Discrete Feature Approach for Heterogeneous Reservoir Production Enhancement
Dershowitz, William S.; Curran, Brendan; Einstein, Herbert; LaPointe, Paul; Shuttle, Dawn; Klise, Kate
2002-07-26
The report presents summaries of technology development for discrete feature modeling in support of the improved oil recovery (IOR) for heterogeneous reservoirs. In addition, the report describes the demonstration of these technologies at project study sites.
Dershowitz, William S.; Einstein, Herbert H.; LaPoint, Paul R.; Eiben, Thorsten; Wadleigh, Eugene; Ivanova, Violeta
1998-12-01
This report summarizes research conducted for the Fractured Reservoir Discrete Feature Network Technologies Project. The five areas studied are development of hierarchical fracture models; fractured reservoir compartmentalization, block size, and tributary volume analysis; development and demonstration of fractured reservoir discrete feature data analysis tools; development of tools for data integration and reservoir simulation through application of discrete feature network technologies for tertiary oil production; quantitative evaluation of the economic value of this analysis approach.
Discrete Feature Approach for Heterogeneous Reservoir Production Enhancement
Dershowitz, William S.; Cladouhos, Trenton
2001-09-06
This progress report describes activities during the period January 1, 1999 to June 30, 1999. Work was carried out on 21 tasks. The major activity during the reporting period was the development and preliminary application of discrete fracture network (DFN) models for Stoney Point, South Oregon Basin, and North Oregon Basins project study sites. In addition, research was carried out on analysis algorithms for discrete future orientation.
Dershowitz, W.S.; La Pointe, P.R.; Einstein, H.H.; Ivanova, V.
1998-01-01
This report describes progress on the project, {open_quotes}Fractured Reservoir Discrete Feature Network Technologies{close_quotes} during the period March 7, 1996 to February 28, 1997. The report presents summaries of technology development for the following research areas: (1) development of hierarchical fracture models, (2) fractured reservoir compartmentalization and tributary volume, (3) fractured reservoir data analysis, and (4) integration of fractured reservoir data and production technologies. In addition, the report provides information on project status, publications submitted, data collection activities, and technology transfer through the world wide web (WWW). Research on hierarchical fracture models included geological, mathematical, and computer code development. The project built a foundation of quantitative, geological and geometrical information about the regional geology of the Permian Basin, including detailed information on the lithology, stratigraphy, and fracturing of Permian rocks in the project study area (Tracts 17 and 49 in the Yates field). Based on the accumulated knowledge of regional and local geology, project team members started the interpretation of fracture genesis mechanisms and the conceptual modeling of the fracture system in the study area. Research on fractured reservoir compartmentalization included basic research, technology development, and application of compartmentalized reservoir analyses for the project study site. Procedures were developed to analyze compartmentalization, tributary drainage volume, and reservoir matrix block size. These algorithms were implemented as a Windows 95 compartmentalization code, FraCluster.
Discretization of continuous features in clinical datasets
Maslove, David M; Podchiyska, Tanya; Lowe, Henry J
2013-01-01
Background The increasing availability of clinical data from electronic medical records (EMRs) has created opportunities for secondary uses of health information. When used in machine learning classification, many data features must first be transformed by discretization. Objective To evaluate six discretization strategies, both supervised and unsupervised, using EMR data. Materials and methods We classified laboratory data (arterial blood gas (ABG) measurements) and physiologic data (cardiac output (CO) measurements) derived from adult patients in the intensive care unit using decision trees and naïve Bayes classifiers. Continuous features were partitioned using two supervised, and four unsupervised discretization strategies. The resulting classification accuracy was compared with that obtained with the original, continuous data. Results Supervised methods were more accurate and consistent than unsupervised, but tended to produce larger decision trees. Among the unsupervised methods, equal frequency and k-means performed well overall, while equal width was significantly less accurate. Discussion This is, we believe, the first dedicated evaluation of discretization strategies using EMR data. It is unlikely that any one discretization method applies universally to EMR data. Performance was influenced by the choice of class labels and, in the case of unsupervised methods, the number of intervals. In selecting the number of intervals there is generally a trade-off between greater accuracy and greater consistency. Conclusions In general, supervised methods yield higher accuracy, but are constrained to a single specific application. Unsupervised methods do not require class labels and can produce discretized data that can be used for multiple purposes. PMID:23059731
An analytical thermohydraulic model for discretely fractured geothermal reservoirs
NASA Astrophysics Data System (ADS)
Fox, Don B.; Koch, Donald L.; Tester, Jefferson W.
2016-09-01
In discretely fractured reservoirs such as those found in Enhanced/Engineered Geothermal Systems (EGS), knowledge of the fracture network is important in understanding the thermal hydraulics, i.e., how the fluid flows and the resulting temporal evolution of the subsurface temperature. The purpose of this study was to develop an analytical model of the fluid flow and heat transport in a discretely fractured network that can be used for a wide range of modeling applications and serve as an alternative analysis tool to more computationally intensive numerical codes. Given the connectivity and structure of a fracture network, the flow in the system was solved using a linear system of algebraic equations for the pressure at the nodes of the network. With the flow determined, the temperature in the fracture was solved by coupling convective heat transport in the fracture with one-dimensional heat conduction perpendicular to the fracture, employing the Green's function derived solution for a single discrete fracture. The predicted temperatures along the fracture surfaces from the analytical solution were compared to numerical simulations using the TOUGH2 reservoir code. Through two case studies, we showed the capabilities of the analytical model and explored the effect of uncertainty in the fracture apertures and network structure on thermal performance. While both sources of uncertainty independently produce large variations in production temperature, uncertainty in the network structure, whenever present, had a predominant influence on thermal performance.
Discrete Biogeography Based Optimization for Feature Selection in Molecular Signatures.
Liu, Bo; Tian, Meihong; Zhang, Chunhua; Li, Xiangtao
2015-04-01
Biomarker discovery from high-dimensional data is a complex task in the development of efficient cancer diagnoses and classification. However, these data are usually redundant and noisy, and only a subset of them present distinct profiles for different classes of samples. Thus, selecting high discriminative genes from gene expression data has become increasingly interesting in the field of bioinformatics. In this paper, a discrete biogeography based optimization is proposed to select the good subset of informative gene relevant to the classification. In the proposed algorithm, firstly, the fisher-markov selector is used to choose fixed number of gene data. Secondly, to make biogeography based optimization suitable for the feature selection problem; discrete migration model and discrete mutation model are proposed to balance the exploration and exploitation ability. Then, discrete biogeography based optimization, as we called DBBO, is proposed by integrating discrete migration model and discrete mutation model. Finally, the DBBO method is used for feature selection, and three classifiers are used as the classifier with the 10 fold cross-validation method. In order to show the effective and efficiency of the algorithm, the proposed algorithm is tested on four breast cancer dataset benchmarks. Comparison with genetic algorithm, particle swarm optimization, differential evolution algorithm and hybrid biogeography based optimization, experimental results demonstrate that the proposed method is better or at least comparable with previous method from literature when considering the quality of the solutions obtained.
On the complexity of discrete feature selection for optimal classification.
Peña, Jose M; Nilsson, Roland
2010-08-01
Consider a classification problem involving only discrete features that are represented as random variables with some prescribed discrete sample space. In this paper, we study the complexity of two feature selection problems. The first problem consists in finding a feature subset of a given size k that has minimal Bayes risk. We show that for any increasing ordering of the Bayes risks of the feature subsets (consistent with an obvious monotonicity constraint), there exists a probability distribution that exhibits that ordering. This implies that solving the first problem requires an exhaustive search over the feature subsets of size k. The second problem consists of finding the minimal feature subset that has minimal Bayes risk. In the light of the complexity of the first problem, one may think that solving the second problem requires an exhaustive search over all of the feature subsets. We show that, under mild assumptions, this is not true. We also study the practical implications of our solutions to the second problem.
Application of Discrete Fracture Modeling and Upscaling Techniques to Complex Fractured Reservoirs
NASA Astrophysics Data System (ADS)
Karimi-Fard, M.; Lapene, A.; Pauget, L.
2012-12-01
During the last decade, an important effort has been made to improve data acquisition (seismic and borehole imaging) and workflow for reservoir characterization which has greatly benefited the description of fractured reservoirs. However, the geological models resulting from the interpretations need to be validated or calibrated against dynamic data. Flow modeling in fractured reservoirs remains a challenge due to the difficulty of representing mass transfers at different heterogeneity scales. The majority of the existing approaches are based on dual continuum representation where the fracture network and the matrix are represented separately and their interactions are modeled using transfer functions. These models are usually based on idealized representation of the fracture distribution which makes the integration of real data difficult. In recent years, due to increases in computer power, discrete fracture modeling techniques (DFM) are becoming popular. In these techniques the fractures are represented explicitly allowing the direct use of data. In this work we consider the DFM technique developed by Karimi-Fard et al. [1] which is based on an unstructured finite-volume discretization. The mass flux between two adjacent control-volumes is evaluated using an optimized two-point flux approximation. The result of the discretization is a list of control-volumes with the associated pore-volumes and positions, and a list of connections with the associated transmissibilities. Fracture intersections are simplified using a connectivity transformation which contributes considerably to the efficiency of the methodology. In addition, the method is designed for general purpose simulators and any connectivity based simulator can be used for flow simulations. The DFM technique is either used standalone or as part of an upscaling technique. The upscaling techniques are required for large reservoirs where the explicit representation of all fractures and faults is not possible
China onshore heavy oil reservoir features and new recovery measures
Naiju Wang
1995-12-31
China is known as being rich in onshore heavy oil resources, with a variety of reservoir characteristics, and complex conditions for thermal recoveries. Over the past decade, with improvement in technology, the scale of heavy oil production has continually expanded, and China has now become one of the major heavy oil producing countries in the world. To date, a complete set of techniques associated with huff and puff processes has been developed with some unique features. This paper analyzes several problems inherent in heavy oil development, and presents technical measures for the future development of heavy oil.
NASA Astrophysics Data System (ADS)
Karimi-Fard, M.; Durlofsky, L. J.
2016-10-01
A comprehensive framework for modeling flow in porous media containing thin, discrete features, which could be high-permeability fractures or low-permeability deformation bands, is presented. The key steps of the methodology are mesh generation, fine-grid discretization, upscaling, and coarse-grid discretization. Our specialized gridding technique combines a set of intersecting triangulated surfaces by constructing approximate intersections using existing edges. This procedure creates a conforming mesh of all surfaces, which defines the internal boundaries for the volumetric mesh. The flow equations are discretized on this conforming fine mesh using an optimized two-point flux finite-volume approximation. The resulting discrete model is represented by a list of control-volumes with associated positions and pore-volumes, and a list of cell-to-cell connections with associated transmissibilities. Coarse models are then constructed by the aggregation of fine-grid cells, and the transmissibilities between adjacent coarse cells are obtained using flow-based upscaling procedures. Through appropriate computation of fracture-matrix transmissibilities, a dual-continuum representation is obtained on the coarse scale in regions with connected fracture networks. The fine and coarse discrete models generated within the framework are compatible with any connectivity-based simulator. The applicability of the methodology is illustrated for several two- and three-dimensional examples. In particular, we consider gas production from naturally fractured low-permeability formations, and transport through complex fracture networks. In all cases, highly accurate solutions are obtained with significant model reduction.
Modeling discrete survival time using genomic feature data.
Ferber, Kyle; Archer, Kellie J
2015-01-01
Researchers have recently shown that penalized models perform well when applied to high-throughput genomic data. Previous researchers introduced the generalized monotone incremental forward stagewise (GMIFS) method for fitting overparameterized logistic regression models. The GMIFS method was subsequently extended by others for fitting several different logit link ordinal response models to high-throughput genomic data. In this study, we further extended the GMIFS method for ordinal response modeling using a complementary log-log link, which allows one to model discrete survival data. We applied our extension to a publicly available microarray gene expression dataset (GSE53733) with a discrete survival outcome. The dataset included 70 primary glioblastoma samples from patients of the German Glioma Network with long-, intermediate-, and short-term overall survival. We tested the performance of our method by examining the prediction accuracy of the fitted model. The method has been implemented as an addition to the ordinalgmifs package in the R programming environment.
NASA Astrophysics Data System (ADS)
Gareis, I.; Gentiletti, G.; Acevedo, R.; Rufiner, L.
2011-09-01
The purpose of this work is to evaluate different feature extraction alternatives to detect the event related evoked potential signal on brain computer interfaces, trying to minimize the time employed and the classification error, in terms of sensibility and specificity of the method, looking for alternatives to coherent averaging. In this context the results obtained performing the feature extraction using discrete dyadic wavelet transform using different mother wavelets are presented. For the classification a single layer perceptron was used. The results obtained with and without the wavelet decomposition were compared; showing an improvement on the classification rate, the specificity and the sensibility for the feature vectors obtained using some mother wavelets.
Henipaviruses: an updated review focusing on the pteropid reservoir and features of transmission.
Clayton, B A; Wang, L F; Marsh, G A
2013-02-01
The henipaviruses, Hendra virus and Nipah virus, are pathogens that have emerged from flying foxes in Australia and South-east Asia to infect both livestock and humans, often fatally. Since the emergence of Hendra virus in Australia in 1994 and the identification of Australian flying foxes as hosts to this virus, our appreciation of bats as reservoir hosts of henipaviruses has expanded globally to include much of Asia and areas of Africa. Despite this, little is currently known of the mechanisms by which bats harbour viruses capable of causing such severe disease in other terrestrial mammals. Pteropid bat ecology, henipavirus virology, therapeutic developments and features of henipavirus infection, pathology and disease in humans and other mammals are reviewed elsewhere in detail. This review focuses on bats as reservoir hosts to henipaviruses and features of transmission of Hendra virus and Nipah virus following spillover from these reservoir hosts.
Selecting discrete and continuous features based on neighborhood decision error minimization.
Hu, Qinghua; Pedrycz, Witold; Yu, Daren; Lang, Jun
2010-02-01
Feature selection plays an important role in pattern recognition and machine learning. Feature evaluation and classification complexity estimation arise as key issues in the construction of selection algorithms. To estimate classification complexity in different feature subspaces, a novel feature evaluation measure, called the neighborhood decision error rate (NDER), is proposed, which is applicable to both categorical and numerical features. We first introduce a neighborhood rough-set model to divide the sample set into decision positive regions and decision boundary regions. Then, the samples that fall within decision boundary regions are further grouped into recognizable and misclassified subsets based on class probabilities that occur in neighborhoods. The percentage of misclassified samples is viewed as the estimate of classification complexity of the corresponding feature subspaces. We present a forward greedy strategy for searching the feature subset, which minimizes the NDER and, correspondingly, minimizes the classification complexity of the selected feature subset. Both theoretical and experimental comparison with other feature selection algorithms shows that the proposed algorithm is effective for discrete and continuous features, as well as their mixture.
He, Jiayuan; Zhang, Dingguo; Sheng, Xinjun; Meng, Jianjun; Zhu, Xiangyang
2013-01-01
An improved discrete Fourier transform (iDFT) is presented in this study as a novel feature for surface electromyogram (sEMG) pattern classification. It employs the principle that the spectrum of sEMG signals changes regarding different motions. iDFT feature focuses on global information of local bands to increase the inter-class distance. The experiment results showed that iDFT feature had a better separability than two other spectral features, auto regression (AR) and Power spectral density (PSD), both on experienced and inexperienced subjects. The optimal bandwidth is between 30 and 50 Hz and influence of division methods is not significant. With the low computation cost and property of insensitivity to sampling frequency, our proposed method provides a competitive choice for prosthetic control.
Lamb wave feature extraction using discrete wavelet transformation and Principal Component Analysis
NASA Astrophysics Data System (ADS)
Ghodsi, Mojtaba; Ziaiefar, Hamidreza; Amiryan, Milad; Honarvar, Farhang; Hojjat, Yousef; Mahmoudi, Mehdi; Al-Yahmadi, Amur; Bahadur, Issam
2016-04-01
In this research, a new method is presented for eliciting the proper features for recognizing and classifying the kinds of the defects by guided ultrasonic waves. After applying suitable preprocessing, the suggested method extracts the base frequency band from the received signals by discrete wavelet transform and discrete Fourier transform. This frequency band can be used as a distinctive feature of ultrasonic signals in different defects. Principal Component Analysis with improving this feature and decreasing extra data managed to improve classification. In this study, ultrasonic test with A0 mode lamb wave is used and is appropriated to reduce the difficulties around the problem. The defects under analysis included corrosion, crack and local thickness reduction. The last defect is caused by electro discharge machining (EDM). The results of the classification by optimized Neural Network depicts that the presented method can differentiate different defects with 95% precision and thus, it is a strong and efficient method. Moreover, comparing the elicited features for corrosion and local thickness reduction and also the results of the two's classification clarifies that modeling the corrosion procedure by local thickness reduction which was previously common, is not an appropriate method and the signals received from the two defects are different from each other.
Lahmiri, Salim; Boukadoum, Mounir
2013-01-01
A new methodology for automatic feature extraction from biomedical images and subsequent classification is presented. The approach exploits the spatial orientation of high-frequency textural features of the processed image as determined by a two-step process. First, the two-dimensional discrete wavelet transform (DWT) is applied to obtain the HH high-frequency subband image. Then, a Gabor filter bank is applied to the latter at different frequencies and spatial orientations to obtain new Gabor-filtered image whose entropy and uniformity are computed. Finally, the obtained statistics are fed to a support vector machine (SVM) binary classifier. The approach was validated on mammograms, retina, and brain magnetic resonance (MR) images. The obtained classification accuracies show better performance in comparison to common approaches that use only the DWT or Gabor filter banks for feature extraction. PMID:27006906
Lahmiri, Salim; Boukadoum, Mounir
2013-01-01
A new methodology for automatic feature extraction from biomedical images and subsequent classification is presented. The approach exploits the spatial orientation of high-frequency textural features of the processed image as determined by a two-step process. First, the two-dimensional discrete wavelet transform (DWT) is applied to obtain the HH high-frequency subband image. Then, a Gabor filter bank is applied to the latter at different frequencies and spatial orientations to obtain new Gabor-filtered image whose entropy and uniformity are computed. Finally, the obtained statistics are fed to a support vector machine (SVM) binary classifier. The approach was validated on mammograms, retina, and brain magnetic resonance (MR) images. The obtained classification accuracies show better performance in comparison to common approaches that use only the DWT or Gabor filter banks for feature extraction.
Bremigan, M.T.; Soranno, P.A.; Gonzalez, M.J.; Bunnell, D.B.; Arend, K.K.; Renwick, W.H.; Stein, R.A.; Vanni, M.J.
2008-01-01
Although effects of land use/cover on nutrient concentrations in aquatic systems are well known, half or more of the variation in nutrient concentration remains unexplained by land use/cover alone. Hydrogeomorphic (HGM) landscape features can explain much remaining variation and influence food web interactions. To explore complex linkages among land use/cover, HGM features, reservoir productivity, and food webs, we sampled 11 Ohio reservoirs, ranging broadly in agricultural catchment land use/cover, for 3 years. We hypothesized that HGM features mediate the bottom-up effects of land use/cover on reservoir productivity, chlorophyll a, zooplankton, and recruitment of gizzard shad, an omnivorous fish species common throughout southeastern U.S. reservoirs and capable of exerting strong effects on food web and nutrient dynamics. We tested specific hypotheses using a model selection approach. Percent variation explained was highest for total nitrogen (R2 = 0.92), moderately high for total phosphorus, chlorophyll a, and rotifer biomass (R2 = 0.57 to 0.67), relatively low for crustacean zooplankton biomass and larval gizzard shad hatch abundance (R2 = 0.43 and 0.42), and high for larval gizzard shad survivor abundance (R2 = 0.79). The trophic status models included agricultural land use/cover and an HGM predictor, whereas the zooplankton models had few HGM predictors. The larval gizzard shad models had the highest complexity, including more than one HGM feature and food web components. We demonstrate the importance of integrating land use/cover, HGM features, and food web interactions to investigate critical interactions and feedbacks among physical, chemical, and biological components of linked land-water ecosystems.
Daily reservoir inflow forecasting using multiscale deep feature learning with hybrid models
NASA Astrophysics Data System (ADS)
Bai, Yun; Chen, Zhiqiang; Xie, Jingjing; Li, Chuan
2016-01-01
Inflow forecasting applies data supports for the operations and managements of reservoirs. A multiscale deep feature learning (MDFL) method with hybrid models is proposed in this paper to deal with the daily reservoir inflow forecasting. Ensemble empirical mode decomposition and Fourier spectrum are first employed to extract multiscale (trend, period and random) features, which are then represented by three deep belief networks (DBNs), respectively. The weights of each DBN are subsequently applied to initialize a neural network (D-NN). The outputs of the three-scale D-NNs are finally reconstructed using a sum-up strategy toward the forecasting results. A historical daily inflow series (from 1/1/2000 to 31/12/2012) of the Three Gorges reservoir, China, is investigated by the proposed MDFL with hybrid models. For comparison, four peer models are adopted for the same task. The results show that, the present model overwhelms all the peer models in terms of mean absolute percentage error (MAPE = 11.2896%), normalized root-mean-square error (NRMSE = 0.2292), determination coefficient criteria (R2 = 0.8905), and peak percent threshold statistics (PPTS(5) = 10.0229%). The addressed method integrates the deep framework with multiscale and hybrid observations, and therefore being good at exploring sophisticated natures in the reservoir inflow forecasting.
NASA Astrophysics Data System (ADS)
Kavousi Ghahfarokhi, Payam
The Tensleep oil reservoir at Teapot Dome, Wyoming, USA, is a naturally fractured tight sandstone reservoir that has been considered for carbon-dioxide enhanced oil recovery (CO2-EOR) and sequestration. CO2-EOR analysis requires a thorough understanding of the Tensleep fracture network. Wireline image logs from the field suggest that the reservoir fracture network is dominated by early formed structural hinge oblique fractures with interconnectivity enhanced by hinge parallel and hinge perpendicular fracture sets. Available post stack 3D seismic data are used to generate a seismic fracture intensity attribute for the reservoir fracture network. The resulting seismic fracture intensity is qualitatively correlated to the field production history. Wells located on hinge-oblique discontinuities are more productive than other wells in the field. We use Oda's method to upscale the fracture permeabilities in the discrete fracture network for use in a dual porosity fluid flow simulator. We analytically show that Oda's method is sensitive to the grid orientation relative to fracture set strike. Results show that the calculated permeability tensors have maximum geometric mean for the non-zero permeability components (kxx,kyy,kzz,kxy) when the dominant fracture set cuts diagonally through the grid cell at 45° relative to the grid cell principal directions (i,j). The geometric mean of the permeability tensor components falls to a minimum when the dominant fracture set is parallel to either grid wall (i or j principal directions). The latter case has off-diagonal permeability terms close to zero. We oriented the Tensleep reservoir grid to N72°W to minimize the off-diagonal permeability terms. The seismic fracture intensity attribute is then used to generate a realization of the reservoir fracture network. Subsequently, fracture properties are upscaled to the reservoir grid scale for a fully compositional flow simulation. We implemented a PVT analysis using CO2 swelling test
Khalighi, Sirvan; Sousa, Teresa; Oliveira, Dulce; Pires, Gabriel; Nunes, Urbano
2011-01-01
In this paper, a novel algorithm is proposed with application in sleep/awake detection and in multiclass sleep stage classification (awake, non rapid eye movement (NREM) sleep and REM sleep). In turn, NREM is further divided into three stages denoted here by S1, S2, and S3. Six electroencephalographic (EEG) and two electro-oculographic (EOG) channels were used in this study. The maximum overlap discrete wavelet transform (MODWT) with the multi-resolution Analysis is applied to extract relevant features from EEG and EOG signals. The extracted feature set is transformed and normalized to reduce the effect of extreme values of features. A set of significant features are selected by mRMR which is a powerful feature selection method. Finally the selected feature set is classified using support vector machines (SVMs). The system achieved 95.0% of average accuracy for sleep/awake detection. As concerns the multiclass case, the average accuracy of sleep stages classification was 93.0%.
NASA Astrophysics Data System (ADS)
Demyanov, V.; Backhouse, L.; Christie, M.
2015-12-01
There is a continuous challenge in identifying and propagating geologically realistic features into reservoir models. Many of the contemporary geostatistical algorithms are limited by various modelling assumptions, like stationarity or Gaussianity. Another related challenge is to ensure the realistic geological features introduced into a geomodel are preserved during the model update in history matching studies, when the model properties are tuned to fit the flow response to production data. The above challenges motivate exploration and application of other statistical approaches to build and calibrate reservoir models, in particular, methods based on statistical learning. The paper proposes a novel data driven approach - Multiple Kernel Learning (MKL) - for modelling porous property distributions in sub-surface reservoirs. Multiple Kernel Learning aims to extract relevant spatial features from spatial patterns and to combine them in a non-linear way. This ability allows to handle multiple geological scenarios, which represent different spatial scales and a range of modelling concepts/assumptions. Multiple Kernel Learning is not restricted by deterministic or statistical modelling assumptions and, therefore, is more flexible for modelling heterogeneity at different scales and integrating data and knowledge. We demonstrate an MKL application to a problem of history matching based on a diverse prior information embedded into a range of possible geological scenarios. MKL was able to select the most influential prior geological scenarios and fuse the selected spatial features into a multi-scale property model. The MKL was applied to Brugge history matching benchmark example by calibrating the parameters of the MKL reservoir model parameters to production data. The history matching results were compared to the ones obtained from other contemporary approaches - EnKF and kernel PCA with stochastic optimisation.
Ramos, Vera; Canta, Guilherme; de Castro, Filipa; Leal, Isabel
2014-08-01
Research suggests that borderline personality disorder (BPD) can be diagnosed in adolescents and is marked by considerable heterogeneity. This study aimed to identify personality features characterizing adolescents with BPD and possible meaningful patterns of heterogeneity that could lead to personality subgroups. The authors analyzed data on 60 adolescents, ages 15 to 18 years, who met DSM criteria for a BPD diagnosis. The authors used latent class analysis (LCA) to identify subgroups based on the personality pattern scales from the Millon Adolescent Clinical Inventory (MACI). LCA indicated that the best-fitting solution was a two-class model, identifying two discrete subgroups of BPD adolescents that were described as internalizing and externalizing. The subgroups were then compared on clinical and sociodemographic variables, measures of personality dimensions, DSM BPD criteria, and perception of attachment styles. Adolescents with a BPD diagnosis constitute a heterogeneous group and vary meaningfully on personality features that can have clinical implications for treatment.
Discrete Sources Method for light scattering analysis of non-axisymmetric features of a substrate
NASA Astrophysics Data System (ADS)
Eremin, Yuri; Wriedt, Thomas
2016-01-01
The Discrete Sources Method (DSM) has been extended to analyze polarized light scattering by non-axial symmetric nano-sized features on a plane substrate. A detailed description of the corresponding numerical scheme is provided. Using a "fictitious" particle approach the new DSM model enables to consider scattering from such substrate defects as a line bump and a line pit. The developed computer model has been employed for demonstrating the ability to perform a comparative analysis of light scattering from such line features. Simulation results corresponding to the Differential Scattering Cross-Section (DSC) and the integral response for P/S polarized light are presented. It was found that the integral response can change by an order of magnitude depending on the orientation of the linear defect with respect to the direction of the incident laser light. In addition, it was shown that some defects can turn out to be "invisible" if an oblique angle of incidence is chosen.
Ion-neutral momentum coupling near discrete high-latitude ionospheric features
NASA Technical Reports Server (NTRS)
St-Maurice, J.-P.; Schunk, R. W.
1981-01-01
A two-dimensional numerical model is developed to study the momentum coupling between the ionosphere and neutral atmosphere in the vicinity of discrete high-latitude features, such as convection channels and plasma density troughs. Based on generalized magnetohydrodynamic equations the model takes account of global pressure gradients, viscous dissipation, ion drag, the Coriolis force, and electrodynamic drifts. Among the findings of an initial steady state investigation are the following: (1) in convection channels, significant shears and rotations of the thermospheric flow can occur below 200 km if a minimum in the electron density profile is present between the E and F regions; (2) in convection channels, the thermospheric wind decreases with height in the F region owing to the effects of horizontal viscosity; and (3) at low altitudes, the boundaries of convection channels may produce Ekman spirals.
Bennet, Jaison; Ganaprakasam, Chilambuchelvan Arul; Arputharaj, Kannan
2014-01-01
Cancer classification by doctors and radiologists was based on morphological and clinical features and had limited diagnostic ability in olden days. The recent arrival of DNA microarray technology has led to the concurrent monitoring of thousands of gene expressions in a single chip which stimulates the progress in cancer classification. In this paper, we have proposed a hybrid approach for microarray data classification based on nearest neighbor (KNN), naive Bayes, and support vector machine (SVM). Feature selection prior to classification plays a vital role and a feature selection technique which combines discrete wavelet transform (DWT) and moving window technique (MWT) is used. The performance of the proposed method is compared with the conventional classifiers like support vector machine, nearest neighbor, and naive Bayes. Experiments have been conducted on both real and benchmark datasets and the results indicate that the ensemble approach produces higher classification accuracy than conventional classifiers. This paper serves as an automated system for the classification of cancer and can be applied by doctors in real cases which serve as a boon to the medical community. This work further reduces the misclassification of cancers which is highly not allowed in cancer detection.
NASA Astrophysics Data System (ADS)
Sitdikova, Elina; Izotov, Victor
2010-05-01
The Tevlinsko-Russkinskoe oil field is located in the central part of the West Siberian lowland. It concerns a group of multistory deposits and is one of the perspective deposits in the West Siberian oil and gas province. The young Sortym formation and the Jurassic sediments offer the best prospects. Layers are consisted of sand-clay deposits of Mesozoic-Cainozoic sedimentary cover and rocks of the pre-Jurassic basement. Core material of base drill holes of the Tevlinsko-Russkinskoe oil field was studied in order to obtain detailed lithological and mineralogical characteristics of rocks features. These drill holes found out main productive horizons. Sandstones of productive horizons of Jurassic petroliferous complex are of a homogeneous and monotonous structure. In the studied samples of core material massive structures prevail. Mineral composite of clastic component of sandstones is polymictic and it is represented by quartz, orthoclase, microcline, plagioclases, biotite, strongly changed dark-coloured minerals, fragments of effusive rocks and quartzite of different degrees of recrystallization. Cluster formation - grains accretion into separated quartzite-like parts - is typical for these rocks. Process of cluster formation is accompanied by change of sandstone structure. This results in reservoir quality alteration and extension of porosity and permeability properties. In the studied rocks-reservoirs of Jurassic oil complex processes of cluster formation were lasting during period of diagenesis and were followed by repartition of cement mass. We carried out electron microscopic research of reservoirs structure to analyze void space structure. Electron microscopic studies were spent on the scanning electron microscope of XL-30 system (Phillips company). The conducted research testifies that reservoirs can be considered a mesoporous-nanoporous medium. Its' studying is of a great importance for realization of questions of Tevlinsko-Russkinskoe oil field working out.
NASA Astrophysics Data System (ADS)
Wellman, T. P.; Poeter, E. P.
2003-12-01
Fractured aquifers serve as primary water resources throughout the western United States. In light of diminishing water supply, management practices must be improved to promote resource sustainability. Ground-water flow models are often the preferred management tool, but can be computationally expensive and difficult to implement in large-scale fractured environments. Discrete feature network (DFN) simulation is a robust approach for modeling fluid movement in fractured architecture, but numerically expensive for large-scale models. By using an equivalent continuum model (ECM) numerical expense may be substantially reduced. An intrinsic assumption of the ECM approach is that the geologic media is represented accurately as a continuum, requiring that grid scale discretization correspond to representative elementary scale (RES) at each location within a fractured aquifer. Heterogeneity and compartmentalization likely cause regions with large differences in fracture permeability and connectivity, resulting in spatially variable RES. Thus, while regional flow may be honored using essentially any grid pattern, failure to properly represent spatially variable RES could lead to erroneous predictions of local flow and transport, especially in highly heterogeneous zones. The purpose of our study is to determine whether head predictions from DFN flow simulations can delineate spatially variable RES in fractured aquifers. Provided there is a correlation of simulated hydraulic head to continuum scale, we hypothesize that RES can be identified using spatially disperse water level observations within a fractured aquifer watershed. Preliminary results suggest there is potential for using hydraulic head data to determine the RES. Ongoing research is necessary to confirm these preliminary results and our hypothesis.
Hawes, Chris S; Kruger, Paul E
2014-11-21
Reported here are the syntheses of four indazole-based ligands and the structural characterisation of four Cu(II) complexes derived from them. The ligands 1-(2-pyridyl)-1H-indazole, L1, and 2-(2-pyridyl)-2H-indazole, L2, have been characterised by single crystal X-ray diffraction methods for the first time. The intramolecular structural changes within L1 and L2 that result from the transition from the 1H to the 2H electronic configuration have been delineated. The synthesis of 1H-indazole-6-carboxylic acid, H2L3, and 1H-indazole-7-carboxylic acid, H2L4, is fully described and the structure of H2L4·H2O determined. The structures of two discrete mononuclear complexes {[Cu(L1)2(NO3)]·NO3·1.5H2O}, 1, and {[Cu(L2)2(NO3)]·NO3}, 2, have been determined and their molecular compositions corroborated by solution-based methods. Reaction of Cu(II) with H2L3 generates a 2D coordination polymer, [Cu3(HL3)4(NO3)2(EtOH)2]·3(C6H6)·2(H2O), 3, that features the archetypal [Cu2(OAc)4] paddlewheel motif and 1D channels; whereas reaction with H2L4 gives a discrete complex [Cu(HL4)2]·H2O·MeOH, 4, in which hydrogen bonding interactions link indazole dimers via a water molecule to yield a 1D network.
McKoy, M.L., Sams, W.N.
1997-10-01
The US Department of Energy, Federal Energy Technology Center, has sponsored a project to simulate the behavior of tight, fractured, strata-bound gas reservoirs that arise from irregular discontinuous, or clustered networks of fractures. New FORTRAN codes have been developed to generate fracture networks, or simulate reservoir drainage/recharge, and to plot the fracture networks and reservoirs pressures. Ancillary codes assist with raw data analysis.
NASA Astrophysics Data System (ADS)
Profit, Matthew; Dutko, Martin; Yu, Jianguo; Cole, Sarah; Angus, Doug; Baird, Alan
2016-04-01
This paper presents a novel approach to predict the propagation of hydraulic fractures in tight shale reservoirs. Many hydraulic fracture modelling schemes assume that the fracture direction is pre-seeded in the problem domain discretisation. This is a severe limitation as the reservoir often contains large numbers of pre-existing fractures that strongly influence the direction of the propagating fracture. To circumvent these shortcomings, a new fracture modelling treatment is proposed where the introduction of discrete fracture surfaces is based on new and dynamically updated geometrical entities rather than the topology of the underlying spatial discretisation. Hydraulic fracturing is an inherently coupled engineering problem with interactions between fluid flow and fracturing when the stress state of the reservoir rock attains a failure criterion. This work follows a staggered hydro-mechanical coupled finite/discrete element approach to capture the key interplay between fluid pressure and fracture growth. In field practice, the fracture growth is hidden from the design engineer and microseismicity is often used to infer hydraulic fracture lengths and directions. Microseismic output can also be computed from changes of the effective stress in the geomechanical model and compared against field microseismicity. A number of hydraulic fracture numerical examples are presented to illustrate the new technology.
Information Requirements for Integrating Spatially Discrete, Feature-Based Earth Observations
NASA Astrophysics Data System (ADS)
Horsburgh, J. S.; Aufdenkampe, A. K.; Lehnert, K. A.; Mayorga, E.; Hsu, L.; Song, L.; Zaslavsky, I.; Valentine, D. L.
2014-12-01
Several cyberinfrastructures have emerged for sharing observational data collected at densely sampled and/or highly instrumented field sites. These include the CUAHSI Hydrologic Information System (HIS), the Critical Zone Observatory Integrated Data Management System (CZOData), the Integrated Earth Data Applications (IEDA) and EarthChem system, and the Integrated Ocean Observing System (IOOS). These systems rely on standard data encodings and, in some cases, standard semantics for classes of geoscience data. Their focus is on sharing data on the Internet via web services in domain specific encodings or markup languages. While they have made progress in making data available, it still takes investigators significant effort to discover and access datasets from multiple repositories because of inconsistencies in the way domain systems describe, encode, and share data. Yet, there are many scenarios that require efficient integration of these data types across different domains. For example, understanding a soil profile's geochemical response to extreme weather events requires integration of hydrologic and atmospheric time series with geochemical data from soil samples collected over various depth intervals from soil cores or pits at different positions on a landscape. Integrated access to and analysis of data for such studies are hindered because common characteristics of data, including time, location, provenance, methods, and units are described differently within different systems. Integration requires syntactic and semantic translations that can be manual, error-prone, and lossy. We report information requirements identified as part of our work to define an information model for a broad class of earth science data - i.e., spatially-discrete, feature-based earth observations resulting from in-situ sensors and environmental samples. We sought to answer the question: "What information must accompany observational data for them to be archivable and discoverable within
Stone, Mandy L.; Graham, Jennifer L.; Gatotho, Jackline W.
2013-01-01
Cheney Reservoir, located in south-central Kansas, is one of the primary water supplies for the city of Wichita, Kansas. The U.S. Geological Survey has operated a continuous real-time water-quality monitoring station in Cheney Reservoir since 2001; continuously measured physicochemical properties include specific conductance, pH, water temperature, dissolved oxygen, turbidity, fluorescence (wavelength range 650 to 700 nanometers; estimate of total chlorophyll), and reservoir elevation. Discrete water-quality samples were collected during 2001 through 2009 and analyzed for sediment, nutrients, taste-and-odor compounds, cyanotoxins, phytoplankton community composition, actinomycetes bacteria, and other water-quality measures. Regression models were developed to establish relations between discretely sampled constituent concentrations and continuously measured physicochemical properties to compute concentrations of constituents that are not easily measured in real time. The water-quality information in this report is important to the city of Wichita because it allows quantification and characterization of potential constituents of concern in Cheney Reservoir. This report updates linear regression models published in 2006 that were based on data collected during 2001 through 2003. The update uses discrete and continuous data collected during May 2001 through December 2009. Updated models to compute dissolved solids, sodium, chloride, and suspended solids were similar to previously published models. However, several other updated models changed substantially from previously published models. In addition to updating relations that were previously developed, models also were developed for four new constituents, including magnesium, dissolved phosphorus, actinomycetes bacteria, and the cyanotoxin microcystin. In addition, a conversion factor of 0.74 was established to convert the Yellow Springs Instruments (YSI) model 6026 turbidity sensor measurements to the newer YSI
NASA Astrophysics Data System (ADS)
Maffucci, R.; Bigi, S.; Corrado, S.; Chiodi, A.; Di Paolo, L.; Giordano, G.; Invernizzi, C.
2015-04-01
We report the results of a systematic study carried out on the fracture systems exposed in the Sierra de La Candelaria anticline, in the central Andean retrowedge of northwestern Argentina. The aim was to elaborate a kinematic model of the anticline and to assess the dimensional and spatial properties of the fracture network characterizing the Cretaceous sandstone reservoir of the geothermal system of Rosario de La Frontera. Special regard was devoted to explore how tectonics may affect fluid circulation at depth and control fluids' natural upwelling at surface. With this aim we performed a Discrete Fracture Network model in order to evaluate the potential of the reservoir of the studied geothermal system. The results show that the Sierra de La Candelaria regional anticline developed according to a kinematic model of transpressional inversion compatible with the latest Andean regional WNW-ESE shortening, acting on a pre-orogenic N-S normal fault. A push-up geometry developed during positive inversion controlling the development of two minor anticlines: Termas and Balboa, separated by further NNW-SSE oblique-slip fault in the northern sector of the regional anticline. Brittle deformation recorded at the outcrop scale is robustly consistent with the extensional and transpressional events recognized at regional scale. In terms of fluid circulation, the NNW-SSE and NE-SW fault planes, associated to the late stage of the positive inversion, are considered the main structures controlling the migration paths of hot fluids from the reservoir to the surface. The results of the fracture modeling performed show that fractures related to the same deformation stage, are characterized by the highest values of secondary permeability. Moreover, the DFN models performed in the reservoir volume indicates that fracture network enhances its permeability: its secondary permeability is of about 49 mD and its fractured portion represents the 0.03% of the total volume.
Ganesan, Karthikeyan; Acharya, U Rajendra; Chua, Chua Kuang; Min, Lim Choo; Abraham, Thomas K
2014-12-01
Mammograms are one of the most widely used techniques for preliminary screening of breast cancers. There is great demand for early detection and diagnosis of breast cancer using mammograms. Texture based feature extraction techniques are widely used for mammographic image analysis. In specific, wavelets are a popular choice for texture analysis of these images. Though discrete wavelets have been used extensively for this purpose, spherical wavelets have rarely been used for Computer-Aided Diagnosis (CAD) of breast cancer using mammograms. In this work, a comparison of the performance between the features of Discrete Wavelet Transform (DWT) and Spherical Wavelet Transform (SWT) based on the classification results of normal, benign and malignant stage was studied. Classification was performed using Linear Discriminant Classifier (LDC), Quadratic Discriminant Classifier (QDC), Nearest Mean Classifier (NMC), Support Vector Machines (SVM) and Parzen Classifier (ParzenC). We have obtained a maximum classification accuracy of 81.73% for DWT and 88.80% for SWT features using SVM classifier.
Nuclear Structure and Quasi-Discrete Features populated in the 152,154Sm(p,t) Reactions
NASA Astrophysics Data System (ADS)
Humby, P.; Beausang, C. W.; Simon, A.; Cooper, N.; Wilson, E.; Gell, K.; Tarlow, T.; Vyas, G.; Ross, T. J.; Hughes, R. O.; Burke, J. T.; Casperson, R. J.; Koglin, J.; Ota, S.; Allmond, J. M.; McCleskey, M.; McCleskey, E.; Saastamoinen, A.; Chyzh, R.; Dag, M.
2016-03-01
The 152,154Sm(p,t) reactions were used to investigate large, narrow, quasi-discrete structures observed in the triton energy spectra at excitation energies of 2-3 MeV. The experiment utilized a 25 MeV proton beam from the K-150 cyclotron at the Cyclotron Institute of Texas A&M University and the outgoing charged particles and γ rays were detected using the STARLiTeR array. This consists of a highly segmented ΔE-E silicon telescope and six BGO shielded HPGe clover detectors. The angular distributions of the outgoing tritons populating the narrow structures are compared to those from both the population of low energy discrete states and the high energy continuum region. The fraction of strength in the structures accounted for by the observed discrete states and the total strength of the feature in neighboring isotopes are discussed. This work is supported by the U.S. Department of Energy No. DE-FG02-05ER41379, DE-FG52-09NA29467 and DE-NA0001801, the National Science Foundation under PHY-130581, and by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.
Features of control systems analysis with discrete control devices using mathematical packages
NASA Astrophysics Data System (ADS)
Yakovleva, E. M.; Faerman, V. A.
2017-02-01
The article contains presentation of basic provisions of the theory of automatic pulse control systems as well as methods of analysis of such systems using the mathematical software widespread in the academic environment. The pulse systems under research are considered as analogues systems interacting among themselves, including sensors, amplifiers, controlled objects, and discrete parts. To describe such systems, one uses a mathematical apparatus of difference equations as well as discrete transfer functions. To obtain a transfer function of the open-loop system, being important from the point of view of the analysis of control systems, one uses mathematical packages Mathcad and Matlab. Despite identity of the obtained result, the way of its achievement from the point of view of user’s action is various for the specified means. In particular, Matlab uses a structural model of the control system while Mathcad allows only execution of a chain of operator transforms. It is worth noting that distinctions taking place allow considering transformation of signals during interaction of the linear and continuous parts of the control system from different sides. The latter can be used in an educational process for the best assimilation of the course of the control system theory by students.
Youth with Psychopathy Features Are Not a Discrete Class: A Taxometric Analysis
ERIC Educational Resources Information Center
Murrie, Daniel C.; Marcus, David K.; Douglas, Kevin S.; Lee, Zina; Salekin, Randall T.; Vincent, Gina
2007-01-01
Background: Recently, researchers have sought to measure psychopathy-like features among youth in hopes of identifying children who may be progressing toward a particularly destructive form of adult pathology. However, it remains unclear whether psychopathy-like personality features among youth are best conceptualized as dimensional (distributed…
Wan, Chayan; Cao, Wenqing; Cheng, Cungui
2014-01-01
Sprague-Dawley (SD) rats' normal and abnormal pancreatic tissues are determined directly by attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy method. In order to diagnose earlier stage of SD rats pancreatic cancer rate with FT-IR, a novel method of extraction of FT-IR feature using discrete wavelet transformation (DWT) analysis and classification with the probability neural network (PNN) was developed. The differences between normal pancreatic and abnormal samples were identified by PNN based on the indices of 4 feature variants. When error goal was 0.01, the total correct rates of pancreatic early carcinoma and advanced carcinoma were 98% and 100%, respectively. It was practical to apply PNN on the basis of ATR-FT-IR to identify abnormal tissues. The research result shows the feasibility of establishing the models with FT-IR-DWT-PNN method to identify normal pancreatic tissues, early carcinoma tissues, and advanced carcinoma tissues. PMID:25548717
Wan, Chayan; Cao, Wenqing; Cheng, Cungui
2014-01-01
Sprague-Dawley (SD) rats' normal and abnormal pancreatic tissues are determined directly by attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy method. In order to diagnose earlier stage of SD rats pancreatic cancer rate with FT-IR, a novel method of extraction of FT-IR feature using discrete wavelet transformation (DWT) analysis and classification with the probability neural network (PNN) was developed. The differences between normal pancreatic and abnormal samples were identified by PNN based on the indices of 4 feature variants. When error goal was 0.01, the total correct rates of pancreatic early carcinoma and advanced carcinoma were 98% and 100%, respectively. It was practical to apply PNN on the basis of ATR-FT-IR to identify abnormal tissues. The research result shows the feasibility of establishing the models with FT-IR-DWT-PNN method to identify normal pancreatic tissues, early carcinoma tissues, and advanced carcinoma tissues.
Petrophysics Features of the Hydrocarbon Reservoirs in the Precambrian Crystalline Basement
NASA Astrophysics Data System (ADS)
Plotnikova, Irina
2014-05-01
A prerequisite for determining the distribution patterns of reservoir zones on the section of crystalline basement (CB) is the solution of a number of problems connected with the study of the nature and structure of empty spaces of reservoirs with crystalline basement (CB) and the impact of petrological, and tectonic factors and the intensity of the secondary transformation of rocks. We decided to choose the Novoelhovskaya well # 20009 as an object of our research because of the following factors. Firstly, the depth of the drilling of the Precambrian crystalline rocks was 4077 m ( advance heading - 5881 m) and it is a maximum for the Volga-Urals region. Secondly, petrographic cut of the well is made on core and waste water, and the latter was sampled regularly and studied macroscopically. Thirdly, a wide range of geophysical studies were performed for this well, which allowed to identify promising areas of collector with high probability. Fourth, along with geological and technical studies that were carried out continuously (including washing and bore hole redressing periods), the studies of the gaseous component of deep samples of clay wash were also carried out, which indirectly helped us estimate reservoir properties and fluid saturation permeable zones. As a result of comprehensive analysis of the stone material and the results of the geophysical studies we could confidently distinguish 5 with strata different composition and structure in the cut of the well. The dominating role in each of them is performed by rocks belonging to one of the structural-material complexes of Archean, and local variations in composition and properties are caused by later processes of granitization on different stages and high temperature diaphthoresis imposed on them. Total capacity of reservoir zones identified according to geophysical studies reached 1034.2 m, which corresponds to 25.8% of the total capacity of 5 rock masses. However, the distribution of reservoirs within the cut
NASA Astrophysics Data System (ADS)
Chen, Binqiang; Zhang, Zhousuo; Sun, Chuang; Li, Bing; Zi, Yanyang; He, Zhengjia
2012-11-01
Gearbox fault diagnosis is very important for preventing catastrophic accidents. Vibration signals of gearboxes measured by sensors are useful and dependable as they carry key information related to the mechanical faults in gearboxes. Effective signal processing techniques are in necessary demands to extract the fault features contained in the collected gearbox vibration signals. Overcomplete rational dilation discrete wavelet transform (ORDWT) enjoys attractive properties such as better shift-invariance, adjustable time-frequency distributions and flexible wavelet atoms of tunable oscillation in comparison with classical dyadic wavelet transform (DWT). Due to these advantages, ORDWT is presented as a versatile tool that can be adapted to analysis of gearbox fault features of different types, especially in analyzing the non-stationary and transient characteristics of the signals. Aiming to extract the various types of fault features confronted in gearbox fault diagnosis, a fault feature extraction technique based on ORDWT is proposed in this paper. In the routine of the proposed technique, ORDWT is used as the pre-processing decomposition tool, and a corresponding post-processing method is combined with ORDWT to extract the fault feature of a specific type. For extracting periodical impulses in the signal, an impulse matching algorithm is presented. In this algorithm, ORDWT bases of varied time-frequency distributions and varied oscillatory natures are adopted, moreover an improved signal impulsiveness measure derived from kurtosis is developed for choosing optimal ORDWT bases that perfectly match the hidden periodical impulses. For demodulation purpose, an improved instantaneous time-frequency spectrum (ITFS), based on the combination of ORDWT and Hilbert transform, is presented. For signal denoising applications, ORDWT is enhanced by neighboring coefficient shrinkage strategy as well as subband selection step to reveal the buried transient vibration contents. The
NASA Astrophysics Data System (ADS)
Gan, Yanfen; Zhong, Junliu
2015-12-01
With the aid of sophisticated photo-editing software, such as Photoshop, copy-move image forgery operation has been widely applied and has become a major concern in the field of information security in the modern society. A lot of work on detecting this kind of forgery has gained great achievements, but the detection results of geometrical transformations of copy-move regions are not so satisfactory. In this paper, a new method based on the Polar Complex Exponential Transform is proposed. This method addresses issues in image geometric moment, focusing on constructing rotation invariant moment and extracting features of the rotation invariant moment. In order to reduce rounding errors of the transform from the Polar coordinate system to the Cartesian coordinate system, a new transformation method is presented and discussed in detail at the same time. The new method constructs a 9 × 9 shrunk template to transform the Cartesian coordinate system back to the Polar coordinate system. It can reduce transform errors to a much greater degree. Forgery detection, such as copy-move image forgery detection, is a difficult procedure, but experiments prove our method is a great improvement in detecting and identifying forgery images affected by the rotated transform.
Altazi, B; Fernandez, D; Zhang, G; Biagioli, M; Moros, E; Moffitt, H. Lee
2015-06-15
Purpose: Site-specific investigations of the role of Radiomics in cancer diagnosis and therapy are needed. We report of the reproducibility of quantitative image features over different discrete voxel levels in PET/CT images of cervical cancer. Methods: Our dataset consisted of the pretreatment PET/CT scans from a cohort of 76 patients diagnosed with cervical cancer, FIGO stage IB-IVA, age range 31–76 years, treated with external beam radiation therapy to a dose range between 45–50.4 Gy (median dose: 45 Gy), concurrent cisplatin chemotherapy and MRI-based Brachytherapy to a dose of 20–30 Gy (median total dose: 28 Gy). Two board certified radiation oncologists delineated Metabolic Tumor volume (MTV) for each patient. Radiomics features were extracted based on 32, 64, 128 and 256 discretization levels (DL). The 64 level was chosen to be the reference DL. Features were calculated based on Co-occurrence (COM), Gray Level Size Zone (GLSZM) and Run-Length (RLM) matrices. Mean Percentage Differences (Δ) of features for discrete levels were determined. Normality distribution of Δ was tested using Kolomogorov - Smirnov test. Bland-Altman test was used to investigate differences between feature values measured on different DL. The mean, standard deviation and upper/lower value limits for each pair of DL were calculated. Interclass Correlation Coefficient (ICC) analysis was performed to examine the reliability of repeated measures within the context of the test re-test format. Results: 3 global and 5 regional features out of 48 features showed distribution not significantly different from a normal one. The reproducible features passed the normality test. Only 5 reproducible results were reliable, ICC range 0.7 – 0.99. Conclusion: Most of the radiomics features tested showed sensitivity to voxel level discretization between (32 – 256). Only 4 GLSZM, 3 COM and 1 RLM showed insensitivity towards mentioned discrete levels.
Zamani, Majid; Demosthenous, Andreas
2014-07-01
Next generation neural interfaces for upper-limb (and other) prostheses aim to develop implantable interfaces for one or more nerves, each interface having many neural signal channels that work reliably in the stump without harming the nerves. To achieve real-time multi-channel processing it is important to integrate spike sorting on-chip to overcome limitations in transmission bandwidth. This requires computationally efficient algorithms for feature extraction and clustering suitable for low-power hardware implementation. This paper describes a new feature extraction method for real-time spike sorting based on extrema analysis (namely positive peaks and negative peaks) of spike shapes and their discrete derivatives at different frequency bands. Employing simulation across different datasets, the accuracy and computational complexity of the proposed method are assessed and compared with other methods. The average classification accuracy of the proposed method in conjunction with online sorting (O-Sort) is 91.6%, outperforming all the other methods tested with the O-Sort clustering algorithm. The proposed method offers a better tradeoff between classification error and computational complexity, making it a particularly strong choice for on-chip spike sorting.
Shi, Shao-Ping; Qiu, Jian-Ding; Sun, Xing-Yu; Huang, Jian-Hua; Huang, Shu-Yun; Suo, Sheng-Bao; Liang, Ru-Ping; Zhang, Li
2011-03-01
It is very challenging and complicated to predict protein locations at the sub-subcellular level. The key to enhancing the prediction quality for protein sub-subcellular locations is to grasp the core features of a protein that can discriminate among proteins with different subcompartment locations. In this study, a different formulation of pseudoamino acid composition by the approach of discrete wavelet transform feature extraction was developed to predict submitochondria and subchloroplast locations. As a result of jackknife cross-validation, with our method, it can efficiently distinguish mitochondrial proteins from chloroplast proteins with total accuracy of 98.8% and obtained a promising total accuracy of 93.38% for predicting submitochondria locations. Especially the predictive accuracy for mitochondrial outer membrane and chloroplast thylakoid lumen were 82.93% and 82.22%, respectively, showing an improvement of 4.88% and 27.22% when other existing methods were compared. The results indicated that the proposed method might be employed as a useful assistant technique for identifying sub-subcellular locations. We have implemented our algorithm as an online service called SubIdent (http://bioinfo.ncu.edu.cn/services.aspx).
Jiang, Guangli; Liu, Leibo; Zhu, Wenping; Yin, Shouyi; Wei, Shaojun
2015-09-04
This paper proposes a real-time feature extraction VLSI architecture for high-resolution images based on the accelerated KAZE algorithm. Firstly, a new system architecture is proposed. It increases the system throughput, provides flexibility in image resolution, and offers trade-offs between speed and scaling robustness. The architecture consists of a two-dimensional pipeline array that fully utilizes computational similarities in octaves. Secondly, a substructure (block-serial discrete-time cellular neural network) that can realize a nonlinear filter is proposed. This structure decreases the memory demand through the removal of data dependency. Thirdly, a hardware-friendly descriptor is introduced in order to overcome the hardware design bottleneck through the polar sample pattern; a simplified method to realize rotation invariance is also presented. Finally, the proposed architecture is designed in TSMC 65 nm CMOS technology. The experimental results show a performance of 127 fps in full HD resolution at 200 MHz frequency. The peak performance reaches 181 GOPS and the throughput is double the speed of other state-of-the-art architectures.
NASA Technical Reports Server (NTRS)
Shore, Steven N.; Altner, Bruce; Bolton, C. T.; Cardelli, Jason A.; Ebbets, Dennis C.
