Isochronal Data Research Articles

Using Isochronal Test Data for the Determination of the Flow Capacity for Gas Wells Using Different Methods: Case Study of Faregh Oilfield Libya.

Using Isochronal Test Data for the Determination of the Flow Capacity for Gas Wells Using Different Methods: Case Study of Faregh Oilfield Libya.

Deuterium diffusion in γ-LiAlO2 pellets irradiated with He+ and D2+ ions

Sequential irradiations of polycrystalline γ-LiAlO2 pellets were performed at 573 K with He+ and D2+ ions to overlap the deuterium (D) profile with the He+ ion damage peak. The D depth profiles were measured using time-of-flight secondary ion mass spectrometry before and after thermal annealing steps. A linear concentration gradient approximation model is proposed to estimate the diffusion coefficient. The combined isothermal and isochronal data are used to determine the activation energy for D migration. At and above 1 × 1017 He++D+/cm2, a double-peak structure in the D profile is observed probably due to isotope exchange reactions with H2O and H2. The D diffusion coefficient in the irradiated γ-LiAlO2 pellets is on the order of 10−12 cm2/s at 773 K for the first 2 min annealing and the average values between 5 and 60 min tend to decrease to 10−13 or 10−14 cm2/s, depending on the ion fluence. The activation energy for D migration is determined to be 1.0 ± 0.3 eV at 2 × 1016 He++D+/cm2 and 0.6 ± 0.3 eV at 1 × 1017 He++D+/cm2. The results from this study may help better understand and predict tritium diffusion behavior during neutron irradiation of γ-LiAlO2 pellets.

Isochronal Annealing of Electron-Irradiated Tungsten Modelled by CD Method: 1D and 3DModel of SIA Diffusivity

The evolution of the microstructure of tungsten under electron irradiation and post-irradiation annealing hasbeen modeled using a multiscale approach based on Cluster Dynamics simulations. In these simulations, bothself-interstitials atoms (SIA) and vacancies, carbon atoms isolated or in clusters, are considered. Isochronal annealing has been simulated in carbon free tungsten and tungsten with carbon, focusing on the recovery stages I and II. The carbon atom, single SIA, single vacancy and vacancy clusters with sizes up to four are treated as the mobile pieces. Their diffusivities as well as the energy formation and binding energies are based on the experimental data and ab initio predictions and some of these parameters have been slightly adjusted, without modifying the interaction character, on isochronal annealing experimental data. The both models with assumption on 1D as well as 3D dimensionality of diffusivity of SIA are treated. The advantage of the model with 1D diffusivity of SIA is found.

Effects of repeated biaxial loads on the creep properties of cardinal ligaments

The cardinal ligament (CL) is one of the major pelvic ligaments providing structural support to the vagina/cervix/uterus complex. This ligament has been studied mainly with regards to its important function in the treatment of different diseases such as surgical repair for pelvic organ prolapse and radical hysterectomy for cervical cancer. However, the mechanical properties of the CL have not been fully determined, despite the important in vivo supportive role of this ligament within the pelvic floor. To advance our limited knowledge about the elastic and viscoelastic properties of the CL, we conducted three consecutive planar equi-biaxial tests on CL specimens isolated from swine. Specifically, the CL specimens were divided into three groups: specimens in group 1 (n = 7) were loaded equi-biaxially to 1 N, specimens in group 2 (n = 8) were loaded equi-biaxially to 2N, and specimens in group 3 (n = 7) were loaded equi-biaxially to 3N. In each group, the equi-biaxial loads of 1N, 2N, or 3N were applied and kept constant for 1200s three times. The two axial loading directions were selected to be the main in-vivo loading direction of the CL and the direction that is perpendicular to it. Using the digital image correlation (DIC) method, the in-plane Lagrangian strains in these two loading directions were measured throughout the tests. The results showed that CL was elastically anisotropic, as statistical differences were found between the mean strains along the two axial loading directions for specimens in group 1, 2, or 3 when the equi-biaxial load reached 1N, 2N, or 3N, respectively. For specimens in group 1 and 2, no statistical differences were detected in the mean normalized strains (or, equivalently, the increase in strain over time) between the two axial loading directions for each creep test. For specimens in group 3, some differences were noted but, by the end of the 3rd creep test, there were no statistical differences in the mean normalized strains between the two axial loading directions. These findings indicated that the increase in strain over time by the end of the 3rd creep test were comparable along these directions. The greatest mean normalized strain (or, equivalently, the largest increase in strain over time) was measured at the end of the 1st creep test (t=1200s), regardless of the equi-biaxial load magnitude or loading direction. Mean normalized strains during the 2nd and 3rd creep tests (t = 100, 600, and 1200s), along each loading direction, were not statistically different. Isochronal data collected at 1N, 2N, or 3N equi-biaxial loads indicated that the CL may be a nonlinear viscoelastic material. Overall, this experimental study offers new knowledge of the mechanical properties of the CL that can guide the development of better treatment methods such as surgical reconstruction for pelvic organ prolapse and radical hysterectomy for cervical cancer.

