Studies of anomalous cosmic ray N, O, and Ne using Cn track detectors

We report measurements of the energy spectra of anomalous cosmic ray N, O and Ne in the energy interval 5–25 MeV/nucleon made with stacks of cellulose nitrate sheets exposed on “Cosmos” satellites in Earth's vicinity in 1994. The successive etching was applied for the best charge identification.     

Strength considerations of optical waveguide fibers

An important aspect of optical waveguide fiber made of glass is whether it will break under a wide variety of service and manufacturing conditions. This paper covers some of the testing in which stress, length, time, and environment were vaned. The use of Weibull statistics with these data indicates that a statistically predictable behavior exists for populations of glass fibers. Extrapolation from short lengths and short times to very long lengths and very long times must be based on an understanding of the “constants” in the prediction equation. That is, these “constants” can be shown to vary when the three basic parameters cover orders of magnitude in range.     

The role of coincidence experiments in studying the nuclear continuum with high-energy electrons and protons

The Lee model of π-nucleon interactions is very simple, and, in a certain case, an exact solution of the problem of a meson scattering on two “nucleons” can be obtained. However, graphs involving crossed pions are absent in that solution. Because such crossed graphs are crucial in determining the form and character of the physical π-nucleus scattering solution, the Lee model should not be used in testing field theories of the pion-nucleus interaction.     

The Multidimensional Filter Diagonalization Method: I. Theory and Numerical Implementation

The theory and numerical aspects of the recently developed multidimensional version of the filter diagonalization method (FDM) are described in detail. FDM can construct various “ersatz” or “hybrid” spectra from multidimensional time signals. Spectral resolution is not limited by the time-frequency uncertainty principle in each separate frequency dimension, but rather by the total joint information content of the signal, i.e., N_total = N₁ × N₂ × × N_D, where some of the interferometric dimensions do not have to be represented by more than a few (e.g., two) time increments. It is shown that FDM can be used to compute various reduced-dimensionality projections of a high-dimensional spectrum directly, i.e., avoiding construction of the latter. A subsequent paper (J. Magn. Reson. 144, 357–366 (2000)) is concerned with applications of the method to 2D, 3D, and 4D NMR experiments.     

Path integral hybrid Monte Carlo calculation of the bosonic oscillators

In this paper, various correlation functions for a bosonic many-body system have been calculated using the path integral hybrid Monte Carlo method proposed by the authors [Chem. Phys. Lett. 308, 115 (1999)]. A system consisting of 32 independent particles in a harmonic well was chosen as a model problem. Calculations were carried out at two temperatures for the Boltzmann and Bose statistics. The large amplitude of the bosonic pair-correlation function around origin was found in comparison with the boltzmannoniac counterpart. This behavior can be interpreted by effective “attractive interaction” between particles arising from the Bose statistics.     

Thorium and uranium content determination using double gamma irradiation

A new technique for the determination of Th and U content in solids was proposed. The ratio of U and Th fission reaction yields for “infinite thick” metall layers was measured in the γ-ray energy range from 7 MeV to 23.5 MeV. For this purpose metallic sheets of U and Th placed next to polyethyleneterephtalate track detectors were irradiated at the Microtron MT-25. The method is based on the fact that the ratio N_U/N_Th differs sufficiently from 1.7 to 3.3 depending on the γ-ray energy. Irradiating an Uranium ethalon and samples with γ-rays of (20–23) MeV (N_U/N_Th = 2.2) and 15–17) MeV (N_U/N_Th = 3.3) one can determine simultaneously both U and Th content in samples. The comparison of the results of measuring of U and Th content in different samples obtained by the proposed and the known methods is presented.     

Wireless retrospective gating: Application to cine cardiac imaging

A new “wireless” method of cardiac imaging is introduced, which, unlike ECG triggering, allows imaging the heart at end-diastole, and greatly reduces smearing artifacts in the phase-encoding direction. It is an improvement over ECG-driven retrospective gating, in that patients with poor ECGs can be imaged. This method extends the applicability of cardiac imaging, and since it requires no physiological monitoring hardware, can be implemented easily on any MR imager. The images produced by this method are superior to those from ECG triggering, especially when viewed in a “cine” loop. The technique described herein is, furthermore, extendable to any area where periodic or quasi-periodic motion is a problem.     

