bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the Influence of Heterogeneous Porosity on
Matrix Diffusion: a Novel Approach Using Adaptive Tree-Multigrid Technique
and Real Porosity Data
Authors: Simbierowicz P. , Olin M. 
Published: September 2012

ABSTRACTLast year we developed a two-dimensional deterministic heterogeneous matrix
diffusion model, which is capable of utilising porosity information
originating from real drill-core samples. The results of numerical
infiltration experiment we had performed with the model displayed
substantial spatial variations in the penetration depth. Because it is
practically impossible to verify experimentally those two-dimensional
penetration profiles we had computed, this time we decided to try modelling
of measured leaching curves. Unfortunately we have not succeeded in
acquiring such curves for the exact same samples, which we have used in
numerical leaching experiments. Nevertheless it can be seen, that the shape
of leaching curves computed with the heterogeneous model is clearly closer
to the shape of measured curves, than the shape of curves provided by the
standard model. These differences can be utilised as a basis for an
approximate numerical method of assessing the geometric factor, which has
traditionally been a purely empirical parameter.The results of the new numerical experiments agree with our older results
from last year: the heterogeneity of the rock matrix has highly significant
impact on the diffusion. However, when interpreting the results, one must
not neglect numerous limitations of the model, and hence, one should not
attempt to overgeneralise the conclusions.
A Note on Radionuclide Transport by Gas Bubbles
Authors: Neretnieks Ivars , Ernstson Märta-Lena 
Published: September 2012

ABSTRACTIn a repository for spent nuclear fuel, gas generated by corrosion of the
iron in the canister may form small bubbles that will escape and rise to the
ground surface. Colloidal particles may attach to the surface of the bubbles
and be carried by them. If the colloids are supplied by the montmorillonite
clay of the buffer material surrounding the canister, the clay can be
carried away. Nuclides sorbed in the clay can be carried with the bubbles.
We have estimated the carrying capacity of the gas of the clay particles and
the escape rate of nuclides carried by the gas bubbles. The latter is also
compared to the escape rate by the conventional escape mechanisms from the
near field. We have further estimated the detachment of the nuclides from
the clay and their sorption onto the fracture surfaces of the rock as well
as their uptake by diffusion into the rock matrix along the bubble transport
paths.The present paper is speculative and uses some hypothetical assumptions.
Although the processes that are modelled are known to exist there is not
enough known of several of them to quantify them accurately. The carrying
capacity of the gas used in the calculations is an upper bound and probably
very much exaggerated. Even so, the consequences are minor for the release
of radionuclides.
Waste Vitrification: Prediction of Acceptable Compositions in a
Lime-Soda-Silica Glass-Forming System
Authors: Gilliam T M. , Jantzen T. M. 
Published: September 2012

ABSTRACTA model is presented based upon calculated bridging oxygens which allows the
prediction of the region of acceptable glass compositions for a
lime-soda-silica glass-forming system containing mixed waste. The model can
be used to guide glass formulation studies (e.g., treatability studies) or
assess the applicability of vitrification to candidate waste streams.
Monte Carlo Simulation of Radioactive Contaminant Transport in
Fractured Geologic Media: Disorder and Long-Range
Correlations
Authors: Mukhopadhyay Sumit , Cushman John H. 
Published: September 2012

ABSTRACTThe geologic media near Yucca mountain site consist of fractured welded
tuffs along with less fractured unwelded tuff. Numerical simulation of flow
and transport in such media poses a number of challenging problems, due
mainly to the heterogeneities and disorder in the media. In addition,
because of different dominant transport mechanisms in different regions of
the media, investigations need to be carried out at different time-scales.
“Time-marching” will pose a considerable problem in analyzing such
multi-scale transient problems. We develop a field-scale network model of
fractures and study transport of radionuclides through geologic media as a
function of disorder and correlated fracture-permeabilities.
Diffusion of Technetium in Compacted Bentonites in the Reducing Condition with Corrosion Products of Iron
Authors: Kuroda Yuji , Idemitsu K. , Furuya H. , Inagaki Y. , Arima T. 
Published: September 2012

