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MACHO RR lyrae stars in the galactic bulge: the spatial distribution

Description: We have analyzed a sample of 1150 type ab, and 550 type c RR Lyrae stars found in 24 bulge fields of the MACHO database. These fields cover a range in Galactocentric distances from 0.3 to 1.6 kpc. In combination with the data on the outer bulge fields of Alard (1997) and Wesselink (1987), here we present the surface density distribution of bulge RR Lyrae between 0.3 and 3 kpc. The distribution along the line of sight of the bulge RR Lyrae population was examined on the basis of the mean magnitudes, and it was shown that the bulk of the RR Lyrae population is not barred (Alcock et al. 1998). There is a hint of a bar only in the RR Lyrae of the inner fields closer to the Galactic center. The red giant clump stars in the MACHO fields, however, clearly show a barred distribution, confirming the results of previous studies (e.g. Dwek et al. 1995, Stanek et al. 1996). In the MACHO fields studied there are about 550 clump giants per RR Lyrae star. The RR Lyrae trace metal-poor stars, which are a minor component of the bulge population. The clump giants, however, should trace the bulk of the metal-rich population, foUowing underlying mass of the bulge more closely. Given the different spatial distribution, we concluded that the RR Lyrae and the clump giants trace two dif+erent populations (Alcock et al. 1998). The RR Lyrae would represent the inner extension of the Galactic halo in these fields (Minniti 1996). The observed surface distribution of RR Lyrae in the bulge fields was computed after discarding background RR Lyrae that belong to the Sgr dwarf galaxy (Alard 1996, Alcock et al. 1997). This distribution yields a power law density distribution. There is no turnover or flattening of this distribution ...
Date: August 1, 1997
Creator: Minniti, D.; Alcock, C. & Alves, D.
Partner: UNT Libraries Government Documents Department

Evidence for Distinct Components of the Galactic Stellar Halo from 838 RR Lyrae Stars Discovered in the LONEOS-I Survey

Description: We present 838 ab-type RR Lyrae stars from the Lowell Observatory Near Earth Objects Survey Phase I (LONEOS-I). These objects cover 1430 deg{sup 2} and span distances ranging from 3-30kpc from the Galactic Center. Object selection is based on phased, photometric data with 28-50 epochs. We use this large sample to explore the bulk properties of the stellar halo, including the spatial distribution. The period-amplitude distribution of this sample shows that the majority of these RR Lyrae stars resemble Oosterhoff type I, but there is a significant fraction (26%) which have longer periods and appear to be Oosterhoff type II. We find that the radial distributions of these two populations have significantly different profiles ({rho}{sub OoI} {approx} R{sup -2.26{+-}0.07} and {rho}{sub OoII} {approx} R{sup -2.88{+-}0.11}). This suggests that the stellar halo was formed by at least two distinct accretion processes and supports dual-halo models.
Date: February 23, 2007
Creator: Miceli, A; Rest, A; Stubbs, C W; Hawley, S L; Cook, K H; Magnier, E A et al.
Partner: UNT Libraries Government Documents Department

Book Review Geostatistical Analysis of Compositional Data

Description: Compositional data are represented as vector variables with individual vector components ranging between zero and a positive maximum value representing a constant sum constraint, usually unity (or 100 percent). The earth sciences are flooded with spatial distributions of compositional data, such as concentrations of major ion constituents in natural waters (e.g. mole, mass, or volume fractions), mineral percentages, ore grades, or proportions of mutually exclusive categories (e.g. a water-oil-rock system). While geostatistical techniques have become popular in earth science applications since the 1970s, very little attention has been paid to the unique mathematical properties of geostatistical formulations involving compositional variables. The book 'Geostatistical Analysis of Compositional Data' by Vera Pawlowsky-Glahn and Ricardo Olea (Oxford University Press, 2004), unlike any previous book on geostatistics, directly confronts the mathematical difficulties inherent to applying geostatistics to compositional variables. The book righteously justifies itself with prodigious referencing to previous work addressing nonsensical ranges of estimated values and error, spurious correlation, and singular cross-covariance matrices.
Date: March 26, 2007
Creator: Carle, S F
Partner: UNT Libraries Government Documents Department

Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise

Description: A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the weight percent of base and photo acid generator (PAG) were varied. A 6x increase in base weight percent is shown to reduce the size of successfully patterned 1:1 line-space features from 52 nm to 39 nm without changing deprotection blur. Corresponding isolated line-edge-roughness is reduced from 6.9 nm to 4.1 nm. A 2x increase in PAG weight percent is shown to improve 1:1 line-space patterning from 47 nm to 40 nm without changing deprotection blur or isolated LER. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photo generated acids in the resists that have been studied.
Date: June 1, 2008
Creator: Anderson, Christopher N.; Naulleau, Patrick P.; Niakoula, Dimitra; Hassanein, Elsayed; Brainard, Robert; Gallatin, Gregg et al.
Partner: UNT Libraries Government Documents Department

The Political Determinants of Fdi Location in Prchina, 1997-2009: Application of a New Model to Taiwanese Fdi in Mainland China

Description: This research seeks to identify the political determinants that account for the uneven geographical distribution of foreign direct investment (FDI) across Chinese counties. I compare the political determinants of Taiwanese FDI (TDI) and non-Taiwanese FDI site selection across counties in China. I focus on the central-local politics in China, especially the effect of county government autonomy on FDI and TDI site selection. I investigate whether the effect of county government autonomy and its interaction with TDI agglomeration varies across the three economic regions of China (i.e. eastern, central, and western regions). I argue that county government autonomy is critical to attracting inflows of FDI, and its impact is conditional on the existing level of FDI in a given county. Counties with higher autonomy are able to make greater commitments to and involvement in the market economy, have more flexibility to give preferential treatment to FDI and to improve the local investment environment. With the political burden that Taiwanese investors face from the special military and political relationship across the Strait, I argue that TDI is more sensitive to county government autonomy not only for the economic gains like other foreign investors but also for pursuing local protection against the political uncertainties from Beijing and the social instabilities of the local population. I also argue that county government autonomy’s impact on TDI inflow is strongest in the central region due to the less dominating role of the geographic and cultural advantages enjoyed by the eastern region and its better economic, cultural, political and geographic conditions that are lacking in the western region. Using the System General Method of Moment model to analyze the county level FDI/TDI panel data sets, I find autonomy’s impact on future FDI inflows fades with the increases in the existing level of FDI but gets stronger with ...
Date: August 2012
Creator: Lu, Kelan
Partner: UNT Libraries

Discovery of Non-random Spatial Distribution of Impacts in the Stardust Cometary Collector

Description: We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than {approx} 10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluated several hypotheses that could explain the observations. No hypothesis was consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low-angle oblique tracks. High-angle oblique tracks unambiguously originate from a non-cometary impact on the spacecraft bus just forward of the collector.
Date: April 6, 2007
Creator: Westphal, A J; Bastien, R K; Borg, J; Bridges, J; Brownlee, D E; Burchell, M J et al.
Partner: UNT Libraries Government Documents Department

Absolute bunch length measurements by incoherent radiation fluctuation analysis

Description: By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.
Date: September 29, 2008
Creator: Sannibale, Fernando; Stupakov, Gennady; Zolotorev, Max; Filippetto, Daniele & Jagerhofer, Lukas
Partner: UNT Libraries Government Documents Department