1993-01-01
We report the observation of transient narrow absorption components (NACs) in the stellar wind of the O giant Xi Per. Two sets of GHRS observations of the Si IV ultraviolet resonance doublet have been obtained. These features are extremely weak, with column densities of approximately 10 exp 12/sq cm and optical depths of order 0.1. The features are narrow, less than 30 km/s, and seem to occur in groups. If the NACs are due to the 1393 A component, they represent previously undetected low-velocity discrete absorption components at V(rad) below -600 km/s. If they are high-velocity features on the 1402 A doublet component, they may represent the decay phase of the discrete absorption components at the terminal velocity. In either case, they are a new aspect of the NAC phenomenon that could not have been detected with previous ultraviolet spectrographs.
Nguyen, Phuong; Liu, Wei; Ma, Jing; Manirarora, Jean N.; Liu, Xin; Cheng, Cheng; Geiger, Terrence L.
2010-01-01
Regulatory T lymphocytes (Treg) expressing the Forkhead Box Transcription Factor 3 (Foxp3) are critical modulators of autoimmunity. Foxp3+ Treg may develop in the thymus as a population distinct from conventional Foxp3− αβ T cells (Tconv). Alternatively, plasticity in Foxp3 expression may allow for the interconversion of mature Treg and Tconv. We examined >160,000 TCR sequences from Foxp3+ or Foxp3− populations in the spleens or CNS of wild type mice with experimental allergic encephalomyelitis (EAE) to determine their relatedness and identify distinguishing TCR features. Our results indicate that the CNS infiltrating Treg and Tconv arise predominantly from distinct sources. The repertoires of CNS Treg or Tconv TCR showed limited overlap with heterologous populations in either the CNS or spleen, indicating that they are largely unrelated. Indeed, Treg and Tconv TCR in the CNS were significantly less related than those populations in the spleen. In contrast, CNS Treg and Tconv repertoires strongly intersected those of the homologous cell type in the spleen. High frequency sequences more likely to be disease associated showed similar results, and some public TCR demonstrated Treg or Tconv-specific motifs. Different charge characteristics and amino acid use preferences were identified in the CDR3β of Treg and Tconv infiltrating the CNS, further indicating that their repertoires are qualitatively distinct. Therefore discrete populations of Treg and Tconv that do not substantially interconvert respond during EAE. Differences in sequence and physical characteristics distinguish Treg and Tconv TCR and imply dissimilar antigen recognition properties. PMID:20810983
Stone, Mandy L.; Graham, Jennifer L.; Gatotho, Jackline W.
2013-01-01
Cheney Reservoir in south-central Kansas is one of the primary sources of water for the city of Wichita. The North Fork Ninnescah River is the largest contributing tributary to Cheney Reservoir. The U.S. Geological Survey has operated a continuous real-time water-quality monitoring station since 1998 on the North Fork Ninnescah River. Continuously measured water-quality physical properties include streamflow, specific conductance, pH, water temperature, dissolved oxygen, and turbidity. Discrete water-quality samples were collected during 1999 through 2009 and analyzed for sediment, nutrients, bacteria, and other water-quality constituents. Regression models were developed to establish relations between discretely sampled constituent concentrations and continuously measured physical properties to estimate concentrations of those constituents of interest that are not easily measured in real time because of limitations in sensor technology and fiscal constraints. Regression models were published in 2006 that were based on a different dataset collected during 1997 through 2003. This report updates those models using discrete and continuous data collected during January 1999 through December 2009. Models also were developed for five new constituents, including additional nutrient species and indicator bacteria. The water-quality information in this report is important to the city of Wichita because it allows the concentrations of many potential pollutants of interest, including nutrients and sediment, to be estimated in real time and characterized over conditions and time scales that would not be possible otherwise.
Ebrahimi, Farideh; Setarehdan, Seyed-Kamaledin; Ayala-Moyeda, Jose; Nazeran, Homer
2013-10-01
The conventional method for sleep staging is to analyze polysomnograms (PSGs) recorded in a sleep lab. The electroencephalogram (EEG) is one of the most important signals in PSGs but recording and analysis of this signal presents a number of technical challenges, especially at home. Instead, electrocardiograms (ECGs) are much easier to record and may offer an attractive alternative for home sleep monitoring. The heart rate variability (HRV) signal proves suitable for automatic sleep staging. Thirty PSGs from the Sleep Heart Health Study (SHHS) database were used. Three feature sets were extracted from 5- and 0.5-min HRV segments: time-domain features, nonlinear-dynamics features and time-frequency features. The latter was achieved by using empirical mode decomposition (EMD) and discrete wavelet transform (DWT) methods. Normalized energies in important frequency bands of HRV signals were computed using time-frequency methods. ANOVA and t-test were used for statistical evaluations. Automatic sleep staging was based on HRV signal features. The ANOVA followed by a post hoc Bonferroni was used for individual feature assessment. Most features were beneficial for sleep staging. A t-test was used to compare the means of extracted features in 5- and 0.5-min HRV segments. The results showed that the extracted features means were statistically similar for a small number of features. A separability measure showed that time-frequency features, especially EMD features, had larger separation than others. There was not a sizable difference in separability of linear features between 5- and 0.5-min HRV segments but separability of nonlinear features, especially EMD features, decreased in 0.5-min HRV segments. HRV signal features were classified by linear discriminant (LD) and quadratic discriminant (QD) methods. Classification results based on features from 5-min segments surpassed those obtained from 0.5-min segments. The best result was obtained from features using 5-min HRV
Maret, Terry R.; Schultz, Justin E.
2013-01-01
Acoustic telemetry was used to determine spring to summer (April–August) movement and habitat use of bull trout (Salvelinus confluentus) in Arrowrock Reservoir (hereafter “Arrowrock”), a highly regulated reservoir in the Boise River Basin of southwestern Idaho. Water management practices annually use about 86 percent of the reservoir water volume to satisfy downstream water demands. These practices might be limiting bull trout habitat and movement patterns. Bull trout are among the more thermally sensitive coldwater species in North America, and the species is listed as threatened throughout the contiguous United States under the Endangered Species Act. Biweekly water-temperature and dissolved-oxygen profiles were collected by the Bureau of Reclamation at three locations in Arrowrock to characterize habitat conditions for bull trout. Continuous streamflow and water temperature also were measured immediately upstream of the reservoir on the Middle and South Fork Boise Rivers, which influence habitat conditions in the riverine zones of the reservoir. In spring 2012, 18 bull trout ranging in total length from 306 to 630 millimeters were fitted with acoustic transmitters equipped with temperature and depth sensors. Mobile boat tracking and fixed receivers were used to detect released fish. Fish were tagged from March 28 to April 20 and were tracked through most of August. Most bull trout movements were detected in the Middle Fork Boise River arm of the reservoir. Fifteen individual fish were detected at least once after release. Water surface temperature at each fish detection location ranged from 6.0 to 16.2 degrees Celsius (°C) (mean=10.1°C), whereas bull trout body temperatures were colder, ranging from 4.4 to 11.6°C (mean=7.3°C). Bull trout were detected over deep-water habitat, ranging from 8.0 to 42.6 meters (m) (mean=18.1 m). Actual fish depths were shallower than total water depth, ranging from 0.0 to 24.5 m (mean=6.7 m). The last bull trout was
Janice Gillespie
2004-11-01
Late Neogene (Plio-Pleistocene) shallow marine strata of the western Bakersfield Arch and Elk Hills produce hydrocarbons from several different reservoirs. This project focuses on the shallow marine deposits of the Gusher and Calitroleum reservoirs in the Lower Shallow Oil Zone (LSOZ). In the eastern part of the study area on the Bakersfield Arch at North and South Coles Levee field and in two wells in easternmost Elk Hills, the LSOZ reservoirs produce dry (predominantly methane) gas. In structurally higher locations in western Elk Hills, the LSOZ produces oil and associated gas. Gas analyses show that gas from the eastern LSOZ is bacterial and formed in place in the reservoirs, whereas gas associated with oil in the western part of the study area is thermogenic and migrated into the sands from deeper in the basin. Regional mapping shows that the gas-bearing LSOZ sands in the Coles Levee and easternmost Elk Hills area are sourced from the Sierra Nevada to the east whereas the oil-bearing sands in western Elk Hills appear to be sourced from the west. The eastern Elk Hills area occupied the basin depocenter, farthest from either source area. As a result, it collected mainly low-permeability offshore shale deposits. This sand-poor depocenter provides an effective barrier to the updip migration of gases from east to west. The role of small, listric normal faults as migration barriers is more ambiguous. Because our gas analyses show that the gas in the eastern LSOZ reservoirs is bacterial, it likely formed in-place near the reservoirs and did not have to migrate far. Therefore, the gas could have been generated after faulting and accumulated within the fault blocks as localized pools. However, bacterial gas is present in both the eastern AND western parts of Elk Hills in the Dry Gas Zone (DGZ) near the top of the stratigraphic section even though the measured fault displacement is greatest in this zone. Bacterial gas is not present in the west in the deeper LSOZ which
Vanniyasingam, Thuva; Cunningham, Charles E; Foster, Gary; Thabane, Lehana
2016-01-01
Objectives Discrete choice experiments (DCEs) are routinely used to elicit patient preferences to improve health outcomes and healthcare services. While many fractional factorial designs can be created, some are more statistically optimal than others. The objective of this simulation study was to investigate how varying the number of (1) attributes, (2) levels within attributes, (3) alternatives and (4) choice tasks per survey will improve or compromise the statistical efficiency of an experimental design. Design and methods A total of 3204 DCE designs were created to assess how relative design efficiency (d-efficiency) is influenced by varying the number of choice tasks (2–20), alternatives (2–5), attributes (2–20) and attribute levels (2–5) of a design. Choice tasks were created by randomly allocating attribute and attribute level combinations into alternatives. Outcome Relative d-efficiency was used to measure the optimality of each DCE design. Results DCE design complexity influenced statistical efficiency. Across all designs, relative d-efficiency decreased as the number of attributes and attribute levels increased. It increased for designs with more alternatives. Lastly, relative d-efficiency converges as the number of choice tasks increases, where convergence may not be at 100% statistical optimality. Conclusions Achieving 100% d-efficiency is heavily dependent on the number of attributes, attribute levels, choice tasks and alternatives. Further exploration of overlaps and block sizes are needed. This study's results are widely applicable for researchers interested in creating optimal DCE designs to elicit individual preferences on health services, programmes, policies and products. PMID:27436671
Insight from modelling discrete fractures using GEOCRACK
DuTeaux, Robert; Swenson, Daniel; Hardeman, Brian
1996-01-24
This work analyzes the behavior of a numerical geothermal reservoir simulation with flow only in discrete fractures. GEOCRACK is a 2-D finite element model developed at Kansas State University for the Hot Dry Rock (HDR) research at Los Alamos National Laboratory. Its numerical simulations couple the mechanics of discrete fracture behavior with the state of earth stress, fluid flow, and heat transfer. This coupled model could also be of value for modeling reinjection and other reservoir operating strategies for liquid dominated fractured reservoirs. Because fracture surfaces cool quickly by fluid convection, and heat does not conduct quickly from the interior of reservoir rock, modeling the injection of cold fluid into a fractured reservoir is better simulated by a model with discrete fractures. This work contains knowledge gained from HDR reservoir simulation and continues to develop the general concept of heat mining, reservoir optimization. and the sensitivity of simulation to the uncertainties of fracture spacing and dynamic flow dispersion.
Reservoir microseismicity at the Ekofisk Oil Field
Rutledge, J.T.; Fairbanks, T.D.; Albright, J.N.; Boade, R.R.; Dangerfield, J.; Landa, G.H.
1994-07-01
A triaxial, downhole geophone was deployed within the Ekofisk oil reservoir for monitoring ambient microseismicity as a test to determine if microearthquake signals generated from discrete shear failure of the reservoir rock could be detected. The results of the test were positive. During 104 hours of monitoring, 572 discrete events were recorded which have been identified as shear-failure microearthquakes. Reservoir microseismicity was detected at large distances (1000 m) from the monitor borehole and at rates (> 5 events per hour) which may allow practical characterization of the reservoir rock and overburden deformation induced by reservoir pressure changes.
NASA Astrophysics Data System (ADS)
Fan, Zifei; Wang, Shuqin; Liu, Lingli; Li, Jianxin; Zhao, Wenqi; Sun, Meng
2017-01-01
Identifying the carbonate reservoirs has always been a challenge to geological exploration, while reasonable classification of flow units is the bottleneck in this exploitation. While taking the NT oil field at the eastern edge of Pre-Caspian Basin as an example, this paper proposes the classification of flow units into five categories based on previous flow-unit classification theory and actual oilfield features by using the pore throat radius at the mercury injection saturation of 35% as the main judging criterion. In this paper, the features of various flow units have also been analyzed. The type-I flow units, mainly found in dolomite and algal reef limestone reservoirs, have the highest production capacity. Given the existence of corrosion and dolomitization, they are mainly fracture-cave composite reservoirs or fracture pore reservoirs. As far as the type-I flow units are concerned, the flow index is > 1.42 for KT-I stratum and > 1.55 for KT-II stratum. The production capacity and reservoir quality of type-II-IV flow units would decline in turn. The type-V flow units are argillaceous limestone, with a very low production capacity and a flow index being 0.01-0.05 for KT-I and 0.03-0.05 for KT-II.
Spatial data discretization methods for geocomputation
NASA Astrophysics Data System (ADS)
Cao, Feng; Ge, Yong; Wang, Jinfeng
2014-02-01
Geocomputation provides solutions to complex geographic problems. Continuous and discrete spatial data are involved in the geocomputational process; however, geocomputational methods for discrete spatial data cannot be directly applied to continuous or mixed spatial data. Therefore, discretization methods for continuous or mixed spatial data are involved in the process. Since spatial data has spatial features, such as association, heterogeneity and spatial structure, these features cannot be handled by traditional discretization methods. Therefore, this work develops feature-based spatial data discretization methods that achieve optimal discretization results for spatial data using spatial information implicit in those features. Two discretization methods considering the features of spatial data are presented. One is an unsupervised method considering autocorrelation of spatial data and the other is a supervised method considering spatial heterogeneity. Discretization processes of the two methods are exemplified using neural tube defects (NTD) for Heshun County in Shanxi Province, China. Effectiveness is also assessed.
Integrable discrete PT symmetric model.
Ablowitz, Mark J; Musslimani, Ziad H
2014-09-01
An exactly solvable discrete PT invariant nonlinear Schrödinger-like model is introduced. It is an integrable Hamiltonian system that exhibits a nontrivial nonlinear PT symmetry. A discrete one-soliton solution is constructed using a left-right Riemann-Hilbert formulation. It is shown that this pure soliton exhibits unique features such as power oscillations and singularity formation. The proposed model can be viewed as a discretization of a recently obtained integrable nonlocal nonlinear Schrödinger equation.
Reservoir Temperature Estimator
Palmer, Carl D.
2014-12-08
The Reservoir Temperature Estimator (RTEst) is a program that can be used to estimate deep geothermal reservoir temperature and chemical parameters such as CO2 fugacity based on the water chemistry of shallower, cooler reservoir fluids. This code uses the plugin features provided in The Geochemists Workbench (Bethke and Yeakel, 2011) and interfaces with the model-independent parameter estimation code Pest (Doherty, 2005) to provide for optimization of the estimated parameters based on the minimization of the weighted sum of squares of a set of saturation indexes from a user-provided mineral assemblage.
Yamauchi, Yoshihiro; Yoshizawa, Michito; Akita, Munetaka; Fujita, Makoto
2009-06-30
Three polarized aromatic guest molecules (pyrene-4,5-dione, 1) form a triple-layered stack in the box-shaped cavity of an organic pillared coordination cage in water. The cavity size strictly limits the number of stacked planar guests but does not restrict guest orientation, and thus enables the study of discrete stacks of polarized guests and their preferred conformations. Crystallographic study shows that the guest molecules in the cavity are rotated 120 degrees with respect to each other, cancelling the net dipole moment rather than the local dipole moment. The unique conformation of a discrete, triple stack of 1 sharply contrasts to the standard head-to-tail conformation in infinite stacks of 1.
Umbral Deformations on Discrete SPACE TIME
NASA Astrophysics Data System (ADS)
Zachos, Cosmas K.
Given a minimum measurable length underlying spacetime, the latter may be effectively regarded as discrete, at scales of order the Planck length. A systematic discretization of continuum physics may be effected most efficiently through the umbral deformation. General functionals yielding such deformations at the level of solutions are furnished and illustrated, and broad features of discrete oscillations and wave propagation are outlined.
Jin, Wenying; Wan, Chayan; Cheng, Cungui
2015-01-01
The attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was employed to acquire the infrared spectra of Radix Bupleuri and its unofficial varieties: the root of Bupleurum smithii Wolff and the root of Bupleurum bicaule Helm. The infrared spectra and spectra of Fourier self-deconvolution (FSD), discrete wavelet transform (DWT), and probability neural network (PNN) of these species were analyzed. By the method of FSD, there were conspicuous differences of the infrared absorption peak intensity of different types between Radix Bupleuri and its unofficial varieties. But it is hard to tell the differences between the root of Bupleurum smithii Wolff and the root of Bupleurum bicaule. The differences could be shown more clearly when the DWT was used. The research result shows that by the DWT technology it is easier to identify Radix Bupleuri from its unofficial varieties the root of Bupleurum smithii Wolff and the root of Bupleurum bicaule.
Discrete cloud structure on Neptune
NASA Technical Reports Server (NTRS)
Hammel, H. B.
1989-01-01
Recent CCD imaging data for the discrete cloud structure of Neptune shows that while cloud features at CH4-band wavelengths are manifest in the southern hemisphere, they have not been encountered in the northern hemisphere since 1986. A literature search has shown the reflected CH4-band light from the planet to have come from a single discrete feature at least twice in the last 10 years. Disk-integrated photometry derived from the imaging has demonstrated that a bright cloud feature was responsible for the observed 8900 A diurnal variation in 1986 and 1987.
Carbonate petroleum reservoirs
Roehl, P.O.; Choquette, P.W.
1985-01-01
This book presents papers on the geology of petroleum deposits. Topics considered include diagenesis, porosity, dolomite reservoirs, deposition, reservoir rock, reefs, morphology, fracture-controlled production, Cenozoic reservoirs, Mesozoic reservoirs, and Paleozoic reservoirs.
Piao, Xianyu; Hou, Nan; Gobert, Geoffrey N.; McManus, Donald P.; Chen, Qijun
2016-01-01
Schistosomiasis is a chronic and debilitating disease caused by blood flukes (digenetic trematodes) of the genus Schistosoma. Schistosomes are sexually dimorphic and exhibit dramatic morphological changes during a complex lifecycle which requires subtle gene regulatory mechanisms to fulfil these complex biological processes. In the current study, a 41,982 features custom DNA microarray, which represents the most comprehensive probe coverage for any schistosome transcriptome study, was designed based on public domain and local databases to explore differential gene expression in S. japonicum. We found that approximately 1/10 of the total annotated genes in the S. japonicum genome are differentially expressed between adult males and females. In general, genes associated with the cytoskeleton, and motor and neuronal activities were readily expressed in male adult worms, whereas genes involved in amino acid metabolism, nucleotide biosynthesis, gluconeogenesis, glycosylation, cell cycle processes, DNA synthesis and genome fidelity and stability were enriched in females. Further, miRNAs target sites within these gene sets were predicted, which provides a scenario whereby the miRNAs potentially regulate these sex-biased expressed genes. The study significantly expands the expressional and regulatory characteristics of gender-biased expressed genes in schistosomes with high accuracy. The data provide a better appreciation of the biological and physiological features of male and female schistosome parasites, which may lead to novel vaccine targets and the development of new therapeutic interventions. PMID:27128440
Compartmentalization analysis using discrete fracture network models
La Pointe, P.R.; Eiben, T.; Dershowitz, W.; Wadleigh, E.
1997-08-01
This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph the theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.
Compartmentalization analysis using discrete fracture network models
La Pointe, P.R.; Eiben, T.; Dershowitz, W.; Wadleigh, E.
1997-12-31
This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.
What is the Effect of Interannual Hydroclimatic Variability on Water Supply Reservoir Operations?
NASA Astrophysics Data System (ADS)
Galelli, S.; Turner, S. W. D.
2015-12-01
Rather than deriving from a single distribution and uniform persistence structure, hydroclimatic data exhibit significant trends and shifts in their mean, variance, and lagged correlation through time. Consequentially, observed and reconstructed streamflow records are often characterized by features of interannual variability, including long-term persistence and prolonged droughts. This study examines the effect of these features on the operating performance of water supply reservoirs. We develop a Stochastic Dynamic Programming (SDP) model that can incorporate a regime-shifting climate variable. We then compare the performance of operating policies—designed with and without climate variable—to quantify the contribution of interannual variability to standard policy sub-optimality. The approach uses a discrete-time Markov chain to partition the reservoir inflow time series into small number of 'hidden' climate states. Each state defines a distinct set of inflow transition probability matrices, which are used by the SDP model to condition the release decisions on the reservoir storage, current-period inflow and hidden climate state. The experimental analysis is carried out on 99 hypothetical water supply reservoirs fed from pristine catchments in Australia—all impacted by the Millennium drought. Results show that interannual hydroclimatic variability is a major cause of sub-optimal hedging decisions. The practical import is that conventional optimization methods may misguide operators, particularly in regions susceptible to multi-year droughts.
NASA Astrophysics Data System (ADS)
Taneja, Ankur; Higdon, Jonathan
2016-11-01
A spectral element method (SEM) is presented to simulate two-phase fluid flow (oil and water phase) in petroleum reservoirs. Petroleum reservoirs are porous media with heterogeneous geologic features, and the flow of two immiscible phases involves sharp, moving interfaces. The governing equations of motion are time-dependent, non-linear PDEs with strong hyperbolic nature. A fully-coupled numerical scheme using discontinuous Galerkin (DG) method with nodal spectral element basis functions for spatial discretization, and an implicit Runge-Kutta type time-stepping is developed to solve the PDEs in a robust, stable manner. Isoparameteric mapping is used to generate grids for reservoir and well geometry. We present the performance capabilities of the DG scheme with high-order basis functions to accurately resolve sharp fluid interfaces and a variety of heterogeneous geologic features. High-order convergence of SEM is demonstrated. Numerical results are presented for reservoir flows with various injection-production patterns. Typical reservoir heterogeneities like low-permeable regions, impermeable shale barriers, etc. are included in the numerical tests. Comparisons with commonly used finite volume methods and linear and quadratic finite element methods are presented. ExxonMobil Upstream Research Co.
Discrete bisoliton fiber laser
Liu, X. M.; Han, X. X.; Yao, X. K.
2016-01-01
Dissipative solitons, which result from the intricate balance between dispersion and nonlinearity as well as gain and loss, are of the fundamental scientific interest and numerous important applications. Here, we report a fiber laser that generates bisoliton – two consecutive dissipative solitons that preserve a fixed separation between them. Deviations from this separation result in its restoration. It is also found that these bisolitons have multiple discrete equilibrium distances with the quantized separations, as is confirmed by the theoretical analysis and the experimental observations. The main feature of our laser is the anomalous dispersion that is increased by an order of magnitude in comparison to previous studies. Then the spectral filtering effect plays a significant role in pulse-shaping. The proposed laser has the potential applications in optical communications and high-resolution optics for coding and transmission of information in higher-level modulation formats. PMID:27767075
Discrete bisoliton fiber laser
NASA Astrophysics Data System (ADS)
Liu, X. M.; Han, X. X.; Yao, X. K.
2016-10-01
Dissipative solitons, which result from the intricate balance between dispersion and nonlinearity as well as gain and loss, are of the fundamental scientific interest and numerous important applications. Here, we report a fiber laser that generates bisoliton – two consecutive dissipative solitons that preserve a fixed separation between them. Deviations from this separation result in its restoration. It is also found that these bisolitons have multiple discrete equilibrium distances with the quantized separations, as is confirmed by the theoretical analysis and the experimental observations. The main feature of our laser is the anomalous dispersion that is increased by an order of magnitude in comparison to previous studies. Then the spectral filtering effect plays a significant role in pulse-shaping. The proposed laser has the potential applications in optical communications and high-resolution optics for coding and transmission of information in higher-level modulation formats.
NASA Technical Reports Server (NTRS)
1986-01-01
This false-color Voyager picture of Uranus shows a discrete cloud seen as a bright streak near the planet's limb. The picture is a highly processed composite of three images obtained Jan. 14, 1986, when the spacecraft was 12.9 million kilometers (8.0 million miles) from the planet. The cloud visible here is the most prominent feature seen in a series of Voyager images designed to track atmospheric motions. (The occasional donut-shaped features, including one at the bottom, are shadows cast by dust in the camera optics; the processing necessary to bring out the faint features on the planet also brings out these camera blemishes.) Three separate images were shuttered through violet, blue and orange filters. Each color image showed the cloud to a different degree; because they were not exposed at exactly the same time, the images were processed to provide a correction for a good spatial match. In a true-color image, the cloud would be barely discernible; the false color helps bring out additional details. The different colors imply variations in vertical structure, but as yet is not possible to be specific about such differences. One possibility is that the Uranian atmosphere contains smog-like constituents, in which case some color differences may represent differences in how these molecules are distributed. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.
Interactive reservoir simulation
Regtien, J.M.M. Por, G.J.A.; Stiphout, M.T. van; Vlugt, F.F. van der
1995-12-31
Shell`s new Modular Reservoir Simulator (MoReS) has been equipped with a comprehensive and versatile user interface called FrontEnd. Apart from providing a user-friendly environment for interactive reservoir simulation, FrontEnd serves a software platform for other dynamic simulation and reservoir-engineering applications. It offers to all supported applications a common user interface, enables the re-use of code and reduces overall maintenance and support costs associated with the embedded applications. Because of its features, FrontEnd facilitates the transfer of research results in the form of operational software to end users. When coupled with MoReS, FrontEnd can be used for pre- and post-processing and interactive simulation. The pre-processing options allow data to be inputted by means of various OSF/Motif widgets containing a spreadsheet, text editors, dialogues and graphical input. The display of the input data as well as the post-processing of all simulation results is made possible by a variety of user-defined plot of tabular (e.g. timestep summary) and array (simulation grid) data. During a simulation user-defined plots can be displayed and edited, allowing a close inspection of the results as they are being calculated. FrontEnd has been equipped with a powerful input command language, which gives the batch user as much flexibility and control over the input as the interactive user.
On-line Optimization-Based Simulators for Fractured and Non-fractured Reservoirs
Milind D. Deo
2005-08-31
Oil field development is a multi-million dollar business. Reservoir simulation is often used to guide the field management and development process. Reservoir characterization and geologic modeling tools have become increasingly sophisticated. As a result the geologic models produced are complex. Most reservoirs are fractured to a certain extent. The new geologic characterization methods are making it possible to map features such as faults and fractures, field-wide. Significant progress has been made in being able to predict properties of the faults and of the fractured zones. Traditionally, finite difference methods have been employed in discretizing the domains created by geologic means. For complex geometries, finite-element methods of discretization may be more suitable. Since reservoir simulation is a mature science, some of the advances in numerical methods (linear, nonlinear solvers and parallel computing) have not been fully realized in the implementation of most of the simulators. The purpose of this project was to address some of these issues. {sm_bullet} One of the goals of this project was to develop a series of finite-element simulators to handle problems of complex geometry, including systems containing faults and fractures. {sm_bullet} The idea was to incorporate the most modern computing tools; use of modular object-oriented computer languages, the most sophisticated linear and nonlinear solvers, parallel computing methods and good visualization tools. {sm_bullet} One of the tasks of the project was also to demonstrate the construction of fractures and faults in a reservoir using the available data and to assign properties to these features. {sm_bullet} Once the reservoir model is in place, it is desirable to find the operating conditions, which would provide the best reservoir performance. This can be accomplished by utilization optimization tools and coupling them with reservoir simulation. Optimization-based reservoir simulation was one of the
Principles of Discrete Time Mechanics
NASA Astrophysics Data System (ADS)
Jaroszkiewicz, George
2014-04-01
1. Introduction; 2. The physics of discreteness; 3. The road to calculus; 4. Temporal discretization; 5. Discrete time dynamics architecture; 6. Some models; 7. Classical cellular automata; 8. The action sum; 9. Worked examples; 10. Lee's approach to discrete time mechanics; 11. Elliptic billiards; 12. The construction of system functions; 13. The classical discrete time oscillator; 14. Type 2 temporal discretization; 15. Intermission; 16. Discrete time quantum mechanics; 17. The quantized discrete time oscillator; 18. Path integrals; 19. Quantum encoding; 20. Discrete time classical field equations; 21. The discrete time Schrodinger equation; 22. The discrete time Klein-Gordon equation; 23. The discrete time Dirac equation; 24. Discrete time Maxwell's equations; 25. The discrete time Skyrme model; 26. Discrete time quantum field theory; 27. Interacting discrete time scalar fields; 28. Space, time and gravitation; 29. Causality and observation; 30. Concluding remarks; Appendix A. Coherent states; Appendix B. The time-dependent oscillator; Appendix C. Quaternions; Appendix D. Quantum registers; References; Index.
Commutation Relations and Discrete Garnier Systems
NASA Astrophysics Data System (ADS)
Ormerod, Christopher M.; Rains, Eric M.
2016-11-01
We present four classes of nonlinear systems which may be considered discrete analogues of the Garnier system. These systems arise as discrete isomonodromic deformations of systems of linear difference equations in which the associated Lax matrices are presented in a factored form. A system of discrete isomonodromic deformations is completely determined by commutation relations between the factors. We also reparameterize these systems in terms of the image and kernel vectors at singular points to obtain a separate birational form. A distinguishing feature of this study is the presence of a symmetry condition on the associated linear problems that only appears as a necessary feature of the Lax pairs for the least degenerate discrete Painlevé equations.
Tree Ensembles on the Induced Discrete Space.
Yildiz, Olcay Taner
2016-05-01
Decision trees are widely used predictive models in machine learning. Recently, K -tree is proposed, where the original discrete feature space is expanded by generating all orderings of values of k discrete attributes and these orderings are used as the new attributes in decision tree induction. Although K -tree performs significantly better than the proper one, their exponential time complexity can prohibit their use. In this brief, we propose K -forest, an extension of random forest, where a subset of features is selected randomly from the induced discrete space. Simulation results on 17 data sets show that the novel ensemble classifier has significantly lower error rate compared with the random forest based on the original feature space.
Discrete Gabor Filters For Binocular Disparity Measurement
NASA Technical Reports Server (NTRS)
Weiman, Carl F. R.
1995-01-01
Discrete Gabor filters proposed for use in determining binocular disparity - difference between positions of same feature or object depicted in stereoscopic images produced by two side-by-side cameras aimed in parallel. Magnitude of binocular disparity used to estimate distance from cameras to feature or object. In one potential application, cameras charge-coupled-device video cameras in robotic vision system, and binocular disparities and distance estimates used as control inputs - for example, to control approaches to objects manipulated or to maintain safe distances from obstacles. Binocular disparities determined from phases of discretized Gabor transforms.
NASA Astrophysics Data System (ADS)
Cashman, Katharine V.; Giordano, Guido
2014-11-01
Large caldera-forming eruptions have long been a focus of both petrological and volcanological studies; petrologists have used the eruptive products to probe conditions of magma storage (and thus processes that drive magma evolution), while volcanologists have used them to study the conditions under which large volumes of magma are transported to, and emplaced on, the Earth's surface. Traditionally, both groups have worked on the assumption that eruptible magma is stored within a single long-lived melt body. Over the past decade, however, advances in analytical techniques have provided new views of magma storage regions, many of which provide evidence of multiple melt lenses feeding a single eruption, and/or rapid pre-eruptive assembly of large volumes of melt. These new petrological views of magmatic systems have not yet been fully integrated into volcanological perspectives of caldera-forming eruptions. Here we explore the implications of complex magma reservoir configurations for eruption dynamics and caldera formation. We first examine mafic systems, where stacked-sill models have long been invoked but which rarely produce explosive eruptions. An exception is the 2010 eruption of Eyjafjallajökull volcano, Iceland, where seismic and petrologic data show that multiple sills at different depths fed a multi-phase (explosive and effusive) eruption. Extension of this concept to larger mafic caldera-forming systems suggests a mechanism to explain many of their unusual features, including their protracted explosivity, spatially variable compositions and pronounced intra-eruptive pauses. We then review studies of more common intermediate and silicic caldera-forming systems to examine inferred conditions of magma storage, time scales of melt accumulation, eruption triggers, eruption dynamics and caldera collapse. By compiling data from large and small, and crystal-rich and crystal-poor, events, we compare eruptions that are well explained by simple evacuation of a zoned
Morris, J; Johnson, S
2007-12-03
The Distinct Element Method (also frequently referred to as the Discrete Element Method) (DEM) is a Lagrangian numerical technique where the computational domain consists of discrete solid elements which interact via compliant contacts. This can be contrasted with Finite Element Methods where the computational domain is assumed to represent a continuum (although many modern implementations of the FEM can accommodate some Distinct Element capabilities). Often the terms Discrete Element Method and Distinct Element Method are used interchangeably in the literature, although Cundall and Hart (1992) suggested that Discrete Element Methods should be a more inclusive term covering Distinct Element Methods, Displacement Discontinuity Analysis and Modal Methods. In this work, DEM specifically refers to the Distinct Element Method, where the discrete elements interact via compliant contacts, in contrast with Displacement Discontinuity Analysis where the contacts are rigid and all compliance is taken up by the adjacent intact material.
Not Available
1990-09-01
This is one in a series of reports prepared by the Tennessee Valley Authority (TVA) for those interested in the conditions of TVA reservoirs. This overview of Norris Reservoir summarizes reservoir and watershed characteristics, reservoir uses, conditions that impair reservoir uses, water quality and aquatic biological conditions, and activities of reservoir management agencies. This information was extracted from the most up-to-date publications and data available, and from interviews with water resource professionals in various federal, state, and local agencies, and in public and private water supply and wastewater treatment facilities. 14 refs., 3 figs.
Synchronous Discrete Harmonic Oscillator
Antippa, Adel F.; Dubois, Daniel M.
2008-10-17
We introduce the synchronous discrete harmonic oscillator, and present an analytical, numerical and graphical study of its characteristics. The oscillator is synchronous when the time T for one revolution covering an angle of 2{pi} in phase space, is an integral multiple N of the discrete time step {delta}t. It is fully synchronous when N is even. It is pseudo-synchronous when T/{delta}t is rational. In the energy conserving hyperincursive representation, the phase space trajectories are perfectly stable at all time scales, and in both synchronous and pseudo-synchronous modes they cycle through a finite number of phase space points. Consequently, both the synchronous and the pseudo-synchronous hyperincursive modes of time-discretization provide a physically realistic and mathematically coherent, procedure for dynamic, background independent, discretization of spacetime. The procedure is applicable to any stable periodic dynamical system, and provokes an intrinsic correlation between space and time, whereby space-discretization is a direct consequence of background-independent time-discretization. Hence, synchronous discretization moves the formalism of classical mechanics towards that of special relativity. The frequency of the hyperincursive discrete harmonic oscillator is ''blue shifted'' relative to its continuum counterpart. The frequency shift has the precise value needed to make the speed of the system point in phase space independent of the discretizing time interval {delta}t. That is the speed of the system point is the same on the polygonal (in the discrete case) and the circular (in the continuum case) phase space trajectories.
Synchronous Discrete Harmonic Oscillator
NASA Astrophysics Data System (ADS)
Antippa, Adel F.; Dubois, Daniel M.
2008-10-01
We introduce the synchronous discrete harmonic oscillator, and present an analytical, numerical and graphical study of its characteristics. The oscillator is synchronous when the time T for one revolution covering an angle of 2π in phase space, is an integral multiple N of the discrete time step Δt. It is fully synchronous when N is even. It is pseudo-synchronous when T/Δt is rational. In the energy conserving hyperincursive representation, the phase space trajectories are perfectly stable at all time scales, and in both synchronous and pseudo-synchronous modes they cycle through a finite number of phase space points. Consequently, both the synchronous and the pseudo-synchronous hyperincursive modes of time-discretization provide a physically realistic and mathematically coherent, procedure for dynamic, background independent, discretization of spacetime. The procedure is applicable to any stable periodic dynamical system, and provokes an intrinsic correlation between space and time, whereby space-discretization is a direct consequence of background-independent time-discretization. Hence, synchronous discretization moves the formalism of classical mechanics towards that of special relativity. The frequency of the hyperincursive discrete harmonic oscillator is "blue shifted" relative to its continuum counterpart. The frequency shift has the precise value needed to make the speed of the system point in phase space independent of the discretizing time interval Δt. That is the speed of the system point is the same on the polygonal (in the discrete case) and the circular (in the continuum case) phase space trajectories.
Discrete dislocations in graphene
NASA Astrophysics Data System (ADS)
Ariza, M. P.; Ortiz, M.
2010-05-01
In this work, we present an application of the theory of discrete dislocations of Ariza and Ortiz (2005) to the analysis of dislocations in graphene. Specifically, we discuss the specialization of the theory to graphene and its further specialization to the force-constant model of Aizawa et al. (1990). The ability of the discrete-dislocation theory to predict dislocation core structures and energies is critically assessed for periodic arrangements of dislocation dipoles and quadrupoles. We show that, with the aid of the discrete Fourier transform, those problems are amenable to exact solution within the discrete-dislocation theory, which confers the theory a distinct advantage over conventional atomistic models. The discrete dislocations exhibit 5-7 ring core structures that are consistent with observation and result in dislocation energies that fall within the range of prediction of other models. The asymptotic behavior of dilute distributions of dislocations is characterized analytically in terms of a discrete prelogarithmic energy tensor. Explicit expressions for this discrete prelogarithmic energy tensor are provided up to quadratures.
NASA Astrophysics Data System (ADS)
Aydin, Alhun; Sisman, Altug
2016-03-01
By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they're almost completely flattened out after summation or integration operation. It's seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl's conjecture always preserve their lower error characteristic.
Innovative techniques for the description of reservoir heterogeneity using tracers
Pope, G.; Sepehrnoori, K.
1991-09-01
The objective of this research is to develop an advanced, innovative technique for the description of reservoir heterogeneity. This proposed method consists of using tracers in single-well backflow tests. The general idea is to make use of fluid drift in the reservoir either due to naturally occurring pressure gradients in the reservoir, or by deliberately imposed pressure gradients using adjacent injection and production wells in the same reservoir. The analytical tool that will be used to design and interpret these tests is a compositional reservoir simulator with special features added and tested specifically for this purpose. 2 refs., 5 figs.
Method of extracting heat from dry geothermal reservoirs
Potter, R.M.; Robinson, E.S.; Smith, M.C.
1974-01-22
Hydraulic fracturing is used to interconnect two or more holes that penetrate a previously dry geothermal reservoir, and to produce within the reservoir a sufficiently large heat-transfer surface so that heat can be extracted from the reservoir at a usefully high rate by a fluid entering it through one hole and leaving it through another. Introduction of a fluid into the reservoir to remove heat from it and establishment of natural (unpumped) convective circulation through the reservoir to accomplish continuous heat removal are important and novel features of the method. (auth)
ERIC Educational Resources Information Center
Peters, James V.
2004-01-01
Using the methods of finite difference equations the discrete analogue of the parabolic and catenary cable are analysed. The fibonacci numbers and the golden ratio arise in the treatment of the catenary.
ERIC Educational Resources Information Center
Crisler, Nancy; Froelich, Gary
1990-01-01
Discussed are summary recommendations concerning the integration of some aspects of discrete mathematics into existing secondary mathematics courses. Outlines of course activities are grouped into the three levels of prealgebra, algebra, and geometry. Some sample problems are included. (JJK)
Not Available
1990-08-01
This is the first in a series of reports prepared by Tennessee Valley Authority (TVA) for those interested in the conditions of TVA reservoirs. This overviews of Cherokee Reservoir summarizes reservoir and watershed characteristics, reservoir uses and use impairments, water quality and aquatic biological conditions, and activities of reservoir management agencies. This information was extracted from the most current reports, publications, and data available, and interviews with water resource professionals in various Federal, state, and local agencies and in public and private water supply and wastewater treatment facilities. 11 refs., 4 figs., 1 tab.
Not Available
1990-09-01
This is one in a series of status reports prepared by the Tennessee Valley Authority (TVA) for those interested in the conditions of TVA reservoirs. This overview of Wheeler Reservoir summarizes reservoir purposes and operation, reservoir and watershed characteristics, reservoir uses and use impairments, and water quality and aquatic biological conditions. The information presented here is from the most recent reports, publications, and original data available. If no recent data were available, historical data were summarized. If data were completely lacking, environmental professionals with special knowledge of the resource were interviewed. 12 refs., 2 figs.
Integration of reservoir simulation and geomechanics
NASA Astrophysics Data System (ADS)
Zhao, Nan
Fluid production from tight and shale gas formations has increased significantly, and this unconventional portfolio of low-permeability reservoirs accounts for more than half of the gas produced in the United States. Stimulation and hydraulic fracturing are critical in making these systems productive, and hence it is important to understand the mechanics of the reservoir. When modeling fractured reservoirs using discrete-fracture network representation, the geomechanical effects are expected to have a significant impact on important reservoir characteristics. It has become more accepted that fracture growth, particularly in naturally fractured reservoirs with extremely low permeability, cannot be reliably represented by conventional planar representations. Characterizing the evolution of multiple, nonplanar, interconnected and possibly nonvertical hydraulic fractures requires hydraulic and mechanical characterization of the matrix, as well as existing latent or healed fracture networks. To solve these challenging problems, a reservoir simulator (Advanced Reactive Transport Simulator (ARTS)) capable of performing unconventional reservoir simulation is developed in this research work. A geomechanical model has been incorporated into the simulation framework with various coupling schemes and this model is used to understand the geomechanical effects in unconventional oil and gas recovery. This development allows ARTS to accept geomechanical information from external geomechanical simulators (soft coupling) or the solution of the geomechanical coupled problem (hard coupling). An iterative solution method of the flow and geomechanical equations has been used in implementing the hard coupling scheme. The hard coupling schemes were verified using one-dimensional and two-dimensional analytical solutions. The new reservoir simulator is applied to learn the influence of geomechanical impact on unconventional oil and gas production in a number of practical recovery scenarios
Dolomite reservoirs: Porosity evolution and reservoir characteristics
Sun, S.Q.
1995-02-01
Systematic analyses of the published record of dolomite reservoirs worldwide reveal that the majority of hydrocarbon-producing dolomite reservoirs occurs in (1) peritidal-dominated carbonate, (2) subtidal carbonate associated with evaporitic tidal flat/lagoon, (3) subtidal carbonate associated with basinal evaporite, and (4) nonevaporitic carbonate sequence associated with topographic high/unconformity, platform-margin buildup or fault/fracture. Reservoir characteristics vary greatly from one dolomite type to another depending upon the original sediment fabric, the mechanism by which dolomite was formed, and the extent to which early formed dolomite was modified by post-dolomitization diagenetic processes (e.g., karstification, fracturing, and burial corrosion). This paper discusses the origin of dolomite porosity and demonstrates the porosity evolution and reservoir characteristics of different dolomite types.
Hybrid Discrete-Continuous Markov Decision Processes
NASA Technical Reports Server (NTRS)
Feng, Zhengzhu; Dearden, Richard; Meuleau, Nicholas; Washington, Rich
2003-01-01
This paper proposes a Markov decision process (MDP) model that features both discrete and continuous state variables. We extend previous work by Boyan and Littman on the mono-dimensional time-dependent MDP to multiple dimensions. We present the principle of lazy discretization, and piecewise constant and linear approximations of the model. Having to deal with several continuous dimensions raises several new problems that require new solutions. In the (piecewise) linear case, we use techniques from partially- observable MDPs (POMDPS) to represent value functions as sets of linear functions attached to different partitions of the state space.
NASA Astrophysics Data System (ADS)
Klette, Reinhard; Jiang, Ruyi; Morales, Sandino; Vaudrey, Tobi
Applying computer technology, such as computer vision in driver assistance, implies that processes and data are modeled as being discretized rather than being continuous. The area of stereo vision provides various examples how concepts known in discrete mathematics (e.g., pixel adjacency graphs, belief propagation, dynamic programming, max-flow/min-cut, or digital straight lines) are applied when aiming for efficient and accurate pixel correspondence solutions. The paper reviews such developments for a reader in discrete mathematics who is interested in applied research (in particular, in vision-based driver assistance). As a second subject, the paper also discusses lane detection and tracking, which is a particular task in driver assistance; recently the Euclidean distance transform proved to be a very appropriate tool for obtaining a fairly robust solution.
Discrete breathers in crystals
NASA Astrophysics Data System (ADS)
Dmitriev, S. V.; Korznikova, E. A.; Baimova, Yu A.; Velarde, M. G.
2016-05-01
It is well known that periodic discrete defect-containing systems, in addition to traveling waves, support vibrational defect-localized modes. It turned out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Since the nodes of the system are all on equal footing, it is only through the special choice of initial conditions that a group of nodes can be found on which such a mode, called a discrete breather (DB), will be excited. The DB frequency must be outside the frequency range of the small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically conserve its vibrational energy forever provided no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery in them of DBs was only a matter of time. It is well known that periodic discrete defect-containing systems support both traveling waves and vibrational defect-localized modes. It turns out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Because the nodes of the system are all on equal footing, only a special choice of the initial conditions allows selecting a group of nodes on which such a mode, called a discrete breather (DB), can be excited. The DB frequency must be outside the frequency range of small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically preserve its vibrational energy forever if no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery of DBs in them was only a matter of time. Experimental studies of DBs encounter major technical difficulties, leaving atomistic computer simulations as the primary investigation tool. Despite
Double-discrete solitons in fishnet arrays of optical fibers.
Staliunas, Kestutis; Malomed, Boris
2013-08-01
We demonstrate that crossed arrays of optical fibers support the double-discrete linear and nonlinear propagation of light beams, in which not only the transverse coordinate (the fiber's number) is discrete, but also the longitudinal (propagation) coordinate, i.e., the number of the fiber-crossing site, is effectively discrete too. In the linear limit, this transmission regime features double-discrete self-collimation. The nonlinear fishnet arrays with both focusing and defocusing nonlinearities give rise to double-discrete spatial solitons. Solitons bifurcating from two different branches of the linear dispersion relation feature strong interactions and form composite states. In the continuum limit, the model of the nonlinear fishnet reduces to a system of coupled-mode equations similar to those describing Bragg gratings, but without the cross-phase-modulation terms.
Natural discretization in noncommutative field theory
NASA Astrophysics Data System (ADS)
Acatrinei, Ciprian Sorin
2015-12-01
A discretization scheme for field theory is developed, in which the space time coordinates are assumed to be operators forming a noncommutative algebra. Generic waves without rotational symmetry are studied in (2+1) - dimensional scalar field theory with Heisenberg-type noncommutativity. In the representation chosen, the radial coordinate is naturally rendered discrete. Nonlocality along this coordinate, induced by noncommutativity, accounts for the angular dependence of the fields. A complete solution and the interpretation of its nonlocal features are given. The exact form of standing and propagating waves on such a discrete space is found in terms of finite series. A precise correspondence is established between the degree of nonlocality and the angular momentum of a field configuration. At small distance no classical singularities appear, even at the location of the sources. At large radius one recovers the usual commutative/continuum behaviour.
Natural discretization in noncommutative field theory
Acatrinei, Ciprian Sorin
2015-12-07
A discretization scheme for field theory is developed, in which the space time coordinates are assumed to be operators forming a noncommutative algebra. Generic waves without rotational symmetry are studied in (2+1) - dimensional scalar field theory with Heisenberg-type noncommutativity. In the representation chosen, the radial coordinate is naturally rendered discrete. Nonlocality along this coordinate, induced by noncommutativity, accounts for the angular dependence of the fields. A complete solution and the interpretation of its nonlocal features are given. The exact form of standing and propagating waves on such a discrete space is found in terms of finite series. A precise correspondence is established between the degree of nonlocality and the angular momentum of a field configuration. At small distance no classical singularities appear, even at the location of the sources. At large radius one recovers the usual commutative/continuum behaviour.
Discrete Time Crystals: Rigidity, Criticality, and Realizations.
Yao, N Y; Potter, A C; Potirniche, I-D; Vishwanath, A
2017-01-20
Despite being forbidden in equilibrium, spontaneous breaking of time translation symmetry can occur in periodically driven, Floquet systems with discrete time-translation symmetry. The period of the resulting discrete time crystal is quantized to an integer multiple of the drive period, arising from a combination of collective synchronization and many body localization. Here, we consider a simple model for a one-dimensional discrete time crystal which explicitly reveals the rigidity of the emergent oscillations as the drive is varied. We numerically map out its phase diagram and compute the properties of the dynamical phase transition where the time crystal melts into a trivial Floquet insulator. Moreover, we demonstrate that the model can be realized with current experimental technologies and propose a blueprint based upon a one dimensional chain of trapped ions. Using experimental parameters (featuring long-range interactions), we identify the phase boundaries of the ion-time-crystal and propose a measurable signature of the symmetry breaking phase transition.
Discrete Time Crystals: Rigidity, Criticality, and Realizations
NASA Astrophysics Data System (ADS)
Yao, N. Y.; Potter, A. C.; Potirniche, I.-D.; Vishwanath, A.
2017-01-01
Despite being forbidden in equilibrium, spontaneous breaking of time translation symmetry can occur in periodically driven, Floquet systems with discrete time-translation symmetry. The period of the resulting discrete time crystal is quantized to an integer multiple of the drive period, arising from a combination of collective synchronization and many body localization. Here, we consider a simple model for a one-dimensional discrete time crystal which explicitly reveals the rigidity of the emergent oscillations as the drive is varied. We numerically map out its phase diagram and compute the properties of the dynamical phase transition where the time crystal melts into a trivial Floquet insulator. Moreover, we demonstrate that the model can be realized with current experimental technologies and propose a blueprint based upon a one dimensional chain of trapped ions. Using experimental parameters (featuring long-range interactions), we identify the phase boundaries of the ion-time-crystal and propose a measurable signature of the symmetry breaking phase transition.
Quantum cosmology based on discrete Feynman paths
Chew, Geoffrey F.
2002-10-10
Although the rules for interpreting local quantum theory imply discretization of process, Lorentz covariance is usually regarded as precluding time quantization. Nevertheless a time-discretized quantum representation of redshifting spatially-homogeneous universe may be based on discrete-step Feynman paths carrying causal Lorentz-invariant action--paths that not only propagate the wave function but provide a phenomenologically-promising elementary-particle Hilbert-space basis. In a model under development, local path steps are at Planck scale while, at a much larger ''wave-function scale'', global steps separate successive wave-functions. Wave-function spacetime is but a tiny fraction of path spacetime. Electromagnetic and gravitational actions are ''at a distance'' in Wheeler-Feynman sense while strong (color) and weak (isospin) actions, as well as action of particle motion, are ''local'' in a sense paralleling the action of local field theory. ''Nonmaterial'' path segments and ''trivial events'' collaborate to define energy and gravity. Photons coupled to conserved electric charge enjoy privileged model status among elementary fermions and vector bosons. Although real path parameters provide no immediate meaning for ''measurement'', the phase of the complex wave function allows significance for ''information'' accumulated through ''gentle'' electromagnetic events involving charged matter and ''soft'' photons. Through its soft-photon content the wave function is an ''information reservoir''.
Makris, Konstantinos G; Suntsov, Sergiy; Christodoulides, Demetrios N; Stegeman, George I; Hache, Alain
2005-09-15
It is theoretically shown that discrete nonlinear surface waves are possible in waveguide lattices. These self-trapped states are located at the edge of the array and can exist only above a certain power threshold. The excitation characteristics and stability properties of these surface waves are systematically investigated.
Structure of random discrete spacetime
NASA Technical Reports Server (NTRS)
Brightwell, Graham; Gregory, Ruth
1991-01-01
The usual picture of spacetime consists of a continuous manifold, together with a metric of Lorentzian signature which imposes a causal structure on the spacetime. A model, first suggested by Bombelli et al., is considered in which spacetime consists of a discrete set of points taken at random from a manifold, with only the causal structure on this set remaining. This structure constitutes a partially ordered set (or poset). Working from the poset alone, it is shown how to construct a metric on the space which closely approximates the metric on the original spacetime manifold, how to define the effective dimension of the spacetime, and how such quantities may depend on the scale of measurement. Possible desirable features of the model are discussed.
3D scientific visualization of reservoir simulation post-processing
Sousa, M.C.; Miranda-Filho, D.N.
1994-12-31
This paper describes a 3D visualization software designed at PETROBRAS and TecGraf/PUC-RJ in Brazil for the analysis of reservoir engineering post-processing data. It offers an advanced functional environment on graphical workstations with intuitive and ergonomic interface. Applications to real reservoir models show the enriching features of the software.
95. BOUQUET RESERVOIR LOOKING UP VALLEY TO RESERVOIR LOOKING EAST ...
95. BOUQUET RESERVOIR LOOKING UP VALLEY TO RESERVOIR LOOKING EAST - Los Angeles Aqueduct, From Lee Vining Intake (Mammoth Lakes) to Van Norman Reservoir Complex (San Fernando Valley), Los Angeles, Los Angeles County, CA
Skimming' a reservoir for trash
Shenman, L.E. )
1993-02-01
Several hydropower facilities are using a new technology for removing floating trash in reservoirs. Representatives from the facilities say the boat, called a trashskimmer, is efficient, easy to maneuver, and transportable. Designed by United Marine International, Inc., the pontoon boat features an operators cab that straddles an open hull between the skis of the pontoon, and uses dual propellers to maneuver through the water. The Marineskimmer allows the operator to approach the trash from the water side upstream of the plant. The Tennessee Valley Authority has used the boat since 1990.
Ponden, Raymond F.
1991-11-22
Inflation of the reservoir is to begin on Friday afternoon, November 22 and continue through mid day on Monday, November 25. Inflation of the reservoir shall be accomplished by using only injection pump, HP-2. NOTE: Under no circumstances should injection pump, HP-1 be operated.
Geothermal reservoir engineering research
NASA Technical Reports Server (NTRS)
Ramey, H. J., Jr.; Kruger, P.; Brigham, W. E.; London, A. L.
1974-01-01
The Stanford University research program on the study of stimulation and reservoir engineering of geothermal resources commenced as an interdisciplinary program in September, 1972. The broad objectives of this program have been: (1) the development of experimental and computational data to evaluate the optimum performance of fracture-stimulated geothermal reservoirs; (2) the development of a geothermal reservoir model to evaluate important thermophysical, hydrodynamic, and chemical parameters based on fluid-energy-volume balances as part of standard reservoir engineering practice; and (3) the construction of a laboratory model of an explosion-produced chimney to obtain experimental data on the processes of in-place boiling, moving flash fronts, and two-phase flow in porous and fractured hydrothermal reservoirs.
Discrete Variational Optimal Control
NASA Astrophysics Data System (ADS)
Jiménez, Fernando; Kobilarov, Marin; Martín de Diego, David
2013-06-01
This paper develops numerical methods for optimal control of mechanical systems in the Lagrangian setting. It extends the theory of discrete mechanics to enable the solutions of optimal control problems through the discretization of variational principles. The key point is to solve the optimal control problem as a variational integrator of a specially constructed higher dimensional system. The developed framework applies to systems on tangent bundles, Lie groups, and underactuated and nonholonomic systems with symmetries, and can approximate either smooth or discontinuous control inputs. The resulting methods inherit the preservation properties of variational integrators and result in numerically robust and easily implementable algorithms. Several theoretical examples and a practical one, the control of an underwater vehicle, illustrate the application of the proposed approach.
