshad, Muhammad
2016-01-01
In this paper we propose a new iteration process, called AK iteration process, for approximation of fixed points for contraction mappings. We show that our iteration process is faster than the leading Vatan Two-step iteration process for contraction mappings. Numerical examples are given to support the analytic proofs. Stability of AK iteration process and data dependence result for contraction mappings by employing AK iteration process are also discussed. PMID:27652189
On different results for new three step iteration process in Banach spaces.
Ullah, Kifayat; Arshad, Muhammad
2016-01-01
In this paper we propose a new iteration process, called AK iteration process, for approximation of fixed points for contraction mappings. We show that our iteration process is faster than the leading Vatan Two-step iteration process for contraction mappings. Numerical examples are given to support the analytic proofs. Stability of AK iteration process and data dependence result for contraction mappings by employing AK iteration process are also discussed.
Mission of ITER and Challenges for the Young
Ikeda, Kaname
2009-02-19
It is recognized that the ongoing effort to provide sufficient energy for the wellbeing of the globe's population and to power the world economy is of the greatest importance. ITER is a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power. It represents the responsible actions of governments whose countries comprise over half the world's population, to create fusion power as a source of clean, economic, carbon dioxide-free energy. This is the most important science initiative of our time.The partners in the Project--the ITER Parties--are the European Union, Japan, the People's Republic of China, India, the Republic of Korea, the Russian Federation and the USA. ITER will be constructed in Europe, at Cadarache in the South of France. The talk will illustrate the genesis of the ITER Organization, the ongoing work at the Cadarache site and the planned schedule for construction. There will also be an explanation of the unique aspects of international collaboration that have been developed for ITER.Although the present focus of the project is construction activities, ITER is also a major scientific and technological research program, for which the best of the world's intellectual resources is needed. Challenges for the young, imperative for fulfillment of the objective of ITER will be identified. It is important that young students and researchers worldwide recognize the rapid development of the project, and the fundamental issues that must be overcome in ITER.The talk will also cover the exciting career and fellowship opportunities for young people at the ITER Organization.
Mission of ITER and Challenges for the Young
NASA Astrophysics Data System (ADS)
Ikeda, Kaname
2009-02-01
It is recognized that the ongoing effort to provide sufficient energy for the wellbeing of the globe's population and to power the world economy is of the greatest importance. ITER is a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power. It represents the responsible actions of governments whose countries comprise over half the world's population, to create fusion power as a source of clean, economic, carbon dioxide-free energy. This is the most important science initiative of our time. The partners in the Project—the ITER Parties—are the European Union, Japan, the People's Republic of China, India, the Republic of Korea, the Russian Federation and the USA. ITER will be constructed in Europe, at Cadarache in the South of France. The talk will illustrate the genesis of the ITER Organization, the ongoing work at the Cadarache site and the planned schedule for construction. There will also be an explanation of the unique aspects of international collaboration that have been developed for ITER. Although the present focus of the project is construction activities, ITER is also a major scientific and technological research program, for which the best of the world's intellectual resources is needed. Challenges for the young, imperative for fulfillment of the objective of ITER will be identified. It is important that young students and researchers worldwide recognize the rapid development of the project, and the fundamental issues that must be overcome in ITER. The talk will also cover the exciting career and fellowship opportunities for young people at the ITER Organization.
Thorman, A; Michael, C; De Bock, M; Howard, J
2016-07-01
A motional Stark effect polarimeter insensitive to polarized broadband light is proposed. Partially polarized background light is anticipated to be a significant source of systematic error for the ITER polarimeter. The proposed polarimeter is based on the standard dual photoelastic modulator approach, but with the introduction of a birefringent delay plate, it generates a sinusoidal spectral filter instead of the usual narrowband filter. The period of the filter is chosen to match the spacing of the orthogonally polarized Stark effect components, thereby increasing the effective signal level, but resulting in the destructive interference of the broadband polarized light. The theoretical response of the system to an ITER like spectrum is calculated and the broadband polarization tolerance is verified experimentally.
NASA Astrophysics Data System (ADS)
Thorman, A.; Michael, C.; De Bock, M.; Howard, J.
2016-07-01
A motional Stark effect polarimeter insensitive to polarized broadband light is proposed. Partially polarized background light is anticipated to be a significant source of systematic error for the ITER polarimeter. The proposed polarimeter is based on the standard dual photoelastic modulator approach, but with the introduction of a birefringent delay plate, it generates a sinusoidal spectral filter instead of the usual narrowband filter. The period of the filter is chosen to match the spacing of the orthogonally polarized Stark effect components, thereby increasing the effective signal level, but resulting in the destructive interference of the broadband polarized light. The theoretical response of the system to an ITER like spectrum is calculated and the broadband polarization tolerance is verified experimentally.
SUMMARY REPORT-FY2006 ITER WORK ACCOMPLISHED
Martovetsky, N N
2006-04-11
Six parties (EU, Japan, Russia, US, Korea, China) will build ITER. The US proposed to deliver at least 4 out of 7 modules of the Central Solenoid. Phillip Michael (MIT) and I were tasked by DoE to assist ITER in development of the ITER CS and other magnet systems. We work to help Magnets and Structure division headed by Neil Mitchell. During this visit I worked on the selected items of the CS design and carried out other small tasks, like PF temperature margin assessment.
Perturbation-iteration theory for analyzing microwave striplines
NASA Technical Reports Server (NTRS)
Kretch, B. E.
1985-01-01
A perturbation-iteration technique is presented for determining the propagation constant and characteristic impedance of an unshielded microstrip transmission line. The method converges to the correct solution with a few iterations at each frequency and is equivalent to a full wave analysis. The perturbation-iteration method gives a direct solution for the propagation constant without having to find the roots of a transcendental dispersion equation. The theory is presented in detail along with numerical results for the effective dielectric constant and characteristic impedance for a wide range of substrate dielectric constants, stripline dimensions, and frequencies.
Qualification tests and facilities for the ITER superconductors
NASA Astrophysics Data System (ADS)
Bruzzone, P.; Wesche, R.; Stepanov, B.; Cau, F.; Bagnasco, M.; Calvi, M.; Herzog, R.; Vogel, M.
2009-06-01
All the ITER superconductors are tested as short length samples in the SULTAN test facility at CRPP. Twenty-four TF conductor samples with small layout variations were tested since February 2007 with the aim of verifying the design and qualification of the manufacturers. The sample assembly and the measurement techniques at CRPP are discussed. Starting in 2010, another test facility for ITER conductors, named EDIPO, will be operating at CRPP to share with SULTAN the load of the samples for the acceptance tests during the construction of ITER.
Iterative method for elliptic problems on regions partitioned into substructures
Bramble, J.H.; Pasciak, J.E.; Schatz, A.H.
1986-04-01
Some new preconditioners for discretizations of elliptic boundary problems are studied. With these preconditioners, the domain under consideration is broken into subdomains and preconditioners are defined which only require the solution of matrix problems on the subdomains. Analytic estimates are given which guarantee that under appropriate hypotheses, the preconditioned iterative procedure converges to the solution of the discrete equations with a rate per iteration that is independent of the number of unknowns. Numerical examples are presented which illustrate the theoretically predicted iterative convergence rates.
Iterative schemes for nonsymmetric and indefinite elliptic boundary value problems
Bramble, J.H.; Leyk, Z.; Pasciak, J.E.
1993-01-01
The purpose of this paper is twofold. The first is to describe some simple and robust iterative schemes for nonsymmetric and indefinite elliptic boundary value problems. The schemes are based in the Sobolev space H ([Omega]) and require minimal hypotheses. The second is to develop algorithms utilizing a coarse-grid approximation. This leads to iteration matrices whose eigenvalues lie in the right half of the complex plane. In fact, for symmetric indefinite problems, the iteration is reduced to a well-conditioned symmetric positive definite system which can be solved by conjugate gradient interation. Applications of the general theory as well as numerical examples are given. 20 refs., 8 tabs.
