Pellet Positions Research Articles

Acceleration of cryogenic pellets for Shattered Pellet Injection

Shattered Pellet Injection (SPI) is considered as a method to effectively mitigate the effect of severe disruptions in tokamaks. For the development of SPI technology in ITER, the Centre for Energy Research, in collaboration with H-ion Kft and VTMT Kft, designed, constructed and operates a Disruption Mitigation System (DMS) Support Laboratory. To simulate pellet acceleration, we developed a zero-dimensional model. The model uses the parameters of pellet material, propellant gas characteristics, dimension of the barrel and fast valve (FV), opening characteristics, temperature, and filling pressure of the FV in order to calculate the time dependent pellet position, pellet velocity, FV pressure and barrel pressure during the acceleration process. The goal of the acceleration model is to forecast velocities for parameters where no data is available as of yet. This paper describes the model and compares its results to two significantly different setups: the SPI measurements at the ASDEX Upgrade test laboratory and the ITER DMS Support Laboratory. We show that our model is capable of predicting tendencies and revealing the sticking stress of pellets to the barrel.

Numerical simulation on gas behavior inside pellet based on X-ray micro-computed tomography

The objective of this work is to investigate gas behavior inside a realistic pellet model while varying inlet velocities and comparing it against published studies. A CT three-dimensional (3D) reconstruction technique was performed to construct a realistic pellet model from the two-dimensional (2D) tomographic images. The distribution of gas velocity, pressure, and species inside the pellet was investigated with computational fluid dynamics (CFD) and microfluidic boundary layer theory. The results indicated that pellet morphology, pore size, and position were responsible for the variability in velocity anisotropy inside the pellet. The pressure gradient between the windward and leeward sides of the pellet tended to rise as the inlet velocity increased, up to a maximum value of 4.2 Pa. Moreover, the pressure gradient resulted in a higher species concentration on the windward side, particularly at lower flow velocities. Finally, the potential effect of the pellet structure on the reduction process is proposed.

Digital phenotyping of individual feed intake in Atlantic salmon (Salmo salar) with the X-ray method and image analysis

The primary barrier to research into feed efficiency of Atlantic salmon (Salmo salar) is the lack of a reliable method to assess individual feed intake in large cohorts of fish over a growth period. A method with potential is the X-ray method, which images radio-opaque markers (beads) in feed consumed by fish. However, the time taken to count the markers in the digestive tract of fish is extremely onerous and the method has previously been shown to have low repeatability. Furthermore, the method has not been assessed and optimized for Atlantic salmon. Firstly, we made use of image analysis to count beads within the digital radiographs, which was highly correlated to manual counting by human observers (R2 = 0.99). Remarkably, image counting was up to 6 times faster than human counting when the number of beads per fish was high (> 300 per fish). We investigated the potential effect of different sources of error on the feed mass to bead count calibration equation and found the effects of X-ray exposure setting and the position of pellets on the X-ray plate to be negligible on the bead counts of both human and image analysis. We tested different feeding periods with the time of the X-ray images to minimize the loss of beads through defecation. We found that fish should be X-rayed within 6.5–11 hours of first being offered feed for a 6-hour feeding period which fed the entire daily ration. Lastly, we assessed the repeatability of feed intake over a 70-day growth period from 80–300 grams and found feed intake to be significantly and moderately repeatable (r = 0.45 ± 0.11), indicating developments in the method result in a consistent ranking of individual fish based on feed intake from three repeated measurements. The X-ray method combined with image analysis greatly reduces counting time without compromising accuracy, achieves promising repeatability, and is feasible in Atlantic salmon parr.

Measurement and simulation of small cryogenic neon pellet Ne-I 640 nm photon efficiency during ablation in DIII-D plasma

Small (∼1 mm) neon pellet fragments are fired into DIII-D H-mode plasmas, and resulting trajectory-averaged photon efficiencies (neutral neon ionization events for every photon emitted) of S/XB≈85 are estimated for Ne-I 640 nm by dividing the estimated initial pellet fragment mass by the measured number of emitted Ne-I photons. The experiments are modeled by running the Lagrangian particle (LP) fluid/magneto-hydrodynamic pellet code to estimate axial ablation plume neon density profiles and temperature profiles at each pellet position. These solutions are then fed into the PrismSPECT collisional-radiative code, which calculates resulting neon charge states and photon emission rates, giving a profile-average of S/XB≈109. The burnthrough plasma minor radius predicted by LP (ρ≈0.63) is reasonably close to the experimental observation ρ≈0.6. The modeling indicates that local S/XB is not constant along the pellet trajectory but tends to increase with increasing ablation rate. Non-equilibrium kinetics are predicted to be very important, while line trapping is predicted to be relatively unimportant (for Ne-I 640 nm S/XB).