Changing the Tendency of Glass-Forming Liquid To Crystallize by Moving Along Different Isolines in the T–p Phase Diagram

Controlling crystallization and glass-forming tendencies of molecular liquids is of great scientific and practical importance. In the present work, we show that a lot can be learned regarding this process by introducing temperature and pressure as thermodynamic control variables. For the glass-forming liquid ketoprofen and its non-hydrogen bonded analogue, we have investigated changes in the crystallization rate along different isolines located in the two-dimensional T–p phase space. This has included isobaric (p = const), isothermal (T = const), and isochronal (τα = const) data. Our results reveal that the crystallization tendency of the investigated liquids can be tuned by moving along specific thermodynamic pathways. In particular, we highlight that among considered isolines the overall crystallization rate is the least affected by the density increase for the isochronal (T, p) state points. Interestingly, for various thermodynamic conditions with the same τα the estimated value of the thermodynamic driving force toward crystallization Δμ was found to be almost constant.

Color-center production and recovery in electron-irradiated magnesium aluminate spinel and ceria

Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV–visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F+ centers (neutral and singly ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in color-center formation were observed for the two crystal orientations. Using calculations from displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at room temperature. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200 °C with almost full bleaching at 600 °C. Activation energies (~0.3–0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub-band-gap absorption feature, which peaked at ~3.1 eV, was recorded for 2.5 MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections.

Transverse Compression of Tendons.

A study was made of the deformation of tendons when compressed transverse to the fiber-aligned axis. Bovine digital extensor tendons were compression tested between flat rigid plates. The methods included: in situ image-based measurement of tendon cross-sectional shapes, after preconditioning but immediately prior to testing; multiple constant-load creep/recovery tests applied to each tendon at increasing loads; and measurements of the resulting tendon displacements in both transverse directions. In these tests, friction resisted axial stretch of the tendon during compression, giving approximately plane-strain conditions. This, together with the assumption of a form of anisotropic hyperelastic constitutive model proposed previously for tendon, justified modeling the isochronal response of tendon as that of an isotropic, slightly compressible, neo-Hookean solid. Inverse analysis, using finite-element (FE) simulations of the experiments and 10 s isochronal creep displacement data, gave values for Young's modulus and Poisson's ratio of this solid of 0.31 MPa and 0.49, respectively, for an idealized tendon shape and averaged data for all the tendons and E = 0.14 and 0.10 MPa for two specific tendons using their actual measured geometry. The compression load versus displacement curves, as measured and as simulated, showed varying degrees of stiffening with increasing load. This can be attributed mostly to geometrical changes in tendon cross section under load, varying according to the initial 3D shape of the tendon.