Steerable Discrete Fourier Transform
NASA Astrophysics Data System (ADS)
Fracastoro, Giulia; Magli, Enrico
2017-03-01
Directional transforms have recently raised a lot of interest thanks to their numerous applications in signal compression and analysis. In this letter, we introduce a generalization of the discrete Fourier transform, called steerable DFT (SDFT). Since the DFT is used in numerous fields, it may be of interest in a wide range of applications. Moreover, we also show that the SDFT is highly related to other well-known transforms, such as the Fourier sine and cosine transforms and the Hilbert transforms.
The Discrete Wavelet Transform
1991-06-01
Split- Band Coding," Proc. ICASSP, May 1977, pp 191-195. 12. Vetterli, M. "A Theory of Multirate Filter Banks ," IEEE Trans. ASSP, 35, March 1987, pp 356...both special cases of a single filter bank structure, the discrete wavelet transform, the behavior of which is governed by one’s choice of filters . In...B-1 ,.iii FIGURES 1.1 A wavelet filter bank structure ..................................... 2 2.1 Diagram illustrating the dialation and
Discrete minimal flavor violation
Zwicky, Roman; Fischbacher, Thomas
2009-10-01
We investigate the consequences of replacing the global flavor symmetry of minimal flavor violation (MFV) SU(3){sub Q}xSU(3){sub U}xSU(3){sub D}x{center_dot}{center_dot}{center_dot} by a discrete D{sub Q}xD{sub U}xD{sub D}x{center_dot}{center_dot}{center_dot} symmetry. Goldstone bosons resulting from the breaking of the flavor symmetry generically lead to bounds on new flavor structure many orders of magnitude above the TeV scale. The absence of Goldstone bosons for discrete symmetries constitute the primary motivation of our work. Less symmetry implies further invariants and renders the mass-flavor basis transformation observable in principle and calls for a hierarchy in the Yukawa matrix expansion. We show, through the dimension of the representations, that the (discrete) symmetry in principle does allow for additional {delta}F=2 operators. If though the {delta}F=2 transitions are generated by two subsequent {delta}F=1 processes, as, for example, in the standard model, then the four crystal-like groups {sigma}(168){approx_equal}PSL(2,F{sub 7}), {sigma}(72{phi}), {sigma}(216{phi}) and especially {sigma}(360{phi}) do provide enough protection for a TeV-scale discrete MFV scenario. Models where this is not the case have to be investigated case by case. Interestingly {sigma}(216{phi}) has a (nonfaithful) representation corresponding to an A{sub 4} symmetry. Moreover we argue that the, apparently often omitted, (D) groups are subgroups of an appropriate {delta}(6g{sup 2}). We would like to stress that we do not provide an actual model that realizes the MFV scenario nor any other theory of flavor.
A paradigm for discrete physics
Noyes, H.P.; McGoveran, D.; Etter, T.; Manthey, M.J.; Gefwert, C.
1987-01-01
An example is outlined for constructing a discrete physics using as a starting point the insight from quantum physics that events are discrete, indivisible and non-local. Initial postulates are finiteness, discreteness, finite computability, absolute nonuniqueness (i.e., homogeneity in the absence of specific cause) and additivity.
Magma Reservoirs Feeding Giant Radiating Dike Swarms: Insights from Venus
NASA Technical Reports Server (NTRS)
Grosfils, E. B.; Ernst, R. E.
2003-01-01
Evidence of lateral dike propagation from shallow magma reservoirs is quite common on the terrestrial planets, and examination of the giant radiating dike swarm population on Venus continues to provide new insight into the way these complex magmatic systems form and evolve. For example, it is becoming clear that many swarms are an amalgamation of multiple discrete phases of dike intrusion. This is not surprising in and of itself, as on Earth there is clear evidence that formation of both magma reservoirs and individual giant radiating dikes often involves periodic magma injection. Similarly, giant radiating swarms on Earth can contain temporally discrete subswarms defined on the basis of geometry, crosscutting relationships, and geochemical or paleomagnetic signatures. The Venus data are important, however, because erosion, sedimentation, plate tectonic disruption, etc. on Earth have destroyed most giant radiating dike swarm's source regions, and thus we remain uncertain about the geometry and temporal evolution of the magma sources from which the dikes are fed. Are the reservoirs which feed the dikes large or small, and what are the implications for how the dikes themselves form? Does each subswarm originate from a single, periodically reactivated reservoir, or do subswarms emerge from multiple discrete geographic foci? If the latter, are these discrete foci located at the margins of a single large magma body, or do multiple smaller reservoirs define the character of the magmatic center as a whole? Similarly, does the locus of magmatic activity change with time, or are all the foci active simultaneously? Careful study of giant radiating dike swarms on Venus is yielding the data necessary to address these questions and constrain future modeling efforts. Here, using giant radiating dike swarms from the Nemesis Tessera (V14) and Carson (V43) quadrangles as examples, we illustrate some of the dike swarm focal region diversity observed on Venus and briefly explore some
NASA Astrophysics Data System (ADS)
Hassani, H.; Saadatinejad, M. R.
2012-04-01
Spectral decomposition provides better methods for quantifying and visualizing subtle seismic features and by decomposing the seismic signal into discrete frequency components, allows the geoscientist to analyze and map features. Through these methods, continuous wavelet transform (CWT) is an effective and widely-applied. It provides a different approach to time-frequency analysis and produces a time-scale map. The application of CWT is extensive and in this paper, we applied two major capacities of CWT in seismic investigations. It operated to detect reservoir structural characteristics and low-frequency shadows below gas reservoirs to develop a producing reservoir and discover a new petroleum reservoir in 2 oilfields in southwestern of Iran successfully. At the first and significant application in reservoir structure study, CWT enabled to providing clear images from kind of structural systems especially to identify hidden structural features such as extensional ruptures and faults for better drilling, injection and recovery operations and be able to increase production of oilfield. According to properties of tectonic events as fault and their effect (velocity diffraction) on seismic signals, it had been observed that CWT results show some discontinuities in location of ruptures and be able to display them more obvious than other spectral results, especially on horizon slices. Then, by picking and interpretation those, we obtain map, kind, strike and deep direction of faults easily. In petroleum exploration case, low-frequency shadows in CWT results appear due to energy attenuation of seismic signal in high frequencies by the presence of gas; this means there are no high frequencies under the gas reservoir. This phenomenon accounts as an indicator and attribute to explore reservoirs containing gas. As the frequency increases, these shadows decrease and finally disappear. The ranges of these shadows are usually between 8 to 20 Hz in gaz and 28 to 35 Hz in oil
Discretization of the Schwarzian derivative
NASA Astrophysics Data System (ADS)
Itoh, Toshiaki
2016-10-01
Numerical treatment of the Schwarzian derivatives from the exact discretization point is useful for many applications. Since we found the discrete counterpart of Schwarzian derivative is the Cross-ratio, we can regard the Cross-ratio to the discrete conformal mapping function instead of the Schwarzian derivative. By this approach we found some integrable system of special functions are derived by the classical treatment of 2nd order ODE and difference equations. Such discrete integrable system is composed of simultameous equation of the two Möbius transformations or discrete Riccati's eqautions.
Reservoir characterization of Pennsylvanian sandstone reservoirs. Final report
Kelkar, M.
1995-02-01
This final report summarizes the progress during the three years of a project on Reservoir Characterization of Pennsylvanian Sandstone Reservoirs. The report is divided into three sections: (i) reservoir description; (ii) scale-up procedures; (iii) outcrop investigation. The first section describes the methods by which a reservoir can be described in three dimensions. The next step in reservoir description is to scale up reservoir properties for flow simulation. The second section addresses the issue of scale-up of reservoir properties once the spatial descriptions of properties are created. The last section describes the investigation of an outcrop.
Three-phase flow simulations in discrete fracture networks
NASA Astrophysics Data System (ADS)
Geiger, S.; Niessner, J.; Matthai, S. K.; Helmig, R.
2006-12-01
Fractures are often the key conduits for fluid flow in otherwise low permeability rocks. Their presence in hydrocarbon reservoirs leads to complex production histories, unpredictable coupling of wells, rapidly changing flow rates, possibly early water breakthrough, and low final recovery. Recently, it has been demonstrated that a combination of finite volume and finite element discretization is well suited to model incompressible, immiscible two-phase flow in 3D discrete fracture networks (DFN) representing complexly fractured rocks. Such an approach has been commercialized in Golder Associates' FracMan Reservoir Edition software. For realistic reservoir simulations, however, it would be desirable if a third compressible gas phase can be included which is often present at reservoir conditions. Here we present the extension of an existing node-centred finite volume - finite element (FEFV) discretization for the efficient and accurate simulations of three-component - three-phase flow in geologically realistic representations of fractured porous media. Two possible types of fracture networks can be used: In 2D, they are detailed geometrical representations of fractured rock masses mapped in field studies. In 3D, they are geologically constrained, stochastically generated discrete fracture networks. Flow and transport can be simulated for fractures only or for fractures and matrix combined. The governing equations are solved decoupled using an implicit-pressure, explicit-saturation (IMPES) approach. Flux and concentration terms can be treated with higher-order accuracy in the finite volume scheme to preserve shock fronts. The method is locally mass conservative and works on unstructured, spatially refined grids. Flash calculations are carried out by a new description of the Black-Oil model. Capillary and gravity effects are included in this formulation. The robustness and accuracy of this formulation is shown in several applications. First, grid convergence is
Bodvarsson, G.S.; Lippmann, M.J.; Pruess, K. )
1993-01-01
Lawrence Berkeley Laboratory is conducting several research projects related to issues of interest to The Geysers operators, including those that deal with understanding the nature of vapor-dominated systems, measuring or inferring reservoir processes and parameters, and studying the effects of liquid injection. All of these topics are directly or indirectly relevant to the development of reservoir strategies aimed at stabilizing or increasing production rates of non-corrosive steam, low in non-condensable gases. Three reservoir engineering studies are described in some detail, that is: (a) Modeling studies of heat transfer and phase distribution in two-phase geothermal reservoirs; (b) Numerical modeling studies of Geysers injection experiments; and (c) Development of a dual-porosity model to calculate mass flow between rock matrix blocks and neighboring fractures.
Potential Mammalian Filovirus Reservoirs
Carroll, Darin S.; Mills, James N.; Johnson, Karl M.
2004-01-01
Ebola and Marburg viruses are maintained in unknown reservoir species; spillover into human populations results in occasional human cases or epidemics. We attempted to narrow the list of possibilities regarding the identity of those reservoir species. We made a series of explicit assumptions about the reservoir: it is a mammal; it supports persistent, largely asymptomatic filovirus infections; its range subsumes that of its associated filovirus; it has coevolved with the virus; it is of small body size; and it is not a species that is commensal with humans. Under these assumptions, we developed priority lists of mammal clades that coincide distributionally with filovirus outbreak distributions and compared these lists with those mammal taxa that have been tested for filovirus infection in previous epidemiologic studies. Studying the remainder of these taxa may be a fruitful avenue for pursuing the identity of natural reservoirs of filoviruses. PMID:15663841
Geothermal reservoir simulation
NASA Technical Reports Server (NTRS)
Mercer, J. W., Jr.; Faust, C.; Pinder, G. F.
1974-01-01
The prediction of long-term geothermal reservoir performance and the environmental impact of exploiting this resource are two important problems associated with the utilization of geothermal energy for power production. Our research effort addresses these problems through numerical simulation. Computer codes based on the solution of partial-differential equations using finite-element techniques are being prepared to simulate multiphase energy transport, energy transport in fractured porous reservoirs, well bore phenomena, and subsidence.
Renner, Joel L.; Bodvarsson, Gudmundur S.; Wannamaker, Philip E.; Horne, Roland N.; Shook, G. Michael
1992-01-01
This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five papers: ''Reservoir Technology'' by Joel L. Renner; ''LBL Research on the Geysers: Conceptual Models, Simulation and Monitoring Studies'' by Gudmundur S. Bodvarsson; ''Geothermal Geophysical Research in Electrical Methods at UURI'' by Philip E. Wannamaker; ''Optimizing Reinjection Strategy at Palinpinon, Philippines Based on Chloride Data'' by Roland N. Horne; ''TETRAD Reservoir Simulation'' by G. Michael Shook
Davies, D.K.; Vessell, R.K.; Doublet, L.E.
1997-08-01
An integrated geological/petrophysical and reservoir engineering study was performed for a large, mature waterflood project (>250 wells, {approximately}80% water cut) at the North Robertson (Clear Fork) Unit, Gaines County, Texas. The primary goal of the study was to develop an integrated reservoir description for {open_quotes}targeted{close_quotes} (economic) 10-acre (4-hectare) infill drilling and future recovery operations in a low permeability, carbonate (dolomite) reservoir. Integration of the results from geological/petrophysical studies and reservoir performance analyses provide a rapid and effective method for developing a comprehensive reservoir description. This reservoir description can be used for reservoir flow simulation, performance prediction, infill targeting, waterflood management, and for optimizing well developments (patterns, completions, and stimulations). The following analyses were performed as part of this study: (1) Geological/petrophysical analyses: (core and well log data) - {open_quotes}Rock typing{close_quotes} based on qualitative and quantitative visualization of pore-scale features. Reservoir layering based on {open_quotes}rock typing {close_quotes} and hydraulic flow units. Development of a {open_quotes}core-log{close_quotes} model to estimate permeability using porosity and other properties derived from well logs. The core-log model is based on {open_quotes}rock types.{close_quotes} (2) Engineering analyses: (production and injection history, well tests) Material balance decline type curve analyses to estimate total reservoir volume, formation flow characteristics (flow capacity, skin factor, and fracture half-length), and indications of well/boundary interference. Estimated ultimate recovery analyses to yield movable oil (or injectable water) volumes, as well as indications of well and boundary interference.
Andrew integrated reservoir description
Todd, S.P.
1996-12-31
The Andrew field is an oil and gas accumulation in Palaeocene deep marine sands in the Central North Sea. It is currently being developed with mainly horizontal oil producers. Because of the field`s relatively small reserves (mean 118 mmbbls), the performance of each of the 10 or so horizontal wells is highly important. Reservoir description work at sanction time concentrated on supporting the case that the field could be developed commercially with the minimum number of wells. The present Integrated Reservoir Description (IRD) is focussed on delivering the next level of detail that will impact the understanding of the local reservoir architecture and dynamic performance of each well. Highlights of Andrew IRD Include: (1) Use of a Reservoir Uncertainty Statement (RUS) developed at sanction time to focus the descriptive effort of both asset, support and contract petrotechnical staff, (2) High resolution biostratigraphic correlation to support confident zonation of the reservoir, (3) Detailed sedimentological analysis of the core including the use of dipmeter to interpret channel/sheet architecture to provide new insights into reservoir heterogeneity; (4) Integrated petrographical and petrophysical investigation of the controls on Sw-Height and relative permeability of water; (5) Fluids description using oil geochemistry and Residual Salt Analysis Sr isotope studies. Andrew IRD has highlighted several important risks to well performance, including the influence of more heterolithic intervals on gas breakthrough and the controls on water coning exerted by suppressed water relative permeability in the transition zone.
Andrew integrated reservoir description
Todd, S.P.
1996-01-01
The Andrew field is an oil and gas accumulation in Palaeocene deep marine sands in the Central North Sea. It is currently being developed with mainly horizontal oil producers. Because of the field's relatively small reserves (mean 118 mmbbls), the performance of each of the 10 or so horizontal wells is highly important. Reservoir description work at sanction time concentrated on supporting the case that the field could be developed commercially with the minimum number of wells. The present Integrated Reservoir Description (IRD) is focussed on delivering the next level of detail that will impact the understanding of the local reservoir architecture and dynamic performance of each well. Highlights of Andrew IRD Include: (1) Use of a Reservoir Uncertainty Statement (RUS) developed at sanction time to focus the descriptive effort of both asset, support and contract petrotechnical staff, (2) High resolution biostratigraphic correlation to support confident zonation of the reservoir, (3) Detailed sedimentological analysis of the core including the use of dipmeter to interpret channel/sheet architecture to provide new insights into reservoir heterogeneity; (4) Integrated petrographical and petrophysical investigation of the controls on Sw-Height and relative permeability of water; (5) Fluids description using oil geochemistry and Residual Salt Analysis Sr isotope studies. Andrew IRD has highlighted several important risks to well performance, including the influence of more heterolithic intervals on gas breakthrough and the controls on water coning exerted by suppressed water relative permeability in the transition zone.
Discrete control of resonant wave energy devices.
Clément, A H; Babarit, A
2012-01-28
Aiming at amplifying the energy productive motion of wave energy converters (WECs) in response to irregular sea waves, the strategies of discrete control presented here feature some major advantages over continuous control, which is known to require, for optimal operation, a bidirectional power take-off able to re-inject energy into the WEC system during parts of the oscillation cycles. Three different discrete control strategies are described: latching control, declutching control and the combination of both, which we term latched-operating-declutched control. It is shown that any of these methods can be applied with great benefit, not only to mono-resonant WEC oscillators, but also to bi-resonant and multi-resonant systems. For some of these applications, it is shown how these three discrete control strategies can be optimally defined, either by analytical solution for regular waves, or numerically, by applying the optimal command theory in irregular waves. Applied to a model of a seven degree-of-freedom system (the SEAREV WEC) to estimate its annual production on several production sites, the most efficient of these discrete control strategies was shown to double the energy production, regardless of the resource level of the site, which may be considered as a real breakthrough, rather than a marginal improvement.
Geometry of Discrete-Time Spin Systems
NASA Astrophysics Data System (ADS)
McLachlan, Robert I.; Modin, Klas; Verdier, Olivier
2016-10-01
Classical Hamiltonian spin systems are continuous dynamical systems on the symplectic phase space (S^2)^n. In this paper, we investigate the underlying geometry of a time discretization scheme for classical Hamiltonian spin systems called the spherical midpoint method. As it turns out, this method displays a range of interesting geometrical features that yield insights and sets out general strategies for geometric time discretizations of Hamiltonian systems on non-canonical symplectic manifolds. In particular, our study provides two new, completely geometric proofs that the discrete-time spin systems obtained by the spherical midpoint method preserve symplecticity. The study follows two paths. First, we introduce an extended version of the Hopf fibration to show that the spherical midpoint method can be seen as originating from the classical midpoint method on T^*{R}^{2n} for a collective Hamiltonian. Symplecticity is then a direct, geometric consequence. Second, we propose a new discretization scheme on Riemannian manifolds called the Riemannian midpoint method. We determine its properties with respect to isometries and Riemannian submersions, and, as a special case, we show that the spherical midpoint method is of this type for a non-Euclidean metric. In combination with Kähler geometry, this provides another geometric proof of symplecticity.
Reservoir characterization and enhanced oil recovery research
Lake, L.W.; Pope, G.A.; Schechter, R.S.
1992-03-01
The research in this annual report falls into three tasks each dealing with a different aspect of enhanced oil recovery. The first task strives to develop procedures for accurately modeling reservoirs for use as input to numerical simulation flow models. This action describes how we have used a detail characterization of an outcrop to provide insights into what features are important to fluid flow modeling. The second task deals with scaling-up and modeling chemical and solvent EOR processes. In a sense this task is the natural extension of task 1 and, in fact, one of the subtasks uses many of the same statistical procedures for insight into the effects of viscous fingering and heterogeneity. The final task involves surfactants and their interactions with carbon dioxide and reservoir minerals. This research deals primarily with phenomena observed when aqueous surfactant solutions are injected into oil reservoirs.
A Discrete Lagrangian Algorithm for Optimal Routing Problems
Kosmas, O. T.; Vlachos, D. S.; Simos, T. E.
2008-11-06
The ideas of discrete Lagrangian methods for conservative systems are exploited for the construction of algorithms applicable in optimal ship routing problems. The algorithm presented here is based on the discretisation of Hamilton's principle of stationary action Lagrangian and specifically on the direct discretization of the Lagrange-Hamilton principle for a conservative system. Since, in contrast to the differential equations, the discrete Euler-Lagrange equations serve as constrains for the optimization of a given cost functional, in the present work we utilize this feature in order to minimize the cost function for optimal ship routing.
A dual-porosity reservoir model with a nonlinear coupling term
Zimmerman, R.W.; Chen, G.; Hadgu, T.; Bodvarsson, G.S.
1992-09-01
Since their introduction by Barenblatt et al. (1960), double-porosity models have been widely used for simulating flow in fractured reservoirs, such as geothermal reservoirs. In a dual-porosity system, the matrix blocks provide most of the storage of the reservoir, whereas the fractures provide the global transmissivity. Initially, most work on dual-porosity models emphasized the development of analytical solutions to idealized reservoir problems. Increasingly, the dual-porosity approach is being implemented by numerical reservoir simulators. Accurate numerical simulation of a dual-porosity problem often requires a prohibitively large number of computational cells in order to resolve the transient pressure gradients in the matrix blocks. We discuss a new dual-porosity model that utilizes a nonlinear differential equation to approximate the fracture/matrix interactions, When implemented into a numerical simulator, it eliminates the need to discretize the matrix blocks, and thereby allows more efficient simulation of reservoir problems.
Hot Dry Rock Geothermal Reservoir Model Development at Los Alamos
Robinson, Bruce A.; Birdsell, Stephen A.
1989-03-21
Discrete fracture and continuum models are being developed to simulate Hot Dry Rock (HDR) geothermal reservoirs. The discrete fracture model is a two-dimensional steady state simulator of fluid flow and tracer transport in a fracture network which is generated from assumed statistical properties of the fractures. The model's strength lies in its ability to compute the steady state pressure drop and tracer response in a realistic network of interconnected fractures. The continuum approach models fracture behavior by treating permeability and porosity as functions of temperature and effective stress. With this model it is practical to model transient behavior as well as the coupled processes of fluid flow, heat transfer, and stress effects in a three-dimensional system. The model capabilities being developed will also have applications in conventional geothermal systems undergoing reinjection and in fractured geothermal reservoirs in general.
Hot Dry Rock geothermal reservoir model development at Los Alamos
Robinson, B.A.; Birdsell, S.A.
1989-01-01
Discrete fracture and continuum models are being developed to simulate Hot Dry Rock (HDR) geothermal reservoirs. The discrete fracture model is a two-dimensional steady state simulator of fluid flow and tracer transport in a fracture network which is generated from assumed statistical properties of the fractures. The model's strength lies in its ability to compute the steady state pressure drop and tracer response in a realistic network of interconnected fractures. The continuum approach models fracture behavior by treating permeability and porosity as functions of temperature and effective stress. With this model it is practical to model transient behavior as well as the coupled processes of fluid flow, heat transfer, and stress effects in a three-dimensional system. The model capabilities being developed will also have applications in conventional geothermal systems undergoing reinjection and in fractured geothermal reservoirs in general. 15 refs., 7 figs.
Manpower Analysis Using Discrete Simulation
2015-12-01
building using Discrete Event Simulation (DES) and experimentation using Design of Experiments (DOE). We derived five metamodels to identify the most...objectives were met. 14. SUBJECT TERMS manpower policy analysis, discrete event simulation, Simkit 15. NUMBER OF PAGES 85 16. PRICE CODE 17. SECURITY...using Discrete Event Simulation (DES) and experimentation using Design of Experiments (DOE). We derived five metamodels to identify the most
Optimal Discretization Resolution in Algebraic Image Reconstruction
NASA Astrophysics Data System (ADS)
Sharif, Behzad; Kamalabadi, Farzad
2005-11-01
In this paper, we focus on data-limited tomographic imaging problems where the underlying linear inverse problem is ill-posed. A typical regularized reconstruction algorithm uses algebraic formulation with a predetermined discretization resolution. If the selected resolution is too low, we may loose useful details of the underlying image and if it is too high, the reconstruction will be unstable and the representation will fit irrelevant features. In this work, two approaches are introduced to address this issue. The first approach is using Mallow's CL method or generalized cross-validation. For each of the two methods, a joint estimator of regularization parameter and discretization resolution is proposed and their asymptotic optimality is investigated. The second approach is a Bayesian estimator of the model order using a complexity-penalizing prior. Numerical experiments focus on a space imaging application from a set of limited-angle tomographic observations.
Thermodynamics of discrete quantum processes
NASA Astrophysics Data System (ADS)
Anders, Janet; Giovannetti, Vittorio
2013-03-01
We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency.
Discrete Pearson distributions
Bowman, K.O.; Shenton, L.R.; Kastenbaum, M.A.
1991-11-01
These distributions are generated by a first order recursive scheme which equates the ratio of successive probabilities to the ratio of two corresponding quadratics. The use of a linearized form of this model will produce equations in the unknowns matched by an appropriate set of moments (assumed to exist). Given the moments we may find valid solutions. These are two cases; (1) distributions defined on the non-negative integers (finite or infinite) and (2) distributions defined on negative integers as well. For (1), given the first four moments, it is possible to set this up as equations of finite or infinite degree in the probability of a zero occurrence, the sth component being a product of s ratios of linear forms in this probability in general. For (2) the equation for the zero probability is purely linear but may involve slowly converging series; here a particular case is the discrete normal. Regions of validity are being studied. 11 refs.
Discrete Reliability Projection
2014-12-01
Defense, Handbook MIL - HDBK -189C, 2011 Hall, J. B., Methodology for Evaluating Reliability Growth Programs of Discrete Systems, Ph.D. thesis, University...pk,i ] · [ 1− (1− θ̆k) · ( N k · T )]k−m , (2.13) 5 2 Hall’s Model where m is the number of observed failure modes and d∗i estimates di (either based...Mode Failures FEF Ni d ∗ i 1 1 0.95 2 1 0.70 3 1 0.90 4 1 0.90 5 4 0.95 6 2 0.70 7 1 0.80 Using equations 2.1 and 2.2 we can calculate the failure
Noyes, H.P. ); Starson, S. )
1991-03-01
Discrete physics, because it replaces time evolution generated by the energy operator with a global bit-string generator (program universe) and replaces fields'' with the relativistic Wheeler-Feynman action at a distance,'' allows the consistent formulation of the concept of signed gravitational charge for massive particles. The resulting prediction made by this version of the theory is that free anti-particles near the surface of the earth will fall'' up with the same acceleration that the corresponding particles fall down. So far as we can see, no current experimental information is in conflict with this prediction of our theory. The experiment crusis will be one of the anti-proton or anti-hydrogen experiments at CERN. Our prediction should be much easier to test than the small effects which those experiments are currently designed to detect or bound. 23 refs.
NASA Astrophysics Data System (ADS)
Noyes, H. Pierre; Starson, Scott
1991-03-01
Discrete physics, because it replaces time evolution generated by the energy operator with a global bit-string generator (program universe) and replaces fields with the relativistic Wheeler-Feynman action at a distance, allows the consistent formulation of the concept of signed gravitational charge for massive particles. The resulting prediction made by this version of the theory is that free anti-particles near the surface of the earth will fall up with the same acceleration that the corresponding particles fall down. So far as we can see, no current experimental information is in conflict with this prediction of our theory. The experiment crusis will be one of the anti-proton or anti-hydrogen experiments at CERN. Our prediction should be much easier to test than the small effects which those experiments are currently designed to detect or bound.
Immigration and Prosecutorial Discretion.
Apollonio, Dorie; Lochner, Todd; Heddens, Myriah
Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration.
Steerable Discrete Cosine Transform
NASA Astrophysics Data System (ADS)
Fracastoro, Giulia; Fosson, Sophie M.; Magli, Enrico
2017-01-01
In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.
Steerable Discrete Cosine Transform.
Fracastoro, Giulia; Fosson, Sophie M; Magli, Enrico
2017-01-01
In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely, a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.
Nonintegrable Schrodinger discrete breathers.
Gómez-Gardeñes, J; Floría, L M; Peyrard, M; Bishop, A R
2004-12-01
In an extensive numerical investigation of nonintegrable translational motion of discrete breathers in nonlinear Schrödinger lattices, we have used a regularized Newton algorithm to continue these solutions from the limit of the integrable Ablowitz-Ladik lattice. These solutions are shown to be a superposition of a localized moving core and an excited extended state (background) to which the localized moving pulse is spatially asymptotic. The background is a linear combination of small amplitude nonlinear resonant plane waves and it plays an essential role in the energy balance governing the translational motion of the localized core. Perturbative collective variable theory predictions are critically analyzed in the light of the numerical results.
Immigration and Prosecutorial Discretion
Apollonio, Dorie; Lochner, Todd; Heddens, Myriah
2015-01-01
Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration. PMID:26146530
Discrete Minimal Surface Algebras
NASA Astrophysics Data System (ADS)
Arnlind, Joakim; Hoppe, Jens
2010-05-01
We consider discrete minimal surface algebras (DMSA) as generalized noncommutative analogues of minimal surfaces in higher dimensional spheres. These algebras appear naturally in membrane theory, where sequences of their representations are used as a regularization. After showing that the defining relations of the algebra are consistent, and that one can compute a basis of the enveloping algebra, we give several explicit examples of DMSAs in terms of subsets of sln (any semi-simple Lie algebra providing a trivial example by itself). A special class of DMSAs are Yang-Mills algebras. The representation graph is introduced to study representations of DMSAs of dimension d ≤ 4, and properties of representations are related to properties of graphs. The representation graph of a tensor product is (generically) the Cartesian product of the corresponding graphs. We provide explicit examples of irreducible representations and, for coinciding eigenvalues, classify all the unitary representations of the corresponding algebras.
An upscaling procedure for fractured reservoirs with embedded grids
NASA Astrophysics Data System (ADS)
Fumagalli, Alessio; Pasquale, Luca; Zonca, Stefano; Micheletti, Stefano
2016-08-01
Upscaling of geological models for reservoir simulation is an active and important area of research. In particular, we are interested in reservoirs where the rock matrix exhibits an intricate network of fractures, which usually acts as a preferential path to the flow. Accounting for fractures' contribution in the simulation of a reservoir is of paramount importance. Here we have focused on obtaining effective parameters (e.g., transmissibility) on a 3-D computational grid on the reservoir scale, which account for the presence, at a finer spatial scale, of fractures and a network of fractures. We have essentially followed the idea illustrated in Karimi-Fard et al. (2006), yet this work has some notable aspects of innovation in the way the procedure has been implemented, and in its capability to consider rather general corner-point grids, like the ones normally used in reservoir simulations in the industry, and complex and realistic fracture networks, possibly not fully connected inside the coarse cells. In particular, novel contribution is the employment of an Embedded Discrete Fracture Model (EDFM) for computing fracture-fracture and matrix-fracture transmissibilities, with a remarkable gain in speedup. The output is in the form of transmissibility that, although obtained by considering single-phase flow, can be used for coarse-scale multiphase reservoir simulations, also via industrial software, such as Eclipse, Intersect, or GPRS. The results demonstrate the effectiveness and computational efficiency of the numerical procedure which is now ready for further testing and industrialization.
Optoelectronic Reservoir Computing
Paquot, Y.; Duport, F.; Smerieri, A.; Dambre, J.; Schrauwen, B.; Haelterman, M.; Massar, S.
2012-01-01
Reservoir computing is a recently introduced, highly efficient bio-inspired approach for processing time dependent data. The basic scheme of reservoir computing consists of a non linear recurrent dynamical system coupled to a single input layer and a single output layer. Within these constraints many implementations are possible. Here we report an optoelectronic implementation of reservoir computing based on a recently proposed architecture consisting of a single non linear node and a delay line. Our implementation is sufficiently fast for real time information processing. We illustrate its performance on tasks of practical importance such as nonlinear channel equalization and speech recognition, and obtain results comparable to state of the art digital implementations. PMID:22371825
Discrete Fluctuations in Memory Erasure without Energy Cost.
Croucher, Toshio; Bedkihal, Salil; Vaccaro, Joan A
2017-02-10
According to Landauer's principle, erasing one bit of information incurs a minimum energy cost. Recently, Vaccaro and Barnett (VB) explored information erasure within the context of generalized Gibbs ensembles and demonstrated that for energy-degenerate spin reservoirs the cost of erasure can be solely in terms of a minimum amount of spin angular momentum and no energy. As opposed to the Landauer case, the cost of erasure in this case is associated with an intrinsically discrete degree of freedom. Here we study the discrete fluctuations in this cost and the probability of violation of the VB bound. We also obtain a Jarzynski-like equality for the VB erasure protocol. We find that the fluctuations below the VB bound are exponentially suppressed at a far greater rate and more tightly than for an equivalent Jarzynski expression for VB erasure. We expose a trade-off between the size of the fluctuations and the cost of erasure. We find that the discrete nature of the fluctuations is pronounced in the regime where reservoir spins are maximally polarized. We also state the first laws of thermodynamics corresponding to the conservation of spin angular momentum for this particular erasure protocol. Our work will be important for novel heat engines based on information erasure schemes that do not incur an energy cost.
Discrete Fluctuations in Memory Erasure without Energy Cost
NASA Astrophysics Data System (ADS)
Croucher, Toshio; Bedkihal, Salil; Vaccaro, Joan A.
2017-02-01
According to Landauer's principle, erasing one bit of information incurs a minimum energy cost. Recently, Vaccaro and Barnett (VB) explored information erasure within the context of generalized Gibbs ensembles and demonstrated that for energy-degenerate spin reservoirs the cost of erasure can be solely in terms of a minimum amount of spin angular momentum and no energy. As opposed to the Landauer case, the cost of erasure in this case is associated with an intrinsically discrete degree of freedom. Here we study the discrete fluctuations in this cost and the probability of violation of the VB bound. We also obtain a Jarzynski-like equality for the VB erasure protocol. We find that the fluctuations below the VB bound are exponentially suppressed at a far greater rate and more tightly than for an equivalent Jarzynski expression for VB erasure. We expose a trade-off between the size of the fluctuations and the cost of erasure. We find that the discrete nature of the fluctuations is pronounced in the regime where reservoir spins are maximally polarized. We also state the first laws of thermodynamics corresponding to the conservation of spin angular momentum for this particular erasure protocol. Our work will be important for novel heat engines based on information erasure schemes that do not incur an energy cost.
Reservoir-Based Drug Delivery Systems Utilizing Microtechnology
Stevenson, Cynthia L.; Santini, John T.; Langer, Robert
2012-01-01
This review covers reservoir-based drug delivery systems that incorporate microtechnology, with an emphasis on oral, dermal, and implantable systems. Key features of each technology are highlighted such as working principles, fabrication methods, dimensional constraints, and performance criteria. Reservoir-based systems include a subset of microfabricated drug delivery systems and provide unique advantages. Reservoirs, whether external to the body or implanted, provide a well-controlled environment for a drug formulation, allowing increased drug stability and prolonged delivery times. Reservoir systems have the flexibility to accommodate various delivery schemes, including zero order, pulsatile, and on demand dosing, as opposed to a standard sustained release profile. Furthermore, the development of reservoir-based systems for targeted delivery for difficult to treat applications (e.g., ocular) has resulted in potential platforms for patient therapy. PMID:22465783
Manicouagin Reservoir of Canada
NASA Technical Reports Server (NTRS)
2002-01-01
Recorded by the Space Shuttle Atlantis STS-110 mission, this is a photograph of the ice- covered Manicouagin Reservoir located in the Canadian Shield of Quebec Province in Eastern Canada, partially obscured by low clouds. This reservoir marks the site of an impact crater, 60 miles (100 kilometers) wide, which according to geologists was formed 212 million years ago when a meteorite crashed into this area. Over millions of years, the crater has been worn down by glaciers and other erosional processes. The Space Shuttle Orbiter Atlantis, STS-110 mission, was launched April 8, 2002 and returned to Earth April 19, 2002.
Hybrid-CVFE method for flexible-grid reservoir simulation
Fung, L.S.K.; Buchanan, L.; Sharma, R. )
1994-08-01
Well flows and pressures are the most important boundary conditions in reservoir simulation. In a typical simulation, rapid changes and large pressure, temperature, saturation, and composition gradients occur in near-well regions. Treatment of these near-well phenomena significantly affects the accuracy of reservoir simulation results; therefore, extensive efforts have been devoted to the numerical treatment of wells and near-well flows. The flexible control-volume finite-element (CVFE) method is used to construct hybrid grids. The method involves use of a local cylindrical or elliptical grid to represent near-well flow accurately while honoring complex reservoir boundaries. The grid transition is smooth without any special discretization approximation, which eliminates the grid transition problem experienced with Cartesian local grid refinement and hybrid Cartesian gridding techniques.
Assessing contribution of DOC from sediments to a drinking-water reservoir using optical profiling
Downing, Bryan D.; Bergamaschi, Brian A.; Evans, David G.; Boss, Emmanuel
2008-01-01
Understanding the sources of dissolved organic carbon (DOC) in drinking-water reservoirs is an important management issue because DOC may form disinfection by-products, interfere with disinfection, or increase treatment costs. DOC may be derived from a host of sources-algal production of DOC in the reservoir, marginal production of DOC from mucks and vascular plants at the margins, and sediments in the reservoir. The purpose of this study was to assess if release of DOC from reservoir sediments containing ferric chloride coagulant was a significant source of DOC to the reservoir. We examined the source-specific contributions of DOC using a profiling system to measure the in situ distribution of optical properties of absorption and fluorescence at various locations in the reservoir. Vertical optical profiles were coupled with discrete water samples measured in the laboratory for DOC concentration and optical properties: absorption spectra and excitation emission matrix spectra (EEMs). Modeling the in situ optical data permitted estimation of the bulk DOC profile in the reservoir as well as separation into source-specific contributions. Analysis of the source-specific profiles and their associated optical characteristics indicated that the sedimentary source of DOC to the reservoir is significant and that this DOC is labile in the reservoir. We conclude that optical profiling is a useful technique for understanding complex biogeochemical processes in a reservoir.
Naturally fractured tight gas reservoir detection optimization
Decker, D.
1995-05-01
Exploration strategies are needed to identify subtle basement features critical to locating fractured regions in advance of drilling in tight gas reservoirs. The Piceance Basin served as a demonstration site for an analysis utilizing aeromagnetic surveys, remote sensing, Landsat Thematic Mapper, and Side Looking Airborne Radar imagery for the basin and surrounding areas. Spatially detailed aeromagnetic maps were used to to interpret zones of basement structure.
Discrete Mathematics and Its Applications
ERIC Educational Resources Information Center
Oxley, Alan
2010-01-01
The article gives ideas that lecturers of undergraduate Discrete Mathematics courses can use in order to make the subject more interesting for students and encourage them to undertake further studies in the subject. It is possible to teach Discrete Mathematics with little or no reference to computing. However, students are more likely to be…
La Pointe, Paul R.; Hermanson, Jan
2002-09-09
The goal of this project is to improve the recovery of oil from the Circle Ridge Oilfield, located on the Wind River Reservation in Wyoming, through an innovative integration of matrix characterization, structural reconstruction, and the characterization of the fracturing in the reservoir through the use of discrete fracture network models.
Doherty, T.J.
1981-07-01
The objective of the reservoir stability studies project is to develop stability criteria for large underground reservoirs in salt domes, hard rock caverns, and porous rock structures for air storage in utility applications. Because reservoir stability was deemed crucial to commercialization of compressed air energy storage (CAES) systems this project has received major emphasis in the early phases of the overall CAES program. A long term plan, including state-of-the-art assessment, numerical model development and experimental studies culminating in field research, as necessary, was formulated. This plan, initiated in 1977, has been completed during FY-1981 to the stage of specific experimental studies and field research. Activities within this project during FY-1981 have included completion of site specific geotechnical design evaluations using methodologies developed to assess hard rock cavern stability, implementation of in-mine research to evaluate numerical and laboratory study conclusions on the response of domal salt, and preparation of integrated laboratory and field study facilities to assess developed predictive methods and determine in situ response of a porous media reservoir to air injection. The major activity in the project has been the field study component of the porous media studies. Accomplishments there have included completion of exploration, permitting and leasing, operation contractor selection and negotiation, and initiation of procurement and construction for an FY-1982 test initiation. A major program milestone, drilling of the injection withdrawal well for this test, was completed ahead of schedule.
Applying reservoir characterization technology
Lake, L.W.
1994-12-31
While reservoir characterization is an old discipline, only within the last 10 years have engineers and scientists been able to make quantitative descriptions, due mostly to improvements in high-resolution computational power, sophisticated graphics, and geostatistics. This paper summarizes what has been learned during the past decade by using these technologies.
Reinjection into geothermal reservoirs
Bodvarsson, G.S.; Stefansson, V.
1987-08-01
Reinjection of geothermal wastewater is practiced as a means of disposal and for reservoir pressure support. Various aspects of reinjection are discussed, both in terms of theoretical studies as well as specific field examples. The discussion focuses on the major effects of reinjection, including pressure maintenance and chemical and thermal effects. (ACR)
Discreteness inducing coexistence
NASA Astrophysics Data System (ADS)
dos Santos, Renato Vieira
2013-12-01
Consider two species that diffuse through space. Consider further that they differ only in initial densities and, possibly, in diffusion constants. Otherwise they are identical. What happens if they compete with each other in the same environment? What is the influence of the discrete nature of the interactions on the final destination? And what are the influence of diffusion and additive fluctuations corresponding to random migration and immigration of individuals? This paper aims to answer these questions for a particular competition model that incorporates intra and interspecific competition between the species. Based on mean field theory, the model has a stationary state dependent on the initial density conditions. We investigate how this initial density dependence is affected by the presence of demographic multiplicative noise and additive noise in space and time. There are three main conclusions: (1) Additive noise favors denser populations at the expense of the less dense, ratifying the competitive exclusion principle. (2) Demographic noise, on the other hand, favors less dense populations at the expense of the denser ones, inducing equal densities at the quasi-stationary state, violating the aforementioned principle. (3) The slower species always suffers the more deleterious effects of statistical fluctuations in a homogeneous medium.
Dynamic-reservoir lubricating device
NASA Technical Reports Server (NTRS)
Ficken, W. H.; Schulien, H. E.
1968-01-01
Dynamic-reservoir lubricating device supplies controlled amounts of lubricating oil to ball bearings during operation of the bearings. The dynamic reservoir lubricating device includes a rotating reservoir nut, a hollow cylinder filled with lubricating oil, flow restrictors and a ball bearing retainer.
Reservoirs typically have elevated fish mercury (Hg) levels compared to natural lakes and rivers. A unique feature of reservoirs is water-level management which can result in sediment exposure to the air. The objective of this study is to identify how reservoir water-level fluct...
Geothermal Reservoirs: Products of Cooling Plutons
Denis L. Norton
2002-09-24
The goals of this project were to develop an in depth understanding of how geothermal reservoirs form and elucidate those features that could potentially be useful in exploration and development of additional energy reserves. Collaboration with Jeff Hulen, EGI helped closely coordinate theoretical concepts and computational experiments with geologic reality in fulfillment of the tasks for this project. Initial reconnaissance computations with Tom Brikowski, University of Texas were critical in realizing the final products of this project. The products of this work contribute basic understanding of the dynamical conditions attendant to the formation of reservoirs in general and the Geysers reservoir in particular. The most exciting of the discoveries were a combination of mineralogical, computational, and geothermometric data sets that revealed a chaotic-like behavior of the processes is critical in the formation of reservoirs near cooling plutions. This discovery provides a fundamental basis for improving resource assessment and exploration methods for geothermal energy associated with very young magmas. Some of the main results are documented in scientific publications, and DOE progress reports. An additional publication is in preparation on the overall significance of fracture propagation and microseismic activity around young magmas.
Effects of water-supply reservoirs on streamflow in Massachusetts
Levin, Sara B.
2016-10-06
State and local water-resource managers need modeling tools to help them manage and protect water-supply resources for both human consumption and ecological needs. The U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, has developed a decision-support tool to estimate the effects of reservoirs on natural streamflow. The Massachusetts Reservoir Simulation Tool is a model that simulates the daily water balance of a reservoir. The reservoir simulation tool provides estimates of daily outflows from reservoirs and compares the frequency, duration, and magnitude of the volume of outflows from reservoirs with estimates of the unaltered streamflow that would occur if no dam were present. This tool will help environmental managers understand the complex interactions and tradeoffs between water withdrawals, reservoir operational practices, and reservoir outflows needed for aquatic habitats.A sensitivity analysis of the daily water balance equation was performed to identify physical and operational features of reservoirs that could have the greatest effect on reservoir outflows. For the purpose of this report, uncontrolled releases of water (spills or spillage) over the reservoir spillway were considered to be a proxy for reservoir outflows directly below the dam. The ratio of average withdrawals to the average inflows had the largest effect on spillage patterns, with the highest withdrawals leading to the lowest spillage. The size of the surface area relative to the drainage area of the reservoir also had an effect on spillage; reservoirs with large surface areas have high evaporation rates during the summer, which can contribute to frequent and long periods without spillage, even in the absence of water withdrawals. Other reservoir characteristics, such as variability of inflows, groundwater interactions, and seasonal demand patterns, had low to moderate effects on the frequency, duration, and magnitude of spillage. The
Grigoryeva, Lyudmila; Henriques, Julie; Larger, Laurent; Ortega, Juan-Pablo
2014-07-01
Reservoir computing is a recently introduced machine learning paradigm that has already shown excellent performances in the processing of empirical data. We study a particular kind of reservoir computers called time-delay reservoirs that are constructed out of the sampling of the solution of a time-delay differential equation and show their good performance in the forecasting of the conditional covariances associated to multivariate discrete-time nonlinear stochastic processes of VEC-GARCH type as well as in the prediction of factual daily market realized volatilities computed with intraday quotes, using as training input daily log-return series of moderate size. We tackle some problems associated to the lack of task-universality for individually operating reservoirs and propose a solution based on the use of parallel arrays of time-delay reservoirs.
Singular perturbations and time scales (SPaTS) in discrete control systems-An overview
NASA Technical Reports Server (NTRS)
Naidu, D. S.; Hibey, J. L.; Price, D. B.
1987-01-01
Recent developments in the theory of singular perturbations and time scales (SPaTS) in discrete control systems are reviewed. Sources of discrete models and the effect of the discretizing interval on the model are examined. The analysis of two-time scale systems is presented to bring out typical characteristic features of SPaTS. In the control of the two-time scale systems, the important issue of multirate sampling is addressed.
Optimal reservoir operation policies using novel nested algorithms
NASA Astrophysics Data System (ADS)
Delipetrev, Blagoj; Jonoski, Andreja; Solomatine, Dimitri
2015-04-01
Historically, the two most widely practiced methods for optimal reservoir operation have been dynamic programming (DP) and stochastic dynamic programming (SDP). These two methods suffer from the so called "dual curse" which prevents them to be used in reasonably complex water systems. The first one is the "curse of dimensionality" that denotes an exponential growth of the computational complexity with the state - decision space dimension. The second one is the "curse of modelling" that requires an explicit model of each component of the water system to anticipate the effect of each system's transition. We address the problem of optimal reservoir operation concerning multiple objectives that are related to 1) reservoir releases to satisfy several downstream users competing for water with dynamically varying demands, 2) deviations from the target minimum and maximum reservoir water levels and 3) hydropower production that is a combination of the reservoir water level and the reservoir releases. Addressing such a problem with classical methods (DP and SDP) requires a reasonably high level of discretization of the reservoir storage volume, which in combination with the required releases discretization for meeting the demands of downstream users leads to computationally expensive formulations and causes the curse of dimensionality. We present a novel approach, named "nested" that is implemented in DP, SDP and reinforcement learning (RL) and correspondingly three new algorithms are developed named nested DP (nDP), nested SDP (nSDP) and nested RL (nRL). The nested algorithms are composed from two algorithms: 1) DP, SDP or RL and 2) nested optimization algorithm. Depending on the way we formulate the objective function related to deficits in the allocation problem in the nested optimization, two methods are implemented: 1) Simplex for linear allocation problems, and 2) quadratic Knapsack method in the case of nonlinear problems. The novel idea is to include the nested
Status of Blue Ridge Reservoir
Not Available
1990-09-01
This is one in a series of reports prepared by the Tennessee Valley Authority (TVA) for those interested in the conditions of TVA reservoirs. This overview of Blue Ridge Reservoir summarizes reservoir and watershed characteristics, reservoir uses and use impairments, water quality and aquatic biological conditions, and activities of reservoir management agencies. This information was extracted from the most current reports and data available, as well as interview with water resource professionals in various federal, state, and local agencies. Blue Ridge Reservoir is a single-purpose hydropower generating project. When consistent with this primary objective, the reservoir is also operated to benefit secondary objectives including water quality, recreation, fish and aquatic habitat, development of shoreline, aesthetic quality, and other public and private uses that support overall regional economic growth and development. 8 refs., 1 fig.
Archeological inundation studies: Manual for reservoir managers. Contract report
Ware, J.A.
1989-09-01
Twentieth century demands for water, electricity, and flood control in the United States have resulted in the damming and impoundment of most of America's large rivers and streams. The impact of such activities on North American archeological and historical resources is difficult to measure. Concern for mitigating the impact of dam construction and reservoir impoundment resulted in the Reservoir Salvage Act of 1960, as amended in 1974, which requires that any US agency undertaking dam construction must provide written notice to the Secretary of the Interior, who shall then cause a survey to be conducted for archeological sites, either by the Department of the Interior or by the Federal agency undertaking the construction project. Development and operation of freshwater reservoirs create a variety of potential impacts on archeological resources. These impacts accrue from several sources, including mechanical, biochemical, and human and other processes associated with the reservoir environment. This report summarizes the findings of the National Reservoir Inundation Study, a multi-agency project designed to assess the range of effects of inundation on archeological resources. Potential effects are discussed within three discrete zones of differential impact: (a) the conservation pool, (b) the fluctuation zone, and (c) the backshore zone.
Cavity State Reservoir Engineering in Circuit Quantum Electrodynamics
NASA Astrophysics Data System (ADS)
Holland, Eric T.
Engineered quantum systems are poised to revolutionize information science in the near future. A persistent challenge in applied quantum technology is creating controllable, quantum interactions while preventing information loss to the environment, decoherence. In this thesis, we realize mesoscopic superconducting circuits whose macroscopic collective degrees of freedom, such as voltages and currents, behave quantum mechanically. We couple these mesoscopic devices to microwave cavities forming a cavity quantum electrodynamics (QED) architecture comprised entirely of circuit elements. This application of cavity QED is dubbed Circuit QED and is an interdisciplinary field seated at the intersection of electrical engineering, superconductivity, quantum optics, and quantum information science. Two popular methods for taming active quantum systems in the presence of decoherence are discrete feedback conditioned on an ancillary system or quantum reservoir engineering. Quantum reservoir engineering maintains a desired subset of a Hilbert space through a combination of drives and designed entropy evacuation. Circuit QED provides a favorable platform for investigating quantum reservoir engineering proposals. A major advancement of this thesis is the development of a quantum reservoir engineering protocol which maintains the quantum state of a microwave cavity in the presence of decoherence. This thesis synthesizes strongly coupled, coherent devices whose solutions to its driven, dissipative Hamiltonian are predicted a priori. This work lays the foundation for future advancements in cavity centered quantum reservoir engineering protocols realizing hardware efficient circuit QED designs.
Chaos in Periodic Discrete Systems
NASA Astrophysics Data System (ADS)
Shi, Yuming; Zhang, Lijuan; Yu, Panpan; Huang, Qiuling
This paper focuses on chaos in periodic discrete systems, whose state space may vary with time. Some close relationships between some chaotic dynamical behaviors of a periodic discrete system and its autonomous induced system are given. Based on these relationships, several criteria of chaos are established and some sufficient conditions for no chaos are given for periodic discrete systems. Further, it is shown that a finite-dimensional linear periodic discrete system is not chaotic in the sense of Li-Yorke or Wiggins. In particular, an interesting problem of whether nonchaotic rules may generate a chaotic system is studied, with some examples provided, one of which surprisingly shows that a composition of globally asymptotically stable maps can be chaotic. In addition, some properties of sign pattern matrices of non-negative square matrices are given for convenience of the study.
Microscopic derivation of discrete hydrodynamics.
Español, Pep; Anero, Jesús G; Zúñiga, Ignacio
2009-12-28
By using the standard theory of coarse graining based on Zwanzig's projection operator, we derive the dynamic equations for discrete hydrodynamic variables. These hydrodynamic variables are defined in terms of the Delaunay triangulation. The resulting microscopically derived equations can be understood, a posteriori, as a discretization on an arbitrary irregular grid of the Navier-Stokes equations. The microscopic derivation provides a set of discrete equations that exactly conserves mass, momentum, and energy and the dissipative part of the dynamics produces strict entropy increase. In addition, the microscopic derivation provides a practical implementation of thermal fluctuations in a way that the fluctuation-dissipation theorem is satisfied exactly. This paper points toward a close connection between coarse-graining procedures from microscopic dynamics and discretization schemes for partial differential equations.
Bathymetry and capacity of Blackfoot Reservoir, Caribou County, Idaho, 2011
Wood, Molly S.; Skinner, Kenneth D.; Fosness, Ryan L.
2012-01-01
The U.S. Geological Survey (USGS), in cooperation with the Shoshone-Bannock Tribes, surveyed the bathymetry and selected above-water sections of Blackfoot Reservoir, Caribou County, Idaho, in 2011. Reservoir operators manage releases from Government Dam on Blackfoot Reservoir based on a stage-capacity relation developed about the time of dam construction in the early 1900s. Reservoir operation directly affects the amount of water that is available for irrigation of agricultural land on the Fort Hall Indian Reservation and surrounding areas. The USGS surveyed the below-water sections of the reservoir using a multibeam echosounder and real-time kinematic global positioning system (RTK-GPS) equipment at full reservoir pool in June 2011, covering elevations from 6,090 to 6,119 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). The USGS used data from a light detection and ranging (LiDAR) survey performed in 2000 to map reservoir bathymetry from 6,116 to 6,124 ft NAVD 88, which were mostly in depths too shallow to measure with the multibeam echosounder, and most of the above-water section of the reservoir (above 6,124 ft NAVD 88). Selected points and bank erosional features were surveyed by the USGS using RTK-GPS and a total station at low reservoir pool in September 2011 to supplement and verify the LiDAR data. The stage-capacity relation was revised and presented in a tabular format. The datasets show a 2.0-percent decrease in capacity from the original survey, due to sedimentation or differences in accuracy between surveys. A 1.3-percent error also was detected in the previously used capacity table and measured water-level elevation because of questionable reference elevation at monitoring stations near Government Dam. Reservoir capacity in 2011 at design maximum pool of 6,124 ft above NAVD 88 was 333,500 acre-ft.
Dessouky, Mohamed M; Elrashidy, Mohamed A; Taha, Taha E; Abdelkader, Hatem M
2016-05-01
The different discrete transform techniques such as discrete cosine transform (DCT), discrete sine transform (DST), discrete wavelet transform (DWT), and mel-scale frequency cepstral coefficients (MFCCs) are powerful feature extraction techniques. This article presents a proposed computer-aided diagnosis (CAD) system for extracting the most effective and significant features of Alzheimer's disease (AD) using these different discrete transform techniques and MFCC techniques. Linear support vector machine has been used as a classifier in this article. Experimental results conclude that the proposed CAD system using MFCC technique for AD recognition has a great improvement for the system performance with small number of significant extracted features, as compared with the CAD system based on DCT, DST, DWT, and the hybrid combination methods of the different transform techniques.
Discrete solitons in graphene metamaterials
NASA Astrophysics Data System (ADS)
Bludov, Yu. V.; Smirnova, D. A.; Kivshar, Yu. S.; Peres, N. M. R.; Vasilevskiy, M. I.
2015-01-01
We study nonlinear properties of multilayer metamaterials created by graphene sheets separated by dielectric layers. We demonstrate that such structures can support localized nonlinear modes described by the discrete nonlinear Schrödinger equation and that its solutions are associated with stable discrete plasmon solitons. We also analyze the nonlinear surface modes in truncated graphene metamaterials being a nonlinear analog of surface Tamm states.
Concurrency and discrete event control
NASA Technical Reports Server (NTRS)
Heymann, Michael
1990-01-01
Much of discrete event control theory has been developed within the framework of automata and formal languages. An alternative approach inspired by the theories of process-algebra as developed in the computer science literature is presented. The framework, which rests on a new formalism of concurrency, can adequately handle nondeterminism and can be used for analysis of a wide range of discrete event phenomena.