ABSTRACTIn the vicinity of a high-level waste repository, corrosion of carbon steel overpacks will create a reducing environment. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as technetium.The apparent diffusion coefficients of technetium were measured in compacted bentonites (Kunigel VI® and Kunipia F®, JAPAN) in contact with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients measured were 10-12to 10-13m2/s under oxidizing conditions and 10-12to 10-13m2/s under reducing conditions. There were significant effects of redox condition, dry density (0.2 to 2.3 g / cm3) and montmorillonite content (50% for Kunigel VI or 100% for Kunipia F) on the apparent diffusion coefficients. Montmorillonite density could be a good index to explain density dependence of the diffusion coefficients under both reducing and oxidizing conditions.
Detailed Description of a Long-Term Low-Level Waste Degradation
Experiment
Authors: Caron F. , Torok J. , Haas M. K. , Manni G. 
Published: September 2012

ABSTRACTThis work gives a detailed description of the important aspects of a
long-term Low-Level Radioactive Waste (LLRW) degradation experiment,
performed at Chalk River Laboratories (CRL). This experiment utilized actual
LLRW. The wastes consist of unconditioned compacted refuse (paper, mop
heads, paper towels, used clothing, etc), which represents the bulk of the
waste volume intended for near-surface disposal at CRL. Waste material was
collected and compacted to make a total of 11 bales for this experiment.
Each bale was then placed and sealed in separate steel containers which were
connected to sampling lines. After a dry monitoring period, water was added
to promote leaching and decomposition of the wastes. The leachate sampled
had a composition similar to landfill leachates. Some applications of this
experiment, used to support the safety case of near-surface disposal, are
briefly discussed in this paper, e.g., the production of colloidal material,
the nature and role of dissolved organics of microbial origin, etc.
Enumeration of Microbial Populations in Radioactive Environments by Epifluorescence Microscopy
Authors: Pansoy-Hjelvik M. E. , Strietelmeier B. A. , Paffett M. T. , Kitten S. M. , Leonard P. A. , Dunn M. , Gillow J. B. , Dodge C. J. , Villarreal R. , Triay I. R. , Francis A. J. 
Published: September 2012

ABSTRACTEpifluorescence microscopy was utilized to enumerate halophilic bacterial populations in two studies involving inoculated, actual radioactive waste/brine mixtures and pure brine solutions. The studies include an initial set of experiments designed to elucidate potential transformations of actinide-containing wastes under salt-repository conditions, including microbially mediated changes.The first study included periodic enumeration of bacterial populations of a mixed inoculum initially added to a collection of test containers. The contents of the test containers are the different types of actual radioactive waste that could potentially be stored in nuclear waste repositories in a salt environment. The transuranic waste was generated from materials used in actinide laboratory research. The results show that cell numbers decreased with time. Sorption of the bacteria to solid surfaces in the test system is discussed as a possible mechanism for the decrease in cell numbers.The second study was designed to determine radiological and/or chemical effects of239Pu,243Am,237Np,232Th and238U on the growth of pure and mixed anaerobic, denitrifying bacterial cultures in brine media. Pu, Am, and Np isotopes at concentrations of ≤1×10–5M, ≤5×10–6M and ≤5×10-4M respectively, and Th and U isotopes at concentrations of ≤4×10-3M were tested in these media. The results indicate that high actinide concentrations affected both the bacterial growth rate and morphology. However, relatively minor effects from Am were observed at all tested concentrations with the pure culture.
The Change in Bioavailability of Organic Matter Associatedwith
Clay-Based Buffer Materials as a Result of Heat Andradiation
Treatment
Authors: Stroes-Gascoyne S. , Haveman S. A. , Vilks P. 
Published: September 2012