Shattered Pellet Disruption Mitigation Technology Development for ITER
Baylor, Larry R; Combs, Stephen Kirk; Jernigan, T. C.; Meitner, Steven J; Edgemon, Timothy D; Parks, P. B.; Commaux, Nicolas JC; Maruyama, S.; Caughman, John B; Rasmussen, David A
2010-01-01
The mitigation of first wall thermal and mechanical loads and damage from runaway electrons during disruptions are critical for successful long term operation of ITER. Disruption mitigation tools based on shattered pellet injection are being developed at Oak Ridge National Laboratory that can be employed on ITER to provide the necessary mitigation of thermal and mechanical loads from disruptions as well as provide collisional damping to inhibit the formation of runaway electrons . Here we present progress on the development of the technology to provide reliable disruption mitigation with large shattered cryogenic pellets. An example of how this concept can be employed on ITER is discussed.
Disruptions in ITER and strategies for their control and mitigation
NASA Astrophysics Data System (ADS)
Lehnen, M.; Aleynikova, K.; Aleynikov, P. B.; Campbell, D. J.; Drewelow, P.; Eidietis, N. W.; Gasparyan, Yu.; Granetz, R. S.; Gribov, Y.; Hartmann, N.; Hollmann, E. M.; Izzo, V. A.; Jachmich, S.; Kim, S.-H.; Kočan, M.; Koslowski, H. R.; Kovalenko, D.; Kruezi, U.; Loarte, A.; Maruyama, S.; Matthews, G. F.; Parks, P. B.; Pautasso, G.; Pitts, R. A.; Reux, C.; Riccardo, V.; Roccella, R.; Snipes, J. A.; Thornton, A. J.; de Vries, P. C.
2015-08-01
The thermal and electromagnetic loads related to disruptions in ITER are substantial and require careful design of tokamak components to ensure they reach the projected lifetime and to ensure that safety relevant components fulfil their function for the worst foreseen scenarios. The disruption load specifications are the basis for the design process of components like the full-W divertor, the blanket modules and the vacuum vessel and will set the boundary conditions for ITER operations. This paper will give a brief overview on the disruption loads and mitigation strategies for ITER and will discuss the physics basis which is continuously refined through the current disruption R&D programs.
Conference on iterative methods for large linear systems
Kincaid, D.R.
1988-12-01
This conference is dedicated to providing an overview of the state of the art in the use of iterative methods for solving sparse linear systems with an eye to contributions of the past, present and future. The emphasis is on identifying current and future research directions in the mainstream of modern scientific computing. Recently, the use of iterative methods for solving linear systems has experienced a resurgence of activity as scientists attach extremely complicated three-dimensional problems using vector and parallel supercomputers. Many research advances in the development of iterative methods for high-speed computers over the past forty years are reviewed, as well as focusing on current research.
NASA Astrophysics Data System (ADS)
Kallus, Yoav
2014-03-01
The question of which convex shapes leave the most empty space in their densest packing is the subject of Reinhardt's conjecture in two dimensions and Ulam's conjecture in three dimensions. Such conjectures about pessimal packing shapes have proven notoriously difficult to make progress on. I show that the regular heptagon is a local pessimum among all convex shapes, and that the 3D ball is a local pessimum among origin-symmetric shapes. Any shape sufficiently close in the space of shapes to these local pessima can be packed at a greater efficiency than they. In two dimensions and in dimensions above three, the ball is not a local pessimum, so the situation in 3D is unusual and intriguing. I will discuss what conditions conspire to make the 3D ball a local pessimum and whether we can prove that it is also a global pessimum.
Micro acoustic spectrum analyzer
Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.
2004-11-23
A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.
NASA Technical Reports Server (NTRS)
Thomas, P. C.; Dermott, S. F.
1991-01-01
After considering the most important relationships between density, rotation rate, shape, and internal structure on the basis of equilibrium figures, the shape of the Saturn satellite Tethys is established from limb-coordinate data. Attention is given to the shape's significance for Tethys' internal structure. It is alternatively concluded that Tethys is either differentiated, and possesses a small rocky core, or has been interpreted as possessing a mass that is too low by about 15 percent.
NASA Technical Reports Server (NTRS)
2000-01-01
Looking at a few pictures of Eros under the right lighting conditions gives a reasonable idea of the shape of the asteroid, but analysis of NEAR Shoemaker data requires a very accurate digital model of Eros' shape. This 'shape model' helps the NEAR team analyze images and other types of data. For example, comparing the brightness of imaged regions with the orientation of the corresponding parts of the surface, taken from the shape model, allows scientists to determine whether bright areas are due to just surface orientation or also to surface properties. By 'filling
NASA Astrophysics Data System (ADS)
Ouaknin, Gaddiel; Laachi, Nabil; Delaney, Kris; Fredrickson, Glenn; Gibou, Frederic
2016-03-01
Directed self-assembly using block copolymers for positioning vertical interconnect access in integrated circuits relies on the proper shape of a confined domain in which polymers will self-assemble into the targeted design. Finding that shape, i.e., solving the inverse problem, is currently mainly based on trial and error approaches. We introduce a level-set based algorithm that makes use of a shape optimization strategy coupled with self-consistent field theory to solve the inverse problem in an automated way. It is shown that optimal shapes are found for different targeted topologies with accurate placement and distances between the different components.
DISJUNCTIVE NORMAL SHAPE MODELS
Ramesh, Nisha; Mesadi, Fitsum; Cetin, Mujdat; Tasdizen, Tolga
2016-01-01
A novel implicit parametric shape model is proposed for segmentation and analysis of medical images. Functions representing the shape of an object can be approximated as a union of N polytopes. Each polytope is obtained by the intersection of M half-spaces. The shape function can be approximated as a disjunction of conjunctions, using the disjunctive normal form. The shape model is initialized using seed points defined by the user. We define a cost function based on the Chan-Vese energy functional. The model is differentiable, hence, gradient based optimization algorithms are used to find the model parameters. PMID:27403233
Walukiewicz, Wladyslaw; Yu, Kin Man; Wu, Junqiao; Schaff, William J.
2007-05-15
An alloy having a large band gap range is used in a multijunction solar cell to enhance utilization of the solar energy spectrum. In one embodiment, the alloy is In.sub.1-xGa.sub.xN having an energy bandgap range of approximately 0.7 eV to 3.4 eV, providing a good match to the solar energy spectrum. Multiple junctions having different bandgaps are stacked to form a solar cell. Each junction may have different bandgaps (realized by varying the alloy composition), and therefore be responsive to different parts of the spectrum. The junctions are stacked in such a manner that some bands of light pass through upper junctions to lower junctions that are responsive to such bands.
The energy spectrum of ultra high energy cosmic rays
NASA Astrophysics Data System (ADS)
Abuzayyad, Tareq Ziad
2000-11-01
The Energy Spectrum of Ultra High Energy Cosmic Rays is measured by the first of two High Resolution Fly's Eye detectors in the monocular mode. The data set collected in the period of May 1997 to June 1999 was used for the measurement. A new reconstruction procedure (profile constrained geometry fit) was developed to analyze the data. This procedure gives reasonably good energy resolution, but poor xmax resolution. Resolution and systematics are discussed in the thesis. The spectrum measurement results are consistent with previous measurements in normalization and general shape. The spectrum appears to continue beyond the Greisen-Zatsepin-Kuz'min cutoff.
Impact of quantum entanglement on spectrum of cosmological fluctuations
Kanno, Sugumi
2014-07-01
We investigate the effect of entanglement between two causally separated open charts in de Sitter space on the spectrum of vacuum fluctuations. We consider a free massive scalar field, and construct the reduced density matrix by tracing out the vacuum state for one of the open charts, as recently derived by Maldacena and Pimentel. We formulate the mean-square vacuum fluctuations by using the reduced density matrix and show that the scale invariant spectrum of massless scalar field is realized on small scales. On the other hand, we find that the quantum entanglement affects the shape of the spectrum on large scales comparable to or greater than the curvature radius.
