bluuebunny/crossref_metadata_2025 huggingface dataset:
A carbon-13 nuclear magnetic resonance relaxation study of the reentrant 60CB–80CB
Authors: Lewis J. S. , Tomchuk E. , Bock E.
Published: April 2011

The carbon-13 spin-lattice relaxation times of the protonated ring carbons of octyloxycyanobiphenyl (80CB) in a 26 wt.% mixture of perdeuterated hexyloxycyanobiphenyl (60CB–d21) in 80CB are measured as a function of temperature at 22.63 MHz in the nematic (N), smectic A(SA), and reentrant nematic (RN) phases. The deuterium spectral densities of the ring deuterons of 60CB–d21 in the same sample were studied previously, and the diffusion coefficients [Formula: see text] and [Formula: see text] found in that study are used to calculate the theoretical carbon-13 relaxation times of the protonated ring carbons of 60CB. The general agreement of the theoretical values for 60CB with the experimental values for 80CB demonstrates that the two constituent molecules of the reentrant have similar motions. Small differences, similar in nature to those encountered in other studies of this interesting reentrant, however, do exist in the nematic and reentrant nematic phases and are discussed in terms of the molecular pairing model proposed by Cladis. (Phys. Rev. Lett. 35, 48 (1975).)
The evolution of partons in the nuclear medium and the EMC effect
Authors: Yang Jianjun , Zhu Yabo , Shen Hongqing , Li Guanglie , Shen Jianping
Published: April 2011

In this paper, we present the parton evolution model and describe the dynamical mechanism of the EMC effect. The ratio of the average nuclear structure function of the nucleus 56Fe to the deuteron structure function is calculated by considering the shadowing effect and the Fermi-motion correction with nuclear momentum conservation. We find that the dynamical mechanism of the EMC effect is the evolution of a parton in the nuclear medium.
Supersymmetric Baecklund transformations and solutions of super-Liouville and super-sine-Gordon equations
Authors: Chung Won-Sang , Kim Jae-Kwan
Published: April 2011

The general solutions of super-Liouville and super-sine-Gordon equations are explicitly obtained by using the supersymmetric Baecklund transformations.
Calculation of electron swarm parameters in oxygen using a rigorous Boltzmann equation analysis
Authors: Liu Jianfen , Raju G. R. Govinda
Published: April 2011

The electron swarm parameters, namely, the drift velocity, mean energy, attachment coefficient, and ionization coefficients are obtained in oxygen by solving the Boltzmann equation over a wider range of E/N values [Formula: see text]. Previous investigations have used either a space-time independent energy distribution or have adopted a rigorous approach for only a narrow range of E/N. The present analysis overcomes these restrictions and shows that the Fourier method of solving the Boltzmann equation yields very good results over the entire range of E/N.
Inverse scattering problem and the Schwinger approximation
Authors: Hooshyar M. A. , Lam T. H. , Razavy M.
Published: April 2011

A new method of inversion of the S-wave scattering amplitude based on the Schwinger variational method is presented. This method is accurate and stable and is applicable to a number of interesting physical systems such as nucleon–nucleon or nucleon–nucleus scattering even when the data are known for a finite nonrelativistic range of energies. ⁁Examples of different scattering amplitudes and their corresponding potential functions are given to show the accuracy and the stability of the method.
A simple generalization of the Kroll–Watson relation
Authors: Ehlotzky F.
Published: April 2011

We present a simple generalization of the Kroll–Watson theorem for the potential scattering of electrons in a low-frequency laser field. This generalization includes the space–dependence of the radiation field in a nonrelativistic approximation and our results apply, in particular, if (i) the electron velocities are comparatively low so that terms of the order β2 may be neglected, and (ii) the laser intensities are relatively high, requiring the inclusion of the space–dependence of the radiation field.
A charged fluid sphere in D space-time dimensions with vanishing normal pressure
Authors: Wolf C.
Published: April 2011

The metric for a charged fluid sphere in D space-time dimensions is found for the case of vanishing normal pressure. The parameters in the solutions are found by matching the interior solution to the exterior Reissner–Nordstròm solution.
Unsteady hydromagnetic free convection flow with Hall current and mass transfer along an accelerated porous plate with time-dependent temperature and concentration
Authors: Sattar Abdus , Hossain Mubarak
Published: April 2011

Unsteady free convective flow, with Hall currents and mass transfer, past an accelerated vertical porous plate is investigated in the presence of a transverse magnetic field while assuming the plate temperature and concentration to be functions of time. A similarity parameter, taken as a function of time, is introduced in the analysis. The suction or the injection velocity is then taken to be inversely proportional to the above parameter. The resulting similarity equations are then solved numerically and the effects of the Hall parameter, the magnetic parameter, and the Schmidt number on the primary and the secondary velocities are discussed and shown graphically. Finally, the corresponding x and z components of the skin friction are shown in tabular form.
Single-mode and two-mode squeezing in the three-level atom
Authors: Abdel-Hafez A. M.
Published: April 2011

