Showing papers by "General Electric published in 1994"

Field-weakening performance of brushless synchronous AC motor drives

Abstract: The paper examines the theoretical and practical limitations to the field-weakening performance of surface permanent magnet, synchronous reluctance and interior permanent magnet motors when driven from an inverter with a limited volt-ampere rating. It is shown that the 'optimal' field-weakening performance consists of an infinite constant-power speed range but is limited to an inverter utilisation of about 0.7. The new concept of the interior permanent magnet parameter plane is introduced. This graphically illustrates the effect of varying the drive parameters on the shape of the field-weakening characteristic. The interior permanent magnet parameter plane is used to show that there are three types of optimal field-weakening designs. When practical factors and considerations are taken into account, the optimal high-saliency interior permanent magnet motor design is the most promising for applications requiring a wide field-weakening range. A 7.5 kW design was built and a constant-power speed range exceeding 7.5:1 was demonstrated.

Experimental heat transfer and friction in channels roughened with angled, v-shaped and discrete ribs on two opposite walls

Abstract: Experimental investigations have shown that the enhancement in heat transfer coefficients for air flow in a channel roughened with angled ribs is on the average higher than that roughened with 90 deg ribs of the same geometry. Secondary flows generated by the angled ribs are believed to be responsible for these higher heat transfer coefficients. In an effort basically to double the area of high heat transfer coefficients, the angled rib is broken at the center to form a V-shaped rib, and tests are conducted to investigate the resulting heat transfer coefficients and friction factors. Three different square rib geometries, corresponding to blockage ratios of 0.083, 0.125, and 0.167, with a fixed pitch-to-height ratio of 10, mounted on two opposite walls of a square channel in a staggered configuration, are tested in a stationary channel for 5,000 < Re < 30,000. Heat transfer coefficients, friction factors, and thermal performances are compared with those of 90 deg, 45 deg, and discrete angled ribs. The V-shaped ribs are tested for both pointing upstream and downstream of the main flow. Test results show that: (a) 90 deg ribs represent the lowest thermal performance, based on the same pumping power, and is essentially themore » same for the 2:1 change in blockage ratio, (b) low-blockage-ratio (E/D{sub h} = 0.083) V-shaped ribs pointing downstream produced the highest heat transfer enhancement and friction factors. Among all other geometries with blockage ratios of 0.125 and 0.167, 45 deg ribs showed the highest heat transfer enhancements with friction factors less than those of V-shaped ribs, (c) thermal performance of 45 deg ribs and the lowest blockage discrete ribs are among the highest of the geometries tested in this investigation, and (d) discrete angled ribs, although inferior to 45 deg and V-shaped ribs, produce much higher heat transfer coefficients and lower friction factors compared to 90 deg ribs.« less

Inductively coupled RF tracking system for use in invasive imaging of a living body

Abstract: RF tracking system employs a RF invasive device coupled to surgical tracking equipment for tracking the invasive device. An inductive coupling permits the device to be quickly coupled to, and decoupled from, the equipment. The coupling comprises an inducting coil which transmits a signal from the surgical tracking equipment to a communicating coil in the invasive device. The signal received by the communicating coil passes along leads to a tracked coil in a distal end of the invasive device. The tracked coil transmits the signal as RF energy which is received by the surgical tracking equipment which superimposes the position of the distal end of the invasive device on an X-ray image and displays it on a monitor A sterile shield is employed as a sterile barrier between the inducting coil and the equipment end of the invasive device to prevent contamination of the invasive device by the inducting coil. The cross-section of the invasive device at its equipment end can be made identical to the rest of the invasive device to permit other invasive devices to pass completely over the invasive device.