ABSTRACTCompacted clay-based buffer surrounds corrosion-resistant waste containers
in the Canadian concept for nuclear fuel waste disposal. Clays naturally
contain small quantities of organic matter that may be resistant to
bacterial degradation. The containers with highly radioactive material would
subject the surrounding buffer to both heat (max. 95°C) and radiation (max.
52 Gy/h). Both could potentially break down complex organic material to
smaller, more bioavailable compounds. This could stimulate microbial growth
and possibly affect gas production, microbially-influenced corrosion or
radionuclide migration. Experiments were carried out in which buffer (50
wt.% Na-bentonite, 50 wt.% sand) was heated at 60 and 90°C for periods of 2,
4 and 6 weeks, in some cases followed by irradiation to 25 kGy. Unheated
buffer was also irradiated to 25 and 50 kGy at different moisture contents.
The treated materials were subsequently suspended in distilled water, shaken
for 24 h and centrifuged to remove the solids. The 0.22 μm filter-sterilized
leachates were inoculated with equal volumes of fresh groundwater and
incubated at room temperature for 10 d to determine the increase in total
and viable bacteria compared to a groundwater control. Results indicated
that leachates from buffer subjected to heat, radiation or combinations of
these, had a stimulating effect on both total and viable cell counts in
groundwater, compared to unamended groundwater controls. This stimulating
effect was generally most pronounced for viable counts and could be larger
than two orders of magnitude. Leachates from untreated buffer material also
stimulated the growth of groundwater bacteria, but to a lesser extent than
leachates from heat-and radiation-treated buffer material. The effects of
heat and radiation on nutrient availability in clay-based sealing materials
(at relevant clay/moisture ratios) should, therefore, be taken into account
when attempting to quantify the effects of microbial activity on vault
performance.
Imaging of Silicon Naphthalocyanine in Toluene
Authors: Becker R. J. , Goedert R. V. , Clements A. F. , Whittaker T. A. 
Published: September 2012

AbstractPulsed-laser shadowgraphs and images of scattered light are combined with limiting and scattering data to build a model of the response of silicon napthalocyanine (SiNc) at concentrations on the order of 10−3 M in toluene to 12–16 ns 532 nm laser pulses over an energy range from 10 nJ to 2 mJ. The inherent spherical aberration induced by the sample has a profound effect on the response. The scattering is extremely intense above pulse energies of 100 μJ. The data indicates the response at pulse energies below 300 mJ is due to reverse saturable absorption. Full absorbance is not observed until the agglomerates vaporize. At fluences approaching 1 J/cm2 a plasma begins to form and the liquid near the window starts to boil. Intense scatter from the boiling liquid combined with plasma absorption produces hard clamping.
Chitosan Gel Systems as Novel Host Materials for Optical Limiters
Authors: Jiang Hao , Su Weijie , Brant Mark , Tomlin David , Bunning Timothy J. 
Published: September 2012

AbstractTwo chitosan gel systems, chitosan/acetic anhydride and chitosan/glutaraldehyde, were studied as host materials for optical limiters. Both gels are transparent and have a very high laser damage threshold. The chitosan/acetic anhydride gel has a damage threshold > 540 J/cm2 while the chitosan/glutaraldehyde gel, which is slightly yellow in color, has a damage threshold > 600 J/cm2 (measurements made with 6.8 ns laser pulses at 532 nm). Different chromophore dopants, including porphyrin and CuPc, were tested. The optical limiting behavior of the guest/host gel systems was similar to their corresponding solution systems. The morphological structure of the gel systems was studied and the gelation process is discussed. Our current research explores the effect of gel morphology on the optical limiting properties of the chromophores and studies the relation between chromophores, cross-linking agents and the host materials. We have also investigated the relationship between optical properties and chemical structure of the gel/chromophore systems in order to optimize the optical behavior.
Optical Switching in Thin Film NdNiO3
Authors: DeNatale J. F. , Kobrin P. H. 
Published: September 2012

AbstractCrystalline thin films of NdNiO3 are known to exhibit characteristic metal-insulator electrical transitions. Infrared transmission measurements of these films have demonstrated the corresponding reversible optical switching response, transforming between IR-transparent and IR-opaque states. Their low-temperature transmission spectra exhibit a sharp increase in transmittance at an onset wavelength of approximately 3 mm (˜0.4eV), with an appearance suggesting formation of a distinct band gap structure. The transmission and reflection characteristics of these films differ significantly from those reported for bulk polycrystalline material.
Spatial and Temporal Characteristics of the Semiconductor to Metallic Phase Transition in VO2 Thin Films
Authors: Corbett Mark , Lewis Keith L , Pitt Andrew M 
Published: September 2012

