Abstract: A nuclear magnetic resonance (NMR) logging technique reveals the volume of hydrocarbons in an earth formation. The differences in viscosity among gas, oil and water are used to distinguish among these three fluids. During NMR logging, a parameter of a sequence of magnetic field pulses is altered, causing echo signal strengths to vary due to the diffusion of the fluids in the formation. The volume of hydrocarbons in the formation is determined from detected spin echo strengths. The invention applies to wireline NMR logging and NMR logging-while-drilling techniques.

Abstract: The present invention features a method and a fixture for determining the asymmetrical character of a readhead prior to its installation in a check-validation machine. Such a machine that is used to validate checks uses a stepper motor drive to convey the check past the readhead. The magnetic field produced by the coil of the stepper motor interferes with the capability of the readhead to recognize the magnetic indicia on the check. Once determined, the asymmetrical sensitivity of the readhead towards the magnetic flux allows the manufacturer to mount the readhead with its sensitive side away from the stepping motor of the validating unit. The readhead asymmetry is determined by the method of this invention by measuring an output voltage pulse of the readhead, when it is excited by magnetic pulses both forward and rear of its read gap. The excitation is provided approximately one inch from the read gap.

Abstract: An overall process in which a boring tool is moved through the ground within a given region along a particular path from a specific starting point is disclosed herein. A method of establishing and graphically recording the location of at least a portion of the particular path taken by the boring tool within the given region is also disclosed herein along with and with respect to a reference path which may change with time and vertical survey reference path which will remain unchanged with time.

Abstract: In order to exclude disturbing influences in the determination of the axle-related speeds of railway vehicles, the signals generated by the passage of the last axle of a bogie are discerned from spurious signals. This is carried out by specifying a time window within which the last axle of a bogie must have passed the measuring zone. Those signals separated by about the same offset time as the time between the passage of the first axle of the first and second sensors are used for the determination of the speed of this last axle. An additional integrity check further increases the reliability signal identification by comparing the sum of certain measured time values which have been detected by the two sensors of the measuring zone. The assignment of the time values respectively to the pulse centers of the event indication eliminates different response tolerances of the sensors due to the lateral offset of the vehicle wheels with respect to the rails in the region of the sensors.

Abstract: A magnetostrictive wire waveguide type position measuring system wherein the wire waveguide is mounted within a small diameter brass tube which, in turn, is mounted by way of resilient suspension components within a rigid outer tube affixed to a position reference frame. The suspension system prevents relatively high frequency shock inputs characteristic of rough environment applications from reaching the waveguide. The position signal is derived from output signal quantities generated by the propagation times of sonic disturbances from a first reference magnet held in a fixed position relative to the outer housing and a second user magnet which moves relative to the outer housing with the element or quantity being monitored.

Abstract: Techniques for conducting two-dimensional fat-saturated multislice MR studies are disclosed. The frequency of saturation pulses is varied on a slice-by-slice basis. In a second preferred embodiment, the phase, or the phase and frequency, of one or more elements of a spatially and spectrally selective MR pulse sequence are varied on a slice-by-slice basis. In a third preferred embodiment, the order in which MR image data is acquired from a plurality of slices is changed so as not to minimize the time between inadvertent saturation of the water signal in a particular slice and the acquisition of MR image data from that slice.

Abstract: A process for detecting metallic or other electrically conducting objects in essentially flat search areas by means of at least one search probe which generates search signals is presented. The probe is guided relative to the search area parallel to its surface, along a search path situated in a search surface. By at least one analysis unit coupled with the search probe, the search signals are automatically correlated with the positions of the search probe on the search surface, as determined by localizing devices. The correlated data are converted to an image of the objects in the search area, such as an object map.

Abstract: A device for excitation and detection of magnetic resonance is presented. The device is fashioned on the principle that electromagnetic radiation is effectively described by fewer independent parameters on considering its interaction with `spins` in a magnetic field, than would be the case in vacuum. In particular, the amplitude and phase of electromagnetic radiation are not independent of each other under such conditions. Complex pulse envelope shapes for excitation may be generated with this device either by pure amplitude modulation, or by pure phase modulation alone instead of by both amplitude and phase modulation). In the latter option, stable, efficient, low-droop Class `C` amplifiers and standard rectangular pulse envelopes may be employed, instead of linear Class `A` or `AB` amplifiers and complex em pulse envelope shapes. In detection mode, signal may be picked up from either one or both of the coils.

Abstract: A rotation sensor has a target wheel including first and second tracks and a dual-element magnetoresistive sensor. Each individual magnetoresistive element is aligned with a respective track of the target wheel to provide substantially inverse resistive changes with the passage of the wheel. One of the tracks is characterized by alternating high and low permeability, such as by a toothed section, and the other of the tracks is characterized by invariant permeability.

Abstract: A nuclear magnetic resonance apparatus including a magnet generating a static magnetic field in a first region containing materials to be analyzed. The magnet generates zero static magnetic field in a second region. The magnet has generally homogeneous magnetization along a longitudinal axis and is magnetized substantially perpendicular to the axis. The apparatus includes means for generating a radio frequency magnetic field in the first region for exciting nuclei of the materials. The means for generating the radio frequency magnetic field includes an antenna disposed within the second region. The apparatus includes means for receiving a nuclear magnetic resonance signal from the excited nuclei. The means for receiving also provides an output indication of properties of the materials to be analyzed. In a preferred embodiment, the means for generating and receiving include an antenna at least partially disposed within the second region.

Abstract: The instruments of a pulsed nuclear magnetic resonance (NMR) device are included in a drill collar for evaluating earth formations. The resulting tool makes NMR measurements while the formation is being drilled. Permanent magnets produce a static field in the earth formation. Shimming permanent magnets inside or outside the drill collar suppress the magnetic resonance of borehole fluids. The permanent magnets are manufactured from two magnetic materials, for example.