Measurement of non-isothermal oxygen potentials in a Cu–Fe–Ca–S–O liquid during reduction of chalcopyrite in lime and carbon mixtures

The reduction of Indian chalcopyrite concentrates from the Ghatshila mines with carbon was studied in the presence of lime in the temperature range of 1123–1573 K. An attempt was made to determine the oxygen potential corresponding to the selective separation of two metals, copper and iron, during the reduction of chalcopyrite by carrying out electro-motive force (emf) measurements under isochronal heating rate conditions using an yttria-stabilised zirconia solid electrolyte cell with Cu/Cu2O as the reference electrode. The isochronal rate data for oxygen potential measurements were analysed by comparing them with the data from isothermal kinetics studies on the reduction of natural and synthetic chalcopyrite minerals in the above temperature range. The analyses of phases formed were carried out using the X-ray powder diffraction and scanning electron microscopic techniques, which showed the presence of a new quinary solid solution CIII phase. The solid solution phase CIII [Cu2S-CII(FeS⋅CaO)] forms as a result of mixing between the two rhombohedral lattices: high-temperature form of Cu2S and CII (FeO⋅CaS) compounds. The mechanism of reduction of chalcopyrite with carbon in the presence of lime is illustrated by the explanation of the role of the intermediate phases, CII, CIII and matte phases.

Annealing process of F- and F+-centers in Al2O3 single crystal induced by fast neutrons irradiation

F and F+ centers were produced in Al2O3 single crystal by fast neutrons (En>1.2MeV) irradiation at low fluence (4.4×1016 ncm−2). The evolution of defects intensity as a function of temperature and of time at 493, 623 and 823K was investigated by UV–visible spectrophotometry technique. It can be concluded from the analysis of isochronal and isothermal annealing data, that the F- and F+-centers annealing process is complex. At low annealing temperature (<473K), only F- to F+-center conversion process takes place. At higher temperature (>493K) the annealing is due to the superposition of several mechanisms with different activation energies. According to our results, the activation energies needed for both F- and F+-centers elimination are 0.2, 0.3 and 0.03eV for temperature range of 300–673K, 673–873K and >873K, respectively.

Growth kinetics of Cu2ZnSnS4 thin films and powders

The growth kinetics of Cu2ZnSnS4 thin films and powders was studied using in-situ synchrotron data. Isothermal and isochronal measurements were performed at the MCX beamline of the Elettra synchrotron (Trieste, Italy). Diffraction line profile analysis was used to follow the changes in the domain size distribution during isothermal measurements, and the change in the mean volume of the domains was studied using the Johnson-Mehl-Avrami equation. The growth was found to be diffusion controlled from small dimensions while the nucleation rate is temperature dependent. An activation energy of 210 kJ/mol could be estimated. In case of the isochronal data, the evolution of inverse of the integral breadth of the diffraction peaks in dependence on temperature was studied using the Ozawa and Šatava equations. The activation energy determined for the growth process is between 112(2) and 145(5) kJ/mol.

Dielectric studies of tetraaryl and triaryl polycarbonates and comparisons with bisphenol A‐polycarbonate

