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Air Force Institute of Technology

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Articles 2641 - 2670 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Photoluminescence Spectroscopy Of Mbe Grown Gallium Antimonide, John A. Dorian Dec 1991

Photoluminescence Spectroscopy Of Mbe Grown Gallium Antimonide, John A. Dorian

Theses and Dissertations

Experimental data are presented for the energy levels of the native acceptor and bound exciton emissions of GaSb grown by MBE and studied with low temperature photoluminescence (PL) spectroscopy. The undoped GaSb emissions showed a donor-acceptor pair transition with an observed emission peak at 776 meV, a peak at 716 meV usually associated with the ionization level of the acceptor, and bound exciton transitions in the energy range from 796 to 804 meV. Other unidentified peaks were observed at about 805 meV. Temperature and power dependence studies of the acceptor peak confirmed donor-acceptor pair (DAP) behavior. A GaSb sample grown …

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Silicon Carbide Thin Film Deposition By Reactive Ion-Beam Sputtering, Larry G. Sills Dec 1991

Silicon Carbide Thin Film Deposition By Reactive Ion-Beam Sputtering, Larry G. Sills

Theses and Dissertations

In this study, hydrogenated amorphous silicon carbide thin films were deposited by reactive ion-beam sputtering under varying conditions to determine whether a film's optical properties can be controlled, focusing on refractive index. Using a Kaufman type ion source to sputter a pure silicon target, three distinct series of films were grown. The first series varied the mixture of methane and argon used in the ion-beam. holding all other parameters constant. For the second series the gas mix was fixed, and only the beam energy (beam voltage) was varied. The final series also varied beam energy, but was grown with a …

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Binary Programming Models Of Spatial Pattern Recognition: Applications In Remote Sensing Image Analysis, Thomas G. Reed Dec 1991

Binary Programming Models Of Spatial Pattern Recognition: Applications In Remote Sensing Image Analysis, Thomas G. Reed

Theses and Dissertations

The major purpose of this investigation was to implement subregion allocation objectives using a network model base on an existing subregion allocation binary programming model (Benabdallah and Wright (B&W), 1990), the ultimate goal being the application of subregion allocation concepts towards the spatial analysis of satellite imagery. The multi-objective aspects of subregion allocation can be accomplished via a network formulation, a formulation vastly simpler in complexity than the binary programming models previously used. Without a network programming package that could maintain integral flows, however, deriving the solution was a tiresome task for the user. Nonetheless, several new concepts and advantages …

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A Formal Definition Of The Object-Oriented Paradigm For Requirements Analysis, Andrew D. Boyd Dec 1991

A Formal Definition Of The Object-Oriented Paradigm For Requirements Analysis, Andrew D. Boyd

Theses and Dissertations

This paper develops a formal definition of the Object-Oriented paradigm for requirements analysis. The literature was surveyed for both formal and informal methods for conducting an Object-Oriented Requirements Analysis (OORA). The informal methods reviewed are: Bailin's, Shlaer and Mellor's, Booch's, and Coad and Yourdon's. The formal methods reviewed are: Bralick's, Z, and REFINE. None of the methods were found to be adequate for doing an OORA. A formal definition of an OORA, based on the concept of classes, is developed. The definition itself is presented as set and relation theory. A supporting graphical representation is also developed and presented. The …

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Multi-Layered Feedforward Neural Networks For Image Segmentation, Gregory L. Tarr Dec 1991

Multi-Layered Feedforward Neural Networks For Image Segmentation, Gregory L. Tarr

Theses and Dissertations

Artificial neural network image segmentation techniques are examined. The biological inspired cortex transform is examined as a means to preprocess images for segmentation and classification. A generalized neural network formalism is presented as a means to produce common pattern recognition processing techniques in a single iterable element. Several feature reduction preprocessing techniques, based on feature saliency, Karhunen-Loeve transformation and identity networks are tested and compared. The generalized architecture is applied to a problem in image segmentation, a tracking of high- value fixed tactical targets. A generalized architecture for neural networks is developed based on the second order terms of the …

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An Expert System For Measuring, Interpreting, And Managing System Performance Factors For The Work Information Management System, Billy J. C. Irwin Dec 1991

An Expert System For Measuring, Interpreting, And Managing System Performance Factors For The Work Information Management System, Billy J. C. Irwin