Shapes of binary asteroid primaries from photometric observations
NASA Astrophysics Data System (ADS)
Scheirich, Peter
2016-10-01
I will present results from a method which combine lightcurve inversion for single bodies and the method for inversion of lightcurves of occulting/eclipsing binary systems. A code developed by M. Kaasalainen and J. Durech for inversion of lightcurves of single bodies is adapted to fit our purposes. The original code uses a slightly elongated ellipsoid as an initial shape for optimization. We substituted this ellipsoid with a variety of shapes using Gaussian random spheres. This allowed the optimization algorithm to iterate to a range of final shapes.For each binary system, the short-period (rotational) component of its lightcurve is inverted using this code and a set of possible shapes of the primary are obtained. In the next step these shape models of the primary are, one by one, incorporated into the full model of the binary system and complete photometric data including the mutual events are fitted. Comparing synthetic lightcurves of the best-fit solutions with the observed data enables another narrowing of the selection of the possible shapes of the primary. This process is based on the times of phases of mutual events occurring on different geometries (i.e. the secondary passing in front of/behind the primary not only equator-on).We will also test a hypothesis that most of the primaries of the binary systems are similar in shape to each other. A figure resembling the shape of the primary of 1999 KW4, i.e., the top-shaped object with an equatorial ridge, will be used for the primary's shape. Its main characteristics – a polar flattening and width and height of the equatorial ridge, will be used as independent parameters. A variety of the shapes generated by a combination of these parameters will be used as an initial shapes for the optimization using the code described above.The work is supported by the Grant Agency of the Czech Republic, Grant 15-07193S.
Electrostatic Dust Detection and Removal for ITER
C.H. Skinner; A. Campos; H. Kugel; J. Leisure; A.L. Roquemore; S. Wagner
2008-09-01
We present some recent results on two innovative applications of microelectronics technology to dust inventory measurement and dust removal in ITER. A novel device to detect the settling of dust particles on a remote surface has been developed in the laboratory. A circuit board with a grid of two interlocking conductive traces with 25 μm spacing is biased to 30 – 50 V. Carbon particles landing on the energized grid create a transient short circuit. The current flowing through the short circuit creates a voltage pulse that is recorded by standard nuclear counting electronics and the total number of counts is related to the mass of dust impinging on the grid. The particles typically vaporize in a few seconds restoring the previous voltage standoff. Experience on NSTX however, showed that in a tokamak environment it was still possible for large particles or fibers to remain on the grid causing a long term short circuit. We report on the development of a gas puff system that uses helium to clear such particles. Experiments with varying nozzle designs, backing pressures, puff durations, and exit flow orientations have given an optimal configuration that effectively removes particles from an area up to 25 cm² with a single nozzle. In a separate experiment we are developing an advanced circuit grid of three interlocking traces that can generate a miniature electrostatic traveling wave for transporting dust to a suitable exit port. We have fabricated such a 3-pole circuit board with 25 micron insulated traces that operates with voltages up to 200 V. Recent results showed motion of dust particles with the application of only 50 V bias voltage. Such a device could potentially remove dust continuously without dedicated interventions and without loss of machine availability for plasma operations.
Sequence analysis by iterated maps, a review
2014-01-01
Among alignment-free methods, Iterated Maps (IMs) are on a particular extreme: they are also scale free (order free). The use of IMs for sequence analysis is also distinct from other alignment-free methodologies in being rooted in statistical mechanics instead of computational linguistics. Both of these roots go back over two decades to the use of fractal geometry in the characterization of phase-space representations. The time series analysis origin of the field is betrayed by the title of the manuscript that started this alignment-free subdomain in 1990, ‘Chaos Game Representation’. The clash between the analysis of sequences as continuous series and the better established use of Markovian approaches to discrete series was almost immediate, with a defining critique published in same journal 2 years later. The rest of that decade would go by before the scale-free nature of the IM space was uncovered. The ensuing decade saw this scalability generalized for non-genomic alphabets as well as an interest in its use for graphic representation of biological sequences. Finally, in the past couple of years, in step with the emergence of BigData and MapReduce as a new computational paradigm, there is a surprising third act in the IM story. Multiple reports have described gains in computational efficiency of multiple orders of magnitude over more conventional sequence analysis methodologies. The stage appears to be now set for a recasting of IMs with a central role in processing nextgen sequencing results. PMID:24162172
An iterative method for indefinite systems of linear equations
NASA Technical Reports Server (NTRS)
Ito, K.
1984-01-01
An iterative method for solving nonsymmetric indefinite linear systems is proposed. The method involves the successive use of a modified version of the conjugate residual method. A numerical example is given to illustrate the method.
Multi-Level iterative methods in computational plasma physics
Knoll, D.A.; Barnes, D.C.; Brackbill, J.U.; Chacon, L.; Lapenta, G.
1999-03-01
Plasma physics phenomena occur on a wide range of spatial scales and on a wide range of time scales. When attempting to model plasma physics problems numerically the authors are inevitably faced with the need for both fine spatial resolution (fine grids) and implicit time integration methods. Fine grids can tax the efficiency of iterative methods and large time steps can challenge the robustness of iterative methods. To meet these challenges they are developing a hybrid approach where multigrid methods are used as preconditioners to Krylov subspace based iterative methods such as conjugate gradients or GMRES. For nonlinear problems they apply multigrid preconditioning to a matrix-few Newton-GMRES method. Results are presented for application of these multilevel iterative methods to the field solves in implicit moment method PIC, multidimensional nonlinear Fokker-Planck problems, and their initial efforts in particle MHD.
Design standard issues for ITER in-vessel components
Majumdar, S.
1994-06-01
Unique requirements that must be addressed by a structural design code for the ITER have been summarized. Existing codes such as ASME Section III, or the French RCC-MR were developed primarily for fission reactor out-of-core components and are not directly applicable to the ITER. They may be used either as a guide for developing a design code for the ITER or as interim standards. However, new rules will be needed for handling the irradiation-induced embrittlement problems faced by the ITER blanket components. Design standards developed in the past for the design of fission reactor core components in the United States can be used as guides in this area.
Leapfrog variants of iterative methods for linear algebra equations
NASA Technical Reports Server (NTRS)
Saylor, Paul E.
1988-01-01
Two iterative methods are considered, Richardson's method and a general second order method. For both methods, a variant of the method is derived for which only even numbered iterates are computed. The variant is called a leapfrog method. Comparisons between the conventional form of the methods and the leapfrog form are made under the assumption that the number of unknowns is large. In the case of Richardson's method, it is possible to express the final iterate in terms of only the initial approximation, a variant of the iteration called the grand-leap method. In the case of the grand-leap variant, a set of parameters is required. An algorithm is presented to compute these parameters that is related to algorithms to compute the weights and abscissas for Gaussian quadrature. General algorithms to implement the leapfrog and grand-leap methods are presented. Algorithms for the important special case of the Chebyshev method are also given.
Iterative methods for elliptic finite element equations on general meshes
NASA Technical Reports Server (NTRS)
Nicolaides, R. A.; Choudhury, Shenaz
1986-01-01
Iterative methods for arbitrary mesh discretizations of elliptic partial differential equations are surveyed. The methods discussed are preconditioned conjugate gradients, algebraic multigrid, deflated conjugate gradients, an element-by-element techniques, and domain decomposition. Computational results are included.
Final Report on ITER Task Agreement 81-18
Brad J. Merrill
2008-02-01
During 2007, the US International Thermonuclear Experimental Reactor (ITER) Project Office (USIPO) entered into a Task Agreement (TA) with the ITER International Organization (IO) to conduct Research and Development activity and/or Design activity in the area of Safety Analyses. There were four tasks within this TA, which were to provide the ITER IO with: 1) Quality Assurance (QA) documentation for the MELCOR 1.8.2 Fusion code, 2) a pedigreed version of MELCOR 1.8.2, 3) assistance in MELCOR input deck development and accident analyses, and 4) support and assistance in the operation of the MELCOR 1.8.2. This report, which is the final report for this agreement, documents the completion of the work scope under this ITER TA, designated as TA 81-18.
International Thermonuclear Experimental Reactor (ITER) neutral beam design
Myers, T.J.; Brook, J.W.; Spampinato, P.T.; Mueller, J.P.; Luzzi, T.E.; Sedgley, D.W. . Space Systems Div.)
