Performance evaluation of two OCR systems
Chen, S.; Subramaniam, S.; Haralick, R.M.; Phillips, I.T.
1994-12-31
An experimental protocol for the performance evaluation of Optical Character Recognition (OCR) algorithms is described. The protocol is intended to serve as a model for using the University of Washington English Document Image Database-I to evaluate OCR systems. The plain text zones (without special symbols) in this database have over 2,300,000 characters. The performances of two UNIX-based OCR systems, namely Caere OCR v109a and Xerox ScanWorX v2.0, are measured. The results suggest that Caere OCR outperforms ScanWorX in terms of recognition accuracy; however, ScanWorX is more robust in the presence of image flaws.
The BBN Byblos Hindi OCR system
NASA Astrophysics Data System (ADS)
Natarajan, Premkumar S.; MacRostie, Ehry; Decerbo, Michael
2005-01-01
The BBN Byblos OCR system implements a script-independent methodology for OCR using Hidden Markov Models (HMMs). We have successfully ported the system to Arabic, English, Chinese, Pashto, and Japanese. In this paper, we report on our recent effort in training the system to perform recognition of Hindi (Devanagari) documents. The initial experiments reported in this paper were performed using a corpus of synthetic (computer-generated) document images along with slightly degraded versions of the same that were generated by scanning printed versions of the document images and by scanning faxes of the printed versions. On a fair test set consisting of synthetic images alone we measured a character error rate of 1.0%. The character error rate on a fair test set consisting of scanned images (scans of printed versions of the synthetic images) was 1.40% while the character error rate on a fair test set of fax images (scans of printed and faxed versions of the synthetic images) was 8.7%.
The BBN Byblos Hindi OCR system
NASA Astrophysics Data System (ADS)
Natarajan, Premkumar S.; MacRostie, Ehry; Decerbo, Michael
2004-12-01
The BBN Byblos OCR system implements a script-independent methodology for OCR using Hidden Markov Models (HMMs). We have successfully ported the system to Arabic, English, Chinese, Pashto, and Japanese. In this paper, we report on our recent effort in training the system to perform recognition of Hindi (Devanagari) documents. The initial experiments reported in this paper were performed using a corpus of synthetic (computer-generated) document images along with slightly degraded versions of the same that were generated by scanning printed versions of the document images and by scanning faxes of the printed versions. On a fair test set consisting of synthetic images alone we measured a character error rate of 1.0%. The character error rate on a fair test set consisting of scanned images (scans of printed versions of the synthetic images) was 1.40% while the character error rate on a fair test set of fax images (scans of printed and faxed versions of the synthetic images) was 8.7%.
The BBN Byblos Hindi OCR System
NASA Astrophysics Data System (ADS)
Natarajan, Prem; Macrostie, Ehry; Decerbo, Michael
The BBN Byblos OCR system implements a script-independent methodology for OCR using hidden Markov models (HMMs). We have successfully ported the system to Arabic, English, Chinese, Pashto, and Japanese. In this chapter, we report on our recent effort in training the system to perform recognition of Hindi (Devanagari) documents. The initial experiments reported in this chapter were performed using a corpus of synthetic (computer-generated) document images along with slightly degraded versions of the same that were generated by scanning printed versions of the document images and by scanning faxes of the printed versions. On a fair test set consisting of synthetic images alone we measured a character error rate of 1.0%. The character error rate on a fair test set consisting of scanned images (scans of printed versions of the synthetic images) was 1.40% while the character error rate on a fair test set of fax images (scans of printed and faxed versions of the synthetic images) was 8.7%.
A multi-evidence, multi-engine OCR system
NASA Astrophysics Data System (ADS)
Zavorin, Ilya; Borovikov, Eugene; Borovikov, Anna; Hernandez, Luis; Summers, Kristen; Turner, Mark
2007-01-01
Although modern OCR technology is capable of handling a wide variety of document images, there is no single OCR engine that performs equally well on all documents for a given single language script. Naturally, each OCR engine has its strengths and weaknesses, and therefore different engines tend to differ in the accuracy on different documents, and in the errors on the same document image. While the idea of using multiple OCR engines to boost output accuracy is not new, most of the existing systems do not go beyond variations on majority voting. While this approach may work well in many cases, it has limitations, especially when OCR technology used to process a given script has not yet fully matured. Our goal is to develop a system called MEMOE (for "Multi-Evidence Multi-OCR-Engine") that combines, in an optimal or near-optimal way, output streams of one or more OCR engines together with various types of evidence extracted from these streams as well as from original document images, to produce output of higher quality than that of the individual OCR engines, or of majority voting applied to multiple OCR output streams. Furthermore, we aim to improve the accuracy of OCR output on images that might otherwise have low accuracy that significantly impacts downstream processing. The MEMOE system functions as an OCR engine taking document images and some configuration parameters as input and producing a single output text stream. In this paper, we describe the design of the system, various evidence types and how they are incorporated into MEMOE in the form of filters. Results of initial tests that involve two corpora of Arabic documents show that, even in its initial configuration, the system is superior to a voting algorithm and that even more improvement may be achieved by incorporating additional evidence types into the system.
Counting OCR errors in typeset text
NASA Astrophysics Data System (ADS)
Sandberg, Jonathan S.
1995-03-01
Frequently object recognition accuracy is a key component in the performance analysis of pattern matching systems. In the past three years, the results of numerous excellent and rigorous studies of OCR system typeset-character accuracy (henceforth OCR accuracy) have been published, encouraging performance comparisons between a variety of OCR products and technologies. These published figures are important; OCR vendor advertisements in the popular trade magazines lead readers to believe that published OCR accuracy figures effect market share in the lucrative OCR market. Curiously, a detailed review of many of these OCR error occurrence counting results reveals that they are not reproducible as published and they are not strictly comparable due to larger variances in the counts than would be expected by the sampling variance. Naturally, since OCR accuracy is based on a ratio of the number of OCR errors over the size of the text searched for errors, imprecise OCR error accounting leads to similar imprecision in OCR accuracy. Some published papers use informal, non-automatic, or intuitively correct OCR error accounting. Still other published results present OCR error accounting methods based on string matching algorithms such as dynamic programming using Levenshtein (edit) distance but omit critical implementation details (such as the existence of suspect markers in the OCR generated output or the weights used in the dynamic programming minimization procedure). The problem with not specifically revealing the accounting method is that the number of errors found by different methods are significantly different. This paper identifies the basic accounting methods used to measure OCR errors in typeset text and offers an evaluation and comparison of the various accounting methods.
Robust language-independent OCR system
NASA Astrophysics Data System (ADS)
Lu, Zhidong A.; Bazzi, Issam; Kornai, Andras; Makhoul, John; Natarajan, Premkumar S.; Schwartz, Richard
1999-01-01
We present a language-independent optical character recognition system that is capable, in principle, of recognizing printed text from most of the world's languages. For each new language or script the system requires sample training data along with ground truth at the text-line level; there is no need to specify the location of either the lines or the words and characters. The system uses hidden Markov modeling technology to model each character. In addition to language independence, the technology enhances performance for degraded data, such as fax, by using unsupervised adaptation techniques. Thus far, we have demonstrated the language-independence of this approach for Arabic, English, and Chinese. Recognition results are presented in this paper, including results on faxed data.
Boost OCR accuracy using iVector based system combination approach
NASA Astrophysics Data System (ADS)
Peng, Xujun; Cao, Huaigu; Natarajan, Prem
2015-01-01
Optical character recognition (OCR) is a challenging task because most existing preprocessing approaches are sensitive to writing style, writing material, noises and image resolution. Thus, a single recognition system cannot address all factors of real document images. In this paper, we describe an approach to combine diverse recognition systems by using iVector based features, which is a newly developed method in the field of speaker verification. Prior to system combination, document images are preprocessed and text line images are extracted with different approaches for each system, where iVector is transformed from a high-dimensional supervector of each text line and is used to predict the accuracy of OCR. We merge hypotheses from multiple recognition systems according to the overlap ratio and the predicted OCR score of text line images. We present evaluation results on an Arabic document database where the proposed method is compared against the single best OCR system using word error rate (WER) metric.
A robust omnifont open-vocabulary Arabic OCR system using pseudo-2D-HMM
NASA Astrophysics Data System (ADS)
Rashwan, Abdullah M.; Rashwan, Mohsen A.; Abdel-Hameed, Ahmed; Abdou, Sherif; Khalil, A. H.
2012-01-01
Recognizing old documents is highly desirable since the demand for quickly searching millions of archived documents has recently increased. Using Hidden Markov Models (HMMs) has been proven to be a good solution to tackle the main problems of recognizing typewritten Arabic characters. These attempts however achieved a remarkable success for omnifont OCR under very favorable conditions, they didn't achieve the same performance in practical conditions, i.e. noisy documents. In this paper we present an omnifont, large-vocabulary Arabic OCR system using Pseudo Two Dimensional Hidden Markov Model (P2DHMM), which is a generalization of the HMM. P2DHMM offers a more efficient way to model the Arabic characters, such model offer both minimal dependency on the font size/style (omnifont), and high level of robustness against noise. The evaluation results of this system are very promising compared to a baseline HMM system and best OCRs available in the market (Sakhr and NovoDynamics). The recognition accuracy of the P2DHMM classifier is measured against the classic HMM classifier, the average word accuracy rates for P2DHMM and HMM classifiers are 79% and 66% respectively. The overall system accuracy is measured against Sakhr and NovoDynamics OCR systems, the average word accuracy rates for P2DHMM, NovoDynamics, and Sakhr are 74%, 71%, and 61% respectively.
An automated system for numerically rating document image quality
Cannon, M.; Kelly, P.; Iyengar, S.S.; Brener, N.
1997-04-01
As part of the Department of Energy document declassification program, the authors have developed a numerical rating system to predict the OCR error rate that they expect to encounter when processing a particular document. The rating algorithm produces a vector containing scores for different document image attributes such as speckle and touching characters. The OCR error rate for a document is computed from a weighted sum of the elements of the corresponding quality vector. The predicted OCR error rate will be used to screen documents that would not be handled properly with existing document processing products.
An evaluation of information retrieval accuracy with simulated OCR output
Croft, W.B.; Harding, S.M.; Taghva, K.; Borsack, J.
1994-12-31
Optical Character Recognition (OCR) is a critical part of many text-based applications. Although some commercial systems use the output from OCR devices to index documents without editing, there is very little quantitative data on the impact of OCR errors on the accuracy of a text retrieval system. Because of the difficulty of constructing test collections to obtain this data, we have carried out evaluation using simulated OCR output on a variety of databases. The results show that high quality OCR devices have little effect on the accuracy of retrieval, but low quality devices used with databases of short documents can result in significant degradation.
ERIC Educational Resources Information Center
Sun, Wei; And Others
1992-01-01
Identifies types and distributions of errors in text produced by optical character recognition (OCR) and proposes a process using machine learning techniques to recognize and correct errors in OCR texts. Results of experiments indicating that this strategy can reduce human interaction required for error correction are reported. (25 references)…
Keyless Entry: Building a Text Database Using OCR Technology.
ERIC Educational Resources Information Center
Grotophorst, Clyde W.
1989-01-01
Discusses the use of optical character recognition (OCR) technology to produce an ASCII text database. A tutorial on digital scanning and OCR is provided, and a systems integration project which used the Calera CDP-3000XF scanner and text retrieval software to construct a database of dissertations at George Mason University is described. (four…
OCR Scanners Facilitate WP Training in Business Schools and Colleges.
ERIC Educational Resources Information Center
School Business Affairs, 1983
1983-01-01
Optical Character Recognition Scanners (OCR) scan typed text and feed it directly into word processing systems, saving input time. OCRs are valuable in word processing training programs because they allow more students access to classes and more time for skill training. (MD)
Kansas State University Libraries' OCR Labeling Project.
ERIC Educational Resources Information Center
Thierer, Joyce; Bower, Merry
This publication describes the planning and implementation of an optical character recognition (OCR) labeling project, the first stage of Kansas State University (KSU) Libraries' program of conversion from a manual to an automated circulation system. It is noted that a telephone survey of libraries with automated circulation systems and…
Prediction of OCR accuracy using simple image features
Blando, L.R.; Kanai, Junichi; Nartker, T.A.
1995-04-01
A classifier for predicting the character accuracy of a given page achieved by any Optical Character Recognition (OCR) system is presented. This classifier is based on measuring the amount of white speckle, the amount of character fragments, and overall size information in the page. No output from the OCR system is used. The given page is classified as either good quality (i.e., high OCR accuracy expected) or poor (i.e., low OCR accuracy expected). Six OCR systems processed two different sets of test data: a set of 439 pages obtained from technical and scientific documents and a set of 200 pages obtained from magazines. For every system, approximately 85% of the pages in each data set were correctly predicted. The performance of this classifier is also compared with the ideal-case performance of a prediction method based upon the number of reject markers in OCR generated text. In several cases, this method matched or exceeded the performance of the reject based approach.
Correcting OCR text by association with historical datasets
NASA Astrophysics Data System (ADS)
Hauser, Susan E.; Schlaifer, Jonathan; Sabir, Tehseen F.; Demner-Fushman, Dina; Straughan, Scott; Thoma, George R.
2003-01-01
The Medical Article Records System (MARS) developed by the Lister Hill National Center for Biomedical Communications uses scanning, OCR and automated recognition and reformatting algorithms to generate electronic bibliographic citation data from paper biomedical journal articles. The OCR server incorporated in MARS performs well in general, but fares less well with text printed in small or italic fonts. Affiliations are often printed in small italic fonts in the journals processed by MARS. Consequently, although the automatic processes generate much of the citation data correctly, the affiliation field frequently contains incorrect data, which must be manually corrected by verification operators. In contrast, author names are usually printed in large, normal fonts that are correctly converted to text by the OCR server. The National Library of Medicine"s MEDLINE database contains 11 million indexed citations for biomedical journal articles. This paper documents our effort to use the historical author, affiliation relationships from this large dataset to find potential correct affiliations for MARS articles based on the author and the affiliation in the OCR output. Preliminary tests using a table of about 400,000 author/affiliation pairs extracted from the corrected data from MARS indicated that about 44% of the author/affiliation pairs were repeats and that about 47% of newly converted author names would be found in this set. A text-matching algorithm was developed to determine the likelihood that an affiliation found in the table corresponding to the OCR text of the first author was the current, correct affiliation. This matching algorithm compares an affiliation found in the author/affiliation table (found with the OCR text of the first author) to the OCR output affiliation, and calculates a score indicating the similarity of the affiliation found in the table to the OCR affiliation. Using a ground truth set of 519 OCR author/OCR affiliation/correct affiliation
Robust keyword retrieval method for OCRed text
NASA Astrophysics Data System (ADS)
Fujii, Yusaku; Takebe, Hiroaki; Tanaka, Hiroshi; Hotta, Yoshinobu
2011-01-01
Document management systems have become important because of the growing popularity of electronic filing of documents and scanning of books, magazines, manuals, etc., through a scanner or a digital camera, for storage or reading on a PC or an electronic book. Text information acquired by optical character recognition (OCR) is usually added to the electronic documents for document retrieval. Since texts generated by OCR generally include character recognition errors, robust retrieval methods have been introduced to overcome this problem. In this paper, we propose a retrieval method that is robust against both character segmentation and recognition errors. In the proposed method, the insertion of noise characters and dropping of characters in the keyword retrieval enables robustness against character segmentation errors, and character substitution in the keyword of the recognition candidate for each character in OCR or any other character enables robustness against character recognition errors. The recall rate of the proposed method was 15% higher than that of the conventional method. However, the precision rate was 64% lower.
Open source OCR framework using mobile devices
NASA Astrophysics Data System (ADS)
Zhou, Steven Zhiying; Gilani, Syed Omer; Winkler, Stefan
2008-02-01
Mobile phones have evolved from passive one-to-one communication device to powerful handheld computing device. Today most new mobile phones are capable of capturing images, recording video, and browsing internet and do much more. Exciting new social applications are emerging on mobile landscape, like, business card readers, sing detectors and translators. These applications help people quickly gather the information in digital format and interpret them without the need of carrying laptops or tablet PCs. However with all these advancements we find very few open source software available for mobile phones. For instance currently there are many open source OCR engines for desktop platform but, to our knowledge, none are available on mobile platform. Keeping this in perspective we propose a complete text detection and recognition system with speech synthesis ability, using existing desktop technology. In this work we developed a complete OCR framework with subsystems from open source desktop community. This includes a popular open source OCR engine named Tesseract for text detection & recognition and Flite speech synthesis module, for adding text-to-speech ability.
NASA Astrophysics Data System (ADS)
Hassibi, Khosrow M.
1994-02-01
This paper presents a brief overview of our research in the development of an OCR system for recognition of machine-printed texts in languages that use the Arabic alphabet. The cursive nature of machine-printed Arabic makes the segmentation of words into letters a challenging problem. In our approach, through a novel preliminary segmentation technique, a word is broken into pieces where each piece may not represent a valid letter in general. Neural networks trained on a training sample set of about 500 Arabic text images are used for recognition of these pieces. The rules governing the alphabet and character-level contextual information are used for recombining these pieces into valid letters. Higher-level contextual analysis schemes including the use of an Arabic lexicon and n-grams is also under development and are expected to improve the word recognition accuracy. The segmentation, recognition, and contextual analysis processes are closely integrated using a feedback scheme. The details of preparation of the training set and some recent results on training of the networks will be presented.
Efficient automatic OCR word validation using word partial format derivation and language model
NASA Astrophysics Data System (ADS)
Chen, Siyuan; Misra, Dharitri; Thoma, George R.
2010-01-01
In this paper we present an OCR validation module, implemented for the System for Preservation of Electronic Resources (SPER) developed at the U.S. National Library of Medicine.1 The module detects and corrects suspicious words in the OCR output of scanned textual documents through a procedure of deriving partial formats for each suspicious word, retrieving candidate words by partial-match search from lexicons, and comparing the joint probabilities of N-gram and OCR edit transformation corresponding to the candidates. The partial format derivation, based on OCR error analysis, efficiently and accurately generates candidate words from lexicons represented by ternary search trees. In our test case comprising a historic medico-legal document collection, this OCR validation module yielded the correct words with 87% accuracy and reduced the overall OCR word errors by around 60%.
NASA Astrophysics Data System (ADS)
Ben Salah, Ahmed; Ragot, Nicolas; Paquet, Thierry
2013-01-01
The French National Library (BnF*) has launched many mass digitization projects in order to give access to its collection. The indexation of digital documents on Gallica (digital library of the BnF) is done through their textual content obtained thanks to service providers that use Optical Character Recognition softwares (OCR). OCR softwares have become increasingly complex systems composed of several subsystems dedicated to the analysis and the recognition of the elements in a page. However, the reliability of these systems is always an issue at stake. Indeed, in some cases, we can find errors in OCR outputs that occur because of an accumulation of several errors at different levels in the OCR process. One of the frequent errors in OCR outputs is the missed text components. The presence of such errors may lead to severe defects in digital libraries. In this paper, we investigate the detection of missed text components to control the OCR results from the collections of the French National Library. Our verification approach uses local information inside the pages based on Radon transform descriptors and Local Binary Patterns descriptors (LBP) coupled with OCR results to control their consistency. The experimental results show that our method detects 84.15% of the missed textual components, by comparing the OCR ALTO files outputs (produced by the service providers) to the images of the document.
Measurement of ocular counterrolling /OCR/ by polarized light
NASA Technical Reports Server (NTRS)
Kenyon, R. V.; Lichtenberg, B. K.
1982-01-01
The assessment of the activation of the otolith gravitoinertial sensors in the vestibular system of the inner ear may be accomplished by observing the occular counterrolling (OCR) movements which rotate the eyes about the line of sight. A method is presented for the continuous measurement of OCR by means of polarized light, a system of polarizers, and a contact lens. A polarized hard contact lens is placed between two soft lenses before application to the eye, and the measured phase difference between the incident rotating polarized light and the reflected light from this lens provides readings uncontaminated by other eye movement modes.
Study of the Effectiveness of OCR for Decentralized Data Capture and Conversion. Final Report.
ERIC Educational Resources Information Center
Liston, David M.; And Others
The ERIC network conversion to an OCR (Optical Character Recognition) mode of data entry was studied to analyze the potential effectiveness of OCR data entry for future EPC/s (Editorial Processing Centers). Study results are also applicable to any other system involving decentralized bibliographic data capture and conversion functions. The report…
Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
Naiman, Cynthia
2006-01-01
The NASA Glenn Research Center, in partnership with the aerospace industry, other government agencies, and academia, is leading the effort to develop an advanced multidisciplinary analysis environment for aerospace propulsion systems called the Numerical Propulsion System Simulation (NPSS). NPSS is a framework for performing analysis of complex systems. The initial development of NPSS focused on the analysis and design of airbreathing aircraft engines, but the resulting NPSS framework may be applied to any system, for example: aerospace, rockets, hypersonics, power and propulsion, fuel cells, ground based power, and even human system modeling. NPSS provides increased flexibility for the user, which reduces the total development time and cost. It is currently being extended to support the NASA Aeronautics Research Mission Directorate Fundamental Aeronautics Program and the Advanced Virtual Engine Test Cell (AVETeC). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structure, and heat transfer with numerical zooming on component codes. Zooming is the coupling of analyses at various levels of detail. NPSS development includes capabilities to facilitate collaborative engineering. The NPSS will provide improved tools to develop custom components and to use capability for zooming to higher fidelity codes, coupling to multidiscipline codes, transmitting secure data, and distributing simulations across different platforms. These powerful capabilities extend NPSS from a zero-dimensional simulation tool to a multi-fidelity, multidiscipline system-level simulation tool for the full development life cycle.
Issues in automatic OCR error classification
Esakov, J.; Lopresti, D.P.; Sandberg, J.S.; Zhou, J.
1994-12-31
In this paper we present the surprising result that OCR errors are not always uniformly distributed across a page. Under certain circumstances, 30% or more of the errors incurred can be attributed to a single, avoidable phenomenon in the scanning process. This observation has important ramifications for work that explicitly or implicitly assumes a uniform error distribution. In addition, our experiments show that not just the quantity but also the nature of the errors is affected. This could have an impact on strategies used for post-process error correction. Results such as these can be obtained only by analyzing large quantities of data in a controlled way. To this end, we also describe our algorithm for classifying OCR errors. This is based on a well-known dynamic programming approach for determining string edit distance which we have extended to handle the types of character segmentation errors inherent to OCR.
Pattern matching techniques for correcting low-confidence OCR words in a known context
NASA Astrophysics Data System (ADS)
Ford, Glenn; Hauser, Susan E.; Le, Daniel X.; Thoma, George R.
2000-12-01
A commercial OCR system is a key component of a system developed at the National Library of Medicine for the automated extraction of bibliographic fields from biomedical journals. This 5-engine OCR system, while exhibiting high performance overall, does not reliably convert very small characters, especially those that are in italics. As a result, the 'affiliations' field that typically contains such characters in most journals, is not captured accurately, and requires a disproportionately high manual input. To correct this problem, dictionaries have been created from words occurring in this field (e.g., university, department, street addresses, names of cities, etc.) from 230,000 articles already processed. The OCR output corresponding to the affiliation field is then matched against these dictionary entries by approximate string-matching techniques, and the ranked matches are presented to operators for verification. This paper outlines the techniques employed and the results of a comparative evaluation.
Generalization of Hindi OCR Using Adaptive Segmentation and Font Files
NASA Astrophysics Data System (ADS)
Agrawal, Mudit; Ma, Huanfeng; Doermann, David
In this chapter, we describe an adaptive Indic OCR system implemented as part of a rapidly retargetable language tool effort and extend work found in [20, 2]. The system includes script identification, character segmentation, training sample creation, and character recognition. For script identification, Hindi words are identified in bilingual or multilingual document images using features of the Devanagari script and support vector machine (SVM). Identified words are then segmented into individual characters, using a font-model-based intelligent character segmentation and recognition system. Using characteristics of structurally similar TrueType fonts, our system automatically builds a model to be used for the segmentation and recognition of the new script, independent of glyph composition. The key is a reliance on known font attributes. In our recognition system three feature extraction methods are used to demonstrate the importance of appropriate features for classification. The methods are tested on both Latin and non-Latin scripts. Results show that the character-level recognition accuracy exceeds 92% for non-Latin and 96% for Latin text on degraded documents. This work is a step toward the recognition of scripts of low-density languages which typically do not warrant the development of commercial OCR, yet often have complete TrueType font descriptions.
The Bible, truth, and multilingual OCR evaluation
NASA Astrophysics Data System (ADS)
Kanungo, Tapas; Resnik, Philip
1999-01-01
In this paper we propose to use the Bible as a dataset for comparing OCR accuracy across languages. Besides being available in a wide range of languages, Bible translations are closely parallel in content, carefully translated, surprisingly relevant with respect to modern-day language, and quite inexpensive. A project at University of Maryland is currently implementing this idea. We have created a scanned image dataset with groundtruth from an Arabic Bible. We have also used image degradation models to create synthetically degraded images of a French Bible. We hope to generate similar Bible datasets for other languages, and we are exploring alternative corpora with similar properties such the Koran and the Bhagavad Gita. Quantitative OCR evaluation based on the Arabic Bible dataset is currently in progress.
Towards Mobile OCR: How To Take a Good Picture of a Document Without Sight
Cutter, Michael; Manduchi, Roberto
2015-01-01
The advent of mobile OCR (optical character recognition) applications on regular smartphones holds great promise for enabling blind people to access printed information. Unfortunately, these systems suffer from a problem: in order for OCR output to be meaningful, a well-framed image of the document needs to be taken, something that is difficult to do without sight. This contribution presents an experimental investigation of how blind people position and orient a camera phone while acquiring document images. We developed experimental software to investigate if verbal guidance aids in the acquisition of OCR-readable images without sight. We report on our participant's feedback and performance before and after assistance from our software. PMID:26677461
Numerical Propulsion System Simulation Architecture
NASA Technical Reports Server (NTRS)
Naiman, Cynthia G.
2004-01-01
The Numerical Propulsion System Simulation (NPSS) is a framework for performing analysis of complex systems. Because the NPSS was developed using the object-oriented paradigm, the resulting architecture is an extensible and flexible framework that is currently being used by a diverse set of participants in government, academia, and the aerospace industry. NPSS is being used by over 15 different institutions to support rockets, hypersonics, power and propulsion, fuel cells, ground based power, and aerospace. Full system-level simulations as well as subsystems may be modeled using NPSS. The NPSS architecture enables the coupling of analyses at various levels of detail, which is called numerical zooming. The middleware used to enable zooming and distributed simulations is the Common Object Request Broker Architecture (CORBA). The NPSS Developer's Kit offers tools for the developer to generate CORBA-based components and wrap codes. The Developer's Kit enables distributed multi-fidelity and multi-discipline simulations, preserves proprietary and legacy codes, and facilitates addition of customized codes. The platforms supported are PC, Linux, HP, Sun, and SGI.
Validation of simulated OCR data sets
Nagy, G.
1994-12-31
Recent interest in synthetic data sets for improving classifier performance raises the question whether pseudo-random defect models provide a good approximation to live data from an OCR perspective. A proposal is presented to evaluate artificial data sets by comparing the confusion matrices genuerated on scanned and synthesized data by a given classifier. The proposed measure applies, in principle, to both isolated character recognition and to printed text. It is argued that the proposed method is more practical than direct comparison of synthetic data with real data.
