Showing papers by "General Electric published in 1992"

Decimation of triangle meshes

Abstract: The polygon remains a popular graphics primitive for computer graphics application. Besides having a simple representation, computer rendering of polygons is widely supported by commercial graphics hardware and software. However, because the polygon is linear, often thousands or millions of primitives are required to capture the details of complex geometry. Models of this size are generally not practical since rendering speeds and memory requirements are proportional to the number of polygons. Consequently applications that generate large polygonal meshes often use domain-specific knowledge to reduce model size. There remain algorithms, however, where domainspecific reduction techniques are not generally available or appropriate. One algorithm that generates many polygons is marching cubes. Marching cubes is a brute force surface construction algorithm that extracts isodensity surfaces from volume data, producing from one to five triangles within voxels that contain the surface. Although originally developed for medical applications, marching cubes has found more frequent use in scientific visualization where the size of the volume data sets are much smaller than those found in medical applications. A large computational fluid dynamics volume could have a finite difference grid size of order 100 by 100 by 100, while a typical medical computed tomography or magnetic resonance scanner produces over 100 slices at a resolution of 256 by 256 or 512 by 512 pixels each. Industrial computed tomography, used for inspection and analysis, has even greater resolution, varying from 512 by 512 to 1024 by 1024 pixels. For these sampled data sets, isosurface extraction using marching cubes can produce from 500k to 2,000k triangles. Even today’s graphics workstations have trouble storing and rendering models of this size. Other sampling devices can produce large polygonal models: range cameras, digital elevation data, and satellite data. The sampling resolution of these devices is also improving, resulting in model sizes that rival those obtained from medical scanners. This paper describes an application independent algorithm that uses local operations on geometry and topology to reduce the number of triangles in a triangle mesh. Although our implementation is for the triangle mesh, it can be directly applied to the more general polygon mesh. After describing other work related to model creation from sampled data, we describe the triangle decimation process and its implementation. Results from two different geometric modeling applications illustrate the strengths of the algorithm.

A CFAR adaptive matched filter detector

Abstract: An adaptive algorithm for radar target detection using an antenna array is proposed. The detector is derived in a manner similar to that of the generalized likelihood-ratio test (GLRT) but contains a simplified test statistic that is a limiting case of the GLRT detector. This simplified detector is analyzed for performance to signals on boresight, as well as when the signal direction is misaligned with the look direction. >

Stereo from uncalibrated cameras

Abstract: The problem of computing placement of points in 3-D space, given two uncalibrated perspective views, is considered. The main theorem shows that the placement of the points is determined only up to an arbitrary projective transformation of 3-space. Given additional ground control points, however, the location of the points and the camera parameters may be determined. The method is linear and noniterative, whereas previously known methods for solving the camera calibration and placement problem to take proper account of both ground-control points and image correspondences are unsatisfactory in requiring either iterative methods or model restrictions. As a result of the main theorem, it is possible to determine projective invariants of 3-D geometric configurations from two perspective views. >

A technique for accurate magnetic resonance imaging in the presence of field inhomogeneities

Abstract: A technique for producing geometrically accurate magnetic resonance images (MRIs) with undistorted intensity in the face of high levels of static field inhomogeneity arising from either source is presented. The technique requires the acquisition of two images of the same object with altered gradients. On the basis of a knowledge of these gradients it employs an automatic postprocessing step that exploits some invariant characteristics of the distortions to produce a rectified image from the two acquired images. No phantom imaging is involved and no operator interaction is required. The technique is theoretically justified and compared to other techniques, and experimental results that show that the technique works are presented. The improved accuracy in geometry and intensity may improve reliability of stereotactic surgery, may enhance the feasibility of both clinical and industrial imaging via external fields, and may increase the resolution of microscopic imaging. >

Coded excitation system for improving the penetration of real-time phased-array imaging systems

