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Theses and Dissertations

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Articles 2521 - 2550 of 2733

Full-Text Articles in Computer Sciences

Searching For Plans Using A Hierarchy Of Learned Macros And Selective Reuse, Douglas E. Dyer Jun 1994

Searching For Plans Using A Hierarchy Of Learned Macros And Selective Reuse, Douglas E. Dyer

Theses and Dissertations

This research presents a new approach to improving the performance of a macro planner: selective reuse. In macro planning, reuse can result in poorer performance than when planning with only primitive operators, a phenomenon that has been called the utility problem. The utility problem arises because the benefits of reuse are outweighed by the cost of retrieving a macro to reuse and the cost of searching through the larger search space caused by considering reuse candidates. Selective reuse contains the expansion of the search space by limiting the number of reuse candidates considered and limits the search required by considering …

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Multirate Time-Frequency Distributions, John R. O'Hair May 1994

Multirate Time-Frequency Distributions, John R. O'Hair

Theses and Dissertations

Multirate systems, which find application in the design and analysis of filter banks, are demonstrated to also be useful as a computational paradigm. It is shown that any problem which can be expressed a set of vector-vector, matrix-vector or matrix-matrix operations can be recast using multirate. This means all of numerical linear algebra can be recast using multirate as the underlying computational paradigm. As a non-trivial example, the multirate computational paradigm is applied to the problem of Generalized Discrete Time- Frequency Distributions GDTFD to create a new family of fast algorithms. The first of this new class of distributions is …

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Subgrouped Real Time Recurrent Learning Neural Networks, Jeffrey S. Dean May 1994

Subgrouped Real Time Recurrent Learning Neural Networks, Jeffrey S. Dean

Theses and Dissertations

A subgrouped Real Time Recurrent Learning (RTRL) network was evaluated. The one layer net successfully learns the XOR problem, and can be trained to perform time dependent functions. The net was tested as a predictor on the behavior of a signal, based on past behavior. While the net was not able to predict the signal's future behavior, it tracked the signal closely. The net was also tested as a classifier for time varying phenomena; for the differentiation of five classes of vehicle images based on features extracted from the visual information. The net achieved a 99.2% accuracy in recognizing the …

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Global Picture Archiving And Communication Systems (Gpacs): An Overview, Russell C. Ellis Apr 1994

Global Picture Archiving And Communication Systems (Gpacs): An Overview, Russell C. Ellis

Theses and Dissertations

The world is currently experiencing a computer revolution. With the expansion and development of new computer technology, the age of video is upon us. The medical world is also currently undergoing a dramatic change. With the development and perfection of non-invasive techniques of probing the body, large amounts of computer data is collected and much of it is used to generate images. The organization and management of these images is the topic of this thesis. The discussion of storage schemes, databases, communications and data compression techniques gives the reader a background and some insight to the current state of the …

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A Format For Storing And Managing Multiple Level Of Detail Terrain For Simulated Environments, Keith L. Meissner Mar 1994

A Format For Storing And Managing Multiple Level Of Detail Terrain For Simulated Environments, Keith L. Meissner

Theses and Dissertations

This study investigated a method of storing, managing and rendering terrain data, while addressing conflicting goals of. rendering speed, display detail and memory usage. A data structure is presented to store terrain data, with an object oriented system to manage the data stored in the structure. The structure stores terrain data in a compact form which is converted into rendering structures in real time. The structure uses levels of detail to maintain display detail. The structure is compared against an existing format for storing terrain data, MultiGen Flight. The system managing the structure is shown to decrease memory usage and …

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Effective Parallel Algorithm Animation, Paul W. Chase Mar 1994

Effective Parallel Algorithm Animation, Paul W. Chase

Theses and Dissertations

The AFIT Algorithm Animation Research Facility AAARF was developed by the Air Force Institute of Technology AFIT as a teaching aid for data structures and algorithm design. In particular, an extensive set of performance animations has been developed for the Intel iPSC Hypercube parallel processing system. This research focuses in part on developing animation support for discrete event simulation, mission routing, and evolutionary algorithms based on abstract representations of parallel algorithm behavior. The effort also builds extensions to the AAARF system and examines direction for further research. An innovative adaptable application-specific animation construction environment has been designed and implemented. The …

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Dyadic Wavelet Features For Isolated Word Speaker Dependent Speech Recognition, Stephen Ainge Mar 1994

Dyadic Wavelet Features For Isolated Word Speaker Dependent Speech Recognition, Stephen Ainge