Comparison of Goos–Hänchen shifts of the reflected beam from graphene on dielectrics and metals

The Goos–Hänchen shifts of the reflected beam from graphene-on-dielectric (or metal) in the optical wavelength are investigated by using the stationary-phase method. For the graphene-on-dielectric substrates, it is found that the pseudo-Brewster angle and Goos–Hänchen shift are influenced greatly by the introduced graphene sheets for TM polarization. By changing number of graphene sheets, the lateral shifts can be large positive or negative near the pseudo-Brewster angle. For TE polarization, the lateral shift is still small; however it can also be positive or negative by changing the number of graphene sheets. For the graphene-on-metal substrates, graphene sheets exert a great impact on the reflectance while has little effect on the lateral shifts of both polarizations. Finally, the role of the graphene sheets on the lateral shifts for the different visible wavelengths is discussed.     

Hopping spectroscopy in doped germanium near the metal-insulator transition

The density of states (DOS) in the vicinity of the Fermi level controls all transport phenomena at low temperatures near the metal-insulator transition (MIT). The well-known method for DOS-determination on the metallic side of the MIT, the so-called “tunneling spectroscopy”, is inapplicable on the insulating side because of the high sample resistance at low temperatures. In this work a new method for DOS-determination on the insulating side is presented. The method is based on the measurements of variable range hopping (VRH) resistance in magnetic fields. By analogy this method can be called “hopping spectroscopy”.     

激光束偏转法非球面面形测量和计算

提出了一种综合测量非球面面形的激光束偏转法 ,针对不同类型的非球面 ,共提出了三种方案 :平移法、转动法和平移转动法。该方法可测各种非球面 ,通用性强。并对激光束偏转法中对面形测量精度有极大影响的激光束反射角的测量作了重点介绍。实验结果显示 ,该方法测量精度达到λ/5～λ/10 ,接近干涉法的水平     

Network ecology: topological constraints on ecosystem dynamics

Ecological systems are complex assemblages of various species with interactions between them. The interactions can be even more important than the species themselves for understanding how the whole system is functioning and organized. For the representation of the topological space of interspecific relationships, graph theory is a suitable mathematical tool: the network perspective and the various techniques of network analysis are more and more elaborated and invading ecology. Beyond a static view on networks, fundamental questions can only be answered if dynamical analyses are also made, and now it is clear that structural and dynamical studies must not “compete” but strongly complement each other. Our aim is to give a menu of classical and more recently suggested network indices and to discuss what do we know about their relations to ecosystem dynamics. Since ecologists have very diverse problems, they need diverse techniques and a good insight in matching the adequate method to a particular problem. The main question is how to link certain graph properties to understanding and predicting the behaviour of an ecosystem. We wish to contribute to bridging the gap between extreme structural and extreme dynamical views.     

Coloured-noise-induced transitions: Exact results for external dichotomous Markovian noise

A general method to calculate explicitly the stationary probability of nonlinear systems subjected to a special case of coloured noise is presented. For a simple model system the “phase diagram” for the various noise-induced transitions is determined.     

Tensile performance of packaged optical fibers

The tensile testing of packaged optical fibers involves the measurement of elastic strains in the range 2-10%. Under these conditions slippage at the tensile grips can produce erroneous results when a nonextensometric method of measurement (e.g., in positive production testing) is used. Slippage of packaged silica fibers (polypropylene/silicone resin-coated silica fibers) observed when using standard pneumatic parallel-faced jaws has been eliminated by using 50-mm-diameter pulley grips with suitable clamps to hold the fiber ends. With this arrangement clean fiber failures are obtained within the gauge length. A correction factor has been estimated for the measured strain values by a theoretical analysis of the measured tension/extension curves for the composite polypropylene/silicone resin-coated fibers. Statistical data have also been obtained for polypropylene-(PP) coated lead silicate fibers and PP-coated “plastic clad” silica fibers. In the latter case, true failure had been obscured by the onset of fiber slippage within the PP jacket.     

A unifying lifting collocation penalty formulation including the discontinuous Galerkin, spectral volume/difference methods for conservation laws on mixed grids

Recently a new high-order formulation for 1D conservation laws was developed by Huynh using the idea of “flux reconstruction”. The formulation was capable of unifying several popular methods including the discontinuous Galerkin, staggered-grid multi-domain method, or the spectral difference/spectral volume methods into a single family. The extension of the method to quadrilateral and hexahedral elements is straightforward. In an attempt to extend the method to other element types such as triangular, tetrahedral or prismatic elements, the idea of “flux reconstruction” is generalized into a “lifting collocation penalty” approach. With a judicious selection of solution points and flux points, the approach can be made simple and efficient to implement for mixed grids. In addition, the formulation includes the discontinuous Galerkin, spectral volume and spectral difference methods as special cases. Several test problems are presented to demonstrate the capability of the method.     

