Miracle-dz/UniFAR-FTUs huggingface dataset:
Linear least‐squares fits with errors in both coordinates. II: Comments on parameter variances

Corrected expressions for parameter variances in linear (straight‐line) least‐squares fits given in an earlier paper [B. C. Reed, Am. J. Phys. 57, 642–646 (1989)] are presented and discussed. In addition, some simplifications to the solution given in that paper are presented, and some comments made as to the role of weighting.
Fast pressure probe measurements of a high-velocity plasma plume

This article reports measurements of stagnation pressure on a contoured coaxial gun, now installed at the Maryland Centrifugal Experiment [R. Ellis et al., Phys. Plasmas 12, 055704 (2005)]. The impact of the plasma on the stationary probe is consistent with adiabatic compression and supersonic flow. Measured pressure signals are consistent with a shock traveling at 110 km/s and a following flow with speed of 90 km/s. At late times, the pressure profile is consistent with an adiabatically expanding plasma that fills the vacuum chamber.
Horwitz's rule, transforming both sides and the design of experiments for mechanistic models

Summary. The paper develops methods for the design of experiments for mechanistic models when the response must be transformed to achieve symmetry and constant variance. The power transformation that is used is partially justified by a rule in analytical chemistry. Because of the nature of the relationship between the response and the mechanistic model, it is necessary to transform both sides of the model. Expressions are given for the parameter sensitivities in the transformed model and examples are given of optimum designs, not only for single‐response models, but also for experiments in which multivariate responses are measured and for experiments in which the model is defined by a set of differential equations which cannot be solved analytically. The extension to designs for checking models is discussed.
Final report on international comparison CCQM-K68: Nitrous oxide in synthetic air

Nitrous oxide (N2O) is one of six greenhouse gases that are regulated by the Kyoto Protocol and has a Global Warming Potential (GWP) that is 296 times that of carbon dioxide. Global levels of nitrous oxide have increased at a rate of 0.25%/yr (0.8 ppb/yr) during the last ten years. In order to monitor levels of nitrous oxide in the atmosphere, it is necessary to use measurement standards with demonstrated equivalence at the highest level of accuracy. This report describes the results of a key comparison of standard gas mixtures of nitrous oxide in synthetic air at an amount fraction of 320 nmol/mol. This key comparison is part of the programme of the Gas Analysis Working Group (GAWG) of the CCQM to demonstrate the equivalence of the standards and measurement capabilities of the NMIs for greenhouse gases. It will support the development of measurement capability at the NMIs for nitrous oxide with uncertainties within the target set by the Global Atmospheric Watch (GAW) programme of the WMO for its global monitoring networks. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm. org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
Commutative torsion theory

This paper links several notions of torsion theory with com- mutative concepts. The notion of dominant dimension (H. H. Storrer, Torsion theories and dominant dimensions, Appendix to Lecture Notes in Math., vol. 177, Springer-Verlag, Berlin and New York, 1971. MR 44 #1685.1 is shown to be very close to the notion of depth. For a commutative ring A and a torsion theory such that the primes of A, whose residue field is torsion-free, form an open set U of the spectrum of A, Spec A, a concrete interpretation of the module of quotients is given: if M is an A -module, its module of quotients Q(M) is isomorphic to the module of sections ii(U), of the quasi-coherent module V canonically associated to M. In the last part it is proved that the (T)-condition of Goldman is satisfied (O. Goldman, Rings and modules of quo- tients, J. Algebra 13 (1969), 10-47. MR 39 #6914. ) if and only if the set of primes, whose residue field is torsion-free, is an affine subset of Spec A, to- gether with an extra condition. The extra, more technical, condition is always satisfied over a Noetherian ring, in this case also it is classical that the (T)- condition of Goldman means that the localization functor Q is exact. This gives a new proof to Serre's theorem (J.-P. Serre, Sur la cohomologie des variete's algebriques, J. Math. Pures Appl. (9) 36 (1957), 1-16. MR 18, 765. ). As an application, the affine open sets of a regular Noetherian ring are also character- ized. This paper is part of the author's doctoral dissertation defended at Queen's
Two-dimensional analysis of magnetoimpedance in magnetic/metallic multilayers

This article concerns the effect of the in-plane film size on the magnetoimpedance (MI) characteristics in magnetic/metallic multilayers. The problem is approached by a two-dimensional solution of the Maxwell equations in a symmetrical three-layer film. If the edge effect is neglected, the magnetic flux generated by the current flowing through the film is confined within the outer magnetic layers. In a finite width sandwich, the flux leaks through the inner conductor. This process eventually results in a considerable drop in MI ratio if this width is smaller than the critical flux decay length depending on the effective transverse permeability, layer thickness, and frequency.
Nonlaminar multicomponent models for electron flow in positive polarity multigap accelerators