Relativistic positioning systems: Numerical simulations
NASA Astrophysics Data System (ADS)
Puchades Colmenero, Neus
The position of users located on the Earth's surface or near it may be found with the classic positioning systems (CPS). Certain information broadcast by satellites of global navigation systems, as GPS and GALILEO, may be used for positioning. The CPS are based on the Newtonian formalism, although relativistic post-Newtonian corrections are done when they are necessary. This thesis contributes to the development of a different positioning approach, which is fully relativistic from the beginning. In the relativistic positioning systems (RPS), the space-time position of any user (ship, spacecraft, and so on) can be calculated with the help of four satellites, which broadcast their proper times by means of codified electromagnetic signals. In this thesis, we have simulated satellite 4-tuples of the GPS and GALILEO constellations. If a user receives the signals from four satellites simultaneously, the emission proper times read -after decoding- are the user "emission coordinates". In order to find the user "positioning coordinates", in an appropriate almost inertial reference system, there are two possibilities: (a) the explicit relation between positioning and emission coordinates (broadcast by the satellites) is analytically found or (b) numerical codes are designed to calculate the positioning coordinates from the emission ones. Method (a) is only viable in simple ideal cases, whereas (b) allows us to consider realistic situations. In this thesis, we have designed numerical codes with the essential aim of studying two appropriate RPS, which may be generalized. Sometimes, there are two real users placed in different positions, which receive the same proper times from the same satellites; then, we say that there is bifurcation, and additional data are needed to choose the real user position. In this thesis, bifurcation is studied in detail. We have analyzed in depth two RPS models; in both, it is considered that the satellites move in the Schwarzschild's space
Study of style effects on OCR errors in the MEDLINE database
NASA Astrophysics Data System (ADS)
Garrison, Penny; Davis, Diane L.; Andersen, Tim L.; Barney Smith, Elisa H.
2005-01-01
The National Library of Medicine has developed a system for the automatic extraction of data from scanned journal articles to populate the MEDLINE database. Although the 5-engine OCR system used in this process exhibits good performance overall, it does make errors in character recognition that must be corrected in order for the process to achieve the requisite accuracy. The correction process works by feeding words that have characters with less than 100% confidence (as determined automatically by the OCR engine) to a human operator who then must manually verify the word or correct the error. The majority of these errors are contained in the affiliation information zone where the characters are in italics or small fonts. Therefore only affiliation information data is used in this research. This paper examines the correlation between OCR errors and various character attributes in the MEDLINE database, such as font size, italics, bold, etc. and OCR confidence levels. The motivation for this research is that if a correlation between the character style and types of errors exists it should be possible to use this information to improve operator productivity by increasing the probability that the correct word option is presented to the human editor. We have determined that this correlation exists, in particular for the case of characters with diacritics.
Study of style effects on OCR errors in the MEDLINE database
NASA Astrophysics Data System (ADS)
Garrison, Penny; Davis, Diane L.; Andersen, Tim L.; Barney Smith, Elisa H.
2004-12-01
The National Library of Medicine has developed a system for the automatic extraction of data from scanned journal articles to populate the MEDLINE database. Although the 5-engine OCR system used in this process exhibits good performance overall, it does make errors in character recognition that must be corrected in order for the process to achieve the requisite accuracy. The correction process works by feeding words that have characters with less than 100% confidence (as determined automatically by the OCR engine) to a human operator who then must manually verify the word or correct the error. The majority of these errors are contained in the affiliation information zone where the characters are in italics or small fonts. Therefore only affiliation information data is used in this research. This paper examines the correlation between OCR errors and various character attributes in the MEDLINE database, such as font size, italics, bold, etc. and OCR confidence levels. The motivation for this research is that if a correlation between the character style and types of errors exists it should be possible to use this information to improve operator productivity by increasing the probability that the correct word option is presented to the human editor. We have determined that this correlation exists, in particular for the case of characters with diacritics.
A Functional Nuclear Localization Sequence in the C. elegans TRPV Channel OCR-2
Ezak, Meredith J.; Ferkey, Denise M.
2011-01-01
The ability to modulate gene expression in response to sensory experience is critical to the normal development and function of the nervous system. Calcium is a key activator of the signal transduction cascades that mediate the process of translating a cellular stimulus into transcriptional changes. With the recent discovery that the mammalian Cav1.2 calcium channel can be cleaved, enter the nucleus and act as a transcription factor to control neuronal gene expression, a more direct role for the calcium channels themselves in regulating transcription has begun to be appreciated. Here we report the identification of a nuclear localization sequence (NLS) in the C. elegans transient receptor potential vanilloid (TRPV) cation channel OCR-2. TRPV channels have previously been implicated in transcriptional regulation of neuronal genes in the nematode, although the precise mechanism remains unclear. We show that the NLS in OCR-2 is functional, being able to direct nuclear accumulation of a synthetic cargo protein as well as the carboxy-terminal cytosolic tail of OCR-2 where it is endogenously found. Furthermore, we discovered that a carboxy-terminal portion of the full-length channel can localize to the nucleus of neuronal cells. These results suggest that the OCR-2 TRPV cation channel may have a direct nuclear function in neuronal cells that was not previously appreciated. PMID:21957475
DRR research beyond commercial off-the-shelf OCR software: a survey
NASA Astrophysics Data System (ADS)
Lin, Xiaofan
2005-01-01
After decades of research, Optical Character Recognition (OCR) has entered into a relatively mature stage. Commercial off-the-shelf (COTS) OCR software packages have become powerful tools in Document Recognition and Retrieval (DRR) applications. One question naturally arises: What areas are left for new DRR research beyond COTS OCR software? There are many discussions around it in recent conferences. This paper attempts to address this question through a systematic survey of recently reported DRR projects as well as our own Digital Content Re-Mastering (DCRM) research at HP Labs. This survey has shown that custom DRR research is still in great need for better accuracy and reliability, complementary contents, or downstream information retrieval. Several concrete observations are also made on the basis of this survey: First, the basic character/word recognition is mostly taken on by COTS software, with a few exceptions. Second, system-level research with regard to reliability and guaranteed accuracy can seldom be replaced by COTS software. Third, document-level structure understanding still has much room to expand. Fourth, post-OCR information retrieval also has many challenging research topics.
DRR research beyond commercial off-the-shelf OCR software: a survey
NASA Astrophysics Data System (ADS)
Lin, Xiaofan
2004-12-01
After decades of research, Optical Character Recognition (OCR) has entered into a relatively mature stage. Commercial off-the-shelf (COTS) OCR software packages have become powerful tools in Document Recognition and Retrieval (DRR) applications. One question naturally arises: What areas are left for new DRR research beyond COTS OCR software? There are many discussions around it in recent conferences. This paper attempts to address this question through a systematic survey of recently reported DRR projects as well as our own Digital Content Re-Mastering (DCRM) research at HP Labs. This survey has shown that custom DRR research is still in great need for better accuracy and reliability, complementary contents, or downstream information retrieval. Several concrete observations are also made on the basis of this survey: First, the basic character/word recognition is mostly taken on by COTS software, with a few exceptions. Second, system-level research with regard to reliability and guaranteed accuracy can seldom be replaced by COTS software. Third, document-level structure understanding still has much room to expand. Fourth, post-OCR information retrieval also has many challenging research topics.
Interagency mechanical operations group numerical systems group
1997-09-01
This report consists of the minutes of the May 20-21, 1971 meeting of the Interagency Mechanical Operations Group (IMOG) Numerical Systems Group. This group looks at issues related to numerical control in the machining industry. Items discussed related to the use of CAD and CAM, EIA standards, data links, and numerical control.
Elliptic systems and numerical transformations
NASA Technical Reports Server (NTRS)
Mastin, C. W.; Thompson, J. F.
1976-01-01
Properties of a transformation method, which was developed for solving fluid dynamic problems on general two dimensional regions, are discussed. These include construction error of the transformation and applications to mesh generation. An error and stability analysis for the numerical solution of a model parabolic problem is also presented.
A super resolution framework for low resolution document image OCR
NASA Astrophysics Data System (ADS)
Ma, Di; Agam, Gady
2013-01-01
Optical character recognition is widely used for converting document images into digital media. Existing OCR algorithms and tools produce good results from high resolution, good quality, document images. In this paper, we propose a machine learning based super resolution framework for low resolution document image OCR. Two main techniques are used in our proposed approach: a document page segmentation algorithm and a modified K-means clustering algorithm. Using this approach, by exploiting coherence in the document, we reconstruct from a low resolution document image a better resolution image and improve OCR results. Experimental results show substantial gain in low resolution documents such as the ones captured from video.
Numerical methods for multibody systems
NASA Technical Reports Server (NTRS)
Glowinski, Roland; Nasser, Mahmoud G.
1994-01-01
This article gives a brief summary of some results obtained by Nasser on modeling and simulation of inequality problems in multibody dynamics. In particular, the augmented Lagrangian method discussed here is applied to a constrained motion problem with impulsive inequality constraints. A fundamental characteristic of the multibody dynamics problem is the lack of global convexity of its Lagrangian. The problem is transformed into a convex analysis problem by localization (piecewise linearization), where the augmented Lagrangian has been successfully used. A model test problem is considered and a set of numerical experiments is presented.
Efficient Language-Independent Retrieval of Printed Documents without OCR
NASA Astrophysics Data System (ADS)
Magdy, Walid; Darwish, Kareem; El-Saban, Motaz
Recent book digitization initiatives have facilitated the access and search of millions of books. Although OCR remains essential for retrieving printed documents, OCR engines remain limited in the languages they handle and are generally expensive to build. This paper proposes a language independent approach that enables search through printed documents in a way that combines image-based matching with conventional IR techniques without using OCR. While image-based matching can be effective in finding similar words, complementing it with efficient retrieval techniques allows for sub-word matching, term weighting, and document ranking. The basic idea is that similar connected elements in printed documents are clustered and represented with ID’s, which are then used to generate equivalent textual representations. The resultant representations are indexed using an IR engine and searched using the equivalent ID’s of the connected elements in queries. Though, the main benefit of the proposed approach lies in languages for which no OCR exists, the technique was tested on English and Arabic to ascertain the relative effectiveness of the approach. The approach achieves more than 61% relative effectiveness compared to using OCR for both languages. While the reported numbers are lower than that of OCR-based approaches, the proposed method is fully automated, does not require any supervised training, and allows documents to be searchable within a few hours.
A segmentation-free approach to Arabic and Urdu OCR
NASA Astrophysics Data System (ADS)
Sabbour, Nazly; Shafait, Faisal
2013-01-01
In this paper, we present a generic Optical Character Recognition system for Arabic script languages called Nabocr. Nabocr uses OCR approaches specific for Arabic script recognition. Performing recognition on Arabic script text is relatively more difficult than Latin text due to the nature of Arabic script, which is cursive and context sensitive. Moreover, Arabic script has different writing styles that vary in complexity. Nabocr is initially trained to recognize both Urdu Nastaleeq and Arabic Naskh fonts. However, it can be trained by users to be used for other Arabic script languages. We have evaluated our system's performance for both Urdu and Arabic. In order to evaluate Urdu recognition, we have generated a dataset of Urdu text called UPTI (Urdu Printed Text Image Database), which measures different aspects of a recognition system. The performance of our system for Urdu clean text is 91%. For Arabic clean text, the performance is 86%. Moreover, we have compared the performance of our system against Tesseract's newly released Arabic recognition, and the performance of both systems on clean images is almost the same.
Combining multiple thresholding binarization values to improve OCR output
NASA Astrophysics Data System (ADS)
Lund, William B.; Kennard, Douglas J.; Ringger, Eric K.
2013-01-01
For noisy, historical documents, a high optical character recognition (OCR) word error rate (WER) can render the OCR text unusable. Since image binarization is often the method used to identify foreground pixels, a body of research seeks to improve image-wide binarization directly. Instead of relying on any one imperfect binarization technique, our method incorporates information from multiple simple thresholding binarizations of the same image to improve text output. Using a new corpus of 19th century newspaper grayscale images for which the text transcription is known, we observe WERs of 13.8% and higher using current binarization techniques and a state-of-the-art OCR engine. Our novel approach combines the OCR outputs from multiple thresholded images by aligning the text output and producing a lattice of word alternatives from which a lattice word error rate (LWER) is calculated. Our results show a LWER of 7.6% when aligning two threshold images and a LWER of 6.8% when aligning five. From the word lattice we commit to one hypothesis by applying the methods of Lund et al. (2011) achieving an improvement over the original OCR output and a 8.41% WER result on this data set.
Evaluating supervised topic models in the presence of OCR errors
NASA Astrophysics Data System (ADS)
Walker, Daniel; Ringger, Eric; Seppi, Kevin
2013-01-01
Supervised topic models are promising tools for text analytics that simultaneously model topical patterns in document collections and relationships between those topics and document metadata, such as timestamps. We examine empirically the effect of OCR noise on the ability of supervised topic models to produce high quality output through a series of experiments in which we evaluate three supervised topic models and a naive baseline on synthetic OCR data having various levels of degradation and on real OCR data from two different decades. The evaluation includes experiments with and without feature selection. Our results suggest that supervised topic models are no better, or at least not much better in terms of their robustness to OCR errors, than unsupervised topic models and that feature selection has the mixed result of improving topic quality while harming metadata prediction quality. For users of topic modeling methods on OCR data, supervised topic models do not yet solve the problem of finding better topics than the original unsupervised topic models.
Numerical propulsion system simulation - An interdisciplinary approach
NASA Technical Reports Server (NTRS)
Nichols, Lester D.; Chamis, Christos C.
1991-01-01
The tremendous progress being made in computational engineering and the rapid growth in computing power that is resulting from parallel processing now make it feasible to consider the use of computer simulations to gain insights into the complex interactions in aerospace propulsion systems and to evaluate new concepts early in the design process before a commitment to hardware is made. Described here is a NASA initiative to develop a Numerical Propulsion System Simulation (NPSS) capability.
Numerical propulsion system simulation: An interdisciplinary approach
NASA Technical Reports Server (NTRS)
Nichols, Lester D.; Chamis, Christos C.
1991-01-01
The tremendous progress being made in computational engineering and the rapid growth in computing power that is resulting from parallel processing now make it feasible to consider the use of computer simulations to gain insights into the complex interactions in aerospace propulsion systems and to evaluate new concepts early in the design process before a commitment to hardware is made. Described here is a NASA initiative to develop a Numerical Propulsion System Simulation (NPSS) capability.
Numerical modeling of nonintrusive inspection systems
Hall, J.; Morgan, J.; Sale, K.
1992-12-01
A wide variety of nonintrusive inspection systems have been proposed in the past several years for the detection of hidden contraband in airline luggage and shipping containers. The majority of these proposed techniques depend on the interaction of radiation with matter to produce a signature specific to the contraband of interest, whether drugs or explosives. In the authors` role as diagnostic specialists in the Underground Test Program over the past forty years, L-Division of the Lawrence Livermore National Laboratory has developed a technique expertise in the combined numerical and experimental modeling of these types of system. Based on their experience, they are convinced that detailed numerical modeling provides a much more accurate estimate of the actual performance of complex experiments than simple analytical modeling. Furthermore, the construction of detailed numerical prototypes allows experimenters to explore the entire region of parameter space available to them before committing their ideas to hardware. This sort of systematic analysis has often led to improved experimental designs and reductions in fielding costs. L-Division has developed an extensive suite of computer codes to model proposed experiments and possible background interactions. These codes allow one to simulate complex radiation sources, model 3-dimensional system geometries with {open_quotes}real world{close_quotes} complexity, specify detailed elemental distributions, and predict the response of almost any type of detector. In this work several examples are presented illustrating the use of these codes in modeling experimental systems at LLNL and their potential usefulness in evaluating nonintrusive inspection systems is discussed.
OCR enhancement through neighbor embedding and fast approximate nearest neighbors
NASA Astrophysics Data System (ADS)
Smith, D. C.
2012-10-01
Generic optical character recognition (OCR) engines often perform very poorly in transcribing scanned low resolution (LR) text documents. To improve OCR performance, we apply the Neighbor Embedding (NE) single-image super-resolution (SISR) technique to LR scanned text documents to obtain high resolution (HR) versions, which we subsequently process with OCR. For comparison, we repeat this procedure using bicubic interpolation (BI). We demonstrate that mean-square errors (MSE) in NE HR estimates do not increase substantially when NE is trained in one Latin font style and tested in another, provided both styles belong to the same font category (serif or sans serif). This is very important in practice, since for each font size, the number of training sets required for each category may be reduced from dozens to just one. We also incorporate randomized k-d trees into our NE implementation to perform approximate nearest neighbor search, and obtain a 1000x speed up of our original NE implementation, with negligible MSE degradation. This acceleration also made it practical to combine all of our size-specific NE Latin models into a single Universal Latin Model (ULM). The ULM eliminates the need to determine the unknown font category and size of an input LR text document and match it to an appropriate model, a very challenging task, since the dpi (pixels per inch) of the input LR image is generally unknown. Our experiments show that OCR character error rates (CER) were over 90% when we applied the Tesseract OCR engine to LR text documents (scanned at 75 dpi and 100 dpi) in the 6-10 pt range. By contrast, using k-d trees and the ULM, CER after NE preprocessing averaged less than 7% at 3x (100 dpi LR scanning) and 4x (75 dpi LR scanning) magnification, over an order of magnitude improvement. Moreover, CER after NE preprocessing was more that 6 times lower on average than after BI preprocessing.
Systems Improved Numerical Fluids Analysis Code
NASA Technical Reports Server (NTRS)
Costello, F. A.
1990-01-01
Systems Improved Numerical Fluids Analysis Code, SINFAC, consists of additional routines added to April, 1983, version of SINDA. Additional routines provide for mathematical modeling of active heat-transfer loops. Simulates steady-state and pseudo-transient operations of 16 different components of heat-transfer loops, including radiators, evaporators, condensers, mechanical pumps, reservoirs, and many types of valves and fittings. Program contains property-analysis routine used to compute thermodynamic properties of 20 different refrigerants. Source code written in FORTRAN 77.
Numerical simulation of magmatic hydrothermal systems
Ingebritsen, S.E.; Geiger, S.; Hurwitz, S.; Driesner, T.
2010-01-01
The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have seen steady growth of computational power and the development of numerical models that have eliminated or minimized the need for various simplifying assumptions. Considerable heuristic insight has been gained from process-oriented numerical modeling. Recent modeling efforts employing relatively complete EOS and accurate transport calculations have revealed dynamic behavior that was damped by linearized, less accurate models, including fluid property control of hydrothermal plume temperatures and three-dimensional geometries. Other recent modeling results have further elucidated the controlling role of permeability structure and revealed the potential for significant hydrothermally driven deformation. Key areas for future reSearch include incorporation of accurate EOS for the complete H2O-NaCl-CO2 system, more realistic treatment of material heterogeneity in space and time, realistic description of large-scale relative permeability behavior, and intercode benchmarking comparisons. Copyright 2010 by the American Geophysical Union.
Research on ARM Numerical Control System
NASA Astrophysics Data System (ADS)
Wei, Xu; JiHong, Chen
Computerized Numerical Control (CNC) machine tools is the foundation of modern manufacturing systems, whose advanced digital technology is the key to solve the problem of sustainable development of machine tool manufacturing industry. The paper is to design CNC system embedded on ARM and indicates the hardware design and the software systems supported. On the hardware side: the driving chip of the motor control unit, as the core of components, is MCX314AL of DSP motion control which is developed by NOVA Electronics Co., Ltd. of Japan. It make convenient to control machine because of its excellent performance, simple interface, easy programming. On the Software side, the uC/OS-2 is selected as the embedded operating system of the open source, which makes a detailed breakdown of the modules of the CNC system. Those priorities are designed according to their actual requirements. The ways of communication between the module and the interrupt response are so different that it guarantees real-time property and reliability of the numerical control system. Therefore, it not only meets the requirements of the current social precision machining, but has good man-machine interface and network support to facilitate a variety of craftsmen use.
Numerical data frame readout system used in testing telemetry systems
NASA Technical Reports Server (NTRS)
Cote, C. E.; Cressey, J. R.
1967-01-01
Digital telemetry systems are treated by a display system that offers direct readout as high data rates. The rates appear in numerical format and are adaptable to photographic recording techniques. The system can show bit dropouts at a memory output or locate a malfunction in a system.
2001 Numerical Propulsion System Simulation Review
NASA Technical Reports Server (NTRS)
Lytle, John; Follen, Gregory; Naiman, Cynthia; Veres, Joseph; Owen, Karl; Lopez, Isaac
2002-01-01
The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective, high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. Major accomplishments include the first formal release of the NPSS object-oriented architecture (NPSS Version 1) and the demonstration of a one order of magnitude reduction in computing cost-to-performance ratio using a cluster of personal computers. The paper also describes the future NPSS milestones, which include the simulation of space transportation propulsion systems in response to increased emphasis on safe, low cost access to space within NASA's Aerospace Technology Enterprise. In addition, the paper contains a summary of the feedback received from industry partners on the fiscal year 2000 effort and the actions taken over the past year to
2000 Numerical Propulsion System Simulation Review
NASA Technical Reports Server (NTRS)
Lytle, John; Follen, Greg; Naiman, Cynthia; Veres, Joseph; Owen, Karl; Lopez, Isaac
2001-01-01
The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia, and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective. high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. Major accomplishments include the first formal release of the NPSS object-oriented architecture (NPSS Version 1) and the demonstration of a one order of magnitude reduction in computing cost-to-performance ratio using a cluster of personal computers. The paper also describes the future NPSS milestones, which include the simulation of space transportation propulsion systems in response to increased emphasis on safe, low cost access to space within NASA'S Aerospace Technology Enterprise. In addition, the paper contains a summary of the feedback received from industry partners on the fiscal year 1999 effort and the actions taken over the past year to
Numeral-Incorporating Roots in Numeral Systems: A Comparative Analysis of Two Sign Languages
ERIC Educational Resources Information Center
Fuentes, Mariana; Massone, Maria Ignacia; Fernandez-Viader, Maria del Pilar; Makotrinsky, Alejandro; Pulgarin, Francisca
2010-01-01
Numeral-incorporating roots in the numeral systems of Argentine Sign Language (LSA) and Catalan Sign Language (LSC), as well as the main features of the number systems of both languages, are described and compared. Informants discussed the use of numerals and roots in both languages (in most cases in natural contexts). Ten informants took part in…
The Numerical Propulsion System Simulation: An Overview
NASA Technical Reports Server (NTRS)
Lytle, John K.
2000-01-01
Advances in computational technology and in physics-based modeling are making large-scale, detailed simulations of complex systems possible within the design environment. For example, the integration of computing, communications, and aerodynamics has reduced the time required to analyze major propulsion system components from days and weeks to minutes and hours. This breakthrough has enabled the detailed simulation of major propulsion system components to become a routine part of designing systems, providing the designer with critical information about the components early in the design process. This paper describes the development of the numerical propulsion system simulation (NPSS), a modular and extensible framework for the integration of multicomponent and multidisciplinary analysis tools using geographically distributed resources such as computing platforms, data bases, and people. The analysis is currently focused on large-scale modeling of complete aircraft engines. This will provide the product developer with a "virtual wind tunnel" that will reduce the number of hardware builds and tests required during the development of advanced aerospace propulsion systems.
Numerically simulating the sandwich plate system structures
NASA Astrophysics Data System (ADS)
Feng, Guo-Qing; Li, Gang; Liu, Zhi-Hui; Niu, Huai-Lei; Li, Chen-Feng
2010-09-01
Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering. At present, according to the rules of classification societies, a mixture of shell and solid elements are required to simulate an SPS. Based on the principle of stiffness decomposition, a new numerical simulation method for shell elements was proposed. In accordance with the principle of stiffness decomposition, the total stiffness can be decomposed into the bending stiffness and shear stiffness. Displacement and stress response related to bending stiffness was calculated with the laminated shell element. Displacement and stress response due to shear was calculated by use of a computational code write by FORTRAN language. Then the total displacement and stress response for the SPS was obtained by adding together these two parts of total displacement and stress. Finally, a rectangular SPS plate and a double-bottom structure were used for a simulation. The results show that the deflection simulated by the elements proposed in the paper is larger than the same simulated by solid elements and the analytical solution according to Hoff theory and approximate to the same simulated by the mixture of shell-solid elements, and the stress simulated by the elements proposed in the paper is approximate to the other simulating methods. So compared with calculations based on a mixture of shell and solid elements, the numerical simulation method given in the paper is more efficient and easier to do.
A unified approach for development of Urdu Corpus for OCR and demographic purpose
NASA Astrophysics Data System (ADS)
Choudhary, Prakash; Nain, Neeta; Ahmed, Mushtaq
2015-02-01
This paper presents a methodology for the development of an Urdu handwritten text image Corpus and application of Corpus linguistics in the field of OCR and information retrieval from handwritten document. Compared to other language scripts, Urdu script is little bit complicated for data entry. To enter a single character it requires a combination of multiple keys entry. Here, a mixed approach is proposed and demonstrated for building Urdu Corpus for OCR and Demographic data collection. Demographic part of database could be used to train a system to fetch the data automatically, which will be helpful to simplify existing manual data-processing task involved in the field of data collection such as input forms like Passport, Ration Card, Voting Card, AADHAR, Driving licence, Indian Railway Reservation, Census data etc. This would increase the participation of Urdu language community in understanding and taking benefit of the Government schemes. To make availability and applicability of database in a vast area of corpus linguistics, we propose a methodology for data collection, mark-up, digital transcription, and XML metadata information for benchmarking.
Zavil'gel'skiĭ, G B; Rastorguev, S M
2009-01-01
Genes encoding antirestriction proteins (antirestrictases, inasmuch as the antirestriction proteins inhibit the activity of restriction-modification systems, but have no proper enzyme activity, the name antirestrictase is only tentative) are included in the composition of conjugative plasmids (genes ardABC) and some bacteriophages (genes ocr and darA). Antirestriction proteins inhibit of the type I restriction-modification enzymes and thus protect unmodified DNA of plasmids and bacteriophages from degradation. Antirestriction proteins belong to the "protein mimicry of DNA" family: the spatial structure is like the B-form of DNA, and therefore the antirestriction proteins operated on the principle of concurrent inhibition replacing DNA in the complex with the restriction-modification enzyme. Based on the prepared in vitro mutant forms of ArdA and Ocr, and also on natural proteins ArdA selectively inhibiting restriction activity of the type I enzymes, but not affecting their methylase activity, we have developed a model of complex formation between the antirestriction proteins and the restriction-modification enzymes R2M2S. Antirestriction proteins are capable of competing displacement of the DNA strand from two sites which are situated as follows: 1) in S-subunit (enzyme contact with the specific DNA site) and 2) in R-subunit (through this unit translocation of the DNA strand occurs followed by its degradation). Analysis of estriction and antimodification activities of proteins ArdA and Ocr depending on the expression level of genes ardA and ocr was performed (the cloning of the genes was done under strictly regulated promoter). PMID:19425495
Papas, Klearchos K.; Bellin, Melena D.; Sutherland, David E. R.; Suszynski, Thomas M.; Kitzmann, Jennifer P.; Avgoustiniatos, Efstathios S.; Gruessner, Angelika C.; Mueller, Kathryn R.; Beilman, Gregory J.; Balamurugan, Appakalai N.; Loganathan, Gopalakrishnan; Colton, Clark K.; Koulmanda, Maria; Weir, Gordon C.; Wilhelm, Josh J.; Qian, Dajun; Niland, Joyce C.; Hering, Bernhard J.