Ultrasonic testing of anaerobic bonded joints

The paper deals with ultrasonic testing of adhesive joints between sheets of thickness greater than 1 mm, bonded by a "zero thickness" layer of anaerobic adhesive. In the case of equally thick sheets, interference phenomena can arise that make impossible the use of the "decay method" (a method previously developed by the authors for the case of non-zero adhesive thickness). Consequently an alternative method, termed "first peak", has been proposed. In order to evaluate the applicability of the two methods, a series of tests has been carried out on specimens having geometry suitable for both types of inspection. Also two different levels of surface roughness have been considered. The results allow for evaluating the defect detection capability of each method, accounting for the roughness effect, and give information on the suitable control procedures.     

Gaussian self-consistent approach to multichain polymer systems

Here we extend the Gaussian self-consistent method that has been successfully applied to the single polymer collapse problem to a polymer solution of many identical chains earlier. This method permits a complete study of the equilibrium thermodynamic properties as well as of the kinetic transformations. We discuss various aspects of the aggregation and collapse phenomena paying particular attention to the interplay between the intra- and inter-molecular degrees of freedom. We show that, at equilibrium, in part of the parameter space our equations may be reduced to those of the Flory-Huggins mean field theory. In kinetics a new phenomenon, notably the existence of a long-lived metastable state of “mesoglobules”, is found.     

An Accurate Characterization of CRT Monitor (II) Proposal for an Extension to CIE Method and Its Verification

According to the ICC specification that is widely used for storing colorimetric characteristics of imaging devices for the current color management systems (CMSs), CRT monitor characteristics can be described by the tone reproduction curves (TRCs) of the red, green and blue channels and a transformation matrix from linearized RGB values to tristimulus values. This idea is based on CIE Technical Report 122#x2013;1996: #x201C;The Relationship between Digital and Colorimetric Data for Computer-Controlled CRT Displays,#x201D; which resulted from the research by Berns et al. This method produces very accurate results under normal conditions. However, users often change the settings of contrast or brightness knobs to a different position from the factory default adjustments. For some of these cases, the characterization method described in the CIE 122 does not produce accurate results. In this paper, we propose an extension to the CIE method for such cases. We investigated the effect of user controls on CRT monitor characteristics at various settings, and verified that our method produced accurate results under any conditions.     

Non-destructive defect characterization of concrete structures reinforced by means of FRP

The aim of this work is to develop a reliable and precise non-destructive testing technique based on infrared thermography and post processing by means of neural networks. In particular, the experimental procedure to be implemented consists mainly in the “impulsive” heating of the structure and in the analysis of the superficial thermal response by means of a thermocamera. The procedure requires a detailed set-up, in order to assess its feasibility. In this work is presented the case study of a concrete structure strengthened by bonded FRP, with imposed well-known defects. The results obtained by means of infrared thermography were compared with results obtained by ultrasonic testing.     

Evaluation of uncertainty in measurements—problems and tools

The ISO “Guide to the Expression of Uncertainty in Measurement” (GUM) establishes a unified method for evaluating and stating measurement uncertainties that has been accepted by nearly all calibration services and most test co-operations in all parts of the world. In measurements of mechanical quantities, such as acceleration and derived motion quantities, the application of the GUM may be difficult and very time-consuming unless some possibilities of simplification are made use of. After a brief introduction to the basic procedure specified in the GUM for the calculation of the measurement uncertainty, a survey of the problems typically encountered in uncertainty calculations when, for example, vibrations are measured or accelerometers calibrated by laser interferometry is given. It is shown how a model function of simple structure can be established for the usually complex relationship between the output quantity (e.g. sensitivity of an accelerometer), the quantity to be measured (e.g. acceleration) and various influence quantities (noise, transverse motion, base strain, etc.). Among other things, non-linear effects such as the influences of distortion, hum and noise can be properly taken into account.     

Leed theory for incommensurate overlayers: Application to graphite on Pt(111)

A dynamical LEED analysis is applied to study the structure of incommensurate overlayers. The previously described BSN method is extended to the incommensurate case, providing an efficient theoretical scheme for calculating the required LEED beam intensities. This method is used to investigate the structure of an incommensurate graphite overlayer on the Pt(111) surface by analyzing the specular diffraction beam intensities at various angles. The measured LEED intensities are well represented by a surface model consisting of a graphite layer 3.70 ± 0.05 Å above the Pt(111) surface, supported by at least a partial layer of “intercalated” carbidic carbon atoms chemisorbed in three-fold hollow sites 1.25 ± 0.10 Å above the Pt(111) surface. A “data subdivision method” is applied in the R-factor analysis to distinguish between the different R-factor minima.