Abstract: A fan assembly has a fan motor and first and second generally identical and spaced apart fans each rotationally attached to the fan motor to turn at the same rotational speed. Each fan has an equal number of generally identical fan blades and produces noise including a tone having a frequency equal to its rotational speed times its number of fan blades. The fan blades of one fan are angularly offset at a relative phase angle with respect to the fan blades of the second fan such that the tones of each fan generally cancel each other out. An equation is provided for a ducted fan assembly relating the relative phase angle to the rotational speed of the fans, the number of fan blades of each fan, the geometry of the duct, and the speed of sound in air within the duct.

Abstract: An ultrasonic transducer employed for both transmitting ultrasonic acoustic energy into an immersion medium and for detecting acoustic energy reflected from an object under examination is provided, the transducer having a hybrid transmitter and receiver in which a ceramic piezoelectric material is used to construct a first piezoelectric element for transmitting the acoustic energy, and a polymer piezoelectric material is used to fabricate a second piezoelectric element for receiving the reflected acoustic energy. The hybrid ultrasonic transducer provides improved performance over prior transducers using only a single ceramic piezoelectric element, in that the good transmitting properties of the ceramic are preserved, while the better receiving properties of the polymer piezoelectric are used to improve the sensitivity of the transducer. The polymer piezoelectric has the further advantage of providing a closer match of acoustic impedance to the immersion fluid used in the evaluation of objects.

Abstract: Complete cone beam scanning and data acquisition techniques are provided for three-dimensional computerized tomography imaging of an object. Such techniques include defining a source scanning trajectory such as a helical path located on a cylindrical surface which surrounds a field of view that contains the object. The foregoing scanning trajectory allows using area detectors having a predetermined dimension (such as height or width) substantially smaller than the corresponding dimension of the object to be imaged.

Abstract: Techniques and system for processing cone beam projection data for reconstructing substantially free of boundary-induced artifacts a three-dimensional computerized tomography (CT) image of a portion of an object are provided. Such techniques include suitably identifying a rotation center shared by a line of integration pair and wherein the rotation center is selected for mapping, within a cone beam masked region identified on a surface array detector, predetermined points situated along the line of integration pair. The suitably identified rotation center allows to acquire cone beam projection data within the masked region which is free of boundary effects. The acquired data is retained for subsequent processing and thus allows for exactly reconstructing the substantially free of boundary-induced artifacts CT image.

Abstract: An improved method and apparatus for preprocessing cone beam attenuation data to reconstruct a three dimensional image of a particular region of interest of an object by a process of inverse Radon transformation is described. The number of required operations is substantially reduced by selectively retaining for further processing only that cone beam attenuation data acquired within a select closed region of the surface of the array detector wherein this region provides data corresponding to beams actually attenuated in passing through the region of interest of the object. In this manner, unnecessary beam attenuation data is discarded at the earliest possible opportunity to expedite image processing.

Abstract: An eddy current probe array is disclosed comprising a plurality of spatially correlated eddy current probe elements sufficiently disposed within a flexible interconnecting structure to collect a discrete plurality of spatially correlated eddy current measurements for nondestructive near surface flaw detection. A plurality of precisely fabricated, substantially identical elements being sufficiently distributed can accommodate inspecting an area of conductor covered by the active width of the array in a single uni-directional scan. The array structure can flexibly conform to accommodate inspection of large, irregular, curved conductive surfaces which cannot be inspected by conventional means.

Abstract: A technique for injecting corpus-based preference into syntactic text parsing is provided. Specifically, the problem of tagging content-word pairs by part-of-speech is solved by using thematic analysis. A new measure of the fixed or variable nature of such word pairs is created and used to classify word pairs as either noun-verb, adjective-noun, or verb-noun.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied.

Abstract: A method and apparatus for exact three dimensional reconstruction of the image of a portion of interest of an object in the field of view of a cone beam source is disclosed, whereby unwanted Radon data are selectively disgarded avoiding undue corruption of the imaging process and missing Radon data that would otherwise be lost are selectively recovered. This is accomplished by ensuring the acquisition of a complete set of Radon data through proper choice of scanning configuration, then selectively partitioning and manipulating the acquired data to image only the select portion of interest of the object.

Abstract: An open magnetic resonance imaging (MRI) magnet having first and second spaced-apart superconductive coil assemblies connected by spaced-apart structural posts each having a first end portion attached to the coil form of the first coil assembly and a second end portion attached to the coil form of the second coil assembly. Each toroidal shaped coil form has radially spaced-apart inner and outer generally cylindrical shells and has longitudinally spaced-apart inner and outer annular plates each attached to the inner and outer cylindrical shells. A superconductive coil surrounds, and is attached to, the outer surface of the outer cylindrical shell.

Abstract: An out-of-balance condition detecting system with a lid actuated switching assembly for interrupting operation of a washing machine upon detection of an out-of-balance (OOB) condition or upon a lid of the washing machine being open. The system includes pneumatic generating units for generating a predetermined fluidic pressure in response to excursions of a tub of the washing machine during a spin cycle; an actuator which is fluidly coupled to such generating units for providing an actuating position corresponding to the OOB condition; and a switching assembly which includes a switch responsive to the actuator in its actuating position to interrupt the OOB condition. The switch is further responsive to the lid to deenergize the motor upon the lid being in an open position. The switch which can be either mechanically or magnetically actuated may be designed such that once the OOB condition has been detected, a user is required to open the lid in order to reset operation of the washing machine.