We investigate the phenomena of single-mode and two-mode squeezing for a three-level atom and two modes. The field modes are initially taken in coherent states. The effects of detuning on these phenomena are studied for one-photon and two-photon interactions. The relation between the collapse and revival phenomena and single-mode and two-mode squeezing is shown. It is found that the two-mode squeezing is much more effective than the single-mode squeezing for the one-photon interaction. While for the two-photon interaction the reverse is true.
Level structures in 180Hf from the β decay of 180Lu
Authors: Sood P. C. , Sheline R. K. , Hoff R. W.
Published: April 2011

Configuration assignments to the levels of 180Hf populated in the β decay of the 5.7 min ground state of 180Lu are derived based on the observed β-transition rates, calculated two-quasiparticle excitation energies, and the observed decay modes of the levels under consideration. Corroborative evidence is sought from the results of the other experimental investigations including (n, γ), (n, 2γ), (n, n′γ), and particle transfer reaction studies. Specifically the 1607.7 and 1742.7 keV levels are assigned the IπK = 4+4 and 5+4 {7/2[514] + 1/2[510]} two-neutron configuration, and the 1374.7 and 1609.7 keV levels are assigned the 4−4 and 5−5 {9/2[624] + 1/2[510]} two-neutron configuration.
Polydisperse Mie theory applied to hollow latex spheres: An integrated light-scattering study
Authors: Strawbridge K. B. , Hallett F. R.
Published: April 2011

Integrated light-scattering spectroscopy provides a method of determining the size, coat thickness, and lumen refractive index of a variety of coated-sphere systems. Integrated light-scattering spectroscopy performed on hollow-latex-sphere suspensions also provides a basis for validating theoretical models, such as Rayleigh–Gans–Debye or Mie, of coated-sphere systems such as vesicles and micelles. The rigidity and stability of hollow latex spheres makes them an excellent candidate for the simulation of a "perfect" coated-sphere system and allows one to determine the effects of other nonstructural factors such as polydispersity. The computer controlled spectrometer collects data in the form of I(Q) vs. Q where I(Q) is the intensity of the scattered light. Mie theory, which provides an exact solution for the absorption and scattering of a sphere of arbitrary radius and refractive index, is used to fit the experimental data. The results are compared with data obtained from dynamic light scattering and electron microscopy.
Energy fluxes and kinematic limits of pions and light fragments in 1 GeV/nucleon CNO on CNO collisions
Authors: Barghouty A. F.
Published: April 2011

The center-of-mass energy fluxes and kinematic limits for the production of negative pions and light fragments (p, d, t, 3He, and 4He) from ~1 GeV/nucleon CNO on CNO collisions are calculated using a statistical nuclear-fragmentation model. Both the calculated energy fluxes and kinematic limits exhibit fluctuations and a strong degree of correlation. The two features are important for the study of nuclear interactions involving cosmic rays as they do not appear to support a superposition-alone scenario.
Finite massless quantum field theory
Authors: Shiekh A. Y.
Published: April 2011

Massless quantum field theory is usually troubled by both ultraviolet and infrared divergences. With the help of analytic continuation, this fact can be exploited to eliminate, or at least reduce the overall number of divergences. This mechanism is investigated within the context of dimensional regularization for the case of massless [Formula: see text] theory in four dimensions.
The major magnetic storm of March 13–14, 1989 and associated ionosphere effects
Authors: Rich F. J. , Denig W. F.
Published: April 2011

The geomagnetic storm of March 1989 was the largest geomagnetic storm of the decade and one of the largest of the century. We review many of the "high-latitude" ionospheric observations that were made during this storm. Most of the data presented here comes from the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP) series. A review of the DMSP data shows that most of the high-latitude, top-side ionospheric disturbance occurred on March 13 and 14. The magnitudes of the particle energy flux (ergs cm−2) (1 erg = 10−7 J) and Joule heating were not unusually large for a storm, but the area of the energy deposition, and thus the total energy deposition, was extremely large. At the peak of the storm (minimum in Dst (disturbance with storm time) and midnight boundary indices) the auroral particle precipitation extended down to magnetic latitudes of 40.1° or L = 1.71 while the polar edge of the auroral zone expanded poleward only slightly. The storm was also a period of intense, hemispherically symmetric polar rain fluxes. The auroral electric field was clearly observed down to magnetic latitude of 35°. This is consistent with the auroral electrojet (AE) current density and the AE index having a saturation level beyond which the index will increase slowly or not at all as more energy is transferred from the solar wind to the magnetosphere, but the cross polar-cap potential during this storm shows no evidence of saturation. There are only two visible light images from DMSP available near the peak of the storm. These images and one UV image from the Dynamics Explorer (DE) satellite at approximately the same time show the distribution of the aurora just after the peak of the storm. Comparison of the DMSP particle data with the DE-1 UV image indicates that the bifurcation of the auroral luminosity in the UV image is probably an effect of the DE-1 UV instrument's sensitivity limits; the DMSP data show no evidence for bifurcation of the auroral zone.
Intermittency and particle correlations
Authors: Brodeur A. , Kiang D. , Young K.
Published: April 2011