2015-01-01
Background Reliable in vitro islet quality assessment assays that can be performed routinely, prospectively, and are able to predict clinical transplant outcomes are needed. In this paper we present data on the utility of an assay based on cellular oxygen consumption rate (OCR) in predicting clinical islet autotransplant (IAT) insulin independence (II). IAT is an attractive model for evaluating characterization assays regarding their utility in predicting II due to an absence of confounding factors such as immune rejection and immunosuppressant toxicity. Methods Membrane integrity staining (FDA/PI), OCR normalized to DNA (OCR/DNA), islet equivalent (IE) and OCR (viable IE) normalized to recipient body weight (IE dose and OCR dose), and OCR/DNA normalized to islet size index (ISI) were used to characterize autoislet preparations (n = 35). Correlation between pre-IAT islet product characteristics and II was determined using receiver operating characteristic analysis. Results Preparations that resulted in II had significantly higher OCR dose and IE dose (p<0.001). These islet characterization methods were highly correlated with II at 6–12 months post-IAT (area-under-the-curve (AUC) = 0.94 for IE dose and 0.96 for OCR dose). FDA/PI (AUC = 0.49) and OCR/DNA (AUC = 0.58) did not correlate with II. OCR/DNA/ISI may have some utility in predicting outcome (AUC = 0.72). Conclusions Commonly used assays to determine whether a clinical islet preparation is of high quality prior to transplantation are greatly lacking in sensitivity and specificity. While IE dose is highly predictive, it does not take into account islet cell quality. OCR dose, which takes into consideration both islet cell quality and quantity, may enable a more accurate and prospective evaluation of clinical islet preparations. PMID:26258815
SINFAC - SYSTEMS IMPROVED NUMERICAL FLUIDS ANALYSIS CODE
NASA Technical Reports Server (NTRS)
Costello, F. A.
1994-01-01
The Systems Improved Numerical Fluids Analysis Code, SINFAC, consists of additional routines added to the April 1983 revision of SINDA, a general thermal analyzer program. The purpose of the additional routines is to allow for the modeling of active heat transfer loops. The modeler can simulate the steady-state and pseudo-transient operations of 16 different heat transfer loop components including radiators, evaporators, condensers, mechanical pumps, reservoirs and many types of valves and fittings. In addition, the program contains a property analysis routine that can be used to compute the thermodynamic properties of 20 different refrigerants. SINFAC can simulate the response to transient boundary conditions. SINFAC was first developed as a method for computing the steady-state performance of two phase systems. It was then modified using CNFRWD, SINDA's explicit time-integration scheme, to accommodate transient thermal models. However, SINFAC cannot simulate pressure drops due to time-dependent fluid acceleration, transient boil-out, or transient fill-up, except in the accumulator. SINFAC also requires the user to be familiar with SINDA. The solution procedure used by SINFAC is similar to that which an engineer would use to solve a system manually. The solution to a system requires the determination of all of the outlet conditions of each component such as the flow rate, pressure, and enthalpy. To obtain these values, the user first estimates the inlet conditions to the first component of the system, then computes the outlet conditions from the data supplied by the manufacturer of the first component. The user then estimates the temperature at the outlet of the third component and computes the corresponding flow resistance of the second component. With the flow resistance of the second component, the user computes the conditions down stream, namely the inlet conditions of the third. The computations follow for the rest of the system, back to the first component
History of the Tesseract OCR engine: what worked and what didn't
NASA Astrophysics Data System (ADS)
Smith, Ray W.
2013-01-01
This paper describes the development history of the Tesseract OCR engine, and compares the methods to general changes in the field over a similar time period. Emphasis is placed on the lessons learned with the goal of providing a primer for those interested in OCR research.
Low-Budget, Cost-Effective OCR: Optical Character Recognition for MS-DOS Micros.
ERIC Educational Resources Information Center
Perez, Ernest
1990-01-01
Discusses optical character recognition (OCR) for use with MS-DOS microcomputers. Cost effectiveness is considered, three types of software approaches to character recognition are explained, hardware and operation requirements are described, possible library applications are discussed, future OCR developments are suggested, and a list of OCR…
Keeping on Keeping on: OCR and Complaints of Racial Discrimination 50 Years after "Brown"
ERIC Educational Resources Information Center
Pollock, Mica
2005-01-01
This article, written by a former civil rights investigator in the U.S. Department of Education's Office for Civil Rights (OCR), contends that ordinary Americans advocating for equal educational opportunity for students of color might enlist OCR more actively and knowingly to help secure racial equality of opportunity 50 years after "Brown." Now a…
Optical character recognition (OCR) in uncontrolled environments using optical correlators
NASA Astrophysics Data System (ADS)
Morin, Andre; Bergeron, Alain; Prevost, Donald; Radloff, Ernst A.
1999-03-01
With the emergence of a global economy, companies are more than ever pressured for improved efficiency. Int he transportation industry there is a growing need for better tracking of the status of containers in transit. This would lead to improved handling operation, reduce the number of errors, increase the throughput and enable the use of electronic data interchange (EDI). As electronic tags are not generalized in this industry, containers identification must rely on optical character recognition of the codes printed on the containers. OCR has been one of the first applications envisaged for optical correlation technologies as a result of their high-speed direct detection and identification capabilities. Until now though, most of the work in this area had been performed on computer-generated symbols. Field applications however, must cope with varying symbol fonts and sizes, colors and backgrounds, illumination levels, etc. Environmental variables such as dust, dirt and rust must also be accounted for. Together, these variables lead to a hard-to- solve problem. This paper presents INO's optical correlator and discusses the methods used to generate the identification vectors from which the OCR classification is achieved. It is shown that good results can be obtained on gray-scale real- life images when a multiple composite-filters strategy combined to an innovative classification method.
ERIC Educational Resources Information Center
Kichuk, Diana
2015-01-01
The electronic conversion of scanned image files to readable text using optical character recognition (OCR) software and the subsequent migration of raw OCR text to e-book text file formats are key remediation or media conversion technologies used in digital repository e-book production. Despite real progress, the OCR problem of reliability and…
Code of Federal Regulations, 2013 CFR
2013-01-01
... 7 Agriculture 1 2013-01-01 2013-01-01 false Other than myself, OCR, and the agency, may any other... Conducted? § 15f.19 Other than myself, OCR, and the agency, may any other interested party participate in... the complainant, OCR, and, and if it so desires, the agency. However, if there are circumstances...
Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 1 2011-01-01 2011-01-01 false Other than myself, OCR, and the agency, may any other... Conducted? § 15f.19 Other than myself, OCR, and the agency, may any other interested party participate in... the complainant, OCR, and, and if it so desires, the agency. However, if there are circumstances...
Code of Federal Regulations, 2014 CFR
2014-01-01
... 7 Agriculture 1 2014-01-01 2014-01-01 false Other than myself, OCR, and the agency, may any other... Conducted? § 15f.19 Other than myself, OCR, and the agency, may any other interested party participate in... the complainant, OCR, and, and if it so desires, the agency. However, if there are circumstances...
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 1 2010-01-01 2010-01-01 false Other than myself, OCR, and the agency, may any other... Conducted? § 15f.19 Other than myself, OCR, and the agency, may any other interested party participate in... the complainant, OCR, and, and if it so desires, the agency. However, if there are circumstances...
Code of Federal Regulations, 2012 CFR
2012-01-01
... 7 Agriculture 1 2012-01-01 2012-01-01 false Other than myself, OCR, and the agency, may any other... Conducted? § 15f.19 Other than myself, OCR, and the agency, may any other interested party participate in... the complainant, OCR, and, and if it so desires, the agency. However, if there are circumstances...
Numerical Archetypal Parameterization for Mesoscale Convective Systems
NASA Astrophysics Data System (ADS)
Yano, J. I.
2015-12-01
Vertical shear tends to organize atmospheric moist convection into multiscale coherent structures. Especially, the counter-gradient vertical transport of horizontal momentum by organized convection can enhance the wind shear and transport kinetic energy upscale. However, this process is not represented by traditional parameterizations. The present paper sets the archetypal dynamical models, originally formulated by the second author, into a parameterization context by utilizing a nonhydrostatic anelastic model with segmentally-constant approximation (NAM-SCA). Using a two-dimensional framework as a starting point, NAM-SCA spontaneously generates propagating tropical squall-lines in a sheared environment. A high numerical efficiency is achieved through a novel compression methodology. The numerically-generated archetypes produce vertical profiles of convective momentum transport that are consistent with the analytic archetype.
Utilizing web data in identification and correction of OCR errors
NASA Astrophysics Data System (ADS)
Taghva, Kazem; Agarwal, Shivam
2013-12-01
In this paper, we report on our experiments for detection and correction of OCR errors with web data. More specifically, we utilize Google search to access the big data resources available to identify possible candidates for correction. We then use a combination of the Longest Common Subsequences (LCS) and Bayesian estimates to automatically pick the proper candidate. Our experimental results on a small set of historical newspaper data show a recall and precision of 51% and 100%, respectively. The work in this paper further provides a detailed classification and analysis of all errors. In particular, we point out the shortcomings of our approach in its ability to suggest proper candidates to correct the remaining errors.
Implicit numerical integration for periodic solutions of autonomous nonlinear systems
NASA Technical Reports Server (NTRS)
Thurston, G. A.
1982-01-01
A change of variables that stabilizes numerical computations for periodic solutions of autonomous systems is derived. Computation of the period is decoupled from the rest of the problem for conservative systems of any order and for any second-order system. Numerical results are included for a second-order conservative system under a suddenly applied constant load. Near the critical load for the system, a small increment in load amplitude results in a large increase in amplitude of the response.
Operating System For Numerically Controlled Milling Machine
NASA Technical Reports Server (NTRS)
Ray, R. B.
1992-01-01
OPMILL program is operating system for Kearney and Trecker milling machine providing fast easy way to program manufacture of machine parts with IBM-compatible personal computer. Gives machinist "equation plotter" feature, which plots equations that define movements and converts equations to milling-machine-controlling program moving cutter along defined path. System includes tool-manager software handling up to 25 tools and automatically adjusts to account for each tool. Developed on IBM PS/2 computer running DOS 3.3 with 1 MB of random-access memory.
Numerical Poisson-Boltzmann Model for Continuum Membrane Systems.
Botello-Smith, Wesley M; Liu, Xingping; Cai, Qin; Li, Zhilin; Zhao, Hongkai; Luo, Ray
2013-01-01
Membrane protein systems are important computational research topics due to their roles in rational drug design. In this study, we developed a continuum membrane model utilizing a level set formulation under the numerical Poisson-Boltzmann framework within the AMBER molecular mechanics suite for applications such as protein-ligand binding affinity and docking pose predictions. Two numerical solvers were adapted for periodic systems to alleviate possible edge effects. Validation on systems ranging from organic molecules to membrane proteins up to 200 residues, demonstrated good numerical properties. This lays foundations for sophisticated models with variable dielectric treatments and second-order accurate modeling of solvation interactions. PMID:23439886
Generalized Database Management System Support for Numeric Database Environments.
ERIC Educational Resources Information Center
Dominick, Wayne D.; Weathers, Peggy G.
1982-01-01
This overview of potential for utilizing database management systems (DBMS) within numeric database environments highlights: (1) major features, functions, and characteristics of DBMS; (2) applicability to numeric database environment needs and user needs; (3) current applications of DBMS technology; and (4) research-oriented and…
NASA Astrophysics Data System (ADS)
Katsuyama, Yutaka; Takebe, Hiroaki; Kurokawa, Koji; Saitoh, Takahiro; Naoi, Satoshi
2001-12-01
We have developed a method that allows Japanese document images to be retrieved more accurately by using OCR character candidate information and a conventional plain text search engine. In this method, the document image is first recognized by normal OCR to produce text. Keyword areas are then estimated from the normal OCR produced text through morphological analysis. A lattice of candidate- character codes is extracted from these areas, and then character strings are extracted from the lattice using a word-matching method in noun areas and a K-th DP-matching method in undefined word areas. Finally, these extracted character strings are added to the normal OCR produced text to improve document retrieval accuracy when u sing a conventional plain text search engine. Experimental results from searches of 49 OHP sheet images revealed that our method has a high recall rate of 98.2%, compared to 90.3% with a conventional method using only normal OCR produced text, while requiring about the same processing time as normal OCR.
Numerical quantification of habitability in serpentinizing systems
NASA Astrophysics Data System (ADS)
Som, S.; Alperin, M. J.; Hoehler, T. M.
2012-12-01
The likely presence of liquid water in contact with olivine-bearing rocks on Mars, the detection of serpentine minerals and of methane emissions possibly consistent with serpentinization, and the observation of serpentine-associated methane-cycling communities on Earth have all led to excitement over the potential of such systems to host life on Mars, even into the present day. However, the habitability of subsurface serpentinizing systems on Mars does not necessarily follow from these qualitative observations. In particular, while the production of H2 during serpentinization could provide methanogens with a needed substrate, the alkaline conditions and corresponding potential for carbon limitation that arise in concert are negatives against which H2 supply must be balanced. We considered this balance via a coupled geochemical-bioenergetic model that weighs the outputs of serpentinization against the metabolic requirements of methanogenesis, in an energetic frame of reference. Serpentinization is modeled using the "Geochemist's Workbench" (GWB) whereby ultramafic harzburgite rocks are reacted with oxygen and sulfate depleted seawater. Reaction kinetics are not explicitly considered, but comparable effects of partial reaction are approximated by assuming post-reaction dilution of equilibrated fluids. The output of GWB serves as the input to the bioenergetic model, which calculates methanogenic energy yields based on spherically-symmetrical diffusion of substrates to a cell followed by reaction at the diffusion-limited rate. Membrane selectivity for substrate transport is explicitly considered. Results will be report updates for two scenarios: (i) High temperature serpentinization followed by cooling and transport of equilibrated fluid to a lower temperature regime accessible to biology; (ii) Serpentinization within the biologically-tolerated range of temperatures. Such coupled models demonstrate that environmental variability with respect to both water-rock reaction
How well does multiple OCR error correction generalize?
NASA Astrophysics Data System (ADS)
Lund, William B.; Ringger, Eric K.; Walker, Daniel D.
2013-12-01
As the digitization of historical documents, such as newspapers, becomes more common, the need of the archive patron for accurate digital text from those documents increases. Building on our earlier work, the contributions of this paper are: 1. in demonstrating the applicability of novel methods for correcting optical character recognition (OCR) on disparate data sets, including a new synthetic training set, 2. enhancing the correction algorithm with novel features, and 3. assessing the data requirements of the correction learning method. First, we correct errors using conditional random fields (CRF) trained on synthetic training data sets in order to demonstrate the applicability of the methodology to unrelated test sets. Second, we show the strength of lexical features from the training sets on two unrelated test sets, yielding a relative reduction in word error rate on the test sets of 6.52%. New features capture the recurrence of hypothesis tokens and yield an additional relative reduction in WER of 2.30%. Further, we show that only 2.0% of the full training corpus of over 500,000 feature cases is needed to achieve correction results comparable to those using the entire training corpus, effectively reducing both the complexity of the training process and the learned correction model.
Title extraction and generation from OCR'd documents
NASA Astrophysics Data System (ADS)
Taghva, Kazem; Condit, Allen; Lumos, Steve; Borsack, Julie; Nartker, Thomas
2007-01-01
Extraction of metadata from documents is a tedious and expensive process. In general, documents are manually reviewed for structured data such as title, author, date, organization, etc. The purpose of extraction is to build metadata for documents that can be used when formulating structured queries. In many large document repositories such as the National Library of Medicine (NLM)1 or university libraries, the extraction task is a daily process that spans decades. Although some automation is used during the extraction process, generally, metadata extraction is a manual task. Aside from the cost and labor time, manual processing is error prone and requires many levels of quality control. Recent advances in extraction technology, as reported at the Message the Understanding Conference (MUC),2 is comparable with extraction performed by humans. In addition, many organizations use historical data for lookup to improve the quality of extraction. For the large government document repository we are working with, the task involves extraction of several fields from millions of OCR'd and electronic documents. Since this project is time-sensitive, automatic extraction turns out to be the only viable solution. There are more than a dozen fields associated with each document that require extraction. In this paper, we report on the extraction and generation of the title field.
INFeRS: Interactive Numeric Files Retrieval System. Final Report.
ERIC Educational Resources Information Center
Chiang, Katherine; And Others
In 1988 Mann Library at Cornell University proposed to develop a computer system that would support interactive access to significant electronic files in agriculture and the life sciences. This system was titled the Interactive Numeric Files Retrieval System (INFeRS). This report describes how project goals were met and it presents the project's…
Quantitative analysis of numerical solvers for oscillatory biomolecular system models
Quo, Chang F; Wang, May D
2008-01-01
Background This article provides guidelines for selecting optimal numerical solvers for biomolecular system models. Because various parameters of the same system could have drastically different ranges from 10-15 to 1010, the ODEs can be stiff and ill-conditioned, resulting in non-unique, non-existing, or non-reproducible modeling solutions. Previous studies have not examined in depth how to best select numerical solvers for biomolecular system models, which makes it difficult to experimentally validate the modeling results. To address this problem, we have chosen one of the well-known stiff initial value problems with limit cycle behavior as a test-bed system model. Solving this model, we have illustrated that different answers may result from different numerical solvers. We use MATLAB numerical solvers because they are optimized and widely used by the modeling community. We have also conducted a systematic study of numerical solver performances by using qualitative and quantitative measures such as convergence, accuracy, and computational cost (i.e. in terms of function evaluation, partial derivative, LU decomposition, and "take-off" points). The results show that the modeling solutions can be drastically different using different numerical solvers. Thus, it is important to intelligently select numerical solvers when solving biomolecular system models. Results The classic Belousov-Zhabotinskii (BZ) reaction is described by the Oregonator model and is used as a case study. We report two guidelines in selecting optimal numerical solver(s) for stiff, complex oscillatory systems: (i) for problems with unknown parameters, ode45 is the optimal choice regardless of the relative error tolerance; (ii) for known stiff problems, both ode113 and ode15s are good choices under strict relative tolerance conditions. Conclusions For any given biomolecular model, by building a library of numerical solvers with quantitative performance assessment metric, we show that it is possible
Characterisation of the structure of ocr, the gene 0.3 protein of bacteriophage T7
Atanasiu, C.; Byron, O.; McMiken, H.; Sturrock, S. S.; Dryden, D. T. F.
2001-01-01
The product of gene 0.3 of bacteriophage T7, ocr, is a potent inhibitor of type I DNA restriction and modification enzymes. We have used biophysical methods to examine the mass, stability, shape and surface charge distribution of ocr. Ocr is a dimeric protein with hydrodynamic behaviour equivalent to a prolate ellipsoid of axial ratio 4.3 ± 0.7:1 and mass of 27 kDa. The protein is resistant to denaturation but removal of the C-terminal region reduces stability substantially. Six amino acids, N4, D25, N43, D62, S68 and W94, are all located on the surface of the protein and N4 and S68 are also located at the interface between the two 116 amino acid monomers. Negatively charged amino acid side chains surround W94 but these side chains are not part of the highly acidic C-terminus after W94. Ocr is able to displace a short DNA duplex from the binding site of a type I enzyme with a dissociation constant of the order of 100 pM or better. These results suggest that ocr is of a suitable size and shape to effectively block the DNA binding site of a type I enzyme and has a large negatively charged patch on its surface. This charge distribution may be complementary to the charge distribution within the DNA binding site of type I DNA restriction and modification enzymes. PMID:11452031
Characterisation of the structure of ocr, the gene 0.3 protein of bacteriophage T7.
Atanasiu, C; Byron, O; McMiken, H; Sturrock, S S; Dryden, D T
2001-07-15
The product of gene 0.3 of bacteriophage T7, ocr, is a potent inhibitor of type I DNA restriction and modification enzymes. We have used biophysical methods to examine the mass, stability, shape and surface charge distribution of ocr. Ocr is a dimeric protein with hydrodynamic behaviour equivalent to a prolate ellipsoid of axial ratio 4.3 +/- 0.7:1 and mass of 27 kDa. The protein is resistant to denaturation but removal of the C-terminal region reduces stability substantially. Six amino acids, N4, D25, N43, D62, S68 and W94, are all located on the surface of the protein and N4 and S68 are also located at the interface between the two 116 amino acid monomers. Negatively charged amino acid side chains surround W94 but these side chains are not part of the highly acidic C-terminus after W94. Ocr is able to displace a short DNA duplex from the binding site of a type I enzyme with a dissociation constant of the order of 100 pM or better. These results suggest that ocr is of a suitable size and shape to effectively block the DNA binding site of a type I enzyme and has a large negatively charged patch on its surface. This charge distribution may be complementary to the charge distribution within the DNA binding site of type I DNA restriction and modification enzymes. PMID:11452031
Boltzmann Fluctuations in Numerical Simulations of Nonequilibrium Lattice Threshold Systems
Rundle, J.B.; Klein, W.; Gross, S.; Turcotte, D.L.
1995-08-21
Nonequilibrium threshold systems such as slider blocks are now used to model a variety of dynamical systems, including earthquake faults, driven neural networks, and sliding charge density waves. We show that for general mean field models driven at low rates fluctuations in the internal energy field are characterized by Boltzmann statistics. Numerical simulations confirm this prediction. Our results indicate that mean field models can be effectively treated as equilibrium systems.
Design of motorcycle rider protection systems using numerical techniques.
Miralbes, R
2013-10-01
The goal of this paper is the development of a design methodology, based on the use of finite elements numerical tools and dummies in order to study the damages and injuries that appear during a motorcyclist collision against a motorcyclist protection system (MPS). According to the existing regulation, a Hybrid III dummy FEM model has been used as a starting point and some modifications have been included. For instance a new finite element helmet model has been developed and later added to the dummy model. Moreover, some structural elements affecting the simulation results such as the connecting bolts or the ground have been adequately modeled. Finally there have been analyzed diverse types of current motorcyclists protection systems, for which it has been made a comparative numerical-experiment analysis to validate the numerical results and the methodology used. PMID:23792610
Numerical evaluation of the performance of active noise control systems
NASA Technical Reports Server (NTRS)
Mollo, C. G.; Bernhard, R. J.
1990-01-01
This paper presents a generalized numerical technique for evaluating the optimal performance of active noise controllers. In this technique, the indirect BEM numerical procedures are used to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the strength of the noise sources or the description of the enclosure boundary may not be known. The performance prediction for a single-input single-output system is presented, together with the analysis of the stability and observability of an active noise-control system employing detectors. The numerical procedures presented can be used for the design of both the physical configuration and the electronic components of the optimal active noise controller.
A review of numerical simulation of hydrothermal systems.
Mercer, J.W.; Faust, C.R.
1979-01-01
Many advances in simulating single and two-phase fluid flow and heat transport in porous media have recently been made in conjunction with geothermal energy research. These numerical models reproduce system thermal and pressure behaviour and can be used for other heat-transport problems, such as high-level radioactive waste disposal and heat-storage projects. -Authors
A Computer-Based Intelligent Assessment System for Numeric Disciplines.
ERIC Educational Resources Information Center
Patel, Ashok; Kinshuk; Russell, David
1998-01-01
Describes an intelligent assessment system for numeric disciplines that works in conjunction with the intelligent tutoring tools developed by Teaching and Learning Technology (TLTP) Byzantium, a consortium of six U.K. universities. Topics include intelligent tutoring tools based on cognitive apprenticeship framework, a history of computerized…
Development of a numerical simulation model of the cardiovascular system.
Geertsema, A A; Rakhorst, G; Mihaylov, D; Blanksma, P K; Verkerke, G J
1997-12-01
A numerical simulation model of the cardiovascular system has been developed. It consists of a model of the left atrium, the left ventricle, the coronary vascular system, the aorta, the arterial system, and the venous system. The input of the complete model is the elastance (pressure/volume ratio) developed by the left ventricle. The shape of this elastance is constant in different circumstances. Left ventricular (LV) myocardial oxygen consumption and the amount of oxygen offered to the left ventricle can be calculated with the model. The model has been validated using data from a patient suffering from coronary artery disease. The measured clinical hemodynamical waveforms could be fitted to those generated by the model. With the numerical simulation model, it is possible to predict the functioning of the left ventricle under different circumstances. This makes it possible to study in vitro various pathological clinical situations. PMID:9423983
NASA Technical Reports Server (NTRS)
Kiang, Richard K.
1992-01-01
Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.
Numerical models for the evaluation of geothermal systems
Bodvarsson, G.S.; Pruess, K.; Lippmann, M.J.
1986-08-01
We have carried out detailed simulations of various fields in the USA (Bada, New Mexico; Heber, California); Mexico (Cerro Prieto); Iceland (Krafla); and Kenya (Olkaria). These simulation studies have illustrated the usefulness of numerical models for the overall evaluation of geothermal systems. The methodology for modeling the behavior of geothermal systems, different approaches to geothermal reservoir modeling and how they can be applied in comprehensive evaluation work are discussed.
Numerical simulations of strongly correlated electron and spin systems
NASA Astrophysics Data System (ADS)
Changlani, Hitesh Jaiprakash
Developing analytical and numerical tools for strongly correlated systems is a central challenge for the condensed matter physics community. In the absence of exact solutions and controlled analytical approximations, numerical techniques have often contributed to our understanding of these systems. Exact Diagonalization (ED) requires the storage of at least two vectors the size of the Hilbert space under consideration (which grows exponentially with system size) which makes it affordable only for small systems. The Density Matrix Renormalization Group (DMRG) uses an intelligent Hilbert space truncation procedure to significantly reduce this cost, but in its present formulation is limited to quasi-1D systems. Quantum Monte Carlo (QMC) maps the Schrodinger equation to the diffusion equation (in imaginary time) and only samples the eigenvector over time, thereby avoiding the memory limitation. However, the stochasticity involved in the method gives rise to the "sign problem" characteristic of fermion and frustrated spin systems. The first part of this thesis is an effort to make progress in the development of a numerical technique which overcomes the above mentioned problems. We consider novel variational wavefunctions, christened "Correlator Product States" (CPS), that have a general functional form which hopes to capture essential correlations in the ground states of spin and fermion systems in any dimension. We also consider a recent proposal to modify projector (Green's Function) Quantum Monte Carlo to ameliorate the sign problem for realistic and model Hamiltonians (such as the Hubbard model). This exploration led to our own set of improvements, primarily a semistochastic formulation of projector Quantum Monte Carlo. Despite their limitations, existing numerical techniques can yield physical insights into a wide variety of problems. The second part of this thesis considers one such numerical technique - DMRG - and adapts it to study the Heisenberg antiferromagnet
High numerical aperture projection system for extreme ultraviolet projection lithography
Hudyma, Russell M.
2000-01-01
An optical system is described that is compatible with extreme ultraviolet radiation and comprises five reflective elements for projecting a mask image onto a substrate. The five optical elements are characterized in order from object to image as concave, convex, concave, convex, and concave mirrors. The optical system is particularly suited for ring field, step and scan lithography methods. The invention uses aspheric mirrors to minimize static distortion and balance the static distortion across the ring field width which effectively minimizes dynamic distortion. The present invention allows for higher device density because the optical system has improved resolution that results from the high numerical aperture, which is at least 0.14.
Numerical System Solver Developed for the National Cycle Program
NASA Technical Reports Server (NTRS)
Binder, Michael P.
1999-01-01
As part of the National Cycle Program (NCP), a powerful new numerical solver has been developed to support the simulation of aeropropulsion systems. This software uses a hierarchical object-oriented design. It can provide steady-state and time-dependent solutions to nonlinear and even discontinuous problems typically encountered when aircraft and spacecraft propulsion systems are simulated. It also can handle constrained solutions, in which one or more factors may limit the behavior of the engine system. Timedependent simulation capabilities include adaptive time-stepping and synchronization with digital control elements. The NCP solver is playing an important role in making the NCP a flexible, powerful, and reliable simulation package.
Numerical Modeling of Flow Distribution in Micro-Fluidics Systems
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Cole, Helen; Chen, C. P.
2005-01-01
This paper describes an application of a general purpose computer program, GFSSP (Generalized Fluid System Simulation Program) for calculating flow distribution in a network of micro-channels. GFSSP employs a finite volume formulation of mass and momentum conservation equations in a network consisting of nodes and branches. Mass conservation equation is solved for pressures at the nodes while the momentum conservation equation is solved at the branches to calculate flowrate. The system of equations describing the fluid network is solved by a numerical method that is a combination of the Newton-Raphson and successive substitution methods. The numerical results have been compared with test data and detailed CFD (computational Fluid Dynamics) calculations. The agreement between test data and predictions is satisfactory. The discrepancies between the predictions and test data can be attributed to the frictional correlation which does not include the effect of surface tension or electro-kinetic effect.