Theses and Dissertations

This study develops an expert system for measuring, interpreting, and managing the Wang VS operating system performance factors for the Work Information Management System. The system's performance concerns least known to system administrators are identified. Of these, SHARER buffers and VTOC cache are identified as factors that can significantly impact system performance with little effort. A six step process is used in developing the expert system. Concept maps representing the structure of the Wang VS Disk Input/Output problem domain are provided. The expert system provides information about the system parameters, SHARER buffers and VTOC cache, and recommends main memory allocations. …

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A Delphi Forecast Of 1996 Roles: Air Force Institute Of Technology Information Resource Management Graduates Assigned To Base Level, David O. Block Dec 1991

A Delphi Forecast Of 1996 Roles: Air Force Institute Of Technology Information Resource Management Graduates Assigned To Base Level, David O. Block

Theses and Dissertations

Graduates of the Air Force Institute of Technology's Information Resource Management master's degree program who are subsequently assigned to base-level positions believe their IRM expertise is wasted in base administration roles that preclude the use of their up-to-date technical educations in managing automated information resources. This research forecasts the role AFIT IRM graduates assigned to base-level positions will need to fill by the year 1996. The research further determined what changes are necessary to resolve the perceived differences between current and forecast roles for these graduates. The Delphi survey method of forecasting was selected as an effective method of discovering …

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Relative Utility Of Selected Software Requirement Metrics, James H. Byers Dec 1991

Relative Utility Of Selected Software Requirement Metrics, James H. Byers

Theses and Dissertations

The objective of this study was to determine the relative utility of selected software requirement metrics in assessing the productivity of the software requirements analysis process and the quality of the products of this process. This objective was met by collecting information about the perceptions that practicing software professionals have of the usefulness of various requirement metrics. The study employed a two part methodology. The first part utilized Basili's goal/question/metric paradigm to identify specific goals of the measurement effort and to identify requirement metrics worthy of further investigation. The second part employed a typical research design to gather perceptions that …

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Plasma Transport In A Magnetic Multicusp Negative Hydrogen Ion Source, Ricky G. Jones Dec 1991

Plasma Transport In A Magnetic Multicusp Negative Hydrogen Ion Source, Ricky G. Jones

Theses and Dissertations

An analysis of plasma transport through the magnetic filter in tandem magnetic multicusp negative hydrogen ion sources was conducted to determine the mechanism of thermal electron diffusion, explain thermal electron cooling, describe the transport of primary electrons through the filter, and model positive ion species transport. The thermal electron flux was shown to exceed its classical value by one to three orders of magnitude. The flux variation with temperature was best described using a Coulomb-like temperature gradient drag term, consistent with diffusion due to ion-sound-like turbulence. Thermal electron energy flux loss was shown to be dominated by inelastic collisions at …

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An Expert System Advisor For Medical Evaluation Boards, Jerry S. G. Harrington Dec 1991

An Expert System Advisor For Medical Evaluation Boards, Jerry S. G. Harrington

Theses and Dissertations

Expert system technology has proven itself to be able to improve productivity and decision making in a variety of fields of endeavor. The purpose of this study was to determine if an expert system for medical evaluation boards (MEBs) could improve upon the processing of medical evaluation board cases. Research was conducted to develop an expert system and measure the capabilities of the system, both in terms of accuracy and timeliness of case completion of the medical evaluation administrators/clerks who were assisted by the system. The research methodology involved a three - phase approach. The objective of phase one was …

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Radar System Classification Using Neural Networks, David M. Cameron Dec 1991

Radar System Classification Using Neural Networks, David M. Cameron

Theses and Dissertations

This study investigated methods of improving the accuracy of neural networks in the classification of large numbers of classes. A literature search revealed that neural networks have been successful in the radar classification problem, and that many complex problems have been solved using systems of multiple neural networks. The experiments conducted were based on 32 classes of radar system data. The neural networks were modelled using a program called the Neural Graphics Analysis System. It was found that the accuracy of the individual neural networks could be increased by controlling the number of hidden nodes, the relative numbers of training …

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Parallel Implementation Of Vhdl Simulations On The Intel Ipsc/2 Hypercube, Ronald C. Comeau Dec 1991

Parallel Implementation Of Vhdl Simulations On The Intel Ipsc/2 Hypercube, Ronald C. Comeau

Theses and Dissertations

VHDL models are executed sequentially in current commercial simulators. As chip designs grow larger and more complex, simulations must run faster. One approach to increasing simulation speed is through parallel processors. This research transforms the behavioral and structural models created by Intermetrics' sequential VHDL simulator into models for parallel execution. The models are simulated on an Intel iPSC/2 hypercube with synchronization of the nodes being achieved by utilizing the Chandy Misra paradigm for discrete-event simulations. Three eight-bit adders, the ripple carry, the carry save, and the carry-lookahead, are each run through the parallel simulator. Simulation time is cut in at …