This is an analysis of the extent to which simple and general mechanisms explain the intermittent behavior observed in particle production. It is shown that a model based on simple particle correlations (with no fractal structure) can generate intermittency exponents similar to those observed experimentally and account for their collision-type dependence in a unified manner.
Contributions to the electron affinity of calcium and scandium
Authors: Fischer Charlotte Froese , Brage Tomas
Published: April 2011

Theoretical predictions of the electron affinity of Ca vary from 0 to 130 meV. Not all calculations have included the same effects. In this paper, the different approaches are reviewed, the effect of assumptions estimated whenever possible, and some new ab initio results reported that estimate the effect of core polarization on electron affinity for both Ca and Sc. For the latter our predicted electron affinity is in good agreement with the experimental value for the lowest 4s23d4p1D state and underestimates the electron affinity for 4s23d4p3D, where the calculation of outer correlation is more demanding and the core-polarization effect is small.
Pulse compression, shaping, and pedestal suppression using a nonlinear twin-core fiber in a loop configuration
Authors: Essiambre R. J. , Vallée R.
Published: April 2011

We propose a new fiber device, involving a nonlinear twin-core fiber in a fiber-loop reflector configuration, achieving several all-optical operations. By varying the disperson parameter β2, we generate quasi-square pulses in the positive dispersion regime and produce compressed and pedestal-free pulses (in one pass) in the anomalous dispersion regime. The stability of these phenomena under a change of β2 is also studied. A scale invariance is derived that permits operation of the device at any desired value of β2 simply by changing its length.
Femtosecond pulses from the ultraviolet to the infrared: Optical parametric processes in a new light
Authors: Driel H. M. van , Mak G.
Published: April 2011

Although the optical parametric oscillator (OPO) is more than 25 years old, it has not seen widespread use unlike other tunable sources such as the dye laser. Part of the reason for this is the low-gain – high-threshold associated with the weak conversion mechanism in the nonlinear optical crystals. Pump lasers with high peak intensities are usually required, which, unfortunately, run the risk of damaging the crystals, especially if their pulse duration is nanoseconds or picoseconds. Recently, however, the emergence of new, more efficient, nonlinear crystals and the development of continuously mode-locked, solid-state lasers, such as the Kerr-lens mode-locked Ti:sapphire laser, has led to a renaissance for OPOs. For example, the Ti:sapphire laser with an average power of over 1 W, with pulses [Formula: see text] long at a 100 MHz repetition rate, has allowed us to construct a stable, low-noise, synchronously pumped OPO. The output pulses are as short as 60 fs and can be produced in the wavelength range from 1 to 4 μm with average power as high as 200 mW. Harmonic generation of the OPO or the Ti:sapphire laser beams provides wavelength coverage from 200 nm to 4 μm. Through difference-frequency-mixing of the two output beams of the OPO in chalcopyrite or proustite crystals we anticipate being able to generate femtosecond pulses at wavelengths from 200 nm to beyond 20 μm. This broad-band, stable light source will open up new areas of investigation in physics, chemistry, and engineering.
Mise au point d'une méthode de détermination de la température moyenne de la mésosphère à partir de la mesure de la vitesse de phase des ondes longues sur un trajet grande distance
Authors: Ayachi M.
Published: April 2011

The.mechanism of the Lyman α ionization of nitric oxide, which is mainly responsible for the formation of the D region, the lowest part of the ionosphere, is first briefly reviewed. From equations of the photochemical equilibrium, a model of the height distribution of the electron density is proposed as a function of the solar angle Θ and the scale height H, which is a function of the mesospheric temperature T. A method named Geoscanner based upon a set of curves that illustrate the theoretical relations between the phase of a continuous VLF radio wave for a long-distance transmission and the different parameters of the daytime atmosphere is described. This method is applied to analyse experimental data obtained by phase measurements for the 10.2 kHz transmission Trelew (Argentina) – Caen (France), nearly 12 000 km distant. It provides a mean value of the mesospheric temperature that is a characteristic of the studied path and day. The significance of such an integrated temperature, ranging between 190 and 200 K, is discussed.
CARS (coherent anti-Stokes Raman scattering) investigations of the intermolecular vibrational energy transfer between nitrogen and carbon dioxide molecules
Authors: Wang L. , Xu J. R. , Jones W. E.
Published: April 2011

The CARS (coherent anti-Stokes Raman scattering) technique has been used for the first time to observe directly the vibrational energy transfer between nitrogen N2 (X1Σ, ν = 1, 2) and carbon dioxide. The transfer-rate constants were determined as (1.0 ± 0.1) × 1011 cm3 mol−1 s−1 and (1.7 ± 0.4) × 1011 cm3 mol−1 s−1 for N2(ν = 1) and N2(ν = 2), respectively.
The effect of H on a-SiNx prepared by ion-beam-assisted reaction deposition
Authors: Zhang S. , Brodie D. E.
Published: April 2011