Design of high-efficiency RF Class-D power amplifier

Abstract: In this paper, the losses in a Class-D RF switching power amplifier and their frequency dependence are described. The losses analyzed are the switching, conduction, and gate drive losses. A 300 W, 13.56 MHz, Class-D circuit is designed in the traditional manner to illustrate the magnitude of the different types of loss. A circuit using the ZVS equations developed in this paper is designed. An experimental circuit is built using standard IRF540 devices in TO220 packages. That circuit does not meet its performance goals because of the package inductance. A new low inductance half-bridge package is introduced to solve this problem. Techniques for circuit layout and power measurements for RF applications are also presented in the experimental section. A low loss gate drive circuit is also presented using a Class-E circuit to provide the drive power. The experimental results confirm the accuracy of the design equations derived in this paper. >

Projective reconstruction and invariants from multiple images

Abstract: This correspondence investigates projective reconstruction of geometric configurations seen in two or more perspective views, and the computation of projective invariants of these configurations from their images. A basic tool in this investigation is the fundamental matrix that describes the epipolar correspondence between image pairs. It is proven that once the epipolar geometry is known, the configurations of many geometric structures (for instance sets of points or lines) are determined up to a collineation of projective 3-space /spl Pscrsup 3/ by their projection in two independent images. This theorem is the key to a method for the computation of invariants of the geometry. Invariants of six points in /spl Pscrsup 3/ and of four lines in /spl Pscrsup 3/ are defined and discussed. An example with real images shows that they are effective in distinguishing different geometrical configurations. Since the fundamental matrix is a basic tool in the computation of these invariants, new methods of computing the fundamental matrix from seven-point correspondences in two images or six-point correspondences in three images are given. >

Impact of system chemistry on electroosmosis in contaminated soil

Abstract: Electroosmosis in a copper‐contaminated kaolinite was highly sensitive to chemical treatment schemes designed to remove the contamination. Non‐uniform profiles of electric field intensity and pH as well as negative pore‐water pressure develop during sustained electrokinetic treatment of clays. These nonlin‐earities and nonuniform pore‐water pressures cannot be adequately described by classical analysis. Classical analysis is based on assumptions of a uniform and constant electroosmotic permeability coefficient, for instance. An extended capillary model which includes nonuniform contributions to electroosmosis and pore pressures that vary with space and time, is developed and compared with experimental findings. Subtle changes in initial and boundary conditions of the system chemistry have a very large effect on electroosmosis in soils. For instance, acid addition at the cathode reservoir may cause reversal of the direction of electroosmotic flow. Other species, such as the citrate, may form stable complex...

Computer graphic and live video system for enhancing visualisation of body structures during surgery

Abstract: An interactive surgery planning and display system mixes live video of external surfaces of the patient with interactive computer generated models of internal anatomy obtained from medical diagnostic imaging data of the patient. The computer images and the live video are coordinated and displayed to a surgeon in real-time during surgery allowing the surgeon to view internal and external structures and the relation between them simultaneously, and adjust his surgery accordingly. In an alternative embodiment, a normal anatomical model is also displayed as a guide in reconstructive surgery. Another embodiment employs three-dimensional viewing.

An approach for reverse engineering of relational databases

Abstract: A process for reverse engineering of relational databases is proposed. Object-oriented models provide a natural language for facilitating the re-engineering process. An object-oriented model can describe the existing software, the reverse-engineered semantic intent, and the forward-engineered new system. The Object Modeling Technique (OMT) notation for modeling data is adopted. Graphical OMT models are intuitive and provide a rigorous basis for specifying software. A more robust process than advanced in the literature is proposed. Guidelines for coping with design optimizations and unfortunate implementation decisions are provided. The process emphasizes analysis of candidate keys rather than primary keys. Three sources for information are incorporated: schema, observed patterns of data, and the semantic understanding of application intent. >

Three-terminal adaptive nematic liquid-crystal lens device

Abstract: A 1 mm × 1 mm nematic liquid-crystal three-terminal device for optical beam forming (focusing/spoiling) is fabricated. A thin-film-resistor network on the device substrate layer is used to control the voltages on the 98 internal lens electrodes by use of only one variable external driver. By using a high-resistance thin-film layer of amorphous silicon under the 98-element parallel electrode structure layer, we generate a near-continuous index perturbation to form a cylindrical lens. The focal length of this lens is continuously variable from inifinity to 12 cm by use of a variable 1–4-V-peak 1-kHz square-wave external terminal control signal.