Classification of plastic materials using machine-learning algorithms and microwave resonant sensor

The identification of different plastic materials in pellet form using a microwave negative-order-resonance sensor along with the evaluation of classification algorithms from machine learning is presented in this paper. Operation of the sensor is within the unlicensed ISM 2.5 GHz band, and identification of the materials is based on the measured resonant parameters from the sensor. Several classifiers are used to process the resonant parameters having uncertainty factors involved in pellet measurements (air gaps, pellet positions, dimensions and shapes), and performance comparison between the algorithms is carried out in terms of accuracy in the classification. Moreover, the presented measurement method is proposed as a fast, non-destructive, and low-power consumption way to identify plastic raw materials using a low-profile circuit having a high potential of being used in industrial processes.

Feasibility study of entrance and exit dose measurements at the contra lateral breast with alanine/electron spin resonance dosimetry in volumetric modulated radiotherapy of breast cancer

The Physikalisch-Technische Bundesanstalt has established a secondary standard measurement system for the dose to water, DW, based on alanine/ESR (Anton et al Phys. Med. Biol. 58 3259–82). The aim of this study was to test the established measurement system for the out-of-field measurements of inpatients with breast cancer.A set of five alanine pellets were affixed to the skin of each patient at the contra lateral breast beginning at the sternum and extending over the mammilla to the distal surface. During 28 fractions with 2.2 Gy per fraction, the accumulated dose was measured in four patients. A cone beam computer tomography (CBCT) scan was generated for setup purposes before every treatment. The reference CT dataset was registered rigidly and deformably to the CBCT dataset for 28 fractions. To take the actual alanine pellet position into account, the dose distribution was calculated for every fraction using the Acuros XB algorithm. The results of the ESR measurements were compared to the calculated doses.The maximum dose measured at the sternum was 19.9 Gy ± 0.4 Gy, decreasing to 6.8 Gy ± 0.2 Gy at the mammilla and 4.5 Gy ± 0.1 Gy at the distal surface of the contra lateral breast. The absolute differences between the calculated and measured doses ranged from −1.9 Gy to 0.9 Gy. No systematic error could be seen.It was possible to achieve a combined standard uncertainty of 1.63% for DW = 5 Gy for the measured dose. The alanine/ESR method is feasible for in vivo measurements.

The effect of eccentricity in the position of UO2 pellets

This work deals with a study of heat conduction in rod type fuel elements. A method of solving the heat transfer equations applied in nuclear fuel rods using the finite element method was developed in order to evaluate the performance and safety of nuclear systems. A computational code was developed in order to evaluate the equations governing the problem, the boundary, and initial conditions. This program is coupled to GiD, which is a universal, adaptive and user-friendly pre and postprocessor for numerical simulations in science and engineering. The method was validated against an analytical solution with error less than 1.4% and with respect to an improved analytical solution for axisymmetric rod and eccentricity rod with error less than a 3.6%. Applications have been developed using temperature dependent physical properties for the resolution of an axisymmetric rod and for the resolution of a rod with eccentricity. The present method allows the analysis of fuel rods in the given situations and other scenarios, also, it is a substantial tool for the analysis of fuel rods.

Direct Electrochemical Preparation of Chromium Powder in Molten Salts

Direct electrochemical reduction of Cr2O3 pellets in molten CaCl2-NaCl mixture salt was investigated by 3.0V applied potential for 12h at 550°C in the improved cell. The electrolysis products were characterized by SEM, EDS and XRD. This study showed that the reduction production was effected by the position of Cr2O3 pellets. Complete reduction of Cr2O3 pellets was achieved near the crucible. Incomplete reduction of Cr2O3 pellets was achieved near the anode and the complex compound was formed.