1990-10-01
This report discusses the following topics on ITER neutral beam design: ion dump; neutralizer and module gas flow analysis; vacuum system; cryogenic system; maintainability; power distribution; and system cost.
Approximate inverse preconditioning of iterative methods for nonsymmetric linear systems
Benzi, M.; Tuma, M.
1996-12-31
A method for computing an incomplete factorization of the inverse of a nonsymmetric matrix A is presented. The resulting factorized sparse approximate inverse is used as a preconditioner in the iterative solution of Ax = b by Krylov subspace methods.
Advancing the Physics Basis of Quiescent H-mode through Exploration of ITER Relevant Parameters
Solomon, W. M.; Burrell, K. H.; Fenstermacher, M. E.; Garofalo, A. M.; Grierson, B. A.; Loarte, A.; McKee, G. R.; Nazikian, R.; Snyder, B. P.
2014-09-01
Recent experiments on DIII-D have overcome a long-standing limitation in accessing quiescent H-mode (QH-mode), a high confinement state of the plasma that does not exhibit the explosive instabilities associated with edge localized modes (ELMs). In the past, QH-mode was associated with low density operation, but has now been extended to high normalized densities compatible with operation envisioned for ITER. Through the use of strong shaping, QH-mode plasmas have been maintained at high densities, both absolute (ηe ≈ 7 × 1019 m—3) and normalized Greenwald fraction (ηe/ηG > 0:7) . In these plasmas, the pedestal can evolve to very high pressures and current as the density is increased. Calculations of the pedestal height and width from the EPED model are quantitatively consistent with the experimental observed evolution with density. The comparison of the dependence of the maximum density threshold for QH-mode with plasma shape help validate the underlying theoretical peeling-ballooning models describing ELM stability. High density QH-mode operation with strong shaping has allowed stable access to a previously predicted regime of very high pedestal dubbed \\Super H-mode". In general, QH-mode is found to achieve ELM-stable operation while maintaining adequate impurity exhaust, due to the enhanced impurity transport from an edge harmonic oscillation, thought to be a saturated kink- peeling mode driven by rotation shear. In addition, the impurity confinement time is not affected by rotation, even though the energy confinement time and measured E Χ B shear is observed to increase at low toroidal rotation. Together with demonstrations of high beta, high confinement and low q95 for many energy confinement times, these results suggest QH-mode as a potentially attractive operating scenario for ITER's Q=10 mission.
Parallel iterative methods for sparse linear and nonlinear equations
NASA Technical Reports Server (NTRS)
Saad, Youcef
1989-01-01
As three-dimensional models are gaining importance, iterative methods will become almost mandatory. Among these, preconditioned Krylov subspace methods have been viewed as the most efficient and reliable, when solving linear as well as nonlinear systems of equations. There has been several different approaches taken to adapt iterative methods for supercomputers. Some of these approaches are discussed and the methods that deal more specifically with general unstructured sparse matrices, such as those arising from finite element methods, are emphasized.
An automatic ordering method for incomplete factorization iterative solvers
Forsyth, P.A.; Tang, W.P. . Dept. of Computer Science); D'Azevedo, E.F.D. )
1991-01-01
The minimum discarded fill (MDF) ordering strategy for incomplete factorization iterative solvers is developed. MDF ordering is demonstrated for several model son-symmetric problems, as well as a water-flooding simulation which uses an unstructured grid. The model problems show a three to five fold decrease in the number of iterations compared to natural orderings. Greater than twofold improvement was observed for the waterflooding simulation. 26 refs., 7 figs., 3 tabs.
Development of the ITER magnetic diagnostic set and specification.
Vayakis, G; Arshad, S; Delhom, D; Encheva, A; Giacomin, T; Jones, L; Patel, K M; Pérez-Lasala, M; Portales, M; Prieto, D; Sartori, F; Simrock, S; Snipes, J A; Udintsev, V S; Watts, C; Winter, A; Zabeo, L
2012-10-01
ITER magnetic diagnostics are now in their detailed design and R&D phase. They have passed their conceptual design reviews and a working diagnostic specification has been prepared aimed at the ITER project requirements. This paper highlights specific design progress, in particular, for the in-vessel coils, steady state sensors, saddle loops and divertor sensors. Key changes in the measurement specifications, and a working concept of software and electronics are also outlined.
An iterative method for systems of nonlinear hyperbolic equations
NASA Technical Reports Server (NTRS)
Scroggs, Jeffrey S.
1989-01-01
An iterative algorithm for the efficient solution of systems of nonlinear hyperbolic equations is presented. Parallelism is evident at several levels. In the formation of the iteration, the equations are decoupled, thereby providing large grain parallelism. Parallelism may also be exploited within the solves for each equation. Convergence of the interation is established via a bounding function argument. Experimental results in two-dimensions are presented.
NASA Astrophysics Data System (ADS)
Pendrill, Ann-Marie
2005-11-01
Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.
ERIC Educational Resources Information Center
Rule, Audrey C.
This document describes a game that provides students with practice in recognizing three dimensional crystal shapes and planar geometric shapes of crystal faces. It contains information on the objective of the game, game preparation, and rules for playing. Play cards are included (four to a page). (ASK)
Visible and Infrared Optical Design for the ITER Upper Ports
Lasnier, C; Seppala, L; Morris, K; Groth, M; Fenstermacher, M; Allen, S; Synakowski, E; Ortiz, J
2007-03-01
This document contains the results of an optical design scoping study of visible-light and infrared optics for the ITER upper ports, performed by LLNL under contract for the US ITER Project Office. ITER is an international collaboration to build a large fusion energy tokamak with a goal of demonstrating net fusion power for pulses much longer than the energy confinement time. At the time of this report, six of the ITER upper ports are planned to each to contain a camera system for recording visible and infrared light, as well as other diagnostics. the performance specifications for the temporal and spatial resolution of this system are shown in the Section II, Functional Specifications. They acknowledge a debt to Y. Corre and co-authors of the CEA Cadarache report ''ITER wide-angle viewing and thermographic and visible system''. Several of the concepts used in this design are derived from that CEA report. The infrared spatial resolution for optics of this design is diffraction-limited by the size of the entrance aperture, at lower resolution than listed in the ITER diagnostic specifications. The size of the entrance aperture is a trade-off between spatial resolution, optics size in the port, and the location of relay optics. The signal-to-noise ratio allows operation at the specified time resolutions.
Development of Jacketing Technologies for Iter CS and TF Conductor
NASA Astrophysics Data System (ADS)
Hamada, K.; Nakajima, H.; Matsui, K.; Kawano, K.; Takano, K.; Tsutsumi, F.; Okuno, K.; Teshima, O.; Soejima, K.
2008-03-01
The Japan Atomic Energy Agency (JAEA) has developed jacketing technologies for ITER Toroidal Field (TF) and Central Solenoid (CS) conductor. Full scale TF and CS conduits were fabricated using carbon-reduced SUS316LN and boron-added (˜40 ppm) high manganese stainless steel (0.025C -22Mn -13Cr -9Ni -0.12N: JK2LB), respectively. Welding condition was optimized so that back bead does not interfere a cable insertion. The weld joint samples were compacted by a compaction machine that was newly constructed and tested at 4.2 K. Mechanical characteristics at 4K of CS, TF conduits and CS welded joint satisfied ITER mechanical requirements. TF welded joint shows slightly lower value of 0.2% yield strength (885 MPa) than that of ITER requirement (900 MPa). The TF conduit contains nitrogen content of 0.14%, which is minimum value in ITER specification. The lower nitrogen content may be caused by the release of nitrogen from molten metal during non-filler welding resulting in a 4 K strength decrease. To satisfy the ITER requirements, minimum nitrogen contents of conduit should be increased from 0.14% to 0.15% at least. Therefore, JAEA successfully developed TF and CS conduits with welding technologies and finalized the procurement specification for ITER conductor jacketing.
Skeldon, Mark D.; Letzring, Samuel A.
1999-03-23
Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses.