Analysis of discretization errors in LES
NASA Technical Reports Server (NTRS)
Ghosal, Sandip
1995-01-01
All numerical simulations of turbulence (DNS or LES) involve some discretization errors. The integrity of such simulations therefore depend on our ability to quantify and control such errors. In the classical literature on analysis of errors in partial differential equations, one typically studies simple linear equations (such as the wave equation or Laplace's equation). The qualitative insight gained from studying such simple situations is then used to design numerical methods for more complex problems such as the Navier-Stokes equations. Though such an approach may seem reasonable as a first approximation, it should be recognized that strongly nonlinear problems, such as turbulence, have a feature that is absent in linear problems. This feature is the simultaneous presence of a continuum of space and time scales. Thus, in an analysis of errors in the one dimensional wave equation, one may, without loss of generality, rescale the equations so that the dependent variable is always of order unity. This is not possible in the turbulence problem since the amplitudes of the Fourier modes of the velocity field have a continuous distribution. The objective of the present research is to provide some quantitative measures of numerical errors in such situations. Though the focus of this work is LES, the methods introduced here can be just as easily applied to DNS. Errors due to discretization of the time-variable are neglected for the purpose of this analysis.
Su, Yuliang; Ren, Long; Meng, Fankun; Xu, Chen; Wang, Wendong
2015-01-01
Stimulated reservoir volume (SRV) fracturing in tight oil reservoirs often induces complex fracture-network growth, which has a fundamentally different formation mechanism from traditional planar bi-winged fracturing. To reveal the mechanism of fracture network propagation, this paper employs a modified displacement discontinuity method (DDM), mechanical mechanism analysis and initiation and propagation criteria for the theoretical model of fracture network propagation and its derivation. A reasonable solution of the theoretical model for a tight oil reservoir is obtained and verified by a numerical discrete method. Through theoretical calculation and computer programming, the variation rules of formation stress fields, hydraulic fracture propagation patterns (FPP) and branch fracture propagation angles and pressures are analyzed. The results show that during the process of fracture propagation, the initial orientation of the principal stress deflects, and the stress fields at the fracture tips change dramatically in the region surrounding the fracture. Whether the ideal fracture network can be produced depends on the geological conditions and on the engineering treatments. This study has both theoretical significance and practical application value by contributing to a better understanding of fracture network propagation mechanisms in unconventional oil/gas reservoirs and to the improvement of the science and design efficiency of reservoir fracturing. PMID:25966285
Su, Yuliang; Ren, Long; Meng, Fankun; Xu, Chen; Wang, Wendong
2015-01-01
Stimulated reservoir volume (SRV) fracturing in tight oil reservoirs often induces complex fracture-network growth, which has a fundamentally different formation mechanism from traditional planar bi-winged fracturing. To reveal the mechanism of fracture network propagation, this paper employs a modified displacement discontinuity method (DDM), mechanical mechanism analysis and initiation and propagation criteria for the theoretical model of fracture network propagation and its derivation. A reasonable solution of the theoretical model for a tight oil reservoir is obtained and verified by a numerical discrete method. Through theoretical calculation and computer programming, the variation rules of formation stress fields, hydraulic fracture propagation patterns (FPP) and branch fracture propagation angles and pressures are analyzed. The results show that during the process of fracture propagation, the initial orientation of the principal stress deflects, and the stress fields at the fracture tips change dramatically in the region surrounding the fracture. Whether the ideal fracture network can be produced depends on the geological conditions and on the engineering treatments. This study has both theoretical significance and practical application value by contributing to a better understanding of fracture network propagation mechanisms in unconventional oil/gas reservoirs and to the improvement of the science and design efficiency of reservoir fracturing.
NASA Astrophysics Data System (ADS)
Paul, Pijush Kanti
both field and well scale observations, I found that damage intensity gradually decreases away from faults, and if the secondary features associated with the damage zones are optimally oriented for shear failure in the present day stress state, they may affect the permeability of the reservoir in both the horizontal and vertical directions. I verified the modeling results with both field (outcrop) scale and well scale observations from a number of studies and show that dynamic rupture propagation gives a reasonable first order approximation of damage zones and can be incorporated into reservoir simulation models. Using fluid simulation in a fine-scale model that included the discrete secondary features of a damage zone, I demonstrated that the permeability anisotropy due to a damage zone exists due to increased permeability along the strike of the fault and in the vertical direction. However, there is no significant change in the permeability of the damage zone in a direction perpendicular to the strike of the parent faults in the studied field. Faults are generally curved and oriented in multiple directions in a reservoir, so often they are not aligned with the simulation grid. Based on the complexity of fault geometry, a simulation grid may have complex cell geometry adjacent to the faults. I present a methodology to implement the effects of damage zones in the simulation grid, which are generally located in fault adjacent grid blocks. To incorporate the fault-related effects of permeability anisotropy in the simulation grid, I used the strike and dip of faults with reference to the grid axes. The relative effects of the dimension of the damage zone are incorporated using the normalized damage zone width with respect to cell volume and surface area. The absolute value of permeability anisotropy is then defined by several iterations of history matching with the observed production data of the studied field. Inclusion of damage zones into simulation model shows a
Magnetic susceptibility of petroleum reservoir fluids
NASA Astrophysics Data System (ADS)
Ivakhnenko, Oleksandr P.; Potter, David K.
A knowledge of the magnetic properties of petroleum reservoir fluids may provide new techniques for improved reservoir characterisation, petroleum exploration and production. However, magnetic information is currently scarce for the vast majority of reservoir fluids. For instance, there is little in the literature concerning basic magnetic susceptibility values of crude oils or formation waters. We have therefore measured the mass magnetic susceptibility ( χm) of several crude oils, refined oil fractions, and formation waters from local and world-wide sites. All the fluids measured were diamagnetic, however there were distinct differences in magnitude between the different fluid types. In particular, χm for the crude oils was more negative than for the formation waters of the same locality. The magnetic susceptibility of the oils appears to be related to their main physical and chemical properties. The results correlated with the density, residue content, API (American Petroleum Institute) gravity, viscosity, sulphur content and metal concentration of the fluids. Light fractions of crude oil were the most diamagnetic. The magnetic measurements potentially allow physical and chemical differences between the fluids to be rapidly characterised. The results suggest other possible applications, such as passive in situ magnetic susceptibility sensors for fluid monitoring (for example, the onset of water breakthrough, or the detection of migrating fines) in reservoirs, which would provide an environmentally friendly alternative to radioactive tracers. The mass magnetic susceptibilities of the fluids in relation to typical reservoir minerals may also play a role in fluid-rock interactions, such as studies of wettability. The χm of crude oil from the various world-wide oil provinces that were tested also showed some differences, possibly reflecting broad physical and chemical features of the geological history of each province.
Robust feature point matching with sparse model.
Jiang, Bo; Tang, Jin; Luo, Bin; Lin, Liang
2014-12-01
Feature point matching that incorporates pairwise constraints can be cast as an integer quadratic programming (IQP) problem. Since it is NP-hard, approximate methods are required. The optimal solution for IQP matching problem is discrete, binary, and thus sparse in nature. This motivates us to use sparse model for feature point matching problem. The main advantage of the proposed sparse feature point matching (SPM) method is that it generates sparse solution and thus naturally imposes the discrete mapping constraints approximately in the optimization process. Therefore, it can optimize the IQP matching problem in an approximate discrete domain. In addition, an efficient algorithm can be derived to solve SPM problem. Promising experimental results on both synthetic points sets matching and real-world image feature sets matching tasks show the effectiveness of the proposed feature point matching method.
Stellar photometry and astrometry with discrete point spread functions
NASA Astrophysics Data System (ADS)
Mighell, Kenneth J.
2005-08-01
The key features of the MATPHOT algorithm for precise and accurate stellar photometry and astrometry using discrete point spread functions (PSFs) are described. A discrete PSF is a sampled version of a continuous PSF, which describes the two-dimensional probability distribution of photons from a point source (star) just above the detector. The shape information about the photon scattering pattern of a discrete PSF is typically encoded using a numerical table (matrix) or an FITS (Flexible Image Transport System) image file. Discrete PSFs are shifted within an observational model using a 21-pixel-wide damped sinc function, and position-partial derivatives are computed using a five-point numerical differentiation formula. Precise and accurate stellar photometry and astrometry are achieved with undersampled CCD (charge-coupled device) observations by using supersampled discrete PSFs that are sampled two, three or more times more finely than the observational data. The precision and accuracy of the MATPHOT algorithm is demonstrated by using the C-language MPD code to analyse simulated CCD stellar observations; measured performance is compared with a theoretical performance model. Detailed analysis of simulated Next Generation Space Telescope observations demonstrate that millipixel relative astrometry and mmag photometric precision is achievable with complicated space-based discrete PSFs.
Geomechanically Coupled Simulation of Flow in Fractured Reservoirs
NASA Astrophysics Data System (ADS)
Barton, C.; Moos, D.; Hartley, L.; Baxter, S.; Foulquier, L.; Holl, H.; Hogarth, R.
2012-12-01
Capturing the necessary and sufficient detail of reservoir hydraulics to accurately evaluate reservoir behavior remains a significant challenge to the exploitation and management of fracture-dominated geothermal reservoirs. In these low matrix permeability reservoirs, stimulation response is controlled largely by the properties of natural and induced fracture networks, which are in turn controlled by the in situ stresses, the fracture distribution and connectivity and the hydraulic behavior of the fractures. This complex interaction of fracture flow systems with the present-day stress field compounds the problem of developing an effective and efficient simulation to characterize, model and predict fractured reservoir performance. We discuss here a case study of the integration of geological, geophysical, geomechanical, and reservoir engineering data to characterize the in situ stresses, the natural fracture network and the controls on fracture permeability in geothermal reservoirs. A 3D geomechanical reservoir model includes constraints on stress magnitudes and orientations, and constraints on mechanical rock properties and the fractures themselves. Such a model is essential to understanding reservoir response to stimulation and production in low matrix permeability, fracture-dominated reservoirs. The geomechanical model for this study was developed using petrophysical, drilling, and wellbore image data along with direct well test measurements and was mapped to a 3D structural grid to facilitate coupled simulation of the fractured reservoir. Wellbore image and stimulation test data were used along with microseismic data acquired during the test to determine the reservoir fracture architecture and to provide control points for a realistic inter-connected discrete fracture network. As most fractures are stress-sensitive, their hydraulic conductivities will change with changes in bottomhole flowing and reservoir pressures, causing variations in production profiles
Hantavirus immunology of rodent reservoirs: current status and future directions.
Schountz, Tony; Prescott, Joseph
2014-03-14
Hantaviruses are hosted by rodents, insectivores and bats. Several rodent-borne hantaviruses cause two diseases that share many features in humans, hemorrhagic fever with renal syndrome in Eurasia or hantavirus cardiopulmonary syndrome in the Americas. It is thought that the immune response plays a significant contributory role in these diseases. However, in reservoir hosts that have been closely examined, little or no pathology occurs and infection is persistent despite evidence of adaptive immune responses. Because most hantavirus reservoirs are not model organisms, it is difficult to conduct meaningful experiments that might shed light on how the viruses evade sterilizing immune responses and why immunopathology does not occur. Despite these limitations, recent advances in instrumentation and bioinformatics will have a dramatic impact on understanding reservoir host responses to hantaviruses by employing a systems biology approach to identify important pathways that mediate virus/reservoir relationships.
Fractured petroleum reservoirs
Firoozabadi, A.; Chang, E.; Tang, G.Q.
2000-01-10
Total compressibility in a fractured reservoir is estimated using the pressure response due to gravitational potential variations. Both the moon and the sun gravitational potentials are accounted for using the full expression by inclusion of longer-period components. The semi-diurnal and diurnal pressure data show substantial long-term variations. The gravitational potential also contains the same variation trend; the ratio between the potential and pressure has a fairly uniform value over successive cycles. The computed total compressibility is also fairly constant and independent of the cycle. Results show the effects of the time interval over which the pressure measurements are performed as well as the location.
Encapsulated microsensors for reservoir interrogation
Scott, Eddie Elmer; Aines, Roger D.; Spadaccini, Christopher M.
2016-03-08
In one general embodiment, a system includes at least one microsensor configured to detect one or more conditions of a fluidic medium of a reservoir; and a receptacle, wherein the receptacle encapsulates the at least one microsensor. In another general embodiment, a method include injecting the encapsulated at least one microsensor as recited above into a fluidic medium of a reservoir; and detecting one or more conditions of the fluidic medium of the reservoir.
Reservoir management cost-cutting
Gulati, M.S.
1996-12-31
This article by Mohinder S. Gulati, Chief Engineer, Unocal Geothermal Operations, discusses cost cutting in geothermal reservoir management. The reservoir engineer or geoscientist can make a big difference in the economical outcome of a project by improving well performance and thus making geothermal energy more competitive in the energy marketplace. Bringing plants online in less time and proving resources to reduce the cycle time are some of the ways to reduce reservoir management costs discussed in this article.
Discrete solitons in electromechanical resonators.
Syafwan, M; Susanto, H; Cox, S M
2010-02-01
We consider a particular type of parametrically driven discrete Klein-Gordon system describing microdevices and nanodevices, with integrated electrical and mechanical functionality. Using a multiscale expansion method we reduce the system to a discrete nonlinear Schrödinger equation. Analytical and numerical calculations are performed to determine the existence and stability of fundamental bright and dark discrete solitons admitted by the Klein-Gordon system through the discrete Schrödinger equation. We show that a parametric driving can not only destabilize onsite bright solitons, but also stabilize intersite bright discrete solitons and onsite and intersite dark solitons. Most importantly, we show that there is a range of values of the driving coefficient for which dark solitons are stable, for any value of the coupling constant, i.e., oscillatory instabilities are totally suppressed. Stability windows of all the fundamental solitons are presented and approximations to the onset of instability are derived using perturbation theory, with accompanying numerical results. Numerical integrations of the Klein-Gordon equation are performed, confirming the relevance of our analysis.
Distributed Relaxation for Conservative Discretizations
NASA Technical Reports Server (NTRS)
Diskin, Boris; Thomas, James L.
2001-01-01
A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.
All-optical reservoir computing.
Duport, François; Schneider, Bendix; Smerieri, Anteo; Haelterman, Marc; Massar, Serge
2012-09-24
Reservoir Computing is a novel computing paradigm that uses a nonlinear recurrent dynamical system to carry out information processing. Recent electronic and optoelectronic Reservoir Computers based on an architecture with a single nonlinear node and a delay loop have shown performance on standardized tasks comparable to state-of-the-art digital implementations. Here we report an all-optical implementation of a Reservoir Computer, made of off-the-shelf components for optical telecommunications. It uses the saturation of a semiconductor optical amplifier as nonlinearity. The present work shows that, within the Reservoir Computing paradigm, all-optical computing with state-of-the-art performance is possible.
Integrable structure in discrete shell membrane theory
Schief, W. K.
2014-01-01
We present natural discrete analogues of two integrable classes of shell membranes. By construction, these discrete shell membranes are in equilibrium with respect to suitably chosen internal stresses and external forces. The integrability of the underlying equilibrium equations is proved by relating the geometry of the discrete shell membranes to discrete O surface theory. We establish connections with generalized barycentric coordinates and nine-point centres and identify a discrete version of the classical Gauss equation of surface theory. PMID:24808755
Discretization errors in particle tracking
NASA Astrophysics Data System (ADS)
Carmon, G.; Mamman, N.; Feingold, M.
2007-03-01
High precision video tracking of microscopic particles is limited by systematic and random errors. Systematic errors are partly due to the discretization process both in position and in intensity. We study the behavior of such errors in a simple tracking algorithm designed for the case of symmetric particles. This symmetry algorithm uses interpolation to estimate the value of the intensity at arbitrary points in the image plane. We show that the discretization error is composed of two parts: (1) the error due to the discretization of the intensity, bD and (2) that due to interpolation, bI. While bD behaves asymptotically like N-1 where N is the number of intensity gray levels, bI is small when using cubic spline interpolation.
Reservoir simulation in a North Sea reservoir experiencing significant compaction drive
Cook, C.C.; Jewell, S.
1995-12-31
The Valhall field in the Norwegian North Sea is a high porosity chalk reservoir undergoing primary pressure depletion. Over the last ten years there have been a number of computer modeling studies of the field which have all assumed an original oil-in-place of approximately 2,000 MMSTB (318.0{times}10{sup 6}m{sup 3}) to the present due to the addition of wells and the optimization of completion techniques. However, the single most important and unique feature influencing Valhall long term production performance is reservoir rock compaction. This paper describes the mathematical model used to simulate reservoir performance in a compacting reservoir with specific discussion regarding the proportion of oil produced by each physical recovery process. An understanding of the recovery mechanisms and their relative importance is critical for the successful management of the field. This paper also presents an alternative method for evaluating the various recovery processes using a simple solution to the material balance equation. This is used to substantiate the magnitude of the various recovery mechanisms identified in the simulation model.
Dissipative discrete breathers: periodic, quasiperiodic, chaotic, and mobile.
Martínez, P J; Meister, M; Floría, L M; Falo, F
2003-06-01
The properties of discrete breathers in dissipative one-dimensional lattices of nonlinear oscillators subject to periodic driving forces are reviewed. We focus on oscillobreathers in the Frenkel-Kontorova chain and rotobreathers in a ladder of Josephson junctions. Both types of exponentially localized solutions are easily obtained numerically using adiabatic continuation from the anticontinuous limit. Linear stability (Floquet) analysis allows the characterization of different types of bifurcations experienced by periodic discrete breathers. Some of these bifurcations produce nonperiodic localized solutions, namely, quasiperiodic and chaotic discrete breathers, which are generally impossible as exact solutions in Hamiltonian systems. Within a certain range of parameters, propagating breathers occur as attractors of the dissipative dynamics. General features of these excitations are discussed and the Peierls-Nabarro barrier is addressed. Numerical scattering experiments with mobile breathers reveal the existence of two-breather bound states and allow a first glimpse at the intricate phenomenology of these special multibreather configurations.
A Discrete Model for Color Naming
NASA Astrophysics Data System (ADS)
Menegaz, G.; Le Troter, A.; Sequeira, J.; Boi, J. M.
2006-12-01
The ability to associate labels to colors is very natural for human beings. Though, this apparently simple task hides very complex and still unsolved problems, spreading over many different disciplines ranging from neurophysiology to psychology and imaging. In this paper, we propose a discrete model for computational color categorization and naming. Starting from the 424 color specimens of the OSA-UCS set, we propose a fuzzy partitioning of the color space. Each of the 11 basic color categories identified by Berlin and Kay is modeled as a fuzzy set whose membership function is implicitly defined by fitting the model to the results of an ad hoc psychophysical experiment (Experiment 1). Each OSA-UCS sample is represented by a feature vector whose components are the memberships to the different categories. The discrete model consists of a three-dimensional Delaunay triangulation of the CIELAB color space which associates each OSA-UCS sample to a vertex of a 3D tetrahedron. Linear interpolation is used to estimate the membership values of any other point in the color space. Model validation is performed both directly, through the comparison of the predicted membership values to the subjective counterparts, as evaluated via another psychophysical test (Experiment 2), and indirectly, through the investigation of its exploitability for image segmentation. The model has proved to be successful in both cases, providing an estimation of the membership values in good agreement with the subjective measures as well as a semantically meaningful color-based segmentation map.
Fingerprinting Persistent Turbidity in Sheep Creek Reservoir, Owhyee, Nevada
NASA Astrophysics Data System (ADS)
Ransom, R. N.; Hooper, R. L.; Kerner, D.; Nicols, S.
2007-12-01
Sheep Creek Reservoir near Owyhee, NV is historically a quality rainbow trout fishery. Persistent high-turbidity has been an issue since a major storm event in 2005 resulted in surface water runoff into the Reservoir. The high turbidity is adversely impacting the quality of the fishery. Initial turbidity measurements in 2005 were upwards of 80NTU and these numbers have only decreased to 30NTU over the past two summers. Field parameters indicate the turbidity is associated with high total suspended solids (TSS) and not algae. Five water samples collected from around the reservoir during June, 2007 indicated uniform TSS values in the range of 5 to 12mg/L and oriented powder x-ray diffraction(XRD) and transmission electron microscopy(TEM) analyses of suspended sediment shows very uniform suspended particulate mineralogy including smectite, mixed layer illite/smectite (I/S), discrete illite, lesser amounts of kaolin, sub-micron quartz and feldspar. Diatoms represent a ubiquitous but minor component of the suspended solids. Six soil samples collected from possible source areas around the reservoir were analyzed using both XRD and TEM to see if a source area for the suspended solids could be unambiguously identified. Soils on the east side of the reservoir contain smectite and mixed layer I/S but very little of the other clays. The less than 2 micron size fraction from soils collected from a playa on the topographic bench immediately to the west of the reservoir show a mineralogic finger-print essentially identical to the current suspended sediment. The suspended sediment probably originates on the bench to the west of the reservoir and cascades into the reservoir over the topographic break during extreme storm events. The topographic relief, short travel distance and lack of a suitable vegetated buffer zone to the west are all consistent with a primary persistent suspended sediment source from the west. Identification of the sediment source allows for design of a cost
Reservoir Modeling for Production Management
Brown, Donald W.
1989-03-21
For both petroleum and geothermal resources, many of the reservoirs are fracture dominated--rather than matrix-permeability controlled. For such reservoirs, a knowledge of the pressure-dependent permeability of the interconnected system of natural joints (i.e., pre-existing fractures) is critical to the efficient exploitation of the resource through proper pressure management. Our experience and that reported by others indicates that a reduction in the reservoir pressure sometimes leads to an overall reduction in production rate due to the ''pinching off'' of the joint network, rather than the anticipated increase in production rate. This effect occurs not just in the vicinity of the wellbore, where proppants are sometimes employed, but throughout much of the reservoir region. This follows from the fact that under certain circumstances, the decline in fracture permeability (or conductivity) with decreasing reservoir pressure exceeds the far-field reservoir ''drainage'' flow rate increase due to the increased pressure gradient. Further, a knowledge of the pressure-dependent joint permeability could aid in designing more appropriate secondary recovery strategies in petroleum reservoirs or reinjection procedures for geothermal reservoirs.
HEC Activities in Reservoir Analysis.
1980-06-01
June 1979. Now, HEC-5, "Simulation of Flood Con- trol and Conservation Systems," (9) is our primary reservoir simulation program. Since its June release...are being incorporated into the reservoir simulation model HEC-5. The objective is to provide a computer program and methodology for total water
Reduced discretization error in HZETRN
Slaba, Tony C.; Blattnig, Steve R.; Tweed, John
2013-02-01
The deterministic particle transport code HZETRN is an efficient analysis tool for studying the effects of space radiation on humans, electronics, and shielding materials. In a previous work, numerical methods in the code were reviewed, and new methods were developed that further improved efficiency and reduced overall discretization error. It was also shown that the remaining discretization error could be attributed to low energy light ions (A < 4) with residual ranges smaller than the physical step-size taken by the code. Accurately resolving the spectrum of low energy light particles is important in assessing risk associated with astronaut radiation exposure. In this work, modifications to the light particle transport formalism are presented that accurately resolve the spectrum of low energy light ion target fragments. The modified formalism is shown to significantly reduce overall discretization error and allows a physical approximation to be removed. For typical step-sizes and energy grids used in HZETRN, discretization errors for the revised light particle transport algorithms are shown to be less than 4% for aluminum and water shielding thicknesses as large as 100 g/cm{sup 2} exposed to both solar particle event and galactic cosmic ray environments.
Discrete tomography in neutron radiography
NASA Astrophysics Data System (ADS)
Kuba, Attila; Rodek, Lajos; Kiss, Zoltán; Ruskó, László; Nagy, Antal; Balaskó, Márton
2005-04-01
Discrete tomography (DT) is an imaging technique for reconstructing discrete images from their projections using the knowledge that the object to be reconstructed contains only a few homogeneous materials characterized by known discrete absorption values. One of the main reasons for applying DT is that we will hopefully require relatively few projections. Using discreteness and some a priori information (such as an approximate shape of the object) we can apply two DT methods in neutron imaging by reducing the problem to an optimization task. The first method is a special one because it is only suitable if the object is composed of cylinders and sphere shapes. The second method is a general one in the sense that it can be used for reconstructing objects of any shape. Software was developed and physical experiments performed in order to investigate the effects of several reconstruction parameters: the number of projections, noise levels, and complexity of the object to be reconstructed. We give a summary of the experimental results and make a comparison of the results obtained using a classical reconstruction technique (FBP). The programs we developed are available in our DT reconstruction program package DIRECT.
Police Discretion: A Selected Bibliography.
ERIC Educational Resources Information Center
Brenner, Robert N.; Kravitz, Marjorie
This bibliography was compiled with two goals. The first goal is to provide police administrators and officers with an overview of the issues involved in developing guidelines for police discretion and a discussion of the options available. The second goal is to demonstrate the need for continuing dialogue and interaction between lawmakers, law…
Material point method modeling in oil and gas reservoirs
Vanderheyden, William Brian; Zhang, Duan
2016-06-28
A computer system and method of simulating the behavior of an oil and gas reservoir including changes in the margins of frangible solids. A system of equations including state equations such as momentum, and conservation laws such as mass conservation and volume fraction continuity, are defined and discretized for at least two phases in a modeled volume, one of which corresponds to frangible material. A material point model technique for numerically solving the system of discretized equations, to derive fluid flow at each of a plurality of mesh nodes in the modeled volume, and the velocity of at each of a plurality of particles representing the frangible material in the modeled volume. A time-splitting technique improves the computational efficiency of the simulation while maintaining accuracy on the deformation scale. The method can be applied to derive accurate upscaled model equations for larger volume scale simulations.
Tertiary carbonate reservoirs in Indonesia
Nayoan, G.A.S.; Arpandi; Siregar, M.
1981-01-01
Hydrocarbon production from Tertiary carbonate reservoirs accounted for ca. 10% of daily Indonesian production at the beginning of 1978. Environmentally, the reservoirs appear as parts of reef complexes and high-energy carbonate deposits within basinal areas situated mainly in the back arc of the archipelago. Good porosities of the reservoirs are represented by vugular/moldic and intergranular porosity types. The reservoirs are capable of producing prolific amounts of hydrocarbons: production tests in Salawati-Irian Jaya reaches maximum values of 32,000 bpd, and in Arun-North Sumatra tests recorded 200 MMCF gas/day. Significant hydrocarbon accumulations are related to good reservoir rocks in carbonates deposited as patch reefs, pinnacle reefs, and platform complexes. Exploration efforts expand continuously within carbonate formations which are extensive horizontally as well as vertically in the Tertiary stratigraphic column.
Stochastic thermodynamics with information reservoirs
NASA Astrophysics Data System (ADS)
Barato, Andre C.; Seifert, Udo
2014-10-01
We generalize stochastic thermodynamics to include information reservoirs. Such information reservoirs, which can be modeled as a sequence of bits, modify the second law. For example, work extraction from a system in contact with a single heat bath becomes possible if the system also interacts with an information reservoir. We obtain an inequality, and the corresponding fluctuation theorem, generalizing the standard entropy production of stochastic thermodynamics. From this inequality we can derive an information processing entropy production, which gives the second law in the presence of information reservoirs. We also develop a systematic linear response theory for information processing machines. For a unicyclic machine powered by an information reservoir, the efficiency at maximum power can deviate from the standard value of 1 /2 . For the case where energy is consumed to erase the tape, the efficiency at maximum erasure rate is found to be 1 /2 .
Reservoir High's TE Site Wins Web Site of the Month
ERIC Educational Resources Information Center
Tech Directions, 2008
2008-01-01
This article features "Mr. Rhine's Technology Education Web Site," a winner of the Web Site of the Month. This Web site was designed by Luke Rhine, a teacher at the Reservoir High School in Fulton, Maryland. Rhine's Web site offers course descriptions and syllabuses, class calendars, lectures and presentations, design briefs and other course…
FRACTURED PETROLEUM RESERVOIRS
Abbas Firoozabadi
1999-06-11
The four chapters that are described in this report cover a variety of subjects that not only give insight into the understanding of multiphase flow in fractured porous media, but they provide also major contribution towards the understanding of flow processes with in-situ phase formation. In the following, a summary of all the chapters will be provided. Chapter I addresses issues related to water injection in water-wet fractured porous media. There are two parts in this chapter. Part I covers extensive set of measurements for water injection in water-wet fractured porous media. Both single matrix block and multiple matrix blocks tests are covered. There are two major findings from these experiments: (1) co-current imbibition can be more efficient than counter-current imbibition due to lower residual oil saturation and higher oil mobility, and (2) tight fractured porous media can be more efficient than a permeable porous media when subjected to water injection. These findings are directly related to the type of tests one can perform in the laboratory and to decide on the fate of water injection in fractured reservoirs. Part II of Chapter I presents modeling of water injection in water-wet fractured media by modifying the Buckley-Leverett Theory. A major element of the new model is the multiplication of the transfer flux by the fractured saturation with a power of 1/2. This simple model can account for both co-current and counter-current imbibition and computationally it is very efficient. It can be orders of magnitude faster than a conventional dual-porosity model. Part II also presents the results of water injection tests in very tight rocks of some 0.01 md permeability. Oil recovery from water imbibition tests from such at tight rock can be as high as 25 percent. Chapter II discusses solution gas-drive for cold production from heavy-oil reservoirs. The impetus for this work is the study of new gas phase formation from in-situ process which can be significantly
Richardson, J.G.; Sangree, J.B.; Sneider, R.M.
1987-12-01
Braided stream deposits, described in a previous article in this series, and meandering stream deposits commonly are excellent reservoirs. Meandering high-sinuousity channels are found on flat alluvial plains with slopes less than 1 1/2/sup 0/ (0.026 rad). These rivers have wide ranges of discharges from low-water flow to flood stage. Two main processes are responsible for development of sand bodies. These are point-bar deposits left by channel migration, and oxbow-lake deposits left in loops of the river course abandoned when the stream cuts a new course during flooding. Extremely high floods spill over the banks and deposit sheets of very fine sand, silt, and clay onto the flood plain.
Discrete impulses in ephaptically coupled nerve fibers.
Maïna, I; Tabi, C B; Ekobena Fouda, H P; Mohamadou, A; Kofané, T C
2015-04-01
We exclusively analyze the condition for modulated waves to emerge in two ephaptically coupled nerve fibers. Through the multiple scale expansion, it is shown that a set of coupled cable-like Hodgkin-Huxley equations can be reduced to a single differential-difference nonlinear equation. The standard approach of linear stability analysis of a plane wave is used to predict regions of parameters where nonlinear structures can be observed. Instability features are shown to be importantly controlled not only by the ephaptic coupling parameter, but also by the discreteness parameter. Numerical simulations, to verify our analytical predictions, are performed, and we explore the longtime dynamics of slightly perturbed plane waves in the coupled nerve fibers. On initially exciting only one fiber, quasi-perfect interneuronal communication is discussed along with the possibility of recruiting damaged or non-myelinated nerve fibers, by myelinated ones, into conduction.
The structure of random discrete spacetime
NASA Technical Reports Server (NTRS)
Brightwell, Graham; Gregory, Ruth
1990-01-01
The usual picture of spacetime consists of a continuous manifold, together with a metric of Lorentzian signature which imposes a causal structure on the spacetime. A model, first suggested by Bombelli et al., is considered in which spacetime consists of a discrete set of points taken at random from a manifold, with only the causal structure on this set remaining. This structure constitutes a partially ordered set (or poset). Working from the poset alone, it is shown how to construct a metric on the space which closely approximates the metric on the original spacetime manifold, how to define the effective dimension of the spacetime, and how such quantities may depend on the scale of measurement. Possible desirable features of the model are discussed.
Discrete-continuous variable structural synthesis using dual methods
NASA Technical Reports Server (NTRS)
Schmit, L. A.; Fleury, C.
1980-01-01
Approximation concepts and dual methods are extended to solve structural synthesis problems involving a mix of discrete and continuous sizing type of design variables. Pure discrete and pure continuous variable problems can be handled as special cases. The basic mathematical programming statement of the structural synthesis problem is converted into a sequence of explicit approximate primal problems of separable form. These problems are solved by constructing continuous explicit dual functions, which are maximized subject to simple nonnegativity constraints on the dual variables. A newly devised gradient projection type of algorithm called DUAL 1, which includes special features for handling dual function gradient discontinuities that arise from the discrete primal variables, is used to find the solution of each dual problem. Computational implementation is accomplished by incorporating the DUAL 1 algorithm into the ACCESS 3 program as a new optimizer option. The power of the method set forth is demonstrated by presenting numerical results for several example problems, including a pure discrete variable treatment of a metallic swept wing and a mixed discrete-continuous variable solution for a thin delta wing with fiber composite skins.
NASA Astrophysics Data System (ADS)
Lee, T.; Kim, K.; Lee, K.; Lee, H.; Lee, W.
2015-12-01
Natural fractures have an effect on the fluid flow and heat transfer in the naturally fractured geothermal reservoir. However, most of the previous works in this area assumed that reservoir systems are continuum model whether it is single continuum or dual continuum. Moreover, some people have studied without continuum model but, it was just pipeline model. In this paper, we developed a generalized discrete fracture network (DFN) geothermal reservoir simulator. In the model, 2D flow is possible within a rectangular fracture, which is important in thick naturally fractured reservoirs. The DFN model developed in this study was validated for two synthetic fracture systems using a commercial thermal model, TETRAD. Comparison results showed an excellent matching between both models. However, this model is only fracture model and it can't calculate simulation of fluid flow and heat transfer in matrix. Therefore, matrix flow model will be added to this model.
Upscaling Multiphase Fluid Flow in Naturally Fractured Reservoirs
NASA Astrophysics Data System (ADS)
Matthai, S.; Maghami-Nick, H.; Belayneh, M.; Geiger, S.
2009-04-01
Hydrocarbon recovery from fractured porous reservoirs is difficult to predict as it depends on the focusing of the flow and the local balance of viscous, gravitational, and capillary forces. Hecto-metre scale sub-volumes of fractured oil reservoirs contain thousands of fractures with highly variable flow properties, dimensions and orientations. This complexity precludes direct geometric incorporation into field scale multiphase flow models. Macroscopic laws of their integral effects on multiphase flow are required. These can be investigated by DFM (discrete fracture and matrix) numerical simulations based on discrete fracture models representing fractured reservoir analogues. Here we present DFM results indicating that hecto-metre-scale relative permeability, the time to water breakthrough, and the subsequent water cut primarily depend on the fracture-to-rock matrix flux ratio, qf/qm, quantifying the proportion of the cross-sectional flux that occurs through the fractures. Relative permeability during imbibition runs is best approximated by a rate-dependent new model taking into account capillary fracture-matrix transfer. The up-scaled fractional flow function fo(sw) derived from this new kri formulation is convex with a near-infinity slope at the residual water saturation. This implies that the hector-metre scale spatially averaged Buckley-Leverett equation for fractured porous media does not contain a shock, but a long leading edge in the averaged profile of the invading phase. This dispersive behaviour marks the progressively widening saturation front and an early water breakthrough observed in the discrete fracture reservoir analogues. Since fracture porosity φf is usually only a fraction of a percent, a cross-over from krw < kro to krw/kro ≈ qf/qm occurs after the first few percent of recovery, and because qf/qm ranges between 10-1,000, sweep efficiency ignoring the positive influence of counter-current imbibition is extremely low. The accuracy of reservoir
Reservoir quality studies, Arctic National Wildlife Refuge, Alaska
Mowatt, T.C.; Banet, A. )
1991-03-01
Reservoir quality studies are part of the reservoir management and resource assessment programs of the U.S. Bureau of Land Management in Alaska. Petrographic analyses have been carried out of samples collected from surface exposures in the Arctic National Wildlife Refuge (ANWR), Alaska, to evaluate surface materials as to their potential reservoir rock qualities in the subsurface. This entails characterization of relevant petrologic-petrophysical properties, integration with regional geological-geophysical relationships, and synthesis in terms of likely diagenetic, structural, and stratigraphic conditions in the subsurface. There is a paucity of relevant data in this region. Inferences must be predicated largely on general principles and known relationships elsewhere. A spectrum of lithologies were studied, representing a substantial portion of the regional stratigraphic column. In a number of cases, particularly among the pre-Brookian samples, the rocks appear to have low reservoir potential, based on their present high degree of diagenetic maturity. There is always the possibility - deemed somewhat unlikely here - of subsurface equivalents with more favorable characteristics, due to different original compositions, textures, and/or geologic histories. Brookian sandstones and conglomerates feature samples with fair-good reservoir characteristics, with prospects of being equally good or better in the subsurface. The samples studied suggest the likelihood of horizons with viable reservoir qualities in the subsurface within the ANWR region.
Water resources review: Ocoee reservoirs, 1990
Cox, J.P.
1990-08-01
Tennessee Valley Authority (TVA) is preparing a series of reports to make technical information on individual TVA reservoirs readily accessible. These reports provide a summary of reservoir purpose and operation; physical characteristics of the reservoir and watershed; water quality conditions; aquatic biological conditions; and designated, actual and potential uses of the reservoir and impairments of those use. This reservoir status report addressed the three Ocoee Reservoirs in Polk County, Tennessee.
Collapsible sheath fluid reservoirs for flow cytometers
Mark, Graham A.
2000-01-01
The present invention is a container in the form of a single housing for holding fluid, including a first collapsible reservoir having a first valve. The first reservoir initially contains a volume of fluid. The container also includes a second reservoir, initially empty (or substantially empty), expandable to a second volume. The second reservoir has a second valve. As the volume of said first reservoir decreases, the volume of the second reservoir proportionally increases.
Archfield, Stacey A.; Carlson, Carl S.
2006-01-01
Potential ground-water contributions to reservoir storage were determined for nine reservoirs in Massachusetts that had shorelines in contact with sand and gravel aquifers. The effect of ground water on firm yield was not only substantial, but furthermore, the firm yield of a reservoir in contact with a sand and gravel aquifer was always greater when the ground-water contribution was included in the water balance. Increases in firm yield ranged from 2 to 113 percent, with a median increase in firm yield of 10 percent. Additionally, the increase in firm yield in two reservoirs was greater than 85 percent. This study identified a set of equations that are based on an analytical solution to the ground-water-flow equation for the case of one-dimensional flow in a finite-width aquifer bounded by a linear surface-water feature such as a stream. These equations, which require only five input variables, were incorporated into an existing firm-yield-estimator (FYE) model, and the potential effect of ground water on firm yield was evaluated. To apply the FYE model to a reservoir in Massachusetts, the model requires that the drainage area to the reservoir be clearly defined and that some surface water flows into the reservoir. For surface-water-body shapes having a more realistic representation of a reservoir shoreline than a stream, a comparison of ground-water-flow rates simulated by the ground-water equations with flow rates simulated by a two-dimensional, finite-difference ground-water-flow model indicate that the agreement between the simulated flow rates is within ?10 percent when the ratio of the distance from the reservoir shoreline to the aquifer boundary to the length of shoreline in contact with the aquifer is between values of 0.5 and 3.5. Idealized reservoir-aquifer systems were assumed to verify that the ground-water-flow equations were implemented correctly into the existing FYE model; however, the modified FYE model has not been validated through a comparison
Analysis of real-time reservoir monitoring : reservoirs, strategies, & modeling.
Mani, Seethambal S.; van Bloemen Waanders, Bart Gustaaf; Cooper, Scott Patrick; Jakaboski, Blake Elaine; Normann, Randy Allen; Jennings, Jim; Gilbert, Bob; Lake, Larry W.; Weiss, Chester Joseph; Lorenz, John Clay; Elbring, Gregory Jay; Wheeler, Mary Fanett; Thomas, Sunil G.; Rightley, Michael J.; Rodriguez, Adolfo; Klie, Hector; Banchs, Rafael; Nunez, Emilio J.; Jablonowski, Chris
2006-11-01
The project objective was to detail better ways to assess and exploit intelligent oil and gas field information through improved modeling, sensor technology, and process control to increase ultimate recovery of domestic hydrocarbons. To meet this objective we investigated the use of permanent downhole sensors systems (Smart Wells) whose data is fed real-time into computational reservoir models that are integrated with optimized production control systems. The project utilized a three-pronged approach (1) a value of information analysis to address the economic advantages, (2) reservoir simulation modeling and control optimization to prove the capability, and (3) evaluation of new generation sensor packaging to survive the borehole environment for long periods of time. The Value of Information (VOI) decision tree method was developed and used to assess the economic advantage of using the proposed technology; the VOI demonstrated the increased subsurface resolution through additional sensor data. Our findings show that the VOI studies are a practical means of ascertaining the value associated with a technology, in this case application of sensors to production. The procedure acknowledges the uncertainty in predictions but nevertheless assigns monetary value to the predictions. The best aspect of the procedure is that it builds consensus within interdisciplinary teams The reservoir simulation and modeling aspect of the project was developed to show the capability of exploiting sensor information both for reservoir characterization and to optimize control of the production system. Our findings indicate history matching is improved as more information is added to the objective function, clearly indicating that sensor information can help in reducing the uncertainty associated with reservoir characterization. Additional findings and approaches used are described in detail within the report. The next generation sensors aspect of the project evaluated sensors and packaging
Data requirements and acquisition for reservoir characterization
Jackson, S.; Chang, Ming Ming; Tham, Min.
1993-03-01
This report outlines the types of data, data sources and measurement tools required for effective reservoir characterization, the data required for specific enhanced oil recovery (EOR) processes, and a discussion on the determination of the optimum data density for reservoir characterization and reservoir modeling. The two basic sources of data for reservoir characterization are data from the specific reservoir and data from analog reservoirs, outcrops, and modern environments. Reservoir data can be divided into three broad categories: (1) rock properties (the container) and (2) fluid properties (the contents) and (3)interaction between reservoir rock and fluid. Both static and dynamic measurements are required.
Fish habitat degradation in U.S. reservoirs
Miranda, Leandro E.; Spickard, M.; Dunn, T.; Webb, K.M.; Aycock, J.N.; Hunt, K.
2010-01-01
As the median age of the thousands of large reservoirs (> 200 ha) in the United States tops 50, many are showing various signs of fish habitat degradation. Our goal was to identify major factors degrading fish habitat in reservoirs across the country, and to explore regional degradation patterns. An online survey including 14 metrics was scored on a 0 (no degradation) to 5 (high degradation) point scale by 221 fisheries scientists (92% response rate) to describe degradation in 482 reservoirs randomly distributed throughout the continental United States. The highest scored sources of degradation were lack of aquatic macrophytes (41% of the reservoirs scored as 4–5), lack or loss of woody debris (35% scored 4–5), mistimed water level fluctuations (34% scored 4–5), and sedimentation (31% scored 4–5). Factor analysis identified five primary degradation factors that accounted for most of the variability in the 14 degradation metrics. The factors reflected siltation, structural habitat, eutrophication, water regime, and aquatic plants. Three degradation factors were driven principally by in-reservoir processes, whereas the other two were driven by inputs from the watershed. A comparison across U.S. regions indicated significant geographical differences in degradation relative to the factors emphasized by each region. Reservoirs sometimes have been dismissed as unnatural and disruptive, but they are a product of public policy, a critical feature of landscapes, and they cannot be overlooked if managers are to effectively conserve river systems. Protection and restoration of reservoir habitats may be enhanced with a broader perspective that includes watershed management, in addition to in reservoir activities.
Fish habitat degradation in U.S. reservoirs
Miranda, L.E.; Spickard, M.; Dunn, T.; Webb, K.M.; Aycock, J.N.; Hunt, K.
2010-01-01
As the median age of the thousands of large reservoirs (> 200 ha) in the United States tops 50, many are showing various signs of fish habitat degradation. Our goal was to identify major factors degrading fish habitat in reservoirs across the country, and to explore regional degradation patterns. An online survey including 14 metrics was scored on a 0 (no degradation) to 5 (high degradation) point scale by 221 fisheries scientists (92% response rate) to describe degradation in 482 reservoirs randomly distributed throughout the continental United States. The highest scored sources of degradation were lack of aquatic macrophytes (41% of the reservoirs scored as 4-5), lack or loss of woody debris (35% scored 4-5), mistimed water level fluctuations (34% scored 4-5), and sedimentation (31% scored 4-5). Factor analysis identified five primary degradation factors that accounted for most of the variability in the 14 degradation metrics. The factors reflected siltation, structural habitat, eutrophication, water regime, and aquatic plants. Three degradation factors were driven principally by in-reservoir processes, whereas the other two were driven by inputs from the watershed. A comparison across U.S. regions indicated significant geographical differences in degradation relative to the factors emphasized by each region. Reservoirs sometimes have been dismissed as unnatural and disruptive, but they are a product of public policy, a critical feature of landscapes, and they cannot be overlooked if managers are to effectively conserve river systems. Protection and restoration of reservoir habitats may be enhanced with a broader perspective that includes watershed management, in addition to in reservoir activities.
Ryder, Robert T.
1998-01-01
equal to or less than 0.1 mD; c) low reservoir water saturation and an average water yield per well less than about 9 to 13 BW/MMCFG; d) a broadly defined updip water-block trap; e) underpressured reservoirs with a gradient ranging from 0.25 to 0.35 psi/ft; and f) reservoir temperature of at least 125? F (52? C). Other than for historical and location purposes, the term field has little or no meaning as an assessment unit for the regional accumulation. In practice, each designated field represents a production sweet spot having relatively high EURs per well that in turn merges with surrounding gas-productive regions that are generally larger in area but have lower EURs per well. This important feature of the Lower Silurian regional accumulation, whereby most wells drilled into it are gas productive, must be considered when assessing its potential for remaining recoverable gas resources. Most of the remaining gas resources reside in 'Clinton' sands and Medina Group sandstone in the basin-centered part of the accumulation where as much as several tens of TCF of natural gas may be technically recoverable. The Tuscarora Sandstone in the eastern extension of the basin-centered part of the accumulation underlies a very large area and, although commonly characterized by very low porosity and permeability and low-Btu gas, probably contains additional gas resources. Remaining undiscovered recoverable gas and oil resources in the discrete and hybrid parts of the accumulation are primarily located beneath Lake Erie.
Sebastian Schunert; Yousry Y. Azmy; Damien Fournier
2011-05-01
We present a comprehensive error estimation of four spatial discretization schemes of the two-dimensional Discrete Ordinates (SN) equations on Cartesian grids utilizing a Method of Manufactured Solution (MMS) benchmark suite based on variants of Larsen’s benchmark featuring different orders of smoothness of the underlying exact solution. The considered spatial discretization schemes include the arbitrarily high order transport methods of the nodal (AHOTN) and characteristic (AHOTC) types, the discontinuous Galerkin Finite Element method (DGFEM) and the recently proposed higher order diamond difference method (HODD) of spatial expansion orders 0 through 3. While AHOTN and AHOTC rely on approximate analytical solutions of the transport equation within a mesh cell, DGFEM and HODD utilize a polynomial expansion to mimick the angular flux profile across each mesh cell. Intuitively, due to the higher degree of analyticity, we expect AHOTN and AHOTC to feature superior accuracy compared with DGFEM and HODD, but at the price of potentially longer grind times and numerical instabilities. The latter disadvantages can result from the presence of exponential terms evaluated at the cell optical thickness that arise from the semianalytical solution process. This work quantifies the order of accuracy and the magnitude of the error of all four discretization methods for different optical thicknesses, scattering ratios and degrees of smoothness of the underlying exact solutions in order to verify or contradict the aforementioned intuitive expectation.
Cometary activity, discrete outgassing areas, and dust-jet formation
NASA Technical Reports Server (NTRS)
Sekanina, Z.
1991-01-01
Conceptual models for various types of features observed in cometary comae (jets, spirals, halos, fans, etc.), their computer simulation, and the hydrodynamic models for jet formation are critically reviewed, and evidence for anisotropic, strongly collimated flows of ejecta emanating from discrete active regions (vents) on the rotating cometary nuclei is presented. Techniques employed to generate synthetic comet images that simulate the features observed are described, and their relevance to the primary objects of coma-morphology studies is discussed. Modeling of temporal variations in the water emission from discrete active regions suggests that production curves asymmetric with respect to perihelion should be commonplace. Critical comparisons with the activity profiles of Enke's comet and with light curves of disappearing comets and comets that undergo outbursts are presented. Recent developments in the understanding of the processes that cause the nongravitational perturbations of cometary motions are reviewed, and the observed discontinuities are identified with the birth of new sources and/or deactivation of old vents.
NASA Astrophysics Data System (ADS)
Holmes, Jon L.
1999-05-01
The Features area of JCE Online is now readily accessible through a single click from our home page. In the Features area each column is linked to its own home page. These column home pages also have links to them from the online Journal Table of Contents pages or from any article published as part of that feature column. Using these links you can easily find abstracts of additional articles that are related by topic. Of course, JCE Online+ subscribers are then just one click away from the entire article. Finding related articles is easy because each feature column "site" contains links to the online abstracts of all the articles that have appeared in the column. In addition, you can find the mission statement for the column and the email link to the column editor that I mentioned above. At the discretion of its editor, a feature column site may contain additional resources. As an example, the Chemical Information Instructor column edited by Arleen Somerville will have a periodically updated bibliography of resources for teaching and using chemical information. Due to the increase in the number of these resources available on the WWW, it only makes sense to publish this information online so that you can get to these resources with a simple click of the mouse. We expect that there will soon be additional information and resources at several other feature column sites. Following in the footsteps of the Chemical Information Instructor, up-to-date bibliographies and links to related online resources can be made available. We hope to extend the online component of our feature columns with moderated online discussion forums. If you have a suggestion for an online resource you would like to see included, let the feature editor or JCE Online (jceonline@chem.wisc.edu) know about it. JCE Internet Features JCE Internet also has several feature columns: Chemical Education Resource Shelf, Conceptual Questions and Challenge Problems, Equipment Buyers Guide, Hal's Picks, Mathcad
Systoles in discrete dynamical systems
NASA Astrophysics Data System (ADS)
Fernandes, Sara; Grácio, Clara; Ramos, Carlos Correia
2013-01-01
The fruitful relationship between Geometry and Graph Theory has been explored by several authors benefiting also the Theory of discrete dynamical systems seen as Markov chains in graphs. In this work we will further explore the relation between these areas, giving a geometrical interpretation of notions from dynamical systems. In particular, we relate the topological entropy with the systole, here defined in the context of discrete dynamical systems. We show that for continuous interval maps the systole is trivial; however, for the class of interval maps with one discontinuity point the systole acquires relevance from the point of view of the dynamical behavior. Moreover, we define the geodesic length spectrum associated to a Markov interval map and we compute the referred spectrum in several examples.
Dark Energy from Discrete Spacetime
Trout, Aaron D.
2013-01-01
Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies. PMID:24312502
Dark energy from discrete spacetime.
Trout, Aaron D
2013-01-01
Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, [Formula: see text] in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies.
Observability of discretized partial differential equations
NASA Technical Reports Server (NTRS)
Cohn, Stephen E.; Dee, Dick P.
1988-01-01
It is shown that complete observability of the discrete model used to assimilate data from a linear partial differential equation (PDE) system is necessary and sufficient for asymptotic stability of the data assimilation process. The observability theory for discrete systems is reviewed and applied to obtain simple observability tests for discretized constant-coefficient PDEs. Examples are used to show how numerical dispersion can result in discrete dynamics with multiple eigenvalues, thereby detracting from observability.
Homayounfar, Mehran; Zomorodian, Mehdi; Martinez, Christopher J.; Lai, Sai Hin
2015-01-01
So far many optimization models based on Nash Bargaining Theory associated with reservoir operation have been developed. Most of them have aimed to provide practical and efficient solutions for water allocation in order to alleviate conflicts among water users. These models can be discussed from two viewpoints: (i) having a discrete nature; and (ii) working on an annual basis. Although discrete dynamic game models provide appropriate reservoir operator policies, their discretization of variables increases the run time and causes dimensionality problems. In this study, two monthly based non-discrete optimization models based on the Nash Bargaining Solution are developed for a reservoir system. In the first model, based on constrained state formulation, the first and second moments (mean and variance) of the state variable (water level in the reservoir) is calculated. Using moment equations as the constraint, the long-term utility of the reservoir manager and water users are optimized. The second model is a dynamic approach structured based on continuous state Markov decision models. The corresponding solution based on the collocation method is structured for a reservoir system. In this model, the reward function is defined based on the Nash Bargaining Solution. Indeed, it is used to yield equilibrium in every proper sub-game, thereby satisfying the Markov perfect equilibrium. Both approaches are applicable for water allocation in arid and semi-arid regions. A case study was carried out at the Zayandeh-Rud river basin located in central Iran to identify the effectiveness of the presented methods. The results are compared with the results of an annual form of dynamic game, a classical stochastic dynamic programming model (e.g. Bayesian Stochastic Dynamic Programming model, BSDP), and a discrete stochastic dynamic game model (PSDNG). By comparing the results of alternative methods, it is shown that both models are capable of tackling conflict issues in water allocation
Homayounfar, Mehran; Zomorodian, Mehdi; Martinez, Christopher J; Lai, Sai Hin
2015-01-01
So far many optimization models based on Nash Bargaining Theory associated with reservoir operation have been developed. Most of them have aimed to provide practical and efficient solutions for water allocation in order to alleviate conflicts among water users. These models can be discussed from two viewpoints: (i) having a discrete nature; and (ii) working on an annual basis. Although discrete dynamic game models provide appropriate reservoir operator policies, their discretization of variables increases the run time and causes dimensionality problems. In this study, two monthly based non-discrete optimization models based on the Nash Bargaining Solution are developed for a reservoir system. In the first model, based on constrained state formulation, the first and second moments (mean and variance) of the state variable (water level in the reservoir) is calculated. Using moment equations as the constraint, the long-term utility of the reservoir manager and water users are optimized. The second model is a dynamic approach structured based on continuous state Markov decision models. The corresponding solution based on the collocation method is structured for a reservoir system. In this model, the reward function is defined based on the Nash Bargaining Solution. Indeed, it is used to yield equilibrium in every proper sub-game, thereby satisfying the Markov perfect equilibrium. Both approaches are applicable for water allocation in arid and semi-arid regions. A case study was carried out at the Zayandeh-Rud river basin located in central Iran to identify the effectiveness of the presented methods. The results are compared with the results of an annual form of dynamic game, a classical stochastic dynamic programming model (e.g. Bayesian Stochastic Dynamic Programming model, BSDP), and a discrete stochastic dynamic game model (PSDNG). By comparing the results of alternative methods, it is shown that both models are capable of tackling conflict issues in water allocation
A biased filter for linear discrete dynamic systems.
NASA Technical Reports Server (NTRS)
Chang, J. W.; Hoerl, A. E.; Leathrum, J. F.
1972-01-01
A recursive estimator, the ridge filter, was developed for the linear discrete dynamic estimation problem. Theorems were established to show that the ridge filter can be, on the average, closer to the expected value of the system state than the Kalman filter. On the other hand, Kalman filter, on the average, is closer to the instantaneous system state than the ridge filter. The ridge filter has been formulated in such a way that the computational features of the Kalman filter are preserved.
Cascade Reservoirs Floodwater Resources Utilization
NASA Astrophysics Data System (ADS)
Wang, Y.
2015-12-01
A reasonable floodwater resources utilization method is put forward by dynamic controlling of cascade reservoirs flood control limited level in this paper. According to the probability distribution of the beginning time of the first flood and the ending time of the final flood from July to September, the Fuzzy Statistic Analysis was used to divide the main flood season. By fitting the flood season membership functions of each period, the cascade reservoirs flood control limited water level for each period were computed according to the characteristic data of reservoirs. In terms of the benefit maximization and risk minimum principle, the reasonable combination of flood control limited water level of cascade reservoirs was put forward.
Fully analogue photonic reservoir computer.
Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge
2016-03-03
Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers.
Reservoir evaporation in Texas, USA
NASA Astrophysics Data System (ADS)
Wurbs, Ralph A.; Ayala, Rolando A.