Algorithm for Rapid Tomography of Gas Concentrations

Description: We present a new computed tomography method, the low third derivative (LTD) method, that is particularly suited for reconstructing the spatial distribution of gas concentrations from path-integral data for a small number of optical paths. The method finds a spatial distribution of gas concentrations that (1) has path integrals that agree with measured path integrals, and (2) has a low third spatial derivative in each direction, at every point. The trade-off between (1) and (2) is controlled by an adjustable parameter, which can be set based on analysis of the path-integral data. The method produces a set of linear equations, which can be solved with a single matrix multiplication if the constraint that all concentrations must be positive is ignored; the method is therefore extremely rapid. Analysis of experimental data from thousands of concentration distributions shows that the method works nearly as well as Smooth Basis Function Minimization (the best method previously available), yet is 100 times faster.
Date: June 27, 2000
Creator: Price, P.N.; Fischer, M.L.; Gadgil, A.J. & Sextro, R.G.
Partner: UNT Libraries Government Documents Department

Meteorology-induced variations in the spatial behavior of summer ozone pollution in Central California

Description: Cluster analysis was applied to daily 8 h ozone maxima modeled for a summer season to characterize meteorology-induced variations in the spatial distribution of ozone. Principal component analysis is employed to form a reduced dimension set to describe and interpret ozone spatial patterns. The first three principal components (PCs) capture {approx}85% of total variance, with PC1 describing a general spatial trend, and PC2 and PC3 each describing a spatial contrast. Six clusters were identified for California's San Joaquin Valley (SJV) with two low, three moderate, and one high-ozone cluster. The moderate ozone clusters are distinguished by elevated ozone levels in different parts of the valley: northern, western, and eastern, respectively. The SJV ozone clusters have stronger coupling with the San Francisco Bay area (SFB) than with the Sacramento Valley (SV). Variations in ozone spatial distributions induced by anthropogenic emission changes are small relative to the overall variations in ozone amomalies observed for the whole summer. Ozone regimes identified here are mostly determined by the direct and indirect meteorological effects. Existing measurement sites are sufficiently representative to capture ozone spatial patterns in the SFB and SV, but the western side of the SJV is under-sampled.
Date: June 23, 2010
Creator: Jin, Ling; Harley, Robert A. & Brown, Nancy J.
Partner: UNT Libraries Government Documents Department

Eddy covariance observations of surface leakage during shallow subsurface CO2 releases

Description: We tested the ability of eddy covariance (EC) to detect, locate, and quantify surface CO{sub 2} flux leakage signals within a background ecosystem. For 10 days starting on 07/09/2007, and for seven days starting on 08/03/2007, 0.1 (Release 1) and 0.3 (Release 2) t CO{sub 2}d{sup -1}, respectively, were released from a horizontal well {approx}100 m in length and {approx}2.5 m in depth located in an agricultural field in Bozeman, MT. An EC station measured net CO{sub 2} flux (F{sub c}) from 06/08/2006 to 09/04/2006 (mean and standard deviation = -12.4 and 28.1 g m{sup -2} d{sup -1}, respectively) and from 05/28/2007 to 09/04/2007 (mean and standard deviation = -12.0 and 28.1 g m{sup -2} d{sup -1}, respectively). The Release 2 leakage signal was visible in the F{sub c} time series, whereas the Release 1 signal was difficult to detect within variability of ecosystem fluxes. To improve detection ability, we calculated residual fluxes (F{sub cr}) by subtracting fluxes corresponding to a model for net ecosystem exchange from F{sub c}. F{sub cr} had reduced variability and lacked the negative bias seen in corresponding F{sub c} distributions. Plotting the upper 90th percentile F{sub cr} versus time enhanced the Release 2 leakage signal. However, values measured during Release 1 fell within the variability assumed to be related to unmodeled natural processes. F{sub cr} measurements and corresponding footprint functions were inverted using a least-squares approach to infer the spatial distribution of surface CO{sub 2} fluxes during Release 2. When combined with flux source area evaluation, inversion results roughly located the CO{sub 2} leak, while resolution was insufficient to quantify leakage rate.
Date: April 1, 2009
Creator: Lewicki, J. L.; Hilley, G.E.; Fischer, M.L.; Pan, L.; Oldenburg, C.M.; Dobeck, L. et al.
Partner: UNT Libraries Government Documents Department