Electron flow in multigap positive‐polarity inductive accelerators is studied by numerical simulation and modeling. The objective of this work is to determine the operating principles of the electron flow such that an optimally efficient design of such machines can be achieved for intense ion beam generation. Because the electrons emitted in different gaps have different energies and canonical momenta, the theory of single‐component magnetic insulation has to be extended in order to describe such multicomponent electron flows. A two‐dimensional electromagnetic particle‐in‐cell code is used to simulate multicomponent electron flow in multigap accelerators with two, three, and four gaps. Observations from these simulations lead to new one‐dimensional, time‐independent models for these flows that incorporate the time‐averaged effects of diamagnetic electron vortices. Equivalent circuits are constructed for simulated accelerators using voltage–current relations predicted by the models. These circuit models ar.
EFFECT OF STOICHIOMETRY ON THE DYNAMIC MECHANICAL PROPERTIES OF LINBO3

Acoustic and optic phonons have been measured by Brillouin and Raman spectroscopies in LiNbO3 samples with different stoichiometries. Consequently, the elastic constants have been determined by Brillouin scattering as a function of the stoichiometry. The C44 elastic constant presents, as a function of the stoichiometry, a clear minimum for the [Li]/[Nb]=1 in the melt sample. This behavior must be related to the existence and competition of two kind of defects, i.e., extended defects induced when growing samples not at the congruent composition, and point defects present in nonstoichiometric samples. The optic phonons seem to be dominated by the point defects. The linear increase of the phonon lifetimes, with respect to an ideal stoichiometric sample, can be due to the scattering by the static imperfections and to an increase of the anharmonic scattering. Several Raman peaks, which appear when the [Li]/[Nb] ratio decreases, are related to the presence of Nb in antisites. The width of some particular phonon.
Synthesis of near-field patterns of arrays

A new technique of synthesis of near-field (NF) amplitude and phase patterns of linear, planar, of volume arrays of finite size or arrays located on a planar contour of finite size is presented. The array could consist of point dipoles or directive elements. The criterion for prescribing the NF (amplitude and phase) pattern information in the synthesis problem for unique determination of array excitation currents is also stated. The proposed near-field synthesis technique is based on the potential integral solution of source currents, Nyquist sampling of the near-field data and the technique of linear least square approximation (LLSA). The NF pattern synthesis technique is illustrated to synthesize a variety of NF patterns with a number of array configurations. Application of the proposed NF pattern synthesis technique to minimize distortion in far-field patterns of arrays mounted on a conducting platform and to realize array antennas with low sidelobes in the near and far field is also presented.
Ferroelastic switching of doped zirconia: Modeling and understanding from first principles

The properties of materials at high temperatures are often determined by complex thermodynamic mechanisms. One of the most prominent examples is the stabilization of tetragonal and cubic zirconia, which we investigate using density functional theory. The results show that the minimum energy path for the tetragonal-to-cubic phase transformation differs significantly from the paths discussed in the literature so far. This provides insight into the properties of compositions codoped with yttria and titania, an approach that has recently been proposed for the design of thermal barrier coatings.
Wafer scale production of carbon nanotube scanning probe tips for atomic force microscopy

A methodology is developed to enable wafer scale fabrication of single-walled carbon nanotube (SWNT) tips for atomic force microscopy. Catalyst selectively placed onto 375 prefabricated Si tips on a wafer is made possible by a simple patterning technique. Chemical vapor deposition on the wafer scale leads to the growth of SWNTs protruding from more than 90% of the Si tips. This represents an important step towards the scale up of nanotube probe tips for advanced nanoscale imaging of solid-state and soft biological systems and for scanning probe lithography.
On lacunary sets for nonabelian groups

Abstract Results concerning a class of lacunary sets are generalized from compact abelian to compact nonabelian groups. This class was introduced for compact abelian groups by Bozejko and Pytlik; it includes the p-Sidon sets of Edwards and Ross. A notion of test family is introduced and is used to give necessary conditions for a set to be lacunary. Using this, it is shown that (2) has no infinite p-Sidon sets for 1 ≤p<2.
A Photometric and [S II] Survey of the Young Cluster Roslund 4

Optical B- and V-band CCD data have been obtained for the young cluster Roslund 4 in conjunction with a large-scale photometric survey of open clusters. In addition, [S II] and off-line continuum CCD emission-line imaging data have also been obtained, revealing three regions in the cluster field where shock-excited gas is present. Two Herbig-Haro–like emission features are found, while a more extended emission feature, along an apparent cloud boundary, may be a result of stellar winds encountering the edge of a molecular cloud. The emission-line features are located near IRAS sources with properties consistent with star-forming regions. A previously published age for Roslund 4 (∼10 Myr) would seemingly suggest that shocked gas features should not be present in the cluster region, but an upper limit on the age (less than 4 Myr) derived from the new photometry is more consistent with their presence. Finally, the distance to Roslund 4 is found to be 1700–2000 pc, considerably closer than the previous published estimate.
Revisions in ARIMA Signal Extraction