AbstractVanadium dioxide exhibits a semiconductor to metallic phase transition at a temperature of about 68 °C. This can be exploited in the form of optical thin film structures which will exhibit non-linear behaviour when exposed to pulsed infra-red radiation. Since the phase transition is structural in nature, it is of interest to explore the temporal and spatial properties when irradiated with pulsed laser sources. Fast CMT detectors have been used to resolve nanosecond temporal detail on an experimental basis and the spatial charateristics have been explored using a simple adiabatic heating model. The dynamic transmission values measured for VO2 devices are complex combinations of the temporally and spatially varying characteristics of the film.
Semiconductor Infrared Nonlinear Optical Materials
Authors: Guha Shekhar , Jessen Gregg , Hood Patrick J. 
Published: September 2012

AbstractLarge values of the infrared nonlinearity make semiconductors important in many optical applications. Along with the two-photon absorption coefficient and free-carrier absorption cross-section, the values of the decay rates of the generated charge carriers control the nonlinear optical performance of semiconductors. In this paper, calculations of the limits of the charge carrier decay rates for five infrared materials are provided and some experimental results, performed in the long-wave and the mid-wave infrared wavelengths on three of these materials are presented. To the authors' best knowledge, this is the first report of measurement of optical nonlinearity of Hg0.65Cd0.35Te in the 4 -5 jtm wavelength range. Comparisons of room temperature and low temperature nonlinear optical behavior of all the materials studied are presented.
Nonlinear Optical Properties of Modified Carbocyanines
Authors: Tang Nansheng , Su Weijie , Cooper Thomas M. , McLean Daniel G. , Brandelik Donna M. , Sutherland Richard L. 
Published: September 2012

AbstractWe studied the optical nonlinearities of modified 3,3′-diethylthiadicarbocyanine iodides (X-DTDCI) in dimethyl sulfoxide (DMSO) solutions (X = H, Cl, Br at meso position) by a pump-probe technique with crossed polarized chirped laser pulses at room temperature. Reverse-saturable-absorption (RSA) with monoexponential lifetimes is observed at 532 nm in all the samples studied. We determined the effective excited-state absorption cross-sections and their lifetimes for all the samples investigated and found that they clearly correlate to the substituent X at the meso position. Empowered by the chirped pulses, a much faster nonlinearity with a decay time of ˜3.1 ps that is much shorter than the laser pulses used, is unveiled in Cl-DTDCI. We expressed both the absorptive and the refractive part of this fast nonlinearity as the equivalent molecular hyperpolarizability γ1212 and found γ1212 = (8.1 + i9.8) × 10−32erg−1.
Broad Band Optical Power Limiting in Vanadium Doped Cd0.55Mn0 45Te Crystals
Authors: Trivedi S. B. , Chen R. J. , Grasza K. , Kutcher S. W. , Nathan G. V. J. , Steier W. H. , Bacher David , Guha S. , Hood Patrick 
Published: September 2012

AbstractA variety of approaches have been used for optical limiting in the past [1–6].A relatively new approach, an electro-optic power limiter (EOPL) has a simple and compact design, wavelength agile sensitivity, the ability to respond to coherent as well as incoherent radiation, low threshold and a large field of view (up to 15°). EOPL devices allow the transmission of low intensity background radiation while simultaneously blocking the damaging high intensity beam. We have demonstrated EOPL in the past using the II-VI semiconductors CdTe:In [7,8], CdTe:V [9] and ZnTe [10]. In this paper, we are reporting on EOPL using a new ternary II-VI semiconductor Cdl-xMnxTe:V. Cd0.55Mn0.45Te is capable of limiting optical radiation from visible (0.630.tm) to near infrared (1.5pm) wavelengths, which covers the wavelength ranges of both CdTe and ZnTe combined. Additionally, crystals of Cd0.55Mn0.45Te are relatively easier to grow than ZnTe. We report our preliminary results of optical limiting in Cd0.55Mn0.45Te:V at 0.780μm, 0.895μm, and 1.06μm, and we discuss the materials issues involved in improving and optimizing Cd1-xMnxTe for electro-optic power limiting.
Hydrated Transition Metal Oxide Films for Reversible Switching in Near IR Region
Authors: Shiyanovskaya I. , Hepel M. 
Published: September 2012

AbstractElectro-optical properties of thin films of hydrated transition metal oxides, WO3 2(H2O) and WO3 1/3(H2O), have been investigated in situ using photoelectrochemical methods. These films can reversibly change their light absorption in the near IR region due to the double charge injection upon the applied electric field in electrolyte media. Taking into account the high stability and fast switching time, these hydrated tungsten oxide films can be utilized for efficient light modulation in the near infrared region of the spectrum.
Photorefractive Beam Fanning Optical Limiter
Authors: Miller M. J. , Wood G. L. , Salamo G. J. 
Published: September 2012