AbstractThe relative permittivity, loss, and breakdown strength are reported for a commercial sample of bisphenol A‐polycarbonate (comm‐BPA‐PC) and a purified sample of the same polymer (rp‐BPA‐PC) as well as for two new polycarbonates having low molecular cross‐sectional areas, namely a copolymer of tetraaryl polycarbonate and BPA‐PC (TABPA‐BPA‐PC) and a triaryl polycarbonate homopolymer (TriBPA‐PC). The glass transition temperatures of the new polymers are higher than the Tg of BPA‐PC (187 and 191 °C vs. 148 °C). Relative permittivity and loss measurements were carried out from 10 to 105 Hz over a wide temperature range, and results for the α‐ and γ‐relaxation regions are discussed in detail. For the α‐relaxation, the isochronal peak position, Tα, scales approximately with Tg. On the other hand, the peak temperature for the γ‐relaxation is approximately constant, independent of Tg. Also, in contrast to what is observed for α, γ exhibits a strong increase in peak height as temperature/frequency increases and a significant difference is found between Arrhenius plots determined from isochronal and isothermal data analyses. Next, the γ‐relaxation region for comm‐BPA‐PC and associated activation parameters show strong history/purity effects. The activation parameters also depend on the method of data analysis. The results shed light on discrepancies that exist in the literature for BPA‐PC. The shapes of the γ loss peaks and hence glassy‐state motions for all the polymers are very similar. However, the intensities of the TriBPA‐PC and TABPA‐BPA‐PC γ peaks are reduced by an amount that closely matches the reduced volume fraction of carbonate units in the two new polymers. Finally, for comm‐BPA‐PC, the breakdown strength is strongly affected by sample history and this is assumed to be related to volatile components in the material. It is found that the breakdown strengths for TriBPA‐PC and TABPA‐BPA‐PC are relatively close to that for rp‐BPA‐PC with the value for TriBPA‐PC being slightly larger than that for rp‐BPA‐PC or the value usually reported for typical capacitor grade polycarbonate. Finally, it is shown that the real part of the relative permittivity remains relatively constant from low temperatures to Tg. Consequently, based on the dielectric properties, TriBPA‐PC and TABPA‐BPA‐PC should be usable in capacitors to at least 50 °C higher than BPA‐PC. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Isochronal annealing of electron-irradiated dilute Fe alloys modelled by an ab initio based AKMC method: Influence of solute–interstitial cluster properties

The evolution of the microstructure of dilute Fe alloys under irradiation has been modelled using a multiscale approach based on ab initio and atomistic kinetic Monte Carlo simulations. In these simulations, both self interstitials and vacancies, isolated or in clusters, are considered. Isochronal annealing after electron irradiation experiments have been simulated in pure Fe, Fe–Cu and Fe–Mn dilute alloys, focusing on recovery stages I and II. The parameters regarding the self interstitial – solute atom interactions are based on ab initio predictions and some of these interactions have been slightly adjusted, without modifying the interaction character, on isochronal annealing experimental data. The different recovery peaks are globally well reproduced. These simulations allow interpreting the different recovery peaks as well as the effect of varying solute concentration. For some peaks, these simulations have allowed to revisit and re-interpret the experimental data. In Fe–Cu, the trapping of self interstitials by Cu atoms allows experimental results to be reproduced, although no mixed dumbbells are formed, contrary to the former interpretations. Whereas, in Fe–Mn, the favorable formation of mixed dumbbell plays an important role in the Mn effect.

An EPR study of native radiation-induced paramagnetic defects in sudoite (di–trioctahedral Al–Mg chlorite) from the alteration halo related to unconformity-type uranium deposits

Natural radiation-induced defects were identified in specimens of sudoite (Al–Mg di-trioctahedral chlorite) related to unconformity-type uranium deposits at the base of the Athabasca Group (Saskatchewan, Canada), using electron paramagnetic resonance (EPR) spectroscopy at X- and Q-band frequencies. X-band spectra indicate the presence of a main native defect, named the As-center, whose EPR signal is dominated by an axially distorted spectrum with apparent principal components as follows: g// = 2,051 and g⊥ = 2,005, and a secondary defect with apparent component g = 2,025. The study of oriented specimens shows that the main defect has its g// component perpendicular to the (ab) plane of sudoite. The As-center corresponds to an electron hole located on oxygen atoms of the structure and is likely associated with Si, according to the lack of hyperfine structure. The As-center in sudoite has EPR parameters similar to the A-center in kaolinite and dickite, and the Ai-center in illite. The saturation behavior of EPR spectra as a function of power demonstrates that native defects of sudoite are different from those known in other clays, such as kaolinite, dickite or smectite, but are similar to those of illite. The isochronal annealing data suggest that the main defect in sudoite is stable to more than 300°C. The corresponding defects characterized in sudoite may have the potential for tracing past radionuclide migration around unconformity-type uranium deposits.