A study of acoustic-to-articulatory inversion of speech by analysis-by-synthesis using chain matrices and the Maeda articulatory model

In this paper, a quantitative study of acoustic-to-articulatory inversion for vowel speech sounds by analysis-by-synthesis using the Maeda articulatory model is performed. For chain matrix calculation of vocal tract (VT) acoustics, the chain matrix derivatives with respect to area function are calculated and used in a quasi-Newton method for optimizing articulatory trajectories. The cost function includes a distance measure between natural and synthesized first three formants, and parameter regularization and continuity terms. Calibration of the Maeda model to two speakers, one male and one female, from the University of Wisconsin x-ray microbeam (XRMB) database, using a cost function, is discussed. Model adaptation includes scaling the overall VT and the pharyngeal region and modifying the outer VT outline using measured palate and pharyngeal traces. The inversion optimization is initialized by a fast search of an articulatory codebook, which was pruned using XRMB data to improve inversion results. Good agreement between estimated midsagittal VT outlines and measured XRMB tongue pellet positions was achieved for several vowels and diphthongs for the male speaker, with average pellet-VT outline distances around 0.15 cm, smooth articulatory trajectories, and less than 1% average error in the first three formants.

Direct on-line Raman measurement of flying solid samples: Determination of polyethylene pellet density

We demonstrated an on-line Raman measurement of polyethylene (PE) pellet density when it is flying in a sample line. While in flight, pellets are sparsely populated at spectral collection, a spectral collection strategy covering a large spatial volume (larger number of pellets simultaneously) is necessary to acquire reasonable Raman intensity. In addition, the Raman measurement must be less sensitive to pellet position, because position and distribution are uncontrollable in a flying condition. To fulfill these requirements, a wide area illumination (WAI) scheme capable of covering a large sample volume (illumination volume: 0.7 cm 3) was used when the pellets were flying in a 2.5-cm-diameter sample line. In addition, a long focal length (250 mm) was used so that minor changes in pellet position would not significantly affect the resulting Raman spectral feature. Although Raman intensity substantially decreased due to the large void space among flying pellets, a correct spectral feature representing PE was successfully obtained without any significant spectral distortion. Using partial least squares (PLS) regression, the prediction error under flying conditions was 0.0009 g cm −3, which was comparable to that acquired when the pellets were packed (0.0008 g cm −3). When a conventional Raman scheme covering a smaller sample volume with a short focal length was used, the PE intensity decreased dramatically, and the resulting signal-to-noise ratio was not proper for quantitative analysis.

Non-linear MHD simulations of edge localized modes (ELMs)

Non-linear MHD simulations of edge localized modes (ELMs) show features in qualitative agreement with the experimental observations such as the formation and speed of filaments, features in the radial profiles and the fine structure observed in the power deposition profiles at the divertor target. The density perturbation predominantly follows the ballooning mode convection cells leading to density filaments. The temperature perturbation, due to the large parallel conduction, follows the magnetic field perturbation. Simulations of pellets injected in the H-mode pedestal show that the high pressure in the high density plasmoid can become large enough to drive ballooning type modes forming a single helical structure located at the pellet (plasmoid) position.

Recovering area functions from acoustics and midsagittal profiles.

Simultaneously recorded midsagittal pellet positions and acoustic output for several subjects comprise the Wisconsin X‐Ray Microbeam Speech Production Database (XRMB‐SPD). An articulatory synthesizer, EASY, was used to help recover area function parameters corresponding to the production of vowels by subjects in the XRMB‐SPD by means of analysis‐by‐synthesis. Specifically, for each subject, an initial personalized midsagittal profile was created based on the pellet positions, pellet trace, and pharyngeal wall trace during neutral vowel production. Based on the scales of this initial profile for a subject, subsequent midsagittal profiles were generated from the pellet data during various vowel productions. Each midsagittal profile and the corresponding first three formant frequencies were used to optimize the parameters of an area function in the EASY for closest acoustic match. The optimization was performed with a genetic algorithm. The results are examined in terms of consistency within a subject for different vowels and consistency within vowel for different subjects. Synthesized examples of vowel production will also be presented. [Work partially supported by Grant DC‐001247 to CReSS LLC.]