Abstract The problem of decomposing an observed series, assumed to follow an ARIMA process, into signal plus noise is considered. It is well known that the preliminary estimates of the signal will be subject to revisions as more data become available. For a general ARIMA process, the revision in the concurrent estimate of the signal is seen to follow a stationary ARMA process, easily derived from the overall series model. The results are extended to non-concurrent preliminary estimates. Finally, it is found that, except for a scale factor, the revisions are the same for all admissible decompositions and the canonical decomposition maximizes the variance of the revision.
Discrete modelling of uncertain continuous systems having an interval structure using higher-order integrators

In this paper, a higher-order integrator approach is proposed to obtain an approximate discrete-time transfer function for uncertain continuous systems having interval uncertainties. Because of the simple algebraic operations of this approach, the resulting discrete model is a rational function of the uncertain parameters. The problem of non-linearly coupled coefficients with exponential nature occurring in the exact discretetime transfer function is therefore circumvented. Furthermore, the interval structure of the uncertain continuous-time system is preserved in the resulting discrete model by using this approach. Formulae to obtain the lower and upper bounds for the coefficients of the discrete interval system are derived, so that digital simulation and design for the uncertain continuous systems can be performed by using the available robustness results in the discrete-time domain.
Point source reconstruction principle of linear inverse problems

Exact point source reconstruction for underdetermined linear inverse problems with a block-wise structure was studied. In a block-wise problem, elements of a source vector are partitioned into blocks. Accordingly, a leadfield matrix, which represents the forward observation process, is also partitioned into blocks. A point source is a source having only one nonzero block. An example of such a problem is current distribution estimation in electroencephalography and magnetoencephalography, where a source vector represents a vector field and a point source represents a single current dipole. In this study, the block-wise norm, a block-wise extension of the ℓp-norm, was defined as the family of cost functions of the inverse method. The main result is that a set of three conditions was found to be necessary and sufficient for block-wise norm minimization to ensure exact point source reconstruction for any leadfield matrix that admit such reconstruction. The block-wise norm that satisfies the conditions is the sum of the cost of all the observations of source blocks, or in other words, the block-wisely extended leadfield-weighted ℓ1-norm. Additional results are that minimization of such a norm always provides block-wisely sparse solutions and that its solutions form cones in source space.
Comparison of three sinogram restoration methods

The raw data acquired during a computed tomography (CT) scan carry the unwanted traces of a number of adverse effects connected with the measurement setup and the acquisition process. To name a few, these include systematic errors like detector crosstalk and afterglow, fluctuations in tube power during the scan, but also statistical effects like photon noise. Most systematic effects can be cast into a linear model, providing a way for neutralizing the influence of these errors through deconvolution. However, this deconvolution process inevitably increases the image noise content. For low-dose scans, application of some kind of noise suppression algorithm is mandatory, in order to keep its disturbing influence on the reconstructed images in check. Since resolution and noise are antagonizing properties, noise suppression usually has the side effect of decreasing resolution. The interest in finding an algorithm that deals with this quandary in an optimal way is obvious. This work compares three deconvolution/denoising methods, identifying the one that performs best on a set of simulated data. The tested methods of combined sinogram deconvolution/denoising are based on (1) regularized matrix inversion, (2) straight matrix inversion plus adaptive filtering, and (3) deconvolution by a penalized maximum likelihood approach. In-plane and axial noise/resolution measurements identified the penalized maximum-likelihood method as best suited for low-dose applications. The adaptive filter approach performed well, but did not retain as much resolution when going to higher smoothing levels. The analytic deconvolution, however, could not compete against the other two methods.
Gas-Phase Infrared Photodissociation Spectroscopy of Cationic Polyaromatic Hydrocarbons

Infrared spectra of gas-phase cationic naphthalene, phenanthrene, anthracene, and pyrene are recorded in the 500-1600 cm-1 range using multiphoton dissociation in an ion trap. Gas-phase polyaromatic hydrocarbons are photoionized by an excimer laser and stored in a quadrupole ion trap. Subsequent interaction with the intense infrared radiation of a free electron laser that is tuned in resonance with an infrared-allowed transition of the ion leads to sequential multiphoton absorption facilitated by rapid intramolecular vibrational redistribution. Absorption of more than 50-100 infrared photons raises the internal energy to above the dissociation threshold, leading eventually to fragmentation of the ion. Mass selective detection of the cationic species stored in the trap yields the infrared absorption spectrum of the parent ion.
Mechanical compression for biotissue image enhancement in optical coherence tomography