Skeldon, M.D.; Letzring, S.A.
1999-03-23
Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses. 8 figs.
ERIC Educational Resources Information Center
Rodwell, Peter
1982-01-01
Describes and evaluates the hardware, software, peripheral devices, performance capabilities, and programing capacity of the Sinclair ZX Spectrum microcomputer. The computer's display system, its version of the BASIC programing language, its graphics capabilities, and the unique features of its data entry keyboard are discussed. (JL)
ERIC Educational Resources Information Center
Geller, Henry; Lampert, Donna
This paper, the third in a series exploring future options for public policy in the communications and information arenas, argues that the communications spectrum--e.g., public mobile service, private radio, and domestic satellites--is a valuable but limited resource that should benefit all Americans. After a background discussion, it is…
ERIC Educational Resources Information Center
Landegren, G. F.
1975-01-01
Describes a device which employs two diffraction gratings and three or four simple lenses to produce arbitrary absorption or emission spectra that may be doppler shifted and spectroscopically examined by students some distance away. It may be regarded as a sort of artificial star whose spectrum may be analyzed as an undergraduate laboratory…
Barbisan, M. Zaniol, B.; Pasqualotto, R.
2014-11-15
A test facility for the development of the neutral beam injection system for ITER is under construction at Consorzio RFX. It will host two experiments: SPIDER, a 100 keV H{sup −}/D{sup −} ion RF source, and MITICA, a prototype of the full performance ITER injector (1 MV, 17 MW beam). A set of diagnostics will monitor the operation and allow to optimize the performance of the two prototypes. In particular, beam emission spectroscopy will measure the uniformity and the divergence of the fast particles beam exiting the ion source and travelling through the beam line components. This type of measurement is based on the collection of the H{sub α}/D{sub α} emission resulting from the interaction of the energetic particles with the background gas. A numerical model has been developed to simulate the spectrum of the collected emissions in order to design this diagnostic and to study its performance. The paper describes the model at the base of the simulations and presents the modeled H{sub α} spectra in the case of MITICA experiment.
Toh, K.C.; Trefethen, L.N.
1994-12-31
What properties of a nonsymmetric matrix A determine the convergence rate of iterations such as GMRES, QMR, and Arnoldi? If A is far from normal, should one replace the usual Ritz values {r_arrow} eigenvalues notion of convergence of Arnoldi by alternative notions such as Arnoldi lemniscates {r_arrow} pseudospectra? Since Krylov subspace iterations can be interpreted as minimization processes involving polynomials of matrices, the answers to questions such as these depend upon mathematical problems of the following kind. Given a polynomial p(z), how can one bound the norm of p(A) in terms of (1) the size of p(z) on various sets in the complex plane, and (2) the locations of the spectrum and pseudospectra of A? This talk reports some progress towards solving these problems. In particular, the authors present theorems that generalize the Kreiss matrix theorem from the unit disk (for the monomial A{sup n}) to a class of general complex domains (for polynomials p(A)).
The design of ROM-type holographic memory with iterative Fourier transform algorithm
NASA Astrophysics Data System (ADS)
Akamatsu, Hideki; Yamada, Kai; Unno, Noriyuki; Yoshida, Shuhei; Taniguchi, Jun; Yamamoto, Manabu
2013-03-01
The research and development of the holographic data storage (HDS) is advanced, as one of the high-speed, mass storage systems of the next generation. Recently, along the development of the write-once system that uses photopolymer media, large capacity ROM type HDS which can replace conventional optical discs becomes important. In this study, we develop the ROM type HDS using a diffractive optical element (DOE), and verify the effectiveness of our approach. In order to design DOE, iterative Fourier transform algorithm was adopted, and DOE is fabricated with electron beam (EB) cutting and nanoimprint lithography. We optimize the phase distribution of the hologram by iterative Fourier transform algorithm known as Gerchberg-Saxton (GS) algorithm with the angular spectrum method. In the fabrication process, the phase distribution of the hologram is implicated as the concavity and convexity structure by the EB cutting and transcribed with nanoimprint lithography. At this time, the mold is formed as multiple-stage concavity and convexity. The purpose of multiple-stage concavity and convexity is to obtain high diffraction efficiency and signal-to-noise ratio (SNR). Fabricated trial model DOE is evaluated by the experiment.
Barbisan, M; Zaniol, B; Pasqualotto, R
2014-11-01
A test facility for the development of the neutral beam injection system for ITER is under construction at Consorzio RFX. It will host two experiments: SPIDER, a 100 keV H(-)/D(-) ion RF source, and MITICA, a prototype of the full performance ITER injector (1 MV, 17 MW beam). A set of diagnostics will monitor the operation and allow to optimize the performance of the two prototypes. In particular, beam emission spectroscopy will measure the uniformity and the divergence of the fast particles beam exiting the ion source and travelling through the beam line components. This type of measurement is based on the collection of the Hα/Dα emission resulting from the interaction of the energetic particles with the background gas. A numerical model has been developed to simulate the spectrum of the collected emissions in order to design this diagnostic and to study its performance. The paper describes the model at the base of the simulations and presents the modeled Hα spectra in the case of MITICA experiment.
Neural network iterative diagonalization method to solve eigenvalue problems in quantum mechanics.
Yu, Hua-Gen
2015-06-01
We propose a multi-layer feed-forward neural network iterative diagonalization method (NNiDM) to compute some eigenvalues and eigenvectors of large sparse complex symmetric or Hermitian matrices. The NNiDM algorithm is developed by using the complex (or real) guided spectral transform Lanczos (cGSTL) method, thick restart technique, and multi-layered basis contraction scheme. Artificial neurons (or nodes) are defined by a set of formally orthogonal Lanczos polynomials, where the biases and weights are dynamically determined through a series of cGSTL iterations and small matrix diagonalizations. The algorithm starts with one random vector. The last output layer produces wanted eigenvalues and eigenvectors near a given reference value via a linear transform diagonalization approach. Since the algorithm uses the spectral transform technique, it is capable of computing interior eigenstates in dense spectrum regions. The general NNiDM algorithm is applied for calculating energies, widths, and wavefunctions of two typical molecules HO2 and CH4 as examples. PMID:25959361
Baylor, Larry R; Commaux, Nicolas JC; Jernigan, Thomas C; Meitner, Steven J; Brooks, N. H.; Combs, Stephen Kirk; Evans, T.E.; Fenstermacher, M. E.; Lasnier, C. J.; Moyer, R.A.; Osborne, T. H.; Parks, P. B.; Strait, E. J.; Unterberg, Ezekial A; Loarte, A.
2012-01-01
. The injection of high repetition rate deuterium pellets is shown to trigger high-frequency edge localized modes (ELMs) in otherwise low natural ELM frequency H-mode deuterium discharges in the DIII-D tokamak. The resulting triggered ELMs have significantly lower energy and particle fluxes to the divertor than the natural ELMs. The plasma global energy confinement and density are not strongly affected by the pellet perturbations. The plasma core impurity density is strongly reduced with the application of the pellets. These experiments were performed in plasmas designed to match the ITER baseline configuration in shape and normalized operation with input power just above the H-mode power threshold. This strongly reduced ELM intensity shows promise for exploitation in ITER to control ELM size while maintaining high plasma purity and performance.
NASA Astrophysics Data System (ADS)
Knaster, J.; Evans, D.; Rajainmaki, H.
2012-06-01
The pre-compression rings (PCRs) for the International Thermonuclear Experimental Reactor (ITER) represent one of the largest and most highly stressed composite structures ever designed for long term operation at 4K. Three rings, each 5m in diameter and 337 × 288 mm in cross-section, will be installed at the top and bottom of the eighteen "D" shaped Toroidal Field (TF) coils to apply a total centripetal load of 70 MN per TF coil. The interaction of the 68 kA conductor current circulating in the coil (for a total of 9.1MA) with the required magnetic field to confine the plasma during operation will result in Lorentz forces that build in-plane and out-of-plane loads. The PCRs are essential to keep the stresses below the acceptable level for the ITER magnets structural materials.