Method and system for analyzing error logs for diagnostics

Abstract: The present invention discloses an error log analysis system comprising a diagnostic unit and a training unit. The training unit includes a plurality of historical error logs generated during abnormal operation or failure from a plurality of machines, and the actual fixes (repair solutions) associated with the abnormal events or failures. A block finding unit identifies sections of each error log that are in common with sections of other historical error logs. The common sections are then labelled as blocks. Each block is then weighted with a numerical value that is indicative of its value in diagnosing a fault. In the diagnostic unit, new error logs associated with a device failure or abnormal operation are received and compared against the blocks of the historical error logs stored in the training unit. If the new error log is found to contain block(s) similar to the blocks contained in the logs in the training unit, then a similarity index is determined by a similarity index unit, and solution(s) is proposed to solve the new problem. After a solution is verified, the new case is stored in the training unit and used for comparison against future new cases.

Maximum-likelihood parameter estimation for unsupervised stochastic model-based image segmentation

Abstract: An unsupervised stochastic model-based approach to image segmentation is described, and some of its properties investigated. In this approach, the problem of model parameter estimation is formulated as a problem of parameter estimation from incomplete data, and the expectation-maximization (EM) algorithm is used to determine a maximum-likelihood (ML) estimate. Previously, the use of the EM algorithm in this application has encountered difficulties since an analytical expression for the conditional expectations required in the EM procedure is generally unavailable, except for the simplest models. In this paper, two solutions are proposed to solve this problem: a Monte Carlo scheme and a scheme related to Besag's (1986) iterated conditional mode (ICM) method. Both schemes make use of Markov random-field modeling assumptions. Examples are provided to illustrate the implementation of the EM algorithm for several general classes of image models. Experimental results on both synthetic and real images are provided. >

Abrasive tool insert

Abstract: Disclosed is an abrasive tool insert having an abrasive particle layer having an upper surface, an outer periphery, and a lower surface integrally formed on a substrate which defines an interface therebetween. The abrasive particle layer outer periphery forms a cutting plane. The thickness of the abrasive particle layer at its outer periphery cutting plane decreases radially inwardly. Thus, the interface can have a sawtooth shape cross-sectional profile, at least one slot extending from said abrasive particle layer outer periphery radially inwardly, or other configuration based on the precepts of the present invention. Also, the angle of the outwardly sloping profile can be matched to the anticipated angle of the wear plane which will develop as the PDC wears in use.

An algorithm for self calibration from several views

Abstract: This paper gives a practical algorithm for the self-calibration of a camera from several views. The method involves non-iterative methods for finding an initial calibration for the camera, followed by least-squares iteration to an optimum solution. At the same time, a scaled Euclidean reconstruction of the scene appearing in the images is computed. >

Virtual internal cavity inspection system

Abstract: A virtual internal cavity inspection system non-invasively provides images of cavities of a subject from a viewpoint within the cavity. An acquisition unit acquires imaging information about internal structures of a subject. This imaging information is segmented into separate structures, and a 3D surface model is constructed. An operator views an image of the 3D model to select a goal viewpoint and a start viewpoint. A viewpoint path is created linking the start viewpoint and the goal viewpoint. Images are created with a viewpoints along the viewpoint path. A variety of additional visualization techniques aid the viewer's localization of the current image viewpoint, and its relation to the subject.

MR spectroscopy of the human heart: The status and the challenges

Abstract: Noninvasive measurements of high-energy phosphate metabolism in the anterior myocardium of heart patients are now possible with image-guided, localized nuclear magnetic resonance (MR) spectroscopy. The results, reviewed herein, are largely consistent with those of prior animal studies. Quantification with phosphorus-31 MR yields normal phosphocreatine (PCr) and adenosine triphosphate (ATP) concentrations of about 11 and 6 mumol per gram wet weight, respectively, with a PCr/ATP ratio of around 1.8. Studies of patients with hypertrophic and dilated cardiomyopathy, left ventricular hypertrophy, valve disease, transplanted hearts, myocardial infarction, or reversible ischemia reveal abnormalities in the PCr/ATP ratio and/or the metabolite concentrations. Differences in reported findings for cardiomyopathies might be attributable to statistical sensitivity and the presence of heart failure. The technique might find use in the clinic for identifying failure when other factors complicate diagnosis. The PCr/ATP r...