Abstract: Based on an analysis of the inherent signal-to-noise ratio (SNR) in medical ultrasound imaging, SNR improvements of 15-20 dB are theoretically possible for real-time phased-array imagers using coded excitation. A very simple coded excitation for phased arrays based on the principles of 'pseudochirp' excitation and equalization filtering is described. This system is capable of SNR improvements of about 15 dB with range sidelobe levels acceptable for many medical imaging applications. Such improvements permit increased operating frequencies, and hence enhanced spatial resolution, for real-time array imagers. Both simulations and measurements are used to demonstrate the efficacy of the method. >

Cosine-modulated FIR filter banks satisfying perfect reconstruction

Abstract: The authors obtain a necessary and sufficient condition on the 2M (M=number of channels) polyphase components of a linear-phase prototype filter of length N=2 mM (where m=an arbitrary positive integer), such that the polyphase component matrix of the modulated filter is lossless. The losslessness of the polyphase component matrix, in turn, is sufficient to ensure that the analysis/synthesis system satisfies perfect reconstruction (PR). Using this result, a novel design procedure is presented based on the two-channel lossless lattice. This enables the design of a large class of FIR (finite impulse response)-PR filter banks, and includes the N=2M case. It is shown that this approach requires fewer parameters to be optimized than in the pseudo-QMF (quadrature mirror filter) designs and in the lossless lattice based PR-QMF designs (for equal length filters in the three designs). This advantage becomes significant when designing long filters for large M. The design procedure and its other advantages are described in detail. Design examples and comparisons are included. >

Balanced-line RF electrode system for use in RF ground heating to recover oil from oil shale

Abstract: An in-situ method of extracting oil from a hydrocarbon bearing layer such as oil-shale or tar sands lying beneath a surface layer comprises applying a radiofrequency excitation signal to the hydrocarbon bearing layer through a system of electrodes. The electrodes are inserted into a matrix of holes drilled through the surface layer and into the hydrocarbon bearing layer. A coaxial line extending through the surface layer is connected to the electrodes extending into the hydrocarbon bearing layer. The electrodes have a length that is an integral number of quarter wavelengths of the radiofrequency energy. A matching network connected between the coaxial cable and a respective one of the electrodes maximizes the power flow into each electrode. The electrodes are excited uniformly in rows and as a "balanced-line" RF array where adjacent rows of electrodes are 180° out of phase. This method does not produce substantial heating of the surface layer or the region surrounding the producing layer, and concentrates most of its power in the hydrocarbon bearing layer.

Methods of Motor Current Signature Analysis

Abstract: Recently a technique for monitoring and diagnosing mechanical problems, associated with rotating machines driven by electric motors, has been proposed and is now being offered by several commercial suppliers. This technique, known as “Motor Current Signature Analysis” or MCSA, seeks to apply much of the long experience in vibration signature analysis to the analysis of motor current in effect using the motor as a sensor akin to an acceleromeier This paper explores some of the history of the technique, presents several examples, and demonstrates a first order approach to the theory with associated cautions.

MR-guided focused ultrasound surgery.

Abstract: Magnetic resonance guided focused ultrasound surgery provides a minimally invasive controlled method for selectively destroying deep-lying tissue. A thermal analysis of focused ultrasound provides an estimate of the time-dependent temperature distribution and thermal dose required for ultrasound surgery. The temperature distribution is estimated by accumulating heat sources, considering the effects of thermal conductivity, heat content, and perfusion. In this study, both gel phantoms and excised in vitro bovine muscle specimens were imaged in a 1.5 T MR system while heated with a 5 cm diameter, 10 cm focal length, 1.1 MHz transducer. During sonication, the thermal effects were observed with T1-weighted pulse sequences. Below a critical temperature, the heat zone appeared as a dark spot that moved with the focal spot. Above a critical thermal dose, the in vitro tissue was irreversibly altered and the focal lesion was observed on both the MR image and the specimen slice.