Empirical articulatory‐acoustic relations for vowels

Vowels tokens were extracted from four talkers in the Wisconsin X‐ray Microbeam Speech Production Database. The neighboring phonemes of these vowels were restricted to be non‐nasal and non‐liquid. The first three formant frequencies were measured using LPC analysis with manual corrections at a rate corresponding to the pellet trajectory sampling rate, thus yielding large amounts of simultaneous formant frequency and pellet position data points (between 11,000 and 20,000 for each talker.) Principal components analysis was performed for both the formant frequencies and the pellet position data, to produce three orthogonal acoustic components and four orthogonal articulatory components. A local linear regression technique, known as loess [Cleveland, W. S. and Devlin, S. J. (1988), J. Amer. Stat. Assoc., 83, 596 ‐ 610], was applied to orthogonal components to map between the acoustic and articulatory domains. This technique permits regression slopes to vary within the domain of the independent variables. The results will be discussed in terms of optimization of loess parameters (e.g. size of local neighborhoods), goodness of fit of the mappings, and the degree to which slopes in the mappings vary. Manually corrected formant frequencies will be compared with fully automatic Line Spectral Frequencies. [Supported by NIDCD‐001247 to CReSS LLC]

Predicting midsagittal pharyngeal dimensions from measures of anterior tongue position in Swedish vowels: Statistical considerations

In a re-analysis of x rays of speakers producing Swedish vowels, midsagittal pharyngeal dimensions were predicted from anterior tongue positions using procedures based on estimated tongue pellet positions. Principal component analysis was used to reduce the number of pellet degrees of freedom from eight to three prior to applying linear regression from these three independent variables to dependent vocal tract midsagittal cross distances. Except for the regions around the laryngopharynx and uvula, the pharynx dimensions were predictable from linear regressions and were significant at the p<0.05 level. Numerical experiments show that it is crucial to reduce the number of independent variables in tests of statistical significance.

Spatio-temporal investigations on the triggering of pellet induced ELMs

Pellets injected into type-I ELMy H-mode discharges are known to trigger edge-localized modes (ELMs). In order to understand the underlying processes the triggering mechanism was investigated in this paper. The major questions of the investigations to be answered were: at which magnetic surface was the ELM initiated and what was the corresponding perturbation caused by the ablating pellet? During the investigations the natural ELM cycle was probed by injecting pellets from the high field side of the ASDEX Upgrade tokamak with significantly lower frequency than the natural ELM frequency. To determine the location of the seed perturbation of the ablating pellet triggering an ELM, the dynamics of the triggered ELMs was linked to the time history of the pellet position in the plasma. The ELM onset was determined by analysing magnetic pick-up coil signals and its delay relative to the time when the pellet crossed the separatrix was measured as a function of the pellet velocity. Supposing that to trigger an ELM a pellet has to reach a certain magnetic surface of the plasma independently of its mass and velocity, the most probable location of the seed perturbation was found to be at the middle of the pedestal—at the high plasma pressure gradient region. The onset of the MHD signature of the ELMs was detected about 50 µs after the pellet reached the seed position. According to our observations ELMs can be triggered either by the cooling of the pedestal region causing sudden increase of the pedestal plasma pressure gradient driving the plasma to the unstable region of the ballooning mode or by the strong MHD perturbation triggering an instability developing into an ELM.

Time dependence of vocal tract modes during production of vowels and vowel sequences

Vocal tract shaping patterns based on articulatory fleshpoint data from four speakers in the University of Wisconsin x-ray microbeam (XRMB) database [J. Westbury, UW-Madison, (1994)] were determined with a principal component analysis (PCA). Midsagittal cross-distance functions representative of approximately the front 6 cm of the oral cavity for each of 11 vowels and vowel-vowel (VV) sequences were obtained from the pellet positions and the hard palate profile for the four speakers. A PCA was independently performed on each speaker's set of cross-distance functions representing static vowels only, and again with time-dependent cross-distance functions representing vowels and VV sequences. In all cases, results indicated that the first two orthogonal components (referred to as modes) accounted for more than 97% of the variance in each speaker's set of cross-distance functions. In addition, the shape of each mode was shown to be similar across the speakers suggesting that the modes represent common patterns of vocal tract deformation. Plots of the resulting time-dependent coefficient records showed that the four speakers activated each mode similarly during production of the vowel sequences. Finally, a procedure was described for using the time-dependent mode coefficients obtained from the XRMB data as input for an area function model of the vocal tract.