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Logic Programming In Digital Circuit Design, Joseph W. Eicher Dec 1991

Logic Programming In Digital Circuit Design, Joseph W. Eicher

Theses and Dissertations

The design of large, complex digital circuitry requires highly skilled engineers. Much of the time spent by these engineers in the design phase involves tasks that are repetitive, tedious, and slow. If these repetitive tasks are automated, the engineer can spend more time managing the design process and produce a better-quality design in less time. Logic programming can be used to automate design tasks, even those that require a high degree of skill. This thesis investigates several aspects of the digital circuit design process that involve pattern-matching paradigms suitable for encoding in the logic programming language Prolog.

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A Spatially Partitioned Parallel Simulation Of Colliding Objects, Robert S. Moser Dec 1991

A Spatially Partitioned Parallel Simulation Of Colliding Objects, Robert S. Moser

Theses and Dissertations

This study investigated the application of a conservative synchronization paradigm to the classical, distributed pool balls simulation executed on an eight node, Intel iPSC/2 hypercube. Wieland's concept of spatial partitioning and limited data replication was used. Analysis has shown that 100% parallelization of execution is possible in a conservative environment via assignment of multiple sectors to nodes. Two conservative formulations for minimum safe time were derived. A tradeoff exists between scalability and efficiency. Optimum sectoring prediction has been shown possible through application of linear regression techniques. The results of this research reveal that a conservative approach to distributed, discrete event …

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Lqg Control Of A Deformable Mirror Adaptive Optics System With Time- Delayed Measurements, David J. Anderson Dec 1991

Lqg Control Of A Deformable Mirror Adaptive Optics System With Time- Delayed Measurements, David J. Anderson

Theses and Dissertations

This thesis proposes a linear quadratic Gaussian (LQG) control law for a ground-based deformable mirror adaptive optics system. The incoming image wavefront is distorted, primarily in phase, due to the turbulent effects of the earth's atmosphere. The adaptive optics system attempts to compensate for the distortion with a deformable mirror. A Hartman wavefront sensor measures the degree of distortion in the image wavefront. The measurements are input to a Kalman filter which estimates the system states. The state estimates are processed by a linear quadratic regulator which generates the appropriate control voltages to apply to the deformable mirror actuators. The …

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Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot Dec 1991

Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot

Theses and Dissertations

This thesis documents the design, fabrication, and testing of a lightweight, planar microwave lens. The lens consists of two planar arrays of lightweight printed circuit antennas interconnected by microstrip lines whose length varies as a function of position on the lens. Microwave energy is coupled from one face of the lens to the other by means of a slot etched in the ground plane. At 8.0 GHz the lens is ten wavelengths across, is less than 1/8 inch thick, and weighs less than 4 pounds. The lens can scan a beam over a +/- 30 degree region in both the …

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Function Prediction Using Recurrent Neural Networks, Randall L. Lindsey Dec 1991

Function Prediction Using Recurrent Neural Networks, Randall L. Lindsey

Theses and Dissertations

A fully recurrent neural network was applied to the function prediction problem. The real-time recurrent learning (RTRL) algorithm was modified and tested for use as a viable function predictor. The modification gave the algorithm a variable learning rate and a linear/sigmoidal output selection. Verifying the networks ability to temporally learn both the classic exclusive-OR (XOR) problem and the internal state problem, the network was then used to simulate the frequency response of a second order IIR lowpass Butterworth filter. The recurrent network was then applied to two problems: head position tracking, and voice date reconstruction. The accuracy at which the …

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Vibrational Energy Transfer In Bromine Monofluoride, Tim L. Thompson Dec 1991

Vibrational Energy Transfer In Bromine Monofluoride, Tim L. Thompson

Theses and Dissertations

Bromine monofluoride (BrF), an interhalogen molecule, is a prospective chemical laser candidate. This study continues research begun in characterizing radiative and collisional dynamics in BrF. Vibrational energy transfer of BrF is studied using time resolved laser induced fluorescence (LIF) techniques and observing the spectrally resolved emission. First, vibrational transfer induced by the BrF production mix is determined to follow the Montroll- Shuler model and Landau-Teller scaling with a fundamental rate coefficient of kv(1,0) = (4.0) x 10-12 cm3/(molecules seconds). Also, rate coefficients for the rare gases were found to scale with the reduced mass of the collision …