Tracking system to monitor the position and orientation of a device using multiplexed magnetic resonance detection

Abstract: A tracking system employs magnetic resonance signals to monitor the position and orientation of at least one device such as a catheter within a subject. The device has a plurality of receiver coils which are sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the device's position and orientation in several dimensions. The position and orientation of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images. One or more devices can be simultaneously tracked.

Air fuel mixer for gas turbine combustor

Abstract: An air fuel mixer is disclosed having a mixing duct, a shroud surrounding the upstream end of the mixing duct having contained therein a fuel manifold in flow communication with a fuel supply and control means, a set of inner and outer counter-rotating swirlers adjacent the upstream end of the mixing duct, hollow vanes in at least the outer swirler having passages therethrough in fluid communication with the fuel manifold to inject fuel into the mixing duct, and a hub separating the inner and outer swirlers to allow independent rotation thereof, wherein high pressure air from a compressor is injected into the mixing duct through the swirlers to form an intense shear region and fuel is injected into the mixing duct from the swirler vanes so that the high pressure air and the fuel is uniformly mixed therein so as to produce minimal formation of pollutants when the fuel/air mixture is exhausted out the downstream end of the mixing duct into the combustor and ignited. Further, the air fuel mixer of the present invention may include passages in the wall of the mixing duct in fluid communication with the fuel manifold, a centerbody in the mixing duct having a passage therethrough to admit air into the downstream end of the mixing duct, and tubes extending from the passages in the swirler vanes and/or mixing duct wall to inject liquid fuel downstream of the swirlers.

Satellite and subsatellite formation in capillary breakup

Abstract: An investigation of the interfacial-tension-driven fragmentation of a very long fluid filament in a quiescent viscous fluid is presented. Experiments covering almost three orders of magnitude in viscosity ratio reveal as many as 19 satellite droplets in between the largest droplets; complementary boundary-integral calculations are used to study numerically the evolution of the filament as a function of the viscosity ratio of the fluids and the initial wavenumber of the interface perturbation. Satellite drops are generated owing to multiple breakup sequences around the neck region of a highly deformed filament. In low-viscosity ratio systems, p < O(0.1), the breakup mechanism is self-repeating in the sense that every pinch-off is always associated with the formation of a neck, the neck undergoes pinch-off, and the process repeats. In general the agreement between computations and experiments is excellent; both indicate that the initial wavenumber of the disturbance is important in the quantitative details of the generated drop size distributions. However, these details are insignificant when compared with the large variations produced in the drop size distributions owing to variation in the viscosity ratio.

Nucleotide sequencing and transcriptional mapping of the genes encoding biphenyl dioxygenase, a multicomponent polychlorinated-biphenyl-degrading enzyme in Pseudomonas strain LB400.

Abstract: The DNA region encoding biphenyl dioxygenase, the first enzyme in the biphenyl-polychlorinated biphenyl degradation pathway of Pseudomonas species strain LB400, was sequenced. Six open reading frames were identified, four of which are homologous to the components of toluene dioxygenase from Pseudomonas putida F1 and have been named bphA, bphE, bphF, and bphG. From this comparison, biphenyl dioxygenase was found to be a multicomponent enzyme containing a two-subunit iron-sulfur protein, a ferredoxin, and a reductase. Comparison of the large subunit of the iron-sulfur protein and the ferredoxin with other multicomponent dioxygenases identified amino acid sequences similar to Rieske iron-sulfur proteins for binding a [2Fe-2S] cluster. Sequences have also been identified in the reductase component that match the consensus sequence for FAD or NAD binding. Transcription of the biphenyl dioxygenase region was examined, and three transcription initiation sites were identified. Transcription initiating at the site furthest upstream is greatly increased when the LB400 cells are grown on biphenyl as the sole carbon source.