2014-03-01
The role of reservoir surface evaporation in river/reservoir water budgets and water management is explored using a modeling system that combines historical natural hydrology with current conditions of water resources development and management. The long-term mean evaporation from the 3415 reservoirs in the Texas water rights permit system is estimated to be 7.53 billion m3/year, which is equivalent to 61% of total agricultural or 126% of total municipal water use in the state during the year 2010. Evaporation varies with the hydrologic conditions governing reservoir surface areas and evaporation rates. Annual statewide total evaporation volumes associated with exceedance probabilities of 75%, 50%, and 25% are 7.07, 7.47, and 7.95 billion m3/year, respectively. Impacts of evaporation are greatest during extended severe droughts that govern water supply capabilities.
Fully analogue photonic reservoir computer
Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge
2016-01-01
Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers. PMID:26935166
Functional wettability in carbonate reservoirs
Brady, Patrick V.; Thyne, Geoffrey
2016-10-11
Oil adsorbs to carbonate reservoirs indirectly through a relatively thick separating water layer, and directly to the surface through a relatively thin intervening water layer. Whereas directly sorbed oil desorbs slowly and incompletely in response to changes in reservoir conditions, indirectly sorbed oil can be rapidly desorbed by changing the chemistry of the separating water layer. The additional recovery might be as much as 30% original oil in place (OOIP) above the ~30% OOIP recovered from carbonates through reservoir depressurization (primary production) and viscous displacement (waterflooding). Electrostatic adhesive forces are the dominant control over carbonate reservoir wettability. A surface complexationmore » model that quantifies electrostatic adhesion accurately predicts oil recovery trends for carbonates. Furthermore, the approach should therefore be useful for estimating initial wettability and designing fluids that improve oil recovery.« less
Functional wettability in carbonate reservoirs
Brady, Patrick V.; Thyne, Geoffrey
2016-10-11
Oil adsorbs to carbonate reservoirs indirectly through a relatively thick separating water layer, and directly to the surface through a relatively thin intervening water layer. Whereas directly sorbed oil desorbs slowly and incompletely in response to changes in reservoir conditions, indirectly sorbed oil can be rapidly desorbed by changing the chemistry of the separating water layer. The additional recovery might be as much as 30% original oil in place (OOIP) above the ~30% OOIP recovered from carbonates through reservoir depressurization (primary production) and viscous displacement (waterflooding). Electrostatic adhesive forces are the dominant control over carbonate reservoir wettability. A surface complexation model that quantifies electrostatic adhesion accurately predicts oil recovery trends for carbonates. Furthermore, the approach should therefore be useful for estimating initial wettability and designing fluids that improve oil recovery.
1. VIEW OF CRUSHING PLANT (FEATURE 19). THE REMAINS OF ...
1. VIEW OF CRUSHING PLANT (FEATURE 19). THE REMAINS OF THE FINE ORE MILL (FEATURE 20) ARE IN THE BACKGROUND ON LEFT. CONCRETE RESERVOIR (FEATURE 22) IS SHOWN AT THE RIGHT EDGE OF PHOTOGRAPH FACING SOUTHWEST. - Copper Canyon Camp of the International Smelting & Refining Company, Crushing Plant, Copper Canyon, Battle Mountain, Lander County, NV
33 CFR 211.81 - Reservoir areas.
Code of Federal Regulations, 2012 CFR
2012-07-01
... McClellan-Kerr Navigation Project in Oklahoma, to Former Owners Authority: Secs. 211.101 to 211.111... to: (a) Fort Gibson Reservoir Area, Oklahoma. (b) Lake Texoma and the Denison Reservoir Area..., Nebraska. (e) Fort Randall Reservoir Area, South Dakota. (f) Garrison Reservoir Area, North Dakota....
33 CFR 211.81 - Reservoir areas.
Code of Federal Regulations, 2011 CFR
2011-07-01
... McClellan-Kerr Navigation Project in Oklahoma, to Former Owners Authority: Secs. 211.101 to 211.111... to: (a) Fort Gibson Reservoir Area, Oklahoma. (b) Lake Texoma and the Denison Reservoir Area..., Nebraska. (e) Fort Randall Reservoir Area, South Dakota. (f) Garrison Reservoir Area, North Dakota....
33 CFR 211.81 - Reservoir areas.
Code of Federal Regulations, 2010 CFR
2010-07-01
... McClellan-Kerr Navigation Project in Oklahoma, to Former Owners Authority: Secs. 211.101 to 211.111... to: (a) Fort Gibson Reservoir Area, Oklahoma. (b) Lake Texoma and the Denison Reservoir Area..., Nebraska. (e) Fort Randall Reservoir Area, South Dakota. (f) Garrison Reservoir Area, North Dakota....
33 CFR 211.81 - Reservoir areas.
Code of Federal Regulations, 2013 CFR
2013-07-01
... McClellan-Kerr Navigation Project in Oklahoma, to Former Owners Authority: Secs. 211.101 to 211.111... to: (a) Fort Gibson Reservoir Area, Oklahoma. (b) Lake Texoma and the Denison Reservoir Area..., Nebraska. (e) Fort Randall Reservoir Area, South Dakota. (f) Garrison Reservoir Area, North Dakota....
49 CFR 393.50 - Reservoirs required.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 49 Transportation 5 2014-10-01 2014-10-01 false Reservoirs required. 393.50 Section 393.50... NECESSARY FOR SAFE OPERATION Brakes § 393.50 Reservoirs required. (a) Reservoir capacity for air-braked... trailers manufactured on or after January 1, 1975, must meet the reservoir requirements of FMVSS No....
Chickamauga reservoir embayment study - 1990
Meinert, D.L.; Butkus, S.R.; McDonough, T.A.
1992-12-01
The objectives of this report are three-fold: (1) assess physical, chemical, and biological conditions in the major embayments of Chickamauga Reservoir; (2) compare water quality and biological conditions of embayments with main river locations; and (3) identify any water quality concerns in the study embayments that may warrant further investigation and/or management actions. Embayments are important areas of reservoirs to be considered when assessments are made to support water quality management plans. In general, embayments, because of their smaller size (water surface areas usually less than 1000 acres), shallower morphometry (average depth usually less than 10 feet), and longer detention times (frequently a month or more), exhibit more extreme responses to pollutant loadings and changes in land use than the main river region of the reservoir. Consequently, embayments are often at greater risk of water quality impairments (e.g. nutrient enrichment, filling and siltation, excessive growths of aquatic plants, algal blooms, low dissolved oxygen concentrations, bacteriological contamination, etc.). Much of the secondary beneficial use of reservoirs occurs in embayments (viz. marinas, recreation areas, parks and beaches, residential development, etc.). Typically embayments comprise less than 20 percent of the surface area of a reservoir, but they often receive 50 percent or more of the water-oriented recreational use of the reservoir. This intensive recreational use creates a potential for adverse use impacts if poor water quality and aquatic conditions exist in an embayment.
SMALL, GEOLOGICALLY COMPLEX RESERVOIRS CAN BENEFIT FROM RESERVOIR SIMULATION
Richard E. Bennett
2002-06-24
The Cascade Sand zone of the Mission-Visco Lease in the Cascade Oil field of Los Angeles County, California, has been under water flood since 1970. Increasing water injection to increase oil production rates was being considered as an opportunity to improve oil recovery. However, a secondary gas cap had formed in the up-dip portion of the reservoir with very low gas cap pressures, creating concern that oil could be displaced into the gas cap resulting in the loss of recoverable oil. Therefore, injecting gas into the gas cap to keep the gas cap pressurized and restrict the influx of oil during water injection was also being considered. Further, it was recognized that the reservoir geology in the gas cap area is very complex with numerous folding and faulting and thus there are potential pressure barriers in several locations throughout the reservoir. With these conditions in mind, there were concerns regarding well to well continuity in the gas cap, which could interfere with the intended repressurization impact. Concerns about the pattern of gas flow from well to well, the possibilities of cycling gas without the desired increased pressure, and the possible loss of oil displaced into the gas cap resulted in the decision to conduct a gas tracer survey in an attempt to better define inter-well communication. Following the gas tracer survey, a reservoir model would be developed to integrate the findings of the gas tracer survey, known geologic and reservoir data, and historic production data. The reservoir model would be used to better define the reservoir characteristics and provide information that could help optimize the waterflood-gas injection project under consideration for efficient water and gas injection management to increase oil production. However, due to inadequate gas sampling procedures in the field and insufficiently developed laboratory analytical techniques, the laboratory was unable to detect the tracer in the gas samples taken. At that point, focus
Forster, C.B.; Nielson, D.L.; Deo, M.
1998-12-01
An exhumed fractured reservoir located near Alligator Ridge in central Nevada provides the basis for developing and testing different approaches for simulating fractured petroleum reservoirs. The fractured analog reservoir comprises a 90 m thickness of silty limestone and shaly interbeds within the Devonian Pilot Shale. A period of regional compression followed by ongoing basin and range extension has created faults and fractures that, in tern, have controlled the migration of both oil and gold ore-forming fluids. Open pit gold mines provide access for observing oil seepage, collecting the detailed fracture data needed to map variations in fracture intensity near faults, build discrete fracture network models and create equivalent permeability structures. Fault trace patterns mapped at the ground surface provide a foundation for creating synthetic fault trace maps using a stochastic procedure conditioned by the outcrop data. Conventional simulations of petroleum production from a 900 by 900 m sub-domain within the reservoir analog illustrate the possible influence of faults and fractures on production. The consequences of incorporating the impact of different stress states (e.g., extension, compression or lithostatic) are also explored. Simulating multiphase fluid flow using a discrete fracture, finite element simulator illustrates how faults acting as conduits might be poorly represented by the upscaling procedures used to assign equivalent permeability values within reservoir models. The parallelized reservoir simulators developed during this project provide a vehicle to evaluate when it might be necessary to incorporate very fine scale grid networks in conventional reservoir simulators or to use finely gridded discrete fracture reservoir simulators.
Petroleum reservoir data for testing simulation models
Lloyd, J.M.; Harrison, W.
1980-09-01
This report consists of reservoir pressure and production data for 25 petroleum reservoirs. Included are 5 data sets for single-phase (liquid) reservoirs, 1 data set for a single-phase (liquid) reservoir with pressure maintenance, 13 data sets for two-phase (liquid/gas) reservoirs and 6 for two-phase reservoirs with pressure maintenance. Also given are ancillary data for each reservoir that could be of value in the development and validation of simulation models. A bibliography is included that lists the publications from which the data were obtained.
Reservoir characterization of Pennsylvanian Sandstone Reservoirs. Annual report
Kelkar, M.
1992-09-01
This annual report describes the progress during the second year of a project on Reservoir Characterization of Pennsylvanian Sandstone Reservoirs. The report is divided into three sections: (i) reservoir description and scale-up procedures; (ii) outcrop investigation; (iii) in-fill drilling potential. The first section describes the methods by which a reservoir can be characterized, can be described in three dimensions, and can be scaled up with respect to its properties, appropriate for simulation purposes. The second section describes the progress on investigation of an outcrop. The outcrop is an analog of Bartlesville Sandstone. We have drilled ten wells behind the outcrop and collected extensive log and core data. The cores have been slabbed, photographed and the several plugs have been taken. In addition, minipermeameter is used to measure permeabilities on the core surface at six inch intervals. The plugs have been analyzed for the permeability and porosity values. The variations in property values will be tied to the geological descriptions as well as the subsurface data collected from the Glen Pool field. The third section discusses the application of geostatistical techniques to infer in-fill well locations. The geostatistical technique used is the simulated annealing technique because of its flexibility. One of the important reservoir data is the production data. Use of production data will allow us to define the reservoir continuities, which may in turn, determine the in-fill well locations. The proposed technique allows us to incorporate some of the production data as constraints in the reservoir descriptions. The technique has been validated by comparing the results with numerical simulations.
Multipulses in discrete Hamiltonian nonlinear systems.
Kevrekidis, P G
2001-08-01
In this work, the behavior of multipulses in discrete Hamiltonian nonlinear systems is investigated. The discrete nonlinear Schrödinger equation is used as the benchmark system for this study. A singular perturbation methodology as well as a variational approach are implemented in order to identify the dominant factors in the discrete problem. The results of the two methodologies are shown to coincide in assessing the interplay of discreteness and exponential tail-tail pulse interaction. They also allow one to understand why, contrary to what is believed for their continuum siblings, discrete systems can sustain (static) multipulse configurations, a conclusion that is subsequently verified by numerical experiment.
On equivalence of discrete-discrete and continuum-discrete design sensitivity analysis
NASA Technical Reports Server (NTRS)
Choi, Kyung K.; Twu, Sung-Ling
1989-01-01
Developments in design sensitivity analysis (DSA) method have been made using two fundamentally different approaches as shown. In the first approach, a discretized structural finite element model is used to carry out DSA. There are three different methods in the discrete DSA approach: finite difference, semi-analytical, and analytical methods. The finite difference method is a popular one due to its simplicity, but a serious shortcoming of the method is the uncertainty in the choice of a perturbation step size of design variables. In the semi-analytical method, the derivatives of stiffness matrix is computed by finite differences, whereas in the analytical method, the derivatives are obtained analytically. For the shape design variable, computation of analytical derivative of stiffness matrix is quite costly. Because of this, the semi-analytical method is a popular choice in discrete shape DSA approach. However, recently, Barthelemy and Haftka presented that the semi-analytical method can have serious accuracy problems for shape design variables in structures modeled by beam, plate, truss, frame, and solid elements. They found that accuracy problems occur even for a simple cantilever beam. In the second approach, a continuum model of the structure is used to carry out DSA.
Data mining and well logging interpretation: application to a conglomerate reservoir
NASA Astrophysics Data System (ADS)
Shi, Ning; Li, Hong-Qi; Luo, Wei-Ping
2015-06-01
Data mining is the process of extracting implicit but potentially useful information from incomplete, noisy, and fuzzy data. Data mining offers excellent nonlinear modeling and self-organized learning, and it can play a vital role in the interpretation of well logging data of complex reservoirs. We used data mining to identify the lithologies in a complex reservoir. The reservoir lithologies served as the classification task target and were identified using feature extraction, feature selection, and modeling of data streams. We used independent component analysis to extract information from well curves. We then used the branch-and-bound algorithm to look for the optimal feature subsets and eliminate redundant information. Finally, we used the C5.0 decision-tree algorithm to set up disaggregated models of the well logging curves. The modeling and actual logging data were in good agreement, showing the usefulness of data mining methods in complex reservoirs.
Long-time behavior of a finite volume discretization for a fourth order diffusion equation
NASA Astrophysics Data System (ADS)
Maas, Jan; Matthes, Daniel
2016-07-01
We consider a non-standard finite-volume discretization of a strongly non-linear fourth order diffusion equation on the d-dimensional cube, for arbitrary d≥slant 1 . The scheme preserves two important structural properties of the equation: the first is the interpretation as a gradient flow in a mass transportation metric, and the second is an intimate relation to a linear Fokker-Planck equation. Thanks to these structural properties, the scheme possesses two discrete Lyapunov functionals. These functionals approximate the entropy and the Fisher information, respectively, and their dissipation rates converge to the optimal ones in the discrete-to-continuous limit. Using the dissipation, we derive estimates on the long-time asymptotics of the discrete solutions. Finally, we present results from numerical experiments which indicate that our discretization is able to capture significant features of the complex original dynamics, even with a rather coarse spatial resolution.
Invariants of broken discrete symmetries.
Kalozoumis, P A; Morfonios, C; Diakonos, F K; Schmelcher, P
2014-08-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
Invariants of Broken Discrete Symmetries
NASA Astrophysics Data System (ADS)
Kalozoumis, P. A.; Morfonios, C.; Diakonos, F. K.; Schmelcher, P.
2014-08-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
The Ogden Valley artesian reservoir
Thomas, H.E.
1945-01-01
Ogden Valley, in Weber County, Utah, contains an artesian reservoir from which the city of Ogden obtains all except a small part of its municipal water supply. A detailed investigation of the ground-water resources of Ogden Valley, and particularly of this artesian reservoir, was made by the Geological Survey, United States Department of the Interior, in cooperation with the city of Ogden between 1932 and 1934, and the results of this investigation have been reported by Leggette and Taylor.1 The present paper, which might be termed a sequel to that report, is based on data collected during those years, augmented by records that have been obtained (1935-1940) by the Geological Survey as part of a State-wide project in cooperation with the Utah State Engineer. The conclusions drawn from the study of these records and presented in detail in the following pages are as follows: (1) The artesian reservoir is filled to capacity nearly every year during the spring run-off from melting snow; (2) after the annual freshet, the recharge to the reservoir is insufficient to balance the discharge from artesian wells, which ordinarily is at a maximum during the summer; the reservoir is depleted and is not filled again until the following spring; (3) during the periods when the artesian reservoir is not full the rate of recharge is more or less proportional to the inflow to the valley by streams, except that rain on the recharge area may be of sufficient intensity to contribute some water by infiltration and deep penetration; and (4) the artesian reservoir thus serves to store water that would otherwise be lost to Great Salt Lake in the excess spring overflow, and available records indicate that water used by increased draft from wells would be replenished in normal years by increased recharge during the spring freshet.
Gu, Qing; Deng, Jinsong; Wang, Ke; Lin, Yi; Li, Jun; Gan, Muye; Ma, Ligang; Hong, Yang
2014-06-10
Various reservoirs have been serving as the most important drinking water sources in Zhejiang Province, China, due to the uneven distribution of precipitation and severe river pollution. Unfortunately, rapid urbanization and industrialization have been continuously challenging the water quality of the drinking-water reservoirs. The identification and assessment of potential impacts is indispensable in water resource management and protection. This study investigates the drinking water reservoirs in Zhejiang Province to better understand the potential impact on water quality. Altogether seventy-three typical drinking reservoirs in Zhejiang Province encompassing various water storage levels were selected and evaluated. Using fifty-two reservoirs as training samples, the classification and regression tree (CART) method and sixteen comprehensive variables, including six sub-sets (land use, population, socio-economy, geographical features, inherent characteristics, and climate), were adopted to establish a decision-making model for identifying and assessing their potential impacts on drinking-water quality. The water quality class of the remaining twenty-one reservoirs was then predicted and tested based on the decision-making model, resulting in a water quality class attribution accuracy of 81.0%. Based on the decision rules and quantitative importance of the independent variables, industrial emissions was identified as the most important factor influencing the water quality of reservoirs; land use and human habitation also had a substantial impact on water quality. The results of this study provide insights into the factors impacting the water quality of reservoirs as well as basic information for protecting reservoir water resources.
Volatile reservoirs below the surface of the Elysium region of Mars: Geomorphic evidence
NASA Technical Reports Server (NTRS)
Christiansen, Eric H.; Hopler, Jennifer A.
1987-01-01
The Elysium volcanic province contains a variety of geomorphic evidence for the existence of large volatile reservoirs of subsurface volatiles. Study of these landforms yields insight into the distribution and size of these reservoirs and how they interact with the surface environment and will ultimately place constraints on the geometry, constitution, origin, time of formation, and temporal evolution of these important components of the Martian crust. Three principal types of landforms appear to be related to subsurface volatile reservoirs in the Elysium region of Mars: small outflow channels; large lahars; and vast expanses of knobby terranes around the margins of the Elysium dome. The evidence provided by these landforms is internally consistent with the presence of a large relatively shallow volatile reservoir in the Elysium region. If the geologic features described are reliable indicators of subsurface volatiles, they imply that: volatile reservoirs lie relatively close to the surface and underlie millions of sq km in this region; there is no apparent latitudinal variation in the depth or thickness of the volatile reservoirs; the precursors of the knobby terranes are or were important volatile reservoirs; volatiles may be lost in a variety of ways from these reservoirs; and volatiles were incorporated in an easily eroded surficial deposit in the middle history of Mars. The ultimate origin of water in this reservoir is uncertain. A model to explain the preferential entrapment of volatiles into the region's surface materials may be required.
An adaptive nonlinear solution scheme for reservoir simulation
Lett, G.S.
1996-12-31
Numerical reservoir simulation involves solving large, nonlinear systems of PDE with strongly discontinuous coefficients. Because of the large demands on computer memory and CPU, most users must perform simulations on very coarse grids. The average properties of the fluids and rocks must be estimated on these grids. These coarse grid {open_quotes}effective{close_quotes} properties are costly to determine, and risky to use, since their optimal values depend on the fluid flow being simulated. Thus, they must be found by trial-and-error techniques, and the more coarse the grid, the poorer the results. This paper describes a numerical reservoir simulator which accepts fine scale properties and automatically generates multiple levels of coarse grid rock and fluid properties. The fine grid properties and the coarse grid simulation results are used to estimate discretization errors with multilevel error expansions. These expansions are local, and identify areas requiring local grid refinement. These refinements are added adoptively by the simulator, and the resulting composite grid equations are solved by a nonlinear Fast Adaptive Composite (FAC) Grid method, with a damped Newton algorithm being used on each local grid. The nonsymmetric linear system of equations resulting from Newton`s method are in turn solved by a preconditioned Conjugate Gradients-like algorithm. The scheme is demonstrated by performing fine and coarse grid simulations of several multiphase reservoirs from around the world.
A discrete momentum-conserving explicit algorithm for rigid body dynamics analysis
NASA Technical Reports Server (NTRS)
Park, K. C.; Chiou, J. C.
1993-01-01
A discrete momentum-conserving explicit time integration is presented. The accurate feature and simplicity of the present algorithm are realized by a mid-point implicit formula for integrating the Euler parameters and a second-order discrete momentum-conserving form of the central difference algorithm, respectively. The accuracy and robustness of the algorithm is demonstrated by example problems which exhibit large overall rigid motions under holonomic constraints.
A discrete momentum-conserving explicit algorithm for multibody dynamics analysis
NASA Technical Reports Server (NTRS)
Park, K. C.; Chiou, J. C.
1992-01-01
A discrete momentum-conserving, explicit time integration is presented. The accurate feature and simplicity of the present algorithm are realized by a mid-point implicit formula for integrating the Euler parameters and a second-order discrete momentum-conserving form of the central difference algorithm, respectively. The accuracy and robustness of the algorithm is demonstrated by example problems which exhibit large overall rigid motions under holonomic constraints.
A vapor-dominated reservoir exceeding 600{degrees}F at the Geysers, Sonoma County, California
Walters, M.A.; Sternfeld, J.N.; Haizlip, J.R.; Drenick, A.F.; Combs, Jim
1988-01-01
A high-temperature vapor-dominated reservoir underlies a portion of the Northwest Geysers area, Sonoma County, California. The high-temperature reservoir (HTR) is defined by flowing fluid temperatures exceeding 500º F, rock temperatures apparently exceeding 600º F and steam enthalpies of about 1320 BTU/lb. Steam from existing wells drilled in the Northwest Geysers is produced from both a “typical” Geysers reservoir and the HTR. In all cases, the HTR is in the lower portion of the wells and is overlain by a “typical” Geysers reservoir. Depth to the high-temperature reservoir is relatively uniform at about -5900 ft subsea. There are no identified lithologic or mineralogic conditions that separate the HTR from the “typical” reservoir, although the two reservoirs are vertically distinct and can be located in most wells to within about 200 ft by the use of downhole temperature-depth measurements. Gas concentrations in steam from the HTR are higher (6 to 9 wt %) than from the “typical” Geysers reservoir (0.85 to 2.6 wt %). Steam from the HTR is enriched in chloride and the heavy isotopes of water relative to the “typical” reservoir. Available static and dynamic measurements show pressures are subhydrostatic in both reservoirs with no anomalous differences between the two: the HTR pressure being near 520 psia at sea level datum. The small observed differences in pressure between the reservoirs appear to vary along a steam density gradient. It is postulated that the Northwest Geysers area evolved more slowly toward vapor-dominated conditions than other parts of The Geysers field because of its poor connection with the surface. In this paper, a model is presented in which the boundary between the HTR and “typical” reservoir is a thermodynamic feature only, resulting from recent deep venting of a liquid-dominated system in which conduction is still an important component of heat transfer.
Supervised Discrete Hashing With Relaxation.
Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu
2016-12-29
Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.
Entwinement in discretely gauged theories
NASA Astrophysics Data System (ADS)
Balasubramanian, V.; Bernamonti, A.; Craps, B.; De Jonckheere, T.; Galli, F.
2016-12-01
We develop the notion of "entwinement" to characterize the amount of quantum entanglement between internal, discretely gauged degrees of freedom in a quantum field theory. This concept originated in the program of reconstructing spacetime from entanglement in holographic duality. We define entwinement formally in terms of a novel replica method which uses twist operators charged in a representation of the discrete gauge group. In terms of these twist operators we define a non-local, gauge-invariant object whose expectation value computes entwinement in a standard replica limit. We apply our method to the computation of entwinement in symmetric orbifold conformal field theories in 1+1 dimensions, which have an S N gauging. Such a theory appears in the weak coupling limit of the D1-D5 string theory which is dual to AdS3 at strong coupling. In this context, we show how certain kinds of entwinement measure the lengths, in units of the AdS scale, of non-minimal geodesics present in certain excited states of the system which are gravitationally described as conical defects and the M = 0 BTZ black hole. The possible types of entwinement that can be computed define a very large new class of quantities characterizing the fine structure of quantum wavefunctions.
Discreteness effects in population dynamics
NASA Astrophysics Data System (ADS)
Guevara Hidalgo, Esteban; Lecomte, Vivien
2016-05-01
We analyse numerically the effects of small population size in the initial transient regime of a simple example population dynamics. These effects play an important role for the numerical determination of large deviation functions of additive observables for stochastic processes. A method commonly used in order to determine such functions is the so-called cloning algorithm which in its non-constant population version essentially reduces to the determination of the growth rate of a population, averaged over many realizations of the dynamics. However, the averaging of populations is highly dependent not only on the number of realizations of the population dynamics, and on the initial population size but also on the cut-off time (or population) considered to stop their numerical evolution. This may result in an over-influence of discreteness effects at initial times, caused by small population size. We overcome these effects by introducing a (realization-dependent) time delay in the evolution of populations, additional to the discarding of the initial transient regime of the population growth where these discreteness effects are strong. We show that the improvement in the estimation of the large deviation function comes precisely from these two main contributions.
Lucia, F.J.
1997-06-01
Reservoir performance of the South Cowden Grayburg field suggests that only 21 percent of the original oil in place has been recovered. The purpose of this study is to construct a realistic reservoir model to be used to predict the location of the remaining mobile oil. Construction of reservoir models for fluid-flow simulation of carbonate reservoirs is difficult because they typically have complicated and unpredictable permeability patterns. Much of the difficulty results from the degree to which diagenetic overprinting masks depositional textures and patterns. For example, the task of constructing a reservoir model of a limestone reservoir that has undergone only cementation and compaction is easier than constructing a model of a karsted reservoir that has undergone cavern formation and collapse as well as cementation and compaction. The Permian-age carbonate-ramp reservoirs in the Permian Basin, West Texas and New Mexico, are typically anhydritic dolomitized limestone. Because the dolomitization occurred soon after deposition, depositional fabrics and patterns are often retained, and a reservoir model can be constructed using depositional concepts. Recent studies of the San Andres outcrop in the Guadalupe Mountains and the Seminole San Andres reservoir in the Permian Basin illustrate how depositional fabrics and patterns can be used to construct a reservoir model when depositional features are retained.
Monterey fractured reservoir, Santa Barbara Channel, California
Belfield, W.C.; Helwig, J.; La Pointe, P.R.; Dahleen, W.K.
1983-03-01
The South Elwood field in the Santa Barbara Channel is a faulted anticline with cumulative production of 14.5 million bbl from the Monterey Formation as of September 1, 1982. The distributions of pressure, flow rates, and oil-water contacts and the low average matrix permeability of 0.2 md require a fractured reservoir. Core and outcrop studies show a dominant fracture set characterized by vertical, lithologically controlled fractures oriented across strike, and breccias controlled by lithology and structure. Generally, the fracture intensity is unaffected by structural position or bed curvature but is controlled by lithology and bed thickness. Other varieties of fracturing in the Monterey are related to a protracted history of diagenesis, deformation, and fluid injection. Three types of tar-bearing breccias occur in the Monterey Formation: stratigraphic breccia, coalescent-fracture breccia, and fault-related breccia. Formation of breccias probably involves high pore pressures. Because of their polygenetic origin, breccia masses have diverse orientations paralleling bedding or fracture/fault systems. In conclusions, fracturing and brecciation of the Monterey Formation reflect the interplay between processes of diagenesis, deformation, and fluid dynamics. The most important features of the reservoir in the area of the present study are: (1) vertical fractures oriented normal to the structural trends and inferred to be favorably oriented (to remain open) with respect to the regional minimum horizontal stress; and (2) breccias that are both stratigraphically and structurally controlled and inferred to be related to the interaction of rock stress and fluid dynamics.
1998-01-01
Infill drilling if wells on a uniform spacing without regard to reservoir performance and characterization foes not optimize reservoir development because it fails to account for the complex nature of reservoir heterogeneities present in many low permeability reservoirs, and carbonate reservoirs in particular. New and emerging technologies, such as geostatistical modeling, rigorous decline curve analysis, reservoir rock typing, and special core analysis can be used to develop a 3-D simulation model for prediction of infill locations.
B. Pregger; D. Davies; D. Moore; G. Freeman; J. Callard; J.W. Nevans; L. Doublet; R. Vessell; T. Blasingame
1997-08-31
Infill drilling if wells on a uniform spacing without regard to reservoir performance and characterization foes not optimize reservoir development because it fails to account for the complex nature of reservoir heterogeneities present in many low permeability reservoirs, and carbonate reservoirs in particular. New and emerging technologies, such as geostatistical modeling, rigorous decline curve analysis, reservoir rock typing, and special core analysis can be used to develop a 3-D simulation model for prediction of infill locations.
1998-03-12
Infill drilling if wells on a uniform spacing without regard to reservoir performance and characterization foes not optimize reservoir development because it fails to account for the complex nature of reservoir heterogeneities present in many low permeability reservoirs, and carbonate reservoirs in particular. New and emerging technologies, such as geostatistical modeling, rigorous decline curve analysis, reservoir rock typing, and special core analysis can be used to develop a 3-D simulation model for prediction of infill locations.
P. K. Pande
1998-10-29
Initial drilling of wells on a uniform spacing, without regard to reservoir performance and characterization, must become a process of the past. Such efforts do not optimize reservoir development as they fail to account for the complex nature of reservoir heterogeneities present in many low permeability reservoirs, and carbonate reservoirs in particular. These reservoirs are typically characterized by: o Large, discontinuous pay intervals o Vertical and lateral changes in reservoir properties o Low reservoir energy o High residual oil saturation o Low recovery efficiency
Service as a Feature of Quality Education.
ERIC Educational Resources Information Center
Drake, Barry
2001-01-01
Suggests ways in which service-learning programs can be included in middle school curricula and describes two such projects. States that a meaningful evaluation of a school's service program is only possible if a number of discrete, observable features of success can be identified that afford the opportunity for objective measurement. (NB)
Ideal shrinking and expansion of discrete sequences
NASA Technical Reports Server (NTRS)
Watson, Andrew B.
1986-01-01
Ideal methods are described for shrinking or expanding a discrete sequence, image, or image sequence. The methods are ideal in the sense that they preserve the frequency spectrum of the input up to the Nyquist limit of the input or output, whichever is smaller. Fast implementations that make use of the discrete Fourier transform or the discrete Hartley transform are described. The techniques lead to a new multiresolution image pyramid.
Shear-slip analysis in multiphase fluid-flow reservoir engineeringap plications using TOUGH-FLAC
Rutqvist, Jonny; Birkholzer, Jens; Cappa, Frederic; Oldenburg,Curt; Tsang, Chin-Fu
2006-01-15
This paper describes and demonstrates the use of the coupledTOUGH-FLAC simulator for geomechanical shear-slip (failure) analysis inmultiphase fluid-flow reservoir-engineering applications. Two approachesfor analyzing shear-slip are described, one using continuum stress-strainanalysis and another using discrete fault analysis. The use of shear-slipanalysis in TOUGH-FLAC is demonstrated on application examples related toCO2 sequestration and geothermal energy extraction. In the case of CO2sequestration, the shear-slip analysis is used to evaluate maximumsustainable CO2-injection pressure under increasing reservoir pressure,whereas in the case of geothermal energy extraction, the shear-slipanalysis is used to study induced seismicity during steam productionunder decreasing reservoir pressure and temperature.
ERIC Educational Resources Information Center
Kelly, Debbie M.; Bischof, Walter F.
2008-01-01
We investigated how human adults orient in enclosed virtual environments, when discrete landmark information is not available and participants have to rely on geometric and featural information on the environmental surfaces. In contrast to earlier studies, where, for women, the featural information from discrete landmarks overshadowed the encoding…
A discrete event method for wave simulation
Nutaro, James J
2006-01-01
This article describes a discrete event interpretation of the finite difference time domain (FDTD) and digital wave guide network (DWN) wave simulation schemes. The discrete event method is formalized using the discrete event system specification (DEVS). The scheme is shown to have errors that are proportional to the resolution of the spatial grid. A numerical example demonstrates the relative efficiency of the scheme with respect to FDTD and DWN schemes. The potential for the discrete event scheme to reduce numerical dispersion and attenuation errors is discussed.
Discrete gauge symmetry in continuum theories
Krauss, L.M.; Wilczek, F.
1989-03-13
We point out that local symmetries can masquerade as discrete global symmetries to an observer equipped with only low-energy probes. The existence of the underlying local gauge invariance can, however, result in observable Aharonov-Bohm-type effects. Black holes can therefore carry discrete gauge charges: a form of nonclassical ''hair.'' Neither black-hole evaporation, wormholes, nor anything else can violate discrete gauge symmetries. In supersymmetric unified theories such discrete symmetries can forbid proton-decay amplitudes that might otherwise be catastrophic.
Scalar discrete nonlinear multipoint boundary value problems
NASA Astrophysics Data System (ADS)
Rodriguez, Jesus; Taylor, Padraic
2007-06-01
In this paper we provide sufficient conditions for the existence of solutions to scalar discrete nonlinear multipoint boundary value problems. By allowing more general boundary conditions and by imposing less restrictions on the nonlinearities, we obtain results that extend previous work in the area of discrete boundary value problems [Debra L. Etheridge, Jesus Rodriguez, Periodic solutions of nonlinear discrete-time systems, Appl. Anal. 62 (1996) 119-137; Debra L. Etheridge, Jesus Rodriguez, Scalar discrete nonlinear two-point boundary value problems, J. Difference Equ. Appl. 4 (1998) 127-144].
Discrete wave mechanics: An introduction
Wall, Frederick T.
1986-01-01
Discrete wave mechanics is formulated for particles in one-dimensional systems by use of a simple finite difference equation. The solutions involve wave vectors (instead of wave functions) as well as a newly defined “wave vector energy.” In the limit, as c → ∞, the treatment reduces to that of Schrödinger's wave mechanics. Specific calculations are made for completely free particles as well as for particles confined to a one-dimensional box. The results exhibit a striking compatibility with relativistic considerations. The wave vectors show properties that can be identified with particles and anti-particles—each possess identical probability distributions with energies that add up to zero. PMID:16593732
Discrete wave mechanics: Multidimensional systems
Wall, Frederick T.
1987-01-01
Discrete wave mechanics is pursued further by extending the one-dimensional treatment to two (or more) dimensions in the light of explicit momentum considerations. Cognizance is taken of the effect of particle motion on mass and hence on the interactions between components of motion in different directions. The overall energy parameter turns out to be a product instead of a sum of parameters identified with each of several orthogonal axes. Accordingly, the separation of variables is most directly accomplished by factoring the principal energy parameter in conjunction with factoring the wave vector expression itself. Wave vector energies, on the other hand, remain additive. Finally, group velocity components are discussed for higher-dimensional systems. PMID:16593833
Discrete modelling of drapery systems
NASA Astrophysics Data System (ADS)
Thoeni, Klaus; Giacomini, Anna
2016-04-01
Drapery systems are an efficient and cost-effective measure in preventing and controlling rockfall hazards on rock slopes. The simplest form consists of a row of ground anchors along the top of the slope connected to a horizontal support cable from which a wire mesh is suspended down the face of the slope. Such systems are generally referred to as simple or unsecured draperies (Badger and Duffy 2012). Variations such as secured draperies, where a pattern of ground anchors is incorporated within the field of the mesh, and hybrid systems, where the upper part of an unsecured drapery is elevated to intercept rockfalls originating upslope of the installation, are becoming more and more popular. This work presents a discrete element framework for simulation of unsecured drapery systems and its variations. The numerical model is based on the classical discrete element method (DEM) and implemented into the open-source framework YADE (Šmilauer et al., 2010). The model takes all relevant interactions between block, drapery and slope into account (Thoeni et al., 2014) and was calibrated and validated based on full-scale experiments (Giacomini et al., 2012).The block is modelled as a rigid clump made of spherical particles which allows any shape to be approximated. The drapery is represented by a set of spherical particle with remote interactions. The behaviour of the remote interactions is governed by the constitutive behaviour of the wire and generally corresponds to a piecewise linear stress-strain relation (Thoeni et al., 2013). The same concept is used to model wire ropes. The rock slope is represented by rigid triangular elements where material properties (e.g., normal coefficient of restitution, friction angle) are assigned to each triangle. The capabilities of the developed model to simulate drapery systems and estimate the residual hazard involved with such systems is shown. References Badger, T.C., Duffy, J.D. (2012) Drapery systems. In: Turner, A.K., Schuster R
MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA
Albert C. Reynolds; Dean S. Oliver; Fengjun Zhang; Yannong Dong; Jan Arild Skjervheim; Ning Liu
2003-01-01
Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. But while the volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade, it is not yet possible to make use of all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. The goal of this project is to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management. Facies (defined here as regions of relatively uniform petrophysical properties) are common features of all reservoirs. Because the flow properties of the various facies can vary greatly, knowledge of the location of facies boundaries is of utmost importance for the prediction of reservoir performance and for the optimization of reservoir management. When the boundaries between facies are fairly well known, but flow properties are poorly known, the average properties for all facies can be determined using traditional techniques. Traditional history matching honors dynamic data by adjusting petrophysical properties in large areas, but in the process of adjusting the reservoir model ignores the static data and often results in implausible reservoir
New discrete element models for elastoplastic problems
NASA Astrophysics Data System (ADS)
Cheng, Ming; Liu, Weifu; Liu, Kaixin
2009-10-01
The discrete element method (DEM) has attractive features for problems with severe damages, but lack of theoretical basis for continua behavior especially for nonlinear behavior has seriously restricted its application. The present study proposes a new approach to developing the DEM as a general and robust technique for modeling the elastoplastic behavior of solid materials. New types of connective links between elements are proposed, the inter-element parameters are theoretically determined based on the principle of energy equivalence and a yield criterion and a flow rule for DEM are given for describing nonlinear behavior of materials. Moreover, a numerical scheme, which can be applied to modeling the behavior of a continuum as well as the transformation from a continuum to a discontinuum, is obtained by introducing a fracture criterion and a contact model into the DEM. The elastoplastic stress wave propagations and the tensile failure process of a steel plate are simulated, and the numerical results agree well with those obtained from the finite element method (FEM) and corresponding experiment, and thus the accuracy and efficiency of the DEM scheme are demonstrated.
Discrete solitons and vortices on anisotropic lattices.
Kevrekidis, P G; Frantzeskakis, D J; Carretero-González, R; Malomed, B A; Bishop, A R
2005-10-01
We consider the effects of anisotropy on solitons of various types in two-dimensional nonlinear lattices, using the discrete nonlinear Schrödinger equation as a paradigm model. For fundamental solitons, we develop a variational approximation that predicts that broad quasicontinuum solitons are unstable, while their strongly anisotropic counterparts are stable. By means of numerical methods, it is found that, in the general case, the fundamental solitons and simplest on-site-centered vortex solitons ("vortex crosses") feature enhanced or reduced stability areas, depending on the strength of the anisotropy. More surprising is the effect of anisotropy on the so-called "super-symmetric" intersite-centered vortices ("vortex squares"), with the topological charge equal to the square's size : we predict in an analytical form by means of the Lyapunov-Schmidt theory, and confirm by numerical results, that arbitrarily weak anisotropy results in dramatic changes in the stability and dynamics in comparison with the degenerate, in this case, isotropic, limit.
Simulating Electrophoresis with Discrete Charge and Drag
NASA Astrophysics Data System (ADS)
Mowitz, Aaron J.; Witten, Thomas A.
A charged asymmetric rigid cluster of colloidal particles in saline solution can respond in exotic ways to an electric field: it may spin or move transversely. These distinctive motions arise from the drag force of the neutralizing countercharge surrounding the cluster. Because of this drag, calculating the motion of arbitrary asymmetric objects with nonuniform charge is impractical by conventional methods. Here we present a new method of simulating electrophoresis, in which we replace the continuous object and the surrounding countercharge with discrete point-draggers, called Stokeslets. The balance of forces imposes a linear, self-consistent relation among the drag and Coulomb forces on the Stokeslets, which allows us to easily determine the object's motion via matrix inversion. By explicitly enforcing charge+countercharge neutrality, the simulation recovers the distinctive features of electrophoretic motion to few-percent accuracy using as few as 1000 Stokeslets. In particular, for uniformly charged objects, we observe the characteristic Smoluchowski independence of mobility on object size and shape. We then discuss electrophoretic motion of asymmetric objects, where our simulation method is particularly advantageous. This work is supported by a Grant from the US-Israel Binational Science Foundation.
Quantification of geologic descriptions for reservoir characterization in carbonate reservoirs
Lucia, F.J.; Vander Stoep, G.W. )
1990-05-01
Recognition that a large volume of oil remains in carbonate reservoirs at the end of primary depletion and waterflooding has prompted the reevaluation of the reserve-growth potential of many existing carbonate reservoirs. Types of numerical data required include porosity, absolute permeability, relative permeability, fluid saturation, and capillary pressure, all of which are related to the size and distribution of pore space. Rock fabrics control the size and distribution of pore space and define facies that best characterize carbonate reservoirs. Thus, the link between facies descriptions and numerical engineering data is the relationship between pore-size distribution and present carbonate rock fabric. The most effective way to convert facies descriptions into engineering parameters is by considering three basic rock-fabric categories. The first category is interparticle pore space (both intergranular and intercrystalline pore types) with pore-size distribution controlled primarily by the size and shape of grains or crystals. Grain or crystal size is the key geologic measurement and, along with porosity, provides the basis for converting geologic descriptions into values for permeability, saturation, and capillarity. The second category is separate-vug pore space, such as moldic or intraparticle pore space. Separate-vug pore space adds porosity but little permeability to the reservoir rock. The contribution to saturation and capillarity depends upon the size of the separate-vug pore space. For example, moldic separate vugs will be saturated with oil, whereas microporous grains will be saturated with water. The third category is touching-vug pore space, which is vuggy pore space that is interconnected on a reservoir scale. The engineering parameters for this category are related to three diagenetic and tectonic factors.
An efficient permeability scaling-up technique applied to the discretized flow equations
Urgelli, D.; Ding, Yu
1997-08-01
Grid-block permeability scaling-up for numerical reservoir simulations has been discussed for a long time in the literature. It is now recognized that a full permeability tensor is needed to get an accurate reservoir description at large scale. However, two major difficulties are encountered: (1) grid-block permeability cannot be properly defined because it depends on boundary conditions; (2) discretization of flow equations with a full permeability tensor is not straightforward and little work has been done on this subject. In this paper, we propose a new method, which allows us to get around both difficulties. As the two major problems are closely related, a global approach will preserve the accuracy. So, in the proposed method, the permeability up-scaling technique is integrated in the discretized numerical scheme for flow simulation. The permeability is scaled-up via the transmissibility term, in accordance with the fluid flow calculation in the numerical scheme. A finite-volume scheme is particularly studied, and the transmissibility scaling-up technique for this scheme is presented. Some numerical examples are tested for flow simulation. This new method is compared with some published numerical schemes for full permeability tensor discretization where the full permeability tensor is scaled-up through various techniques. Comparing the results with fine grid simulations shows that the new method is more accurate and more efficient.
NASA Astrophysics Data System (ADS)
Ryerson, F. J.; Ezzedine, S. M.; Glascoe, L. G.; Antoun, T. H.
2011-12-01
Fractures and fracture networks are the principle pathways for migration of water, heat and mass in enhanced geothermal systems, oil and gas reservoirs, CO2 leakage from saline aquifers, and radioactive and toxic industrial wastes from underground storage repositories. A major issue to overcome when characterizing a fractured reservoir is that of data limitation due to accessibility and affordability. Moreover, the ability to map discontinuities in the rock with available geological and geophysical tools tends to decrease particularly as the scale of the discontinuity goes down. Data collected are often reduced to probability distribution functions for predictive modeling and simulation in a stochastic framework such as stochastic discrete fracture network. Stochastic discrete fracture network models enable probabilistic assessment of flow, transport and geomechanical phenomena that are not adequately captured using continuum models. Despite the fundamental uncertainties inherited within the probabilistic reduction of the sparse data collected, very little work has been conducted on quantifying uncertainty on the reduced probabilistic distribution functions. In the current study, we investigate the impact of parameter uncertainties of the distribution functions that characterize discrete fracture networks on the flow, heat and mass transport and geomechanics. Numerical results of first, second and third moments, normalized to a base case scenario, are presented and compared to theoretical results extended from percolation theory. (Prepared by LLNL under Contract DE-AC52-07NA27344)
Unconventional Reservoirs: Ideas to Commercialization
NASA Astrophysics Data System (ADS)
Tinker, S. W.
2015-12-01
There is no shortage of coal, oil, and natural gas in the world. What are sometimes in short supply are fresh ideas. Scientific innovation combined with continued advances in drilling and completion technology revitalized the natural gas industry in North America by making production from shale economic. Similar advances are now happening in shale oil. The convergence of ideas and technology has created a commercial environment in which unconventional reservoirs could supply natural gas to the North American consumer for 50 years or more. And, although not as far along in terms of resource development, oil from the Eagle Ford and Bakken Shales and the oil sands in Alberta could have a similar impact. Without advanced horizontal drilling, geosteering, staged hydraulic-fracture stimulation, synthetic and natural proppants, evolution of hydraulic fluid chemistry, and high-end monitoring and simulation, many of these plays would not exist. Yet drilling and completion technology cannot stand alone. Also required for success are creative thinking, favorable economics, and a tolerance for risk by operators. Current understanding and completion practices will leave upwards of 80% of oil and natural gas in the shale reservoirs. The opportunity to enhance recovery through advanced reservoir understanding and imaging, as well as through recompletions and infill drilling, is considerable. The path from ideas to commercialization will continue to provide economic results in unconventional reservoirs.
Prevention of Reservoir Interior Discoloration
Arnold, K.F.
2001-04-03
Contamination is anathema in reservoir production. Some of the contamination is a result of welding and some appears after welding but existed before. Oxygen was documented to be a major contributor to discoloration in welding. This study demonstrates that it can be controlled and that some of the informal cleaning processes contribute to contamination.
Jirik, L.A. )
1990-09-01
Detailed evaluation of middle Frio (Oligocene) fluvial sandstones reveals a complex architectural style potentially suited to the addition of gas reserves through recognition of poorly drained reservoir compartments and bypassed gas zones. Seeligson field is being studied as part of a Gas Research Institute/US Department of Energy/State of Texas-sponsored program, with the cooperation of Oryx Energy Company and Mobil Exploration and Producing US, Inc. Four reservoirs, Zones 15, 16D, 16E, and 19C, were studied in a 20 mi{sup 2} area within Seeligson field. Collectively, these reservoirs have produced more than 240 bcf of gas from wells within the study area. Detailed electric log correlation of individual reservoirs enabled subdivision of aggregate producing zones into component genetic units. Cross sections, net-sandstone maps, and log-facies maps were prepared to illustrate depositional style, sand-body geometry, and reservoir heterogeneity. Zones 15 and 19C are examples of laterally stacked fluvial architecture. Individual channel-fill sandstones range from 10 to 50 ft thick, and channel widths are approximately 2,500 ft. Crevasse-splay sandstones may extend a few thousand feet from the main channel system. Multiple, overlapping channel and splay deposits commonly form sand-rich belts that result in leaky reservoir compartments that may be incompletely drained. Zones 16D and 16E are examples of vertically stacked fluvial architecture, with discrete, relatively thin and narrow channel and splay sandstones generally encased within floodplain muds. This architectural style is likely to form more isolated reservoir compartments. Although all of these reservoirs are currently considered nearly depleted, low-pressure producers, recent well completions and bottomhole pressure data indicate that untapped or poorly drained compartments are being encountered.
ERTS-1 study of reservoirs in Kansas.
NASA Technical Reports Server (NTRS)
Yarger, H. L.; James, G. W.; Magnuson, L. M.; Coiner, J. C.; Mccauley, J. R.; Marzolf, G. R.
1973-01-01
Single pass coverage over Cedar Bluff, Webster, Tuttle Creek, Milford, and Council Groves reservoirs is analyzed. The long-range goal of the study is to test the feasibility of monitoring reservoirs by satellite. It is hoped that results may eventually help to optimize reservoir management for use in flood control, agriculture, urban areas, and recreation. ERTS-1 imagery promises to be a very useful tool for studying reservoir turbidity patterns. Initial coverage indicates a strong qualitative correlation between film density and turbidity.
Reservoir System Analysis for Water Quality.
1984-08-01
reservoirs on flows and damages in the system. The program should also be useful In selecting the 2 PHASE Z- 1979 SINGLE RESERVOIR SIMULATION FOR WATER...TEMPERATURE PHASE H- 1980 TWO RESERVOIR SIMULATION FOR WATER TEMPERATURE AND SEVEN CONSTITUENTS 1981 FIELD TESTING AND MINOR MODIFICATIONS PHASE M- 1982...TEN RESERVOIR SIMULATION FOR WATER TEMPERATURE AND . TAB SEVEN CONSTITUENTS 1P.IX Ot1Oun4 ___ ___ __ __ ___ __ ___ __ ___ _ .zt ltl@a’tlo@ . 113
Wallace, R.E.
1990-01-01
The San Andreas fault system, a complex of faults that display predominantly large-scale strike slip, is part of an even more complex system of faults, isolated segments of the East Pacific Rise, and scraps of plates lying east of the East Pacific Rise that collectively separate the North American plate from the Pacific plate. This chapter briefly describes the San Andreas fault system, its setting along the Pacific Ocean margin of North America, its extent, and the patterns of faulting. Only selected characteristics are described, and many features are left for depictions on maps and figures.
Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs
Nurhandoko, Bagus Endar B. E-mail: bagusnur@rock-fluid.com; Susilowati E-mail: bagusnur@rock-fluid.com
2015-04-16
Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.
Current Density and Continuity in Discretized Models
ERIC Educational Resources Information Center
Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard
2010-01-01
Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schrodinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying…
Discretization vs. Rounding Error in Euler's Method
ERIC Educational Resources Information Center
Borges, Carlos F.
2011-01-01
Euler's method for solving initial value problems is an excellent vehicle for observing the relationship between discretization error and rounding error in numerical computation. Reductions in stepsize, in order to decrease discretization error, necessarily increase the number of steps and so introduce additional rounding error. The problem is…
Tenth workshop on geothermal reservoir engineering: proceedings
Not Available
1985-01-22
The workshop contains presentations in the following areas: (1) reservoir engineering research; (2) field development; (3) vapor-dominated systems; (4) the Geysers thermal area; (5) well test analysis; (6) production engineering; (7) reservoir evaluation; (8) geochemistry and injection; (9) numerical simulation; and (10) reservoir physics. (ACR)
Reservoir System Regulation for Water Quality Control.
1983-03-01
Davis, California 95616. [PHASE I!- 1979 SINGLE RESERVOIR SIMULATION FOR WATER TEMPERATURE PHASE 31- 1980 TWO RESERVOIR SIMULATION FOR WATER TEMPERATURE...AND SEVEN CONSTITUENTS 1981 FIELD TESTING AND MINOR MODIFICATIONS ’IFI PHASE 3nm- 1982 TEN RESERVOIR SIMULATION FOR WATER TEMPERATURE AND SEVEN
49 CFR 236.792 - Reservoir, equalizing.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Reservoir, equalizing. 236.792 Section 236.792 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Reservoir, equalizing. An air reservoir connected with and adding volume to the top portion of...
49 CFR 236.792 - Reservoir, equalizing.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 49 Transportation 4 2012-10-01 2012-10-01 false Reservoir, equalizing. 236.792 Section 236.792 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Reservoir, equalizing. An air reservoir connected with and adding volume to the top portion of...
49 CFR 236.792 - Reservoir, equalizing.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 49 Transportation 4 2014-10-01 2014-10-01 false Reservoir, equalizing. 236.792 Section 236.792 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Reservoir, equalizing. An air reservoir connected with and adding volume to the top portion of...
49 CFR 236.792 - Reservoir, equalizing.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 4 2013-10-01 2013-10-01 false Reservoir, equalizing. 236.792 Section 236.792 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Reservoir, equalizing. An air reservoir connected with and adding volume to the top portion of...
49 CFR 236.792 - Reservoir, equalizing.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 49 Transportation 4 2011-10-01 2011-10-01 false Reservoir, equalizing. 236.792 Section 236.792 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Reservoir, equalizing. An air reservoir connected with and adding volume to the top portion of...
Ekofisk reservoir voidage and seabed subsidence
Mes, M.J. )
1990-11-01
Field data describing the time lag between Ekofisk subsidence and reservoir voidage are given. A method to discriminate between real subsidence variations and random-data errors and a procedure to derive a contemporary relationship between reservoir voidage and seabed subsidence are presented. At Ekofisk, most subsidence lags reservoir voidage by 2 to 3 months.
49 CFR 393.50 - Reservoirs required.
Code of Federal Regulations, 2012 CFR
2012-10-01
... using air or vacuum braking must have either reserve capacity, or a reservoir, that would enable the.... Each service reservoir system on a motor vehicle shall be protected against a loss of air pressure or vacuum due to a failure or leakage in the system between the service reservoir and the source of...
49 CFR 393.50 - Reservoirs required.
Code of Federal Regulations, 2010 CFR
2010-10-01
... using air or vacuum braking must have either reserve capacity, or a reservoir, that would enable the.... Each service reservoir system on a motor vehicle shall be protected against a loss of air pressure or vacuum due to a failure or leakage in the system between the service reservoir and the source of...
49 CFR 393.50 - Reservoirs required.
Code of Federal Regulations, 2013 CFR
2013-10-01
... using air or vacuum braking must have either reserve capacity, or a reservoir, that would enable the.... Each service reservoir system on a motor vehicle shall be protected against a loss of air pressure or vacuum due to a failure or leakage in the system between the service reservoir and the source of...
49 CFR 393.50 - Reservoirs required.
Code of Federal Regulations, 2011 CFR
2011-10-01
... using air or vacuum braking must have either reserve capacity, or a reservoir, that would enable the.... Each service reservoir system on a motor vehicle shall be protected against a loss of air pressure or vacuum due to a failure or leakage in the system between the service reservoir and the source of...
NASA Astrophysics Data System (ADS)
Reagan, Matthew T.; Moridis, George J.; Keen, Noel D.; Johnson, Jeffrey N.
2015-04-01
Hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques, such as hydraulic fracturing, has grown explosively over the last decade. However, concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers, thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids. This study investigates, by numerical simulation, gas and water transport between a shallow tight-gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations, if such a connecting pathway has been created. We focus on two general failure scenarios: (1) communication between the reservoir and aquifer via a connecting fracture or fault and (2) communication via a deteriorated, preexisting nearby well. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure, and not producing may increase the potential for release. We also find that hydrostatic tight-gas reservoirs are unlikely to act as a continuing source of migrating gas, as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination. Such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes.