Numerical Three-Dimensional Model of Airport Terminal Drainage System
NASA Astrophysics Data System (ADS)
Strzelecki, Michał
2014-03-01
During the construction of an airport terminal it was found that as a result of the hydrostatic pressure of underground water the foundation plate of the building had dangerously shifted in the direction opposite to that of the gravitational forces. The only effective measure was to introduce a drainage system on the site. The complex geology of the area indicated that two independent drainage systems, i.e., a horizontal system in the Quaternary beds and a vertical system in the Tertiary water-bearing levels, were necessary. This paper presents numerical FEM calculations of the two drainage systems being part of the airport terminal drainaged esign. The computer simulation which was carried out took into consideration the actual effect of the drainage systems and their impact on the depression cone being formed in the two aquifers.
The use of Optical Character Recognition (OCR) in the digitisation of herbarium specimen labels.
Drinkwater, Robyn E; Cubey, Robert W N; Haston, Elspeth M
2014-01-01
At the Royal Botanic Garden Edinburgh (RBGE) the use of Optical Character Recognition (OCR) to aid the digitisation process has been investigated. This was tested using a herbarium specimen digitisation process with two stages of data entry. Records were initially batch-processed to add data extracted from the OCR text prior to being sorted based on Collector and/or Country. Using images of the specimens, a team of six digitisers then added data to the specimen records. To investigate whether the data from OCR aid the digitisation process, they completed a series of trials which compared the efficiency of data entry between sorted and unsorted batches of specimens. A survey was carried out to explore the opinion of the digitisation staff to the different sorting options. In total 7,200 specimens were processed. When compared to an unsorted, random set of specimens, those which were sorted based on data added from the OCR were quicker to digitise. Of the methods tested here, the most successful in terms of efficiency used a protocol which required entering data into a limited set of fields and where the records were filtered by Collector and Country. The survey and subsequent discussions with the digitisation staff highlighted their preference for working with sorted specimens, in which label layout, locations and handwriting are likely to be similar, and so a familiarity with the Collector or Country is rapidly established. PMID:25009435
Sim, Ida; Tu, Samson W.; Carini, Simona; Lehmann, Harold P.; Pollock, Brad H.; Peleg, Mor; Wittkowski, Knut M.
2013-01-01
To date, the scientific process for generating, interpreting, and applying knowledge has received less informatics attention than operational processes for conducting clinical studies. The activities of these scientific processes — the science of clinical research — are centered on the study protocol, which is the abstract representation of the scientific design of a clinical study. The Ontology of Clinical Research (OCRe) is an OWL 2 model of the entities and relationships of study design protocols for the purpose of computationally supporting the design and analysis of human studies. OCRe’s modeling is independent of any specific study design or clinical domain. It includes a study design typology and a specialized module called ERGO Annotation for capturing the meaning of eligibility criteria. In this paper, we describe the key informatics use cases of each phase of a study’s scientific lifecycle, present OCRe and the principles behind its modeling, and describe applications of OCRe and associated technologies to a range of clinical research use cases. OCRe captures the central semantics that underlies the scientific processes of clinical research and can serve as an informatics foundation for supporting the entire range of knowledge activities that constitute the science of clinical research. PMID:24239612
Automatic Cataloguing and Searching for Retrospective Data by Use of OCR Text.
ERIC Educational Resources Information Center
Tseng, Yuen-Hsien
2001-01-01
Describes efforts in supporting information retrieval from OCR (optical character recognition) degraded text. Reports on approaches used in an automatic cataloging and searching contest for books in multiple languages, including a vector space retrieval model, an n-gram indexing method, and a weighting scheme; and discusses problems of Asian…
The use of Optical Character Recognition (OCR) in the digitisation of herbarium specimen labels
Drinkwater, Robyn E.; Cubey, Robert W. N.; Haston, Elspeth M.
2014-01-01
Abstract At the Royal Botanic Garden Edinburgh (RBGE) the use of Optical Character Recognition (OCR) to aid the digitisation process has been investigated. This was tested using a herbarium specimen digitisation process with two stages of data entry. Records were initially batch-processed to add data extracted from the OCR text prior to being sorted based on Collector and/or Country. Using images of the specimens, a team of six digitisers then added data to the specimen records. To investigate whether the data from OCR aid the digitisation process, they completed a series of trials which compared the efficiency of data entry between sorted and unsorted batches of specimens. A survey was carried out to explore the opinion of the digitisation staff to the different sorting options. In total 7,200 specimens were processed. When compared to an unsorted, random set of specimens, those which were sorted based on data added from the OCR were quicker to digitise. Of the methods tested here, the most successful in terms of efficiency used a protocol which required entering data into a limited set of fields and where the records were filtered by Collector and Country. The survey and subsequent discussions with the digitisation staff highlighted their preference for working with sorted specimens, in which label layout, locations and handwriting are likely to be similar, and so a familiarity with the Collector or Country is rapidly established. PMID:25009435
Interferometric correction system for a numerically controlled machine
Burleson, Robert R.
1978-01-01
An interferometric correction system for a numerically controlled machine is provided to improve the positioning accuracy of a machine tool, for example, for a high-precision numerically controlled machine. A laser interferometer feedback system is used to monitor the positioning of the machine tool which is being moved by command pulses to a positioning system to position the tool. The correction system compares the commanded position as indicated by a command pulse train applied to the positioning system with the actual position of the tool as monitored by the laser interferometer. If the tool position lags the commanded position by a preselected error, additional pulses are added to the pulse train applied to the positioning system to advance the tool closer to the commanded position, thereby reducing the lag error. If the actual tool position is leading in comparison to the commanded position, pulses are deleted from the pulse train where the advance error exceeds the preselected error magnitude to correct the position error of the tool relative to the commanded position.
Understanding disordered systems through numerical simulation and algorithm development
NASA Astrophysics Data System (ADS)
Sweeney, Sean Michael
Disordered systems arise in many physical contexts. Not all matter is uniform, and impurities or heterogeneities can be modeled by fixed random disorder. Numerous complex networks also possess fixed disorder, leading to applications in transportation systems, telecommunications, social networks, and epidemic modeling, to name a few. Due to their random nature and power law critical behavior, disordered systems are difficult to study analytically. Numerical simulation can help overcome this hurdle by allowing for the rapid computation of system states. In order to get precise statistics and extrapolate to the thermodynamic limit, large systems must be studied over many realizations. Thus, innovative algorithm development is essential in order reduce memory or running time requirements of simulations. This thesis presents a review of disordered systems, as well as a thorough study of two particular systems through numerical simulation, algorithm development and optimization, and careful statistical analysis of scaling properties. Chapter 1 provides a thorough overview of disordered systems, the history of their study in the physics community, and the development of techniques used to study them. Topics of quenched disorder, phase transitions, the renormalization group, criticality, and scale invariance are discussed. Several prominent models of disordered systems are also explained. Lastly, analysis techniques used in studying disordered systems are covered. In Chapter 2, minimal spanning trees on critical percolation clusters are studied, motivated in part by an analytic perturbation expansion by Jackson and Read that I check against numerical calculations. This system has a direct mapping to the ground state of the strongly disordered spin glass. We compute the path length fractal dimension of these trees in dimensions d = {2, 3, 4, 5} and find our results to be compatible with the analytic results suggested by Jackson and Read. In Chapter 3, the random bond Ising
Numerical simulations and modeling for stochastic biological systems with jumps
NASA Astrophysics Data System (ADS)
Zou, Xiaoling; Wang, Ke
2014-05-01
This paper gives a numerical method to simulate sample paths for stochastic differential equations (SDEs) driven by Poisson random measures. It provides us a new approach to simulate systems with jumps from a different angle. The driving Poisson random measures are assumed to be generated by stationary Poisson point processes instead of Lévy processes. Methods provided in this paper can be used to simulate SDEs with Lévy noise approximately. The simulation is divided into two parts: the part of jumping integration is based on definition without approximation while the continuous part is based on some classical approaches. Biological explanations for stochastic integrations with jumps are motivated by several numerical simulations. How to model biological systems with jumps is showed in this paper. Moreover, method of choosing integrands and stationary Poisson point processes in jumping integrations for biological models are obtained. In addition, results are illustrated through some examples and numerical simulations. For some examples, earthquake is chose as a jumping source which causes jumps on the size of biological population.
INEX (integrated numerical experiment) simulations of the Boeing FEL system
Tokar, R.L.; Young, L.M.; Lumpkin, A.H.; McVey, B.D.; Thode, L.E.; Bender, S.C.; Chan, K.C.D. ); Yeremian, A.D.; Dowell, D.H.; Lowrey, A.R. )
1989-01-01
The INEX (integrated numerical experiment) numerical model is applied to the 0.6 {mu}m FEL oscillator at Boeing Aerospace and Electronics Company in Seattle, WA. This system consists of a 110 MeV L-band rf linac, a beam transport line from the accelerator to the entrance of the wiggler, the 5.0 meter THUNDER variable taper wiggler, and a near concentric two mirror optical oscillator. Many aspects of the model for the electron beam accelerator and transport line agree with experimental measurements. Predictions for lasing performance are compared with data obtained in May and June 1989 using a mild tapered wiggler. We obtain good agreement with the achieved extraction efficiency, while 1D pulse simulations reproduce the observed sideband instability. 15 refs., 11 figs.
Numerical simulation of iontophoresis in the drug delivery system.
Filipovic, Nenad; Zivanovic, Marko; Savic, Andrej; Bijelic, Goran
2016-01-01
The architecture and composition of stratum corneum act as barriers and limit the diffusion of most drug molecules and ions. Much effort has been made to overcome this barrier and it can be seen that iontophoresis has shown a good effect. Iontophoresis represents the application of low electrical potential to increase the transport of drugs into and across the skin or tissue. Iontophoresis is a noninvasive drug delivery system, and therefore, it is a useful alternative to drug transportation by injection. In this study, we present a numerical model and effects of electrical potential on the drug diffusion in the buccal tissue and the stratum corneum. The initial numerical results are in good comparison with experimental observation. We demonstrate that the application of an applied voltage can greatly improve the efficacy of localized drug delivery as compared to diffusion alone. PMID:26592537
Numerical Simulations of the Solar Orbiter Antenna System RPW ANT
NASA Astrophysics Data System (ADS)
Sampl, M.; Rucker, H. O.; Oswald, T. H.; Plettemeier, D.; Maksimovic, M.; Macher, W.
The high-frequency electric sensors onboard Solar Orbiter are part of the radio and plasma wave experiment (RPW). The sensors consist of cylindrical antennas (ANT) mounted on three booms extruded from the central body of the spacecraft. Due to the parasitic effects of the conducting spacecraft body and solar panels the true antenna properties (effective axes and length, capacitances) do not coincide with their physical representations. The numerical analysis of the reception properties of these antennas is presented. In order to analyze the antenna system we applied a numerical method. The current distribution on the spacecraft body and the effective length vector was calculated, by solving the underlying field equations using electromagnetic code. In the applied method the spacecraft is modeled as a mesh-grid.
Numerical simulations of the thermoacoustic computed tomography breast imaging system
NASA Astrophysics Data System (ADS)
Kiser, William Lester, Jr.
A thermoacoustic wave is produced when an object absorbs energy and experiences a subsequent thermal expansion. We have developed a Thermoacoustic Computed Tomography (TACT) breast imaging system to exploit the thermoacoustic phenomena as a method of soft tissue imaging. By exposing the breast to short pulses of 434 MHz microwaves, ultrasonic pulses are generated and detected with a hemispherical transducer array submersed in a water bath. Filtering and back projecting the transducer signals generates a 3-D image that maps the localized microwave absorption properties of the breast. In an effort to understand the factors limiting image quality, the TACT system was numerically simulated. The simulations were used to generate the transducer signals that would be collected by the TACT system during a scan of an object. These simulated data streams were then fed into the system image reconstruction software to provide images of simulated phantoms. The effects of transducer diameter, transducer response, transducer array geometry and stimulating pulse width on the spatial and contrast resolution of the system were quantified using the simulations. The spatial resolution was highly dependent upon location in the imaging volume. This was due to the off axis response of transducers of finite aperture. Simulated data were compared with experimental data, obtained by imaging a parallel-piped resolution phantom, to verify the accuracy of the simulation code. A contrast-detail phantom was numerically simulated to determine the ability of the system to image spheres of diameters <1 cm with absorption values on the order of physiologic saline, when located in a background of noise. The results of the contrast-detail analysis were dependent on the location of the spheres in the imaging volume and the diameter of the simulated transducers. This work sets the foundation for the initial image quality studies of the TACT system. Improvements to the current imaging system, based on
Numerical weather prediction model tuning via ensemble prediction system
NASA Astrophysics Data System (ADS)
Jarvinen, H.; Laine, M.; Ollinaho, P.; Solonen, A.; Haario, H.
2011-12-01
This paper discusses a novel approach to tune predictive skill of numerical weather prediction (NWP) models. NWP models contain tunable parameters which appear in parameterizations schemes of sub-grid scale physical processes. Currently, numerical values of these parameters are specified manually. In a recent dual manuscript (QJRMS, revised) we developed a new concept and method for on-line estimation of the NWP model parameters. The EPPES ("Ensemble prediction and parameter estimation system") method requires only minimal changes to the existing operational ensemble prediction infra-structure and it seems very cost-effective because practically no new computations are introduced. The approach provides an algorithmic decision making tool for model parameter optimization in operational NWP. In EPPES, statistical inference about the NWP model tunable parameters is made by (i) generating each member of the ensemble of predictions using different model parameter values, drawn from a proposal distribution, and (ii) feeding-back the relative merits of the parameter values to the proposal distribution, based on evaluation of a suitable likelihood function against verifying observations. In the presentation, the method is first illustrated in low-order numerical tests using a stochastic version of the Lorenz-95 model which effectively emulates the principal features of ensemble prediction systems. The EPPES method correctly detects the unknown and wrongly specified parameters values, and leads to an improved forecast skill. Second, results with an atmospheric general circulation model based ensemble prediction system show that the NWP model tuning capacity of EPPES scales up to realistic models and ensemble prediction systems. Finally, a global top-end NWP model tuning exercise with preliminary results is published.
Numerical Propulsion System Simulation (NPSS) 1999 Industry Review
NASA Technical Reports Server (NTRS)
Lytle, John; Follen, Greg; Naiman, Cynthia; Evans, Austin
2000-01-01
The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia, and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective, high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. In addition, the paper contains a summary of the feedback received from industry partners in the development effort and the actions taken over the past year to respond to that feedback. The NPSS development was supported in FY99 by the High Performance Computing and Communications Program.
Numerical and experimental investigation of a rockfall drapery system
NASA Astrophysics Data System (ADS)
Thoeni, K.; Giacomini, A.; Lambert, C.; Sloan, S. W.
2012-04-01
Rockfalls represent a significant hazard to people and infrastructures in steep terrain, should it be a mountainous region, a quarry, or a mine. Although rockfall occurrences cannot be totally eliminated, it is possible to reduce the risk by deploying effective rockfall protective systems such as metallic wire mesh draperies. This work focuses on the performance of a simple drapery system with a double-twisted hexagonal wire mesh. Numerical modelling and experimental investigations have been performed. The main objective of the work is the residual hazard assessment in conjunction with such a system since blocks can still detach between the installed drapery and the rock surface. First, the numerical model for the drapery mesh and the rock slope is presented. Following the approach by Bertrand et al. [1], a discrete element model of a hexagonal wire mesh has been implemented into the open-source framework YADE [4]. The mesh is discretised by a set of spherical particles which interact remotely (i.e. interactions between the particles exist without direct contact) and are located at the physical nodes of the mesh. The rock slope is represented by triangular elements which have been generated on the basis of a point cloud representation of the rock slope. The slope is assumed to be rigid and energy dissipation on the slope during rock impact is considered via friction and viscous damping. Second, results of field tests carried out at a mine in New South Wales (Australia) are presented [3]. Concrete blocks with shapes according to EOTA [2] were released from the top of a highwall. The tests were carried out on two different sections of the highwall: the first section had a drapery system installed whereas the second section had no protective system installed. In the first section, the blocks were released between the rock surface and the mesh drapery. The 3D block trajectories were recorded by using two stereo pairs of synchronised high speed cameras. The collected
The hydraulic system of trees: theoretical framework and numerical simulation
Fruh; Kurth
1999-12-21
Empirical studies pose the problem of the physiological integration of the tree organism, which is also important on the scale of ecosystems. Recently, spatially distributed models emerged, which approach this problem by reflecting the close linkage between physiological processes and the structures of trees and tree stands. In the case of water flow, the tree organism can be regarded as hydraulic system and the branched tree architecture as hydraulic network. Previous models of the hydraulic system either did not take into account the network structure, or they had shortcomings regarding the translation of the underlying physiological assumptions by the discrete computation method. We have developed a theoretical framework which takes the form of a numerical simulation model of tree water flow. A discrete initial boundary value problem (IBVP) combines the phenomena of Darcy flow, water storage and conductivity losses in the hydraulic network. The software HYDRA computes the solution of the IBVP. The theoretical derivation and model tests corroborate the consistent translation of the physiological assumptions by the computational method. Simulation studies enabled us to formulate hypotheses on the following points: (1) differences in the hydraulic segmentation between Picea abies and Thuja occidentalis, (2) responses of the hydraulic system to rapid transpiration changes and to a scenario of drought stress, and (3) how these responses depend on architectural quantities of the trees. The simulation studies demonstrated our possibilities of deriving theoretically well-founded hypotheses about the functioning of the hydraulic system and its relation to system structure. The numerical simulation model is designed as a tool for structure-function studies, which is able to treat tree architecture as independent variable. The model supports the integration of data on tree level, and it can be used for computer experiments which quantify the dynamics of the hydraulic
Numerical studies of identification in nonlinear distributed parameter systems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Lo, C. K.; Reich, Simeon; Rosen, I. G.
1989-01-01
An abstract approximation framework and convergence theory for the identification of first and second order nonlinear distributed parameter systems developed previously by the authors and reported on in detail elsewhere are summarized and discussed. The theory is based upon results for systems whose dynamics can be described by monotone operators in Hilbert space and an abstract approximation theorem for the resulting nonlinear evolution system. The application of the theory together with numerical evidence demonstrating the feasibility of the general approach are discussed in the context of the identification of a first order quasi-linear parabolic model for one dimensional heat conduction/mass transport and the identification of a nonlinear dissipation mechanism (i.e., damping) in a second order one dimensional wave equation. Computational and implementational considerations, in particular, with regard to supercomputing, are addressed.
Numerical database system based on a weighted search tree
NASA Astrophysics Data System (ADS)
Park, S. C.; Bahri, C.; Draayer, J. P.; Zheng, S.-Q.
1994-09-01
An on-line numerical database system, that is based on the concept of a weighted search tree and which functions like a file directory, is introduced. The system, which is designed to aid in reducing time-consuming redundant calculations in numerically intensive computations, can be used to fetch, insert and delete items from a dynamically generated list in optimal [ O(log n) where n is the number of items in the list] time. Items in the list are ordered according to a priority queue with the initial priority for each element set either automatically or by an user supplied algorithm. The priority queue is updated on-the-fly to reflect element hit frequency. Items can be added to a database so long as there is space to accommodate them, and when there is not, the lowest priority element(s) is removed to make room for an incoming element(s) with higher priority. The system acts passively and therefore can be applied to any number of databases, with the same or different structures, within a single application.
Numerical Study of a Four-Roll Coating System
NASA Astrophysics Data System (ADS)
Tsuda, Takeaki
The characteristics of a four-roll coating system were numerically investigated and compared with experimental data to validate the theoretical models used in this study. In the theoretical models, a film splitting model using a power-law-type equation, a roll-gap model based on elastohydrodynamics, and a flow model from a rotating-cylinder system were applied. The parametric computations for each operational condition revealed the steady and dynamic behaviors of a coating film and liquid films on the coating rolls. The results of the frequency response to the speed disturbances of the coating rolls indicated that the sensitivity of the lowest coating roll to the disturbance was half that of the others; this implies that the requirement for the accuracy of a driving system of the coating roll is not as severe as compared with others. The experimental data and the numerical results at steady state agreed well. Therefore, the theoretical models used in this research were found to be appropriate.
Integrated numerical methods for hypersonic aircraft cooling systems analysis
NASA Technical Reports Server (NTRS)
Petley, Dennis H.; Jones, Stuart C.; Dziedzic, William M.
1992-01-01
Numerical methods have been developed for the analysis of hypersonic aircraft cooling systems. A general purpose finite difference thermal analysis code is used to determine areas which must be cooled. Complex cooling networks of series and parallel flow can be analyzed using a finite difference computer program. Both internal fluid flow and heat transfer are analyzed, because increased heat flow causes a decrease in the flow of the coolant. The steady state solution is a successive point iterative method. The transient analysis uses implicit forward-backward differencing. Several examples of the use of the program in studies of hypersonic aircraft and rockets are provided.
Integrating Numerical Groundwater Modeling Results With Geographic Information Systems
NASA Astrophysics Data System (ADS)
Witkowski, M. S.; Robinson, B. A.; Linger, S. P.
2001-12-01
Many different types of data are used to create numerical models of flow and transport of groundwater in the vadose zone. Results from water balance studies, infiltration models, hydrologic properties, and digital elevation models (DEMs) are examples of such data. Because input data comes in a variety of formats, for consistency the data need to be assembled in a coherent fashion on a single platform. Through the use of a geographic information system (GIS), all data sources can effectively be integrated on one platform to store, retrieve, query, and display data. In our vadoze zone modeling studies in support of Los Alamos National Laboratory's Environmental Restoration Project, we employ a GIS comprised of a Raid storage device, an Oracle database, ESRI's spatial database engine (SDE), ArcView GIS, and custom GIS tools for three-dimensional (3D) analysis. We store traditional GIS data, such as, contours, historical building footprints, and study area locations, as points, lines, and polygons with attributes. Numerical flow and transport model results from the Finite Element Heat and Mass Transfer Code (FEHM) are stored as points with attributes, such as fluid saturation, or pressure, or contaminant concentration at a given location. We overlay traditional types of GIS data with numerical model results, thereby allowing us to better build conceptual models and perform spatial analyses. We have also developed specialized analysis tools to assist in the data and model analysis process. This approach provides an integrated framework for performing tasks such as comparing the model to data and understanding the relationship of model predictions to existing contaminant source locations and water supply wells. Our process of integrating GIS and numerical modeling results allows us to answer a wide variety of questions about our conceptual model design: - Which set of locations should be identified as contaminant sources based on known historical building operations
Numerical approaches to isolated many-body quantum systems
NASA Astrophysics Data System (ADS)
Kolodrubetz, Michael H.
Ultracold atoms have revolutionized atomic and condensed matter physics. In addition to having clean, controllable Hamiltonians, ultracold atoms are near-perfect realizations of isolated quantum systems, in which weak environmental coupling can be neglected on experimental time scales. This opens new opportunities to explore these systems not just in thermal equilibrium, but out of equilibrium as well. In this dissertation, we investigate some properties of closed quantum systems, utilizing a combination of numerical and analytical techniques. We begin by applying full configuration-interaction quantum Monte Carlo (FCIQMC) to the Fermi polaron, which we use as a test bed to improve the algorithm. In addition to adapting standard QMC techniques, we introduce novel controlled approximations that allow mitigation of the sign problem and simulation directly in the thermodynamic limit. We also contrast the sign problem of FCIQMC with that of more standard techniques, focusing on FCIQMC's capacity to work in a second quantized determinant space. Next, we discuss nonequilibrium dynamics near a quantum critical point, focusing on the one-dimensional transverse-field Ising (TFI) chain. We show that the TFI dynamics exhibit critical scaling, within which the spin correlations exhibit qualitatively athermal behavior. We provide strong numerical evidence for the universality of dynamic scaling by utilizing time-dependent matrix product states to simulate a non-integrable model in the same equilibrium universality class. As this non-integrable model has been realized experimentally, we investigate the robustness of our predictions against the presence of open boundary conditions and disorder. We find that the qualitatively athermal correlations remain visible, although other phenomena such as even/odd effects become relevant within the finite size scaling theory. Finally, we investigate the properties of the integrable TFI model upon varying the strength of a non
Configuration Management File Manager Developed for Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
Follen, Gregory J.
1997-01-01
One of the objectives of the High Performance Computing and Communication Project's (HPCCP) Numerical Propulsion System Simulation (NPSS) is to provide a common and consistent way to manage applications, data, and engine simulations. The NPSS Configuration Management (CM) File Manager integrated with the Common Desktop Environment (CDE) window management system provides a common look and feel for the configuration management of data, applications, and engine simulations for U.S. engine companies. In addition, CM File Manager provides tools to manage a simulation. Features include managing input files, output files, textual notes, and any other material normally associated with simulation. The CM File Manager includes a generic configuration management Application Program Interface (API) that can be adapted for the configuration management repositories of any U.S. engine company.
Systematic analytical and numerical studies of highly correlated electron systems
NASA Astrophysics Data System (ADS)
Tsai, Shan-Wen
Strong electron correlations in condensed matter systems give rise to a wide range of striking physical properties, producing phenomena as varied as high temperature superconductivity, metal-insulator transitions and the integer and fractional quantum Hall effects. Quantum critical systems also exhibit strong correlations between a large number of degrees of freedom. In this thesis we study these complicated systems using a combination of analytical and numerical approaches. We perform systematic investigations, which adds to the robustness of our results. We develop a new method, based on the density-matrix renormalization-group (DMRG) algorithm combined with finite-size scaling analysis, to study critical behavior in quantum spin chains and extract critical exponents. Accurate results are obtained for spin-1/2 antiferromagnetic chains and the spin-1 chain at the critical point separating the Haldane and the dimerized phases. Disorder in a system can change its properties drastically. Plateau transitions in the integer quantum Hall effect provide the clearest example of quantum critical behavior in a disordered system. We provide analytical proof that the Chalker-Coddington model, which is used to describe the plateau transitions, is quantum critical. Starting from a field theory based on this model, equivalent to a non-Hermitian supersymmetric spin chain, we prove quantum criticality by a Lieb-Schultz-Mattis type theorem. This approach was motivated by numerical results obtained using the DMRG/finite-size scaling method. Our generalized LSM theorem also applies to the spin quantum Hall effect, which can appear in disordered d-wave superconductors with broken time-reversal symmetry. The last part of the thesis is a renormalization-group study of two dimensional interacting electron systems. We obtain results relevant to high-temperature superconductors and also to the family of kappa - (BEDT - TTF)2X organic superconductors. At half filling, the fully nested
Lexicon-supported OCR of eighteenth century Dutch books: a case study
NASA Astrophysics Data System (ADS)
de Does, Jesse; Depuydt, Katrien
2013-01-01
We report on a case study on OCR of eighteenth century books conducted in the IMPACT project. After introducing the IMPACT project and its approach to lexicon building and deployment, we zoom in to the application of IMPACT tools and data to the Dutch EDBO collection. The results are exemplified by detailed discussion of various practical options to improve text recognition beyond a baseline of running an uncustomized Finereader 10. In particular, we discuss improved recognition of long s.
Wind Tunnel to Flight: Numerical Simulations of Hypersonic Propulsion Systems
NASA Astrophysics Data System (ADS)
Iaccarino, Gianluca
2009-11-01
Uncertainties in the flight conditions and limitations of ground based facilities create inherent difficulties in assessing the performance of hypersonic propulsion systems. We use numerical simulations to investigate the correlation of wind-tunnel measurements (Steelant et al., 2006) and flight data (Hass et al., 2005) for the HyShot vehicle; the objective is to identify potential engine unstart events occurring under different combustion regimes. As a first step we perform simulations corresponding to both reacting and non-reacting conditions in the ground-based facility to validate the numerical tools. Next, we focus on reproducing the flight conditions; a fundamental difficulty is the lack of precise information about the vehicle trajectory. A Bayesian inversion strategy is used to infer the altitude, angle of attack and Mach number from the noisy pressure measurements collected during the flight. The estimated conditions, together with the scatter due to the measurement uncertainty, are then used to study the flow and thermal fields in the combustor. The details of the methods used to characterize the uncertainty in the flow simulations and to perform the Bayesian inversion will also be discussed.