Crystallization kinetics of Zr65Ag5Cu12.5Ni10Al7.5 glassy powders produced by ball milling of pre-alloyed ingots

Ball milling was employed to produce Zr65Ag5Cu12.5Ni10Al7.5 glassy powder from pre-alloyed mixtures of crystalline intermetallic compounds. Differential scanning calorimetry (DSC) in isochronal as well as in isothermal modes was used to study the thermal stability and the crystallization kinetics of the glassy powder. The activation energy for crystallization was calculated using isothermal and isochronal DSC data as well as from viscosity measurements, which lead to values of the activation energy ranging between 298 and 314 kJ/mol. Johnson–Mehl–Avrami analysis shows that the transformation is a diffusion controlled three-dimensional process and the crystallization proceeds with increasing nucleation rate at annealing temperatures within the super-cooled liquid region. To test the effectiveness of the glassy powder as reinforcement in Al-based metal matrix composites, bulk specimens consisting of pure Al powder blended with 50 vol.% of Zr65Ag5Cu12.5Ni10Al7.5 glassy powder were synthesized by powder metallurgy. Room temperature compression tests reveal that the strength increases from 155 MPa for pure Al to 235 MPa for the composite with 50 vol.% of glass reinforcement.

血管造影撮影装置搭載コーンビームＣＴの特徴

Angiographic cone-beam CT, called DynaCT by SIEMENS, is a 3D imaging tool reconstructed from projection data by a rotational C-arm with a flat panel detector. It can visualize low-contrast objects such as soft tissue or small vessels as well as high-contrast structures such as enhanced vessels or bone. We need to understand its image characteristics and dose distribution during 200 degree rotation around a patient. In this research, we evaluated fundamental characteristics and dose effectiveness for optimized clinical images. DynaCT, including soft tissue information and isochronal voxel data along the z-axis, could provide enough CT-like image quality for IVR use. In addition, evaluation of accumulated dose distribution helped us to predict and avoid the occurrence of radiodermatitis. Thus, DynaCT is useful as a support and navigation tool for IVR.

Evidence of native radiation-induced paramagnetic defects in natural illites from unconformity-type uranium deposits

This study presents the first unequivocal identification of natural radiation-induced defects in illites. Middle Proterozoic illites related to unconformity-type uranium deposits of Canada and Australia were studied using electron paramagnetic resonance (EPR) spectroscopy at X- and Q-band frequencies. The saturation behaviour of EPR spectra as a function of power demonstrates that native defects of illites are different from those known in other clays as kaolinite, dickite or smectite. Q-band spectra indicate the presence of several––at least two––native defects. The EPR signal is dominated by an axially distorted spectrum with apparent principal components as follows: g∥ = 2.032 and g⊥ = 1.993. The corresponding defect is named as Ai center. The study of oriented specimen confirms the strong anisotropy, and shows that the main defect has its g∥ component perpendicular to the (ab) plane of illite. These defects in illite correspond to electron holes located on oxygen atoms of the structure and likely associated to Si, according to the lack of hyperfine structure. The Ai center in illite has similar EPR parameters to the A center in kaolinite and dickite. The isochronal annealing data suggest that illite can be used as a dosimeter in the geosphere. However, the determination of half-life and activation energy of the Ai center requires additional work.

Practical Well Test Analysis of a Hydraulically Fractured Low Permeability Gas Reservoir: A Case History

The primary objective of hydraulic fracturing is to create a propped fracture with sufficient conductivity and length to amplify or at least optimize well performance of low permeability tight gas reservoir. The oil industry has suggested that hydraulically fractured tight gas wells performance is hindered significantly by non-Darcy flow effect.This work will present an investigation of non-Darcy flow effect to hydraulically fractured gas wells performance and provide the development, validation, and application of actual well test analysis for wells with a finite conductivity vertical fracture.Also, this work presents the results obtained in the study of actual post frac modified isochronal test data of gas wells intersected by a finite conductivity vertical fracture in a tight low permeability gas reservoir. In addition, the estimation of reservoir properties and fracture properties were carried out to construct a simple analytical model, which used for rate prediction.The effect of non-Darcy flow in fractures is clearly seen in the tests data and will lead to limiting production especially on higher chokes (after one inch). Therefore, non-Darcy effects should be considered in design of hydraulic fracture treatments, otherwise the design might be far from optimal