Speckle noise filtering in ultrasound imaging

Abstract: The enhancement of ultrasound images is provided through the filtering of signal dependent noise such as speckle noise by dividing the signal into selective subintervals and utilizing discrete wavelet transform and the identification and selection of those wavelet transform coefficients primarily including signal and not those primarily including signal dependent noise.

Predictive respiratory gating: a new method to reduce motion artifacts on CT scans.

Abstract: PURPOSE: To evaluate a gating system, called predictive respiratory gating (PRG), that reduces motion-induced artifacts on computed tomographic (CT) scans of patients who cannot suspend respiration. MATERIALS AND METHODS: PRG uses a respiration monitor and a new algorithm to predict when a motionless period is about to occur. It automatically starts scanning so the scan is temporally centered around the motionless period at end inspiration or end expiration. To demonstrate PRG, CT was performed on a motion phantom and a quietly breathing volunteer with and without gating. RESULTS: Scans of the phantom obtained with PRG contained less motion-induced streaking and blurring than did scans acquired without PRG. Scans of the volunteer gated at end expiration contained significantly less artifact than nongated scans (P < .03). CONCLUSION: PRG reduced motion artifact on scans of a spontaneously breathing volunteer. PRG may be able to reduce motion artifacts on scans of patients unable to suspend respiration.

High pressure gas generator rotor tie rod system for gas turbine engine

Abstract: An improved high pressure gas generator rotor for a gas turbine engine is disclosed in which a tie rod of unitary construction provides an axial compressive load across a plurality of non-bolted compressor and turbine components arranged in rotational driving arrangement, for example, by face splines and rabbets. An interim compressive load path solely through the compressor rotor portion is automatically provided upon relaxation of the operational compressive load in the rotor to maintain mechanical integrity of the compressor and facilitate assembly and maintenance activity. An anti-rotated midspan locknut on the tie rod obviates the need for additional, special tooling configured to clamp the compressor components during disassembly of the turbine.

Method of and apparatus for providing offset for light detector

Abstract: The invention provides a solid state light imager or x-ray detector including an array of rows and columns of elements, each element including a photo diode, which converts photons to an electrical signal, and a transistor. Each photo diode has a capacitance associated with it. The cathode of the photo diode in each element is connected to the source of the transistor in the element. The amount of charge removed from each photo diode, after exposure to light, is used to create an image. The image is capable of accurate measurement of charge removed from the photo diodes after the array has been exposed to light, using unipolar measuring circuitry, in spite of charge retention by the transistors and a problem caused by the combination of changes in row voltage and parasitic row to column capacitance.

Wireless radio frequency power semiconductor devices using high density interconnect

Abstract: A power device component package includes a substrate supporting a drain lead, a source lead, and a gate lead. Each of the leads comprises an electrically conductive material having a thickness sufficient to form a high current contact. A power device component with component pads has an electrically conductive backside supported by and electrically coupled to the drain lead. A dielectric layer overlies at least portions of the component, the source lead, and the gate lead and has a plurality of vias therein aligned with predetermined ones of the component pads and predetermined portions of the source and gate leads. A pattern of electrical conductors extends through selected ones of the vias, with a first portion of the pattern coupling selected ones of the component pads to the source lead and a second portion of the pattern coupling at least one other of the component pads to the gate lead.