a-SiNx:H films have been prepared using ion-beam-assisted deposition and source gases of NH3, or N2 + NH3 gas mixtures. Some optical and electrical properties were compared with those of nonhydrogenated a-SiNx films, prepared using pure N2 as the ion source gas. H can significantly alter the a-SiNx:H film properties, but the effects are different, depending on the source gas used. a-SiNx:H films, prepared using NH3 ion beams exhibit activated conductivities, are photoconducting and display photoconductivity fatigue effects. For the same N concentrations, the decay of a-SiNx:H is faster than that of a-SiNx. This could be due to an indirect role for H, i.e., its effect on the recombination centre density. a-SiN0.82:H prepared with an NH3 + N2 gas mixture contains more N—H bonds than Si—H bonds, and this is opposite to that found in a-SiNx:H, made using an ammonia ion beam. Even though the N concentrations and the total H concentrations are kept fairly constant in this group of films, the electrical activation energies, optical gaps and conductivities are different. The results suggest that the Si—H bond is more important than the N—H bond in determining the film properties for Si-rich films. The photoconductivities for the group of films made with the gas mixture are lower than those observed for a-SiNx:H films prepared with NH3 alone. In addition, the mixing of NH3 with N2 for the ion source reduces both the optical gaps and the activation energies, and increases the dark conductivities of the films for the same N concentration, when a lower NH3/(NH3 + N2) gas ratio is used.
Hypervirial perturbation calculations for double-well potentials of perturbed oscillator type
Authors: Witwit M. R. M. , Killingbeck J. P.
Published: April 2011

The renormalized hypervirial perturbation method is used to compute the energy levels for a double-well potential V(x) = −Z2x2 + x2J. Results are produced for a wide range of parameters [Formula: see text] and of state numbers [Formula: see text]. Comparison is made with results obtained by other means.
Depth profiling of the C/Si interface
Authors: Danailov D. M. , Miteva V. , Littmark U.
Published: April 2011

Auger profiles analysis is performed on thin carbon films deposited on silicon substrates (a-C:D/Si) using a 5 keV Xe+-ion beam. Stability of the interface is observed after annealing at different temperatures. The profiling is modeled by means of a Monte-Carlo dynamic computer code. A comparison is made of the mixing of the layers for profiling with different primary ions: the heavy Xe+ and the commonly-used Ar+.
A continuum approximation of the rare-gas liquids
Authors: Mohazzabi P. , Popadic Timothy H.
Published: April 2011

Potential energies and the number of nearest neighbors in liquid neon, argon, krypton, and xenon are calculated using a continuum approximation and the Lennard–Jones potential energy function. The number of nearest neighbors obtained in this way compare very well to those obtained from the neutron diffraction data. The potential energies are used to calculate the latent heat of fusion for these elements, which are in excellent agreement with the experimental data in all cases.
Constrained Hamiltonian systems on Lie groups, moment map reductions, and central extensions
Authors: Harnad J.
Published: April 2011

The canonical symplectic structure on the cotangent bundle T*G of a Lie group, whose algebra gc admits a central extension gc, is modified so that the moment map associated to right translations generates a representation of gc. Zero moment map constraints are applied to a class of Hamiltonian systems on T*G that are not necessarily right invariant to yield reduced systems on coadjoint orbits in gc*. The Hamiltonian formulation of the WZW model is developed as an example in which G = LG0 is a loop group and the reduced space is the group of based loops ΩG0, identified as a coadjoint orbit of the affine Kac–Moody algebra [Formula: see text]. An extension of the geometric quantization method leads to representations of [Formula: see text] on Hilbert spaces of sections of holomorphic vector bundles over ΩG0.
Construction of higher local (2 + 1) dimensional exponential lattice equations
Authors: Levi D. , Ragnisco O. , Shabat A. B.
Published: April 2011

It is shown that the 2-dimensional Toda equation can be decomposed into two integrable differential-difference equations, thus implying that we can associate to it a triad of linear problems. Using this same trick we construct new 2-dimensional differential-difference equations with exponential interactions.
Compositional dependence of thin films of BiPbSrCaCuO on target to substrate distance
Authors: Murdoch J. , Razavi F. S. , Moore J. A.
Published: April 2011

Using magnetron sputtering techniques, several thin films of superconducting BiPbSrCaCuO were fabricated by varying the distance between the substrate (single crystal of MgO with polished (100) plane) and the targets. During the deposition the gas pressure was kept constant at 0.3 mbar (1 mbar = 0.1 kPa) and the substrate temperature was kept at 700 °C. An energy-dispersive X-ray fluorescence was designed using a radioisotope source with a secondary target and a Si(Li) X-ray spectrometer and it was used to measure the atomic composition of the film quantitatively. It was found that the Ca concentration relative to Sr increases linearly as the distance between the substrate and the targets increases. However, both Cu and Bi show a more complex variation of concentration with distance. The X-ray diffraction results also indicated that the films are grown epitaxially along the C axis, which showed a semiconducting behaviour with TC,zero below 60 K.
Phenomenological approach to the viable nonmetric relativistic scalar 4-vector theory of gravitation
Authors: Vlasov Alexander A.
Published: April 2011

Contrary to the hypothesis that every viable theory of gravitation must be the metric one, this paper presents the example of nonmetric relativistic gravitational theory on the basis of Minkowski space-time, where the gravitation is described by a mixture of the nonlinear scalar field and the linear 4-vector field, compatible with all the known post-Newtonian gravitational tests, with tests on gravitational radiation from binary pulsar PSR 1913 + 16 and with the ordinary cosmological notions.
Measurement of the behaviour of high-purity copper at very high rates of strain
Authors: Kamler Frank , Niessen P. , Pick R. J.
Published: April 2011