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Real Imagery As A Three Dimensional Display, Juan C. Echeverry Dec 1991

Real Imagery As A Three Dimensional Display, Juan C. Echeverry

Theses and Dissertations

This research effort implemented two 3-D display designs to assess their performance and effect on an observer's depth perception. Both 3-D displays produced real images for the observer to view. The first display setup combined a lens relay with a two concave mirror projector. The second display setup combined the two concave mirror projector with a diffuser. The lens relay/ two concave mirror projector combination was successful in imaging a source from the CRT to a point in space above the two mirror system. The problem was that the observer could not assess the image location by just looking at …

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An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii Dec 1991

An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii

Theses and Dissertations

This study attempted to analytically reproduce experimental and analytical data, on the single-insulated and conducting PRIZ, presented in 1987 and 1988 by the Soviet scientists Bliznetsov et al. Our onedimensional analytical models, derived from earlier Soviet reports, have consistently reproduced previously reported data on the PRIZ. In this study, the same codes were successfully used to analyze the effects of injection at high and low intensity exposures (30 µW/cm2 to 500 mW/cm2) Although the codes qualitatively duplicated the nature of the space charge distribution in the single-insulated and conducting PRIZ, our quantitative results were significantly different from …

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Object-Oriented Analysis And Design Of The Saber Wargame, Christine M. Sherry Dec 1991

Object-Oriented Analysis And Design Of The Saber Wargame, Christine M. Sherry

Theses and Dissertations

This thesis presents an object-oriented analysis and design of Saber, a theater-level computerized wargame, for the Air Force Wargaming Center, Maxwell AFB, Alabama. The analysis and design is based on a recently developed conceptual model, and existing land battle, and additional research. This thesis also begins the implementation process. The design was accomplished using an iterative, five step design process. Objects and operations were chosen and then encapsulated in Ada packages. This thesis also makes necessary changes to the land battle as described by the conceptual model and as the result of additional research. Sound software engineering principles were used …

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A Hybrid Approach To Battlefield Parallel Discrete Event Simulation, Steven R. Soderholm Dec 1991

A Hybrid Approach To Battlefield Parallel Discrete Event Simulation, Steven R. Soderholm

Theses and Dissertations

This thesis describes a method of parallelizing a battlefield discrete event simulation. The method combines elements of conservative time synchronization together with elements of optimistic computation and local rollback on a message passing hardware architecture. The battle simulation features aircraft moving in a battle area and launching missiles at enemy aircraft. Aircraft are randomly grouped into logical process (LPs), and a single LP is assigned to each processor. Aircraft state information is replicated across all LPs. Only the LP with the minimum next event time can execute safely. While one LP is executing safely all other LPs are precomputing their …

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Graph-Based Visualization Of Formal Specification And Domain Specific Languages, Randel K. Langloss Dec 1991

Graph-Based Visualization Of Formal Specification And Domain Specific Languages, Randel K. Langloss

Theses and Dissertations

This research develops and implements Visual Refine, a graph-based visualization system, for the Refine wide-spectrum formal specification language and environment developed and marketed by Reasoning Systems, Inc. Refine specifications are represented in the Refine object base as abstract syntax trees (AST). Using these AST representations, one-to-one mappings are defined between nodes of the AST and the graphical icons of Visual Refine. Visual Refine uses these mappings to implement a set of formal transformations. Each transformation is encapsulated within a Refine rule, and this set of rules form the Visual Refine transformation system. The Visual Refine transformation system, in conjunction with …

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Control Of A Large Flexible Space Structure Using Multiple Model Adaptive Algorithms, John A. Gustafson Dec 1991

Control Of A Large Flexible Space Structure Using Multiple Model Adaptive Algorithms, John A. Gustafson

Theses and Dissertations

The development and performance of moving-bank multiple model adaptive estimation (MMAE) and control (MMAC) algorithms for quelling vibrations induced in the SPICE 2 space structure are analyzed in this thesis. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. The model supplied by Phillips Laboratory, Kirtland AFB is used to develop a truth model and multiple reduced ordered filter models. The filter models are developed from modal analysis and internally balanced techniques. Deviations of the line-of-sight vector from the center of the large platform to the center of the smaller …

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An Event Driven State Based Interface For Synthetic Environments, Mark J. Gerken Dec 1991