Abstract: A system and method are provided for detecting and interrupting an out-of-balance (OOB) condition in a washing machine. The system includes pneumatic generating units for generating a predetermined fluidic pressure in response to excursions of a tub of the washing machine during a spin cycle; an actuator which is fluidly coupled to such generating units for providing an actuating position corresponding to the OOB condition; and a switch responsive to the actuator in its actuating position to deenergize a motor which spins the basket for holding the articles to be cleansed and thereby interrupt the OOB condition.

Abstract: A trim system reduces NO.sub.x output from a cannular gas turbine by trimming fuel flow rates to equalize the fuel-air ratio in each combustor can. The system includes a main valve fluidly connected to the fuel inlet of each can and a trim valve fluidly connected to each fuel inlet in parallel with the main valve. Each trim valve has a flow resistance which is about 30-100 times greater than the flow resistance of each main valve. A controller is provided for controlling the opening of the trim valves in response to the level of NO.sub.x emitted from the gas turbine. The controller receives a signal corresponding to the NO.sub.x emissions from a NO.sub.x sensor and outputs suitable control signals to the trim valves. In one preferred control scheme, the controller sequentially perturbs the fuel flow rate to each can and monitors the resulting changes in NO.sub.x emissions. The controller establishes influence coefficients for each combustor can which are defined as the ratio of the change in NO.sub.

Abstract: Disclosed are methods for processing and interpreting data acquired from an eddy current probe array inspection system, based on a background subtraction technique. Test and reference waveform data sets are acquired, and subsequently combined. However, the data sets are first normalized and registered to the same position, registering on characteristic signals produced when scanning over edges. Specific techniques are disclosed for normalizing, correcting for spatial offsets, determining the actual locations of edge signals by peak detection and correlation, and adjusting for variations in the number of points in the test and reference data sets.

Abstract: An improved eddy current probe array having means to compensate the entire array for varying different element liftoff, is described. An array consisting of a plurality of sense elements and means for compensating these sense elements is scanned across an inspection surface to produce respective scan responsive signals wherein the scan responsive signals of the sense elements are proportionately normalized or calibrated against the scan response of said compensating means during routine signal processing of the array signals in order to compensate for any lift off experienced by the sense elements. Array lift off compensation is attributable to sense element design cooperating with at least one lift off compensating sense element and a method of normalization/calibration performed during signal processing of the array signals.

Abstract: An active noise control system which minimizes noise output by creating a secondary, cancelling noise field using vibrational inputs. The system includes one or more piezoceramic actuators mounted to the inner surface of the shroud of an aircraft engine. The actuators can be either mounted directly to the shroud or to one or more noise cancelling members which are resiliently mounted the shroud. Transducers are also provided for sensing the noise generated by the engine and producing an error signal corresponding to the level of noise sensed. A controller sends a control signal to the actuators in response to the error signal, thereby causing the actuators to vibrate and generate a noise field which minimizes the total noise emanating from the engine. The piezoceramic actuators can be thin sheets of piezoceramic material or can be in the form of a piezoelectric-driven mechanical lever arrangement.

Abstract: A trim system reduces NO.sub.x output from a cannular gas turbine by trimming fuel flow rates to equalize the fuel-air ratio in each combustor can. The system includes a main valve fluidly connected to the fuel inlet of each can and a trim valve fluidly connected to each fuel inlet in parallel with the main valve. Each trim valve has a flow resistance which is about 30-100 times greater than the flow resistance of each main valve. A controller is provided for controlling the opening of the trim valves in response to the level of NO.sub.x emitted from the gas turbine. The controller receives a signal corresponding to the NO.sub.x emissions from a NO.sub.x sensor and outputs suitable control signals to the trim valves. In one preferred control scheme, the controller sequentially perturbs the fuel flow rate to each can and monitors the resulting changes in NO.sub.x emissions. The controller establishes influence coefficients for each combustor can which are defined as the ratio of the change in NO.sub.

Abstract: Apparatus and method for regenerating saturated adsorbents using microwave energy. A saturated adsorbent, such as activated carbon, is fed onto a continuously moving conveyor belt. The conveyor belt transports the carbon to a microwave cavity where the carbon is exposed to microwave energy. The cavity is defined by a containment enclosure which is sealed to prevent radiation leakage. The carbon is heated to a sufficient temperature to cause the contaminants to desorb. The system also includes vents for removing the desorbed contaminants and a holder for receiving the treated carbon discharged from the belt. The microwave cavity may be divided into a number of heating compartments so that the carbon on the belt is heated to different temperatures in each compartment. Each compartment is separately vented, thereby allowing selective recovery of the different contaminants in the carbon.

Abstract: This invention relates to a sensor for monitoring the operation of a suction-type shot peening machine. Such structures of this type, generally, measure the vacuum in the gun mixing chamber of the suction-type shot peening machine. Changes in this sensor will be indicative of either gun surging or changes in shot delivery rate or velocity. Its output will, therefore, provide diagnostic information on the performance of the process.

Abstract: A method and apparatus for acquiring scanning cone beam projection data along a three dimensional scanning trajectory is disclosed. The technique ensures acquisition of a substantially uniform distribution of Radon data that is sufficiently complete for exact image reconstruction of an object irradiated by a scanning cone beam source. By choosing a scanning trajectory whose planar projection onto a plurality of coaxial planes, when taken together, forms a continuous, convex, closed curve about a corresponding projection of the object being scanned; the Radon information obtained therefrom is complete and information coverage is uniform over the region of support of the object. Accordingly, this condition provides a practical, easy to implement, visual method for evaluating candidate three dimensional scanning trajectories.