Abstract: A method of phase unwrapping by solving the Poisson equation using a weighted iterative algorithm, for use when separating spectral component with magnetic resonance imaging systems. The solution of the Poisson equation is expedited by using a weighting matrix obtained by calculating the average noise level of an in-phase image and using 3-5 times the noise level as a threshold with only pixel intensity levels above the threshold being set equal to one and the other pixels being set to zero. The pixels on the weight matrix are also set to zero according to the size differences of the phase offset per pixel either in the row or column direction. The solution of the Poisson equation is then uniquely operated on to remove a constant (bias) and to improve the fit.

Abstract: The current supply of a gradient coil in a magnetic resonance tomography apparatus with a gradient amplifier and a connectable capacitor that can be interconnected with the gradient coil to form a series resonant circuit. The gradient amplifier produces at least a part of the voltage needed for driving a predetermined gradient current through the gradient coil. The resonant frequency of the capacitor in combination with the gradient coil is lower than 1/4 T.sub.r, whereby T.sub.r is the duration of a leading or trailing edge of the gradient current.

Abstract: A method of establishing the location of at least a portion of a particular path taken by a boring tool within a given region is presented. The method includes the steps of establishing a reference path within the region and providing a portable locator and means located partially at and forming part of the boring tool and partially at and forming part of the locator for generating certain information about the position of the boring tool relative to the position of the locator. When the boring tool reaches various spaced apart measuring locations as it moves along the particular path, at each such measuring location, the locator is positioned on the reference path at an associated reference point which is specifically determined by the position of the boring tool at the associated location on the particular path.

Abstract: A simple, pore-level model for diffusion and NMR relaxation of oil-water mixtures in water wet pores has been developed. In addition to lending physical insight into the relaxation time behavior of mixed pore fluids, the model can be used to generate a practical tool for interpreting diffusion log data, i.e., a T2 vs. D cross plot. Locating points on the cross plot simultaneously yields the near wellbore water saturation and the rock pore size. For light oils, T2 is shown to be mainly a pore size indicator whereas D is controlled mainly by Sw. The pore size "resolution" decreases as oil viscosity and/or Sw decreases. A preliminary verification of the model has been made with limited core data and the results of applying the model to interpreting NMR log data are encouraging.

Abstract: An apparatus and method for determining a property of a sample, derived from a response obtained from the sample after an electrical pulse has been applied to it. Blood cells are subjected to an electrical pulse, a response is obtained using data retrieval means and a Fourier Transform is applied to the response. As the pulse applied is of very short duration (ideally a Dirac pulse) the Fourier transform yields information across a very broad bandwidth, typically several MHz, and accordingly a wide range of frequency response data is obtained. Certain cellular defects can be deduced from the transformed data. A detector is provided to detect precisely the presence of a cell as it passes through a particular region of an oriface. This is then used to trigger the pulse at a precisely controlled instant. This reduces the effect of random dispersion and can be adapted to ignore noise peaks which inevitably occur.

Abstract: A detector device delivering a signal representative of the respiration of patient, adapted to be used in a charged and sensitive electromagnetic environment. The device is principally constituted by at least two non-metallic electrodes (1) and by a unit for the processing of electrical signals emitted by the heart, comprising a first module (5) for acquiring and shaping cardiac electric signals, a second module (6) for extraction of the respiratory signal, and a third module (7) for electro-optical conversion of this latter, the modules being disposed in a shielded casing (8) forming a Faraday cage and, finally, by an optical connection (9) connecting the casing (8) to at least one other apparatus or device.

Abstract: A magnetic field sensor is composed of layered magnetoresistive elements which are arranged in a bridge on a substrate. The magnetoresistive elements comprise two ferromagnetic layers which exhibit an uni-axial anisotropy in one plane and are separated by a non-ferromagnetic layer. During the manufacture of the sensor the magnetization directions of these ferromagnetic layers are laid down so that two elements in two adjacent branches of the bridge exhibit an opposed sensitivity to external magnetic fields. Moreover, in each magnetoresistive element the magnetization of a ferromagnetic layer is adjusted substantially perpendicularly to the magnetization direction of the other ferromagnetic layer. As a result auxiliary fields are no longer required for the measurement of small magnetic fields and the sensor is substantially free of hysteresis and has an enhanced linearity.

Abstract: A bolus of magnetized blood is formed by at least two radio frequency magnetic fields, and readout gradient magnetic fields are repeatedly applied at a proportion of 1:-2:1 along a blood vessel so as to continuously obtain a first echo signal whose phase change due to velocity is corrected, from the moving bolus. This first echo signal provides velocity information on the blood stream. The sequence of the readout gradient magnetic fields is repeatedly applied at a proportion of (.sqroot.2-1):-2:2:-(.sqroot.2-1) so as to continuously obtain a second echo signal whose phase change due to velocity and acceleration is corrected, from the moving bolus. Acceleration information of the blood stream is extracted by calculating the difference between the first echo signal and the second echo signal. The velocity information and/or the acceleration information is displayed in superposition with a specific blood vessel of an angiogram shot in advance.

Abstract: A logging apparatus is provided for use in a wellbore for measuring an attribute of at least one of the wellbore and a surrounding formation, when coupled to a wellbore tubular expended in the wellbore. The logging apparatus includes a housing, at least one transmitter, and at least one receiver. The transmitter is carried by the housing and is individually and selectively operable for producing electromagnetic interrogating signal at selected interrogation frequency for passage to the wellbore and surrounding formation. The receiver is carried by the housing in a selected position relative to the transmitter, and is tuned to receive electromagnetic signals at the interrogation frequency to the exclusion of other frequencies.