Comparison of vocal tract shaping patterns derived from articulatory fleshpoint data and MRI-based area functions

A recent addition to the University of Wisconsin x-ray microbeam (XRMB) database [Westbury, UW-Madison, 1994] (XRMB) is a speaker from whom MRI-based vocal tract area functions have been previously obtained. The purpose of this study was to compare principal components derived from collections of vocal tract shapes for vowels obtained with these two different techniques. For the XRMB data, midsagittal cross-distance functions representative of each of 11 vowels were first obtained from tongue and jaw pellet positions and the hard palate profile of the speaker. A principal components analysis was then performed on the set of cross-distance functions. Results indicated that the first two orthogonal components (referred to as modes) accounted for more than 90% of the variance. The shape of these two modes was shown to be similar to those previously determined from the same speakers set of MRI-based area functions. The XRMB-based modes were then used to develop a database-lookup technique where mode coefficients could be determined for time frames throughout a series of vowel sequences. Finally, a procedure is described for using the time-dependent mode coefficients obtained from the XRMB data as input for an area function model of the vocal tract. [Work supported by NIH R01-DC04789.]

Speech synthesis by mapping articulator movement patterns to a shape-based area function model of the vocal tract

Orthogonal components of tongue and lip displacement data from two speakers in the Univ. of Wisconsin x-ray microbeam database (Westbury, UW–Madison, 1994) were determined with a principal components analysis (PCA). The PCA was performed on steady-state vowels and at the sentence level. For every time frame, the analysis consisted of fitting a cubic spline to four pellet points on the tongue and to modified positions for the incisor pellet and the upper and lower lip pellets. The modifications brought the pellet positions to the level of the airway. The PCA was performed over a collection of frames and showed that the first two (most significant in terms of variance) orthogonal components were similar in shape to those determined from a set of MRI-based vocal tract area functions [Story and Titze, J. Phonetics 26, 223–260 (1998)]. Next, the coefficients determined from a sentence-level PCA of the microbeam data were normalized and used as input to an area function model based also on orthogonal shaping components. The result is that articulatory movement patterns from data in the x-ray microbeam database can be transformed to movement patterns of a vocal tract area function to reproduce (synthesize) the original sentence. [Work supported by NIH R01-DC04789-01.]

Principal components analysis of x-ray microbeam pellet positions

Sets of pellet coordinates from the X-ray Microbeam Speech Production Database, each corresponding to a static articulatory configuration, are submitted to a principal components analysis. Several talkers are analyzed separately, and various criteria are used to select the times in the continuous speech data from which to extract pellet data. In some instances, all of a talker’s speech data are submitted to an automatic procedure intended to select syllable nuclei, based on Mermelstein’s algorithm [P. Mermelstein, J. Acoust. Soc. Am. 58, 880–883 (1975)]. In other instances specific data are chosen by hand according to utterance type (e.g., vowel, glide, and consonant–vowel transition). These analyses are intended for use in a project to recover articulation from speech acoustics. In particular, we examine the relationship between pellet positions from data, the tongue shape reconstructed from the principal components analysis, and the parameters of a simple acoustic tube model, which is derived from the Stevens and House model [K. N. Stevens and A. S. House, J. Acoust. Soc. Am. 27, 484–493 (1955)]. [Work supported by Grant NIDCD-01247 to Sensimetrics Corporation.]

Lip-pellet positions during vowels and labial consonants

Sagittal-plane movements of small markers attached to the upper and lower lips were analyzed for ten speakers of American English, and seven speakers of Japanese. Each speaker produced simple utterances containing vowels and labial consonants. The data were analyzed to better understand: (1) patterns of pellet motions associated with labial consonant production; (2) pellet positions at discrete, acoustically-defined moments during selected speech sounds; and (3) the relationship between midline separation between the lip surfaces and inter-lip-pellet distance. Results from the study provide qualitative information about the dynamics of labial gestures for consonants involving lip closure. The data also indicate that the English and Japanese speakers positioned and moved their lips in generally similar ways during the test sounds analyzed. Finally, results suggest that plausible estimates of mid-line inter-lip separation can be derived from the trajectories of two pellets, one on each lip, as long as the possibility of lip-body deformation is taken into account.