Published measurements describing the high strain rate constitutive behaviour of oxygen-free high-conductivity (OFHC) and commercially pure copper are limited and show considerable scatter. To provide additional data, a direct impact compressive split Hopkinson bar was miniaturized to utilize specimens, 640 μm in diameter and 686 and 292 μm in length. This paper describes the design of this apparatus and results for OFHC copper. Good agreement is shown with results from pressure shear plate impact experiments.
A high-pressure technique for determining the microcrack porosities of damaged brittle materials
Authors: Schmitt Douglas R. , Li Yong Yi
Published: April 2011

The microcrack porosity of a damaged brittle material is found by accurately measuring the compressibilities under a hydrostatic pressure to 200 MPa. Crack apertures are sensitive to the stress applied normal to their plane and, as a result, at low confining pressures the bulk of the strain records the response of the progressive closure of these cracks. At higher pressures when much of the microcrack porosity is closed the observed strains are nearly the same as that expected for the solid compounds within the rock. The higher pressure response may then be used to estimate the expected solid strains that are removed from those observed to leave that portion of the strain due to microcrack porosity. This procedure differs from that of other workers who either ignore the portion of the strain due to intrinsic compression or account for it indirectly by taking the derivative of the observed strain curves. The final results may be analyzed in tensor form to show possible anisotropies in microcrack orientations within a given sample. An example of the experiment on a rock sample that was damaged during removal from the earth by drilling yielded a microcrack porosity of 0.79%, which was a substantial fraction of the total porosity near 5%. At 200 MPa, the principal crack strains had magnitudes of 1.86, 2.61, and 3.39 mstrains; the orientation of this last and greatest magnitude strain differing from the vertical direction by approximately 20°. This suggests that the planes of the predominant family of microcracks within the test piece were subhorizontal. This suggests that a portion of the microcracks result from drilling-induced damage and not solely from stress relief of the sample upon removal from the earth.
Infrared finiteness of the two-loop correction to the Chern–Simons term in the Yang–Mills–Chern–Simons theory
Authors: Kao Yeong-Chuan , Li Hsiang-Nan
Published: April 2011

We show that the two-loop contribution to the coefficient of the Chern–Simons term in the effective action of the Yang–Mills–Chern–Simons theory is infrared finite in the background field Landau gauge. We also discuss the difficulties in verifying the conjecture, due to topological considerations, that there are no more quantum corrections to the Chern–Simons term other than the well-known one-loop shift of the coefficient.
Deflection angle of a massless particle under Reissner–Nordström's metric
Authors: Do-Nhat T.
Published: April 2011

The perturbation method of Pointcaré and Lindstedt has been used to find the asymptotic expression of a massless particle under the Reissner–Nordström metric. From this analytical expression, the deflection angle of a massless particle is expressed as a rapidly convergent power series of a perturbation parameter, whose leading term is the well-known Einstein deflection angle. This power series was verified in two limiting cases in which the charge parameter or the Schwarzschild radius tends to zero.
A Hill-determinant approach to symmetric double-well potentials in two dimensions
Authors: Witwit M. R. M. , Killingbeck J. P.
Published: April 2011

Energy levels of the Schrödinger equation for a double-well potential V(x,y;Z2,λ) = −Z2[x2 + y2] + λ[axxx4 + 2axyx2y2 + ayyy4] in two-dimensional space are calculated, using a Hill-determinant approach for several eigenstates and a range of values of λ and Z2. Special emphasis is placed on the larger values of Z2, for which the eigenvalues for different states have almost degenerate eigenvalues.
Galactic cosmic-ray modulation effect by solar-wind streams
Authors: El-Borie M. A.
Published: April 2011

Data, from the worldwide network of neutron monitors, recorded at Deep River, Hermanus, Rome, Tokyo, and Huancayo, over two solar cycles (Nos. 20 and 21) are analyzed to study the long-term variations of the solar diurnal variations as they relate to solar-wind speed. The median primary rigidities of response (Rm) for these detectors cover the range 16 GV ≤ Rm ≤ 33 GV. We discuss the solar diurnal variations (amplitude and phase) of cosmic rays as a function of solar activity. The behavior of solar diurnal phases is completely different for the two epochs of high-wind speed. Data of solar-wind speed from 1966–1986 are classified according to the state of the daily mean values. Variation in the amplitudes of the diurnal variations, as functions of the median primary rigidity of cosmic rays, for the two selected periods (1973–1975 and 1979–1981) of high and low solar-wind speeds were determined at the selected stations. The rigidity dependence of the averaged solar diurnal variations of cosmic rays related to the high solar-wind speed was studied. The most sensitive rigidity of modulation is around 20 and 30 GV during the 1973–1975 and 1979–1981 periods, respectively. Our results also show that there is a significant correlation in the solar diurnal amplitudes between the two divisions of high and low solar-wind speed days.
Pair-correlation function of an electron gas
Authors: Overhauser A. W.
Published: April 2011