EXPERIMENTAL INVESTIGATION OF RELATIVE PERMEABILITY UPSCALING FROM THE MICRO-SCALE TO THE MACRO-SCALE

Description: The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements of interfacial area per volume. During this reporting period, we have shown experimentally and theoretically that the optical coherence imaging system is optimized for sandstone. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures that are statistically similar to real porous media has shown the existence of a unique relationship among these hydraulic parameters. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, has the same length-scale as the values of IAV determined for the two-dimensional micro-models.
Date: December 1, 2001
Creator: Cheng, JiangTao; Yu, Ping; Headley, William; Giordao, Nicholas; Mustata, Mirela; Chen, Daiquan et al.
Partner: UNT Libraries Government Documents Department

Gluon density in nuclei

Description: In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.
Date: October 1996
Creator: Ayala, A. L.; Ducati, M. B. G. & Levin, E. M.
Partner: UNT Libraries Government Documents Department

Assessment of the quantities and distribution of K East Basin floor sludge constituents

Description: Floor sludge constituent masses and their spatial distribution within K East Basin were calculated. This information will be beneficial in the assessing the acceptability of K Basin sludge in the Tank Waste Remediation System and in the design and/or operational practices related to retrieval and handling of this K Basin sludge. Calculations were made based on results from recent laboratory chemical and radionuclides analyses of sludge sampled from thirteen locations in K East main basin. This concentration data was mathematically processed to determine the various constituents concentration distribution throughout the basin floor. This data was further processed, along with data previously generated from the analysis of measured sludge depths, to give both basin total masses and associated spatial distribution of the various sludge constituents. Results of these calculations, showed that the major gravimetric constituents of the sludge are iron (1505 kg), uranium (1387 kg), aluminum, sodium and c2@15cium. Significant amounts of fissionable materials were also calculated: u (9.92 kg) and 239pU (3.42 kg). The calculated distribution of sludge constituent masses showed distinct patterns. Sludge constituent associated with corroded spent nuclear fuel were concentrated near the north-west corner of the basin. Aluminum and iron, and many other elements are mainly located near the mouth of the South Load Out Pit. A value of 10,200 Ci of alpha (5%) + beta (95%) radioactivity was calculated for the total basin floor sludge, and was concentrated near the north-west corner of the basin and near the Dummy Elevator Pit.
Date: October 1, 1996
Creator: Hecht, S.L.
Partner: UNT Libraries Government Documents Department

A tool for the quantitative spatial analysis of mammary gland epithelium

Description: In this paper we present a method for the spatial analysis of complex cellular systems based on a multiscale study of neighborhood relationships. A function to measure those relationships, M, is introduced. The refined Relative Neighborhood Graph is then presented as a method to establish vicinity relationships within layered cellular structures, and particularized to epithelial cell nuclei in the mammary gland. Finally, the method is illustrated with two examples that show interactions within one population of epithelial cells and between two different populations.
Date: April 9, 2004
Creator: Ortiz de Solorzano, Carlos & Fernandez-Gonzalez, Rodrigo
Partner: UNT Libraries Government Documents Department

Water structure as a function of temperature from X-ray scatteringexperiments and ab initio molecular dynamics

Description: We present high-quality X-ray scattering experiments on pure water taken over a temperature range of 2 to 77 C using a synchrotron beam line at the advanced light source (ALS) at Lawrence Berkeley National Laboratory. The ALS X-ray scattering intensities are qualitatively different in trend of maximum intensity over this temperature range compared to older X-ray experiments. While the common procedure is to report both the intensity curve and radial distribution function(s), the proper extraction of the real-space pair correlation functions from the experimental scattering is very difficult due to uncertainty introduced in the experimental corrections, the proper weighting of OO, OH, and HH contributions, and numerical problems of Fourier transforming truncated data in Q-space. Instead, we consider the direct calculation of X-ray scattering spectra using electron densities derived from density functional theory based on real-space configurations generated with classical water models. The simulation of the experimental intensity is therefore definitive for determining radial distribution functions over a smaller Q-range. We find that the TIP4P, TIP5P and polarizable TIP4P-Pol2 water models, with DFT-LDA densities, show very good agreement with the experimental intensities, and TIP4P-Pol2 in particular shows quantitative agreement over the full temperature range. The resulting radial distribution functions from TIP4P-Pol2 provide the current best benchmarks for real-space water structure over the biologically relevant temperature range studied here.
Date: March 1, 2003
Creator: Hura, Greg; Russo, Daniela; Glaeser, Robert M.; Head-Gordon,Teresa; Krack, Matthias & Parrinello, Michele
Partner: UNT Libraries Government Documents Department