Routine quantitative analysis of brain and cerebrospinal fluid spaces with MR imaging

Abstract: A computerized system for processing spin-echo magnetic resonance (MR) imaging data was implemented to estimate whole brain (gray and white matter) and cerebrospinal fluid volumes and to display three-dimensional surface reconstructions of specified tissue classes. The techniques were evaluated by assessing the radiometric variability of MR volume data and by comparing automated and manual procedures for measuring tissue volumes. Results showed (a) the homogeneity of the MR data and (b) that automated techniques were consistently superior to manual techniques. Both techniques, however, were affected by the complexity of the structure, with simpler structures (eg, the intracranial cavity) showing less variability and better spatial correlation of segmentation results between raters. Moreover, the automated techniques were completed for whole brain in a fraction of the time required to complete the equivalent segmentation manually. Additional evaluations included interrater reliability and an evaluation that included longitudinal measurement, in which one subject was imaged sequentially 24 times, with reliability computed from data collected by three raters over 1 year. Results showed good reliability for the automated segmentation procedures.

An hdtv compression system

Abstract: Apparatus for encoding/decoding an HDTV signal for e.g., terrestrial transmission includes a compression circuit (10) responsive to high definition video source signals for providing hierarchically layered codewords CW representing compressed video data and associated codewords T, defining the types of data represented by the codewords CW. A priority selection circuit (11), responsive to the codewords CW and T, parses the codewords CW into high and low priority codeword sequences wherein the high and low priority codeword sequences correspond to compressed video data of relatively greater and lesser importance to image reproduction respectively. A transport processor (12), responsive to the high and low priority codeword sequences, forms high and low priority transport blocks of high and low priority codewords respectively. Each transport block includes a header, codewords CW and error detection check bits. The respective transport blocks are applied to a forward error check circuit (15, 16) for applying additional error check data. Thereafter the high and low priority data are applied to a modem (17) wherein they quadrature amplitude modulate respective carriers for transmission.

Surge Dynamics in a Free-Spool Centrifugal Compressor System

Abstract: Turbocharger surge has been investigated in a radial impeller-vaneless diffuser free-spool system. Several different aspects are addressed. First, two very different compression systems, one with a large downstram volume and one with the smallest possible downstram voluem, are employed to examine stall initiation phenomena as well as the behavior of the compressor characteristics when operating in surge. The measurements show impeller stall at the inducer tips to be a key phenomena in initiating surge. The inducer stall is stationary and asymmetric, due to the presence of the volute, and is most severe near the volute tongue angular position

Biodegradation of bisphenol A and other bisphenols by a gram-negative aerobic bacterium

Abstract: A novel bacterium designated strain MV1 was isolated from a sludge enrichment taken from the wastewater treatment plant at a plastics manufacturing facility and shown to degrade 2,2-bis(4-hydroxyphenyl)propane (4,4'-isopropylidenediphenol or bisphenol A). Strain MV1 is a gram-negative, aerobic bacillus that grows on bisphenol A as a sole source of carbon and energy. Total carbon analysis for bisphenol A degradation demonstrated that 60% of the carbon was mineralized to CO2, 20% was associated with the bacterial cells, and 20% was converted to soluble organic compounds. Metabolic intermediates detected in the culture medium during growth on bisphenol A were identified as 4-hydroxybenzoic acid, 4-hydroxyacetophenone, 2,2-bis(4-hydroxyphenyl)-1-propanol, and 2,3-bis(4-hydroxyphenyl)-1,2-propanediol. Most of the bisphenol A degraded by strain MV1 is cleaved in some way to form 4-hydroxybenzoic acid and 4-hydroxyacetophenone, which are subsequently mineralized or assimilated into cell carbon. In addition, about 20% of the bisphenol A is hydroxylated to form 2,2-bis(4-hydroxyphenyl)-1-propanol, which is slowly biotransformed to 2,3-bis(4-hydroxyphenyl)-1,2-propanediol. Cells that were grown on bisphenol A degraded a variety of bisphenol alkanes, hydroxylated benzoic acids, and hydroxylated acetophenones during resting-cell assays. Transmission electron microscopy of cells grown on bisphenol A revealed lipid storage granules and intracytoplasmic membranes.