A numerical solution for the diffusion equation in hydrogeologic systems
Ishii, A.L.; Healy, R.W.; Striegl, R.G.
1989-01-01
The documentation of a computer code for the numerical solution of the linear diffusion equation in one or two dimensions in Cartesian or cylindrical coordinates is presented. Applications of the program include molecular diffusion, heat conduction, and fluid flow in confined systems. The flow media may be anisotropic and heterogeneous. The model is formulated by replacing the continuous linear diffusion equation by discrete finite-difference approximations at each node in a block-centered grid. The resulting matrix equation is solved by the method of preconditioned conjugate gradients. The conjugate gradient method does not require the estimation of iteration parameters and is guaranteed convergent in the absence of rounding error. The matrixes are preconditioned to decrease the steps to convergence. The model allows the specification of any number of boundary conditions for any number of stress periods, and the output of a summary table for selected nodes showing flux and the concentration of the flux quantity for each time step. The model is written in a modular format for ease of modification. The model was verified by comparison of numerical and analytical solutions for cases of molecular diffusion, two-dimensional heat transfer, and axisymmetric radial saturated fluid flow. Application of the model to a hypothetical two-dimensional field situation of gas diffusion in the unsaturated zone is demonstrated. The input and output files are included as a check on program installation. The definition of variables, input requirements, flow chart, and program listing are included in the attachments. (USGS)
Numerical Analysis of a Radiant Heat Flux Calibration System
NASA Technical Reports Server (NTRS)
Jiang, Shanjuan; Horn, Thomas J.; Dhir, V. K.
1998-01-01
A radiant heat flux gage calibration system exists in the Flight Loads Laboratory at NASA's Dryden Flight Research Center. This calibration system must be well understood if the heat flux gages calibrated in it are to provide useful data during radiant heating ground tests or flight tests of high speed aerospace vehicles. A part of the calibration system characterization process is to develop a numerical model of the flat plate heater element and heat flux gage, which will help identify errors due to convection, heater element erosion, and other factors. A 2-dimensional mathematical model of the gage-plate system has been developed to simulate the combined problem involving convection, radiation and mass loss by chemical reaction. A fourth order finite difference scheme is used to solve the steady state governing equations and determine the temperature distribution in the gage and plate, incident heat flux on the gage face, and flat plate erosion. Initial gage heat flux predictions from the model are found to be within 17% of experimental results.
Numerical investigation and recommendations for push-pull ventilation systems.
Chern, Ming-Jyh; Ma, Chen-Hsuan
2007-03-01
This study presents numerical simulations of push-pull ventilation systems. A push-pull system is a device commonly used in capturing pollutants from large tanks used in industrial chemical processes. An air jet is blown from one side of a tank and collected by an exhaust hood on the opposite side of the tank. In this study, a finite volume model coupled with the standard k -epsilon turbulent model is employed to describe the flow structures and characteristics. Moreover, the turbulence mass transfer equation is adopted to show the concentration distribution above the open surface tank. All the flow fields can be classified according to four dominant modes, i.e., dispersion, transition, encapsulation, and strong suction. The push and pull flow velocities should be adjusted into encapsulation and strong suction modes to ensure all pollutants can be captured by the exhaust hood. Other geometric parameters such as the flange size, pull-channel size, offset distance, etc., also influence the flow characteristics. For a variety of lengths of tanks and pollutant evaporation velocities, the push and pull flow velocity must be matched to achieve optimal operation. Furthermore, the flange size and other parameters are determined to enhance the capture efficiency of the push-pull system. Recommendations for design guidelines are introduced in this study. PMID:17237024
SAMSAN- MODERN NUMERICAL METHODS FOR CLASSICAL SAMPLED SYSTEM ANALYSIS
NASA Technical Reports Server (NTRS)
Frisch, H. P.
1994-01-01
SAMSAN was developed to aid the control system analyst by providing a self consistent set of computer algorithms that support large order control system design and evaluation studies, with an emphasis placed on sampled system analysis. Control system analysts have access to a vast array of published algorithms to solve an equally large spectrum of controls related computational problems. The analyst usually spends considerable time and effort bringing these published algorithms to an integrated operational status and often finds them less general than desired. SAMSAN reduces the burden on the analyst by providing a set of algorithms that have been well tested and documented, and that can be readily integrated for solving control system problems. Algorithm selection for SAMSAN has been biased toward numerical accuracy for large order systems with computational speed and portability being considered important but not paramount. In addition to containing relevant subroutines from EISPAK for eigen-analysis and from LINPAK for the solution of linear systems and related problems, SAMSAN contains the following not so generally available capabilities: 1) Reduction of a real non-symmetric matrix to block diagonal form via a real similarity transformation matrix which is well conditioned with respect to inversion, 2) Solution of the generalized eigenvalue problem with balancing and grading, 3) Computation of all zeros of the determinant of a matrix of polynomials, 4) Matrix exponentiation and the evaluation of integrals involving the matrix exponential, with option to first block diagonalize, 5) Root locus and frequency response for single variable transfer functions in the S, Z, and W domains, 6) Several methods of computing zeros for linear systems, and 7) The ability to generate documentation "on demand". All matrix operations in the SAMSAN algorithms assume non-symmetric matrices with real double precision elements. There is no fixed size limit on any matrix in any
Numerical investigation of seismic wave propagation in fracture systems
NASA Astrophysics Data System (ADS)
Yi, Weidong
The geometric features and physical characteristics of fractures in rock masses are often considered major factors controlling the production of oil and gas. Therefore, it is important to detect fractures in oil and gas reservoirs. Of the various geophysical methods, seismic methods are particularly attractive for fracture detection and imaging because of the sensitivity of elastic waves to the mechanical compliance associated with fractures. Based on the effects of fracture on the velocities and amplitudes of seismic waves, several studies have shown the potential for using seismic tomography and vertical seismic profiling (VSP) techniques to characterize fracture systems in reservoirs. In this thesis, seismic wave propagation through a fracture system is numerically investigated by the finite-difference method. When seismic waves propagate in a medium with single fractures of infinite and finite length, the head wave and the dispersive interface waves (symmetric and antisymmetric modes) along the fracture are strongly excited by the explosion source if the seismic source is moved close to the fracture with low stiffness. In a fracture waveguide, fracture channel waves are supported by the waveguide, even in the absence of a velocity contrast between the fracture waveguide and surrounding host rock. The particular modes generated strongly depend on the polarization of the seismic source. When the seismic source is vertically (horizontally) polarized, antisymmetric (symmetric) modes are excited. In addition, if the thickness of the fracture waveguide increases, a complex particle motion of the fracture channel waves develops because the fracture channel waves partly couple with the interface waves along the fractures. For seismic wave propagation through a multi-fracture system consisting of equally spaced fractures, both an explicit fracture model and an equivalent transversely isotropic (TI) medium model were used to model the fracture system. In comparison to
Effects of Fast Simple Numerical Calculation Training on Neural Systems
Takeuchi, Hikaru; Nagase, Tomomi; Taki, Yasuyuki; Sassa, Yuko; Hashizume, Hiroshi; Nouchi, Rui; Kawashima, Ryuta
2016-01-01
Cognitive training, including fast simple numerical calculation (FSNC), has been shown to improve performance on untrained processing speed and executive function tasks in the elderly. However, the effects of FSNC training on cognitive functions in the young and on neural mechanisms remain unknown. We investigated the effects of 1-week intensive FSNC training on cognitive function, regional gray matter volume (rGMV), and regional cerebral blood flow at rest (resting rCBF) in healthy young adults. FSNC training was associated with improvements in performance on simple processing speed, speeded executive functioning, and simple and complex arithmetic tasks. FSNC training was associated with a reduction in rGMV and an increase in resting rCBF in the frontopolar areas and a weak but widespread increase in resting rCBF in an anatomical cluster in the posterior region. These results provide direct evidence that FSNC training alone can improve performance on processing speed and executive function tasks as well as plasticity of brain structures and perfusion. Our results also indicate that changes in neural systems in the frontopolar areas may underlie these cognitive improvements. PMID:26881117
Numeric Modeling of Valley Networks and Drainage Systems on Mars
NASA Astrophysics Data System (ADS)
Vidal, A.
2006-12-01
Valley networks observed on Mars are often invoked to support the historical presence of water on the surface of Mars. There is a need for quantification of these networks and the drainage processes associated with them. Numerical modeling of these streams and drainage basins within a GIS environment allows for rapid assessment of hydrologic surface processes. In this study, several areas of valley networks which had been previously mapped visually using Viking, MOC, and MOLA datasets were re-examined using numeric processes and tools available in ArcGIS. Specifically, stream length and drainage density were quantified using the MOLA gridded DEM and ArcGIS tools. This process is significantly faster than the visual identification and delineation techniques used in the past. The project sought to test whether or not computer-assisted techniques were comparable in accuracy and precision to previous studies using visual techniques. To do this, two quadrangles previously visually mapped by Carr (1995) and Hynek and Phillips (2003) were analyzed. Total valley network length at the first site was found to be 18,300 km, compared to previous estimates of 1,308 km (Carr) and 11,100 km (Hynek and Phillips). Drainage density was calculated to be 0.0605/km, compared to previous estimates of 0.0076/km (Carr) and 0.065/km (Hynek and Phillips). The highest stream order found was 5th, compared to 3rd (Carr) and 6th (Hynek and Phillips). In the second quadrangle, total valley network length was measured at 4,010 km, compared to 453 km and 3,496 km. The drainage density was calculated to be 0.068/km, compared to 0.011/km and 0.082/km. The highest stream order found was 4th, compared to 2nd and 5th. Results were very similar to those using visual interpretation of MOC shaded relief by Hynek and Phillips. A difference in stream order, however, suggests that the computer-aided technique may not connect systems that visually have been connected. Still, automated results offer an
A numerical investigation of a thermodielectric power generation system
NASA Astrophysics Data System (ADS)
Sklar, Akiva A.
consists of four processes; the first process is a charging process, during which an electric field is applied to a thermodielectric material, causing it to acquire electrical charge on its surface (this process is analogous to the isentropic compression process of a Brayton cycle). The second process is a heating process in which the temperature of the dielectric material is increased via heat transfer from an external source. During this process, the thermodielectric material is forced to eject a portion of its surface charge because its charge storing capability decreases as the temperature increases; the ejected charge is intended for capture by external circuitry connected to the thermodielectric material, where it can be routed to an electrochemical storage device or an electromechanical device requiring high voltage direct current. The third process is a discharging process, during which the applied electric field is reduced to its initial strength (analogous to the isentropic expansion process of a Brayton cycle). The final process is a cooling process in which the temperature of the dielectric material is decreased via heat transfer from an external source, returning it to its initial temperature. Previously, predicting the performance of a thermodielectric power generator was hindered by a poor understanding of the material's thermodynamic properties and the effect unsteady heat transfer losses have on system performance. In order to improve predictive capabilities in this study, a thermodielectric equation of state was developed that relates the strength of the applied electric field, the amount of surface charge stored by the thermodielectric material, and its temperature. This state equation was then used to derive expressions for the material's thermodynamic states (internal energy, entropy), which were subsequently used to determine the optimum material properties for power generation. Next, a numerical simulation code was developed to determine the heat
A numerical investigation of a thermodielectric power generation system
NASA Astrophysics Data System (ADS)
Sklar, Akiva A.
consists of four processes; the first process is a charging process, during which an electric field is applied to a thermodielectric material, causing it to acquire electrical charge on its surface (this process is analogous to the isentropic compression process of a Brayton cycle). The second process is a heating process in which the temperature of the dielectric material is increased via heat transfer from an external source. During this process, the thermodielectric material is forced to eject a portion of its surface charge because its charge storing capability decreases as the temperature increases; the ejected charge is intended for capture by external circuitry connected to the thermodielectric material, where it can be routed to an electrochemical storage device or an electromechanical device requiring high voltage direct current. The third process is a discharging process, during which the applied electric field is reduced to its initial strength (analogous to the isentropic expansion process of a Brayton cycle). The final process is a cooling process in which the temperature of the dielectric material is decreased via heat transfer from an external source, returning it to its initial temperature. Previously, predicting the performance of a thermodielectric power generator was hindered by a poor understanding of the material's thermodynamic properties and the effect unsteady heat transfer losses have on system performance. In order to improve predictive capabilities in this study, a thermodielectric equation of state was developed that relates the strength of the applied electric field, the amount of surface charge stored by the thermodielectric material, and its temperature. This state equation was then used to derive expressions for the material's thermodynamic states (internal energy, entropy), which were subsequently used to determine the optimum material properties for power generation. Next, a numerical simulation code was developed to determine the heat
Numerical Simulations of Quantum Many-body Systems
Scalapino, Douglas J. Sugar, Robert L.
1998-04-20
The goals of our DOE work were to develop numerical tools in order to (1) determine the actual phase of particular many-electron models and (2) to understand the underlying mechanisms responsible for the observed phases. Over the years, DOE funds provided support for a number of graduate students and postdoctoral fellows who have gone on to continue and extend this effort. Looking back, they were more successful in determining the types of correlations that developed in particular models and less successful in establishing the underlying mechanisms. For example, they found clear evidence for antiferromagnetism, d{sub x{sup 3}-y{sup 2}}-pairing correlations, and stripes in various t-t{prime}-J and Hubbard models. Here, the stripes consisted of 1/2-filled domain walls of holes separated by {pi}-phase shifted antiferromagnetic regions. They found that a next-near-neighbor hopping t{prime} with t{prime}/t > 0 suppressed the stripes and favored the d{sub x{sup 3}-y{sup 2}}-pairing correlations. They studied a model of a CuO, 2-leg ladder and found that d{sub x{sup 3}-y{sup 2}} correlations formed when the system was doped with either electrons or holes. Another example that they studied was a two-dimensional spin 1/2 easy plane model with a near-neighbor exchange J and a four-site ring exchange K. In this J-K model, as K/J is increased, one moves from XY order to stripe order and to Ising antiferromagnetic order. They are still exploring the unusual transition between the Xy and striped phase. The key feature that we found was that strongly-correlated, many-electron systems are 'delicately balanced' between different possible phases. They also believe that their work provides strong support in favor of Anderson's suggestion that the Hubbard model contains the basic physics of the cuprates. That is, it exhibits antiferromagnetism, d{sub x{sup 3}-y{sup 2}}-pairing correlations, and stripes as the half-filled model is doped with holes. They were not as successful in
A numerical model of combustion in gasless pyrotechnic systems
Boddington, T.; Cottrell, A.; Laye, P.G.
1989-04-01
A simple numerical model has been developed for the propagation of a combustion wave through a gasless pyrotechnic mixture. A pseudo one-dimensional approach has been adopted in which an allowance for heat loss has been made by the inclusion of a simple Newtonian heat transfer term. Implementation requires a knowledge of the thermal and kinetic properties of the pyrotechnic mixture. The model reproduces the observed trends in burning velocity and predicts conditions leading to combustion failure.
Numerical simulation of nonlinear dynamical systems driven by commutative noise
Carbonell, F. Biscay, R.J.; Jimenez, J.C.; Cruz, H. de la
2007-10-01
The local linearization (LL) approach has become an effective technique for the numerical integration of ordinary, random and stochastic differential equations. One of the reasons for this success is that the LL method achieves a convenient trade-off between numerical stability and computational cost. Besides, the LL method reproduces well the dynamics of nonlinear equations for which other classical methods fail. However, in the stochastic case, most of the reported works has been focused in Stochastic Differential Equations (SDE) driven by additive noise. This limits the applicability of the LL method since there is a number of interesting dynamics observed in equations with multiplicative noise. On the other hand, recent results show that commutative noise SDEs can be transformed into a random differential equation (RDE) by means of a random diffeomorfism (conjugacy). This paper takes advantages of such conjugacy property and the LL approach for defining a LL scheme for SDEs driven by commutative noise. The performance of the proposed method is illustrated by means of numerical simulations.
Numerical Methods of Computational Electromagnetics for Complex Inhomogeneous Systems
Cai, Wei
2014-05-15
Understanding electromagnetic phenomena is the key in many scientific investigation and engineering designs such as solar cell designs, studying biological ion channels for diseases, and creating clean fusion energies, among other things. The objectives of the project are to develop high order numerical methods to simulate evanescent electromagnetic waves occurring in plasmon solar cells and biological ion-channels, where local field enhancement within random media in the former and long range electrostatic interactions in the latter are of major challenges for accurate and efficient numerical computations. We have accomplished these objectives by developing high order numerical methods for solving Maxwell equations such as high order finite element basis for discontinuous Galerkin methods, well-conditioned Nedelec edge element method, divergence free finite element basis for MHD, and fast integral equation methods for layered media. These methods can be used to model the complex local field enhancement in plasmon solar cells. On the other hand, to treat long range electrostatic interaction in ion channels, we have developed image charge based method for a hybrid model in combining atomistic electrostatics and continuum Poisson-Boltzmann electrostatics. Such a hybrid model will speed up the molecular dynamics simulation of transport in biological ion-channels.
Field Study and Numerical Simulation of Sub Slab Ventilation Systems
Bonnefous, Y.C.; Gadgil, A.J.; Fisk, W.J.; Prill, R.J.; Nematollahi, A.R.
1992-05-01
The effectiveness of the technique of subslab ventilation (SSV) for limiting radon entry into basements was investigated through complementary experimentation and numerical modeling. Subslab pressure fields resulting from SSV were measured in six well-characterized basements, each with a different combination of soil and aggregate permeability. The relationship between air velocity and pressure gradient was measured in the laboratory for the three types of aggregate installed beneath the basement slabs. A new numerical model of SSV was developed and verified with the field data. This model simulates non-Darcy flow in the aggregate. We demonstrate that non-Darcy effects significantly impact SSV performance. Field data and numerical simulations indicate that increasing the aggregate permeability within the investigated range of 2 x 10{sup -8} m{sup 2} to 3 x 10{sup -7} m{sup 2} substantially improves the extension of the subslab pressure field due to SSV operation. Sealing of cracks in the slab and excavation of a small pit where the SSV pipe penetrates the slab also dramatically improve this pressure field extension. Our findings are consistent with the results of prior field studies; however, the studies reported here have improved our understanding of factors affecting SSV performance. The dependence of SSV performance on the relevant parameters are currently under investigation with the model.
NASA Astrophysics Data System (ADS)
Fasteen, Jodi I.
Alternate numeration systems are common in preservice teacher (PST) mathematics curricula, but there is limited research on how to leverage alternate systems to promote the development of mathematical knowledge for teaching. I analyzed the role of alternate numeration systems in three ways. I conducted a thematic analysis of current PST textbooks to consider the role of alternate numeration systems in written curricula. I conducted a teaching experiment to analyze PSTs' mathematical activity as they engaged with a base five task sequence to reinvent an algorithm for multiplication. And I introduced problematizing mathematical contexts as a design heuristic, situating this within the design theory of Realistic Mathematics Education. I found that alternate numeration systems can be leveraged to create opportunities for PSTs to (a) engage in guided reinvention of an algorithm, (b) improve understanding of base ten by comparing it to other numeration systems, and (c) reflect on their learning experience and the learning experiences of children.
Numerical simulation and wave extraction of binary black hole system
NASA Astrophysics Data System (ADS)
Imbiriba, Breno Cesar De Oliveira
In the first part of this work, we apply finite difference methods, specially mesh refinement techniques, in order to numerically evolve a single black hole, which is represented by the puncture initial data. We use standard second order finite differences, and the second order Iterated Crank-Nicholson integrator. We observe that, in order to obtain a second order accurate evolution we must impose second order accurate interface conditions at the refinement boundaries. We test our evolution with both the geodesic and the 1+log slicing conditions, and observe the expected results. We conclude that our mesh refinement technique generates convergent evolutions, and the puncture method behaves very well with it. The second part of this work deals with a modification of the hybrid "Lazarus" method for wave extraction. This method is divided in three parts: an early evolution, a set of transformations to produce perturbations over a Kerr background from the numerical data, and Teukolsky evolution. By using our evolution code (with mesh refinement) and gauges (1+log, gamma-driver, shifting-shift), we deviate from the original Lazarus approach. We used an independent implementation of the Lazarus transformations, validating the original results, and of the Teukolsky equation. We obtained results similar to the original Lazarus, both on the waveforms as well as on the negative results at later times. For instance, strong pulses that contaminate some gauge transformations, which may be explained in part by the propagating gauge modes of the 1+log slicing. Increasing the accuracy of the initial black hole evolution we seem to obtain better final results for the Kerr test case. Because of the gauge problems, we develop an approximated embedding method which approximates location of the numerical slice into the Kerr spacetime. This method is much less sensitive to the gauge perturbations. Given the difficulties of the Lazarus procedure, we decide to use the Lazarus method as a
Automated Testcase Generation for Numerical Support Functions in Embedded Systems
NASA Technical Reports Server (NTRS)
Schumann, Johann; Schnieder, Stefan-Alexander
2014-01-01
We present a tool for the automatic generation of test stimuli for small numerical support functions, e.g., code for trigonometric functions, quaternions, filters, or table lookup. Our tool is based on KLEE to produce a set of test stimuli for full path coverage. We use a method of iterative deepening over abstractions to deal with floating-point values. During actual testing the stimuli exercise the code against a reference implementation. We illustrate our approach with results of experiments with low-level trigonometric functions, interpolation routines, and mathematical support functions from an open source UAS autopilot.
Numerical Modeling of Unsteady Thermofluid Dynamics in Cryogenic Systems
NASA Technical Reports Server (NTRS)
Majumdar, Alok
2003-01-01
A finite volume based network analysis procedure has been applied to model unsteady flow without and with heat transfer. Liquid has been modeled as compressible fluid where the compressibility factor is computed from the equation of state for a real fluid. The modeling approach recognizes that the pressure oscillation is linked with the variation of the compressibility factor; therefore, the speed of sound does not explicitly appear in the governing equations. The numerical results of chilldown process also suggest that the flow and heat transfer are strongly coupled. This is evident by observing that the mass flow rate during 90-second chilldown process increases by factor of ten.
ERIC Educational Resources Information Center
Kapes, Jerome T.; Greenwood, Katy L.
The OCR Guidelines (Vocational Education Programs Guidelines for Eliminating Discrimination and Denial of Service on the Basis of Race, Color, National Origin, Sex and Handicap) are not the result of new legislation, but are new regulations for Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504…
ERIC Educational Resources Information Center
Hennefer, April; Sowder, Kristina; Pemberton, Cynthia Lee A.; Easterly, Debra M.
During the 2001-02 academic year, Idaho State University engaged a nationwide study to investigate the prevalence of dance and cheerleading programs among National Collegiate Athletic Association (NCAA) D-I schools. The goal of the study was to build a case for Office for Civil Rights (OCR) and NCAA sport recognition and designation. The study…
NASA Technical Reports Server (NTRS)
Reed, John A.; Afjeh, Abdollah A.; Lewandowski, Henry; Homer, Patrick T.; Schlichting, Richard D.
1996-01-01
The NASA Numerical Propulsion System Simulation (NPSS) project is exploring the use of computer simulation to facilitate the design of new jet engines. Several key issues raised in this research are being examined in an NPSS-related research project: zooming, monitoring and control, and support for heterogeneity. The design of a simulation executive that addresses each of these issues is described. In this work, the strategy of zooming, which allows codes that model at different levels of fidelity to be integrated within a single simulation, is applied to the fan component of a turbofan propulsion system. A prototype monitoring and control system has been designed for this simulation to support experimentation with expert system techniques for active control of the simulation. An interconnection system provides a transparent means of connecting the heterogeneous systems that comprise the prototype.
An Evaluation of PC-Based Optical Character Recognition Systems.
ERIC Educational Resources Information Center
Schreier, E. M.; Uslan, M. M.
1991-01-01
The review examines six personal computer-based optical character recognition (OCR) systems designed for use by blind and visually impaired people. Considered are OCR components and terms, documentation, scanning and reading, command structure, conversion, unique features, accuracy of recognition, scanning time, speed, and cost. (DB)
ERIC Educational Resources Information Center
Hyde, Daniel C.; Spelke, Elizabeth S.
2011-01-01
Behavioral research suggests that two cognitive systems are at the foundations of numerical thinking: one for representing 1-3 objects in parallel and one for representing and comparing large, approximate numerical magnitudes. We tested for dissociable neural signatures of these systems in preverbal infants by recording event-related potentials…
Numerical investigation of smart base isolation system employing MR elastomer
NASA Astrophysics Data System (ADS)
Usman, M.; Sung, S. H.; Jang, D. D.; Jung, H. J.; Koo, J. H.
2009-02-01
This paper evaluates the dynamic performance of a newly proposed smart base isolation system employing Magneto-Rheological Elastomers (MREs). MREs belong to a class of smart materials whose elastic modulus or stiffness can be adjusted by varying the magnitude of the magnetic field. The base isolation systems are considered as one of the most effective devices for vibration reduction of civil engineering structures in the event of earthquakes. The proposed base isolation system strives to enhance the performance of the conventional base-isolation system by using controllable MREs. To validate the effectiveness of the MRE-based isolation system, an extensive simulation study has been performed using a five degree-of-freedom structure under several historical earthquake excitations. The results show that the proposed system outperformed the conventional system in reducing the responses of the structure in all the seismic excitations considered in the study.
Optimizing OCR accuracy for bi-tonal, noisy scans of degraded Arabic documents
NASA Astrophysics Data System (ADS)
Herceg, Paul; Huyck, Benjamin; Johnson, Christopher; Van Guilder, Linda; Kundu, Amlan
2005-05-01
Acquiring foreign language from degraded hardcopy documents is of interest to military and border control applications. Bi-tonal image scans are desirable because file size is small. However, the nature of hardcopy degradations and the scanner or image enhancement software capabilities used directly affect the quality of the captured image and the extent of language acquisition. We applied a collection of manual treatments to hardcopy Arabic documents to develop a corpus of bi-tonal images. We then used this corpus in an exploratory study to derive conclusions about how bi-tonal images could be enhanced. This paper discusses the manually degraded Arabic document corpus, the image enhancement study, and the significant optical character recognition (OCR) improvements obtained with simple scanner driver adjustments.
75 FR 18841 - Office for Civil Rights; Privacy Act of 1974, Amended System of Records
Federal Register 2010, 2011, 2012, 2013, 2014
2010-04-13
...),'' System No. 09-90-0052, published at 67 FR 57011, September 6, 2002. First, we propose to add a new... INFORMATION: The system of records (i.e., PIMS) described in the OCR's Privacy Act notice, 67 FR 57011 (Sept... Improvement Act of 2005, and altered to add two new routine uses in OCR's Privacy Act notice at 72 FR...
Numerical modeling of pendulum dampers in torsional systems
Johnston, P.R.; Shusto, L.M.
1986-01-01
Centrifugal pendulum-design dampers are utilized in torsional systems to reduce the vibration amplitude at certain objectionable torsional speeds. The damper is tuned by proper design of its mass, dimensions, and position on a carrier disk, which is rigidly attached to the torsional system. The effects of the pendulum damper on the response of the torsional system may be included by modifying the structural model to include a separate damper element representing each order of the pendulum damper. The stiffness and mass matrices for a damper element are dependent upon the order of vibration being dampened, the mass, and the geometry of the damper. A general form of the mass and stiffness equations for a simple centrifugal pendulum damper are derived from first principles using Lagrange's equations of motion. The analysis of torsional systems with pendulum dampers utilizing the mass and stiffness properties developed is included in the program SHAMS. SHAMS calculates the steady-state response of a system of springs and masses to harmonic loads using modal superposition. The response of a crankshaft system with and without the pendulum dampers are included as a case study.