An Event Driven State Based Interface For Synthetic Environments, Mark J. Gerken

Theses and Dissertations

Previous research at the Air Force Institute of Technology (AFIT) has produced synthetic environments using head mounted displays (HMDs) and hand measurement devices. This thesis is a continuation of AFIT synthetic environment research. Hand measurement data from a VPL DataGlove is combined with hand orientation and translational data to define a set of valid gestures. These gestures form the basis of an input language for class of finite automata known as finite state machines. Using the input symbols from this language, the user may define a finite state machine which associates a stream of input symbols with one or more …

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Parallelizing Serial Code For A Distributed Processing Environment With An Application To High Frequency Electromagnetic Scattering, Paul R. Work Dec 1991

Parallelizing Serial Code For A Distributed Processing Environment With An Application To High Frequency Electromagnetic Scattering, Paul R. Work

Theses and Dissertations

This thesis investigates the parallelization of existing serial programs in computational electromagnetics for use in a parallel environment. Existing Algorithms for calculating the radar cross section of a object are covered, and a ray-tracing code is chosen for implementation on a parallel machine. Current parallel architectures are introduced and a suitable parallel machine is selected for the implementation of the chosen ray tracing algorithm. The standard techniques for the parallelization of serial code are discussed, including load balancing and decomposition considerations, and appropriate methods for the parallelization effort are selected. A load balancing algorithm is modified to increase the efficiency …

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Establishing A Methodology For Evaluation And Selecting Computer Aided Software Engineering Tools For A Defined Software Engineering Environment At The Air Force Institute Of Technology School Of Engineering, Jody L. Mattingly Dec 1991

Establishing A Methodology For Evaluation And Selecting Computer Aided Software Engineering Tools For A Defined Software Engineering Environment At The Air Force Institute Of Technology School Of Engineering, Jody L. Mattingly

Theses and Dissertations

This thesis identifies the software engineering environment (SEE) as it exists at the Air Force Institute of Technology (AFIT) School of Engineering. It also describes the software process model employed and the software development methods presented as part of the curriculum. Based on this information, criteria was established to evaluate computer aided software engineering (CASE) tools being considered for integration into the SEE. Each criterion was weighted to indicate its importance when selecting CASE tools. The criteria were further used to establish a methodology to be used to evaluate and select the CASE tools under consideration as well as future …

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Structured Hypermedia Application Development Model (Shadm): A Structured Model For Technical Documentation Application Design, Peter W. Cassell Dec 1991

Structured Hypermedia Application Development Model (Shadm): A Structured Model For Technical Documentation Application Design, Peter W. Cassell

Theses and Dissertations

This research was conducted to determine how a Royal Australian Air Force technical maintenance publication could be transformed into a task oriented hypermedia application and to develop a model that could be used for future similar transformations. The model was developed following in-depth analysis of the existing USAF F-15E maintenance publication set and validation was conducted using a prototype developed in HyperWriter, a commercial hypermedia product. The prototype model was based around the performance of three maintenance tasks on an aircraft sub-subsystem and incorporated online user access to the necessary support data for task completion. Publication managers, producers, and users …

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Possible Application Of Quality Function Deployment In Software Systems Development In The United States Air Force, Craig R. Lamb Dec 1991

Possible Application Of Quality Function Deployment In Software Systems Development In The United States Air Force, Craig R. Lamb

Theses and Dissertations

The objectives of the thesis were to determine whether the methods of Quality Function Deployment (QFD) could be used in the software development environment within the USAF, and whether or not this area should be researched further. The research was limited to the requirements analysis and definition phase. The different areas of study included a brief review of the structured analysis methodology, a detailed review of the QFD models currently being used in the product industries, a review of how QFD fits into the software development cycle, and specific software modifications to the QFD methodology. A review of some applications …

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An Object-Oriented Database Implementation Of The Magic Vlsi Layout Design System, Timothy M. Jacobs Dec 1991

An Object-Oriented Database Implementation Of The Magic Vlsi Layout Design System, Timothy M. Jacobs

Theses and Dissertations

This thesis attempts to prove that the commercially available Object Store data management system provide the performance and functionality necessary to support a complex engineering design system. This is accomplished by modifying the Magic VLSI circuit layout design system to eliminate its current Unix file data management system and replace it with Object Store. The approach to this research effort includes a design recovery of the Magic system and identification of its ket data management functions. These functions are then modified to take advantage of the database management facilities of Object Store. Additional code is added to instrument performance measurement …

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