A High Resolution Hydrometer Phase Classifier Based on Analysis of Cloud Radar Doppler Spectra.

Description: The lifecycle and radiative properties of clouds are highly sensitive to the phase of their hydrometeors (i.e., liquid or ice). Knowledge of cloud phase is essential for specifying the optical properties of clouds, or else, large errors can be introduced in the calculation of the cloud radiative fluxes. Current parameterizations of cloud water partition in liquid and ice based on temperature are characterized by large uncertainty (Curry et al., 1996; Hobbs and Rangno, 1998; Intriery et al., 2002). This is particularly important in high geographical latitudes and temperature ranges where both liquid droplets and ice crystal phases can exist (mixed-phase cloud). The mixture of phases has a large effect on cloud radiative properties, and the parameterization of mixed-phase clouds has a large impact on climate simulations (e.g., Gregory and Morris, 1996). Furthermore, the presence of both ice and liquid affects the macroscopic properties of clouds, including their propensity to precipitate. Despite their importance, mixed-phase clouds are severely understudied compared to the arguably simpler single-phase clouds. In-situ measurements in mixed-phase clouds are hindered due to aircraft icing, difficulties distinguishing hydrometeor phase, and discrepancies in methods for deriving physical quantities (Wendisch et al. 1996, Lawson et al. 2001). Satellite-based retrievals of cloud phase in high latitudes are often hindered by the highly reflecting ice-covered ground and persistent temperature inversions. From the ground, the retrieval of mixed-phase cloud properties has been the subject of extensive research over the past 20 years using polarization lidars (e.g., Sassen et al. 1990), dual radar wavelengths (e.g., Gosset and Sauvageot 1992; Sekelsky and McIntosh, 1996), and recently radar Doppler spectra (Shupe et al. 2004). Millimeter-wavelength radars have substantially improved our ability to observe non-precipitating clouds (Kollias et al., 2007) due to their excellent sensitivity that enables the detection of thin cloud layers and their ability to penetrate ...
Date: August 6, 2007
Creator: Luke,E. & Kollias, P.
Partner: UNT Libraries Government Documents Department

Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields

Description: Modification of the structure of materials at the nanoscale level is one goal of current nanoscience research. For example, by purposefully modifying the spatial distribution of adsorbates one could control the rate of chemical reactions on a local scale. Here we show how this can be accomplished in the case of H on Pd(111) through the application of local electric fields. Hydrogen adsorption on the platinum group metals is particularly interesting because these metals are used as catalysts in a variety of industrial processes, including hydrogenation and dehydrogenation reactions. Electric fields on surfaces are also of primary interest in electrochemistry where despite the considerable amount of experimental and theoretical work done to date, there still remains more work to be done before a clear understanding of phenomena at the atomic scale can be accomplished.
Date: May 10, 2007
Creator: Mitsui, T.; Fomin, E.; Ogletree, D.F.; Salmeron, M.; Nilekar,A.U. & Mavrikakis, M.
Partner: UNT Libraries Government Documents Department

Characterizing high energy spectra of NIF ignition hohlraums using a differentially filtered high energy multi-pinhole X-ray imager