Numerical Modeling of a Shallow Borehole Thermal Energy Storage System
NASA Astrophysics Data System (ADS)
Catolico, N.; Ge, S.; Lu, N.; McCartney, J. S.
2014-12-01
Borehole thermal energy storage (BTES) combined with solar thermal energy harvesting is an economic technological system to garner and store energy as well as an environmentally-sustainable alternative for the heating of buildings. The first community-scale BTES system in North America was installed in 2007 in the Drake Landing Solar Community (DLSC), about 35 miles south of Calgary, Canada. The BTES system involves direct circulation of water heated from solar thermal panels in the summer into a storage tank, after which it is circulate within an array of 144 closed-loop geothermal heat exchangers having a depth of 35 m and a spacing of 2.5 m. In the winter the circulation direction is reversed to supply heat to houses. Data collection over a six year period indicates that this system can supply more than 90% of the winter heating energy needs for 52 houses in the community. One major challenge facing the BTES system technology is the relatively low annual efficiency, i.e., the ratio of energy input and output is in the range of 15% to 40% for the system in Drake Landing. To better understand the working principles of BTES and to improve BTES performance for future applications at larger scales, a three-dimensional transient coupled fluid and heat transfer model is established using TOUGH2. The time-dependent injection temperatures and circulation rate measured over the six years of monitoring are used as model input. The simulations are calibrated using soil temperature data measured at different locations over time. The time-dependent temperature distributions within the borehole region agree well with the measured temperatures for soil with an intrinsic permeability of 10e-19 m2, an apparent thermal conductivity of 2.03 W/m°C, and a volumetric heat capacity of 2.31 MJ/m-3°C. The calibrated model serves as the basis for a sensitivity analysis of soil and operational parameters on BTES system efficiency preformed with TOUGH2. Preliminary results suggest 1) BTES
Numerical simulations of thermal conductivity in dissipative two-dimensional Yukawa systems.
Khrustalyov, Yu V; Vaulina, O S
2012-04-01
Numerical data on the heat transfer constants in two-dimensional Yukawa systems were obtained. Numerical study of the thermal conductivity and diffusivity was carried out for the equilibrium systems with parameters close to conditions of laboratory experiments with dusty plasma. For calculations of heat transfer constants the Green-Kubo formulas were used. The influence of dissipation (friction) on the heat transfer processes in nonideal systems was investigated. The approximation of the coefficient of thermal conductivity is proposed. Comparison of the obtained results to the existing experimental and numerical data is discussed. PMID:22680584
Numerical analysis of nonlinear properties of rail fastening systems
NASA Astrophysics Data System (ADS)
Liu, Y.; Luo, Y.; Yin, H. P.
2014-10-01
Higher demand on vibration isolation of track structure in nowadays leads to a trend of lower stiffness of rail fastening system accompanied with larger deformation of its rubber component. Nonlinear properties of rubber material under large deformation thus should be taken into account. Uniaxial tension, uniaxial compression and planar tension experiments of a rubber material were carried out to defined mathematical material models by using Abaqus. Accuracy of the material model and model coefficients were supported by good agreement between measured and simulated results. A shear type and a bonded compressed type of rail fastening system are designed and produced with the same rubber material. Quasi-static experiment of these two rail fastening systems were performed and simulated as well. Predictions of the preload dependent nonlinear properties of the two different rail fastening systems by Abaqus were found to be in good agreement with experiments. Nonlinearities of the two specimens, due both to the intrinsic rubber material properties and the geometric characteristics, were well analyzed and explained. This is believed to contribute to product designing and geometrical optimization with rubber component under general or local large deformation.
Differential Emergence of Representational Systems: Drawings, Letters, and Numerals
ERIC Educational Resources Information Center
Yamagata, Kyoko
2007-01-01
This study investigated the process by which the representational activity and knowledge about drawing and letter and number writing emerge in children 21-46 months old. The results revealed that representational activities developed with age through several phases. Beginning at age 2, children produced different marks for different systems, but…
NASA Astrophysics Data System (ADS)
Imada, Masatoshi; Kashima, Tsuyoshi
2000-09-01
A numerical algorithm for studying strongly correlated electron systems is proposed. The groundstate wavefunction is projected out after a numerical renormalization procedure in the path integral formalism. The wavefunction is expressed from the optimized linear combination of retained states in the truncated Hilbert space with a numerically chosen basis. This algorithm does not suffer from the negative sign problem and can be applied to any type of Hamiltonian in any dimension. The efficiency is tested in examples of the Hubbard model where the basis of Slater determinants is numerically optimized. We show results on fast convergence and accuracy achieved with a small number of retained states.
Numerical study on thermal load of laser reflecting focusing system
NASA Astrophysics Data System (ADS)
Cheng, Fu Qiang; Hong, Yan Ji
2013-05-01
In laser thrusters, the reflectors of the focusing system work under high-intensity laser radiation. The material choice of the reflectors is quite important due to thermal load raised by laser absorption. Meanwhile the endurance of heavy thermal load should be attributed to the metallic reflectors with low laser energy absorption ratio. Based on two-dimension heat conduction equation and several approximations, this study investigates the melting time and thermal deformation characteristics for three kind of metallic materials that are of high heat specific heat, high conductivity and high melting point, and so are some alloys. Calculated through Finite Differential Method, the results show that, as for the twice reflecting focusing system, the thermal load is quite remarkable for the both reflectors and is more serious for the second one, while different materials present distinct thermal endurance performance. For the materials under study, the beryllium mirrors featuring higher specific heat could endure longer laser radiation and may prolong the work time. Moreover, if the reflecting mirror is required to work under high laser radiation for longer time, the aid of cooling system maybe indispensable.
Numerical modeling of Saturn's satellites and ring system
NASA Astrophysics Data System (ADS)
Chambers, Lindsey Starr
2008-10-01
Saturn's extensive ring and satellite system make it one of the most fascinating bodies in the solar system. Space missions like Cassini have revolutionized our understanding of the Saturn system; however, many issues remain unresolved. This dissertation explores three projects related to unanswered questions about Saturn's rings and satellites. Published moment of inertia data provide weak constraints on the interior structure of Saturn's mid-sized icy satellites. Giant impact basins and their associated antipodal terrains provide an alternate way to study the satellites' interior structures. I used hydrodynamical impact simulations to assess the amount of damage caused to the antipodal terrain of Tethys, Mimas and Rhea. Results vary somewhat from one satellite to another due to differences in the sizes of the satellites and impactors. I find that antipodal disruption depends more on core radius than core density, suggesting that core geometry may express a surface signature in global impacts on partially differentiated targets. The flux of meteoroids impacting Saturn's rings is not well known; this has important implications for the age of the rings. One way to better constrain this flux is to observe flashes caused by hypervelocity impacts between meteoroids and ring particles. 400 hours of ultraviolet Cassini observations were initially allotted to search for impact flashes. I used a hydrodynamics code to simulate such impacts and developed a radiative transfer model to study the resulting impact plumes. I find that the impact plumes last for only 10- 4 s, and radiation from the impact plumes is emitted in the visible rather than ultraviolet. The albedos of the ring particles are not well constrained. This directly relates to the composition of the rings and has implications for their age. I developed a radiative transfer code to model photon interactions with ring particles. This code includes the volume filling factor and demonstrates that inclusion of
Lifeflow vad: design and numerical modeling of magnetic bearing system.
Kailasan, Arunvel; Untaroiu, Alexandrina; Jiang, Wei; Wood, Houston G; Allaire, Paul E
2012-01-01
The non-contact and lubrication free support of magnetic bearings make them ideal to support rotating machines. One area of application of magnetic bearings is in the design of the mechanical heart pumps. The LifeFlow heart pump developed by the University of Virginia is one such heart pump which uses active and passive magnetic bearings to support the impeller. The design and controls of such bearings can be quite challenging. One of the major difficulties that one may encounter in designing the controller is to get accurate values of the control parameters such as bias flux, radial and axial stiffness values, forces, etc. In order to obtain these parameters accurately, a three dimensional finite element analysis of the magnetic bearings is crucial. This paper covers the analysis of the magnetic bearing system used in the LifeFlow Heart pump. The main purpose of the analysis was to provide accurate values of air gap flux, forces, radial and axial stiffness in order to design a robust and optimized controller for the bearings. As a result of the analysis, these parameters have been determined and the motor is being redesigned with a smaller footprint to achieve higher efficiency. PMID:22846286
One Language, Two Number-Word Systems and Many Problems: Numerical Cognition in the Czech Language
ERIC Educational Resources Information Center
Pixner, S.; Zuber, J.; Hermanova, V.; Kaufmann, L.; Nuerk, H.-C.; Moeller, K.
2011-01-01
Comparing numerical performance between different languages does not only mean comparing different number-word systems, but also implies a comparison of differences regarding culture or educational systems. The Czech language provides the remarkable opportunity to disentangle this confound as there exist two different number-word systems within…
Neural computing for numeric-to-symbolic conversion in control systems
NASA Technical Reports Server (NTRS)
Passino, Kevin M.; Sartori, Michael A.; Antsaklis, Panos J.
1989-01-01
A type of neural network, the multilayer perceptron, is used to classify numeric data and assign appropriate symbols to various classes. This numeric-to-symbolic conversion results in a type of information extraction, which is similar to what is called data reduction in pattern recognition. The use of the neural network as a numeric-to-symbolic converter is introduced, its application in autonomous control is discussed, and several applications are studied. The perceptron is used as a numeric-to-symbolic converter for a discrete-event system controller supervising a continuous variable dynamic system. It is also shown how the perceptron can implement fault trees, which provide useful information (alarms) in a biological system and information for failure diagnosis and control purposes in an aircraft example.
Heat transfer coefficients in two-dimensional Yukawa systems (numerical simulations)
NASA Astrophysics Data System (ADS)
Khrustalyov, Yu. V.; Vaulina, O. S.
2013-05-01
New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data.
Numerical solution of flow problems using body-fitted coordinate systems
NASA Technical Reports Server (NTRS)
Thompson, J. F.
1980-01-01
The paper deals with numerically generated boundary-fitted coordinate systems. This procedure eliminates the shape of the boundaries as a complicating factor and allows the flow about arbitrary boundaries to be treated essentially as easily as that about simple boundaries. The technique of boundary-fitted coordinate systems is based on a method of automatic numerical generation of a general curvilinear coordinate system having a coordinate line coincident with each boundary of a general multiconnected region involving any number of arbitrarily shaped boundaries. Once the curvilinear coordinate system is generated, any partial differential system of interest may be solved on the coordinate system by transforming the equations and solving the resulting system in finite-difference approximation on the rectangular transformed plane. Attention is given to the types of boundary-fitted coordinate systems, coordinate system control, operation of the coordinate codes, solution of partial differential equations, application to free-surface flow, and other applications of interest.
Experimental And Numerical Modelling Of The Priming Operation In Spacecraft Propulsion Systems
NASA Astrophysics Data System (ADS)
Lema, Marcos; Pinho, Jorge; Steelant, Johan; Lopez-Pena, Fernando; Rambaud, Patrick
2011-05-01
The present study investigates experimentally and numerically the fluid hammer phenomenon in a confined environment, representing the priming operation of spacecraft propulsion systems. For the experimental approach, a new facility has been designed at the von Karman Institute, which can reproduce all the physical phenomena taking place in the propellant lines during a priming process. The simplified test procedure allows the recording of the pressure evolution of the liquid front with a fast response pressure transducer. The numerical approach is done with the numerical codes used by the European Space Agency (ESA) to support the propulsion systems design, i.e. EcosimPro/ESPSS and CFD-ACE+, simulating the experimental configuration both with 1D and 3D approaches. Comparing the numerical results with the experimental measurements indicates that the modelling of two-phase, two-component transient flows is a requirement for a proper simulation.
NASA Astrophysics Data System (ADS)
Balashov, V. A.; Savenkov, E. B.
2015-10-01
The applicability of numerical algorithms based on a quasi-hydrodynamic system of equations for computing viscous heat-conducting compressible gas flows at Mach numbers M = 10-2-10-1 is studied numerically. The numerical algorithm is briefly described, and the results obtained for a number of two- and three-dimensional test problems are presented and compared with earlier numerical data.
NASA Technical Reports Server (NTRS)
Bernstein, Ira B.; Brookshaw, Leigh; Fox, Peter A.
1992-01-01
The present numerical method for accurate and efficient solution of systems of linear equations proceeds by numerically developing a set of basis solutions characterized by slowly varying dependent variables. The solutions thus obtained are shown to have a computational overhead largely independent of the small size of the scale length which characterizes the solutions; in many cases, the technique obviates series solutions near singular points, and its known sources of error can be easily controlled without a substantial increase in computational time.
Journees 2010: New challenges for reference systems and numerical standards in astronomy
NASA Astrophysics Data System (ADS)
Capitaine, Nicole
2011-10-01
The Journees 2010 "Systemes de reference spatio-temporels", with the sub-title "New challenges for reference systems and numerical standards in astronomy", were organized from 20 to 22 September 2010 at Paris Observatory and Ecole Normale Superieure in Paris, France. The scientific programme was focused on the issues related to the recent developments and new challenges in astronomical space and time reference systems and their relativistic aspects, astrometric catalogs, Earth orientation, astronomical constants and numerical standards, planetary ephemerides and modern astrometry. There have been presentations and discussions related to the IAU Division 1 commissions and IAU Working Group "Numerical Standards for Fundamental astronomy" (NSFA); there has been a special session for presenting the latest developments in the solar system ephemerides and comparing details in those ephemerides.
Free vibrations of beam-mass-spring systems: analytical analysis with numerical confirmation
NASA Astrophysics Data System (ADS)
Darabi, Mohammad A.; Kazemirad, Siavash; Ghayesh, Mergen H.
2012-04-01
Free vibrations of a beam-mass-spring system with different boundary conditions are analyzed both analytically and numerically. In the analytical analysis, the system is divided into three subsystems and the effects of the spring and the point mass are considered as internal boundary conditions between any two neighboring subsystems. The partial differential equations governing the motion of the subsystems and internal boundary conditions are then solved using the method of separation of variables. In the numerical analysis, the whole system is considered as a single system and the effects of the spring and point mass are introduced using the Dirac delta function. The Galerkin method is then employed to discretize the equation of motion and the resulting set of ordinary differential equations are solved via eigenvalue analysis. Analytical and numerical results are shown to be in very good agreement.
NASA Astrophysics Data System (ADS)
Degtyarev, Alexander; Khramushin, Vasily
2016-02-01
The paper deals with the computer implementation of direct computational experiments in fluid mechanics, constructed on the basis of the approach developed by the authors. The proposed approach allows the use of explicit numerical scheme, which is an important condition for increasing the effciency of the algorithms developed by numerical procedures with natural parallelism. The paper examines the main objects and operations that let you manage computational experiments and monitor the status of the computation process. Special attention is given to a) realization of tensor representations of numerical schemes for direct simulation; b) realization of representation of large particles of a continuous medium motion in two coordinate systems (global and mobile); c) computing operations in the projections of coordinate systems, direct and inverse transformation in these systems. Particular attention is paid to the use of hardware and software of modern computer systems.
NASA Astrophysics Data System (ADS)
Tsai, C. S.; Su, H. C.; Chiang, T. C.
2014-03-01
Current structural analysis software programs offer few if any applicable device-specific hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system (MFPS) with numerous sliding interfaces. Based on the concept of subsystems, an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is proposed. The aim is to simulate the characteristics of sliding motions for an MFPS isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding stages. An MFPS with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the first represents the concave sliding interfaces above the slider, and the second represents those below the slider. The equivalent series system for the entire system is then obtained by connecting those for each subsystem in series. The equivalent series system is validated by comparing numerical results for an MFPS with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and Constantinou. Furthermore, these numerical results demonstrate that an MFPS isolator with numerous concave sliding interfaces, which may have any number of sliding interfaces, is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.
Maier, O.A.
1984-01-01
Some needs addressed concerning computer-aided design and computer-aided manufacture include: data base definition rules and three-dimensional data bases; inclusion of concise dimensional, finishing, and other data in textual or attribute form; usable solid modeling capability; better toolpath control; programmable language section of system capable of addressing the whole system data structure; and broader numerical control macro capability. (LEW)
Online Numeric Data-Base Systems: A Resource for the Traditional Library.
ERIC Educational Resources Information Center
Adams, Margaret O'Neill
1982-01-01
Analysis of one component of library reference service--online numeric database systems for time-series data--reviews tradition of reference service and ways in which computer technology has enhanced provision of library services. Experiences with Kentucky Economic Information System (KEIS) are described. Examples of KEIS and 30 references are…
ERIC Educational Resources Information Center
Zhang, Jie; Lu, Xiaofei
2013-01-01
This study examined variability in Chinese as a Foreign Language (CFL) learners' development of the Chinese numeral classifier system from a dynamic systems approach. Our data consisted of a longitudinal corpus of 657 essays written by CFL learners at lower and higher intermediate levels and a corpus of 100 essays written by native speakers (NSs)…
Supporting Indigenous Students' Understanding of the Numeration System of Their First Language
ERIC Educational Resources Information Center
Cortina, Jose Luis
2013-01-01
Results from a project conducted in Mexico are discussed, in which a group of 17 indigenous teachers analyzed the numeration systems of their first language. The main goal of the project is to develop resources that help teachers in supporting students' understanding of the systems. In the first phase of the project, the central organizing ideas…
Numerical Propulsion System Simulation (NPSS): An Award Winning Propulsion System Simulation Tool
NASA Technical Reports Server (NTRS)
Stauber, Laurel J.; Naiman, Cynthia G.
2002-01-01
The Numerical Propulsion System Simulation (NPSS) is a full propulsion system simulation tool used by aerospace engineers to predict and analyze the aerothermodynamic behavior of commercial jet aircraft, military applications, and space transportation. The NPSS framework was developed to support aerospace, but other applications are already leveraging the initial capabilities, such as aviation safety, ground-based power, and alternative energy conversion devices such as fuel cells. By using the framework and developing the necessary components, future applications that NPSS could support include nuclear power, water treatment, biomedicine, chemical processing, and marine propulsion. NPSS will dramatically reduce the time, effort, and expense necessary to design and test jet engines. It accomplishes that by generating sophisticated computer simulations of an aerospace object or system, thus enabling engineers to "test" various design options without having to conduct costly, time-consuming real-life tests. The ultimate goal of NPSS is to create a numerical "test cell" that enables engineers to create complete engine simulations overnight on cost-effective computing platforms. Using NPSS, engine designers will be able to analyze different parts of the engine simultaneously, perform different types of analysis simultaneously (e.g., aerodynamic and structural), and perform analysis in a more efficient and less costly manner. NPSS will cut the development time of a new engine in half, from 10 years to 5 years. And NPSS will have a similar effect on the cost of development: new jet engines will cost about a billion dollars to develop rather than two billion. NPSS is also being applied to the development of space transportation technologies, and it is expected that similar efficiencies and cost savings will result. Advancements of NPSS in fiscal year 2001 included enhancing the NPSS Developer's Kit to easily integrate external components of varying fidelities, providing
Maes, G.J.
1993-10-01
This document contains the proceedings of the 62nd Interagency Manufacturing Operations Group (IMOG) Numerical Systems Group. Included are the minutes of the 61st meeting and the agenda for the 62nd meeting. Presentations at the meeting are provided in the appendices to this document. Presentations were: 1992 NSG Annual Report to IMOG Steering Committee; Charter for the IMOG Numerical Systems Group; Y-12 Coordinate Measuring Machine Training Project; IBH NC Controller; Automatically Programmed Metrology Update; Certification of Anvil-5000 for Production Use at the Y-12 Plant; Accord Project; Sandia National Laboratories {open_quotes}Accord{close_quotes}; Demo/Anvil Tool Path Generation 5-Axis; Demo/Video Machine/Robot Animation Dynamics; Demo/Certification of Anvil Tool Path Generation; Tour of the M-60 Inspection Machine; Distributed Numerical Control Certification; Spline Usage Method; Y-12 NC Engineering Status; and Y-12 Manufacturing CAD Systems.
Supporting indigenous students' understanding of the numeration system of their first language
NASA Astrophysics Data System (ADS)
Cortina, José Luis
2013-03-01
Results from a project conducted in Mexico are discussed, in which a group of 17 indigenous teachers analyzed the numeration systems of their first language. The main goal of the project is to develop resources that help teachers in supporting students' understanding of the systems. In the first phase of the project, the central organizing ideas of 14 numeration systems were specified. Each system belonged to a different Mesoamerican language. Three aspects of the systems were identified that would have to be accounted for in instructional design. They include using 20 as a multiplicative base. Examples are presented of the instructional resources that indigenous teachers could use to help their students understand the quantitative rationales of the systems.
A numerical model of an intensive care ventilator-humidifier system.
Drew, T; Vardy, A; Tarnow-Mordi, W; Lerski, R
1996-04-01
Current intensive care ventilator-humidifier systems neither monitor nor adequately control inspired gas humidity. Problems of low delivered humidity and condensation within ventilator circuitry are commonly encountered. To help to address these problems, a numerical model of a complete ventilator-humidifier-patient intensive care system has been developed. The model, based on a finite difference technique, can predict pressures, flow-rates, temperatures and relative humidities at discrete points throughout the system. A comparison of numerical predictions and measurements in a real system is reported. A strong qualitative agreement is demonstrated in all cases studied, and a good quantitative agreement is obtained in most cases. It is concluded that such models could be used to assess methods of controlling ventilator-humidifier systems to prevent the occurrence of condensation. Similar models could be developed for other medical gas delivery systems. PMID:8718951
Shaking table test and numerical analysis of offshore wind turbine tower systems controlled by TLCD
NASA Astrophysics Data System (ADS)
Chen, Jianbing; Liu, Youkun; Bai, Xueyuan
2015-03-01
A wind turbine system equipped with a tuned liquid column damper (TLCD) is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response-equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs. Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane's equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades' rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.
NASA Technical Reports Server (NTRS)
Rosenbaum, J. S.
1976-01-01
If a system of ordinary differential equations represents a property conserving system that can be expressed linearly (e.g., conservation of mass), it is then desirable that the numerical integration method used conserve the same quantity. It is shown that both linear multistep methods and Runge-Kutta methods are 'conservative' and that Newton-type methods used to solve the implicit equations preserve the inherent conservation of the numerical method. It is further shown that a method used by several authors is not conservative.
A numerical scheme for optimal transition paths of stochastic chemical kinetic systems
NASA Astrophysics Data System (ADS)
Liu, Di
2008-10-01
We present a new framework for finding the optimal transition paths of metastable stochastic chemical kinetic systems with large system size. The optimal transition paths are identified to be the most probable paths according to the Large Deviation Theory of stochastic processes. Dynamical equations for the optimal transition paths are derived using the variational principle. A modified Minimum Action Method (MAM) is proposed as a numerical scheme to solve the optimal transition paths. Applications to Gene Regulatory Networks such as the toggle switch model and the Lactose Operon Model in Escherichia coli are presented as numerical examples.
A numerical method to study the dynamics of capillary fluid systems
NASA Astrophysics Data System (ADS)
Herrada, M. A.; Montanero, J. M.
2016-02-01
We propose a numerical approach to study both the nonlinear dynamics and linear stability of capillary fluid systems. In the nonlinear analysis, the time-dependent fluid region is mapped onto a fixed numerical domain through a coordinate transformation. The hydrodynamic equations are spatially discretized with the Chebyshev spectral collocation technique, while an implicit time advancement is performed using second-order backward finite differences. The resulting algebraic equations are solved with the iterative Newton-Raphson technique. The most novel aspect of the method is the fact that the elements of the Jacobian of the discretized system of equations are symbolic functions calculated before running the simulation. These functions are evaluated numerically in the Newton-Raphson iterations to find the solution at each time step, which reduces considerably the computing time. Besides, this numerical procedure can be easily adapted to solve the eigenvalue problem which determines the linear global modes of the capillary system. Therefore, both the nonlinear dynamics and the linear stability analysis can be conducted with essentially the same algorithm. We validate this numerical approach by studying the dynamics of a liquid bridge close to its minimum volume stability limit. The results are virtually the same as those obtained with other methods. The proposed approach proves to be much more computationally efficient than those other methods. Finally, we show the versatility of the method by calculating the linear global modes of a gravitational jet.
One language, two number-word systems and many problems: numerical cognition in the Czech language.
Pixner, S; Zuber, J; Heřmanová, V; Kaufmann, L; Nuerk, H-C; Moeller, K
2011-01-01
Comparing numerical performance between different languages does not only mean comparing different number-word systems, but also implies a comparison of differences regarding culture or educational systems. The Czech language provides the remarkable opportunity to disentangle this confound as there exist two different number-word systems within the same language: for instance, "25" can be either coded in non-inverted order "dvadsetpät" [twenty-five] or in inverted order "pätadvadset" [five-and-twenty]. To investigate the influence of the number-word system on basic numerical processing within one culture, 7-year-old Czech-speaking children had to perform a transcoding task (i.e., writing Arabic numbers to dictation) in both number-word systems. The observed error pattern clearly indicated that the structure of the number-word system determined transcoding performance reliably: In the inverted number-word system about half of all errors were inversion-related. In contrast, hardly any inversion-related errors occurred in the non-inverted number-word system. We conclude that the development of numerical cognition does not only depend on cultural or educational differences, but is indeed related to the structure and transparency of a given number-word system. PMID:21763104
New developments in the numerical solution of differential/algebraic systems
Petzold, L.R.
1987-04-01
In this paper we survey some recent developments in the numerical solution of nonlinear differential/algebraic equation (DAE) systems of the form 0 = F(t,y,y'), where the initial values of y are known and par. deltaF/par. deltay' may be singular. These systems arise in the simulation of electrical networks, as well as in many other applications. DAE systems include standard form ODEs as a special case, but they also include problems which are in many ways quite different from ODEs. We examine the classification of DAE systems according to the degree of singularity of the system, and present some results on the analytical structure of these systems. We give convergence results for backward differentiation formulas applied to DAEs and examine some of the software issues involved in the numerical solution of DAEs. One-step methods are potentially advantageous for solving DAE systems with frequent discontinuities. However, recent results indicate that there is a reduction in the order of accuracy of many implicit Runge-Kutta methods even for simple DAE systems. We examine the current state of solving DAE systems by implicit Runge-Kutta methods. Finding a consistent set of initial conditions is often a problem for DAEs arising in applications. We explore some numerical methods for obtaining a consistent set of initial conditions. 21 refs.
NASA Technical Reports Server (NTRS)
Lan, C. Edward; Ge, Fuying
1989-01-01
Control system design for general nonlinear flight dynamic models is considered through numerical simulation. The design is accomplished through a numerical optimizer coupled with analysis of flight dynamic equations. The general flight dynamic equations are numerically integrated and dynamic characteristics are then identified from the dynamic response. The design variables are determined iteratively by the optimizer to optimize a prescribed objective function which is related to desired dynamic characteristics. Generality of the method allows nonlinear effects to aerodynamics and dynamic coupling to be considered in the design process. To demonstrate the method, nonlinear simulation models for an F-5A and an F-16 configurations are used to design dampers to satisfy specifications on flying qualities and control systems to prevent departure. The results indicate that the present method is simple in formulation and effective in satisfying the design objectives.