NASA Astrophysics Data System (ADS)
Zou, Wenlong; Cai, Zhijian; Zhou, Hongwu; Wu, Jianhong
2013-12-01
Raman spectroscopy is fast and nondestructive, and it is widely used in chemistry, biomedicine, food safety and other areas. However, Raman spectroscopy is often hampered by strong fluorescence background, especially in food additives detection and biomedicine researching. In this paper, one efficient technique was the multi-excitation Raman difference spectroscopy (MERDS) which incorporated a series of small wavelength-shift wavelengths as excitation sources. A modified multi-energy constrained iterative deconvolution (MMECID) algorithm was proposed to reconstruct the Raman Spectroscopy. Computer simulation and experiments both demonstrated that the Raman spectrum can be well reconstructed from large fluorescence background. The more excitation sources used, the better signal to noise ratio got. However, many excitation sources were equipped on the Raman spectrometer, which increased the complexity of the experimental system. Thus, a trade-off should be made between the number of excitation frequencies and experimental complexity.
NASA Astrophysics Data System (ADS)
Watanabe, Hiroyuki
In this research, an iterative learning type courseware was made, the distribution of time scores in the courseware is gotten by the learning management system. It is a proposed method by which the distribution of time scores is changed to frequency and to power spectrum using Fourier Transform. The learning process continues until students get the passing scores and are classified by using these values, which are related to average time and the average of scores‧ square. Furthermore, the cross-correlation coefficients between the standard student and students are calculated, and delay times are analyzed. Finally, the transfer functions of some students are calculated, and the characteristics of the learning processes are analyzed.
Green`s function of Maxwell`s equations and corresponding implications for iterative methods
Singer, B.S.; Fainberg, E.B.
1996-12-31
Energy conservation law imposes constraints on the norm and direction of the Hilbert space vector representing a solution of Maxwell`s equations. In this paper, we derive these constrains and discuss the corresponding implications for the Green`s function of Maxwell`s equations in a dissipative medium. It is shown that Maxwell`s equations can be reduced to an integral equation with a contracting kernel. The equation can be solved using simple iterations. Software based on this algorithm have successfully been applied to a wide range of problems dealing with high contrast models. The matrix corresponding to the integral equation has a well defined spectrum. The equation can be symmetrized and solved using different approaches, for instance one of the conjugate gradient methods.
Theoretical model of Saturn's kilometric radiation spectrum
NASA Astrophysics Data System (ADS)
Galopeau, P.; Zarka, P.; Le Queau, D.
1989-07-01
A model was developed, which allowed the theoretical derivation of an envelope for the average spectrum of the Saturnian kilometric radiation (SKR), assuming that the SKR is generated by the cyclotron maser instability. The theoretical SKR spectrum derived was found to exhibit the same spectral features as the observed mean spectra. Namely, the overall shape of both calculated and measured spectra are similar, with the fluxes peaking at frequencies of 100,000 Hz and decreasing abruptly at high frequencies, and more slowly at lower frequencies. The calculated spectral intensity levels exceed the most intense observed intensities by up to 1 order of magnitude, suggesting that the SKR emission is only marginally saturated by nonlinear processes.
NASA Astrophysics Data System (ADS)
Ren, Lin; Pan, Delu; Hao, Zengzhou; Mao, Zhihua; He, Xianqiang
2011-11-01
Synthetic aperture radar (SAR) can measure directional wave spectrum based on the closed nonlinear SAR-ocean mapping mechanism. The according wave spectrum retrieval algorithm has been developing for decades, but some limitations remain, like high wave number cut off in azimuthal direction and the need for the first guess spectrum. Wave spectrometer is a kind of new satellite-based real aperture radar (RAR) operating at low incidence, which has a narrow beam and scans complete 360° by antenna rotation. It derives wave spectrum by the simple linear relation between the wave spectrum and the modulation spectrum from the wave spectrometer. The linear coefficient can be estimated by the nadir beam or external wind speed information. This paper proposes a method on the wave spectrum estimation based on the joint measurement from synchronous SAR and wave spectrometer. Firstly, the modulation spectrum is derived from the signal spectrum of the wave spectrometer, from which the relative wave spectrum can be constructed. Then the relative wave spectrum is seen as the first guess spectrum for the wave spectrum retrieval of SAR image. Because the relative wave spectrum has the same pattern with the real wave spectrum but has different absolute energy, we can retrieve the directional wave spectrum by the iteration way based on the relative wave spectrum from the SAR image. This paper makes use of simulation technology to validate the joint measurement. The simulation compares the input spectrum and the retrieved one in terms of peak direction, peak wavelength and significant wave height, which has a deviation of 6°, 4m and 0.3m, respectively. Simulation results show the joint measurement has the feasibility for the retrieval of directional ocean wave spectrum.
NASA Astrophysics Data System (ADS)
Pearson, Darren L.; Schumm, Jeffry S.; Jones, Leroy, II; Tour, James M.
1994-06-01
We have devised an iterative convergent/divergent approach to conjugated oligomers that might serve as molecular wires. The molecular length doubles with each iteration. The systems prepared are completely monodispersed and based upon oligo(thiophene-ethynylene)s (1) and oligo(phenylene-ethynylene)s at 100 A and 128 A long, respectively. The optical and size exclusion chromatography (SEC) properties are discussed. Methods are outlined to attach end groups that might serve as molecular alligator clips.
Collision Broadening Of Line Spectrum In Sonoluminescence
Li Chaohui; An Yu
2008-06-24
The direct measurement of temperature inside a sonoluminescing bubble as it is at its flashing phase is almost impossible due to the smallness of the bubble and the short duration of the flashing. One may estimate the temperature through fitting the continuum spectrum of sonoluminescence by the black body radiation formula, or fitting the shape of atomic or molecular line spectrum (the different temperature, density and pressure result in the different shape of the line spectrum due to the effect of collision broadening). However, the temperature changes in a huge range at short duration as the bubble flashes, therefore, the observed spectra are some kind of average one, so are those fitted results. To evaluate the instantaneous temperature more accurately, we simulate the processes of the bubble motion and the thermodynamics inside the bubble, in which atomic or molecular line spectra with the collision broadening effect and the continuum spectra contributed from the processes of electron-atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation and radiative attachment of electrons to atoms and molecules are taken into account in calculating the light emission. If both the calculated continuum spectra and the shape of line spectra can well represent the experimental data, we may deduce that the calculation of the temperature, density and pressure is reliable and we indirectly evaluate those quantities inside the bubble. In the present calculation, the line spectra of OH radical at about 310 nm mixing the electron transition with the vibration and rotational bands are considered. The calculation qualitatively consists with the observation, and we expect that with the more precise bubble dynamics model instead of the uniform model employed in the present calculation we may improve the quantitative result.
DIII-D Research in Support of ITER
Strait, E
2008-10-14
DIII-D research is providing key information for the design and operation of ITER. Discharges that simulate ITER operating scenarios in conventional H-mode, advanced inductive, hybrid, and steady state regimes have achieved normalized performance consistent with ITER's goals for fusion performance. Stationary discharges with high {beta}{sub N} and 90% noninductive current that project to Q=5 in ITER have been sustained for a current relaxation time ({approx}2.5 s), and high-beta wall-stabilized discharges with fully non-inductive current drive have been sustained for more than one second. Detailed issues of plasma control have been addressed, including the development of a new large-bore startup scenario for ITER. A broad research program provides the physics basis for predicting the performance of ITER. Recent key results include the discovery that the L-H power threshold is reduced with low neutral beam torque, and the development of a successful model for prediction of the H-mode pedestal height in DIII-D. Research areas with the potential to improve ITER's performance include the demonstration of ELM-free 'QH-mode' discharges with both co and counter-injection, and validation of the predicted torque generated by static, non-axisymmetric magnetic fields. New diagnostics provide detailed benchmarking of turbulent transport codes and direct measurements of the anomalous transport of fast ions by Alfven instabilities. DIII-D research also contributes to the basis for reliable operation in ITER, through active control of the chief performance-limiting instabilities. Recently, ELM suppression with resonant magnetic perturbations has been demonstrated at collisionality similar to ITER's, while simultaneous stabilization of NTMs (by localized current drive) and RWMs (by magnetic feedback) has allowed stable operation at high beta and low rotation. In research aimed at improving the lifetime of material surfaces near the plasma, recent experiments have investigated
High internal inductance for steady-state operation in ITER and a reactor
NASA Astrophysics Data System (ADS)
Ferron, J. R.; Holcomb, C. T.; Luce, T. C.; Park, J. M.; Kolemen, E.; La Haye, R. J.; Solomon, W. M.; Turco, F.