Theses and Dissertations

This research examines the use of dyadic wavelet features for the recognition of speaker dependent isolated word speech. The features were generated using three different wavelet filters-Daubechies 4 coefficient (Db4), Daubechies 20 coefficient (Db20) and a 31 coefficient cubic spline and three different window lengths-15ms, 8ms and 4ms. The accuracy of the standard and over-sampled dyadic wavelet methods were compared. The over-sampled dyadic wavelet method using the Db4 scaling function, with a maximum accuracy of 65.5, was found to be the most accurate of the wavelet methods tested. The accuracy of this over-sampled dyadic Db4 wavelet method was compared to …

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Clustering Techniques In Speaker Recognition, Douglas N. Prescott Mar 1994

Clustering Techniques In Speaker Recognition, Douglas N. Prescott

Theses and Dissertations

This thesis presents a comparison based on identification rate, of three clustering techniques applied to cepstral features for speaker identification. LBG vector quantization as developed by Linde, Buzo and Gray; is used to provide benchmark performance for comparison with Fuzzy clustering (based on the unsupervised fuzzy partition-optimal number of classes, UFP-ONC algorithm by Gath and Geva) and an Artificial Neural Network, the Multilayer Perceptron. Cepstral features from the TIMIT, King and AFIT93 corpus speaker databases are used to produce speaker-identification classifiers using each of the clustering algorithms. The experiment reported evaluates the speaker identification performance using the 20-dimensional cepstral features …

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Application Of Sequential Quadratic Programming To Large-Scale Structural Design Problems, Mark A. Abramson Mar 1994

Application Of Sequential Quadratic Programming To Large-Scale Structural Design Problems, Mark A. Abramson

Theses and Dissertations

Large-scale structural optimization problems are often difficult to solve with reasonable efficiency and accuracy. Such problems are often characterized by constraint functions which are not explicitly defined. Constraint and gradient functions are usually expensive to evaluate. An optimization approach which uses the NLPQL sequential quadratic programming algorithm of Schittkowski, integrated with the Automated Structural Optimization System ASTROS is tested. The traditional solution approach involves the formulation and solution of an explicitly defined approximate problem during each iteration. This approach is replaced by a simpler approach in which the approximate problem is eliminated. In the simpler approach, each finite element analysis …

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A Simulation Approach To Granite Sentry System Analysis, Marilyn J. Bauer Mar 1994

A Simulation Approach To Granite Sentry System Analysis, Marilyn J. Bauer

Theses and Dissertations

This study demonstrated the use of simulation modelling to analyze Granite Sentry system performance. The availability simulation model constructed provides a number of system performance measures as a function of component MTBFs and MTTRs. Analysis of failure data prior to model construction supported the generally accepted use of exponentially distributed failure rates and lognormally distributed repair times.

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The Effective Use Of Animation In Simulation Model Validation, Christopher L. Swider Mar 1994

The Effective Use Of Animation In Simulation Model Validation, Christopher L. Swider

Theses and Dissertations

This study examined two animation displays moving icons, bar graphs at two presentation speeds to determine how each of these factors affected the animations ability to communicate violations of model assumptions. Subjects viewed animation displays individually and in combination at each presentation speed. Eight problem scenarios were presented to evaluate each animations ability to communicate violations of different assumptions. Each animations communication ability was measured subjectively and objectively. Subjective measures in the form of pairwise comparisons were used to calculate normalized preference ratings for each animation. objective measures included problem identification accuracy and problem time. Subjective results indicated that moving …

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Assessing The Vulnerability Of Multi-Commodity Networks With Failing Components, Alan R. Robinson Mar 1994

Assessing The Vulnerability Of Multi-Commodity Networks With Failing Components, Alan R. Robinson

Theses and Dissertations

This research proposes an analytical approach for assessing flow disturbance, or compromise, based on limited sampling of arc flow information in multi-commodity, or multiple origin-destination O-D, networks with failing arcs. There were three objectives established for this research. The first objective was to bound the expected flow, given the arcs fail with certain probabilities, which was accomplished by reviewing current approaches for single-commodity networks and extending the results to the multi-commodity case. The second objective was to determine the best placement of flow monitors to obtain the most accurate estimates of O-D pair volumes. This was accomplished using a multi-criteria …

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A Fortran Based Learning System Using Multilayer Back-Propagation Neural Network Techniques, Gregory L. Reinhart Mar 1994

A Fortran Based Learning System Using Multilayer Back-Propagation Neural Network Techniques, Gregory L. Reinhart