Reagan, Matthew T; Moridis, George J; Keen, Noel D; Johnson, Jeffrey N
2015-04-01
Hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques, such as hydraulic fracturing, has grown explosively over the last decade. However, concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers, thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids. This study investigates, by numerical simulation, gas and water transport between a shallow tight-gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations, if such a connecting pathway has been created. We focus on two general failure scenarios: (1) communication between the reservoir and aquifer via a connecting fracture or fault and (2) communication via a deteriorated, preexisting nearby well. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure, and not producing may increase the potential for release. We also find that hydrostatic tight-gas reservoirs are unlikely to act as a continuing source of migrating gas, as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination. Such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes.
Extreme events in discrete nonlinear lattices.
Maluckov, A; Hadzievski, Lj; Lazarides, N; Tsironis, G P
2009-02-01
We perform statistical analysis on discrete nonlinear waves generated through modulational instability in the context of the Salerno model that interpolates between the integrable Ablowitz-Ladik (AL) equation and the nonintegrable discrete nonlinear Schrödinger equation. We focus on extreme events in the form of discrete rogue or freak waves that may arise as a result of rapid coalescence of discrete breathers or other nonlinear interaction processes. We find power law dependence in the wave amplitude distribution accompanied by an enhanced probability for freak events close to the integrable limit of the equation. A characteristic peak in the extreme event probability appears that is attributed to the onset of interaction of the discrete solitons of the AL equation and the accompanied transition from the local to the global stochasticity monitored through the positive Lyapunov exponent of a nonlinear map.
Discrete multiscale wavelet shrinkage and integrodifferential equations
NASA Astrophysics Data System (ADS)
Didas, S.; Steidl, G.; Weickert, J.
2008-04-01
We investigate the relation between discrete wavelet shrinkage and integrodifferential equations in the context of simplification and denoising of one-dimensional signals. In the continuous setting, strong connections between these two approaches were discovered in 6 (see references). The key observation is that the wavelet transform can be understood as derivative operator after the convolution with a smoothing kernel. In this paper, we extend these ideas to the practically relevant discrete setting with both orthogonal and biorthogonal wavelets. In the discrete case, the behaviour of the smoothing kernels for different scales requires additional investigation. The results of discrete multiscale wavelet shrinkage and related discrete versions of integrodifferential equations are compared with respect to their denoising quality by numerical experiments.
Generalized exponential function and discrete growth models
NASA Astrophysics Data System (ADS)
Souto Martinez, Alexandre; Silva González, Rodrigo; Lauri Espíndola, Aquino
2009-07-01
Here we show that a particular one-parameter generalization of the exponential function is suitable to unify most of the popular one-species discrete population dynamic models into a simple formula. A physical interpretation is given to this new introduced parameter in the context of the continuous Richards model, which remains valid for the discrete case. From the discretization of the continuous Richards’ model (generalization of the Gompertz and Verhulst models), one obtains a generalized logistic map and we briefly study its properties. Notice, however that the physical interpretation for the introduced parameter persists valid for the discrete case. Next, we generalize the (scramble competition) θ-Ricker discrete model and analytically calculate the fixed points as well as their stabilities. In contrast to previous generalizations, from the generalized θ-Ricker model one is able to retrieve either scramble or contest models.
Active control of turbomachine discrete tones
NASA Astrophysics Data System (ADS)
Fleeter, Sanford
This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.
Seleson, Pablo; Du, Qiang; Parks, Michael L.
2016-08-16
The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of such discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest
A unified framework for modeling landscape evolution by discrete flows
NASA Astrophysics Data System (ADS)
Shelef, Eitan; Hilley, George E.
2016-05-01
Topographic features such as branched valley networks and undissected convex-up hillslopes are observed in disparate physical environments. In some cases, these features are formed by sediment transport processes that occur discretely in space and time, while in others, by transport processes that are uniformly distributed across the landscape. This paper presents an analytical framework that reconciles the basic attributes of such sediment transport processes with the topographic features that they form and casts those in terms that are likely common to different physical environments. In this framework, temporal changes in surface elevation reflect the frequency with which the landscape is traversed by geophysical flows generated discretely in time and space. This frequency depends on the distance to which flows travel downslope, which depends on the dynamics of individual flows, the lithologic and topographic properties of the underlying substrate, and the coevolution of topography, erosion, and the routing of flows over the topographic surface. To explore this framework, we postulate simple formulations for sediment transport and flow runout distance and demonstrate that the conditions for hillslope and channel network formation can be cast in terms of fundamental parameters such as distance from drainage divide and a friction-like coefficient that describes a flow's resistance to motion. The framework we propose is intentionally general, but the postulated formulas can be substituted with those that aim to describe a specific process and to capture variations in the size distribution of such flow events.
Different pressure grids for reservoir simulation in heterogeneous reservoirs
Guerillot, D.R.; Verdiere, S.
1995-12-31
Petroleum reservoirs are made of highly heterogeneous rocks. These reservoirs could be described by geostatistical models composed of millions of cells. Currently, fluid flow simulations performed within these media need upscaling (or averaging) techniques. Hence, their results are given by averaging on cells which are much larger than the geological model cells. To overcome this problem, the Dual Mesh Method is proposed here, whose purpose is to solve the pressure equation on a low resolution grid, and then to interpolate pressure over the fine mesh by taking into account small scale heterogeneities of the mediums. The aim of this paper is the interpolation step; its implementation is presented and illustrated in a five-spot pattern for three different rock characteristics.
A chemical EOR benchmark study of different reservoir simulators
NASA Astrophysics Data System (ADS)
Goudarzi, Ali; Delshad, Mojdeh; Sepehrnoori, Kamy
2016-09-01
Interest in chemical EOR processes has intensified in recent years due to the advancements in chemical formulations and injection techniques. Injecting Polymer (P), surfactant/polymer (SP), and alkaline/surfactant/polymer (ASP) are techniques for improving sweep and displacement efficiencies with the aim of improving oil production in both secondary and tertiary floods. There has been great interest in chemical flooding recently for different challenging situations. These include high temperature reservoirs, formations with extreme salinity and hardness, naturally fractured carbonates, and sandstone reservoirs with heavy and viscous crude oils. More oil reservoirs are reaching maturity where secondary polymer floods and tertiary surfactant methods have become increasingly important. This significance has added to the industry's interest in using reservoir simulators as tools for reservoir evaluation and management to minimize costs and increase the process efficiency. Reservoir simulators with special features are needed to represent coupled chemical and physical processes present in chemical EOR processes. The simulators need to be first validated against well controlled lab and pilot scale experiments to reliably predict the full field implementations. The available data from laboratory scale include 1) phase behavior and rheological data; and 2) results of secondary and tertiary coreflood experiments for P, SP, and ASP floods under reservoir conditions, i.e. chemical retentions, pressure drop, and oil recovery. Data collected from corefloods are used as benchmark tests comparing numerical reservoir simulators with chemical EOR modeling capabilities such as STARS of CMG, ECLIPSE-100 of Schlumberger, REVEAL of Petroleum Experts. The research UTCHEM simulator from The University of Texas at Austin is also included since it has been the benchmark for chemical flooding simulation for over 25 years. The results of this benchmark comparison will be utilized to improve
ADVANCED TECHNIQUES FOR RESERVOIR SIMULATION AND MODELING OF NONCONVENTIONAL WELLS
Louis J. Durlofsky; Khalid Aziz
2004-08-20
); and (3) accurate approaches to account for the effects of reservoir heterogeneity and for the optimization of nonconventional well deployment. An overview of our progress in each of these main areas is as follows. A general purpose object-oriented research simulator (GPRS) was developed under this project. The GPRS code is managed using modern software management techniques and has been deployed to many companies and research institutions. The simulator includes general black-oil and compositional modeling modules. The formulation is general in that it allows for the selection of a wide variety of primary and secondary variables and accommodates varying degrees of solution implicitness. Specifically, we developed and implemented an IMPSAT procedure (implicit in pressure and saturation, explicit in all other variables) for compositional modeling as well as an adaptive implicit procedure. Both of these capabilities allow for efficiency gains through selective implicitness. The code treats cell connections through a general connection list, which allows it to accommodate both structured and unstructured grids. The GPRS code was written to be easily extendable so new modeling techniques can be readily incorporated. Along these lines, we developed a new dual porosity module compatible with the GPRS framework, as well as a new discrete fracture model applicable for fractured or faulted reservoirs. Both of these methods display substantial advantages over previous implementations. Further, we assessed the performance of different preconditioners in an attempt to improve the efficiency of the linear solver. As a result of this investigation, substantial improvements in solver performance were achieved.
Production of superheated steam from vapor-dominated geothermal reservoirs
Truesdell, A.H.; White, D.E.
1973-01-01
Vapor-dominated geothermal systems such as Larderello, Italy, The Geysers, California, and Matsukawa, Japan yield dry or superheated steam when exploited. Models for these systems are examined along with production data and the thermodynamic properties of water, steam and rock. It is concluded that these systems initially consist of a water and steam filled reservoir, a water-saturated cap rock, and a water or brine-saturated deep reservoir below a water table. Most liquid water in all parts of the system is relatively immobilized in small pores and crevices; steam dominates the large fractures and voids of the reservoir and is the continuous, pressure-controlling phase. With production, the pressure is lowered and the liquid water boils, causing massive transfer of heat from the rock and its eventual drying. Passage of steam through already dried rock produces superheating. After an initial vaporization of liquid water in the reservoir, the decrease in pressure produces increased boiling below the deep water table. With heavy exploitation, boiling extends deeper into hotter rock and the temperature of the steam increases. This model explains most features of the published production behavior of these systems and can be used to guide exploitation policies. ?? 1973.
Tandem-type pulse tube refrigerator without reservoir
NASA Astrophysics Data System (ADS)
Ki, Taekyung; Jeong, Sangkwon; Ko, Junseok; Park, Jiho
2015-12-01
In this paper, a tandem-type pulse tube refrigerator without a reservoir is discussed and investigated. For its practical application a tandem-type compressor is designed to generate two pulsating pressure waves with opposite phases, simultaneously. A tandem-type pulse tube refrigerator consists of a tandem-type compressor and two identical pulse tube refrigerators. The two identical pulse tube refrigerators share the same heat exchangers and one can be connected with the other by an inertance tube without a reservoir. In this proposed configuration, the mechanical vibration and temperature oscillations in the cold-end heat exchanger can be internally suppressed due to its intrinsic opposite-characteristic operation. To examine the quantitative evaluation of the tandem feature which does not require a reservoir in the pulse tube, an evolutionary approach has been attempted. A general structure of a pulse tube refrigerator is modified into tandem Stirling-type and GM-type machines and the transformed configuration has been simulated for tandem operation. The simulation results clearly demonstrate that a properly designed tandem-type pulse tube refrigerator without a reservoir can function favorably.
Salt tectonics, patterns of basin fill, and reservoir distribution
Yorston, H.J.; Miles, A.E.
1988-02-01
Salt structures, which develop due to sediment loading, gravity creep, and/or buoyancy, include boundary-fault grabens and half grabens, rollers, anticlines, domes and walls, diapirs, sills, massifs, and compressional toe structures. Associated features include fault systems and turtle structures. Of these, six directly relate to basin fill and all directly influence the distribution of reservoir facies. Salt structuring is initiated by sedimentation, which in turn is localized by salt withdrawal. Withdrawal produces individual salt structures, migrating sills, dissected massifs, and regional depocenters bordered by salt walls. Composite withdrawals dictate the patterns of basin fill. Relative rates of structural growth and sedimentation control the distribution of reservoir facies. When growth dominates, sands are channeled into lows. When sedimentation dominates and maintains flat surfaces, facies distribution is not impacted except where faulting develops. Turtle structures, developed by the inversion of peripheral synclines, can move sands into favorable structural position and/or serve as platforms for carbonate reservoir development. Salt growth varies with type structure, stage of development, and rate of sedimentation. Sedimentation at a specific location depends on basin position, sediment transport system, sea level stand, and rate of salt withdrawal. This paper presents techniques for using seismic data to determine the controls on salt structural growth and sedimentation and the patterns of basin fill and reservoir distribution.
Discrete vortices on anisotropic lattices
NASA Astrophysics Data System (ADS)
Chen, Gui-Hua; Wang, Hong-Cheng; Chen, Zi-Fa
2015-08-01
We consider the effects of anisotropy on two types of localized states with topological charges equal to 1 in two-dimensional nonlinear lattices, using the discrete nonlinear Schrödinger equation as a paradigm model. We find that on-site-centered vortices with different propagation constants are not globally stable, and that upper and lower boundaries of the propagation constant exist. The region between these two boundaries is the domain outside of which the on-site-centered vortices are unstable. This region decreases in size as the anisotropy parameter is gradually increased. We also consider off-site-centered vortices on anisotropic lattices, which are unstable on this lattice type and either transform into stable quadrupoles or collapse. We find that the transformation of off-sitecentered vortices into quadrupoles, which occurs on anisotropic lattices, cannot occur on isotropic lattices. In the quadrupole case, a propagation-constant region also exists, outside of which the localized states cannot stably exist. The influence of anisotropy on this region is almost identical to its effects on the on-site-centered vortex case.
MULTISCALE DISCRETIZATION OF SHAPE CONTOURS
Prasad, L.; Rao, R.
2000-09-01
We present an efficient multi-scale scheme to adaptively approximate the continuous (or densely sampled) contour of a planar shape at varying resolutions. The notion of shape is intimately related to the notion of contour, and the efficient representation of the contour of a shape is vital to a computational understanding of the shape. Any polygonal approximation of a planar smooth curve is equivalent to a piecewise constant approximation of the parameterized X and Y coordinate functions of a discrete point set obtained by densely sampling the curve. Using the Haar wavelet transform for the piecewise approximation yields a hierarchical scheme in which the size of the approximating point set is traded off against the morphological accuracy of the approximation. Our algorithm compresses the representation of the initial shape contour to a sparse sequence of points in the plane defining the vertices of the shape's polygonal approximation. Furthermore, it is possible to control the overall resolution of the approximation by a single, scale-independent parameter.
Elsworth, Derek; Izadi, Ghazal; Gan, Quan; Fang, Yi; Taron, Josh; Sonnenthal, Eric
2015-07-28
This work has investigated the roles of effective stress induced by changes in fluid pressure, temperature and chemistry in contributing to the evolution of permeability and induced seismicity in geothermal reservoirs. This work has developed continuum models [1] to represent the progress or seismicity during both stimulation [2] and production [3]. These methods have been used to resolve anomalous observations of induced seismicity at the Newberry Volcano demonstration project [4] through the application of modeling and experimentation. Later work then focuses on the occurrence of late stage seismicity induced by thermal stresses [5] including the codifying of the timing and severity of such responses [6]. Furthermore, mechanistic linkages between observed seismicity and the evolution of permeability have been developed using data from the Newberry project [7] and benchmarked against field injection experiments. Finally, discontinuum models [8] incorporating the roles of discrete fracture networks have been applied to represent stimulation and then thermal recovery for new arrangements of geothermal wells incorporating the development of flow manifolds [9] in order to increase thermal output and longevity in EGS systems.
Discrete-ordinates finite-element method for atmospheric radiative transfer and remote sensing
NASA Technical Reports Server (NTRS)
Gerstl, S. A. W.; Zardecki, A.
1985-01-01
The principal features of the discrete-ordinates finite-element method are reviewed, and the applicability of general-purpose discrete-ordinates codes to atmospheric radiative transfer and remote sensing problems is demonstrated. In particular, numerical results for typical problems arising in meteorology, climatology, and remote sensing are shown to be in good agreement with results from other methods and measurements. A sample two-dimensional calculation demonstrates that specific capabilities available in the discrete-ordinates code TWOTRAN can produce new results that are valuable in the characterization of atmospheric effects on remote sensing (e.g., the adjacency effect). The intrinsic limitations of the method are also considered, and it is concluded that the strengths of the discrete-ordinates finite-element method outweigh its weaknesses.
Susan Nissen; Saibal Bhattacharya; W. Lynn Watney; John Doveton
2009-03-31
Our project goal was to develop innovative seismic-based workflows for the incremental recovery of oil from karst-modified reservoirs within the onshore continental United States. Specific project objectives were: (1) to calibrate new multi-trace seismic attributes (volumetric curvature, in particular) for improved imaging of karst-modified reservoirs, (2) to develop attribute-based, cost-effective workflows to better characterize karst-modified carbonate reservoirs and fracture systems, and (3) to improve accuracy and predictiveness of resulting geomodels and reservoir simulations. In order to develop our workflows and validate our techniques, we conducted integrated studies of five karst-modified reservoirs in west Texas, Colorado, and Kansas. Our studies show that 3-D seismic volumetric curvature attributes have the ability to re-veal previously unknown features or provide enhanced visibility of karst and fracture features compared with other seismic analysis methods. Using these attributes, we recognize collapse features, solution-enlarged fractures, and geomorphologies that appear to be related to mature, cockpit landscapes. In four of our reservoir studies, volumetric curvature attributes appear to delineate reservoir compartment boundaries that impact production. The presence of these compartment boundaries was corroborated by reservoir simulations in two of the study areas. Based on our study results, we conclude that volumetric curvature attributes are valuable tools for mapping compartment boundaries in fracture- and karst-modified reservoirs, and we propose a best practices workflow for incorporating these attributes into reservoir characterization. When properly calibrated with geological and production data, these attributes can be used to predict the locations and sizes of undrained reservoir compartments. Technology transfer of our project work has been accomplished through presentations at professional society meetings, peer-reviewed publications
Stability of discrete systems near a multivalued equilibrium
Kuntsevich, V.M.; Pokotilo, V.G.
1995-01-01
The main objective of this article is to derive sufficient conditions of stability in the small for ensembles of trajectories of nonlinar discrete systems near multivalued equilibria. The stability conditions are expressed in terms of a linearized system, and we examine the effect of the structure of invariant sets near which the behavior of the system is investigated. On the one hand, this approach provides a clearer picture of the specific features of multivalued systems and, on the other hand, it produces results that characterize stability of analogs of periodic motion.
The discrete nature of circumstellar OH maser emission
NASA Technical Reports Server (NTRS)
Zell, Philip J.; Fix, John D.
1990-01-01
The Arecibo radio telescope was used to obtain high-resolution, high-SNR 1612-MHz observations of seven circumstellar OH maser sources. Each spectrum displays the double-peaked emission line profile characteristics of an expanding shell. The jaggedness of the spectra, which varies from source to source, is consistent with statistical fluctuations in the number of discrete emitting elements contributing at a given velocity. In particular, it is found that the spectra of WX Psc and OH 53.6-0.2 contain narrow, weak, isolated emission features which may arise from individual emitting elements.
NASA Astrophysics Data System (ADS)
Schwarz, F.; Goldstein, M.; Dorda, A.; Arrigoni, E.; Weichselbaum, A.; von Delft, J.
2016-10-01
The description of interacting quantum impurity models in steady-state nonequilibrium is an open challenge for computational many-particle methods: the numerical requirement of using a finite number of lead levels and the physical requirement of describing a truly open quantum system are seemingly incompatible. One possibility to bridge this gap is the use of Lindblad-driven discretized leads (LDDL): one couples auxiliary continuous reservoirs to the discretized lead levels and represents these additional reservoirs by Lindblad terms in the Liouville equation. For quadratic models governed by Lindbladian dynamics, we present an elementary approach for obtaining correlation functions analytically. In a second part, we use this approach to explicitly discuss the conditions under which the continuum limit of the LDDL approach recovers the correct representation of thermal reservoirs. As an analytically solvable example, the nonequilibrium resonant level model is studied in greater detail. Lastly, we present ideas towards a numerical evaluation of the suggested Lindblad equation for interacting impurities based on matrix product states. In particular, we present a reformulation of the Lindblad equation, which has the useful property that the leads can be mapped onto a chain where both the Hamiltonian dynamics and the Lindblad driving are local at the same time. Moreover, we discuss the possibility to combine the Lindblad approach with a logarithmic discretization needed for the exploration of exponentially small energy scales.
49 CFR 229.31 - Main reservoir tests.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 49 Transportation 4 2014-10-01 2014-10-01 false Main reservoir tests. 229.31 Section 229.31... reservoir tests. (a) Before it is placed in service, each main reservoir other than an aluminum reservoir... intervals that do not exceed 736 calendar days, each main reservoir other than an aluminum reservoir...
49 CFR 229.31 - Main reservoir tests.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Main reservoir tests. 229.31 Section 229.31... reservoir tests. (a) Before it is placed in service, each main reservoir other than an aluminum reservoir... intervals that do not exceed 736 calendar days, each main reservoir other than an aluminum reservoir...
49 CFR 229.31 - Main reservoir tests.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 4 2013-10-01 2013-10-01 false Main reservoir tests. 229.31 Section 229.31... reservoir tests. (a) Before it is placed in service, each main reservoir other than an aluminum reservoir... intervals that do not exceed 736 calendar days, each main reservoir other than an aluminum reservoir...
49 CFR 229.31 - Main reservoir tests.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 49 Transportation 4 2012-10-01 2012-10-01 false Main reservoir tests. 229.31 Section 229.31... reservoir tests. (a) Before it is placed in service, each main reservoir other than an aluminum reservoir... intervals that do not exceed 736 calendar days, each main reservoir other than an aluminum reservoir...
49 CFR 229.31 - Main reservoir tests.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 49 Transportation 4 2011-10-01 2011-10-01 false Main reservoir tests. 229.31 Section 229.31... reservoir tests. (a) Before it is placed in service, each main reservoir other than an aluminum reservoir... intervals that do not exceed 736 calendar days, each main reservoir other than an aluminum reservoir...
4. International reservoir characterization technical conference
1997-04-01
This volume contains the Proceedings of the Fourth International Reservoir Characterization Technical Conference held March 2-4, 1997 in Houston, Texas. The theme for the conference was Advances in Reservoir Characterization for Effective Reservoir Management. On March 2, 1997, the DOE Class Workshop kicked off with tutorials by Dr. Steve Begg (BP Exploration) and Dr. Ganesh Thakur (Chevron). Tutorial presentations are not included in these Proceedings but may be available from the authors. The conference consisted of the following topics: data acquisition; reservoir modeling; scaling reservoir properties; and managing uncertainty. Selected papers have been processed separately for inclusion in the Energy Science and Technology database.
Compatible Spatial Discretizations for Partial Differential Equations
Arnold, Douglas, N, ed.
2004-11-25
From May 11--15, 2004, the Institute for Mathematics and its Applications held a hot topics workshop on Compatible Spatial Discretizations for Partial Differential Equations. The numerical solution of partial differential equations (PDE) is a fundamental task in science and engineering. The goal of the workshop was to bring together a spectrum of scientists at the forefront of the research in the numerical solution of PDEs to discuss compatible spatial discretizations. We define compatible spatial discretizations as those that inherit or mimic fundamental properties of the PDE such as topology, conservation, symmetries, and positivity structures and maximum principles. A wide variety of discretization methods applied across a wide range of scientific and engineering applications have been designed to or found to inherit or mimic intrinsic spatial structure and reproduce fundamental properties of the solution of the continuous PDE model at the finite dimensional level. A profusion of such methods and concepts relevant to understanding them have been developed and explored: mixed finite element methods, mimetic finite differences, support operator methods, control volume methods, discrete differential forms, Whitney forms, conservative differencing, discrete Hodge operators, discrete Helmholtz decomposition, finite integration techniques, staggered grid and dual grid methods, etc. This workshop seeks to foster communication among the diverse groups of researchers designing, applying, and studying such methods as well as researchers involved in practical solution of large scale problems that may benefit from advancements in such discretizations; to help elucidate the relations between the different methods and concepts; and to generally advance our understanding in the area of compatible spatial discretization methods for PDE. Particular points of emphasis included: + Identification of intrinsic properties of PDE models that are critical for the fidelity of numerical
Integration Over Connections in the Discretized Gravitational Functional Integrals
NASA Astrophysics Data System (ADS)
Khatsymovsky, V. M.
The result of performing integrations over connection type variables in the path integral for the discrete field theory may be poorly defined in the case of non-compact gauge group with the Haar measure exponentially growing in some directions. This point is studied in the case of the discrete form of the first-order formulation of the Einstein gravity theory. Here the result of interest can be defined as generalized function (of the rest of variables of the type of tetrad or elementary areas), i.e. a functional on a set of probe functions. To define this functional, we calculate its values on the products of components of the area tensors, the so-called moments. The resulting distribution (in fact, probability distribution) has singular (δ-function-like) part with support in the nonphysical region of the complex plane of area tensors and regular part (usual function) which decays exponentially at large areas. As we discuss, this also provides suppression of large edge lengths which is important for internal consistency, if one asks whether gravity on short distances can be discrete. Some other features of the obtained probability distribution including occurrence of the local maxima at a number of the approximately equidistant values of area are also considered.
Fowler, M.L.; Young, M.A.; Madden, M.P.
1997-08-01
Optimum reservoir recovery and profitability result from guidance of reservoir practices provided by an effective reservoir management plan. Success in developing the best, most appropriate reservoir management plan requires knowledge and consideration of (1) the reservoir system including rocks, and rock-fluid interactions (i.e., a characterization of the reservoir) as well as wellbores and associated equipment and surface facilities; (2) the technologies available to describe, analyze, and exploit the reservoir; and (3) the business environment under which the plan will be developed and implemented. Reservoir characterization is the essential to gain needed knowledge of the reservoir for reservoir management plan building. Reservoir characterization efforts can be appropriately scaled by considering the reservoir management context under which the plan is being built. Reservoir management plans de-optimize with time as technology and the business environment change or as new reservoir information indicates the reservoir characterization models on which the current plan is based are inadequate. BDM-Oklahoma and the Department of Energy have implemented a program of reservoir management demonstrations to encourage operators with limited resources and experience to learn, implement, and disperse sound reservoir management techniques through cooperative research and development projects whose objectives are to develop reservoir management plans. In each of the three projects currently underway, careful attention to reservoir management context assures a reservoir characterization approach that is sufficient, but not in excess of what is necessary, to devise and implement an effective reservoir management plan.
NASA Astrophysics Data System (ADS)
Reiter, Karsten; Heidbach, Oliver; Moeck, Inga
2013-04-01
For the assessment and exploration of a potential geothermal reservoir, the contemporary in-situ stress is of key importance in terms of well stability and orientation of possible fluid pathways. However, available data, e.g. Heidbach et al. (2009) or Zang et al. (2012), deliver only point wise information of parts of the six independent components of the stress tensor. Moreover most measurements of the stress orientation and magnitude are done for hydrocarbon industry obvious in shallow depth. Interpolation across long distances or extrapolation into depth is unfavourable, because this would ignore structural features, inhomogeneity's in the crust or other local effects like topography. For this reasons geomechanical numerical modelling is the favourable method to quantify orientations and magnitudes of the 3D stress field for a geothermal reservoir. A geomechanical-numerical modelling, estimating the 3D absolute stress state, requires the initial stress state as model constraints. But in-situ stress measurements within or close by a potential reservoir are rare. For that reason a larger regional geomechanical-numerical model is necessary, which derive boundary conditions for the wanted local reservoir model. Such a large scale model has to be tested against in-situ stress measurements, orientations and magnitudes. Other suitable and available data, like GPS measurements or fault slip rates are useful to constrain kinematic boundary conditions. This stepwise approach from regional to local scale takes all stress field factors into account, from first over second up to third order. As an example we present a large scale crustal and upper mantle 3D-geomechanical-numerical model of the Alberta Basin and the surroundings, which is constructed to describe continuously the full stress tensor. In-situ stress measurements are the most likely data, because they deliver the most direct information's of the stress field and they provide insights into different depths, a
Trophic status evaluation of TVA reservoirs
Placke, J.F.
1983-10-01
TVA tributary and mainstem reservoirs show generalized differences in morphometry, hydraulics, nutrient loads, and response to nutrient concentrations. Neither type of reservoir is strictly comparable to the natural lakes on which classical eutrophication studies have been based. The majority of published trophic state indices and standards (e.g., hypolimnetic dissolved oxygen depletion, Secchi depth, areas nutrient loading rates, in-reservoir phosphorus concentrations) are inappropriate for evaluation of some or all TVA reservoirs. No single trophic potential or trophic response variable summarizes the mechanisms and manifestations of eutrophication sufficiently to be used as a sole criterion for judging or regulating TVA reservoir water quality. Relative multivariate trophic state indices were developed for mainstem and tributary reservoirs. Ranking of the mainstem reservoirs is based on chlorophyll, macrophyte coverage, hydraulic retention time, reservoir area less than five feet deep, annual pool elevation drawdown, and Secchi depth. Based on available data, the rank from least eutrophic to most eutrophic is: Pickwick, Kentucky, Chickamauga, Nickajack, Wilson, Fort Loudoun, Watts Bar, Wheeler, and Guntersville Reservoirs. Ranking of the tributary reservoirs is based on chlorophyll, total phosphorus and total nitrogen weighted by the N:P ratio, and bio-available inorganic carbon levels. The rank from least eutrophic to most eutrophic is: Hiwassee, Blue Ridge, Chatuge, Norris and Fontana, Watauga, South Holston, Tims Ford, Cherokee, Douglas, and Boone Reservoirs. 130 references, 18 figures, 30 tables.
Reservoir floodplains support distinct fish assemblages
Miranda, Leandro E.; Wigen, S. L.; Dagel, Jonah D.
2014-01-01
Reservoirs constructed on floodplain rivers are unique because the upper reaches of the impoundment may include extensive floodplain environments. Moreover, reservoirs that experience large periodic water level fluctuations as part of their operational objectives seasonally inundate and dewater floodplains in their upper reaches, partly mimicking natural inundations of river floodplains. In four flood control reservoirs in Mississippi, USA, we explored the dynamics of connectivity between reservoirs and adjacent floodplains and the characteristics of fish assemblages that develop in reservoir floodplains relative to those that develop in reservoir bays. Although fish species richness in floodplains and bays were similar, species composition differed. Floodplains emphasized fish species largely associated with backwater shallow environments, often resistant to harsh environmental conditions. Conversely, dominant species in bays represented mainly generalists that benefit from the continuous connectivity between the bay and the main reservoir. Floodplains in the study reservoirs provided desirable vegetated habitats at lower water level elevations, earlier in the year, and more frequently than in bays. Inundating dense vegetation in bays requires raising reservoir water levels above the levels required to reach floodplains. Therefore, aside from promoting distinct fish assemblages within reservoirs and helping promote diversity in regulated rivers, reservoir floodplains are valued because they can provide suitable vegetated habitats for fish species at elevations below the normal pool, precluding the need to annually flood upland vegetation that would inevitably be impaired by regular flooding. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
Geostatistics applied to gas reservoirs
Meunier, G.; Coulomb, C.; Laille, J.P. )
1989-09-01
The spatial distribution of many of the physical parameters connected with a gas reservoir is of primary interest to both engineers and geologists throughout the study, development, and operation of a field. It is therefore desirable for the distribution to be capable of statistical interpretation, to have a simple graphical representation, and to allow data to be entered from either two- or three-dimensional grids. To satisfy these needs while dealing with the geographical variables, new methods have been developed under the name geostatistics. This paper describes briefly the theory of geostatistics and its most recent improvements for the specific problem of subsurface description. The external-drift technique has been emphasized in particular, and in addition, four case studies related to gas reservoirs are presented.
Optimal nonpoint source pollution control strategies for a reservoir watershed in Taiwan.
Hsieh, Cheng-Daw; Yang, Wan-Fa
2007-12-01
The purpose of this study is to develop a model for optimal nonpoint source pollution control for the Fei-Tsui Reservoir watershed in Northern Taiwan. Several structural best management practices (BMPs) are selected to treat stormwater runoff. The complete model consists of two interacting components: an optimization model based on discrete differential dynamic programming (DDDP) and a zero-dimensional reservoir water quality model. A predefined procedure is used to locate suitable sites for construction of various selected BMPs in the watershed. In the optimization model, the objective function is to find the best combination of BMP type and placement, which minimizes the total construction and operation, maintenance, and repair (OMR) costs of the BMPs. The constraints are the water quality standards for total phosphorus (TP) and total suspended solids (TSS) concentrations in the reservoir. A zero-dimensional reservoir water quality model of the Vollenweider type is embedded in the optimization framework to simulate pollutant concentrations in Fei-Tsui Reservoir. The resulting optimal cost and benefit of water quality improvement are depicted by the model-derived trade-off curves. The modeling framework developed in the present study could be used as an efficient tool for planning a watershed-wide implementation of BMPs for mitigating stormwater pollution impact on the receiving water bodies.
Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries
NASA Astrophysics Data System (ADS)
Zuloaga-Molero, Pavel; Yu, Wei; Xu, Yifei; Sepehrnoori, Kamy; Li, Baozhen
2016-09-01
The recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the expected oil recovery factor from these reservoirs is still very low. CO2-based enhanced oil recovery is a suitable solution to improve the recovery. One challenge of the estimation of the recovery is to properly model complex hydraulic fracture geometries which are often assumed to be planar due to the limitation of local grid refinement approach. More flexible methods like the use of unstructured grids can significantly increase the computational demand. In this study, we introduce an efficient methodology of the embedded discrete fracture model to explicitly model complex fracture geometries. We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery. This study also provides new insights into the understanding of the impacts of CO2 molecular diffusion, reservoir permeability, and natural fractures on the performance of CO2-EOR processes in tight oil reservoirs.
Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries
Zuloaga-Molero, Pavel; Yu, Wei; Xu, Yifei; Sepehrnoori, Kamy; Li, Baozhen
2016-01-01
The recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the expected oil recovery factor from these reservoirs is still very low. CO2-based enhanced oil recovery is a suitable solution to improve the recovery. One challenge of the estimation of the recovery is to properly model complex hydraulic fracture geometries which are often assumed to be planar due to the limitation of local grid refinement approach. More flexible methods like the use of unstructured grids can significantly increase the computational demand. In this study, we introduce an efficient methodology of the embedded discrete fracture model to explicitly model complex fracture geometries. We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery. This study also provides new insights into the understanding of the impacts of CO2 molecular diffusion, reservoir permeability, and natural fractures on the performance of CO2-EOR processes in tight oil reservoirs. PMID:27628131
Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries.
Zuloaga-Molero, Pavel; Yu, Wei; Xu, Yifei; Sepehrnoori, Kamy; Li, Baozhen
2016-09-15
The recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the expected oil recovery factor from these reservoirs is still very low. CO2-based enhanced oil recovery is a suitable solution to improve the recovery. One challenge of the estimation of the recovery is to properly model complex hydraulic fracture geometries which are often assumed to be planar due to the limitation of local grid refinement approach. More flexible methods like the use of unstructured grids can significantly increase the computational demand. In this study, we introduce an efficient methodology of the embedded discrete fracture model to explicitly model complex fracture geometries. We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery. This study also provides new insights into the understanding of the impacts of CO2 molecular diffusion, reservoir permeability, and natural fractures on the performance of CO2-EOR processes in tight oil reservoirs.
Which spatial discretization for which distributed hydrological model?
NASA Astrophysics Data System (ADS)
Dehotin, J.; Braud, I.
2007-04-01
Distributed hydrological models are valuable tools to derive distributed estimation of water balance components or to study the impact of land-use or climate change on water resources and water quality. In these models, the choice of an appropriate spatial scale for the modelling units is a crucial issue. It is obviously linked to the available data and their scale, but not only. For a given catchment and a given data set, the "optimal" spatial discretization should be different according to the problem to be solved and the objectives of the modelling. Thus a flexible methodology is needed, especially for large catchments, to derive modelling units by performing suitable trade-off between available data, the dominant hydrological processes, their representation scale and the modelling objectives. In order to represent catchment heterogeneity efficiently according to the modelling goals, and the availability of the input data, we propose to use nested discretization, starting from a hierarchy of sub-catchments, linked by the river network topology. If consistent with the modelling objectives, the active hydrological processes and data availability, sub-catchment variability can be described using a finer nested discretization. The latter takes into account different geophysical factors such as topography, land-use, pedology, but also suitable hydrological discontinuities such as ditches, hedges, dams, etc. For small catchments, the landscape features such as agricultural fields, buildings, hedges, river reaches can be represented explicitly, as well as the water pathways between them. For larger catchments, such a representation is not feasible and simplification is necessary. For the sub-catchments discretization in these large catchments, we propose a flexible methodology based on the principles of landscape classification, using reference zones. These principles are independent from the catchment size. They allow to keep suitable features which are required in
On the definition of discrete hydrodynamic variables.
Español, Pep; Zúñiga, Ignacio
2009-10-28
The Green-Kubo formula for discrete hydrodynamic variables involves information about not only the fluid transport coefficients but also about discrete versions of the differential operators that govern the evolution of the discrete variables. This gives an intimate connection between discretization procedures in fluid dynamics and coarse-graining procedures used to obtain hydrodynamic behavior of molecular fluids. We observed that a natural definition of discrete hydrodynamic variables in terms of Voronoi cells leads to a Green-Kubo formula which is divergent, rendering the full coarse-graining strategy useless. In order to understand this subtle issue, in the present paper we consider the coarse graining of noninteracting Brownian particles. The discrete hydrodynamic variable for this problem is the number of particles within Voronoi cells. Thanks to the simplicity of the model we spot the origin of the singular behavior of the correlation functions. We offer an alternative definition, based on the concept of a Delaunay cell that behaves properly, suggesting the use of the Delaunay construction for the coarse graining of molecular fluids at the discrete hydrodynamic level.
Carbonate fracture stratigraphy: An integrated outcrop and 2D discrete element modelling study
NASA Astrophysics Data System (ADS)
Spence, Guy; Finch, Emma
2013-04-01
Constraining fracture stratigraphy is important as natural fractures control primary fluid flow in low matrix permeability naturally fractured carbonate hydrocarbon reservoirs. Away from the influence of folds and faults, stratigraphic controls are known to be the major control on fracture networks. The fracture stratigraphy of carbonate nodular-chert rhythmite successions are investigated using a Discrete Element Modelling (DEM) technique and validated against observations from outcrops. Comparisons are made to the naturally fractured carbonates of the Eocene Thebes Formation exposed in the west central Sinai of Egypt, which form reservoir rocks in the nearby East Ras Budran Field. DEM allows mechanical stratigraphy to be defined as the starting conditions from which forward numerical modelling can generate fracture stratigraphy. DEM can incorporate both stratigraphic and lateral heterogeneity, and enable mechanical and fracture stratigraphy to be characterised separately. Stratally bound stratified chert nodules below bedding surfaces generate closely spaced lateral heterogeneity in physical properties at stratigraphic mechanical interfaces. This generates extra complexity in natural fracture networks in addition to that caused by bed thickness and lithological physical properties. A series of representative geologically appropriate synthetic mechanical stratigraphic models were tested. Fracture networks generated in 15 DEM experiments designed to isolate and constrain the effects of nodular chert rhythmites on carbonate fracture stratigraphy are presented. The discrete element media used to model the elastic strengths of rocks contain 72,866 individual elements. Mechanical stratigraphies and the fracture networks generated are placed in a sequence stratigraphic framework. Nodular chert rhythmite successions are shown to be a distinct type of naturally fractured carbonate reservoir. Qualitative stratigraphic rules for predicting the distribution, lengths, spacing
Quantum features of natural cellular automata
NASA Astrophysics Data System (ADS)
Elze, Hans-Thomas
2016-03-01
Cellular automata can show well known features of quantum mechanics, such as a linear rule according to which they evolve and which resembles a discretized version of the Schrödinger equation. This includes corresponding conservation laws. The class of “natural” Hamiltonian cellular automata is based exclusively on integer-valued variables and couplings and their dynamics derives from an Action Principle. They can be mapped reversibly to continuum models by applying Sampling Theory. Thus, “deformed” quantum mechanical models with a finite discreteness scale l are obtained, which for l → 0 reproduce familiar continuum results. We have recently demonstrated that such automata can form “multipartite” systems consistently with the tensor product structures of nonrelativistic many-body quantum mechanics, while interacting and maintaining the linear evolution. Consequently, the Superposition Principle fully applies for such primitive discrete deterministic automata and their composites and can produce the essential quantum effects of interference and entanglement.
SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION
Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin
2003-12-01
We have developed and tested technology for a new type of direct hydrocarbon detection. The method uses inelastic rock properties to greatly enhance the sensitivity of surface seismic methods to the presence of oil and gas saturation. These methods include use of energy absorption, dispersion, and attenuation (Q) along with traditional seismic attributes like velocity, impedance, and AVO. Our approach is to combine three elements: (1) a synthesis of the latest rock physics understanding of how rock inelasticity is related to rock type, pore fluid types, and pore microstructure, (2) synthetic seismic modeling that will help identify the relative contributions of scattering and intrinsic inelasticity to apparent Q attributes, and (3) robust algorithms that extract relative wave attenuation attributes from seismic data. This project provides: (1) Additional petrophysical insight from acquired data; (2) Increased understanding of rock and fluid properties; (3) New techniques to measure reservoir properties that are not currently available; and (4) Provide tools to more accurately describe the reservoir and predict oil location and volumes. These methodologies will improve the industry's ability to predict and quantify oil and gas saturation distribution, and to apply this information through geologic models to enhance reservoir simulation. We have applied for two separate patents relating to work that was completed as part of this project.
Discrete Ramanujan transform for distinguishing the protein coding regions from other regions.
Hua, Wei; Wang, Jiasong; Zhao, Jian
2014-01-01
Based on the study of Ramanujan sum and Ramanujan coefficient, this paper suggests the concepts of discrete Ramanujan transform and spectrum. Using Voss numerical representation, one maps a symbolic DNA strand as a numerical DNA sequence, and deduces the discrete Ramanujan spectrum of the numerical DNA sequence. It is well known that of discrete Fourier power spectrum of protein coding sequence has an important feature of 3-base periodicity, which is widely used for DNA sequence analysis by the technique of discrete Fourier transform. It is performed by testing the signal-to-noise ratio at frequency N/3 as a criterion for the analysis, where N is the length of the sequence. The results presented in this paper show that the property of 3-base periodicity can be only identified as a prominent spike of the discrete Ramanujan spectrum at period 3 for the protein coding regions. The signal-to-noise ratio for discrete Ramanujan spectrum is defined for numerical measurement. Therefore, the discrete Ramanujan spectrum and the signal-to-noise ratio of a DNA sequence can be used for distinguishing the protein coding regions from the noncoding regions. All the exon and intron sequences in whole chromosomes 1, 2, 3 and 4 of Caenorhabditis elegans have been tested and the histograms and tables from the computational results illustrate the reliability of our method. In addition, we have analyzed theoretically and gotten the conclusion that the algorithm for calculating discrete Ramanujan spectrum owns the lower computational complexity and higher computational accuracy. The computational experiments show that the technique by using discrete Ramanujan spectrum for classifying different DNA sequences is a fast and effective method.
Spurious haloes and discreteness-driven relaxation in cosmological simulations
NASA Astrophysics Data System (ADS)
Power, C.; Robotham, A. S. G.; Obreschkow, D.; Hobbs, A.; Lewis, G. F.
2016-10-01
There is strong evidence that cosmological N-body simulations dominated by warm dark matter (WDM) contain spurious or unphysical haloes, most readily apparent as regularly spaced low-mass haloes strung along filaments. We show that spurious haloes are a feature of traditional N-body simulations of cosmological structure formation models, including WDM and cold dark matter models, in which gravitational collapse proceeds in an initially anisotropic fashion, and arises naturally as a consequence of discreteness-driven relaxation. We demonstrate this using controlled N-body simulations of plane-symmetric collapse and show that spurious haloes are seeded at shell crossing by localized velocity perturbations induced by the discrete nature of the density field, and that their characteristic separation should be approximately the mean inter-particle separation of the N-body simulation, which is fixed by the mass resolution within the volume. Using cosmological N-body simulations in which particles are split into two collisionless components of fixed mass ratio, we find that the spatial distribution of the two components show signatures of discreteness-driven relaxation on both large and small scales. Adopting a spline kernel gravitational softening that is of order the comoving mean inter-particle separation helps to suppress the effect of discreteness-driven relaxation, but cannot eliminate it completely. These results provide further motivation for recent developments of new algorithms, which include, for example, revisions of the traditional N-body approach by means of spatially adaptive anistropric gravitational softenings or explicit solution of the evolution of dark matter in phase space.
Milind Deo; Chung-Kan Huang; Huabing Wang
2008-08-31
Black-oil, compositional and thermal simulators have been developed to address different physical processes in reservoir simulation. A number of different types of discretization methods have also been proposed to address issues related to representing the complex reservoir geometry. These methods are more significant for fractured reservoirs where the geometry can be particularly challenging. In this project, a general modular framework for reservoir simulation was developed, wherein the physical models were efficiently decoupled from the discretization methods. This made it possible to couple any discretization method with different physical models. Oil characterization methods are becoming increasingly sophisticated, and it is possible to construct geologically constrained models of faulted/fractured reservoirs. Discrete Fracture Network (DFN) simulation provides the option of performing multiphase calculations on spatially explicit, geologically feasible fracture sets. Multiphase DFN simulations of and sensitivity studies on a wide variety of fracture networks created using fracture creation/simulation programs was undertaken in the first part of this project. This involved creating interfaces to seamlessly convert the fracture characterization information into simulator input, grid the complex geometry, perform the simulations, and analyze and visualize results. Benchmarking and comparison with conventional simulators was also a component of this work. After demonstration of the fact that multiphase simulations can be carried out on complex fracture networks, quantitative effects of the heterogeneity of fracture properties were evaluated. Reservoirs are populated with fractures of several different scales and properties. A multiscale fracture modeling study was undertaken and the effects of heterogeneity and storage on water displacement dynamics in fractured basements were investigated. In gravity-dominated systems, more oil could be recovered at a given pore
Discrete symmetries and de Sitter spacetime
Cotăescu, Ion I. Pascu, Gabriel
2014-11-24
Aspects of the ambiguity in defining quantum modes on de Sitter spacetime using a commuting system composed only of differential operators are discussed. Discrete symmetries and their actions on the wavefunction in commonly used coordinate charts are reviewed. It is argued that the system of commuting operators can be supplemented by requiring the invariance of the wavefunction to combined discrete symmetries- a criterion which selects a single state out of the α-vacuum family. Two such members of this family are singled out by particular combined discrete symmetries- states between which exists a well-known thermality relation.
Discrete flavour symmetries from the Heisenberg group
NASA Astrophysics Data System (ADS)
Floratos, E. G.; Leontaris, G. K.
2016-04-01
Non-abelian discrete symmetries are of particular importance in model building. They are mainly invoked to explain the various fermion mass hierarchies and forbid dangerous superpotential terms. In string models they are usually associated to the geometry of the compactification manifold and more particularly to the magnetised branes in toroidal compactifications. Motivated by these facts, in this note we propose a unified framework to construct representations of finite discrete family groups based on the automorphisms of the discrete and finite Heisenberg group. We focus in particular, on the PSL2 (p) groups which contain the phenomenologically interesting cases.
Effects of reservoir squeezing on quantum systems and work extraction
NASA Astrophysics Data System (ADS)
Huang, X. L.; Wang, Tao; Yi, X. X.
2012-11-01
We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when TH
Effects of reservoir squeezing on quantum systems and work extraction.
Huang, X L; Wang, Tao; Yi, X X
2012-11-01
We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when T(H)
Ultrasonic and numerical modeling of reflections from simulated fractured reservoirs
Stephen, T.; Zhu, Xiang,
1997-10-01
In order to develop modeling techniques for the characterization of fracture properties in tight gas sands from surface seismic reflection data we examine seismic waves scattered from anisotropic heterogeneity with laboratory data and numerical modeling. Laboratory models representing features of a fractured reservoir were constructed using Phenolite embedded in a Lucite background, and seismic surveys were gathered over these models. In parallel with laboratory measurement, finite-difference modeling of reflections from a fractured medium were carried out. Fracture zone properties were calculated using an effective medium theory, the variation of fracture density produced a heterogeneous medium. The heterogeneity was modeled with a stochastic process, characterized by a probability density function and an auto-correlation function. Results from both modeling efforts show that prestacked AVO data can contain important information describing reservoir heterogeneity.
Wang, F.P.; Dai, J.; Kerans, C.
1998-11-01
In part 1 of this paper, the authors discussed the rock-fabric/petrophysical classes for dolomitized carbonate-ramp rocks, the effects of rock fabric and pore type on petrophysical properties, petrophysical models for analyzing wireline logs, the critical scales for defining geologic framework, and 3-D geologic modeling. Part 2 focuses on geophysical and engineering characterizations, including seismic modeling, reservoir geostatistics, stochastic modeling, and reservoir simulation. Synthetic seismograms of 30 to 200 Hz were generated to study the level of seismic resolution required to capture the high-frequency geologic features in dolomitized carbonate-ramp reservoirs. Outcrop data were collected to investigate effects of sampling interval and scale-up of block size on geostatistical parameters. Semivariogram analysis of outcrop data showed that the sill of log permeability decreases and the correlation length increases with an increase of horizontal block size. Permeability models were generated using conventional linear interpolation, stochastic realizations without stratigraphic constraints, and stochastic realizations with stratigraphic constraints. Simulations of a fine-scale Lawyer Canyon outcrop model were used to study the factors affecting waterflooding performance. Simulation results show that waterflooding performance depends strongly on the geometry and stacking pattern of the rock-fabric units and on the location of production and injection wells.
Modern Reservoir Sedimentation Management Techniques with Examples
NASA Astrophysics Data System (ADS)
Annandale, G. W.
2014-12-01
Implementation of reservoir sedimentation management approaches results in a win-win scenario, it assists in enhancing the environment by preserving river function downstream of dams while concurrently providing opportunities to sustainably manage water resource infrastructure. This paper summarizes the most often used reservoir sedimentation management techniques with examples of where they have been implemented. Three categories can be used to classify these technologies, i.e. catchment management, sediment routing and sediment removal. The objective of catchment management techniques is to minimize the amount of sediment that may discharge into a reservoir, thereby reducing the loss of storage space due to sedimentation. Reservoir routing is a set of techniques that aim at minimizing the amount of sediment that may deposit in a reservoir, thereby maximizing the amount of sediment that may be passed downstream. The third group consists of techniques that may be used to remove previously deposited sediment from reservoirs. The selection of reservoir sedimentation management approaches is site specific and depends on various factors, including dam height, reservoir volume, reservoir length, valley shape, valley slope, sediment type and hydrology. Description of the different reservoir sedimentation management techniques that are used in practice will be accompanied by case studies, including video, illustrating criteria that may be used to determine the potential success of implementing the techniques.
Storage capacity in hot dry rock reservoirs
Brown, D.W.
1997-11-11
A method is described for extracting thermal energy, in a cyclic manner, from geologic strata which may be termed hot dry rock. A reservoir comprised of hot fractured rock is established and water or other liquid is passed through the reservoir. The water is heated by the hot rock, recovered from the reservoir, cooled by extraction of heat by means of heat exchange apparatus on the surface, and then re-injected into the reservoir to be heated again. Water is added to the reservoir by means of an injection well and recovered from the reservoir by means of a production well. Water is continuously provided to the reservoir and continuously withdrawn from the reservoir at two different flow rates, a base rate and a peak rate. Increasing water flow from the base rate to the peak rate is accomplished by rapidly decreasing backpressure at the outlet of the production well in order to meet periodic needs for amounts of thermal energy greater than a baseload amount, such as to generate additional electric power to meet peak demands. The rate of flow of water provided to the hot dry rock reservoir is maintained at a value effective to prevent depletion of the liquid inventory of the reservoir. 4 figs.
Longitudinal gradients along a reservoir cascade
Miranda, L.E.; Habrat, M.D.; Miyazono, S.
2008-01-01
Reservoirs have traditionally been regarded as spatially independent entities rather than as longitudinal segments of a river system that are connected upstream and downstream to the river and other reservoirs. This view has frustrated advancement in reservoir science by impeding adequate organization of available information and by hindering interchanges with allied disciplines that often consider impounded rivers at the basin scale. We analyzed reservoir morphology, water quality, and fish assemblage data collected in 24 reservoirs of the Tennessee River; we wanted to describe longitudinal changes occurring at the scale of the entire reservoir series (i.e., cascade) and to test the hypothesis that fish communities and environmental factors display predictable gradients like those recognized for unimpounded rivers. We used a data set collected over a 7-year period; over 3 million fish representing 94 species were included in the data set. Characteristics such as reservoir mean depth, relative size of the limnetic zone, water retention time, oxygen stratification, thermal stratification, substrate size, and water level fluctuations increased in upstream reservoirs. Conversely, reservoir area, extent of riverine and littoral zones, access to floodplains and associated wetlands, habitat diversity, and nutrient and sediment inputs increased in downstream reservoirs. Upstream reservoirs included few, largely lacustrine, ubiquitous fish taxa that were characteristic of the lentic upper reaches of the basin. Fish species richness increased in a downstream direction from 12 to 67 species/ reservoir as riverine species became more common. Considering impoundments at a basin scale by viewing them as sections in a river or links in a chain may generate insight that is not always available when the impoundments are viewed as isolated entities. Basin-scale variables are rarely controllable but constrain the expression of processes at smaller scales and can facilitate the
Comparing the Discrete and Continuous Logistic Models
ERIC Educational Resources Information Center
Gordon, Sheldon P.
2008-01-01
The solutions of the discrete logistic growth model based on a difference equation and the continuous logistic growth model based on a differential equation are compared and contrasted. The investigation is conducted using a dynamic interactive spreadsheet. (Contains 5 figures.)
Dynamic discretization method for solving Kepler's equation
NASA Astrophysics Data System (ADS)
Feinstein, Scott A.; McLaughlin, Craig A.
2006-09-01
Kepler’s equation needs to be solved many times for a variety of problems in Celestial Mechanics. Therefore, computing the solution to Kepler’s equation in an efficient manner is of great importance to that community. There are some historical and many modern methods that address this problem. Of the methods known to the authors, Fukushima’s discretization technique performs the best. By taking more of a system approach and combining the use of discretization with the standard computer science technique known as dynamic programming, we were able to achieve even better performance than Fukushima. We begin by defining Kepler’s equation for the elliptical case and describe existing solution methods. We then present our dynamic discretization method and show the results of a comparative analysis. This analysis will demonstrate that, for the conditions of our tests, dynamic discretization performs the best.
Running Parallel Discrete Event Simulators on Sierra
Barnes, P. D.; Jefferson, D. R.
2015-12-03
In this proposal we consider porting the ROSS/Charm++ simulator and the discrete event models that run under its control so that they run on the Sierra architecture and make efficient use of the Volta GPUs.
A Few Continuous and Discrete Dynamical Systems
NASA Astrophysics Data System (ADS)
Zhang, Yufeng; Rui, Wenjuan
2016-08-01
Starting from a 2-unimodular group, we construct its new Lie algebras for which the positive-order Lax pairs and the negative-order Lax pairs are introduced, respectively. With the help of the resulting structure equation of the group we generate some partial differential equations including the well-known MKdV equation, the sine-Gordon equation, the hyperbolic sine-Gordon equation and other new nonlinear evolution equations. With the aid of the Tu scheme combined with the given Lax pairs, we obtain the isospectral and nonisospectral hierarchies of evolution equations, from which we generate two sets of symmetries of a generalized nonlinear Schrödinger (gNLS) equation. Finally, we discretize the Lax pairs to obtain a set of coupled semi-discrete equations. As their reduction, we produce the semi-discrete MKdV equation and semi-discrete NLS equation.
Motion of Discrete Interfaces Through Mushy Layers
NASA Astrophysics Data System (ADS)
Braides, Andrea; Solci, Margherita
2016-08-01
We study the geometric motion of sets in the plane derived from the homogenization of discrete ferromagnetic energies with weak inclusions. We show that the discrete sets are composed by a `bulky' part and an external `mushy region' composed only of weak inclusions. The relevant motion is that of the bulky part, which asymptotically obeys to a motion by crystalline mean curvature with a forcing term, due to the energetic contribution of the mushy layers, and pinning effects, due to discreteness. From an analytical standpoint, it is interesting to note that the presence of the mushy layers implies only a weak and not strong convergence of the discrete motions, so that the convergence of the energies does not commute with the evolution. From a mechanical standpoint it is interesting to note the geometrical similarity of some phenomena in the cooling of binary melts.