Minimum scan speeds for suppression of motion artifacts in CT.

Abstract: Cardiac and ventilatory motions cause artifacts at chest computed tomography (CT). To determine how short the scan times on third-generation units must be to avoid such artifacts, motion was measured with fast and ultrafast CT scans. Minimum detectable motion was then determined. The longest scan time that avoided a barely perceptible artifact was calculated by dividing the minimum detectable motion by the peak physiologic velocity. The posterior left ventricular wall moved at a maximum velocity of 52.5 mm/sec, necessitating a scan time of 19.1 msec or less to avoid artifact. Lung vessels near the heart moved at 40.5 mm/sec for a scan time of 24.7 msec or less. During quiet breathing, pulmonary vessels moved at 10.7 mm/sec for a scan time of 93.5 msec or less. The authors conclude that the shortest scan time on third-generation units (0.6 second) cannot prevent all artifacts arising from motion in the chest. Even ultrafast scan times (50 msec) are not short enough to eliminate artifacts on these units. Th...

Algorithmic statistical process control: concepts and an application

Abstract: The goal of algorithmic statistical process control is to reduce predictable quality variations using feedback and feedforward techniques and then monitor the complete system to detect and remove unexpected root causes of variation. This methodology seeks to exploit the strengths of both automatic control and statistical process control (SPC), two fields that have developed in relative isolation from one another. Recent experience with the control and monitoring of intrinsic viscosity from a particular General Electric polymerization process has led to a better understanding of how SPC and feedback control can be united into a single system. Building on past work by MacGregor, Box, Astrom, and others, the article covers the application from statistical identification and modeling to implementing feedback control and final SPC monitoring. Operational and technical issues that arose are examined, and a general approach is outlined.

Active reflectarray antenna for communication satellite frequency re-use

Abstract: An antenna suited for a communications satellite includes two separately located, mutually orthogonally polarized feed antennas such as vertically and horizontally polarized linear horns. The horns feed an active reflector antenna array. The array includes a plurality of mutually orthogonally polarized antenna elements such as crossed dipoles or square patch antenna with cross feeds for two independent orthogonal polarizations. The feeds of the antenna elements are coupled to amplifier modules. Each module includes a circulator for each polarization, coupled to a processor including a low noise amplifier, controlled phase shifter, variable gain amplifier and power amplifier. The output of the power amplifier feeds the antenna element through the circulator. The large number of radiating elements allows high power using power amplifier with relatively modest capabilities. The phase shifters of each module independently control the reradiation phase of the vertical and horizontal signals, so that a collimated beam can be independently focused to the two feed points, one for each polarization.

Data compression system including successive approximation quantizer

Abstract: A data processing system augments compression of non-zero values of significant coefficients by coding entries of a significance map independently of coding the values of significant non-zero coefficients. A dedicated symbol represents a zerotree structure encompassing a related association of insignificant coefficients within the tree structure. The zerotree symbol represents that a coefficient is a root of a zerotree if, at a threshold T, the coefficient and all of its descendants that have been found to be insignificant at larger thresholds have magnitudes less than threshold T. The zerotree structure is disclosed in the context of a pyramid-type image subband processor together with successive refinement quantization and entropy coding to facilitate data compression.

Chaos, symmetry, and self-similarity: exploiting order and disorder in mixing processes.

Abstract: Fluid mixing is a successful application of chaos. Theory anticipates the coexistence of order and disorder-symmetry and chaos-as well as self-similarity and multifractality arising from repeated stretching and folding. Experiments and computations, in turn, provide a point of confluence and a visual analog for chaotic behavior, multiplicative processes, and scaling behavior. All these concepts have conceptual engineering counterparts: examples arise in the context of flow classification, design of mixing devices, enhancement of transport processes, and controlled structure formation in two-phase systems.