Theses and Dissertations

An interactive computer system which allows the researcher to build an optimal neural network structure quickly, is developed and validated. This system assumes a single hidden layer perceptron structure and uses the back- propagation training technique. The software enables the researcher to quickly define a neural network structure, train the neural network, interrupt training at any point to analyze the status of the current network, re-start training at the interrupted point if desired, and analyze the final network using two- dimensional graphs, three-dimensional graphs, confusion matrices and saliency metrics. A technique for training, testing, and validating various network structures and …

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Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran Dec 1993

Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran

Theses and Dissertations

This thesis designed, constructed, and tested a robotic arm for the Aerobot Aerial Robot. The main purpose of the ARM is to enable the Aerobot to retrieve objects for use in an annual robotics competition. Design of the ARM involved synthesizing the characteristics of simplicity, weight, strength, and size. The result was a three-degree-of-freedom manipulator that uses electric motors, cable linkages, and telescoping tubes to access a work space below the Aerobot. Forward and inverse kinematics were investigated to enable automation of the ARM. Data was collected from infrared sensors to validate the model. Manipulation of the ARM is presently …

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A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake Dec 1993

A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake

Theses and Dissertations

A numerical analysis of the aerodynamic phenomena associated with the high-speed flight of a sharp-nosed, four-finned, high-fineness ratio missile using a block-structured, parallel computer algorithm is presented. The algorithm, PANS-3EM, utilizes a second-order-accurate, shock-capturing, Total Variation Diminishing scheme and incorporates a Baldwin-Lomax turbulence model. PANS-3EM allows for extreme flexibility in the choice of computational domain decomposition and computing machine of implementation. Developmental work consists of conceptualization and verification of the algorithm as well as parallel performance and scalability studies conducted on a variety of computing platforms. Using PANS-3EM, the aerodynamic characteristics of the missile are investigated. Drag and pitching moment …

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Genetic Algorithms And Their Application To The Protein Folding Problem, Donald J. Brinkman Dec 1993

Genetic Algorithms And Their Application To The Protein Folding Problem, Donald J. Brinkman

Theses and Dissertations

The protein folding problem involves the prediction of the secondary and tertiary structure of a molecule given the primary structure. The primary structure defines sequence of amino-acid residues, while the secondary structure describes the local 3-dimensional arrangement of amino-acid residues within the molecule. The relative orientation of the secondary structural motifs, namely the tertiary structure, defines the shape of the entire biomolecule. The exact, mechanism by which a sequence of amino acids protein folds into its 3- dimensional conformation is unknown Current approaches to the protein folding problem include calculus-based methods, systematic search, model building and symbolic methods, random methods …

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A Parallel Computational Fluid Dynamics Unstructured Grid Generator, Deborah E. Davis Dec 1993

A Parallel Computational Fluid Dynamics Unstructured Grid Generator, Deborah E. Davis

Theses and Dissertations

This research addressed the development of a parallel computational fluid dynamics unstructured grid generator using Delaunay triangulation. The generator is applied to simple elliptical and cylindrical two-dimensional bodies. The methodologies used included Watsons point insertion algorithm, Holmes and Snyders point creation algorithm, a discretized surface definition, Andersons clustering function, and a Laplacian smoother. The first version of the software involved a processor boundary exchange at the end of each iteration with no inter-processor communications during the iterations The second version used inter-processor communication during each iteration instead of the boundary exchange. Version 1 demonstrated a speedup of 1.8 for some …

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Developing A Sophisticated User Interface To Support Domain-Oriented Application Composition And Generation Systems, Jay A. Cossentine Dec 1993

Developing A Sophisticated User Interface To Support Domain-Oriented Application Composition And Generation Systems, Jay A. Cossentine

Theses and Dissertations

This research refined the visual presentation and usability of a previously developed visual interface for a domain-oriented application composition and generation system. The refined visual interface incorporated domain-specific bit-mapped graphics and sophisticated user interface design concepts to reduce user workload. User workload was reduced through object layout, window design, and color utilization techniques; by combining repetitive procedures into single commands; and reusing, rather than recreating, composition information throughout the application composition process. The Software Refinery environment, including its graphical interface tool INTERVISTA, was used to develop techniques for visualizing and manipulating objects contained in a formal object base. INTERVISTA was …

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Alternative Architectures For Domain-Oriented Application Composition And Generation Systems, Warren E. Gool Dec 1993