2015-07-01
Increased confinement and ideal stability limits at relatively high values of the internal inductance ({{\\ell}i} ) have enabled an attractive scenario for steady-state tokamak operation to be demonstrated in DIII-D. Normalized plasma pressure in the range appropriate for a reactor has been achieved in high elongation and triangularity double-null divertor discharges with {β\\text{N}}≈ 5 at {{\\ell}i}≈ 1.3 , near the ideal n=1 kink stability limit calculated without the effect of a stabilizing vacuum vessel wall, with the ideal-wall limit still higher at {β\\text{N}}>5.5 . Confinement is above the H-mode level with {{H}98≤ft(\\text{y,2\\right)}}≈ 1.8 . At {{q}95}≈ 7.5 , the current is overdriven, with bootstrap current fraction {{f}\\text{BS}}≈ 0.8 , noninductive current fraction {{f}\\text{NI}}>1 and negative surface voltage. For ITER (which has a single-null divertor shape), operation at {{\\ell}i}≈ 1 is a promising option with {{f}\\text{BS}}≈ 0.5 and the remaining current driven externally near the axis where the electron cyclotron current drive efficiency is high. This scenario has been tested in the ITER shape in DIII-D at {{q}95}=4.8 , so far reaching {{f}\\text{NI}}=0.7 and {{f}\\text{BS}}=0.4 at {β\\text{N}}≈ 3.5 with performance appropriate for the ITER Q=5 mission, {{H}89}{β\\text{N}}/q952≈ 0.3 . Modeling studies explored how increased current drive power for DIII-D could be applied to maintain a stationary, fully noninductive high {{\\ell}i} discharge. Stable solutions in the double-null shape are found without the vacuum vessel wall at {β\\text{N}}=4 , {{\\ell}i}=1.07 and {{f}\\text{BS}}=0.5 , and at {β\\text{N}}=5 with the vacuum vessel wall.
2010-01-01
Background Landmark based geometric morphometrics (GM) allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species. Results We show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species. Conclusions To preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes. PMID:20964872
NASA Astrophysics Data System (ADS)
Kirschner, Matthias; Wesarg, Stefan
2011-03-01
Active Shape Models (ASMs) are a popular family of segmentation algorithms which combine local appearance models for boundary detection with a statistical shape model (SSM). They are especially popular in medical imaging due to their ability for fast and accurate segmentation of anatomical structures even in large and noisy 3D images. A well-known limitation of ASMs is that the shape constraints are over-restrictive, because the segmentations are bounded by the Principal Component Analysis (PCA) subspace learned from the training data. To overcome this limitation, we propose a new energy minimization approach which combines an external image energy with an internal shape model energy. Our shape energy uses the Distance From Feature Space (DFFS) concept to allow deviations from the PCA subspace in a theoretically sound and computationally fast way. In contrast to previous approaches, our model does not rely on post-processing with constrained free-form deformation or additional complex local energy models. In addition to the energy minimization approach, we propose a new method for liver detection, a new method for initializing an SSM and an improved k-Nearest Neighbour (kNN)-classifier for boundary detection. Our ASM is evaluated with leave-one-out tests on a data set with 34 tomographic CT scans of the liver and is compared to an ASM with standard shape constraints. The quantitative results of our experiments show that we achieve higher segmentation accuracy with our energy minimization approach than with standard shape constraints.nym
Liver recognition based on statistical shape model in CT images
NASA Astrophysics Data System (ADS)
Xiang, Dehui; Jiang, Xueqing; Shi, Fei; Zhu, Weifang; Chen, Xinjian
2016-03-01
In this paper, an automatic method is proposed to recognize the liver on clinical 3D CT images. The proposed method effectively use statistical shape model of the liver. Our approach consist of three main parts: (1) model training, in which shape variability is detected using principal component analysis from the manual annotation; (2) model localization, in which a fast Euclidean distance transformation based method is able to localize the liver in CT images; (3) liver recognition, the initial mesh is locally and iteratively adapted to the liver boundary, which is constrained with the trained shape model. We validate our algorithm on a dataset which consists of 20 3D CT images obtained from different patients. The average ARVD was 8.99%, the average ASSD was 2.69mm, the average RMSD was 4.92mm, the average MSD was 28.841mm, and the average MSD was 13.31%.
Isogeometric shape optimisation of shell structures using multiresolution subdivision surfaces
NASA Astrophysics Data System (ADS)
Xiao, Xiao; Bandara, Kosala; Cirak, Fehmi
2016-08-01
We introduce the isogeometric shape optimisation of thin shell structures using subdivision surfaces. Both triangular Loop and quadrilateral Catmull-Clark subdivision schemes are considered for geometry modelling and finite element analysis. A gradient-based shape optimisation technique is implemented to minimise compliance, i.e. to maximise stiffness. Different control meshes describing the same surface are used for geometry representation, optimisation and finite element analysis. The finite element analysis is performed with subdivision basis functions corresponding to a sufficiently fine control mesh. During iterative shape optimisation the geometry is updated starting from the coarsest control mesh and proceeding to increasingly finer control meshes. The proposed approach is applied to three optimisation examples, namely a catenary, a roof over a rectangular domain, and free-form architectural shell roof. The influence of the geometry description and the used subdivision scheme on the obtained optimised curved geometries are investigated in detail.
NASA Astrophysics Data System (ADS)
Santo, Loredana
2016-02-01
Recent advances in shape memory polymer (SMP) foam research are reviewed. The SMPs belong to a new class of smart polymers which can have interesting applications in microelectromechanical systems, actuators and biomedical devices. They can respond to specific external stimulus changing their configuration and then remember the original shape. In the form of foams, the shape memory behaviour can be enhanced because they generally have higher compressibility. Considering also the low weight, and recovery force, the SMP foams are expected to have great potential applications primarily in aerospace. This review highlights the recent progress in characterization, evaluation, and proposed applications of SMP foams mainly for aerospace applications.
NASA Astrophysics Data System (ADS)
Tatartchenko, Vitali A.
Crystals of specified shape and size (shaped crystals) with controlled crystal growth (SCG) defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section shaping technique (CST) grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the
Perception of Mirror Symmetry in Autism Spectrum Disorders
ERIC Educational Resources Information Center
Falter, Christine M.; Bailey, Anthony J.
2012-01-01
Gestalt grouping in autism spectrum disorders (ASD) is selectively impaired for certain organization principles but for not others. Symmetry is a fundamental Gestalt principle characterizing many biological shapes. Sensitivity to symmetry was tested using the Picture Symmetry Test, which requires finding symmetry lines on pictures. Individuals…
Nonlinear Simulation of the Tooth Enamel Spectrum for EPR Dosimetry
NASA Astrophysics Data System (ADS)
Kirillov, V. A.; Dubovsky, S. V.
2016-07-01
Software was developed where initial EPR spectra of tooth enamel were deconvoluted based on nonlinear simulation, line shapes and signal amplitudes in the model initial spectrum were calculated, the regression coefficient was evaluated, and individual spectra were summed. Software validation demonstrated that doses calculated using it agreed excellently with the applied radiation doses and the doses reconstructed by the method of additive doses.
Sherman, L.L.; Taylor, A.C. III; Hou, G.W.; Korivi, V.M.