Chen, YaoHan; Su, ChungHwei; Tseng, JoMing; Li, WunJie
2015-01-01
The water spray systems are effective protection systems in the confined or unconfined spaces to avoid the damage to building structures since the high temperature when fires occur. NFPA 15 and 502 have suggested respectively that the factories or vehicle tunnels install water spray systems to protect the machinery and structures. This study discussed the cooling effect of water spray systems in experimental and numerical analyses. The actual combustion of woods were compared with the numerical simulations. The results showed that although the flame continued, the cooling effects by water spraying process within 120 seconds were obvious. The results also indicated that the simulation results of the fifth version Fire Dynamics Simulator (FDS) overestimated the space temperature before water spraying in the case of the same water spray system. PMID:25723519
Chen, YaoHan; Su, ChungHwei; Tseng, JoMing; Li, WunJie
2015-01-01
The water spray systems are effective protection systems in the confined or unconfined spaces to avoid the damage to building structures since the high temperature when fires occur. NFPA 15 and 502 have suggested respectively that the factories or vehicle tunnels install water spray systems to protect the machinery and structures. This study discussed the cooling effect of water spray systems in experimental and numerical analyses. The actual combustion of woods were compared with the numerical simulations. The results showed that although the flame continued, the cooling effects by water spraying process within 120 seconds were obvious. The results also indicated that the simulation results of the fifth version Fire Dynamics Simulator (FDS) overestimated the space temperature before water spraying in the case of the same water spray system. PMID:25723519
A numerical model for thermal energy storage systems utilising encapsulated phase change materials
NASA Astrophysics Data System (ADS)
Jacob, Rhys; Saman, Wasim; Bruno, Frank
2016-05-01
In an effort to reduce the cost of thermal energy storage for concentrated solar power plants, a thermocline storage concept was investigated. Two systems were investigated being a sensible-only and an encapsulated phase change system. Both systems have the potential to reduce the storage tank volume and/or reduce the cost of the filler material, thereby reducing the cost of the system when compared to current two-tank molten salt systems. The objective of the current paper is to create a numerical model capable of designing and simulating the aforementioned thermocline storage concepts in the open source programming language known as Python. The results of the current study are compared to previous numerical results and are found to be in good agreement.
NASA Technical Reports Server (NTRS)
Korte, John J.
1990-01-01
A numerical simulation of the actuation system for the propulsion control valve (PCV) of the NASA Langley Aircraft Landing Dynamics Facility was developed during the preliminary design of the PCV and used throughout the entire project. The simulation is based on a predictive model of the PCV which is used to evaluate and design the actuation system. The PCV controls a 1.7 million-pound thrust water jet used in propelling a 108,000-pound test carriage. The PCV can open and close in 0.300 second and deliver over 9,000 gallons of water per sec at pressures up to 3150 psi. The numerical simulation results are used to predict transient performance and valve opening characteristics, specify the hydraulic control system, define transient loadings on components, and evaluate failure modes. The mathematical model used for numerically simulating the mechanical fluid power system is described, and numerical results are demonstrated for a typical opening and closing cycle of the PCV. A summary is then given on how the model is used in the design process.
Numerical Studies of Collective Phenomena in Two-Dimensional Electron and Cold Atom Systems
Rezayi, Edward
2013-07-25
Numerical calculations were carried out to investigate a number of outstanding questions in both two-dimensional electron and cold atom systems. These projects aimed to increase our understanding of the properties of and prospects for non-Abelian states in quantum Hall matter.
RELAP5 two-phase fluid model and numerical scheme for economic LWR system simulation
Ransom, V.H.; Wagner, R.J.; Trapp, J.A.
1981-01-01
The RELAP5 two-phase fluid model and the associated numerical scheme are summarized. The experience accrued in development of a fast running light water reactor system transient analysis code is reviewed and example of the code application are given.
A Framework for Evaluating Regional-Scale Numerical Photochemical Modeling Systems
This paper discusses the need for critically evaluating regional-scale (~ 200-2000 km) three dimensional numerical photochemical air quality modeling systems to establish a model's credibility in simulating the spatio-temporal features embedded in the observations. Because of li...
Numerical modelling of interrogation systems for optical fibre Bragg grating sensors
NASA Astrophysics Data System (ADS)
Oswald, Daniel; Richardson, Steven; Wild, Graham
2011-12-01
There are a number of interrogation methods that can be used in optical Fibre Bragg Grating (FBG) sensing system. For very high frequency signals interrogating the sensor signal from an FBG is limited to two intensiometric methods, edge filter detection and power detection. In edge filter detection, a broadband light source illuminates an FBG, the reflected spectrum is then passed through a spectral filter. In power detection, a narrowband light source with a wavelength corresponding to the 3dB point of the FBG is filtered by the FBG itself. Both methods convert the spectral shift of the FBG into intensity signals. These two categories each have a number of variations, all with different performance characteristics. In this work we present a numerical model for all of these interrogation systems. The numerical model is based on previous analytical modelling, which could only be utilised for perfect Gaussian profiles. However, interrogation systems can make use of non Gaussian shaped filters, or sources. The numerical modelling enables the different variations to be compared using identical component performance, showing the relative strengths and weakness of the systems in terms of useful parameters, including, signal-to-noise ratio, sensitivity, and dynamic resolution. The two different detection methods can also be compared side-by-side using the same FBG. Since the model is numerical, it enables real spectral data to be used for the various components (FBG, light source, filters). This has the added advantage of increasing the accuracy and usefulness of the model, over previous analytical work.
Kagawa, Yuki; Miyahara, Hirotaka; Ota, Yuri; Tsuneda, Satoshi
2016-01-01
Estimating the oxygen consumption rates (OCRs) of mammalian cells in hypoxic environments is essential for designing and developing a three-dimensional (3-D) cell culture system. However, OCR measurements under hypoxic conditions are infrequently reported in the literature. Here, we developed a system for measuring OCRs at low oxygen levels. The system injects nitrogen gas into the environment and measures the oxygen concentration by an optical oxygen microsensor that consumes no oxygen. The developed system was applied to HepG2 cells in static culture. Specifically, we measured the spatial profiles of the local dissolved oxygen concentration in the medium, then estimated the OCRs of the cells. The OCRs, and also the pericellular oxygen concentrations, decreased nonlinearly as the oxygen partial pressure in the environment decreased from 19% to 1%. The OCRs also depended on the culture period and the matrix used for coating the dish surface. Using this system, we can precisely estimate the OCRs of various cell types under environments that mimic 3-D culture conditions, contributing crucial data for an efficient 3-D culture system design. PMID:26558344
Research on numerical control system based on S3C2410 and MCX314AL
NASA Astrophysics Data System (ADS)
Ren, Qiang; Jiang, Tingbiao
2008-10-01
With the rapid development of micro-computer technology, embedded system, CNC technology and integrated circuits, numerical control system with powerful functions can be realized by several high-speed CPU chips and RISC (Reduced Instruction Set Computing) chips which have small size and strong stability. In addition, the real-time operating system also makes the attainment of embedded system possible. Developing the NC system based on embedded technology can overcome some shortcomings of common PC-based CNC system, such as the waste of resources, low control precision, low frequency and low integration. This paper discusses a hardware platform of ENC (Embedded Numerical Control) system based on embedded processor chip ARM (Advanced RISC Machines)-S3C2410 and DSP (Digital Signal Processor)-MCX314AL and introduces the process of developing ENC system software. Finally write the MCX314AL's driver under the embedded Linux operating system. The embedded Linux operating system can deal with multitask well moreover satisfy the real-time and reliability of movement control. NC system has the advantages of best using resources and compact system with embedded technology. It provides a wealth of functions and superior performance with a lower cost. It can be sure that ENC is the direction of the future development.
Numerical test for hyperbolicity of chaotic dynamics in time-delay systems
NASA Astrophysics Data System (ADS)
Kuptsov, Pavel V.; Kuznetsov, Sergey P.
2016-07-01
We develop a numerical test of hyperbolicity of chaotic dynamics in time-delay systems. The test is based on the angle criterion and includes computation of angle distributions between expanding, contracting, and neutral manifolds of trajectories on the attractor. Three examples are tested. For two of them, previously predicted hyperbolicity is confirmed. The third one provides an example of a time-delay system with nonhyperbolic chaos.
Numerical test for hyperbolicity of chaotic dynamics in time-delay systems.
Kuptsov, Pavel V; Kuznetsov, Sergey P
2016-07-01
We develop a numerical test of hyperbolicity of chaotic dynamics in time-delay systems. The test is based on the angle criterion and includes computation of angle distributions between expanding, contracting, and neutral manifolds of trajectories on the attractor. Three examples are tested. For two of them, previously predicted hyperbolicity is confirmed. The third one provides an example of a time-delay system with nonhyperbolic chaos. PMID:27575062
A new method of modelling and numerical simulation of nonlinear dynamical systems
Colosi, T.; Codreanu, S.
1996-06-01
This work presents the most significant aspects of an original method of modelling and numerical simulation of nonlinear (linear) dynamical systems (1) it assures the local-iterative linearization (LIL) of nonlinear (linear) differential equations and transforms them, in the close proximity of a pivot moment, into algebraic equations. The use of this method is illustrated in the study of a particular nonlinear dynamical systems. The conclusions highlight the advantages of the proposed procedure. {copyright} {ital 1996 American Institute of Physics.}
Numerical Simulation of the Oscillations in a Mixer: An Internal Aeroacoustic Feedback System
NASA Technical Reports Server (NTRS)
Jorgenson, Philip C. E.; Loh, Ching Y.
2004-01-01
The space-time conservation element and solution element method is employed to numerically study the acoustic feedback system in a high temperature, high speed wind tunnel mixer. The computation captures the self-sustained feedback loop between reflecting Mach waves and the shear layer. This feedback loop results in violent instabilities that are suspected of causing damage to some tunnel components. The computed frequency is in good agreement with the available experimental data. The physical phenomena are explained based on the numerical results.
Numerical methods for systems of conservation laws of mixed type using flux splitting
NASA Technical Reports Server (NTRS)
Shu, Chi-Wang
1990-01-01
The essentially non-oscillatory (ENO) finite difference scheme is applied to systems of conservation laws of mixed hyperbolic-elliptic type. A flux splitting, with the corresponding Jacobi matrices having real and positive/negative eigenvalues, is used. The hyperbolic ENO operator is applied separately. The scheme is numerically tested on the van der Waals equation in fluid dynamics. Convergence was observed with good resolution to weak solutions for various Riemann problems, which are then numerically checked to be admissible as the viscosity-capillarity limits. The interesting phenomena of the shrinking of elliptic regions if they are present in the initial conditions were also observed.
Wetzstein, M.; Nelson, Andrew F.; Naab, T.; Burkert, A.
2009-10-01
We present a numerical code for simulating the evolution of astrophysical systems using particles to represent the underlying fluid flow. The code is written in Fortran 95 and is designed to be versatile, flexible, and extensible, with modular options that can be selected either at the time the code is compiled or at run time through a text input file. We include a number of general purpose modules describing a variety of physical processes commonly required in the astrophysical community and we expect that the effort required to integrate additional or alternate modules into the code will be small. In its simplest form the code can evolve the dynamical trajectories of a set of particles in two or three dimensions using a module which implements either a Leapfrog or Runge-Kutta-Fehlberg integrator, selected by the user at compile time. The user may choose to allow the integrator to evolve the system using individual time steps for each particle or with a single, global time step for all. Particles may interact gravitationally as N-body particles, and all or any subset may also interact hydrodynamically, using the smoothed particle hydrodynamic (SPH) method by selecting the SPH module. A third particle species can be included with a module to model massive point particles which may accrete nearby SPH or N-body particles. Such particles may be used to model, e.g., stars in a molecular cloud. Free boundary conditions are implemented by default, and a module may be selected to include periodic boundary conditions. We use a binary 'Press' tree to organize particles for rapid access in gravity and SPH calculations. Modules implementing an interface with special purpose 'GRAPE' hardware may also be selected to accelerate the gravity calculations. If available, forces obtained from the GRAPE coprocessors may be transparently substituted for those obtained from the tree, or both tree and GRAPE may be used as a combination GRAPE/tree code. The code may be run without
Numerical Analysis of Combined Well and Open-Closed Loops Geothermal (CWG) Systems
NASA Astrophysics Data System (ADS)
Park, Yu-Chul
2016-04-01
Open-loop geothermal heat pump (GHP) system and closed-loop heat pump systems have been used in Korea to reduce emission of greenhouse gases such as carbon dioxide (CO2). The GHP systems have the pros and cons, for example, the open-loop GHP system is good energy-efficient and the closed-loop GHP system requires minimum maintenance costs. The open-loop GHP system can be used practically only with large amount of groundwater supply. The closed-loop GHP system can be used with high costs of initial installation. The performance and efficiency of the GHP system depend on the characteristics of the GHP system itself in addition to the geologic conditions. To overcome the cons of open-loop or closed-loop GHP system, the combined well and open-closed loops geothermal (CWG) system was designed. The open-loop GHP system is surrounded with closed-loop GHP systems in the CWG system. The geothermal energy in closed-loop GHP systems is supplied by the groundwater pumped by the open-loop GHP system. In this study, 2 different types of the CWG systems (small aperture hybrid CWG system and large aperture CWG system) are estimated using numerical simulation models in the aspect of energy efficiency. This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No.20153030111120).
Numerical modeling of an enhanced very early time electromagnetic (VETEM) prototype system
Cui, T.J.; Chew, W.C.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.; Abraham, J.D.
2000-01-01
In this paper, two numerical models are presented to simulate an enhanced very early time electromagnetic (VETEM) prototype system, which is used for buried-object detection and environmental problems. Usually, the VETEM system contains a transmitting loop antenna and a receiving loop antenna, which run on a lossy ground to detect buried objects. In the first numerical model, the loop antennas are accurately analyzed using the Method of Moments (MoM) for wire antennas above or buried in lossy ground. Then, Conjugate Gradient (CG) methods, with the use of the fast Fourier transform (FFT) or MoM, are applied to investigate the scattering from buried objects. Reflected and scattered magnetic fields are evaluated at the receiving loop to calculate the output electric current. However, the working frequency for the VETEM system is usually low and, hence, two magnetic dipoles are used to replace the transmitter and receiver in the second numerical model. Comparing these two models, the second one is simple, but only valid for low frequency or small loops, while the first modeling is more general. In this paper, all computations are performed in the frequency domain, and the FFT is used to obtain the time-domain responses. Numerical examples show that simulation results from these two models fit very well when the frequency ranges from 10 kHz to 10 MHz, and both results are close to the measured data.
Numerical analysis of impact effect on mechanical behavior of strong guardrail system
NASA Astrophysics Data System (ADS)
Shen, X.; Guo, L.; Yang, L.; Du, X.; Cao, P.
2008-02-01
The purpose of this study is to estimate the crashworthiness of a guardrail system, and to optimize the relative vertical distance between centroid of vehicle and mounting height of W-beam. Abaqus/Explicit 6.5 software is used to simulate the dynamic response of the post and W-beam guardrail systems under vehicular impacts. Numerical results of maximum displacement of vehicles during dynamic contact between vehicle and guardrail system with various given masses of vehicles are obtained. Energy-absorbing properties of the guardrail system are studied for different values of centroid height. Influence of frictional coefficient between ground surface and vehicles is also investigated.
A numerical study for design of depth, pitch and roll control system of a towed vehicle
Koterayama, W.; Yamaguchi, S.; Nakamura, M.; Moriyama, A.; Akamatsu, T.
1994-12-31
A towed vehicle system, FLYING FISH, is under development for use in making chemical and physical measurements which enable the authors to obtain spacially continuous and real time data in an ocean mixed layer. The heave, pitch and roll of FLYING FISH are controlled by a main wing and horizontal tail wings which permit its stable attitudes and assure accurate measurements. The numerical simulation of motions was carried out to design the optimal control system of this towed vehicle system and the results gave the data for the design of the mechanical parts of the control system.
Xing, Lu; Cullin, James; Spitler, Jeffery; Im, Piljae; Fisher, Daniel
2011-01-01
A new type of ground heat exchanger that utilizes the excavation often made for basements or foundations has been proposed as an alternative to conventional ground heat exchangers. This article describes a numerical model that can be used to size these foundation heat exchanger (FHX) systems. The numerical model is a two-dimensional finite-volume model that considers a wide variety of factors, such as soil freezing and evapotranspiration. The FHX numerical model is validated with one year of experimental data collected at an experimental house located near Oak Ridge, Tennessee. The model shows good agreement with the experimental data-heat pump entering fluid temperatures typically within 1 C (1.8 F) - with minor discrepancies due to approximations, such as constant moisture content throughout the year, uniform evapotranspiration over the seasons, and lack of ground shading in the model.
A practical numerical scheme for the ternary Cahn-Hilliard system with a logarithmic free energy
NASA Astrophysics Data System (ADS)
Jeong, Darae; Kim, Junseok
2016-01-01
We consider a practically stable finite difference method for the ternary Cahn-Hilliard system with a logarithmic free energy modeling the phase separation of a three-component mixture. The numerical scheme is based on a linear unconditionally gradient stable scheme by Eyre and is solved by an efficient and accurate multigrid method. The logarithmic function has a singularity at zero. To remove the singularity, we regularize the function near zero by using a quadratic polynomial approximation. We perform a convergence test, a linear stability analysis, and a robustness test of the ternary Cahn-Hilliard equation. We observe that our numerical solutions are convergent, consistent with the exact solutions of linear stability analysis, and stable with practically large enough time steps. Using the proposed numerical scheme, we also study the temporal evolution of morphology patterns during phase separation in one-, two-, and three-dimensional spaces.
NASA Technical Reports Server (NTRS)
Sutton, M. A.; Davis, P. K.
1976-01-01
Numerical solutions of the governing equations of motion of a liquid squeeze film damped forced vibration system were carried out to examine the feasibility of using a liquid squeeze film to cushion and protect large structures, such as buildings, located in areas of high seismic activity. The mathematical model used was that for a single degree of freedom squeeze film damped spring mass system. The input disturbance was simulated by curve fitting actual seismic data with an eleventh order Lagranging polynomial technique. Only the normal component of the seismic input was considered. The nonlinear, nonhomogeneous governing differential equation of motion was solved numerically to determine the transmissibility over a wide range of physical parameters using a fourth-order Runge-Kutta technique. It is determined that a liquid squeeze film used as a damping agent in a spring-mass system can significantly reduce the response amplitude for a seismic input disturbance.
NASA Astrophysics Data System (ADS)
Dong, Xing-Jian; Meng, Guang; Peng, Juan-Chun
2006-11-01
The aim of this study is to investigate the efficiency of a system identification technique known as observer/Kalman filter identification (OKID) technique in the numerical simulation and experimental study of active vibration control of piezoelectric smart structures. Based on the structure responses determined by finite element method, an explicit state space model of the equivalent linear system is developed by employing OKID approach. The linear quadratic Gaussian (LQG) algorithm is employed for controller design. The control law is then incorporated into the ANSYS finite element model to perform closed loop simulations. Therefore, the control law performance can be evaluated in the context of a finite element environment. Furthermore, a complete active vibration control system comprising the cantilever plate, the piezoelectric actuators, the accelerometers and the digital signal processor (DSP) board is set up to conduct the experimental investigation. A state space model characterizing the dynamics of the physical system is developed from experimental results using OKID approach for the purpose of control law design. The controller is then implemented by using a floating point TMS320VC33 DSP. Numerical examples by employing the proposed numerical simulation method, together with the experimental results obtained by using the active vibration control system, have demonstrated the validity and efficiency of OKID method in application of active vibration control of piezoelectric smart structures.
NASA Astrophysics Data System (ADS)
Brunetti, J.; Massi, F.; Saulot, A.; Renouf, M.; D`Ambrogio, W.
2015-06-01
Mechanical systems present several contact surfaces between deformable bodies. The contact interface can be either static (joints) or in sliding (active interfaces). The sliding interfaces can have several roles and according to their application they can be developed either for maximizing the friction coefficient and the energy dissipation (e.g. brakes) or rather to allow the relative displacement at joints with a maximum efficiency. In both cases the coupling between system and local contact dynamics can bring to system dynamics instabilities (e.g. brake squeal or squeaking of hip prostheses). This results in unstable vibrations of the system, induced by the oscillation of the contact forces. In the literature, a large number of works deal with such kind of instabilities and are mainly focused on applied problems such as brake squeal noise. This paper shows a more general numerical analysis of a simple system constituted by two bodies in sliding contact: a rigid cylinder rotating inside a deformable one. The parametrical Complex Eigenvalue Analysis and the transient numerical simulations show how the friction forces can give rise to in-plane dynamic instabilities due to the interaction between two system modes, even for such a simple system characterized by one deformable body. Results from transient simulations highlight the key role of realistic values of the material damping to have convergence of the model and, consequently, reliable physical results. To this aim an experimental estimation of the material damping has been carried out. Moreover, the simplicity of the system allows for a deeper analysis of the contact instability and a balance of the energy flux among friction, system vibrations and damping. The numerical results have been validated by comparison with experimental ones, obtained by a specific test bench developed to reproduce and analyze the contact friction instabilities.
NASA Technical Reports Server (NTRS)
Majumdar, Alok K.; LeClair, Andre C.; Hedayat, Ali
2016-01-01
This paper presents a numerical model of pressurization of a cryogenic propellant tank for the Integrated Vehicle Fluid (IVF) system using the Generalized Fluid System Simulation Program (GFSSP). The IVF propulsion system, being developed by United Launch Alliance, uses boiloff propellants to drive thrusters for the reaction control system as well as to run internal combustion engines to develop power and drive compressors to pressurize propellant tanks. NASA Marshall Space Flight Center (MSFC) has been running tests to verify the functioning of the IVF system using a flight tank. GFSSP, a finite volume based flow network analysis software developed at MSFC, has been used to develop an integrated model of the tank and the pressurization system. This paper presents an iterative algorithm for converging the interface boundary conditions between different component models of a large system model. The model results have been compared with test data.
NASA Technical Reports Server (NTRS)
Rosenbaum, J. S.
1971-01-01
Systems of ordinary differential equations in which the magnitudes of the eigenvalues (or time constants) vary greatly are commonly called stiff. Such systems of equations arise in nuclear reactor kinetics, the flow of chemically reacting gas, dynamics, control theory, circuit analysis and other fields. The research reported develops an A-stable numerical integration technique for solving stiff systems of ordinary differential equations. The method, which is called the generalized trapezoidal rule, is a modification of the trapezoidal rule. However, the method is computationally more efficient than the trapezoidal rule when the solution of the almost-discontinuous segments is being calculated.
Blue laser and high-numerical-aperture optical disk system for digital video recording (DVR)
NASA Astrophysics Data System (ADS)
van Houten, Henk
2001-02-01
Based on a blue diode laser (405 nm wavelength) and a two- element objective lens with a numerical aperture of 0.85, a third generation optical recording system has been developed that is able to record 22.5 GB on a single sided 12 cm diameter disc, at a user data rate of 50 Mb/s. The system is referred to by the technical name DVR for high definition Digital Video Recording. In this paper, we review the physical and the system concept, the phase change media, the optical pick up unit, and the drive implementation.
Simulation studies of the impact of advanced observing systems on numerical weather prediction
NASA Technical Reports Server (NTRS)
Atlas, R.; Kalnay, E.; Susskind, J.; Reuter, D.; Baker, W. E.; Halem, M.
1984-01-01
To study the potential impact of advanced passive sounders and lidar temperature, pressure, humidity, and wind observing systems on large-scale numerical weather prediction, a series of realistic simulation studies between the European Center for medium-range weather forecasts, the National Meteorological Center, and the Goddard Laboratory for Atmospheric Sciences is conducted. The project attempts to avoid the unrealistic character of earlier simulation studies. The previous simulation studies and real-data impact tests are reviewed and the design of the current simulation system is described. Consideration is given to the simulation of observations of space-based sounding systems.
Mapping sea ice leads with a coupled numeric/symbolic system
NASA Technical Reports Server (NTRS)
Key, J.; Schweiger, A. J.; Maslanik, J. A.
1990-01-01
A method is presented which facilitates the detection and delineation of leads with single-channel Landsat data by coupling numeric and symbolic procedures. The procedure consists of three steps: (1) using the dynamic threshold method, an image is mapped to a lead/no lead binary image; (2) the likelihood of fragments to be real leads is examined with a set of numeric rules; and (3) pairs of objects are examined geometrically and merged where possible. The processing ends when all fragments are merged and statistical characteristics are determined, and a map of valid lead objects are left which summarizes useful physical in the lead complexes. Direct implementation of domain knowledge and rapid prototyping are two benefits of the rule-based system. The approach is found to be more successfully applied to mid- and high-level processing, and the system can retrieve statistics about sea-ice leads as well as detect the leads.
Numerical analysis of composite systems by using interphase/interface models
NASA Astrophysics Data System (ADS)
Chaboche, J. L.; Girard, R.; Schaff, A.
1997-07-01
The paper considers two classes of approaches for the numerical analysis of composite systems: the first one discretizes the assumed interphase (between matrix and fibre) as volumic elements and uses material models that degenerate from Continuum Damage Mechanics. The second one introduces interface elements that relate non linearly the normal and tangential tractions to the corresponding displacement discontinuities, incorporating a progressive decohesion, following the lines of Needleman (1987) and Tvergaard (1990). The respective capabilities of these two approaches are discussed on the basis of some numerical results obtained for a unidirectional metal matrix composite system. When the models are consistently adjusted they are able to reproduce the same kind of results. The advantages of the second class of method is underlined and two new versions of interface models are proposed that guarantee the continuity and the monotonicity of the shear stiffness between the progressive decohesion phase and the subsequent contact/friction law that plays role under compressive shear after complete separation.
Winter, T.C.; Pfannkuch, H.O.
1984-01-01
The interaction of lakes and groundwater is controlled partly by the geologic framework through which the water flows. Two interrelated geometric factors of the groundwater system that affect flow are overall geometry of the system, and anisotropy of the porous media within the system. Numerical simulation analysis was made for variations in the coefficient of anisotropy for each of several lake and groundwater settings having different geometric configurations. These analyses indicate that, for a given geometric setting, as the anisotropy of geologic materials decreases seepage from a lake decreases and depth of the local groundwater flow system associated with the lake increases. Transformation of scale of groundwater systems that have anisotropic media to isotropic equivalents results in a change in the overall geometry. Because of the different slopes of the water table and lakebed resulting from the scale transformations, a series of numerical experiments were made for various geometric configurations for a given anisotropy. These analyses indicate that as thickness of the groundwater system decreases, relative depth of the local flow system increases and seepage from the lake decreases. ?? 1984.
Simulation studies of proposed observing systems and their impact on numerical weather prediction
NASA Technical Reports Server (NTRS)
Atlas, R.; Kalnay, E.; Susskind, J.; Baker, W. E.; Halem, M.
1984-01-01
A series of realistic simulation studies is being conducted as a cooperative effort between the European Centre for Medium Range Weather Forecasts (ECMWF), the National Meteorological Center (NMC), and the Goddard Laboratory for Atmospheric Sciences (GLAS) to provide a quantitative assessment of the potential impact of proposed observation systems on large scale numerical weather prediction. A special objective of this project is to avoid the unrealistic character of earlier simulation studies.
Experimental evidence, numerics, and theory of vibrational resonance in bistable systems.
Baltanás, J P; López, L; Blechman, I I; Landa, P S; Zaikin, A; Kurths, J; Sanjuán, M A F
2003-06-01
We consider an overdamped bistable oscillator subject to the action of a biharmonic force with very different frequencies, and study the response of the system when the parameters of the high-frequency force are varied. A resonantlike behavior is obtained when the amplitude or the frequency of this force is modified in an experiment performed by means of an analog circuit. This behavior, confirmed by numerical simulations, is explained on the basis of a theoretical approach. PMID:16241316
Numerical model for the flow within the tower of a tornado-type wind energy system
Ayad, S.S.
1981-11-01
A two-equation turbulence model is used to predict numerically the flow within the tower of a tornado-type wind energy system. Calculations are carried out for a tower in a uniform flow. Both cases of closed-bottom tower and simulated turbine flow with a variety of turbine-to-tower diameter ratios and turbine flow rates are considered. Calculated values of pressure for closed-bottom tower are compared with experimental values. 11 refs.