The pair-correlation function p(0), at r = 0, of an electron gas is derived by a partial-wave, phase-shift analysis. The dependence of p(0) on rs, the radius of the sphere (in Bohr units) containing on average one electron, is found to be 32/(8 + 3rs)2. This analytic result, obtained with the help of a simplifying approximation, is compared with several numerical calculations. An improved formula is also derived. p(0) is an important parameter in theories of charge response or spin response whenever a perturbation, ~cos qx, has a small wave length, i.e., [Formula: see text]. Electron–electron scattering depends on both response functions and, consequently, also on p(0).
Single-color photoionization optogalvanic spectroscopy in U--Xe and U--Ne hollow-cathode discharges
Authors: Lévesque S , Gagné J -M , Babin F
Published: April 2011

Resonance ionization spectroscopy is a powerful tool used to study and identify highly excited states of atoms and molecules, but usually requires complex experimental setups. Recently, we described a new method for this spectroscopy based on previous work on the rapid optogalvanic effect. The optogalvanic photoionization spectroscopy method is particularly attractive as a replacement for the atomic beam when refractory elements are considered. As an illustration of the method, we measured the rapid optogalvanic spectra in U--Ne and U--Xe hollow-cathode discharges over the 16500--20500 cm-1 range, where we have identified about 900 lines. Although showing a larger density of lines, the rapid optogalvanic spectrum of UI reproduces the main characteristics of the resonant ionization spectra obtained in field-free low-pressure atomic uranium beams. Over 600 of the observed lines are interpreted as two or three photon photoionization transitions, from which we propose nearly 400 new highly excited levels of UI. Electric field and collision ionization of Rydberg states is also considered but is shown to play only a minor role.PACS Nos.: 32.30, 31.50, 32.80, and 52.70.
Solvation force in a hard-sphere fluid
Authors: Moradi M , Tehrani M Kavosh
Published: April 2011

The solvation force in a hard-sphere fluid is obtained by the denisty functional theory proposed by Rickayzen and Augousti. The direct correlation function (DCF) with the tail introduced by Tang and Lu is used. This DCF (hereafter TL DCF ) is postulated to hold the Yukawa form outside the hard core; and the generalized mean spherical approximation (GMSA) approach has been applied. The results are compared with those obtained by using the Percus-Yevick (PY) DCF. These results are also compared with those of Monte Carlo simulations. At low densities and fairly high densities the results are in agreement. But at high densities there is more oscillation in the solvation force obtained by using TL DCF in comparison with the PY DCF. There are no simulation results at high densities to be compared with these results.PACS No. 61.20
Analysis of self-boring pressuremeter (SBPM) and Marchetti dilatometer (DMT) tests in granite saprolites
Authors: Schnaid F , Ortigao J AR , Mántaras F M , Cunha R P , MacGregor I
Published: April 2011

This paper presents the analyses of the results of the site investigation programme carried out at the Kowloon Bay site in Hong Kong. The tests consisted of self-boring pressuremeter (SBPM), Marchetti dilatometer (DMT), and laboratory tests carried out in a granite saprolite, which can be described as a lightly cemented sand. The purpose of this research project is to stimulate the development of methods to interpret data obtained from tests in residual soils. In particular, the work aims to evaluate the analyses of the SBPM data through a curve-fitting technique. Both the loading and unloading portions of the SBPM curve were analysed and the results compared with those from other tests. The advantage of this analysis technique is the possibility of constructing a theoretical curve that reproduces a pressuremeter test from which a set of fundamental parameters can be derived, namely the friction angle, cohesion intercept, lateral stress, and shear modulus. The DMT proved to be a reliable tool that yielded good soil parameters at a small fraction of the cost of the other in situ tests.Key words: residual soil, in situ tests, pressuremeter, Marchetti dilatometer.
Mesure du module en petites déformations d'un sol autour d'une conduite enterrée : présentation d'un nouvel essai in situ
Authors: Thépot Olivier , Frank Roger
Published: April 2011

A new method of measurement of backfill stiffness around buried flexible pipe is presented. It consists of using flexible pipe as an expanding pressiometric probe. The pipe dilatation is obtained by an internal jacking test that causes a relatively small three-dimensional "ovalization" around 0.05%. We obtain a force-displacement curve along the force axis as well as the damping of the displacement in the longitudinal direction up to one diameter in range. Knowing the pipe mechanical characteristics, we can calculate Young's modulus of the backfill in the domain of small deformations. The paper describes the test procedure as well as the modulus computation technique, which is based upon a three-dimensional parametric study using the finite element method. The results obtained in a jacking test conducted on iron pipe of 1.4 m in diameter and 8.0 m in length are presented. The computed moduli are compared with the ones obtained in laboratory testing using resonant-column and cyclic triaxial tests.Key words: buried pipes, jacking test, soil stiffness, soil-structure interaction, three-dimensional analysis, finite elements.
Three-dimensional deformation behavior of the Taipei National Enterprise Center (TNEC) excavation case history
Authors: Ou Chang-Yu , Shiau Bor-Yuan , Wang I-Wen
Published: April 2011