Direct stacked and flip chip power semiconductor device structures

Abstract: Power semiconductor device structures and assemblies with improved heat dissipation characteristics and low impedance interconnections include a thermally-conductive dielectric layer, such as diamondlike carbon (DLC) overlying at least portions of the active major surface of a semiconductor chip, with vias formed in the dielectric layer in alignment with contact pads on the active major surface. A patterned metallization layer is formed over the thermally-conductive dielectric layer, with portions of the metallization layer extending through the vias into electrical contact with the chip contact pads. A metal structure is electrically and thermally coupled to selected areas of the patterned metallization, such as by solder bonding or by a eutectic bonding process. In different embodiments, the metal structure may comprise a metal conductor bonded to the opposite major surface of another power semiconductor device structure, a heat-dissipating device-mounting structure, or simply a low-impedance lead.

Magnetic resonance (MR) angiography using a faraday catheter

Abstract: A magnetic resonance (MR) angiography system employs a Faraday catheter for generating MR angiograms of selected blood vessels. A subject is first placed in a polarizing magnetic field. The Faraday catheter is then inserted into a selected blood vessel of the subject at or near the root of a vessel tree desired to be imaged. An MR imaging pulse sequence is then applied to the subject to obtain image information from the region containing the desired vessel tree. Fluid inside the Faraday catheter is shielded from the RF pulses of the MR imaging sequence allowing the fluid to be in a relaxed state, while tissue outside the Faraday catheter is on a steady-state. As the fluid exits the catheter, and before it reaches steady-state, it produces an increased MR response signal causing the desired vessel tree to be imaged.

Combustion control for producing low NOx emissions through use of flame spectroscopy

Abstract: Combustion in a gas turbine is controlled through use of flame spectroscopy in order to achieve low NO x emissions in the exhaust. By monitoring the combustion flame in the turbine to determine intensity of non-infrared spectral lines, and dynamically adjusting the fuel/air ratio of the fuel mixture such that this intensity remains below a predetermined level associated with a desired low level of NO x emissions, the engine produces significantly reduced NO x emissions in its exhaust but at a sufficiently high combustion flame temperature to avoid any undue risk of flame-out, thereby assuring stable, safe and reliable operation.

Method and apparatus for communicating with a plurality of electrical metering devices and a system control center with a mobile node

Abstract: A method and apparatus for transmitting signals according to the present invention between electrical metering devices and a system control center includes a mobile node. The mobile node communicates with the electrical metering devices operably connected to a distribution transformer and transmits the signals received from the electrical metering devices to the system control center while the mobile node is in the field and removed from the system control center. The mobile node may then be relocated in the field within the electrical power distribution system so as to communicate with the electrical metering devices operably connected to another distribution transformer. Thus, a single mobile node may communicate with the electrical metering devices connected to a number of distribution transformers so as to decrease the number of fixed nodes employed by a communications system of an electrical power distribution system.

Mechanical positioner for magnetic resonance guided ultrasound therapy

Abstract: A positioner for a magnetic resonance (MR) surgery system which positions a focal point of an ultrasound transducer to selectively destroys tissue in a region within a patient. The positioning means moves an ultrasound transducer under the control of an operator. Mechanical threaded shafts and slides act as screw drives causing several connected slides to move the ultrasound transducer in three dimensions. Expanding shafts are connected between a fixed point on a housing and the actuating point of the threaded shafts. Two of the expanding shafts employ universal joints allowing the shafts to rotate as they follow the slides. The third expanding shaft need only expand but the relative angle between its attachment points does not change, thereby eliminating the need for universal joints. An MR imaging system employing a temperature sensitive pulse sequence, creates an image of the tissue and the region being heated to allow the operator to adjust the position of the ultrasonic transducer so as to direct ultrasonic energy to the appropriate location.

Method for transforming relational data base schemas into object models using ideal table meta models

Abstract: An algorithm for transforming data base schema information to object modeling notation utilizes meta models of the data base tables and the target object modeling notation respectively to bridge the gap between the data base schema representation and the object model representation. Detection of associations between classes of objects is performed for one-to-one, one-to-many, and many-to-many associations by analyzing unique key attributes. Once an object meta model is populated, the underlying object model may be displayed using existing software packages.