1996-12-01
The straightforward automatic-differentiation and the hand-differentiated incremental iterative methods are interwoven to produce a hybrid scheme that captures some of the strengths of each strategy. With this compromise, discrete aerodynamic sensitivity derivatives are calculated with the efficient incremental iterative solution algorithm of the original flow code. Moreover, the principal advantage of automatic differentiation is retained. The basic equations for second-order sensitivity derivatives are presented, which results in a comparison of four different methods. Each of these four schemes for second-order derivatives requires that large systems are solved first for the first-order adjoint variables. Of these latter three schemes, two require no solutions of large systems thereafter. For the other two for which additional systems are solved, the equations and solution procedures are analogous to those for the first-order derivatives. From a practical viewpoint, implementation of the second-order methods is feasible only with software tools such as automatic differentiation, because of the extreme complexity and large number of terms. First- and second-order sensitivities are calculated accurately for two airfoil problems, including a turbulent-flow example. In each of these two sample problems, three dependent variables (coefficients of lift, drag, and pitching-moment) and six independent variables (three geometric-shape and three flow-condition design variables) are considered. Several different procedures are tested, and results are compared on the basis of accuracy, computational time, and computer memory. For first-order derivatives, the hybrid incremental iterative scheme obtained with automatic differentiation is competitive with the best hand-differentiated method. Furthermore, it is at least two to four times faster than central finite differences, without an overwhelming penalty in computer memory. 23 refs., 14 tabs.
Development of ITER 15 MA ELMy H-mode Inductive Scenario
Kessel, C. E.; Campbell, D.; Gribov, Y.; Saibene, G.; Ambrosino, G.; Casper, T.; Cavinato, M.; Fujieda, H.; Hawryluk, R.; Horton, L. D.; Kavin, A.; Kharyrutdinov, R.; Koechl, F.; Leuer, J.; Loarte, A.; Lomas, P. J.; Luce, T.; Lukash, V.; Mattei, M.; Nunes, I.; Parail, V.; Polevoi, A.; Portone, A.; Sartori, R.; Sips, A. C.C.; Thomas, P. R.; Welander, A.; Wesley, J.
2008-10-16
The poloidal field (PF) coil system on ITER, which provides both feedforward and feedback control of plasma position, shape, and current, is a critical element for achieving mission performance. Analysis of PF capabilities has focused on the 15 MA Q = 10 scenario with a 300-500 s flattop burn phase. The operating space available for the 15 MA ELMy H-mode plasma discharges in ITER and upgrades to the PF coils or associated systems to establish confidence that ITER mission objectives can be reached have been identified. Time dependent self-consistent free-boundary calculations were performed to examine the impact of plasma variability, discharge programming, and plasma disturbances. Based on these calculations a new reference scenario was developed based upon a large bore initial plasma, early divertor transition, low level heating in L-mode, and a late H-mode onset. Equilibrium analyses for this scenario indicate that the original PF coil limitations do not allow low li (<0.8) operation or lower flux states, and the flattop burn durations were predicted to be less than the desired 400 s. This finding motivates the expansion of the operating space, considering several upgrade options to the PF coils. Analysis was also carried out to examine the feedback current reserve required in the CS and PF coils during a series of disturbances and a feasibility assessment of the 17 MA scenario was undertaken. Results of the studies show that the new scenario and modified PF system will allow a wide range of 15 MA 300-500 s operation and more limited but finite 17 MA operation.
Transport simulations of ITER with empirical heat diffusivity scaling
NASA Astrophysics Data System (ADS)
Becker, G.
1998-02-01
Radiative mantle scenarios of the ignited ITER Engineering Design Activity (EDA) with argon and neon influxing are explored by computer experiments using special versions of the 1.5 dimensional (1.5-D) BALDUR predictive transport code. An empirical scaling law for the effective heat diffusivity, compatible with the ITERH92-P ELMy H mode scaling and validated against experiments, is applied. The prescribed flat density profiles, conductive heat loss across the separatrix of 200 MW and ratio τ*He/ τE,r of 10 are reached in the simulations. Self-sustained thermonuclear burn is achieved for at least 485 s. The helium ash concentrations of up to 9.5% are found to cause significant fuel dilution. Owing to the high electron density, only small argon and neon fractions of 0.07 and 0.27%, respectively, are needed. In the argon scenario, the required radiation corrected thermal energy confinement time τE,r is 4.8 s. The confinement time predicted by the local scaling law is 1.4 times longer and agrees with the global scaling prediction. With argon, the design parameters are reached by radiating 128 MW within the separatrix, thus reducing the energy flow to the divertor to 73 MW. In the neon case with its more peripheral radiation, the radiative loss within the separatrix has to be diminished. Owing to the flat profile of the fuel ion density, the neoclassical drift velocities of argon and neon are directed outwards in the whole plasma. In the argon scenario, the sensitivity of transport to the density profile shape is studied. It is found that τE,r remains almost unchanged, varying between 4.5 and 4.8 s, which is explained by an analytic expression for the thermal energy. Peaking of the electron and impurity densities does not alter the required argon concentration but causes a peaking of the radiation profiles and reduction in the temperatures. Sufficiently narrow fuel ion density profiles are shown to cause inward directed neoclassical drift velocities of argon in the
NASA Astrophysics Data System (ADS)
Svilainis, L.; Kitov, S.; Rodríguez, A.; Vergara, L.; Dumbrava, V.; Chaziachmetovas, A.
2012-12-01
Ultrasonic imaging of composites was investigated. Glass and carbon fiber reinforced plastic produced by resin transfer molding and prepreg forming were analyzed. In some of the samples air bubbles were trapped during RTM (resin transfer molding) process and interlayer gaps were present in prepreg technology samples. One of the most expected techniques to apply in such case is the Split Spectrum processing. On the other hand such signals require specific processing to reliably reconstruct the temporal position of the defect reflection. Correlation processing can be used for signal compression or Wiener filtering can be applied for spectral content equalisation. Pulse signals are simple to generate, but lack the possibility to alter the signal's spectrum shape. Spread spectrum signals offer a powerful tool for signal energy over frequency band increase and resolution enhancement. CW (continuous wave) burst has high energy but lacks the bandwidth needed for SSP (spread spectrum processing). The aim of the investigation was to compare the performance of the above signals in case of composite imaging, when various Split Spectrum Processing techniques are used with preceding Wiener processing for spectral content compensation. Resulting composite signals and images obtained are presented. Structural noise removal performance was evaluated as Receiver Operating Characteristics (ROC).
Negative Ion Based Heating and Diagnostic Neutral Beams for ITER
NASA Astrophysics Data System (ADS)
Schunke, B.; Bora, D.; Antoni, V.; Bonicelli, T.; Chakraborty, A.; Cordier, J.-J.; Hemsworth, R.; Inoue, T.; Tanga, A.; Watanabe, K.
2008-04-01
To meet the requirements of the four operating and one start-up scenarios foreseen in the International Tokamak Experimental Reactor (ITER) a flexible heating mix will be required, which has to include a reliable contribution from neutral beams. The current baseline of ITER foresees 2 Heating Neutral Beam (HNB) systems based on negative ion technology, each operating at 1 MeV 40 A D- ions, and each capable of delivering up to 16.7 MW of D ° to the ITER plasma. A 3rd HNB injector is foreseen as an upgrade option. In addition a dedicated Diagnostic Neutral Beam (DNB) injecting 100 keV 60 A of negative hydrogen ions will be available for charge exchange resonant spectroscopy (CXRS). The significant R&D effort necessary to meet the design requirements will be provided in the Neutral Beam Test Facility (NBTF), which is to be constructed in Padua, Italy. This paper gives an overview of the current status of the neutral beam (NB) systems and the chosen configuration. The ongoing integration effort into the ITER plant is highlighted and open interface issues are identified. It is shown how installation and maintenance logistics has influenced the design. ITER operating scenarios are briefly discussed, including start-up and commissioning. For example it is now envisaged to have a low current hydrogen phase of ITER operations, essentially for commissioning of the many auxiliary systems used on ITER. The low current limits the achievable plasma density, and hence the NB energy due to shine through limitations. Therefore a possible reconfiguration of the auxiliary heating systems is now being discussed. Other NB related issues identified by the ongoing design review process are emphasized and possible impact on the implementations of the HNB and DNB systems is indicated.