Alternative Architectures For Domain-Oriented Application Composition And Generation Systems, Warren E. Gool

Theses and Dissertations

This thesis presents a formalized framework for comparing the structure and semantics of software architectures. The framework uses object diagrams for analyzing the structure of the architectures and the axiomatic approach for analyzing the semantics. This framework is used to compare the Object Connection Update OCU model developed by the Software Engineering Institute against four other software architectures VHDL defined by Lipsett, MetaH defined by Honeywell, microRapide defined by Luckham, and hierarchical software systems as defined by Batory. The goal of the comparison was to evaluate the OCU model for suitability within prototype application composition and generation systems. This research …

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Using Database Technology To Support Domain-Oriented Application Composition Systems, Danny A. Cecil, Joseph A. Fullenkamp Dec 1993

Using Database Technology To Support Domain-Oriented Application Composition Systems, Danny A. Cecil, Joseph A. Fullenkamp

Theses and Dissertations

This research designed and prototyped an OODBMS technology base to store and retrieve various types of domain artifacts for domain-oriented application composition systems (DOACS). We developed object-oriented database schemas for a validating domain and the Object-Connection-Update software architecture. We implemented an inheritance relationship between the schemas so a domain model can inherit an architectural structure from an architecture model allowing us to isolate domain-specific knowledge from architecture-specific knowledge. We also developed a meta-model to formally define domain models in the database. We then developed a set of database methods to transform a domain model into a database schema for storing …

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A Distributed Interactive Simulation Based Remote Debriefing Tool For Red Flag Missions, Michael T. Gardner Dec 1993

A Distributed Interactive Simulation Based Remote Debriefing Tool For Red Flag Missions, Michael T. Gardner

Theses and Dissertations

Air Force leaders, recognizing the need for improved training following the Vietnam War, implemented the Red Flag exercises at Nellis AFB. At the heart of this training is the Red Flag Measurement and Debriefing System RFMDS and its capability to accurately reconstruct the elements of an intense exercise fought over the deserts of Nevada. This thesis uses the technology of distributed interactive simulation DIS to transmit aircraft telemetry onto computer networks, allowing the monitoring and analysis of live Red Flag missions at any site with compatible communications equipment and thesis software. The use of standard DIS protocols enables simulators to …

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Integration And Enhancement Of The Saber Wargame, Karl S. Mathias Dec 1993

Integration And Enhancement Of The Saber Wargame, Karl S. Mathias

Theses and Dissertations

The Saber wargame is a theater-level air/land battle wargame written in Ada that is being developed for the Air Force Wargaming Center at Maxwell AFB, AL. This thesis documents how the user interface and simulation engine were integrated. Integration was accomplished by developing a portable object-oriented database system (OODBMS) interface. The interface was implemented in Ada and tied to an OODBMS also written in Ada. Using the interface, both subsystems were able to work from a consistent database and exchange information. The user interface was enhanced by converting it from the Software Technology for Adaptable Reliable Systems Ada/X Window System …

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A Prototype Architecture For An Automated Scenario Generation System For Combat Simulations, Mark W. Pfefferman Dec 1993

A Prototype Architecture For An Automated Scenario Generation System For Combat Simulations, Mark W. Pfefferman

Theses and Dissertations

This research effort examines the problem of automating the scenario generation process and presents a prototype architecture for an automated scenario generation system. This architecture is designed using an object- oriented approach which leads to a modular and modifiable design. The architecture provides a mechanism for automatically generating scenario files from a textual US Army operation order. This translation process occurs in two phases. First, the text operation order is translated into an intermediate format called the mission file. In the second phase, the system reads the mission file, instantiates intelligent entities, and assigns missions to those entities. The intelligent …

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Design Of A Shared Coherent Cache For A Multiple Channel Architecture, John A. Reisner Dec 1993

Design Of A Shared Coherent Cache For A Multiple Channel Architecture, John A. Reisner

Theses and Dissertations

The Multiple Channel Architecture MCA is a recently proposed computer architecture which uses fiber optic communications to overcome many of the problems associated with interconnection networks. There exists a detailed MCA simulator which faithfully simulates an MCA system, however, the original version of the simulator did not cache shared data. In order to improve the performance of the MCA, a cache coherency protocol was developed and implemented in the simulator. The protocol has two features which are significant: (1) a time-division multiplexed TDM communication bus is used for coherency traffic, and (2) the shared data is cached in an independent …

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Objectsim - A Reusable Object Oriented Dis Visual Simulation, Mark I. Snyder Dec 1993