The Taipei National Enterprise Center (TNEC) excavation project was constructed using the top-down construction method, in which a diaphragm wall was supported by the concrete floor slab. Previous studies have reported the deformation and stress-strain behaviors along the main observation section, which was considered to be in the plane strain condition. This paper examines the three-dimensional movements of the soil and wall through field observations and finite element analyses. The results indicate that the soil outside the excavation zone tends to move toward the excavation center. Such a tendency increases with excavation depth. The soil settlement near the corner of the excavation is less than that near the center due to the corner effect. The empirical equation proposed by Clough and O'Rourke for estimating the ground settlement appears to be adequate for plane strain sections and other non-plane strain sections. Numerical studies indicate that the wall deformation and ground surface settlement can be reasonably predicted using three-dimensional finite element analysis. Parametric studies revealed that for this case record zoned excavation commencing near the final stage of excavation has very little effect on excavation behavior.Key words: TNEC case history, deep excavation, deformation, three-dimensional finite element method.
Use of image analysis to study the microstructure of a failed sand specimen
Authors: Jang Deh-Jeng , Frost J David
Published: April 2011

The shearing of dilatant specimens of granular materials in the laboratory is often accompanied by the development of zones of more intense shearing. The nominal behavior of the specimens during this shearing condition is dictated by the behavior of soil particles inside the shear zones. To study the behavior of soil particles inside the shear zones, quantitative evaluation of the soil structure at the particulate scale is required. This paper describes the findings of a study that used digital image analysis to examine sand structure in a specimen where a shear zone formed. Evolution of the local void ratio distribution and changes in particle orientations within and adjacent to the shear zone were quantified.Key words: image analysis, sand, microstructure, shear, critical state.
Interpretation of in situ test results from the CANLEX sites
Authors: (Fear) Wride C E , Robertson P K , Biggar K W , Campanella R G , Hofmann B A , Hughes J MO , Küpper A , Woeller D J
Published: April 2011

One of the primary objectives of the Canadian Liquefaction Experiment (CANLEX) project was to evaluate in situ testing techniques and existing interpretation methods as part of the overall goal to focus and coordinate Canadian geotechnical expertise on the topic of soil liquefaction. Six sites were selected by the CANLEX project in an attempt to characterize various deposits of loose sandy soil. The sites consisted of a variety of soil deposits, including hydraulically placed sand deposits associated with the oil sands industry, natural sand deposits in the Fraser River Delta, and hydraulically placed sand deposits associated with the hard-rock mining industry. At each site, a target zone was selected and various in situ tests were performed. These included standard penetration tests, cone penetration tests, seismic downhole cone penetration tests (giving shear wave velocity measurements), geophysical (gamma-gamma) logging, and pressuremeter testing. This paper describes the techniques used in the in situ testing program at each site and presents a summary and interpretation of the results.Key words: CANLEX, in situ testing, shear wave velocity, geophysical logging, pressuremeter.
The CANLEX project: summary and conclusions
Authors: Robertson P K , (Fear) Wride C E , List B R , Atukorala U , Biggar K W , Byrne P M , Campanella R G , Cathro D C , Chan D H , Czajewski K , Finn WDL , Gu W H , Hammamji Y , Hofmann B A , Howie J A , Hughes J , Imrie A S , Konrad J -M , Küpper A , Law T , Lord E RF , Monahan P A , Morgenstern N R , Phillips R , Piché R , Plewes H D , Scott D , Sego D C , Sobkowicz J , Stewart R A , Watts B D , Woeller D J , Youd T L , Zavodni Z
Published: April 2011

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness resulting in substantial deformations. The intent of this paper is to compare, interpret, and summarize the large amount of field and laboratory data obtained for six sites in Western Canada as part of the CANLEX project. The sites are compared in terms of both flow-liquefaction and cyclic-softening considerations. The paper presents a number of conclusions drawn from the project as a whole, in terms of both fundamental and practical significance.Key words: sand, flow liquefaction, cyclic softening, CANLEX.
Phase and amplitude responses associated with the measurement of shear-wave velocity in sand by bender elements
Authors: Blewett J , Blewett I J , Woodward P K
Published: April 2011

Shear-wave velocity measured by bender elements in laboratory sand samples is shown to be dependent upon the excitation frequency and exhibits a maximum velocity for a finite frequency. By comparing the relative effects of dispersion due to propagation of shear waves through sand and dispersion due to bender element performance within sand, we show that a combination of the two processes is required to explain the observations. The magnitude of the aggregate response of the bender elements and the sand implies that reliable shear-wave velocity results cannot be obtained from bender element tests without a prior knowledge of the frequency response of the entire system.Key words: shear-wave velocity, phase-sensitive detection, dispersion, attenuation, sand.
Experimental investigations of the soil-water characteristics of a volcanic soil
Authors: Ng Charles WW , Pang Y W
Published: April 2011