Vortex chains travelling with discrete velocities
NASA Astrophysics Data System (ADS)
Malishevskii, A. S.; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.
2008-05-01
It has been shown that Swihart waves slowing down caused by Josephson junction spatial dispersion leads to the new field periodic nonlinear vortex states moving with discrete velocities. Swihart waves trapping by periodic vortex structures is discovered.
Discrete breathers in nonlinear magnetic metamaterials.
Lazarides, N; Eleftheriou, M; Tsironis, G P
2006-10-13
Magnetic metamaterials composed of split-ring resonators or U-type elements may exhibit discreteness effects in THz and optical frequencies due to weak coupling. We consider a model one-dimensional metamaterial formed by a discrete array of nonlinear split-ring resonators where each ring interacts with its nearest neighbors. On-site nonlinearity and weak coupling among the individual array elements result in the appearance of discrete breather excitations or intrinsic localized modes, both in the energy-conserved and the dissipative system. We analyze discrete single and multibreather excitations, as well as a special breather configuration forming a magnetization domain wall and investigate their mobility and the magnetic properties their presence induces in the system.
The discrete-time compensated Kalman filter
NASA Technical Reports Server (NTRS)
Lee, W. H.; Athans, M.
1978-01-01
A suboptimal dynamic compensator to be used in conjunction with the ordinary discrete time Kalman filter was derived. The resultant compensated Kalman Filter has the property that steady state bias estimation errors, resulting from modelling errors, were eliminated.
Radix Representation of Triangular Discrete Grid System
NASA Astrophysics Data System (ADS)
Ben, J.; Li, Y. L.; Wang, R.
2016-11-01
Discrete Global Grid Systems (DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. It provides an organizational structure that permits fast integration between multiple sources of large and variable geospatial data. Although many endeavors have been done to describe certain discrete grid systems, there still lack of a uniform mathematical framework for them. This paper simplifies the planar class I aperture 4 triangular discrete grid system into a hierarchical lattice model which is proved to be a radix system in the complex number plane. Mathematical properties of the radix system reveal the discrete grid system is equivalent to the set of complex numbers with special form. The conclusion provides a potential way to build a uniform mathematical framework of DGGS and can be used to design efficient encoding and spatial operation scheme for DGGS.
Liao, Chin-Wen; Lu, Chien-Yu
2011-06-01
The state estimation problem for discrete-time recurrent neural networks with both interval discrete and infinite-distributed time-varying delays is studied in this paper, where interval discrete time-varying delay is in a given range. The activation functions are assumed to be globally Lipschitz continuous. A delay-dependent condition for the existence of state estimators is proposed based on new bounding techniques. Via solutions to certain linear matrix inequalities, general full-order state estimators are designed that ensure globally asymptotic stability. The significant feature is that no inequality is needed for seeking upper bounds for the inner product between two vectors, which can reduce the conservatism of the criterion by employing the new bounding techniques. Two illustrative examples are given to demonstrate the effectiveness and applicability of the proposed approach.
Vertical distribution of the subsurface microorganisms in Sagara oil reservoir
NASA Astrophysics Data System (ADS)
Nunoura, T.; Oida, H.; Masui, N.; Ingaki, F.; Takai, K.; Nealson, K. H.; Horikoshi, K.
2002-12-01
The recent microbiological studies reported that active microbial habitat for methanogen, sulfate reducers (Archaeoglobus, d-Proteobacteria, gram positives), fermenters (Thermococcus, Thermotogales, gram positives etc.) and other heterotrophs (g-Proteobacteria etc.) are in subsurface petroleum oil reservoirs. However, microbial distribution at vertical distances in depth has not been demonstrated since the samples in previous studies are only to use oil and the formation water. Here, we show the vertical profile of microbial community structure in Japanese terrestrial oil reservoir by a combination of molecular ecological analyses and culture dependent studies. The sequential WRC (Whole Round Core) samples (200 mbsf) were recovered from a drilling project for Sagara oil reservoir, Shizuoka Prefecture, Japan, conducted in Jar. -Mar. 2002. The lithology of the core samples was composed of siltstone, sandstone, or partially oil containing sand. The major oil components were gasoline, kerosene and light oil, that is a unique feature observed in the Sagara oil reservoir. The direct count of DAPI-stained cells suggested that the biomass was relatively constant, 1.0x104cells/g through the core of the non-oil layers, whereas the oil-bearing layers had quite higher population density at a range of 1.0x105 ? 3.7x107cells/g. The vertical profile of microbial community structures was analyzed by the sequence similarity analysis, phylogenetic analysis and T-RFLP fingerprinting of PCR-amplified 16S rDNA. From bacterial rDNA clone libraries, most of the examined rDNA were similar with the sequence of genera Pseudomanas, Stenotrophomonas and Sphingomonas within g-Proteobacteria. Especially, Pseudomonas stutzeri was predominantly present in all oil-bearing layers. From archaeal rDNA clone libraries, all rDNA clone sequences were phylogenetically associated with uncultured soil group in Crenarchaeota. We detected none of the sequences of sulfate reducers, sulfur dependent fermenters
ERIC Educational Resources Information Center
Kennelly, Brendan; Flannery, Darragh; Considine, John; Doherty, Edel; Hynes, Stephen
2014-01-01
This paper outlines how a discrete choice experiment (DCE) can be used to learn more about how students are willing to trade off various features of assignments such as the nature and timing of feedback and the method used to submit assignments. A DCE identifies plausible levels of the key attributes of a good or service and then presents the…
Discrete mechanics, "time machines" and hybrid systems
NASA Astrophysics Data System (ADS)
Elze, Hans-Thomas
2013-09-01
Modifying the discrete mechanics proposed by T.D. Lee, we construct a class of discrete classical Hamiltonian systems, in which time is one of the dynamical variables. This includes a toy model of "time machines" which can travel forward and backward in time and which differ from models based on closed timelike curves (CTCs). In the continuum limit, we explore the interaction between such time reversing machines and quantum mechanical objects, employing a recent description of quantum-classical hybrids.
Discrete Surface Modelling Using Partial Differential Equations.
Xu, Guoliang; Pan, Qing; Bajaj, Chandrajit L
2006-02-01
We use various nonlinear partial differential equations to efficiently solve several surface modelling problems, including surface blending, N-sided hole filling and free-form surface fitting. The nonlinear equations used include two second order flows, two fourth order flows and two sixth order flows. These nonlinear equations are discretized based on discrete differential geometry operators. The proposed approach is simple, efficient and gives very desirable results, for a range of surface models, possibly having sharp creases and corners.
Terminal Dynamics Approach to Discrete Event Systems
NASA Technical Reports Server (NTRS)
Zak, Michail; Meyers, Ronald
1995-01-01
This paper presents and discusses a mathematical formalism for simulation of discrete event dynamic (DED)-a special type of 'man-made' systems to serve specific purposes of information processing. The main objective of this work is to demonstrate that the mathematical formalism for DED can be based upon a terminal model of Newtonian dynamics which allows one to relax Lipschitz conditions at some discrete points.!.
NASA Astrophysics Data System (ADS)
Maity, Debotyam
This study is aimed at an improved understanding of unconventional reservoirs which include tight reservoirs (such as shale oil and gas plays), geothermal developments, etc. We provide a framework for improved fracture zone identification and mapping of the subsurface for a geothermal system by integrating data from different sources. The proposed ideas and methods were tested primarily on data obtained from North Brawley geothermal field and the Geysers geothermal field apart from synthetic datasets which were used to test new algorithms before actual application on the real datasets. The study has resulted in novel or improved algorithms for use at specific stages of data acquisition and analysis including improved phase detection technique for passive seismic (and teleseismic) data as well as optimization of passive seismic surveys for best possible processing results. The proposed workflow makes use of novel integration methods as a means of making best use of the available geophysical data for fracture characterization. The methodology incorporates soft computing tools such as hybrid neural networks (neuro-evolutionary algorithms) as well as geostatistical simulation techniques to improve the property estimates as well as overall characterization efficacy. The basic elements of the proposed characterization workflow involves using seismic and microseismic data to characterize structural and geomechanical features within the subsurface. We use passive seismic data to model geomechanical properties which are combined with other properties evaluated from seismic and well logs to derive both qualitative and quantitative fracture zone identifiers. The study has resulted in a broad framework highlighting a new technique for utilizing geophysical data (seismic and microseismic) for unconventional reservoir characterization. It provides an opportunity to optimally develop the resources in question by incorporating data from different sources and using their temporal
Ramakrishnan, A G; Abhiram, B; Prasanna, S R Mahadeva
2015-06-01
A characterization of the voice source (VS) signal by the pitch synchronous (PS) discrete cosine transform (DCT) is proposed. With the integrated linear prediction residual (ILPR) as the VS estimate, the PS DCT of the ILPR is evaluated as a feature vector for speaker identification (SID). On TIMIT and YOHO databases, using a Gaussian mixture model (GMM)-based classifier, it performs on par with existing VS-based features. On the NIST 2003 database, fusion with a GMM-based classifier using MFCC features improves the identification accuracy by 12% in absolute terms, proving that the proposed characterization has good promise as a feature for SID studies.
Paulsson, B.N.P.
1997-08-01
Single-well seismology, Reverse Vertical Seismic Profiles (VSP`s) and Crosswell seismology are three new seismic techniques that we jointly refer to as borehole seismology. Borehole seismic techniques are of great interest because they can obtain much higher resolution images of oil and gas reservoirs than what is obtainable with currently used seismic techniques. The quality of oil and gas reservoir management decisions depend on the knowledge of both the large and the fine scale features in the reservoirs. Borehole seismology is capable of mapping reservoirs with an order of magnitude improvement in resolution compared with currently used technology. In borehole seismology we use a high frequency seismic source in an oil or gas well and record the signal in the same well, in other wells, or on the surface of the earth.
[Zoonotic diseases caused by bacteria of the genus Bartonella genus: new reservoirs ? New vectors?].
Chomel, Bruno B; Boulouis, Henri-Jean
2005-03-01
Domestic animals and wildlife represent a large reservoir for bartonellae, at least eight species or subspecies of which have been reported to cause zoonotic infections. In addition, numerous orphan clinical syndromes are now being attributed to Bartonella henselae infection. Many mammalian species, including cats, dogs, rodents and ruminants are the main bartonellae reservoirs. Cats are the main reservoir for B. henselae. It appears that domestic dogs, at least in non tropical regions, are more likely to be accidental hosts than reservoirs, and constitute excellent sentinels for human infections. Bartonellae are vector-borne bacteria. The mode of B. henselae transmission by cat fleas is now better understood, but new potential vectors have recently been identified, including ticks and biting flies. This articles summarizes current knowledge of the etiology, new clinical features and epidemiological characteristics of these emerging zoonoses.
Healthcare Outbreaks Associated With a Water Reservoir and Infection Prevention Strategies.
Kanamori, Hajime; Weber, David J; Rutala, William A
2016-06-01
Hospital water may serve as a reservoir of healthcare-associated pathogens, and contaminated water can lead to outbreaks and severe infections. The clinical features of waterborne outbreaks and infections as well as prevention strategies and control measures are reviewed. The common waterborne pathogens were bacteria, including Legionella and other gram-negative bacteria, and nontuberculous mycobacteria, although fungi and viruses were occasionally described. These pathogens caused a variety of infections, including bacteremia and invasive and disseminated diseases, particularly among immunocompromised hosts and critically ill adults as well as neonates. Waterborne outbreaks occurred in healthcare settings with emergence of new reported reservoirs, including electronic faucets (Pseudomonas aeruginosa and Legionella), decorative water wall fountains (Legionella), and heater-cooler devices used in cardiac surgery (Mycobacterium chimaera). Advanced molecular techniques are useful for achieving a better understanding of reservoirs and transmission pathways of waterborne pathogens. Developing prevention strategies based on water reservoirs provides a practical approach for healthcare personnel.
Discrete mappings with an explicit discrete Lyapunov function related to integrable mappings
NASA Astrophysics Data System (ADS)
Inoue, Hironori; Takahashi, Daisuke; Matsukidaira, Junta
2006-05-01
We propose discrete mappings of second order that have a discrete analogue of Lyapunov function. The mappings are extensions of the integrable Quispel-Roberts-Thompson (QRT) mapping, and a discrete Lyapunov function of the mappings is identical to an explicit conserved quantity of the QRT mapping. Moreover we can obtain a differential and an ultradiscrete limit of the mappings preserving the existence of Lyapunov function. We also give applications of a mapping with an adjusted parameter, a probabilistic mapping and coupled mappings.
Uncertainty analysis for water supply reservoir yields
NASA Astrophysics Data System (ADS)
Kuria, Faith; Vogel, Richard
2015-10-01
Understanding the variability of water supply reservoir yields is central for planning purposes. The basis of this study is an empirical global relationship between reservoir storage capacity, water supply yield and reliability based on a global database of 729 rivers. Monte Carlo simulations reveal that the coefficient of variation of estimates of water supply reservoir yields depend only on the length of streamflows record and the coefficient of variation of the streamflows used to estimate the yield. We compare the results of those Monte Carlo experiments with an analytical uncertainty method First Order Variance Approximation (FOVA). FOVA is shown to produce a general, accurate and useful expression for estimating the coefficient of variation of water supply reservoir yield estimates. We also document how the FOVA analytical model can be used to determine the minimum length of streamflow record required during the design of water supply reservoirs so as to ensure that the yield delivered from reservoir falls within a prespecified margin of error.
Quantization of systems with temporally varying discretization. I. Evolving Hilbert spaces
Höhn, Philipp A.
2014-08-15
A temporally varying discretization often features in discrete gravitational systems and appears in lattice field theory models subject to a coarse graining or refining dynamics. To better understand such discretization changing dynamics in the quantum theory, an according formalism for constrained variational discrete systems is constructed. While this paper focuses on global evolution moves and, for simplicity, restricts to flat configuration spaces R{sup N}, a Paper II [P. A. Höhn, “Quantization of systems with temporally varying discretization. II. Local evolution moves,” J. Math. Phys., e-print http://arxiv.org/abs/arXiv:1401.7731 [gr-qc].] discusses local evolution moves. In order to link the covariant and canonical picture, the dynamics of the quantum states is generated by propagators which satisfy the canonical constraints and are constructed using the action and group averaging projectors. This projector formalism offers a systematic method for tracing and regularizing divergences in the resulting state sums. Non-trivial coarse graining evolution moves lead to non-unitary, and thus irreversible, projections of physical Hilbert spaces and Dirac observables such that these concepts become evolution move dependent on temporally varying discretizations. The formalism is illustrated in a toy model mimicking a “creation from nothing.” Subtleties arising when applying such a formalism to quantum gravity models are discussed.
NASA Astrophysics Data System (ADS)
Mighell, K. J.
2004-12-01
I describe the key features of my MATPHOT algorithm for accurate and precise stellar photometry and astrometry using discrete Point Spread Functions. A discrete Point Spread Function (PSF) is a sampled version of a continuous two-dimensional PSF. The shape information about the photon scattering pattern of a discrete PSF is typically encoded using a numerical table (matrix) or a FITS image file. The MATPHOT algorithm shifts discrete PSFs within an observational model using a 21-pixel-wide damped sinc function and position partial derivatives are computed using a five-point numerical differentiation formula. The MATPHOT algorithm achieves accurate and precise stellar photometry and astrometry of undersampled CCD observations by using supersampled discrete PSFs that are sampled 2, 3, or more times more finely than the observational data. I have written a C-language computer program called MPD which is based on the current implementation of the MATPHOT algorithm; all source code and documentation for MPD and support software is freely available at the following website: http://www.noao.edu/staff/mighell/matphot . I demonstrate the use of MPD and present a detailed MATPHOT analysis of simulated James Webb Space Telescope observations which demonstrates that millipixel relative astrometry and millimag photometric accuracy is achievable with very complicated space-based discrete PSFs. This work was supported by a grant from the National Aeronautics and Space Administration (NASA), Interagency Order No. S-13811-G, which was awarded by the Applied Information Systems Research (AISR) Program of NASA's Science Mission Directorate.
Discrete Wavelength-Locked External Cavity Laser
NASA Technical Reports Server (NTRS)
Pilgrim, Jeffrey S.; Silver, Joel A.
2004-01-01
A prototype improved external cavity laser (ECL) was demonstrated in the second phase of a continuing effort to develop wavelength-agile lasers for fiber-optic communications and trace-gas-sensing applications. This laser is designed to offer next-generation performance for incorporation into fiber-optic networks. By eliminating several optical components and simplifying others used in prior designs, the design of this laser reduces costs, making lasers of this type very competitive in a price-sensitive market. Diode lasers have become enabling devices for fiber optic networks because of their cost, compactness, and spectral properties. ECLs built around diode laser gain elements further enhance capabilities by virtue of their excellent spectral properties with significantly increased (relative to prior lasers) wavelength tuning ranges. It is essential to exploit the increased spectral coverage of ECLs while simultaneously insuring that they operate only at precisely defined communication channels (wavelengths). Heretofore, this requirement has typically been satisfied through incorporation of add-in optical components that lock the ECL output wavelengths to these specific channels. Such add-in components contribute substantially to the costs of ECL lasers to be used as sources for optical communication networks. Furthermore, the optical alignment of these components, needed to attain the required wavelength precision, is a non-trivial task and can contribute substantially to production costs. The design of the present improved ECL differs significantly from the designs of prior ECLs. The present design relies on inherent features of components already included within an ECL, with slight modifications so that these components perform their normal functions while simultaneously effecting locking to the required discrete wavelengths. Hence, add-in optical components and the associated cost of alignment can be eliminated. The figure shows the locking feedback signal
A virtual company concept for reservoir management
Martin, F.D.; Kendall, R.P.; Whitney, E.M.
1998-12-31
This paper describes how reservoir management problems were pursued with a virtual company concept via the Internet and World Wide Web. The focus of the paper is on the implementation of virtual asset management teams that were assembled with small independent oil companies. The paper highlights the mechanics of how the virtual team transferred data and interpretations, evaluated geological models of complex reservoirs, and used results of simulation studies to analyze various reservoir management strategies.
NASA Astrophysics Data System (ADS)
Chen, Wei; Simonetti, Antonio
2015-02-01
The exact mantle source for carbonatite melts remains highly controversial. Despite their predominant occurrence within continental (lithospheric) domains, the radiogenic isotope data from young (< 200 Ma) carbonatite complexes worldwide overlap the fields defined by present-day oceanic island basalts (OIBs). This feature suggests an intimate petrogenetic relationship with asthenospheric mantle. New Pb, Sr, C, and O isotopic data are reported here for constituent minerals from the Oka carbonatite complex, which is associated with the Cretaceous Monteregian Igneous Province (MIP), northeastern North America. The Pb isotope data define linear arrays in Pb-Pb isotope diagrams, with the corresponding Sr isotope ratios being highly variable (0.70314-0.70343); both these features are consistent with open system behavior involving at least three distinct mantle reservoirs. Compared to the isotope composition of known mantle sources for OIBs and carbonatite occurrences worldwide, the least radiogenic 207Pb/204Pb (14.96 ± 0.07) and 208Pb/204Pb (37.29 ± 0.15) isotopic compositions relative to their corresponding 206Pb/204Pb ratios (18.86 ± 0.08) reported here are distinct, and indicate the involvement of an ancient depleted mantle (ADM) source. The extremely unradiogenic Pb isotope compositions necessitate U/Pb fractionation early in Earth's history (prior to 4.0 Ga ago) and growth via a multi-stage Pb evolution model. The combined stable (C and O) and radiogenic isotopic compositions effectively rule out crustal/lithosphere contamination during the petrogenetic history of the Oka complex. Instead, the isotopic variations reported here most likely result from the mixing of discrete, small volume partial melts derived from a heterogeneous plume source characterized by a mixed HIMU-EM1-ADM signature.
Storage capacity in hot dry rock reservoirs
Brown, Donald W.
1997-01-01
A method of extracting thermal energy, in a cyclic manner, from geologic strata which may be termed hot dry rock. A reservoir comprised of hot fractured rock is established and water or other liquid is passed through the reservoir. The water is heated by the hot rock, recovered from the reservoir, cooled by extraction of heat by means of heat exchange apparatus on the surface, and then re-injected into the reservoir to be heated again. Water is added to the reservoir by means of an injection well and recovered from the reservoir by means of a production well. Water is continuously provided to the reservoir and continuously withdrawn from the reservoir at two different flow rates, a base rate and a peak rate. Increasing water flow from the base rate to the peak rate is accomplished by rapidly decreasing backpressure at the outlet of the production well in order to meet periodic needs for amounts of thermal energy greater than a baseload amount, such as to generate additional electric power to meet peak demands. The rate of flow of water provided to the hot dry rock reservoir is maintained at a value effective to prevent depletion of the liquid
Geothermal reservoirs in hydrothermal convection systems
Sorey, M.L.
1982-01-01
Geothermal reservoirs commonly exist in hydrothermal convection systems involving fluid circulation downward in areas of recharge and upwards in areas of discharge. Because such reservoirs are not isolated from their surroundings, the nature of thermal and hydrologic connections with the rest of the system may have significant effects on the natural state of the reservoir and on its response to development. Conditions observed at numerous developed and undeveloped geothermal fields are discussed with respect to a basic model of the discharge portion of an active hydrothermal convection system. Effects of reservoir development on surficial discharge of thermal fluid are also delineated.
Flow Characterization in Naturally Fractured Reservoirs
NASA Astrophysics Data System (ADS)
Alajmi, A.; Gharbi, R.
2008-12-01
Most hydrocarbon reservoirs are fractured in nature with various degrees of fracture intensities. With the current oil prices and growing demand for oil, a great interest is built in the petroleum industry to characterize partially fractured reservoirs and to develop an increased understanding of the physics of fluid flow in these types of reservoirs. This is due to the fact that fractured reservoirs have different performance behavior and high potential for oil recovery than conventional reservoirs. Therefore, prediction and understanding of fluid displacement in these reservoirs is very much critical in the decision on the applicability of oil recovery methods. Using a finite difference numerical simulator, this study investigated the effect of reservoir fracture intensities on the displacement behavior. Several heterogeneous permeable media, each with different probability of fracture intensity, were generated stochastically. The fracture intensity covers reservoirs with no fracture (zero fracture intensity) to fully fractured reservoirs (fracture intensity of 1). In order to better describe and model fractured reservoirs, a dual porosity-dual permeability model was built. Extensive simulations of water displacing oil were then performed in each of the generated fractured models for different well configurations. The objective was to determine the functional relationships between the displacement performance, fracture intensities, and well configurations. The study has resulted in significant new insights into the flow characterization in naturally fractured reservoirs. Results show that the reservoir fracture intensity has considerable effects on the efficiency of fluid displacement in naturally fractured reservoirs. A critical value of reservoir fracture intensity appears to sort favorable from unfavorable displacement, causing the displacement to be either fracture-dominated or matrix-dominated. The conditions under which fluid displacement may yield better
Pope, G.A.; Sepehrnoori, K.; Delshad, M.; Ferreira, L.; Gupta, A.; Maroongroge, V.
1994-11-01
This is the final report of a three year research project on the use of tracers for reservoir characterization. The objective of this research was to develop advanced, innovative techniques for the description of reservoir characteristics using both single-well backflow and interwell tracer tests. (1) The authors implemented and validated tracer modeling features in a compositional simulator (UTCOMP). (2) They developed and applied a new single well tracer test for estimating reservoir heterogeneity. (3) They developed and applied a new single well tracer test for estimating reservoir wettability in-situ. (4) They developed a new, simple and efficient method to analyze two well tracer tests based upon type curve matching and illustrated its use with actual field tracer data. (5) They developed a new method for deriving an integrated reservoir description based upon combinatorial optimization schemes. (6) They developed a new, interwell tracer test for reservoir heterogeneity called vertical tracer profiling (VTP) and demonstrated its advantages over conventional interwell tracer testing. (7) They developed a simple and easy analytical method to estimate swept pore volume from interwell tracer data and showed both the theoretical basis for this method and its practical utility. (8) They made numerous enhancements to our compositional reservoir simulator such as including the full permeability tensor, adding faster solvers, improving its speed and robustness and making it easier to use (better I/0) for tracer simulation problems. (9) They applied the enhanced version of UTCOMP to the analysis of interwell tracer data using perfluorocarbons at Elks Hill Naval Petroleum Reserve. All of these accomplishments taken together have significantly improved the state of reservoir tracer technology and have demonstrated that it is a far more powerful and useful tool for quantitative reservoir characterization than previously realized or practiced by the industry.
NASA Astrophysics Data System (ADS)
Cunha, Davi Gasparini Fernandes; Benassi, Simone Frederigi; de Falco, Patrícia Bortoletto; do Carmo Calijuri, Maria
2016-03-01
Artificial reservoirs have been used for drinking water supply, other human activities, flood control and pollution abatement worldwide, providing overall benefits to downstream water quality. Most reservoirs in Brazil were built during the 1970s, but their long-term patterns of trophic status, water chemistry, and nutrient removal are still not very well characterized. We aimed to evaluate water quality time series (1985-2010) data from the riverine and lacustrine zones of the transboundary Itaipu Reservoir (Brazil/Paraguay). We examined total phosphorus and nitrogen, chlorophyll a concentrations, water transparency, and phytoplankton density to look for spatial and temporal trends and correlations with trophic state evolution and nutrient retention. There was significant temporal and spatial water quality variation ( P < 0.01, ANCOVA). The results indicated that the water quality and structure of the reservoir were mainly affected by one internal force (hydrodynamics) and one external force (upstream cascading reservoirs). Nutrient and chlorophyll a concentrations tended to be lower in the lacustrine zone and decreased over the 25-year timeframe. Reservoir operational features seemed to be limiting primary production and phytoplankton development, which exhibited a maximum density of 6050 org/mL. The relatively small nutrient concentrations in the riverine zone were probably related to the effect of the cascade reservoirs upstream of Itaipu and led to relatively low removal percentages. Our study suggested that water quality problems may be more pronounced immediately after the filling phase of the artificial reservoirs, associated with the initial decomposition of drowned vegetation at the very beginning of reservoir operation.
Cunha, Davi Gasparini Fernandes; Benassi, Simone Frederigi; de Falco, Patrícia Bortoletto; Calijuri, Maria do Carmo
2016-03-01
Artificial reservoirs have been used for drinking water supply, other human activities, flood control and pollution abatement worldwide, providing overall benefits to downstream water quality. Most reservoirs in Brazil were built during the 1970s, but their long-term patterns of trophic status, water chemistry, and nutrient removal are still not very well characterized. We aimed to evaluate water quality time series (1985-2010) data from the riverine and lacustrine zones of the transboundary Itaipu Reservoir (Brazil/Paraguay). We examined total phosphorus and nitrogen, chlorophyll a concentrations, water transparency, and phytoplankton density to look for spatial and temporal trends and correlations with trophic state evolution and nutrient retention. There was significant temporal and spatial water quality variation (P < 0.01, ANCOVA). The results indicated that the water quality and structure of the reservoir were mainly affected by one internal force (hydrodynamics) and one external force (upstream cascading reservoirs). Nutrient and chlorophyll a concentrations tended to be lower in the lacustrine zone and decreased over the 25-year timeframe. Reservoir operational features seemed to be limiting primary production and phytoplankton development, which exhibited a maximum density of 6050 org/mL. The relatively small nutrient concentrations in the riverine zone were probably related to the effect of the cascade reservoirs upstream of Itaipu and led to relatively low removal percentages. Our study suggested that water quality problems may be more pronounced immediately after the filling phase of the artificial reservoirs, associated with the initial decomposition of drowned vegetation at the very beginning of reservoir operation.
NASA Astrophysics Data System (ADS)
Felici, Fabrizio; Alemanni, Annalisa; Bouacida, Djamil; de Montleau, Pierre
2016-10-01
Fault arrays and natural fractures distribution strongly influence subsurface fluids migration, trapping and production. It is critical to develop methodologies that can be used to accurately characterize reservoir volumes as present-day exploration and appraisal campaigns become increasingly focused on tight or low porosity reservoirs. A common method used to model the distribution and intensity of subsurface fracture sets is the Discrete Fracture Network (DFN) technique. Shortcomings of the DFN technique include the evaluation of fracture attributes, computational aspects in the case of large fields, and most importantly issues related to upscaling. Thus, the aim of this work is to present a simplified methodology for fractured reservoir characterization based on the distribution of fracture intensity as a continuous property. Fracture intensity was calculated from image well-logs data and then distributed in the reservoir according to specific fracture drivers. The case study is related to a large appraisal gas field located in the Illizi Basin, Southern Algeria, where Late Ordovician glacial deposits are the primary reservoir levels, in which the presence of faults and fractures strongly enhance well performances. The final fracture intensity model was obtained by implementing a workflow in a commonly used commercial geomodeling software and calibrated by means of well test data analysis. The implemented methodology is a useful tool for large fractured reservoir characterization when DFN technique is hardly applicable for computational reasons or the level of uncertainty does not support a performing discrete analysis.
Seleson, Pablo; Du, Qiang; Parks, Michael L.
2016-08-16
The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of suchmore » discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest
PREFACE: 4th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE2014)
NASA Astrophysics Data System (ADS)
Di Domenico, Antonio; Mavromatos, Nick E.; Mitsou, Vasiliki A.; Skliros, Dimitri P.
2015-07-01
The DISCRETE 2014: Fourth Symposium in the Physics of Discrete Symmetries took place at King's College London, Strand Campus, London WC2R 2LS, from Tuesday, December 2 2014 till Saturday, December 6 2014. This is the fourth Edition of the DISCRETE conference series, which is a biannual event, having been held previously in Valencia (Discrete'08), Rome (Discrete2010) and Lisbon (Discrete2012). The topics covered at the DISCRETE series of conferences are: T, C, P, CP symmetries; accidental symmetries (B, L conservation); CPT symmetry, decoherence and entangled states, Lorentz symmetry breaking (phenomenology and current bounds); neutrino mass and mixing; implications for cosmology and astroparticle physics, dark matter searches; experimental prospects at LHC, new facilities. In DISCRETE 2014 we have also introduced two new topics: cosmological aspects of non-commutative space-times as well as PT symmetric Hamiltonians (non-Hermitian but with real eigenvalues), a topic that has wide applications in particle physics and beyond. The conference was opened by the King's College London Vice Principal on Research and Innovation, Mr Chris Mottershead, followed by a welcome address by the Chair of DISCRETE 2014 (Professor Nick E. Mavromatos). After these introductory talks, the scientific programme of the DISCRETE 2014 symposium started. Following the tradition of DISCRETE series of conferences, the talks (138 in total) were divided into plenary-review talks (25), invited research talks (50) and shorter presentations (63) — selected by the conveners of each session in consultation with the organisers — from the submitted abstracts. We have been fortunate to have very high-quality, thought stimulating and interesting talks at all levels, which, together with the discussions among the participants, made the conference quite enjoyable. There were 152 registered participants for the event.
Fredrich, J.T.; Argueello, J.G.; Thorne, B.J.; Wawersik, W.R. |
1996-11-01
This paper describes an integrated geomechanics analysis of well casing damage induced by compaction of the diatomite reservoir at the Belridge Field, California. Historical data from the five field operators were compiled and analyzed to determine correlations between production, injection, subsidence, and well failures. The results of this analysis were used to develop a three-dimensional geomechanical model of South Belridge, Section 33 to examine the diatomite reservoir and overburden response to production and injection at the interwell scale and to evaluate potential well failure mechanisms. The time-dependent reservoir pressure field was derived from a three-dimensional finite difference reservoir simulation and used as input to three-dimensional non-linear finite element geomechanical simulations. The reservoir simulation included -200 wells and covered 18 years of production and injection. The geomechanical simulation contained 437,100 nodes and 374,130 elements with the overburden and reservoir discretized into 13 layers with independent material properties. The results reveal the evolution of the subsurface stress and displacement fields with production and injection and suggest strategies for reducing the occurrence of well casing damage.
Analysis of induced seismicity and heat transfer in geothermal reservoirs by coupled simulation
NASA Astrophysics Data System (ADS)
Gan, Quan
. Conversely, at high relative non-dimensional flow rates the propagating pressure pulse is larger and migrates more quickly through the reservoir but the thermal drawdown is uniform across the reservoir and without the presence of a distinct thermal front, and less capable of triggering late-stage seismicity. In Chapter 2 we develop a dimensionless model to predict the thermal drawdown response, and quantify the relationship between the timing and magnitude of late stage seismic event and the induced thermal stress from thermal drawdown. We evaluate the uniformity of thermal drawdown as a function of a dimensionless flow rate QD that scales with fracture spacing s( m), injection rate q (kg/s), and the distance between the injector and the target point L* ( Qd ∝ qs2 / L*). By assuming the dominant heat transfer by heat conduction within the fractured medium, this model is either capable to predict the timing of induced seismicity by the thermal stress by the analytical formula. Due to the significant influence of fracture network geometry in heat transfer and induced seismicity, a discrete fracture network model is developed (Chapter 3) to couple stress and fluid flow in a discontinuous fractured mass represented as a continuum by coupling the continuum simulator TF_FLAC 3D with cell-by-cell discontinuum laws for deformation and flow. Both equivalent medium crack and permeability tensor approaches are employed to characterize preexisting discrete fractures. The evolution of fracture permeability accommodates stress-dependent aperture under different stress states, including normal closure, shear dilation, and for fracture walls out of contact under tensile loading. This discrete fracture network model is applied (Chapter 4) in a generic reservoir with an initial permeability in the range of 10-17 to 10-16 m2, fracture density of ~0.09m -1 and fractures oriented such that either none, one, or both sets of fractures are critically stressed. For a given reservoir with a pre
49 CFR 229.49 - Main reservoir system.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 49 Transportation 4 2012-10-01 2012-10-01 false Main reservoir system. 229.49 Section 229.49... Main reservoir system. (a)(1) The main reservoir system of each locomotive shall be equipped with at... reservoir of air under pressure to be used for operating those power controls. The reservoir shall...
49 CFR 229.49 - Main reservoir system.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 49 Transportation 4 2014-10-01 2014-10-01 false Main reservoir system. 229.49 Section 229.49... Main reservoir system. (a)(1) The main reservoir system of each locomotive shall be equipped with at... reservoir of air under pressure to be used for operating those power controls. The reservoir shall...
49 CFR 229.49 - Main reservoir system.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 4 2013-10-01 2013-10-01 false Main reservoir system. 229.49 Section 229.49... Main reservoir system. (a)(1) The main reservoir system of each locomotive shall be equipped with at... reservoir of air under pressure to be used for operating those power controls. The reservoir shall...
49 CFR 229.49 - Main reservoir system.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 49 Transportation 4 2011-10-01 2011-10-01 false Main reservoir system. 229.49 Section 229.49... Main reservoir system. (a)(1) The main reservoir system of each locomotive shall be equipped with at... reservoir of air under pressure to be used for operating those power controls. The reservoir shall...
49 CFR 229.49 - Main reservoir system.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Main reservoir system. 229.49 Section 229.49... Main reservoir system. (a)(1) The main reservoir system of each locomotive shall be equipped with at... reservoir of air under pressure to be used for operating those power controls. The reservoir shall...
Discrete rogue waves in an array of waveguides
NASA Astrophysics Data System (ADS)
Efe, S.; Yuce, C.
2015-06-01
We study discrete rogue waves in an array of nonlinear waveguides. We show that very small degree of disorder due to experimental imperfection has a deep effect on the formation of discrete rogue waves. We predict long-living discrete rogue wave solution of the discrete nonlinear Schrödinger equation.
NASA Astrophysics Data System (ADS)
Cheng, Bingjie; Xu, Tianji; Robbins, Benedict; Shen, ZhongMing
2015-08-01
The organic reef is a special type of carbonate reservoir which always dominates the spatial distribution, reserves and accumulations of natural gas. However, it is difficult to determine the organic reef's internal structure and gas reservoirs due to numerous adverse factors such as the low resolution of seismic data, depth of burial, strong anisotropy, irregular spatial distribution and complex internal structure. A case study of wavelet decomposition and reconstruction technology applied to elucidate the features of organic reef reservoirs in the Changxing formation from Yuanba gas field shows that the seismic record reconstructed by high frequency signal can adequately describe the internal properties of organic reef reservoirs. Furthermore, the root mean square amplitude ratio of both low and high frequency data obtained from the reconstructed seismic data clearly show spatial distribution of gas and water in reef reservoirs.
Leijenaar, Ralph T.H.; Nalbantov, Georgi; Carvalho, Sara; van Elmpt, Wouter J.C.; Troost, Esther G.C.; Boellaard, Ronald; Aerts, Hugo J.W.L; Gillies, Robert J.; Lambin, Philippe
2015-01-01
FDG-PET-derived textural features describing intra-tumor heterogeneity are increasingly investigated as imaging biomarkers. As part of the process of quantifying heterogeneity, image intensities (SUVs) are typically resampled into a reduced number of discrete bins. We focused on the implications of the manner in which this discretization is implemented. Two methods were evaluated: (1) RD, dividing the SUV range into D equally spaced bins, where the intensity resolution (i.e. bin size) varies per image; and (2) RB, maintaining a constant intensity resolution B. Clinical feasibility was assessed on 35 lung cancer patients, imaged before and in the second week of radiotherapy. Forty-four textural features were determined for different D and B for both imaging time points. Feature values depended on the intensity resolution and out of both assessed methods, RB was shown to allow for a meaningful inter- and intra-patient comparison of feature values. Overall, patients ranked differently according to feature values–which was used as a surrogate for textural feature interpretation–between both discretization methods. Our study shows that the manner of SUV discretization has a crucial effect on the resulting textural features and the interpretation thereof, emphasizing the importance of standardized methodology in tumor texture analysis. PMID:26242464
Leijenaar, Ralph T H; Nalbantov, Georgi; Carvalho, Sara; van Elmpt, Wouter J C; Troost, Esther G C; Boellaard, Ronald; Aerts, Hugo J W L; Gillies, Robert J; Lambin, Philippe
2015-08-05
FDG-PET-derived textural features describing intra-tumor heterogeneity are increasingly investigated as imaging biomarkers. As part of the process of quantifying heterogeneity, image intensities (SUVs) are typically resampled into a reduced number of discrete bins. We focused on the implications of the manner in which this discretization is implemented. Two methods were evaluated: (1) R(D), dividing the SUV range into D equally spaced bins, where the intensity resolution (i.e. bin size) varies per image; and (2) R(B), maintaining a constant intensity resolution B. Clinical feasibility was assessed on 35 lung cancer patients, imaged before and in the second week of radiotherapy. Forty-four textural features were determined for different D and B for both imaging time points. Feature values depended on the intensity resolution and out of both assessed methods, R(B) was shown to allow for a meaningful inter- and intra-patient comparison of feature values. Overall, patients ranked differently according to feature values–which was used as a surrogate for textural feature interpretation–between both discretization methods. Our study shows that the manner of SUV discretization has a crucial effect on the resulting textural features and the interpretation thereof, emphasizing the importance of standardized methodology in tumor texture analysis.
NASA Astrophysics Data System (ADS)
Leijenaar, Ralph T. H.; Nalbantov, Georgi; Carvalho, Sara; van Elmpt, Wouter J. C.; Troost, Esther G. C.; Boellaard, Ronald; Aerts, Hugo J. W. L.; Gillies, Robert J.; Lambin, Philippe
2015-08-01
FDG-PET-derived textural features describing intra-tumor heterogeneity are increasingly investigated as imaging biomarkers. As part of the process of quantifying heterogeneity, image intensities (SUVs) are typically resampled into a reduced number of discrete bins. We focused on the implications of the manner in which this discretization is implemented. Two methods were evaluated: (1) RD, dividing the SUV range into D equally spaced bins, where the intensity resolution (i.e. bin size) varies per image; and (2) RB, maintaining a constant intensity resolution B. Clinical feasibility was assessed on 35 lung cancer patients, imaged before and in the second week of radiotherapy. Forty-four textural features were determined for different D and B for both imaging time points. Feature values depended on the intensity resolution and out of both assessed methods, RB was shown to allow for a meaningful inter- and intra-patient comparison of feature values. Overall, patients ranked differently according to feature values-which was used as a surrogate for textural feature interpretation-between both discretization methods. Our study shows that the manner of SUV discretization has a crucial effect on the resulting textural features and the interpretation thereof, emphasizing the importance of standardized methodology in tumor texture analysis.
Constraint analysis for variational discrete systems
Dittrich, Bianca; Höhn, Philipp A.
2013-09-15
A canonical formalism and constraint analysis for discrete systems subject to a variational action principle are devised. The formalism is equivalent to the covariant formulation, encompasses global and local discrete time evolution moves and naturally incorporates both constant and evolving phase spaces, the latter of which is necessary for a time varying discretization. The different roles of constraints in the discrete and the conditions under which they are first or second class and/or symmetry generators are clarified. The (non-) preservation of constraints and the symplectic structure is discussed; on evolving phase spaces the number of constraints at a fixed time step depends on the initial and final time step of evolution. Moreover, the definition of observables and a reduced phase space is provided; again, on evolving phase spaces the notion of an observable as a propagating degree of freedom requires specification of an initial and final step and crucially depends on this choice, in contrast to the continuum. However, upon restriction to translation invariant systems, one regains the usual time step independence of canonical concepts. This analysis applies, e.g., to discrete mechanics, lattice field theory, quantum gravity models, and numerical analysis.
Discrete breathers for a discrete nonlinear Schrödinger ring coupled to a central site.
Jason, Peter; Johansson, Magnus
2016-01-01
We examine the existence and properties of certain discrete breathers for a discrete nonlinear Schrödinger model where all but one site are placed in a ring and coupled to the additional central site. The discrete breathers we focus on are stationary solutions mainly localized on one or a few of the ring sites and possibly also the central site. By numerical methods, we trace out and study the continuous families the discrete breathers belong to. Our main result is the discovery of a split bifurcation at a critical value of the coupling between neighboring ring sites. Below this critical value, families form closed loops in a certain parameter space, implying that discrete breathers with and without central-site occupation belong to the same family. Above the split bifurcation the families split up into several separate ones, which bifurcate with solutions with constant ring amplitudes. For symmetry reasons, the families have different properties below the split bifurcation for even and odd numbers of sites. It is also determined under which conditions the discrete breathers are linearly stable. The dynamics of some simpler initial conditions that approximate the discrete breathers are also studied and the parameter regimes where the dynamics remain localized close to the initially excited ring site are related to the linear stability of the exact discrete breathers.
ERIC Educational Resources Information Center
Rosenstein, Joseph G., Ed.; Franzblau, Deborah S., Ed.; Roberts, Fred S., Ed.
This book is a collection of articles by experienced educators and explains why and how discrete mathematics should be taught in K-12 classrooms. It includes evidence for "why" and practical guidance for "how" and also discusses how discrete mathematics can be used as a vehicle for achieving the broader goals of the major…
Sibillano, Teresa; Ancona, Antonio; Rizzi, Domenico; Lupo, Valentina; Tricarico, Luigi; Lugarà, Pietro Mario
2010-01-01
The plasma optical radiation emitted during CO2 laser welding of stainless steel samples has been detected with a Si-PIN photodiode and analyzed under different process conditions. The discrete wavelet transform (DWT) has been used to decompose the optical signal into various discrete series of sequences over different frequency bands. The results show that changes of the process settings may yield different signal features in the range of frequencies between 200 Hz and 30 kHz. Potential applications of this method to monitor in real time the laser welding processes are also discussed. PMID:22319311
The electrical behavior of GaAs-insulator interfaces - A discrete energy interface state model
NASA Technical Reports Server (NTRS)
Kazior, T. E.; Lagowski, J.; Gatos, H. C.
1983-01-01
The relationship between the electrical behavior of GaAs Metal Insulator Semiconductor (MIS) structures and the high density discrete energy interface states (0.7 and 0.9 eV below the conduction band) was investigated utilizing photo- and thermal emission from the interface states in conjunction with capacitance measurements. It was found that all essential features of the anomalous behavior of GaAs MIS structures, such as the frequency dispersion and the C-V hysteresis, can be explained on the basis of nonequilibrium charging and discharging of the high density discrete energy interface states.
Formation of discrete solitons in light-induced photonic lattices.
Chen, Zhigang; Martin, Hector; Eugenieva, Eugenia; Xu, Jingjun; Yang, Jianke
2005-03-21
We present both experimental and theoretical results on discrete solitons in two-dimensional optically-induced photonic lattices in a variety of settings, including fundamental discrete solitons, vector-like discrete solitons, discrete dipole solitons, and discrete soliton trains. In each case, a clear transition from two-dimensional discrete diffraction to discrete trapping is demonstrated with a waveguide lattice induced by partially coherent light in a bulk photorefractive crystal. Our experimental results are in good agreement with the theoretical analysis of these effects.
NASA Astrophysics Data System (ADS)
Kosack, Christian; Vogt, Christian; Rath, Volker; Marquart, Gabriele
2010-05-01
, permeability, and dispersivity which produces a nearly perfect fit to the measured tracer data. The models used for the inversion are simplified to the main geologic elements of the geothermal reservoir and consist of only 2 to 4 regions of constant properties. Optimal a-posteriori parameter estimates will be complemented by an analysis of parameter dependencies and uncertainties as a by-product of the nonlinear inversion. With both ensemble methods a cell-wise discrete spatial distribution of the permeability can be retrieved. For MC approach we produced a large number of system realizations with permeability distributions randomly picked from a bimodal histogram of the enhanced zone and the surrounding. The main fracture area is modelled by assuming a high permeability and an anisotropic correlation length. After forward simulation of the tracer experiment, the successful realizations are selected and further grouped to study principal features of the permeability distribution. Similar to the MC approach, the EnKF is based on a forward propagation of an ensemble of realizations. At successive instants in time, different kinds of data as tracer concentration, bottom hole pressure, and permeability in various drill holes are collected in one data vector and used to update (assimilate) the system variables to improve the match between observation and simulation leading to a convergence of the ensemble. We studied the performance and spatial resolution of the EnKF procedure for a 3D test model which is based on the borehole locations and tracer experiment of the Soultz geothermal reservoir. We used all available information to condition the pressure field and to estimate the permeability. Already after a few assimilation steps the ensemble average permeability shows coarse features of the expected permeability field. However, any estimates of smaller scale permeability variations turn out to be very sensitive to the (potentially unknown) correlation lengths.
Stone, Mandy L.; Juracek, Kyle E.; Graham, Jennifer; Foster, Guy
2015-01-01
Cheney Reservoir, constructed during 1962 to 1965, is the primary water supply for the city of Wichita, the largest city in Kansas. Sediment is an important concern for the reservoir as it degrades water quality and progressively decreases water storage capacity. Long-term data collection provided a unique opportunity to estimate the annual suspended sediment loads for the entire history of the reservoir. To quantify and characterize sediment loading to Cheney Reservoir, discrete suspended sediment samples and continuously measured streamflow data were collected from the North Fork Ninnescah River, the primary inflow to Cheney Reservoir, over a 48-year period. Continuous turbidity data also were collected over a 15-year period. These data were used together to develop simple linear regression models to compute continuous suspended sediment concentrations and loads from 1966 to 2013. The inclusion of turbidity as an additional explanatory variable with streamflow improved regression model diagnostics and increased the amount of variability in suspended sediment concentration explained by 14%. Using suspended sediment concentration from the streamflow-only model, the average annual suspended sediment load was 102,517 t (113,006 tn) and ranged from 4,826 t (5,320 tn) in 1966 to 967,569 t (1,066,562 tn) in 1979. The sediment load in 1979 accounted for about 20% of the total load over the 48-year history of the reservoir and 92% of the 1979 sediment load occurred in one 24-hour period during a 1% annual exceedance probability flow event (104-year flood). Nearly 60% of the reservoir sediment load during the 48-year study period occurred in 5 years with extreme flow events (9% to 1% annual exceedance probability, or 11- to 104-year flood events). A substantial portion (41%) of sediment was transported to the reservoir during five storm events spanning only eight 24-hour periods during 1966 to 2013. Annual suspended sediment load estimates based on streamflow were, on
Ostfeld, Richard S; Levi, Taal; Jolles, Anna E; Martin, Lynn B; Hosseini, Parviez R; Keesing, Felicia
2014-01-01
Animal and plant species differ dramatically in their quality as hosts for multi-host pathogens, but the causes of this variation are poorly understood. A group of small mammals, including small rodents and shrews, are among the most competent natural reservoirs for three tick-borne zoonotic pathogens, Borrelia burgdorferi, Babesia microti, and Anaplasma phagocytophilum, in eastern North America. For a group of nine commonly-infected mammals spanning >2 orders of magnitude in body mass, we asked whether life history features or surrogates for (unknown) encounter rates with ticks, predicted reservoir competence for each pathogen. Life history features associated with a fast pace of life generally were positively correlated with reservoir competence. However, a model comparison approach revealed that host population density, as a proxy for encounter rates between hosts and pathogens, generally received more support than did life history features. The specific life history features and the importance of host population density differed somewhat between the different pathogens. We interpret these results as supporting two alternative but non-exclusive hypotheses for why ecologically widespread, synanthropic species are often the most competent reservoirs for multi-host pathogens. First, multi-host pathogens might adapt to those hosts they are most likely to experience, which are likely to be the most abundant and/or frequently bitten by tick vectors. Second, species with fast life histories might allocate less to certain immune defenses, which could increase their reservoir competence. Results suggest that of the host species that might potentially be exposed, those with comparatively high population densities, small bodies, and fast pace of life will often be keystone reservoirs that should be targeted for surveillance or management.
An algebra of discrete event processes
NASA Technical Reports Server (NTRS)
Heymann, Michael; Meyer, George
1991-01-01
This report deals with an algebraic framework for modeling and control of discrete event processes. The report consists of two parts. The first part is introductory, and consists of a tutorial survey of the theory of concurrency in the spirit of Hoare's CSP, and an examination of the suitability of such an algebraic framework for dealing with various aspects of discrete event control. To this end a new concurrency operator is introduced and it is shown how the resulting framework can be applied. It is further shown that a suitable theory that deals with the new concurrency operator must be developed. In the second part of the report the formal algebra of discrete event control is developed. At the present time the second part of the report is still an incomplete and occasionally tentative working paper.
LAPS discretization and solution of plasma equilibrium
NASA Astrophysics Data System (ADS)
Missanelli, Maria; Delzanno, Gian Luca; Guo, Zehua; Srinivasan, Bhuvana; Tang, Xianzhu
2011-10-01
LAPS provides spectral element discretization for solving steady state plasma profiles. Our initial focus is on its implementation for two dimensional open magnetic field equilibria in linear and toroidal geometries. The linear geometry is an axisymmetric magnetic mirror with anisotropic pressure. The toroidal case is a tokamak scrape-off layer plasma. Structured grids are produced by the grid generation package in LAPS. The spectral element discretization uses modal bases over quadrilateral elements. A Newton-Krylov solver implemented with the Portable, Extensible Toolkits for Scientific Computing PETSc is applied to iteratively converge the solution. Care has been taken in the code design to separate the grid generation, spectral element discretization, and (non)linear solver from the user-specified equilibrium equations, so the LAPS infrastructure can be easily used for different applications. Work supported by DOE OFES.
Numerical discretization for nonlinear diffusion filter
NASA Astrophysics Data System (ADS)
Mustaffa, I.; Mizuar, I.; Aminuddin, M. M. M.; Dasril, Y.
2015-05-01
Nonlinear diffusion filters are famously used in machine vision for image denoising and restoration. This paper presents a study on the effects of different numerical discretization of nonlinear diffusion filter. Several numerical discretization schemes are presented; namely semi-implicit, AOS, and fully implicit schemes. The results of these schemes are compared by visual results, objective measurement e.g. PSNR and MSE. The results are also compared to a Daubechies wavelet denoising method. It is acknowledged that the two preceding scheme have already been discussed in literature, however comparison to the latter scheme has not been made. The semi-implicit scheme uses an additive operator splitting (AOS) developed to overcome the shortcoming of the explicit scheme i.e., stability for very small time steps. Although AOS has proven to be efficient, from the nonlinear diffusion filter results with different discretization schemes, examples shows that implicit schemes are worth pursuing.
Superheavy dark matter with discrete gauge symmetries
NASA Astrophysics Data System (ADS)
Hamaguchi, K.; Nomura, Yasunori; Yanagida, T.
1998-11-01
We show that there are discrete gauge symmetries which naturally protect heavy X particles from decaying into ordinary light particles in the supersymmetric standard model. This makes the proposal that superheavy X particles constitute part of the dark matter in the present universe very attractive. It is more interesting that there is a class of discrete gauge symmetries which naturally accommodates a long-lived unstable X particle. We find that in some discrete Z10 models, for example, a superheavy X particle has a lifetime of τX~=1011-1026 yr for a mass of MX~=1013-1014 GeV. This long lifetime is guaranteed by the absence of lower dimensional operators (of light particles) coupled to the X. We briefly discuss a possible explanation for the recently observed ultrahigh-energy cosmic ray events by the decay of this unstable X particle.
Optimal Learning Rules for Discrete Synapses
Barrett, Adam B.; van Rossum, M. C. W.
2008-01-01
There is evidence that biological synapses have a limited number of discrete weight states. Memory storage with such synapses behaves quite differently from synapses with unbounded, continuous weights, as old memories are automatically overwritten by new memories. Consequently, there has been substantial discussion about how this affects learning and storage capacity. In this paper, we calculate the storage capacity of discrete, bounded synapses in terms of Shannon information. We use this to optimize the learning rules and investigate how the maximum information capacity depends on the number of synapses, the number of synaptic states, and the coding sparseness. Below a certain critical number of synapses per neuron (comparable to numbers found in biology), we find that storage is similar to unbounded, continuous synapses. Hence, discrete synapses do not necessarily have lower storage capacity. PMID:19043540
Discrete breathers in hexagonal dusty plasma lattices
Koukouloyannis, V.; Kourakis, I.
2009-08-15
The occurrence of single-site or multisite localized vibrational modes, also called discrete breathers, in two-dimensional hexagonal dusty plasma lattices is investigated. The system is described by a Klein-Gordon hexagonal lattice characterized by a negative coupling parameter epsilon in account of its inverse dispersive behavior. A theoretical analysis is performed in order to establish the possibility of existence of single as well as three-site discrete breathers in such systems. The study is complemented by a numerical investigation based on experimentally provided potential forms. This investigation shows that a dusty plasma lattice can support single-site discrete breathers, while three-site in phase breathers could exist if specific conditions, about the intergrain interaction strength, would hold. On the other hand, out of phase and vortex three-site breathers cannot be supported since they are highly unstable.
Discrete-time Markovian stochastic Petri nets
NASA Technical Reports Server (NTRS)
Ciardo, Gianfranco
1995-01-01
We revisit and extend the original definition of discrete-time stochastic Petri nets, by allowing the firing times to have a 'defective discrete phase distribution'. We show that this formalism still corresponds to an underlying discrete-time Markov chain. The structure of the state for this process describes both the marking of the Petri net and the phase of the firing time for each transition, resulting in a large state space. We then modify the well-known power method to perform a transient analysis even when the state space is infinite, subject to the condition that only a finite number of states can be reached in a finite amount of time. Since the memory requirements might still be excessive, we suggest a bounding technique based on truncation.
Discrete Roughness Transition for Hypersonic Flight Vehicles
NASA Technical Reports Server (NTRS)
Berry, Scott A.; Horvath, Thomas J.