Description: Understanding hot electron distributions generated inside hohlraums is important to the ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with the target materials. We used an array of 18 pinholes, with four independent filter combinations, to image entire hohlraums with a magnification of 0.87x during the hohlraum energetics campaign on NIF. Comparing our results with hohlraum simulations indicates that the characteristic 30 keV hot electrons are mainly generated from backscattered laser plasma interactions rather than from hohlraum hydrodynamics.
Date: May 11, 2010
Creator: Park, H; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J et al.
Partner: UNT Libraries Government Documents Department

First Quarter Hanford Seismic Report for Fiscal Year 2008

Description: The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 41 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, forty-four local earthquakes were recorded during the first quarter of fiscal year 2008. A total of thirty-one micro earthquakes were recorded within the Rattlesnake Mountain swarm area at depths in the 5-8 km range, most likely within the pre-basalt sediments. The largest event recorded by the network during the first quarter (November 25, 2007 - magnitude 1.5 Mc) was located within this swarm area at a depth of 4.3 km. With regard to the depth distribution, three earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), thirty-six earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and five earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, thirty-eight earthquakes occurred in swarm areas and six earth¬quakes were classified as random events.
Date: March 21, 2008
Creator: Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E. & Devary, Joseph L.
Partner: UNT Libraries Government Documents Department

An integrated approach to characterization of microbial exudates and investigation of their role in the spatial distribution and transformations of uranium at the mineral-microbe interface

Description: The long-term aim of this project was to understand the role of microbiota and their polymers (EPS) in controlling the distribution and fates of contaminants in subsurface environments. Additionally, this project also focused on the identification and characterization of extracellular proteins under a variety of growth conditions. Finally, this project sought to develop and advance the use of a variety of synchrotron-based hard-x-ray techniques to address a number of different ERSP elements.
Date: June 1, 2006
Creator: Kemner, K.M.; O'Loughlin, E.J.; Kelly, S.D. & Nealson, K.H.
Partner: UNT Libraries Government Documents Department

An Integrated Approach to Characterizing Bypassed Oil in Heterogeneous and Fractured Reservoirs Using Partitioning Tracers

Description: We explore the use of efficient streamline-based simulation approaches for modeling and analysis partitioning interwell tracer tests in heterogeneous and fractured hydrocarbon reservoirs. We compare the streamline-based history matching techniques developed during the first two years of the project with the industry standard assisted history matching. We enhance the widely used assisted history matching in two important aspects that can significantly improve its efficiency and effectiveness. First, we utilize streamline-derived analytic sensitivities to relate the changes in reservoir properties to the production response. These sensitivities can be computed analytically and contain much more information than that used in the assisted history matching. Second, we utilize the sensitivities in an optimization procedure to determine the spatial distribution and magnitude of the changes in reservoir parameters needed to improve the history-match. By intervening at each iteration during the optimization process, we can retain control over the history matching process as in assisted history matching. This allows us to accept, reject, or modify changes during the automatic history matching process. We demonstrate the power of our method using two field examples with model sizes ranging from 10{sup 5} to 10{sup 6} grid blocks and with over one hundred wells. We have also extended the streamline-based production data integration technique to naturally fractured reservoirs using the dual porosity approach. The principal features of our method are the extension of streamline-derived analytic sensitivities to account for matrix-fracture interactions and the use of our previously proposed generalized travel time inversion for history matching. Our proposed workflow has been demonstrated by using both a dual porosity streamline simulator and a commercial finite difference simulator. Our approach is computationally efficient and well suited for large scale field applications in naturally fractured reservoirs with changing field conditions. This considerably broadens the applicability of the streamline-based analysis of tracer data ...
Date: August 1, 2005
Creator: Datta-Gupta, Akhil
Partner: UNT Libraries Government Documents Department

Absolute Bunch Length Measurements by Incoherent Radiation Fluctuation Analysis

Description: By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.
Date: December 9, 2009
Creator: Sannibale, F.; /LBL, Berkeley; Stupakov, G.V.; /SLAC; Zolotorev, M.S.; /LBL, Berkeley et al.
Partner: UNT Libraries Government Documents Department