Rain-induced landslides are common around the world. To analyse transient seepage and to predict pore-water pressure distribution in unsaturated slopes subjected to rainfall infiltration, it is essential to study soil-water characteristics and water permeability functions. The soil-water characteristic curve (SWCC) is a relationship between suction and water content or degree of saturation. Conventionally, only the drying soil-water characteristic curve of soil specimens is determined in a pressure-plate extractor without the application of any external stress. In this paper, the influences of initial dry density and initial water content, history of drying and wetting, soil structure, and the stress state upon the desorption and adsorption soil-water characteristics of a completely decomposed volcanic soil in Hong Kong are examined and discussed. The experimental results presented are obtained by using a conventional volumetric pressure-plate extractor and a newly modified one-dimensional stress-controllable pressure-plate extractor with deformation measurements. The SWCC of a recompacted specimen is very different from that of a natural specimen with the same initial soil density and initial water content. The SWCC of the recompacted specimen is highly dependent on the history of drying and wetting. The rates of desorption and adsorption are substantially higher at the first drying and wetting cycle than at the second drying and wetting cycle. The size of the hysteresis loop of the recompacted specimen is considerably larger than that of the natural specimens. The SWCC of soil is stress-state dependent. For recompacted specimens subjected to different stress states, the higher the applied stresses, the lower the rate of desorption and the smaller the size of the hysteresis loops. However, for natural specimens, the size of the hysteresis loops seems to be independent of the stress state. Under a higher applied stress, natural specimens exhibit lower rates of desorption and adsorption.Key words: volcanic soil, SWCC, drying and wetting, stress-state dependent.
Strain degradation of saturated clay under cyclic loading
Authors: Zhou Jian , Gong Xiaonan
Published: April 2011

Soil degradation is studied from the point of view of cyclic axial strain through stress-controlled triaxial tests on Hangzhou normally consolidated clay. Different influence factors on strain, such as cyclic stress ratio, overconsolidation ratio, and frequency, are studied. Degradation index is redefined according to the tests. A mathematical model for strain degradation is presented and verified.Key words: cyclic loading, saturated clay, strain degradation, mathematical model.
Effective stresses in a porous seabed of finite thickness: inertia effects
Authors: Jeng D S , Rahman M S
Published: April 2011

The evaluation of wave-induced pore pressure and effective stresses is an important factor in the design of offshore installations. However, to simplify a complicated problem, most previous investigations have ignored the effects of inertia forces. This paper presents a new semi-analytical solution to the equations governing the wave-induced seabed response, including inertia terms for the whole problem. The numerical results show that the inertia forces cannot always be ignored. The relative difference between the present solution (with inertia items) and the previous solution (without inertia items) may reach 17% of po under certain combinations of wave and soil conditions. Key words: inertia force, pore pressure, effective stresses.
Saline water intrusion adjacent to the Fraser River, Richmond, British Columbia
Authors: Neilson-Welch Laurie , Smith Leslie
Published: April 2011

During periods of average to low flow in the Fraser River, seawater from Georgia Strait migrates with a rising tide up the river channel, reaching distances up to 16 km from the river's outlet to the ocean. This relatively dense water infiltrates through the river bed and circulates as a stable wedge of saline water within permeable deltaic deposits adjacent to the river. At the Kidd2 site in Richmond, the wedge extends approximately 500 m inland from the river. The top of the transition zone between fresh and saline water is 10 m below ground surface. The bottom of the saline wedge is located at the contact with underlying low-permeability delta slope deposits, resulting in a wedge with a vertical extent of approximately 10 m. Maximum salinity values observed in the wedge (1617 parts per thousand) reflect the time-averaged response to density-driven flow under a complex sequence of daily and seasonal variations in salinity within the Fraser River and mixing with fresh river water that may enter the aquifer during the summer freshet. Under the assumption of dynamic equilibrium, simulation of the saline wedge at the Kidd2 site suggests (1) the effective, long-term average salinity at the base of the river channel is approximately 19 parts per thousand; (2) the velocity of groundwater, directed inland in the central portion of the wedge, is in the range from 0.5 to 6 m/year; and (3) fresh water in the confined deltaic sands moves from inland areas toward the Fraser River under a hydraulic gradient of approximately 3 × 104.Key words: salt water intrusion, deltaic sediments, modeling.
Influence of swelling on the microstructure of expansive clays
Authors: Katti Dinesh R , Shanmugasundaram Vijayakumar
Published: April 2011

The focus of this work is to elucidate the changes in microstructure during swelling in expansive clays. A new device to enable controlled swelling of clay samples was designed and fabricated. This controlled uniaxial swelling device when integrated with a closed loop mechanical testing load frame allowed for the measurement of swelling pressure at a controlled and predetermined extent of swelling of the expansive clay samples. Further, this cell offered ease of removal of samples for microanalytical testing in a scanning electron microscope. Microstructural analysis was performed on the bentonite samples after the saturated samples were allowed to swell 0, 50, and 75% beyond their original volume. The void and particle gray scales were identified in the images using energy-dispersive X-ray analysis. Digital analysis of the images using custom-developed macros and Scion ImageTM software shows that the increase in swelling and reduction of swelling pressure due to swelling in the clay samples result in appreciable reduction in particle size. Thus, the swelling results in a breakdown of the clay agglomerates into smaller sized particles. These effects of swelling on microstructure of swelling clays could have a significant impact on stress deformation and the hydraulic properties of the clay.Key words: expansive clays, swelling, swelling pressure, microstructure, image analysis, scanning electron microscopy.