2007-01-01
The importance of discrete roughness and the correlations developed to predict the onset of boundary layer transition on hypersonic flight vehicles are discussed. The paper is organized by hypersonic vehicle applications characterized in a general sense by the boundary layer: slender with hypersonic conditions at the edge of the boundary layer, moderately blunt with supersonic, and blunt with subsonic. This paper is intended to be a review of recent discrete roughness transition work completed at NASA Langley Research Center in support of agency flight test programs. First, a review is provided of discrete roughness wind tunnel data and the resulting correlations that were developed. Then, results obtained from flight vehicles, in particular the recently flown Hyper-X and Shuttle missions, are discussed and compared to the ground-based correlations.
The ultimatum game: Discrete vs. continuous offers
NASA Astrophysics Data System (ADS)
Dishon-Berkovits, Miriam; Berkovits, Richard
2014-09-01
In many experimental setups in social-sciences, psychology and economy the subjects are requested to accept or dispense monetary compensation which is usually given in discrete units. Using computer and mathematical modeling we show that in the framework of studying the dynamics of acceptance of proposals in the ultimatum game, the long time dynamics of acceptance of offers in the game are completely different for discrete vs. continuous offers. For discrete values the dynamics follow an exponential behavior. However, for continuous offers the dynamics are described by a power-law. This is shown using an agent based computer simulation as well as by utilizing an analytical solution of a mean-field equation describing the model. These findings have implications to the design and interpretation of socio-economical experiments beyond the ultimatum game.
Temperature and oxygen in Missouri reservoirs
Jones, John R.; Knowlton, Matthew F.; Obrecht, Daniel V.; Graham, Jennifer L.
2011-01-01
Vertical profiles of water temperature (n = 7193) and dissolved oxygen (n = 6516) were collected from 235 Missouri reservoirs during 1989–2007; most data were collected during May–August and provide a regional summary of summer conditions. Collectively, surface water temperature ranged from a mean of ~22 C in May to 28 C in July, and individual summer maxima typically were 28–32 C. Most (~95%) reservoirs stably stratify by mid-May, but few are deep enough to have hypolimnia with near-uniform temperatures. Among stratified reservoirs, maximum effective length and maximum depth accounted for 75% of the variation in mixed depth and thermocline depth. Ephemeral, near-surface thermoclines occurred in 39% of summer profiles and were most frequent in small, turbid reservoirs. Isotherms below the mixed layer deepen during stratification, and the water column is >20 C by August in all but the deepest reservoirs. Most reservoirs showed incipient dissolved oxygen (DO) depletion by mid-May, and by August, 80% of profiles had DO minima of 50% of variation in DO below the mixed layer during summer. Warm summer temperatures and widespread low DO often limit available fish habitat in Missouri reservoirs and compress warm-water fish communities into subsurface layers that exceed their thermal preferences. This study provides a regional baseline of reservoir temperature and oxygen conditions useful for future evaluations of eutrophication and the effects of a warming climate.
An index of reservoir habitat impairment
Miranda, L.E.; Hunt, K.M.
2011-01-01
Fish habitat impairment resulting from natural and anthropogenic watershed and in-lake processes has in many cases reduced the ability of reservoirs to sustain native fish assemblages and fisheries quality. Rehabilitation of impaired reservoirs is hindered by the lack of a method suitable for scoring impairment status. To address this limitation, an index of reservoir habitat impairment (IRHI) was developed by merging 14 metrics descriptive of common impairment sources, with each metric scored from 0 (no impairment) to 5 (high impairment) by fisheries scientists with local knowledge. With a plausible range of 5 to 25, distribution of the IRHI scores ranged from 5 to 23 over 482 randomly selected reservoirs dispersed throughout the USA. The IRHI reflected five impairment factors including siltation, structural habitat, eutrophication, water regime, and aquatic plants. The factors were weakly related to key reservoir characteristics including reservoir area, depth, age, and usetype, suggesting that common reservoir descriptors are poor predictors of fish habitat impairment. The IRHI is rapid and inexpensive to calculate, provides an easily understood measure of the overall habitat impairment, allows comparison of reservoirs and therefore prioritization of restoration activities, and may be used to track restoration progress. The major limitation of the IRHI is its reliance on unstandardized professional judgment rather than standardized empirical measurements. ?? 2010 US Government.
Water resources review: Wheeler Reservoir, 1990
Wallus, R.; Cox, J.P.
1990-09-01
Protection and enhancement of water quality is essential for attaining the full complement of beneficial uses of TVA reservoirs. The responsibility for improving and protecting TVA reservoir water quality is shared by various federal, state, and local agencies, as well as the thousands of corporations and property owners whose individual decisions affect water quality. TVA's role in this shared responsibility includes collecting and evaluating water resources data, disseminating water resources information, and acting as a catalyst to bring together agencies and individuals that have a responsibility or vested interest in correcting problems that have been identified. This report is one in a series of status reports that will be prepared for each of TVA's reservoirs. The purpose of this status report is to provide an up-to-date overview of the characteristics and conditions of Wheeler Reservoir, including: reservoir purposes and operation; physical characteristics of the reservoir and the watershed; water quality conditions: aquatic biological conditions: designated, actual, and potential uses of the reservoir and impairments of those uses; ongoing or planned reservoir management activities. Information and data presented here are form the most recent reports, publications, and original data available. 21 refs., 8 figs., 29 tabs.
European Rabbits as Reservoir for Coxiella burnetii
González-Barrio, David; Maio, Elisa; Vieira-Pinto, Madalena
2015-01-01
We studied the role of European rabbits (Oryctolagus cuniculus) as a reservoir for Coxiella burnetii in the Iberian region. High individual and population seroprevalences observed in wild and farmed rabbits, evidence of systemic infections, and vaginal shedding support the reservoir role of the European rabbit for C. burnetii. PMID:25988670
Carbon emission from global hydroelectric reservoirs revisited.
Li, Siyue; Zhang, Quanfa
2014-12-01
Substantial greenhouse gas (GHG) emissions from hydropower reservoirs have been of great concerns recently, yet the significant carbon emitters of drawdown area and reservoir downstream (including spillways and turbines as well as river reaches below dams) have not been included in global carbon budget. Here, we revisit GHG emission from hydropower reservoirs by considering reservoir surface area, drawdown zone and reservoir downstream. Our estimates demonstrate around 301.3 Tg carbon dioxide (CO2)/year and 18.7 Tg methane (CH4)/year from global hydroelectric reservoirs, which are much higher than recent observations. The sum of drawdown and downstream emission, which is generally overlooked, represents 42 % CO2 and 67 % CH4 of the total emissions from hydropower reservoirs. Accordingly, the global average emissions from hydropower are estimated to be 92 g CO2/kWh and 5.7 g CH4/kWh. Nonetheless, global hydroelectricity could currently reduce approximate 2,351 Tg CO2eq/year with respect to fuel fossil plant alternative. The new findings show a substantial revision of carbon emission from the global hydropower reservoirs.
Mycobacterium bovis: characteristics of wildlife reservoir hosts.
Palmer, M V
2013-11-01
Mycobacterium bovis is the cause of tuberculosis in animals and sometimes humans. Many developed nations have long-standing programmes to eradicate tuberculosis in livestock, principally cattle. As disease prevalence in cattle decreases these efforts are sometimes impeded by passage of M. bovis from wildlife to cattle. In epidemiological terms, disease can persist in some wildlife species, creating disease reservoirs, if the basic reproduction rate (R0) and critical community size (CCS) thresholds are achieved. Recognized wildlife reservoir hosts of M. bovis include the brushtail possum (Trichosurus vulpecula) in New Zealand, European badger (Meles meles) in Great Britain and Ireland, African buffalo (Syncerus caffer) in South Africa, wild boar (Sus scrofa) in the Iberian Peninsula and white-tailed deer (Odocoileus virginianus) in Michigan, USA. The epidemiological concepts of R0 and CCS are related to more tangible disease/pathogen characteristics such as prevalence, pathogen-induced pathology, host behaviour and ecology. An understanding of both epidemiological and disease/pathogen characteristics is necessary to identify wildlife reservoirs of M. bovis. In some cases, there is a single wildlife reservoir host involved in transmission of M. bovis to cattle. Complexity increases, however, in multihost systems where multiple potential reservoir hosts exist. Bovine tuberculosis eradication efforts require elimination of M. bovis transmission between wildlife reservoirs and cattle. For successful eradication identification of true wildlife reservoirs is critical, as disease control efforts are most effective when directed towards true reservoirs.
Prestack seismic inversion and reservoir property prediction
NASA Astrophysics Data System (ADS)
Chi, Xingang
In this dissertation, I have applied the method of prestack seismic inversion with uncertainty analysis. Also, I have developed the methods of the rock physics template analysis, the fluid modulus inversion and the reservoir property inversion from AVO attributes with and without constraint to improve the technique of reservoir characterization. I use the prestack seismic inversion to invert the elastic properties and use the statistical method to derive the posterior probability of the inverted elastic properties for the uncertainty analysis. I use the rock physics template drawn in the cross-plot of the inverted elastic properties to analyze the lithology and fluid property in the target reservoir. I develop the fluid modulus inversion method based on the simplified Gassmann's equation and the empirical rock physics relationship. Using the inverted fluid modulus, I estimate the gas saturation of the target reservoir before drilling. The reservoir property inversion is to predict the porosity, shale volume and water saturation of the reservoir from AVO attributes to enhance the reservoir interpretation and characterization. I apply this method with the statistical analysis together to execute the uncertainty analysis for the inversion results. Two methods of reservoir property inversion from AVO attributes are attempted in this dissertation: one is performed without constraint and the other is performed with the constrained relationship of the porosity and shale volume.
Carbon content of sediments of small reservoirs
Ritchie, J.C. )
1989-04-01
Carbon content was measured in sediments deposited in 58 small reservoirs across the US. Reservoirs varied from 0.2 to 4,000 km{sup 2} in surface area. The carbon content of sediment ranged from 0.3 to 5.6 percent, with a mean of 1.9 {plus minus} 1.1 percent. No significant differences between the soil and sediment carbon content were found using a paired t-test or ANOVA. The carbon content of sediments in reservoirs was similar to the carbon content of surface soils in the watershed, except in watersheds with shrub or steppe (desert) vegetation. Based on the sediment accumulation rates measured in each reservoir, the calculated organic carbon accumulation rates among reservoirs ranged from 26 to 3,700 gC m{sup {minus}2} yr{sup {minus}1}, with a mean of 675 {plus minus} 739 gC m{sup {minus}2} yr{sup {minus}1}. The carbon content and accumulation rates were highest in sediments from grassland watersheds. High variability was found in carbon content, carbon accumulation, and sediment accumulation rates due to individual watershed and reservoir characteristics rather than to any broad physiographic patterns. The carbon accumulation rates in these reservoir sediments indicate that reservoir sediments could be a significant sink of organic carbon.
Economics of Developing Hot Stratigraphic Reservoirs
Greg Mines; Hillary Hanson; Rick Allis; Joseph Moore
2014-09-01
Stratigraphic geothermal reservoirs at 3 – 4 km depth in high heat-flow basins are capable of sustaining 100 MW-scale power plants at about 10 c/kWh. This paper examines the impacts on the levelized cost of electricity (LCOE) of reservoir depth and temperature, reservoir productivity, and drillhole/casing options. For a reservoir at 3 km depth with a moderate productivity index by hydrothermal reservoir standards (about 50 L/s/MPa, 5.6 gpm/psi), an LCOE of 10c/kWh requires the reservoir to be at about 200°C. This is the upper temperature limit for pumps. The calculations assume standard hydrothermal drilling costs, with the production interval completed with a 7 inch liner in an 8.5 inch hole. If a reservoir at 4 km depth has excellent permeability characteristics with a productivity index of 100 L/s/MPa (11.3 gpm/psi), then the LCOE is about 11 c/kWh assuming the temperature decline rate with development is not excessive (< 1%/y, with first thermal breakthrough delayed by about 10 years). Completing wells with modest horizontal legs (e.g. several hundred meters) may be important for improving well productivity because of the naturally high, sub-horizontal permeability in this type of reservoir. Reducing the injector/producer well ratio may also be cost-effective if the injectors are drilled as larger holes.
Climate variations, soil conservation and reservoir sedimentation
Technology Transfer Automated Retrieval System (TEKTRAN)
The integrated effects of soil conservation and a wetter climate on reservoir sedimentation were investigated for the Fort Cobb Reservoir watershed in west-central Oklahoma. A 12% wetter climate since the mid-1980s led to an increase in soil erosion and downstream sediment yield that offset the redu...
Seismic determination of saturation in fractured reservoirs
Brown, R.L.; Wiggins, M.L.; Gupta, A.
2002-01-01
Detecting the saturation of a fractured reservoir using shear waves is possible when the fractures have a geometry that induces a component of movement perpendicular to the fractures. When such geometry is present, vertically traveling shear waves can be used to examine the saturation of the fractured reservoir. Tilted, corrugated, and saw-tooth fracture models are potential examples.
Electromagnetic Heating Methods for Heavy Oil Reservoirs
Sahni, A.; Kumar, M.; Knapp, R.B.
2000-05-01
The most widely used method of thermal oil recovery is by injecting steam into the reservoir. A well-designed steam injection project is very efficient in recovering oil, however its applicability is limited in many situations. Simulation studies and field experience has shown that for low injectivity reservoirs, small thickness of the oil-bearing zone, and reservoir heterogeneity limits the performance of steam injection. This paper discusses alternative methods of transferring heat to heavy oil reservoirs, based on electromagnetic energy. They present a detailed analysis of low frequency electric resistive (ohmic) heating and higher frequency electromagnetic heating (radio and microwave frequency). They show the applicability of electromagnetic heating in two example reservoirs. The first reservoir model has thin sand zones separated by impermeable shale layers, and very viscous oil. They model preheating the reservoir with low frequency current using two horizontal electrodes, before injecting steam. The second reservoir model has very low permeability and moderately viscous oil. In this case they use a high frequency microwave antenna located near the producing well as the heat source. Simulation results presented in this paper show that in some cases, electromagnetic heating may be a good alternative to steam injection or maybe used in combination with steam to improve heavy oil production. They identify the parameters which are critical in electromagnetic heating. They also discuss past field applications of electromagnetic heating including technical challenges and limitations.
Nguyen, Ba Nghiep; Hou, Zhangshuan; Last, George V.; Bacon, Diana H.
2016-12-01
This work develops a three-dimensional multiscale model to analyze a complex CO_{2} faulted reservoir that includes some key geological features of the San Andreas and nearby faults southwest of the Kimberlina site. The model uses the STOMP-CO_{2} code for flow modeling that is coupled to the ABAQUS® finite element package for geomechanical analysis. A 3D ABAQUS® finite element model is developed that contains a large number of 3D solid elements with two nearly parallel faults whose damage zones and cores are discretized using the same continuum elements. Five zones with different mineral compositions are considered: shale, sandstone, fault damaged sandstone, fault damaged shale, and fault core. Rocks’ elastic properties that govern their poroelastic behavior are modeled by an Eshelby-Mori-Tanka approach (EMTA). EMTA can account for up to 15 mineral phases. The permeability of fault damage zones affected by crack density and orientations is also predicted by an EMTA formulation. A STOMP-CO_{2} grid that exactly maps the ABAQUS® finite element model is built for coupled hydro-mechanical analyses. Simulations of the reservoir assuming three different crack pattern situations (including crack volume fraction and orientation) for the fault damage zones are performed to predict the potential leakage of CO_{2} due to cracks that enhance the permeability of the fault damage zones. The results illustrate the important effect of the crack orientation on fault permeability that can lead to substantial leakage along the fault attained by the expansion of the CO_{2} plume. Potential hydraulic fracture and the tendency for the faults to slip are also examined and discussed in terms of stress distributions and geomechanical properties.
Wiggins, Michael L.; Brown, Raymon L.; Civan, Faruk; Hughes, Richard G.
2003-02-11
This research was directed toward developing a systematic reservoir characterization methodology which can be used by the petroleum industry to implement infill drilling programs and/or enhanced oil recovery projects in naturally fractured reservoir systems in an environmentally safe and cost effective manner. It was anticipated that the results of this research program will provide geoscientists and engineers with a systematic procedure for properly characterizing a fractured reservoir system and a reservoir/horizontal wellbore simulator model which can be used to select well locations and an effective EOR process to optimize the recovery of the oil and gas reserves from such complex reservoir systems.
Reagan, Matthew T; Moridis, George J; Keen, Noel D; Johnson, Jeffrey N
2015-01-01
Hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques, such as hydraulic fracturing, has grown explosively over the last decade. However, concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers, thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids. This study investigates, by numerical simulation, gas and water transport between a shallow tight-gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations, if such a connecting pathway has been created. We focus on two general failure scenarios: (1) communication between the reservoir and aquifer via a connecting fracture or fault and (2) communication via a deteriorated, preexisting nearby well. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure, and not producing may increase the potential for release. We also find that hydrostatic tight-gas reservoirs are unlikely to act as a continuing source of migrating gas, as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination. Such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes. Key Points: Short-term leakage fractured reservoirs requires high-permeability pathways Production strategy affects the likelihood and magnitude of gas release Gas release is likely short-term, without additional driving forces PMID
Cortical Neural Computation by Discrete Results Hypothesis.
Castejon, Carlos; Nuñez, Angel
2016-01-01
One of the most challenging problems we face in neuroscience is to understand how the cortex performs computations. There is increasing evidence that the power of the cortical processing is produced by populations of neurons forming dynamic neuronal ensembles. Theoretical proposals and multineuronal experimental studies have revealed that ensembles of neurons can form emergent functional units. However, how these ensembles are implicated in cortical computations is still a mystery. Although cell ensembles have been associated with brain rhythms, the functional interaction remains largely unclear. It is still unknown how spatially distributed neuronal activity can be temporally integrated to contribute to cortical computations. A theoretical explanation integrating spatial and temporal aspects of cortical processing is still lacking. In this Hypothesis and Theory article, we propose a new functional theoretical framework to explain the computational roles of these ensembles in cortical processing. We suggest that complex neural computations underlying cortical processing could be temporally discrete and that sensory information would need to be quantized to be computed by the cerebral cortex. Accordingly, we propose that cortical processing is produced by the computation of discrete spatio-temporal functional units that we have called "Discrete Results" (Discrete Results Hypothesis). This hypothesis represents a novel functional mechanism by which information processing is computed in the cortex. Furthermore, we propose that precise dynamic sequences of "Discrete Results" is the mechanism used by the cortex to extract, code, memorize and transmit neural information. The novel "Discrete Results" concept has the ability to match the spatial and temporal aspects of cortical processing. We discuss the possible neural underpinnings of these functional computational units and describe the empirical evidence supporting our hypothesis. We propose that fast-spiking (FS
Cortical Neural Computation by Discrete Results Hypothesis
Castejon, Carlos; Nuñez, Angel
2016-01-01
One of the most challenging problems we face in neuroscience is to understand how the cortex performs computations. There is increasing evidence that the power of the cortical processing is produced by populations of neurons forming dynamic neuronal ensembles. Theoretical proposals and multineuronal experimental studies have revealed that ensembles of neurons can form emergent functional units. However, how these ensembles are implicated in cortical computations is still a mystery. Although cell ensembles have been associated with brain rhythms, the functional interaction remains largely unclear. It is still unknown how spatially distributed neuronal activity can be temporally integrated to contribute to cortical computations. A theoretical explanation integrating spatial and temporal aspects of cortical processing is still lacking. In this Hypothesis and Theory article, we propose a new functional theoretical framework to explain the computational roles of these ensembles in cortical processing. We suggest that complex neural computations underlying cortical processing could be temporally discrete and that sensory information would need to be quantized to be computed by the cerebral cortex. Accordingly, we propose that cortical processing is produced by the computation of discrete spatio-temporal functional units that we have called “Discrete Results” (Discrete Results Hypothesis). This hypothesis represents a novel functional mechanism by which information processing is computed in the cortex. Furthermore, we propose that precise dynamic sequences of “Discrete Results” is the mechanism used by the cortex to extract, code, memorize and transmit neural information. The novel “Discrete Results” concept has the ability to match the spatial and temporal aspects of cortical processing. We discuss the possible neural underpinnings of these functional computational units and describe the empirical evidence supporting our hypothesis. We propose that fast
The discrete regime of flame propagation
NASA Astrophysics Data System (ADS)
Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew
The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment
Characterization of oil and gas reservoir heterogeneity
Sharma, G.D.
1992-01-01
The ultimate objective of this cooperative research project is to characterize Alaskan petroleum reservoirs in terms of their reserves, physical and chemical properties, geologic configuration in relation to lithofacies and structure, and development potential. The project has two tasks: Task 1 is a geological description of the reservoirs including petrophysical properties, i.e., porosity, permeability, permeability variation, formation depth, temperature, and net pay, facies changes and reservoir structures as drawn from cores, well logs, and other geological data. Task 2 is reservoir fluid characterization-determination of physical properties of reservoir fluids including density, viscosity, phase distributions and composition as well as petrogenesis-source rock identification; and the study of asphaltene precipitation for Alaskan crude oils. Results are discussed.
Characterization of oil and gas reservoir heterogeneity
Sharma, G.D.
1992-01-01
The ultimate objective of this cooperative research project is to characterize Alaskan petroleum reservoirs in terms of their reserves, physical and chemical properties, geologic configuration in relation to lithofacies and structure, and development potential. The project has two tasks: Task 1 is a geological description of the reservoirs including petrophysical properties, i.e., porosity, permeability, permeability variation, formation depth, temperature, and net pay, facies changes and reservoir structures as drawn from cores, well logs, and other geological data. Task 2 is reservoir fluid characterization -- determination of physical properties of reservoir fluids including density, viscosity, phase distributions and composition as well as petrogenesis -- source rock identification; and the study of asphaltene precipitation for Alaskan crude oils.
Rodent reservoirs of future zoonotic diseases.
Han, Barbara A; Schmidt, John Paul; Bowden, Sarah E; Drake, John M
2015-06-02
The increasing frequency of zoonotic disease events underscores a need to develop forecasting tools toward a more preemptive approach to outbreak investigation. We apply machine learning to data describing the traits and zoonotic pathogen diversity of the most speciose group of mammals, the rodents, which also comprise a disproportionate number of zoonotic disease reservoirs. Our models predict reservoir status in this group with over 90% accuracy, identifying species with high probabilities of harboring undiscovered zoonotic pathogens based on trait profiles that may serve as rules of thumb to distinguish reservoirs from nonreservoir species. Key predictors of zoonotic reservoirs include biogeographical properties, such as range size, as well as intrinsic host traits associated with lifetime reproductive output. Predicted hotspots of novel rodent reservoir diversity occur in the Middle East and Central Asia and the Midwestern United States.
Characterization of oil and gas reservoir heterogeneity
Sharma, G.D.
1992-01-01
The ultimate oojective of this cooperative research project is to characterize Alaskan petroleum reservoirs in terms of their reserves, physical and chemical properties, geologic configuration in relation to lithofacies and structure, and development potential. The project has two tasks: Task 1 is a geological description of the reservoirs including petrophysical properties, i.e., porosity, permeability, permeability variation, formation depth, temperature, and net pay, facies changes and reservoir structures as drawn from cores, well logs, and other geological data. Task 2 is reservoir fluid characterization--determination of physical properties of reservoir fluids including density, viscosity, phase distributions and composition as well as petrogenesis--source rock identification; and the study of asphaltene precipitation for Alaskan crude oils. This report presents a summary of technical progress of the well log analysis of Kuparuk Field, Northslope, Alaska.
Next generation oil reservoir simulations
Joubert, W.
1996-04-01
This paper describes a collaborative effort between Amoco Production Company, Los Alamos National Laboratory and Cray Research Inc. to develop a next-generation massively parallel oil reservoir simulation code. The simulator, code-named Falcon, enables highly detailed simulations to be performed on a range of platforms such as the Cray T3D and T3E. The code is currently being used by Amoco to perform a sophisticated field study using multiple geostatistical realizations on a scale of 2-5 million grid blocks and 1000-2000 wells. In this paper we discuss the nature of this collaborative effort, the software design and engineering aspects of the code, parallelization experiences, and performance studies. The code will be marketed to the oil industry by a third-party independent software vendor in mid-1996.
NASA Astrophysics Data System (ADS)
Ezzedine, S. M.
2010-12-01
Fractures and fracture networks are the principle pathways for migration of water, heat and mass in enhanced geothermal systems, oil and gas reservoirs, CO2 leakage from saline aquifers, and radioactive and toxic industrial wastes from underground storage repositories. A major issue to overcome when characterizing a fractured reservoir is that of data limitation due to accessibility and affordability. Moreover, the ability to map discontinuities in the rock with available geological and geophysical tools tends to decrease particularly as the scale of the discontinuity goes down. Geological characterization data include measurements of fracture density, orientation, extent, and aperture, and are based on analysis of outcrops, borehole optical and acoustic televiewer logs, aerial photographs, and core samples among others. All of these measurements are taken at the field scale through a very sparse limited number of deep boreholes. These types of data are often reduced to probability distributions function for predictive modeling and simulation in a stochastic framework such as stochastic discrete fracture network. Stochastic discrete fracture network models enable, through Monte Carlo realizations and simulations, for probabilistic assessment of flow and transport phenomena that are not adequately captured using continuum models. Despite the fundamental uncertainties inherited within the probabilistic reduction of the sparse data collected, very little work has been conducted on quantifying uncertainty on the reduced probabilistic distribution functions. In the current study, using nested Monte Carlo simulations, we present the impact of parameter uncertainties of the distribution functions that characterize discrete fracture networks on the flow, heat and mass transport. Numerical results of first, second and third moments, normalized to a base case scenario, are presented and compared to theoretical results extended from percolation theory.
Discrete dark solitons with multiple holes.
Susanto, Hadi; Johansson, Magnus
2005-07-01
We consider staggered dark solitons admitted by the discrete nonlinear Schrödinger equation with focusing cubic nonlinearity. In particular, we focus on the study of dark solitons with several holes characterized by the number of zeros in the uncoupled case. Such structures reveal interesting behaviors, such as stable intersite dark solitons. All of the structures have no counterpart in the strong coupling limit since they disappear in a saddle-node bifurcation. We also consider the evolution of structures with multiple holes representing an interaction between multiple dark solitons in a very discrete case.
Optical Planar Discrete Fourier and Wavelet Transforms
NASA Astrophysics Data System (ADS)
Cincotti, Gabriella; Moreolo, Michela Svaluto; Neri, Alessandro
2007-10-01
We present all-optical architectures to perform discrete wavelet transform (DWT), wavelet packet (WP) decomposition and discrete Fourier transform (DFT) using planar lightwave circuits (PLC) technology. Any compact-support wavelet filter can be implemented as an optical planar two-port lattice-form device, and different subband filtering schemes are possible to denoise, or multiplex optical signals. We consider both parallel and serial input cases. We design a multiport decoder/decoder that is able to generate/process optical codes simultaneously and a flexible logarithmic wavelength multiplexer, with flat top profile and reduced crosstalk.
Synchronization Of Parallel Discrete Event Simulations
NASA Technical Reports Server (NTRS)
Steinman, Jeffrey S.
1992-01-01
Adaptive, parallel, discrete-event-simulation-synchronization algorithm, Breathing Time Buckets, developed in Synchronous Parallel Environment for Emulation and Discrete Event Simulation (SPEEDES) operating system. Algorithm allows parallel simulations to process events optimistically in fluctuating time cycles that naturally adapt while simulation in progress. Combines best of optimistic and conservative synchronization strategies while avoiding major disadvantages. Algorithm processes events optimistically in time cycles adapting while simulation in progress. Well suited for modeling communication networks, for large-scale war games, for simulated flights of aircraft, for simulations of computer equipment, for mathematical modeling, for interactive engineering simulations, and for depictions of flows of information.
Feedback nonlinear discrete-time systems
NASA Astrophysics Data System (ADS)
Yu, Miao; Wang, Jiasen; Qi, Donglian
2014-11-01
In this paper, we design an adaptive iterative learning control method for a class of high-order nonlinear output feedback discrete-time systems with random initial conditions and iteration-varying desired trajectories. An n-step ahead predictor approach is employed to estimate future outputs. The discrete Nussbaum gain method is incorporated into the control design to deal with unknown control directions. The proposed control algorithm ensures that the tracking error converges to zero asymptotically along the iterative learning axis except for the beginning outputs affected by random initial conditions. A numerical simulation is carried out to demonstrate the efficacy of the presented control laws.
13. VIEW OF PORTLAND RESERVOIR NO. 2, LOOKING EAST FROM ...
13. VIEW OF PORTLAND RESERVOIR NO. 2, LOOKING EAST FROM NORTHWEST CORNER OF RESERVOIR. POST OF ORIGINAL FENCE IS IN FOREGROUND - Portland Reservoir No. 2, 6007 Southeast Division Street, Portland, Multnomah County, OR
9. VIEW OF PORTLAND RESERVOIR NO. 2, LOOKING SOUTHWEST, SHOWING ...
9. VIEW OF PORTLAND RESERVOIR NO. 2, LOOKING SOUTHWEST, SHOWING CHAIN-LINK FENCE IN FOREGROUND AND FOUNDATION STRUCTURE IN THE MIDDLE OF RESERVOIR BASIN - Portland Reservoir No. 2, 6007 Southeast Division Street, Portland, Multnomah County, OR
10. 'Y' CONNECTOR TO PICACHO RESERVOIR ON MAIN CANAL. VIEW ...
10. 'Y' CONNECTOR TO PICACHO RESERVOIR ON MAIN CANAL. VIEW LOOKING EAST FROM PICACHO RESERVOIR INLET CHANNEL - San Carlos Irrigation Project, Marin Canal, Amhurst-Hayden Dam to Picacho Reservoir, Coolidge, Pinal County, AZ
The Obtaining of Oil from an Oil Reservoir.
ERIC Educational Resources Information Center
Dawe, R. A.
1979-01-01
Discusses the mechanics of how an actual oil reservoir works and provides some technical background in physics. An experiment which simulates an oil reservoir and demonstrates quantitatively all the basic concepts of oil reservoir rock properties is also presented. (HM)
The Potosi Reservoir Model 2013
Adushita, Yasmin; Smith, Valerie; Leetaru, Hannes
2014-09-30
As a part of a larger project co-funded by the United States Department of Energy (US DOE) to evaluate the potential of formations within the Cambro-Ordovician strata above the Mt. Simon as potential targets for carbon sequestration in the Illinois and Michigan Basins, the Illinois Clean Coal Institute (ICCI) requested Schlumberger to evaluate the potential injectivity and carbon dioxide (CO2) plume size of the Cambrian Potosi Formation. The evaluation of this formation was accomplished using wireline data, core data, pressure data, and seismic data from the US DOE-funded Illinois Basin–Decatur Project (IBDP) being conducted by the Midwest Geological Sequestration Consortium in Macon County, Illinois. In 2010, technical performance evaluations on the Cambrian Potosi Formation were performed through reservoir modeling. The data included formation tops from mud logs, well logs from the VW1 and the CCS1 wells, structural and stratigraphic formation from three dimensional (3D) seismic data, and field data from several waste water injection wells for Potosi Formation. Intention was for two million tons per annum (MTPA) of CO2 to be injected for 20 years. In the preceding, the 2010 Potosi heterogeneous model (referred to as the "Potosi Dynamic Model 2010" in this topical report) was re-run using a new injection scenario; 3.2 MTPA for 30 years. The extent of the Potosi Dynamic Model 2010, however, appeared too small for the new injection target. It was not sufficiently large enough to accommodate the evolution of the plume. The new model, Potosi Dynamic Model 2013a, was built by extending the Potosi Dynamic Model 2010 grid to 30 miles x 30 miles (48.3km x48.3km), while preserving all property modeling workflows and layering. This model was retained as the base case of Potosi Dynamic Model 2013a. The Potosi reservoir model was updated to take into account the new data from the verification well VW2 which was drilled in 2012. The new porosity and permeability modeling was
NASA Astrophysics Data System (ADS)
Niederau, Jan; Gomez, Sergio; Ebigbo, Anozie; Inversi, Barbara; Marquart, Gabriele; Scrocca, Davide
2015-04-01
In this work, we present the results of hydrothermal simulations for assessing the geothermal potential of a fractured carbonate reservoir in Campania (Guardia Lombardi). Local surface heat flows of up to 90 mW/m² suggest that this area is a potential medium-enthalpy geothermal reservoir. The targeted reservoir rocks are fractured shallow-water carbonates (Jurassic to Cretaceous) of the Apulia Platform. During the Apennine orogeny, those carbonates were affected by at least two tectonic phases: Thrust-related folding of the carbonate platform due to compression followed by extension which caused major normal faulting. Based on seismic interpretation, a discretized structural model is set up, comprising the reservoir unit and the overlying sedimentary cover. The model comprises an area of 42 km × 28 km and extends to a depth of about six kilometers. Results of calibrated hydrothermal reservoir simulations suggest that free convection occurs in some parts of the reservoir. For assessing optimal locations for potential hydrothermal doublet systems, a tool was developed which uses the results of the reservoir simulationsin combination with predefined constraints. Those constraints or minimum requirements consider: a) minimum temperature for operating the doublet system, b) minimum matrix permeability allowing for a pumping rate of 40 L/s, and c) social constraints (location of cities or conservation areas, where the construction of a potential geothermal energy plant would be problematic). The optimization tool ranks possible doublet system locations by evaluating an objective function for the minimum requirements. Those locations are further used to extract smaller models from the big reservoir model and simulate the operation of a hypothetical geothermal doublet system. By assessing the optimized results, an optimal location of a geothermal energy plant would produce water with a temperature of 163 °C from a depth of almost 4 km.
Cabrera de Casas, L.; Chacartegui, F. )
1993-02-01
The main purpose of this study was to characterize the Upper Eocene C-2 reservoir using sedimentological, petrophysical and biostratigraphic parameters. The reservoir quality was evaluated by defining its physical attributes, geometry, areal distribution and orientation, from facies analysis of sedimentary units identified in core samples. In evaluating the sedimentary features of the Misoa C-2 reservoir in VLE 305/326 area, Block V, Lamar Field, Maracaibo Lake, 2,000' of cores from five wells (named VLe-339, VLE-720, VLE -723, VLe-754, LPG-1211) were analyzed. The sedimentary sequence studied represents upper-middle deltaic plain deposits with no marine influence. These deposits were identified as interdistributary channels, crevasse splays and interdistributary bays deposited in a northward prograding system. Seven sedimentary facies were defined from the physical, chemical and biological features observed in all cores. These facies were petrophysically and petrographically characterized then grouped in six sedimentary units which were then correlated over the entire area. One hundred well logs were correlated using sedimentological criteria. Finally, four flow units were identified in the reservoir using the sedimentological parameters, petrophysical data and production behavior. A surface trend analysis program utilizing thickness values resulted in contours, trends, residuals and isometry maps of each unit with a generalized southwest-northeast trend orientation. It was determined that facies distribution in the units controls the reservoir quality. These results are the main input into reservoir simulation. An accurate reservoir modeling is needed to prepare for optimizing secondary oil recovery.
Exploration of the lower permeability reservoir in Sanzhao area of Songliao Basin
Ding Guiming; Wang Yuxin )
1996-01-01
Sanzhao area is an independent petroleum generation-migration-accumulation unit that concentrates in the Sanzhao sag, a large sag in the central depression of Songliao basin. The oil generated from the Lower Cretaceous Qingshankou Formation migrated into Fuyu and Yangdachengzi reservoirs in Members 3 and 4 of the Quantou Formation, with the overpressure of the source bed driving fluids through dense fault pathways. Fuyu and Yangdachengzi reserviors are formed by areally-extensive, fluviodeltaic thin interbedded sandstones. Most of the oil pools in Sanzhao area are in low-permeability lithologies. In order to prospect for these lower permeability reservoirs, first we set evaluation and oil/gas reservoir evaluation. On the basis of the composite study of petroleum geology, the low-permeability feature of Fuyu and Yangdachengzi reservoirs has been further understood. Secondly, we have developed a series of exploration methods and techniques, including high-resolution seismic exploration, oil testing and fracturing, and techniques for protecting oil reservoirs. Due to breakthrough in understanding of petroleum geology and the development of composite exploration techniques, the low-permeability reservoirs of Sanzhao area have liberated abundant reservers. A large, low-permeability oil province with reserves of more than 10x10[sup 8] has been proven.
Exploration of the lower permeability reservoir in Sanzhao area of Songliao Basin
Ding Guiming; Wang Yuxin
1996-12-31
Sanzhao area is an independent petroleum generation-migration-accumulation unit that concentrates in the Sanzhao sag, a large sag in the central depression of Songliao basin. The oil generated from the Lower Cretaceous Qingshankou Formation migrated into Fuyu and Yangdachengzi reservoirs in Members 3 and 4 of the Quantou Formation, with the overpressure of the source bed driving fluids through dense fault pathways. Fuyu and Yangdachengzi reserviors are formed by areally-extensive, fluviodeltaic thin interbedded sandstones. Most of the oil pools in Sanzhao area are in low-permeability lithologies. In order to prospect for these lower permeability reservoirs, first we set evaluation and oil/gas reservoir evaluation. On the basis of the composite study of petroleum geology, the low-permeability feature of Fuyu and Yangdachengzi reservoirs has been further understood. Secondly, we have developed a series of exploration methods and techniques, including high-resolution seismic exploration, oil testing and fracturing, and techniques for protecting oil reservoirs. Due to breakthrough in understanding of petroleum geology and the development of composite exploration techniques, the low-permeability reservoirs of Sanzhao area have liberated abundant reservers. A large, low-permeability oil province with reserves of more than 10x10{sup 8} has been proven.
An improved reservoir for the flushing test to diagnose shunt insufficiency.
Schlosser, Hans-Georg; Crawack, Hans-Joachim; Miethke, Christoph; Knitter, Thoralf; Zeiner, Andreas; Sprung, Christian
2016-09-01
OBJECTIVE Reservoirs integrated into hydrocephalus shunts are commonly used for the removal of CSF and for intra-ventricular pressure measurement. Pumping with the reservoir to diagnose shunt sufficiency is still a matter of controversy. The authors describe an improved flushing device and its characteristic features in vitro and in vivo. METHODS The flushing reservoir is constructed with a sapphire ball in a cage as a nonresistance valve to also enable the detection of distal occlusions. The most important reservoir parameters were investigated in vitro, simulating total and partial proximal and distal shunt occlusions. Then the expected advantages were assessed in vivo by evaluating the pump test data of 360 implanted reservoirs. The results were compared with those found in the literature. RESULTS The optimization of the technical parameters of the device, such as the high stroke volume in combination with moderate suction force, are obvious advantages compared with other flushing devices. Total occlusion of the ventricular catheter and the valve could be assessed with high certainty. The detection of a total obstruction of the peritoneal catheter or any partial obstruction is also possible, depending on its exact grade and location. CONCLUSIONS Shunt obstructions can be assessed using the pumping test. The reservoir construction presented here provides a clear enhancement of that diagnostic test.
Kerans, C.
1988-01-01
Ellenburger Group reservoirs constitute a major play in the Permian basin of west Texas, with over 1.4 billion bbl cumulative production through 1985. These reservoirs typically have been developed by assuming homogeneous fracture-related pore system. Examination of core, log, and production data demonstrates that most Ellenburger reservoirs are characterized by pronounced vertical and lateral heterogeneities created by post-Ellenburger karst development. Vertical reservoir compartmentalization in the Ellenburger evolved from development of a laterally extensive cave system between 100 and 300 ft beneath the original land surface. Caves were filled by relatively impermeable siliciclastics from the overlying Simpson Group, effectively isolating permeable cave-roof breccias (uppermost Ellenburger) from collapse breccias deposited on cave floors prior to shale infill. Lateral compartmentalization of Ellenburger reservoirs originated by localized collapse of the cave system both during karst formation and after burial. In the Shafter Lake field, lateral compartmentalization is the result of a 200-ft vertical collapse during deposition of Simpson Group sands. Abrupt lateral discontinuities in the Big Lake and Glasco fields may represent similar collapse-related features, such as are spectacularly displayed in Ellenburger-equivalent outcrops of the Franklin Mountains. An estimated 750 million bbl of remaining mobile oil, in addition to conventional reserves, occurs in this mature but complexly compartmentalized play. Considering this paleokarst model will aid in further exploitation of Ellenburger reservoirs.
Equation-Free Effective Computation for Discrete Systems: a Time Stepper Based Approach
NASA Astrophysics Data System (ADS)
Möller, J.; Runborg, O.; Kevrekidis, P. G.; Lust, K.; Kevrekidis, I. G.
We propose a computer-assisted approach to studying the effective continuum behavior of spatially discrete evolution equations. The advantage of the approach is that the "coarse model" (the continuum, effective equation) need not be explicitly constructed. The method only uses a time-integration code for the discrete problem and judicious choices of initial data and integration times; our bifurcation computations are based on the so-called Recursive Projection Method (RPM) with arc-length continuation [Shroff & Keller, 1993]. The technique is used to monitor features of the genuinely discrete problem such as the pinning of coherent structures and its results are compared to quasi-continuum approaches such as the ones based on Padé approximations.
Discrete phase changes within nonlinear steepened magnetosonic waves - Comet Giacobini-Zinner
NASA Technical Reports Server (NTRS)
Tsurutani, Bruce T.; Smith, Edward J.; Buti, B.; Matsumoto, Hiroshi; Brinca, Armando
1990-01-01
Some features of steepened magnetosonic waves are discussed with reference to the Giacobini-Zinner data set. In particular, attention is given to the discovery of discrete intervals of both phase rotation and lack of phase rotation within a single wavelength and also to the presence of intervals of 'backward' rotations (right-hand polarized in the spacecraft frame) within the magnetosonic wave. Possible explanations of these features are reviewed, and it is suggested that these features are nonlinear manifestations of the wave steepening process.
Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions
Wotzlaw, Jörn-Frederik; Bindeman, Ilya N.; Stern, Richard A.; D’Abzac, Francois-Xavier; Schaltegger, Urs
2015-01-01
Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 103 to 104 years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption. PMID:26356304
Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions.
Wotzlaw, Jörn-Frederik; Bindeman, Ilya N; Stern, Richard A; D'Abzac, Francois-Xavier; Schaltegger, Urs
2015-09-10
Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 10(3) to 10(4) years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption.
Online feature selection with streaming features.
Wu, Xindong; Yu, Kui; Ding, Wei; Wang, Hao; Zhu, Xingquan
2013-05-01
We propose a new online feature selection framework for applications with streaming features where the knowledge of the full feature space is unknown in advance. We define streaming features as features that flow in one by one over time whereas the number of training examples remains fixed. This is in contrast with traditional online learning methods that only deal with sequentially added observations, with little attention being paid to streaming features. The critical challenges for Online Streaming Feature Selection (OSFS) include 1) the continuous growth of feature volumes over time, 2) a large feature space, possibly of unknown or infinite size, and 3) the unavailability of the entire feature set before learning starts. In the paper, we present a novel Online Streaming Feature Selection method to select strongly relevant and nonredundant features on the fly. An efficient Fast-OSFS algorithm is proposed to improve feature selection performance. The proposed algorithms are evaluated extensively on high-dimensional datasets and also with a real-world case study on impact crater detection. Experimental results demonstrate that the algorithms achieve better compactness and higher prediction accuracy than existing streaming feature selection algorithms.
Carr, T.P.; Guy, W.J.; Franseen, E.K.; Bhattacharya, S.
1996-12-31
The Pennsylvanian-Mississippian unconformity is a major stratigraphic event in Kansas that truncates rocks ranging from Precambrian to Mississippian. Many of the 6,000 fields in Kansas are located immediately beneath this unconformity. One example, Schaben Field located in Ness County, Kansas, has produced approximately 9 million barrels since it was discovered in 1963. Production is from the Mississippian (Osagian) cherty dolomites beneath the inconformity. The field was initially developed on a regular forty-acre spacing, but recent drilling has demonstrated the potential for additional targeted infill drilling. To develop an enhanced reservoir model for the Schabin field modern core, log, and well data were integrated with the existing data. New techniques such as {open_quotes}Pseudoseismic{close_quotes} and the {open_quotes}Super{close_quotes} Pickett plot were used to leverage the existing data and provide tools for analysis and 3D visualization. The pseudoseismic approach uses well-logs within a standard 3D seismic visualization system to provide a detailed macroscale view of karst patterns. The petrophysical analyses using the {open_quotes}Super{close_quotes} Pickett plot were used to recognize subtle trends and patterns for each of multiple reservoir intervals. Visual and petrographic examination of core from the field confirms karst development and indicates multiple stages of fracturing, brecciation, and dissolution features that were important in controlling and modifying development of reservoirs. The understanding of the reservoir heterogeneities resulting from the paleokarst model at Schaben field emphasizes the importance of integrating available data with new techniques to provide a predictive tool for discovery of additional pay within existing subunconformity fields in Kansas.
Carr, T.P.; Guy, W.J.; Franseen, E.K.; Bhattacharya, S. )
1996-01-01
The Pennsylvanian-Mississippian unconformity is a major stratigraphic event in Kansas that truncates rocks ranging from Precambrian to Mississippian. Many of the 6,000 fields in Kansas are located immediately beneath this unconformity. One example, Schaben Field located in Ness County, Kansas, has produced approximately 9 million barrels since it was discovered in 1963. Production is from the Mississippian (Osagian) cherty dolomites beneath the inconformity. The field was initially developed on a regular forty-acre spacing, but recent drilling has demonstrated the potential for additional targeted infill drilling. To develop an enhanced reservoir model for the Schabin field modern core, log, and well data were integrated with the existing data. New techniques such as [open quotes]Pseudoseismic[close quotes] and the [open quotes]Super[close quotes] Pickett plot were used to leverage the existing data and provide tools for analysis and 3D visualization. The pseudoseismic approach uses well-logs within a standard 3D seismic visualization system to provide a detailed macroscale view of karst patterns. The petrophysical analyses using the [open quotes]Super[close quotes] Pickett plot were used to recognize subtle trends and patterns for each of multiple reservoir intervals. Visual and petrographic examination of core from the field confirms karst development and indicates multiple stages of fracturing, brecciation, and dissolution features that were important in controlling and modifying development of reservoirs. The understanding of the reservoir heterogeneities resulting from the paleokarst model at Schaben field emphasizes the importance of integrating available data with new techniques to provide a predictive tool for discovery of additional pay within existing subunconformity fields in Kansas.
5. EASTSIDE RESERVOIR, LOOKING WEST. WEST DAM UNDER CONSTRUCTION, QUARRIES ...
5. EASTSIDE RESERVOIR, LOOKING WEST. WEST DAM UNDER CONSTRUCTION, QUARRIES TO LEFT MIDDLE GROUND OF PICTURE. - Eastside Reservoir, Diamond & Domenigoni Valleys, southwest of Hemet, Hemet, Riverside County, CA
Stable discrete representation of relativistically drifting plasmas
NASA Astrophysics Data System (ADS)
Kirchen, M.; Lehe, R.; Godfrey, B. B.; Dornmair, I.; Jalas, S.; Peters, K.; Vay, J.-L.; Maier, A. R.
2016-10-01
Representing the electrodynamics of relativistically drifting particle ensembles in discrete, co-propagating Galilean coordinates enables the derivation of a Particle-In-Cell algorithm that is intrinsically free of the numerical Cherenkov instability for plasmas flowing at a uniform velocity. Application of the method is shown by modeling plasma accelerators in a Lorentz-transformed optimal frame of reference.
A deterministic discrete ordinates transport proxy application
2014-06-03
Kripke is a simple 3D deterministic discrete ordinates (Sn) particle transport code that maintains the computational load and communications pattern of a real transport code. It is intended to be a research tool to explore different data layouts, new programming paradigms and computer architectures.
Applied Behavior Analysis: Beyond Discrete Trial Teaching
ERIC Educational Resources Information Center
Steege, Mark W.; Mace, F. Charles; Perry, Lora; Longenecker, Harold
2007-01-01
We discuss the problem of autism-specific special education programs representing themselves as Applied Behavior Analysis (ABA) programs when the only ABA intervention employed is Discrete Trial Teaching (DTT), and often for limited portions of the school day. Although DTT has many advantages to recommend its use, it is not well suited to teach…
Conjugacy classes in discrete Heisenberg groups
Budylin, R Ya
2014-08-01
We study an extension of a discrete Heisenberg group coming from the theory of loop groups and find invariants of conjugacy classes in this group. In some cases, including the case of the integer Heisenberg group, we make these invariants more explicit. Bibliography: 4 titles.
The Discrete Site Sticky Wall Model.
1986-05-27
TECHNICAL REPORT #23 THE DISCRETE SITE STICKY WALL tMDEL by J.P. Badiali Laboratoire Propre No 15 de CNRS Physique des Liquides et Electrochimie Tour 22, 5e...Liquides et Electrochimie NTIS CRA&I DTIC TAB 5 Tour 22, 5e Etage, 4 Place Jussieu U’annou;.ced . J ’ tificatlo rn
Discrete Event Simulation of Distributed Team Communication
2012-03-22
executable system architecture approach to discrete events system modeling using sysml in conjunction with colored petri net . In Systems Conference, 2008 2nd...operators. Mitchell found that IMPRINT predictions of communication times and frequencies correlated with recorded communications amongst a platoon of
Discrete wavelength-locked external cavity laser
NASA Technical Reports Server (NTRS)
Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)
2005-01-01
An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.
Kinematics of foldable discrete space cranes
NASA Technical Reports Server (NTRS)
Nayfeh, A. H.
1985-01-01
Exact kinematic description of a NASA proposed prototype foldable-deployable discrete space crane are presented. A computer program is developed which maps the geometry of the crane once controlling parameters are specified. The program uses a building block type approach in which it calculates the local coordinates of each repeating cell and then combines them with respect to a global coordinates system.
Discrete Events as Units of Perceived Time
ERIC Educational Resources Information Center
Liverence, Brandon M.; Scholl, Brian J.
2012-01-01
In visual images, we perceive both space (as a continuous visual medium) and objects (that inhabit space). Similarly, in dynamic visual experience, we perceive both continuous time and discrete events. What is the relationship between these units of experience? The most intuitive answer may be similar to the spatial case: time is perceived as an…
Discrete Gust Model for Launch Vehicle Assessments
NASA Technical Reports Server (NTRS)
Leahy, Frank B.
2008-01-01
Analysis of spacecraft vehicle responses to atmospheric wind gusts during flight is important in the establishment of vehicle design structural requirements and operational capability. Typically, wind gust models can be either a spectral type determined by a random process having a wide range of wavelengths, or a discrete type having a single gust of predetermined magnitude and shape. Classical discrete models used by NASA during the Apollo and Space Shuttle Programs included a 9 m/sec quasi-square-wave gust with variable wavelength from 60 to 300 m. A later study derived discrete gust from a military specification (MIL-SPEC) document that used a "1-cosine" shape. The MIL-SPEC document contains a curve of non-dimensional gust magnitude as a function of non-dimensional gust half-wavelength based on the Dryden spectral model, but fails to list the equation necessary to reproduce the curve. Therefore, previous studies could only estimate a value of gust magnitude from the curve, or attempt to fit a function to it. This paper presents the development of the MIL-SPEC curve, and provides the necessary information to calculate discrete gust magnitudes as a function of both gust half-wavelength and the desired probability level of exceeding a specified gust magnitude.
Neutrino mass and mixing with discrete symmetry.
King, Stephen F; Luhn, Christoph
2013-05-01
This is a review paper about neutrino mass and mixing and flavour model building strategies based on discrete family symmetry. After a pedagogical introduction and overview of the whole of neutrino physics, we focus on the PMNS mixing matrix and the latest global fits following the Daya Bay and RENO experiments which measure the reactor angle. We then describe the simple bimaximal, tri-bimaximal and golden ratio patterns of lepton mixing and the deviations required for a non-zero reactor angle, with solar or atmospheric mixing sum rules resulting from charged lepton corrections or residual trimaximal mixing. The different types of see-saw mechanism are then reviewed as well as the sequential dominance mechanism. We then give a mini-review of finite group theory, which may be used as a discrete family symmetry broken by flavons either completely, or with different subgroups preserved in the neutrino and charged lepton sectors. These two approaches are then reviewed in detail in separate chapters including mechanisms for flavon vacuum alignment and different model building strategies that have been proposed to generate the reactor angle. We then briefly review grand unified theories (GUTs) and how they may be combined with discrete family symmetry to describe all quark and lepton masses and mixing. Finally, we discuss three model examples which combine an SU(5) GUT with the discrete family symmetries A₄, S₄ and Δ(96).
5 CFR 572.102 - Agency discretion.
Code of Federal Regulations, 2010 CFR
2010-01-01
... and transportation or interview expenses in filling any position, the agency should consider such factors as availability of funds as well as the desirability of conducting interviews for a particular job... TRANSPORTATION EXPENSES; NEW APPOINTEES AND INTERVIEWS § 572.102 Agency discretion. Payment of travel...
Teaching Discrete Mathematics with Graphing Calculators.
ERIC Educational Resources Information Center
Masat, Francis E.
Graphing calculator use is often thought of in terms of pre-calculus or continuous topics in mathematics. This paper contains examples and activities that demonstrate useful, interesting, and easy ways to use a graphing calculator with discrete topics. Examples are given for each of the following topics: functions, mathematical induction and…
Failure diagnosis using discrete event models
Sampath, M.; Sengupta, R.; Lafortune, S.; Teneketzis, D.; Sinnamohideen, K.
1994-12-31
We propose a Discrete Event Systems (DES) approach to the failure diagnosis problem. We present a methodology for modeling physical systems in a DES framework. We discuss the notion of diagnosability and present the construction procedure of the diagnoser. Finally, we illustrate our approach using a Heating, Ventilation and Air Conditioning (HVAC) system.
Analysis hierarchical model for discrete event systems
NASA Astrophysics Data System (ADS)
Ciortea, E. M.
2015-11-01
The This paper presents the hierarchical model based on discrete event network for robotic systems. Based on the hierarchical approach, Petri network is analysed as a network of the highest conceptual level and the lowest level of local control. For modelling and control of complex robotic systems using extended Petri nets. Such a system is structured, controlled and analysed in this paper by using Visual Object Net ++ package that is relatively simple and easy to use, and the results are shown as representations easy to interpret. The hierarchical structure of the robotic system is implemented on computers analysed using specialized programs. Implementation of hierarchical model discrete event systems, as a real-time operating system on a computer network connected via a serial bus is possible, where each computer is dedicated to local and Petri model of a subsystem global robotic system. Since Petri models are simplified to apply general computers, analysis, modelling, complex manufacturing systems control can be achieved using Petri nets. Discrete event systems is a pragmatic tool for modelling industrial systems. For system modelling using Petri nets because we have our system where discrete event. To highlight the auxiliary time Petri model using transport stream divided into hierarchical levels and sections are analysed successively. Proposed robotic system simulation using timed Petri, offers the opportunity to view the robotic time. Application of goods or robotic and transmission times obtained by measuring spot is obtained graphics showing the average time for transport activity, using the parameters sets of finished products. individually.
Electroless plating apparatus for discrete microsized particles
Mayer, Anton
1978-01-01
Method and apparatus are disclosed for producing very uniform coatings of a desired material on discrete microsized particles by electroless techniques. Agglomeration or bridging of the particles during the deposition process is prevented by imparting a sufficiently random motion to the particles that they are not in contact with each other for a time sufficient for such to occur.
Geometric Representations for Discrete Fourier Transforms
NASA Technical Reports Server (NTRS)
Cambell, C. W.
1986-01-01
Simple geometric representations show symmetry and periodicity of discrete Fourier transforms (DFT's). Help in visualizing requirements for storing and manipulating transform value in computations. Representations useful in any number of dimensions, but particularly in one-, two-, and three-dimensional cases often encountered in practice.
A Note on Discrete Mathematics and Calculus.
ERIC Educational Resources Information Center
O'Reilly, Thomas J.
1987-01-01
Much of the current literature on the topic of discrete mathematics and calculus during the first two years of an undergraduate mathematics curriculum is cited. A relationship between the recursive integration formulas and recursively defined polynomials is described. A Pascal program is included. (Author/RH)