AbstractWe have investigated the potential for using photorefractive phenomena in optical limiting devices. The major obstacle preventing the photorefractive limiter from reaching this potential has been speed of response. In this paper we report on several techniques which are successful in enhancing the photorefractive beam fanning response time. In particular, we demonstrate and characterize the use of applied electric fields, gratings to seed the beam fan, and cylindrical focusing. We also report the first demonstration of a prototype beam fanning optical limiter encompassing many of the proposed improvements.
Optical Limiting in a Photorefractive Polymer
Authors: Grunnet-Jepsen A. , Thompson C. L. , Moerner W. E. 
Published: September 2012

AbstractOptical limiting has been suggested as a possible device application of high gain photorefractive (PR) polymers. The principle of operation relies on the existence of amplified scattering (beam fanning) to deplete the intensity of the incident coherent optical beam. The newest photorefractive polymers show a combination of high gain and reasonable speed, and we show how these materials behave as a beam fanning optical limiter and as a limiter based on self-pumped phase conjugation. A prototype cascaded beam fanning device is demonstrated and its salient features are discussed.
Effects of Varying Surfactants on the Electrooptical Switching Characteristics of Volume holograms recorded in PDLC'S
Authors: Tondiglia V. P. , Natarajan L. V. , Neal R. M. , Sutherland R. L. , Bunning T. J. 
Published: September 2012

AbstractThe effects of adding various chemical surfactants to the prepolymer syrup on the electro-optical switching properties of Bragg gratings recorded in polymer dispersed liquid crystals (PDLC's) have been studied. The gratings were holographically recorded in prepolymer recipes substituting hexanoic, heptanoic, propylpentanoic and octanoic acids as surfactants in the recipe. A small percentage of monomer containing an attached long chain alkyl group (vinyl neononanoate) was also used instead of a surfactant. The addition of surfactants resulted in lowering the required switching field from 17 V/μm with no surfactant to 1.5 to 8 V/μm at a concentration of about 6.7% by weight, depending on the surfactant. Field on response times for electrical switching decreased with the addition of surfactant, and off times increased.
Saturation Effects in Optical Limiters Utilizing Thick Nonlinear Media
Authors: Chapple P. B. , Hermann J. A. 
Published: September 2012

AbstractOptical Limiters which operate by exploiting nonlinear absorption and nonlinear refraction are most effective towards an incoming laser beam when the active material is somewhat thicker than one Rayleigh length. A variety of thick optical limiter configurations are described and modeled by appropriately integrating the formulas for thin nonlinear media with gaussian-shaped beams. The attenuating effects of linear losses are allowed for, and the approach is exact to the first order in optical power or irradiance. Irradiance-dependent and fluence-dependent absorbers are considered. For a gaussian-shaped input beam, we find that the combined effects of diffraction and nonlinear absorption produce, in the thick-medium limit, a transmitted beam which retains a gaussian-shaped profile at the far field, but which is now uniformly attenuated according to the magnitudes of the nonlinear and linear absorption parameters. This implies that the normalized transmittance is independent of the size of the receiving aperture. As the optical beam power increases the limiting behaviour saturates. We have discovered a simple saturation formula which agrees well with numerically calculated transmittances for thick irradiance-dependent absorbers within the strongly nonlinear regime. Under certain conditions this formula also describes the behaviour of refractive limiters, providing a simple and accurate technique for modeling limiters over a broad parameter range.
Broadband Optical Limiting and CCD Sensor Protection From Nanosecond-Pulsed Laser Threat With Reverse Saturable Absorbers
Authors: Dentan V. , Feneyrou P. , Soyer F. , Vergnolle M. , Barny P. Le , Robin Ph. 
Published: September 2012

AbstractWe study in detail the linear and nonlinear optical properties of a heavy metal substituted naphthalocyanine reverse saturable absorber (RSA). The excited states involved in the RSA process under nanosecond pulsed laser excitation in the visible are fully characterized. We then demonstrate that this material can be used as an efficient optical limiter for protecting silicium CCD arrays from destruction due to nanosecond-pulsed laser irradiation in the visible.