Objectsim - A Reusable Object Oriented Dis Visual Simulation, Mark I. Snyder

Theses and Dissertations

This research designed and implemented a reusable Distributed Interactive Simulation DIS visual simulation architecture for Silicon Graphics platforms. The goal was to research software architecture technologies and to create a design and implementation using these ideas. The architecture was designed using object oriented techniques to provide the ability to customize it via inheritance extension. The resulting design was implemented using C and applied to several DIS visual simulation projects in the Graphics Lab at AFIT. The architecture, named ObjectSim, was successful in its goal of providing a reusable core for the DIS visual simulation projects in the Graphics Lab at …

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Object Interaction In A Parallel Object-Oriented Discrete-Event Simulation, Walter G. Trachsel Dec 1993

Object Interaction In A Parallel Object-Oriented Discrete-Event Simulation, Walter G. Trachsel

Theses and Dissertations

This thesis investigates object interaction issues involved in developing an object-oriented parallel discrete-event simulation and develops a simulation model that provides object interaction capabilities. The research covers issues in object representation, object interaction, object management. discrete-event simulation, and parallel simulation. There are three primary types of objects that the research discusses. The first type is a basic simulation object, whose size and behavior is insignificant compared to the size of the simulation as a whole. The second type is an aggregate object which consists of smaller component objects that interact and affect the performance of the larger object as a …

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A Method For Populating The Knowledge Base Of Afit's Domain-Oriented Application Composition System, Russell M. Warner Dec 1993

A Method For Populating The Knowledge Base Of Afit's Domain-Oriented Application Composition System, Russell M. Warner

Theses and Dissertations

This research developed a formal method for adding new domains to Architect, a domain-oriented application composition system being developed at the Air Force Institute of Technology AFIT to explore new software engineering technologies. Using canonical formal specifications of domain objects, Architect rapidly composes these specifications into a software application and executes a prototype of that application as a means to demonstrate its correctness before any programming language specific code is generated. Architect is implemented in the Software Refinery environment, which allows Architect to create and manipulate object-oriented specifications. As a part of this research effort, domain-oriented application composition systems were …

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Three Dimensional Object Recognition Using A Complex Autoregressive Model, David E. Chelen Dec 1993

Three Dimensional Object Recognition Using A Complex Autoregressive Model, David E. Chelen

Theses and Dissertations

Based on an autoregressive model, Complex Partial Correlation CPARCOR features are known to provide exceptional Position, Scale, and Rotation Invariant PSRI properties for planar 2-Dimensional 2-D object recognition. Although autogressive models have been successfully applied to numerous spatio-temporal recognition tasks, the effects of out-of-plane image rotations were never considered. This study investigates application of the CPAR-COR model to a five class problem of nonplanar 2-D views of 3-D objects. Recognition based on CPAR-COR features is evaluated using a Template Matching algorithm, two K-Nearest-Neighbor KNN classifiers, and a Hidden Markov Model HMM. Direct comparisons to recognition based on Fourier features are …

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Discovery Learning In Autonomous Agents Using Genetic Algorithms, Edward O. Gordon Dec 1993

Discovery Learning In Autonomous Agents Using Genetic Algorithms, Edward O. Gordon

Theses and Dissertations

As the new Distributed Interactive Simulation (DIS) draft standard evolves into a useful document and distributed simulations begin to emerge that implement parts of the standard, there is renewed interest in available methods to effectively control autonomous aircraft agents in such a simulated environment. This investigation examines the use of a genetics-based classifier system for agent control. These are robust learning systems that use the adaptive search mechanisms of genetic algorithms to guide the learning system in forming new concepts (decision rules) about its environment. By allowing the rule base to evolve, it adapts agent behavior to environmental changes. Addressed …

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Graphical Tools For Situational Awareness Assistance For Large Battle Spaces, Brian B. Soltz Dec 1993

Graphical Tools For Situational Awareness Assistance For Large Battle Spaces, Brian B. Soltz

Theses and Dissertations

As virtual environments grow in complexity and size, users are increasingly challenged in assessing situations in large-scale virtual environment. This occurs because of the difficulty in determining where to focus attention and assimilating and assessing the information as it floods in. One technique for providing this type of assistance is to provide the user with a first-person, immersive, synthetic environment observation post, that permits unobtrusive observation of the environment without interfering with the activity in the environment. However, for large, complex synthetic environments, this type of support is not sufficient because the portrayal of raw, unanalyzed data in the virtual …

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