The paper discusses application of mechanical compression for contrasting structural components of biotissues with different mechanical properties in optical coherence tomography (OCT) images. Ex vivo study on human rectum samples and in vivo study on human thin skin samples are performed. It is shown that for ex vivo sample the contrast between epithelial and stroma layers increases with increase in applied pressure. For in vivo sample it is shown that at weak constant applied pressure the contrast between epidermal and dermal layer increases exhibiting maximum after 2-3 minutes since pressure application. Monte Carlo simulations of OCT images of human rectum sample at different compression levels is performed in order to confirm the origin of contrast. The results of simulations qualitatively agree with experimental data.
Simulation of soliton‐like waves generated by topography with conservative fully discrete shallow‐water arbitrary‐order schemes

Purpose – The purpose of this paper is to suggest a new approach to the numerical simulation of shallow‐water flows both in plane domains and on the sphere.Design/methodology/approach – The approach involves the technique of splitting of the model operator by geometric coordinates and by physical processes. Specially chosen temporal and spatial approximations result in one‐dimensional finite difference schemes that conserve the mass and the total energy. Therefore, the mass and the total energy of the whole two‐dimensional split scheme are kept constant too.Findings – Explicit expressions for the schemes of arbitrary approximation orders in space are given. The schemes are shown to be mass‐ and energy‐conserving, and hence absolutely stable because the square root of the total energy is the norm of the solution. The schemes of the first four approximation orders are then tested by simulating nonlinear solitary waves generated by a model topography. In the analysis, the primary attention is given to the st.
Finding the elasticae by means of geometric gradient flows

This article is an announcement of our recent result on finding the critical points of a Kirchhoff elastic energy, or the so called elasticae, by means of geometric gradient flows. The reader can find out the details of the proof in [8]. In order to keep the model problem simple, we only consider a special isotropic Kirchhoff elastic energy in the following. Suppose f : I = R/Z —> M is the centerline of a closed rod. Let 7 = \dxf\, ds = 7 dx the arclength element, and ds = j~ dx the arclength differentiation. Denote by T = dsf the unit tangent vector, and K = d^f the curvature vector of /. A rod configuration F is a framed curve described by {/ (s); T ( s ) , MI (s), MZ (s)}, where the material frame {T, Mi,M2} forms an orthonormal frame field along /. Thus, we can write the skew-symmetric system
Laser range-gated underwater imaging including polarization discrimination

A range-gated underwater imaging system is described that utilizes a frequency doubled, Q- switched Nd:YAG 30 Hz laser source for illumination and a fast-gated microchannel plate intensified CCD array camera for detection. Laser pulse widths of 7 ns are timed relative to comparable camera gates with subnanosecond jitter. Results for a test bed system obtained in a 4 X 4 X 40 ft water tank with various targets are presented. Water quality was varied with the addition of progressive concentrations of Maalox as scattering agent, and monitored with a home-built laser transmissometer. The 1/4 in. , high contrast target lines were able to be resolved at ranges exceeding four attenuation lengths. A simple analytical model for image signal-to-noise ratios is presented and a straightforward polarization discrimination scheme suggested for contrast enhancement. Polarization optics were incorporated into the range-gated test bed system and results obtained for targets of varying characteristic depolarization. In all but a few cases where target and background depolarizations were similar, the signal to noise is enhanced in spite of rejection of orthogonal polarization signal. Issues regarding the evolution of the test bed system to field operation are discussed and significant progress in the development of appropriate miniaturized and ruggedized components is presented
Spatial inhomogeneity and regularization in EIT

The reconstruction of impedance distribution in electrical impedance tomography (EIT) is a nonlinear ill-posed inverse problem. In order to obtain a stable solution the problem has to be regularized. One of the most common methods for this is the generalized Tikhonov regularization. The regularization matrices that are usually used with the Tikhonov method are more or less ad hoc and the associated implicit assumptions are thus in many cases inappropriate. Here, the authors propose a method with which the prior assumptions on the approximately known spatial inhomogeneity of the impedance distribution can be included in the regularization. The proposed approach is shown to be suitable in the cases in which there are distinct and known jumps in the impedance distribution. Such an example is the imaging of the head in which there are large impedance changes in the scalp-skull and skull-brain interfaces.
Theoretical analysis of the batch variant of the self-organizing feature map algorithm for 1-d networks mapping a continuous 1-d input space

This work investigates the batch variant of Kohonen's self-organizing feature map (SOFM) algorithm both analytically and with simulations. In this algorithm, the winning neurons as well as the weight updates are computed in batch mode (epoch mode). It is shown that for 1-D maps and 1-D continuous input and weight spaces the strictly increasing or decreasing weight configurations form absorbing classes provided certain conditions on the parameters are satisfied. Ordering of the maps, convergence in distribution and asymptotic convergence are also proved analytically. Finally, simulations and comparisons with the original Kohonen algorithm on 1-D and 2-D maps are provided and are found to be in complete agreement with the theoretical results.