Large deviations in boundary-driven systems: Numerical evaluation and effective large-scale behavior
NASA Astrophysics Data System (ADS)
Bunin, Guy; Kafri, Yariv; Podolsky, Daniel
2012-07-01
We study rare events in systems of diffusive fields driven out of equilibrium by the boundaries. We present a numerical technique and use it to calculate the probabilities of rare events in one and two dimensions. Using this technique, we show that the probability density of a slowly varying configuration can be captured with a small number of long-wavelength modes. For a configuration which varies rapidly in space this description can be complemented by a local-equilibrium assumption.
Numerical study of the performance of tornado-type wind energy systems
Ayad, S.S.
1983-03-01
The tornado-type wind energy system was proposed to utilize the pressure drop created by an intens vortex in a tower. The tower serves as a low pressure exhaust for the turbine. The author carried out a numerical solution of the tower flow, using the two-equation (kappa-epsilon) turbulence model, for the small size system tested by Yen, with a 0.127-m- (5-in.-) diam tower standing in a uniform wind flow. A comparison of the results with the measured pressure values verified the model. In the present work the same numerical model is used for a system with a tower that is completely embedded in an atmospheric boundary layer. The results show, for a tower in a boundary layer of the one-seventh power-law profile, about a 28% reduction of the values of power coefficient from those for a tower in a uniform stream. Calculations for the performance of a system with different tower heights and the same tower and turbine diameters show a sharp decrease of power for H/D less than or equal to 0.5. Analysis of the tangential velocity shows that the vortex should be maintained up to heights /ZETA//D less than or equal to 0.9 to avoid the decrease in power extraction. Numerical predictions are made for systems with tower diameters between 0.5 and 8 m (1.64 and 26.24 ft) using the same system geometry and approach flow conditions. The results show that the scale effect is negligible for systems of 4-m tower diameter or larger.
Numerical Modeling of Cavitating Venturi: A Flow Control Element of Propulsion System
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Saxon, Jeff (Technical Monitor)
2002-01-01
In a propulsion system, the propellant flow and mixture ratio could be controlled either by variable area flow control valves or by passive flow control elements such as cavitating venturies. Cavitating venturies maintain constant propellant flowrate for fixed inlet conditions (pressure and temperature) and wide range of outlet pressures, thereby maintain constant, engine thrust and mixture ratio. The flowrate through the venturi reaches a constant value and becomes independent of outlet pressure when the pressure at throat becomes equal to vapor pressure. In order to develop a numerical model of propulsion system, it is necessary to model cavitating venturies in propellant feed systems. This paper presents a finite volume model of flow network of a cavitating venturi. The venturi was discretized into a number of control volumes and mass, momentum and energy conservation equations in each control volume are simultaneously solved to calculate one-dimensional pressure, density, and flowrate and temperature distribution. The numerical model predicts cavitations at the throat when outlet pressure was gradually reduced. Once cavitation starts, with further reduction of downstream pressure, no change in flowrate is found. The numerical predictions have been compared with test data and empirical equation based on Bernoulli's equation.
The generation and use of numerical shape models for irregular Solar System objects
NASA Technical Reports Server (NTRS)
Simonelli, Damon P.; Thomas, Peter C.; Carcich, Brian T.; Veverka, Joseph
1993-01-01
We describe a procedure that allows the efficient generation of numerical shape models for irregular Solar System objects, where a numerical model is simply a table of evenly spaced body-centered latitudes and longitudes and their associated radii. This modeling technique uses a combination of data from limbs, terminators, and control points, and produces shape models that have some important advantages over analytical shape models. Accurate numerical shape models make it feasible to study irregular objects with a wide range of standard scientific analysis techniques. These applications include the determination of moments of inertia and surface gravity, the mapping of surface locations and structural orientations, photometric measurement and analysis, the reprojection and mosaicking of digital images, and the generation of albedo maps. The capabilities of our modeling procedure are illustrated through the development of an accurate numerical shape model for Phobos and the production of a global, high-resolution, high-pass-filtered digital image mosaic of this Martian moon. Other irregular objects that have been modeled, or are being modeled, include the asteroid Gaspra and the satellites Deimos, Amalthea, Epimetheus, Janus, Hyperion, and Proteus.
NASA Astrophysics Data System (ADS)
Rivola, Alessandro; Troncossi, Marco
2014-10-01
The development of high-performance vehicle engines requires advanced investigations in order to provide engineers with proper analysis tools to optimize the system design. The elastodynamic behaviour of the engine powertrain may be critical at high velocities (when the flexibility of the system components can have a major role on the overall performance) with consequences on the valve timing and the transmission of dynamic loads. A thorough numerical/experimental investigation was performed on the timing system of a racing motorbike engine. The timing system included the geartrain, which transmits power from the crankshaft to the camshafts, and the valve train, formed by the camshafts and the cam-follower mechanisms for the valve actuation. An experimental campaign was designed and carried out with the purpose of inspecting the timing system behaviour for different velocities and different design parameters. A numerical model was developed in order to provide a simulation/analysis tool that permits the design optimization of the main system components. The present work focuses on the geartrain elastodynamic analysis, which is the main novelty of a long-lasting activity carried out by the authors in collaborations with Ducati Motor Holding S.p.a. (Bologna, Italy). The experimental campaign, the model development and validation, and some simulation results are reported and discussed.
Practical vision based degraded text recognition system
NASA Astrophysics Data System (ADS)
Mohammad, Khader; Agaian, Sos; Saleh, Hani
2011-02-01
Rapid growth and progress in the medical, industrial, security and technology fields means more and more consideration for the use of camera based optical character recognition (OCR) Applying OCR to scanned documents is quite mature, and there are many commercial and research products available on this topic. These products achieve acceptable recognition accuracy and reasonable processing times especially with trained software, and constrained text characteristics. Even though the application space for OCR is huge, it is quite challenging to design a single system that is capable of performing automatic OCR for text embedded in an image irrespective of the application. Challenges for OCR systems include; images are taken under natural real world conditions, Surface curvature, text orientation, font, size, lighting conditions, and noise. These and many other conditions make it extremely difficult to achieve reasonable character recognition. Performance for conventional OCR systems drops dramatically as the degradation level of the text image quality increases. In this paper, a new recognition method is proposed to recognize solid or dotted line degraded characters. The degraded text string is localized and segmented using a new algorithm. The new method was implemented and tested using a development framework system that is capable of performing OCR on camera captured images. The framework allows parameter tuning of the image-processing algorithm based on a training set of camera-captured text images. Novel methods were used for enhancement, text localization and the segmentation algorithm which enables building a custom system that is capable of performing automatic OCR which can be used for different applications. The developed framework system includes: new image enhancement, filtering, and segmentation techniques which enabled higher recognition accuracies, faster processing time, and lower energy consumption, compared with the best state of the art published
Stability analysis and numerical simulation of 1 prey - 2 predator system
NASA Astrophysics Data System (ADS)
Savitri, D.; Abadi
2015-03-01
In this paper, we study an ecological system that consists of 1 prey and 2 predators populations. The prey population grows logistically while Holling type II functional response is applied for both predators . The first predator preys on the prey and the second predator preys on the first one. The study starts with the stability analysis of critical points of the systems. Then, by using normal form and centre manifold method the information about other nontrivial solutions due to bifurcation including possible limit cycles appearance is obtained. The results are confirmed by numerical simulation using MatCont and biological interpretation of the results is also presented.
NASA Astrophysics Data System (ADS)
Calcagnile, Lucio M.; Galatolo, Stefano; Menconi, Giulia
2010-12-01
We numerically test the method of non-sequential recursive pair substitutions to estimate the entropy of an ergodic source. We compare its performance with other classical methods to estimate the entropy (empirical frequencies, return times, and Lyapunov exponent). We have considered as a benchmark for the methods several systems with different statistical properties: renewal processes, dynamical systems provided and not provided with a Markov partition, and slow or fast decay of correlations. Most experiments are supported by rigorous mathematical results, which are explained in the paper.
Numerical simulation of geodesic acoustic modes in a multi-ion system
Ye, Lei; Guo, Wenfeng; Xiao, Xiaotao; Wang, Shaojie
2013-07-15
Based on the semi-Lagrangian method, a δf drift kinetic continuum code incorporating magnetic flux coordinate was developed and applied to investigate the geodesic acoustic mode (GAM) oscillation in a multi-ion plasma system. This work proves clearly that the effective ion mass number affects the GAM in a multi-ion system. In this simulation, GAM frequency and damping rate are seen to vary with the proportion of impurity ions. The numerical result is consistent with the theoretical prediction in terms of both frequency and damping rate.
Zhang, Ellen Ziyi; Oh, Wang-Yuhl; Villiger, Martin L.; Chen, Liang; Bouma, Brett E.; Vakoc, Benjamin J.
2013-01-01
Polarization mode dispersion (PMD), which can be induced by circulators or even moderate lengths of optical fiber, is known to be a dominant source of instrumentation noise in fiber-based PS-OCT systems. In this paper we propose a novel PMD compensation method that measures system PMD using three fixed calibration signals, numerically corrects for these instrument effects and reconstructs an improved sample image. Using a frequency multiplexed PS-OFDI setup, we validate the proposed method by comparing birefringence noise in images of intralipid, muscle, and tendon with and without PMD compensation. PMID:23389009
NASA Technical Reports Server (NTRS)
Reed, John A.; Afjeh, Abdollah A.
1995-01-01
A major difficulty in designing aeropropulsion systems is that of identifying and understanding the interactions between the separate engine components and disciplines (e.g., fluid mechanics, structural mechanics, heat transfer, material properties, etc.). The traditional analysis approach is to decompose the system into separate components with the interaction between components being evaluated by the application of each of the single disciplines in a sequential manner. Here, one discipline uses information from the calculation of another discipline to determine the effects of component coupling. This approach, however, may not properly identify the consequences of these effects during the design phase, leaving the interactions to be discovered and evaluated during engine testing. This contributes to the time and cost of developing new propulsion systems as, typically, several design-build-test cycles are needed to fully identify multidisciplinary effects and reach the desired system performance. The alternative to sequential isolated component analysis is to use multidisciplinary coupling at a more fundamental level. This approach has been made more plausible due to recent advancements in computation simulation along with application of concurrent engineering concepts. Computer simulation systems designed to provide an environment which is capable of integrating the various disciplines into a single simulation system have been proposed and are currently being developed. One such system is being developed by the Numerical Propulsion System Simulation (NPSS) project. The NPSS project, being developed at the Interdisciplinary Technology Office at the NASA Lewis Research Center is a 'numerical test cell' designed to provide for comprehensive computational design and analysis of aerospace propulsion systems. It will provide multi-disciplinary analyses on a variety of computational platforms, and a user-interface consisting of expert systems, data base management and
NASA Astrophysics Data System (ADS)
Alfonso, Lester; Zamora, Jose; Cruz, Pedro
2015-04-01
The stochastic approach to coagulation considers the coalescence process going in a system of a finite number of particles enclosed in a finite volume. Within this approach, the full description of the system can be obtained from the solution of the multivariate master equation, which models the evolution of the probability distribution of the state vector for the number of particles of a given mass. Unfortunately, due to its complexity, only limited results were obtained for certain type of kernels and monodisperse initial conditions. In this work, a novel numerical algorithm for the solution of the multivariate master equation for stochastic coalescence that works for any type of kernels and initial conditions is introduced. The performance of the method was checked by comparing the numerically calculated particle mass spectrum with analytical solutions obtained for the constant and sum kernels, with an excellent correspondence between the analytical and numerical solutions. In order to increase the speedup of the algorithm, software parallelization techniques with OpenMP standard were used, along with an implementation in order to take advantage of new accelerator technologies. Simulations results show an important speedup of the parallelized algorithms. This study was funded by a grant from Consejo Nacional de Ciencia y Tecnologia de Mexico SEP-CONACYT CB-131879. The authors also thanks LUFAC® Computacion SA de CV for CPU time and all the support provided.
NASA Technical Reports Server (NTRS)
Przekwas, A. J.; Yang, H. Q.
1989-01-01
The capability of accurate nonlinear flow analysis of resonance systems is essential in many problems, including combustion instability. Classical numerical schemes are either too diffusive or too dispersive especially for transient problems. In the last few years, significant progress has been made in the numerical methods for flows with shocks. The objective was to assess advanced shock capturing schemes on transient flows. Several numerical schemes were tested including TVD, MUSCL, ENO, FCT, and Riemann Solver Godunov type schemes. A systematic assessment was performed on scalar transport, Burgers' and gas dynamic problems. Several shock capturing schemes are compared on fast transient resonant pipe flow problems. A system of 1-D nonlinear hyperbolic gas dynamics equations is solved to predict propagation of finite amplitude waves, the wave steepening, formation, propagation, and reflection of shocks for several hundred wave cycles. It is shown that high accuracy schemes can be used for direct, exact nonlinear analysis of combustion instability problems, preserving high harmonic energy content for long periods of time.
Numerical analysis of some supersonic viscous flows related to inlet and nozzle systems
NASA Technical Reports Server (NTRS)
Kim, Y.-N.; Buggeln, R. C.; Mcdonald, H.
1986-01-01
A numerical method originally developed for three-dimensional supersonic inlet flow calculations is extended and applied to the study of two-dimensional and three-dimensional flows associated with arbitrary propulsion systems. The method is based on the forward spatial marching solution of a reduced form of the three-dimensional steady Navier-Stokes equations in which streamwise pressure gradients are retained in both the subsonic and supersonic regions. The present paper briefly describes the analysis and then shows three applications. In the first application, a wall transpiration study has been performed for the two-dimensional shock wave/turbulent boundary layer interaction flow field with application to an inlet configuration. The second application treats a rectangular high speed inlet with a swept sideplate including the effects of sideplate spillage. Finally, the method is utilized to analyze the interaction of an under-expanded supersonic jet with an ambient flow. Computed results are examined and compared with available experimental measurements. It is demonstrated that the present numerical method is capable of numerically simulating complex two- and three-dimensional flows relevant to hypersonic propulsion systems in a manner which both shows good agreement with data when such data is available, and which shows the complex flow features in the absence of data.
Bender, Andrea; Schlimm, Dirk; Beller, Sieghard
2015-10-01
The domain of numbers provides a paradigmatic case for investigating interactions of culture, language, and cognition: Numerical competencies are considered a core domain of knowledge, and yet the development of specifically human abilities presupposes cultural and linguistic input by way of counting sequences. These sequences constitute systems with distinct structural properties, the cross-linguistic variability of which has implications for number representation and processing. Such representational effects are scrutinized for two types of verbal numeration systems-general and object-specific ones-that were in parallel use in several Oceanic languages (English with its general system is included for comparison). The analysis indicates that the object-specific systems outperform the general systems with respect to counting and mental arithmetic, largely due to their regular and more compact representation. What these findings reveal on cognitive diversity, how the conjectures involved speak to more general issues in cognitive science, and how the approach taken here might help to bridge the gap between anthropology and other cognitive sciences is discussed in the conclusion. PMID:26424227
Numerical simulation of the blood flow in the human cardiovascular system.
Zácek, M; Krause, E
1996-01-01
This paper describes a numerical model of the human cardiovascular system. The model is composed of 15 elements connected in series representing the main parts of the system. Each element is composed of a rigid connecting tube and an elastic reservoir. The blood flow is described by a one-dimensional time-dependent Bernoulli equation. The action of the ventricles is simulated with a Hill's three-element model, adapted for the left and right heart. The closing of the four heart valves is simulated with the aid of time-dependent drag coefficients. Closing is achieved by letting the drag coefficient approach infinity. The resulting system of 32 non-linear ordinary differential equations is solved numerically with the Runge-Kutta method. The results of the simulation (pressure-time and volume-time dependence for the atria and ventricles and pressure forms in the aorta at a heart rate of 70 beats per minute) agree with the physiological data given in the literature. The model's input aortic impedance is 31.5 dyn s cm-5 which agrees with literature data given for aortic input impedance in man 26-80 dyn s cm-5). Long-term stability of the system was achieved. The cardiovascular system presented here can also be simulated at higher and varying heart rates--up to 200 beats per minute. The results of calculations for some pathological changes (e.g. valvular abnormalities) are discussed. PMID:8839013
NASA Astrophysics Data System (ADS)
Pagliarulo, Vito; Russo, Tiziana; Miccio, Lisa; Ferraro, Pietro
2015-10-01
Digital holography (DH) in microscopy became an important interferometric tool in optical metrology when camera sensors reached a higher pixel number with smaller size and high-speed computers became able to process the acquired images. This allowed the investigation of engineered surfaces on microscale, such as microelectromechanical systems (MEMS). In DH, numerical tools perform the reconstruction of the wave field. This offers the possibility of retrieving not only the intensity of the acquired wavefield, but also the phase distribution. This review describes the principles of DH and shows the most important numerical tools discovered and applied to date in the field of MEMS. Both the static and the dynamic regimes can be analyzed by means of DH. Whereas the first one is mostly related to the characterization after the fabrication process, the second one is a useful tool to characterize the actuation of the MEMS.
NASA Astrophysics Data System (ADS)
Andreozzi, A.; Buonomo, B.; Manca, O.; Mesolella, P.; Tamburrino, S.
2012-11-01
In this paper different high temperature TES components are numerically analyzed. The difference is defined by the different type of porous medium employed in the storage. Two different porous media are considered: spheres or foams. In all cases a ceramic material is considered. In the formulation of the model it is assumed that the system geometry is cylindrical, the fluid and the solid thermophysical properties are temperature independents, the radiation heat transfer mechanism is taken into account. The commercial CFD Fluent code is used to solve the governing equations in transient regime and in local thermal non-equilibrium (LTNE). Numerical simulations are carried out at different mass flow rates of the heat-carrying fluid. The results show the effects of the porosity and of the working fluid mass flow rate on the stored thermal energy and on the storage time.
Comparison of numerical models for predicting ground water rebound in abandoned deep mine systems
NASA Astrophysics Data System (ADS)
Choi, Y.; Baek, H.; Kim, D.
2012-12-01
Cessation of dewatering usually results in ground water rebound after closing a deep underground mine because the mind voids and surrounding strata flood up to the levels of decant points such as shafts and drifts. Several numerical models have been developed to predict the timing, magnitude and location of discharges resulting from ground water rebound. We compared the numerical models such as VSS-NET, GRAM and MODFLOW codes at different spatial and time scales. Based on the comparisons, a new strategy is established to develop a program for ground water rebound modeling in abandoned deep mine systems. This presentation describes the new strategy and its application to an abandoned underground mine in Korea.
Numerical modeling of solidification and convection in a viscous pure binary eutectic system
NASA Technical Reports Server (NTRS)
Oldenburg, Curtis M.; Spera, Frank J.
1991-01-01
The solidification and convection of the pure binary eutectic silicate system diopside-anorthite (Di-An) is numerically modeled. A mass-weighted enthalpy of fusion is used to account for the second solid phase (An) which crystallizes at the solidus temperature. Variable under-relaxation is used to aid convergence of the momentum equations in the implementation of the SIMPLER algorithm used to solve the two-dimensional continuum conservation equations. Numerical experiments of the solidification of Di80 melt show that a large temperature drop occurs across the solid and mush regions which decreases convective vigor in the liquid. Interesting compositional segregation patterns are produced during the solidification of Di80.
Minsky, D. M.; Valda, A. A.; Somacal, H.; Burlon, A. A.; Kreiner, A. J.
2007-02-12
A tomographic system for online dose measurements in Boron Neutron Capture Therapy (BNCT) based on the measurement of a specific 478 keV {gamma}-ray emitted after the neutron capture in boron is being developed. In the present work we study by means of Monte Carlo numerical simulations the effects of the finite spatial resolution and the limited number of counts, i. e. the statistical noise, on the reconstructed image contrast of numerical phantoms. These phantoms, of simple geometry, mimic the tumor (specific) and the normal tissue (non specific) boron concentrations. The simulated projection data were reconstructed using the expectation-maximization maximum-likelihood algorithm. These studies will help in the improvement of BNCT dosimetry.
Finite element modeling of borehole heat exchanger systems. Part 2. Numerical simulation
NASA Astrophysics Data System (ADS)
Diersch, H.-J. G.; Bauer, D.; Heidemann, W.; Rühaak, W.; Schätzl, P.
2011-08-01
Single borehole heat exchanger (BHE) and arrays of BHE are modeled by using the finite element method. Applying BHE in regional discretizations optimal conditions of mesh spacing around singular BHE nodes are derived. Optimal meshes have shown superior to such discretizations which are either too fine or too coarse. The numerical methods are benchmarked against analytical and numerical reference solutions. Practical application to a borehole thermal energy store (BTES) consisting of 80 BHE is given for the real-site BTES Crailsheim, Germany. The simulations are controlled by the specifically developed FEFLOW-TRNSYS coupling module. Scenarios indicate the effect of the groundwater flow regime on efficiency and reliability of the subsurface heat storage system.
ERIC Educational Resources Information Center
Oyeleye, Omobola Awosika
2013-01-01
The purpose of the study was to examine the circumstances and practices that led to OCR and DOJ investigations in seven selected school districts, and to determine the emerging themes from the details of the settlement agreements between the school districts and the United States. The themes developed through this study were aimed at providing a…
Numerical Modeling of Compliant-Moored System Dynamics with Applications to Marine Energy Converters
NASA Astrophysics Data System (ADS)
Nichol, Tyler
The development of a numerical model simulating the dynamic response of compliant-moored submerged systems to non-uniform fluid flow is presented. The model is meant to serve as a computational tool with applications to compliant-moored marine energy converters by time-domain representation of the mooring dynamics. The scope of the initial code is restricted to full-submerged moored tidal turbines, though the model can be readily expanded to analyze wave energy converters as well. The system is modeled in a Lagrangian frame treating tidal turbines and structural elements as rigid bodies. Mooring lines are modeled as a series of discrete elastic segments, with parameters and force contributions lumped to point-mass nodes joining each segment. Full-range of motion is achieved using the alpha-beta-gamma Euler Angle method. The governing equations of motion of the system are derived computationally through implementation of Lagrange's Equation of Motion. The techniques employed to develop the symbolic expressions for the total kinetic, potential, and damping energies of the system and the forces acting on each element of the system are discussed. The system of differential equations obtained from evaluation of Lagrange's Equation with the developed symbolic expressions is solved numerically using a built-in MATLAB ordinary differential equation solver called ODE15i.m with the user defined initial condition of the system. Several validation tests are presented and their results discussed. Finally, an explanation of future plans for development of the model and application to existing tidal energy systems are presented.
Numerical algorithms for computations of feedback laws arising in control of flexible systems
NASA Technical Reports Server (NTRS)
Lasiecka, Irena
1989-01-01
Several continuous models will be examined, which describe flexible structures with boundary or point control/observation. Issues related to the computation of feedback laws are examined (particularly stabilizing feedbacks) with sensors and actuators located either on the boundary or at specific point locations of the structure. One of the main difficulties is due to the great sensitivity of the system (hyperbolic systems with unbounded control actions), with respect to perturbations caused either by uncertainty of the model or by the errors introduced in implementing numerical algorithms. Thus, special care must be taken in the choice of the appropriate numerical schemes which eventually lead to implementable finite dimensional solutions. Finite dimensional algorithms are constructed on a basis of a priority analysis of the properties of the original, continuous (infinite diversional) systems with the following criteria in mind: (1) convergence and stability of the algorithms and (2) robustness (reasonable insensitivity with respect to the unknown parameters of the systems). Examples with mixed finite element methods and spectral methods are provided.
NASA Technical Reports Server (NTRS)
Ho, C. Y.; Li, H. H.
1989-01-01
A computerized comprehensive numerical database system on the mechanical, thermophysical, electronic, electrical, magnetic, optical, and other properties of various types of technologically important materials such as metals, alloys, composites, dielectrics, polymers, and ceramics has been established and operational at the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) of Purdue University. This is an on-line, interactive, menu-driven, user-friendly database system. Users can easily search, retrieve, and manipulate the data from the database system without learning special query language, special commands, standardized names of materials, properties, variables, etc. It enables both the direct mode of search/retrieval of data for specified materials, properties, independent variables, etc., and the inverted mode of search/retrieval of candidate materials that meet a set of specified requirements (which is the computer-aided materials selection). It enables also tabular and graphical displays and on-line data manipulations such as units conversion, variables transformation, statistical analysis, etc., of the retrieved data. The development, content, accessibility, etc., of the database system are presented and discussed.
Numerical Treatment of the Boltzmann Equation for Self-Propelled Particle Systems
NASA Astrophysics Data System (ADS)
Thüroff, Florian; Weber, Christoph A.; Frey, Erwin
2014-10-01
Kinetic theories constitute one of the most promising tools to decipher the characteristic spatiotemporal dynamics in systems of actively propelled particles. In this context, the Boltzmann equation plays a pivotal role, since it provides a natural translation between a particle-level description of the system's dynamics and the corresponding hydrodynamic fields. Yet, the intricate mathematical structure of the Boltzmann equation substantially limits the progress toward a full understanding of this equation by solely analytical means. Here, we propose a general framework to numerically solve the Boltzmann equation for self-propelled particle systems in two spatial dimensions and with arbitrary boundary conditions. We discuss potential applications of this numerical framework to active matter systems and use the algorithm to give a detailed analysis to a model system of self-propelled particles with polar interactions. In accordance with previous studies, we find that spatially homogeneous isotropic and broken-symmetry states populate two distinct regions in parameter space, which are separated by a narrow region of spatially inhomogeneous, density-segregated moving patterns. We find clear evidence that these three regions in parameter space are connected by first-order phase transitions and that the transition between the spatially homogeneous isotropic and polar ordered phases bears striking similarities to liquid-gas phase transitions in equilibrium systems. Within the density-segregated parameter regime, we find a novel stable limit-cycle solution of the Boltzmann equation, which consists of parallel lanes of polar clusters moving in opposite directions, so as to render the overall symmetry of the system's ordered state nematic, despite purely polar interactions on the level of single particles.
Solving the Bateman equations in CASMO5 using implicit ode numerical methods for stiff systems
Hykes, J. M.; Ferrer, R. M.
2013-07-01
The Bateman equations, which describe the transmutation of nuclides over time as a result of radioactive decay, absorption, and fission, are often numerically stiff. This is especially true if short-lived nuclides are included in the system. This paper describes the use of implicit numerical methods for o D Es applied to the stiff Bateman equations, specifically employing the Backward Differentiation Formulas (BDF) form of the linear multistep method. As is true in other domains, using an implicit method removes or lessens the (sometimes severe) step-length constraints by which explicit methods must abide. To gauge its accuracy and speed, the BDF method is compared to a variety of other solution methods, including Runge-Kutta explicit methods and matrix exponential methods such as the Chebyshev Rational Approximation Method (CRAM). A preliminary test case was chosen as representative of a PWR lattice depletion step and was solved with numerical libraries called from a Python front-end. The Figure of Merit (a combined measure of accuracy and efficiency) for the BDF method was nearly identical to that for CRAM, while explicit methods and other matrix exponential approximations trailed behind. The test case includes 319 nuclides, in which the shortest-lived nuclide is {sup 98}Nb with a half-life of 2.86 seconds. Finally, the BDF and CRAM methods were compared within CASMO5, where CRAM had a FOM about four times better than BDF, although the BDF implementation was not fully optimized. (authors)
NASA Astrophysics Data System (ADS)
Ohchi, Masashi; Furukawa, Tatsuya; Tanaka, Shin-Ichiro
Among several numerical methods, a Finite Element Method (FEM) has been adopted in various engineering problems. In such a background, it is necessary to instruct university students in the numerical analysis. The authors have designed and implemented the numerical analysis education support system for learning electromagnetic fields with Graphical User Interface (GUI) based on the server-client model using Java. In the paper, a feasibility study on the student laboratory class in the third year is described.