Shroud cooling assembly for gas turbine engine

Abstract: To cool the shroud in the high pressure turbine section of a gas turbine engine, high pressure cooling air is directed in metered flow to baffle plenums and thence through baffle perforations to impingement cool the shroud rails and back surface. Impingement cooling air then flows through elongated, convection cooling passages in the shroud and exits to flow along the shroud front surface with the main gas stream to provide film cooling. The baffle perforations and the convection cooling passages are interactively located to achieve maximum cooling benefit and highly efficient cooling air utilization.

Metal-matrix composites for electronic packaging

Abstract: A materials revolution is underway, and there are profound implications for electronic packaging materials. Composites, especially metal-matrix composites, are playing a key role, because of their unique and tailorable combinations of properties; light weight; and low-cost, net-shape fabrication potential.

Using multiple knowledge sources for word sense discrimination

Abstract: This paper addresses the problem of how to identify the intended meaning of individual words in unrestricted texts, without necessarily having access to complete representations of sentences. To discriminate senses, an understander can consider a diversity of information, including syntactic tags, word frequencies, collocations, semantic context, role-related expectations, and syntactic restrictions. However, current approaches make use of only small subsets of this information. Here we will describe how to use the whole range of information. Our discussion will include how the preference cues relate to general lexical and conceptual knowledge and to more specialized knowledge of collocations and contexts. We will describe a method of combining cues on the basis of their individual specificity, rather than a fixed ranking among cue-types. We will also discuss an application of the approach in a system that computes sense tags for arbitrary texts, even when it is unable to determine a single syntactic or semantic representation for some sentences.

Some aspects of the thermal conductivity of isotopically enriched diamond single crystals.

Abstract: New data on the thermal-conductivity temperature dependence k(T) of both natural abundance and isotopically enriched synthetic diamond gems are presented. The existing data on the thermal-conductivity temperature dependence k(T) of natural type-IIa diamond have been reanalyzed using a comprehensive Klemens-Callaway model. The high thermal conductivity of isotopically pure diamond is shown to be consistent with the model.

Method and apparatus for conveying compressed video data over a noisy communication channel

Abstract: A digital compressed video signal transmission system includes a transport processor for segmenting compressed data into transport cells for transmission. Particular portions of the compressed data are formatted into further transport cells, which further transport cells are interspersed with normally occurring transport cells. The further transport cells include redundant video signal data which may be utilized to resynchronize a compressed video signal decoder after loss or corruption of transmitted data.

Self-accommodating brush seal for gas turbine combustor

Abstract: The gas turbine includes a combustor 10 having a transition piece 18 with its exit end spaced from a first-stage nozzle 22. A brush seal 26 seals about the space between the transition piece and first-stage nozzle. The brush seal includes a sealing cap 28 supported by one of the transition piece and the first-stage nozzle and having a portion 38 overlying the other of the transition piece and first-stage nozzle. A seal ring 30 is secured to the other of the transition piece and the first-stage nozzle and carries bristles 32 projecting therefrom for engagement with the overlying portion 38 of the sealing cap 28 to seal the gap between the transition piece and the first-stage nozzle. In one form, the side face portions of the bristles of the bristle pack form the seal by engaging against a planar sealing surface.

Efficient synthetic aperture imaging from a circular aperture with possible application to catheter-based imaging

Abstract: Phased-array imaging, including complete dynamic focus, is explored for imaging using a circular aperture. Based on the constraints of catheter-based systems, an efficient synthetic aperture method has been developed for imaging using a single wire connection between the imaging array and external electronics. The method employs a highly sampled array with an element pitch small compared to the acoustic wavelength. On any given firing of the array, however, a large number of channels are electrically connected on both transmission and reception. From firing to firing, one element is dropped and one new element is included, in analogy to a classic linear array system. Using an optimal filtering approach for synthetic aperture reconstruction, a dynamically focused image exhibiting diffraction limited resolution is produced. The results of detailed simulations are presented demonstrating the capabilities of the method. In addition, the prospects for real-time implementation of the reconstruction are discussed. >