Analysis of rapid chain dynamics in isochronal dielectric measurements of polymers

Fast dynamics within the microwave frequency range (approximately gigahertz) in polymer systems as a function of temperature (in the range from 20 to 190 degrees C) were studied using high frequency dielectric spectroscopy. The frequency of radiation was varied from 0.5 to 18 GHz. The isochronal dielectric loss data were taken to eliminate the complexity arising from the frequency-independent, temperature-dependent background loss in the condensed phase. These studies were conducted for poly(caprolactone) (PCL), poly(ethylene oxide) (PEO), poly(ethylene oxide) with methoxy end group (PEO-CH3), PLA-b-PEO-b-PLA triblock copolymers, and several polymers with high glass transition temperatures. These polymers possess glass temperatures ranging from -62 degrees C (PCL) to 110 degrees C (PMMA). One broad relaxation process was found only for polymers (PCL, PEO, and PLA-b-PEO-b-PLA) with low glass transition temperatures. The effect due to end groups was investigated by comparing the results of PEO with hydroxy versus methoxy end groups. The measured relaxation process was determined not to be associated with end groups. The results from temperature-dependent dielectric spectroscopy indicate that the relaxation process follows an Arrhenius T dependence suggesting that it is due to local motions. The activation energy of the relaxation process was measured and investigated based on the coupling model. The results suggest that the observed relaxation process behaves as a Johari-Goldstein beta relaxation.

Isochronal annealing studies in Pu and Pu alloys using magnetic susceptibility

The isochronal annealing of the low temperature accumulated damage from the radioactive decay of plutonium in α-Pu, δ-Pu 1− x Ga x ( x = 0.043) and δ-Pu 1− x Am x ( x = 0.224) was characterized using magnetic susceptibility. In each specimen, thermal annealing, as tracked by magnetic susceptibility, only commenced when T > 33 K and the magnetic susceptibility changes due to defects were fully annealed at T ∼ 300 K. The α-Pu magnetic susceptibility isochronal annealing data is similar to earlier measurements of resistivity characterized isochronal annealing. However, the δ-Pu 1− x Ga x ( x = 0.043) magnetic susceptibility isochronal annealing data, when compared with similar resistivity data, indicates that for this alloy magnetic susceptibility studies are more sensitive to vacancies than to the interstitials accumulated at low temperatures. The Pu 1− x Am x ( x = 0.224) alloy shows a remarkable change in properties, over a limited temperature range beginning where interstitial defects are first mobile, and characterized by an induced effective moment of order 1.1 μ B/Pu. This transient behavior may be evidence for a disorder driven low temperature phase transition, perhaps indicative of a compositional and structural proximity to a state possessing significant magnetic moments.

Effect of cationic size on gelation temperature and properties of gelatin hydrogels

Effect of Na +, K + and Ca 2+ on gel transition temperature ( T g) of gelatin hydrogels (5%, w/v) has been studied by oscillatory rheology in the salt concentration range I = 0.01–0.1 M, which showed increase in T g with salt concentration with the trend for T g showing Ca 2+ > K + > Na +. The dynamic light scattering (DLS) measurements in the sol state ( T > T g) showed two distinct relaxation modes whereas only a gel mode was observed in the gel state in all the samples which contained significant amount of heterodyne contribution. Low frequency (1.5 rad/s) isochronal storage modulus data revealed the formation of strong gel in presence of CaCl 2 compared to that of NaCl and KCl situations. The slow mode relaxation and heterodyne parameter obtained from DLS data indicate the presence of larger clusters in Ca 2+ gels.