Abstract: A circuit for detecting the position of a radio frequency (RF) coil assembly in a magnetic resonance (MR) scanner includes, in the preferred embodiment, a normally closed switch connected to ground in parallel with a PIN diode which forms part of a transmit/receive (T/R) switch used to selectively couple the RF coil assembly to an RF power amplifier and an RF receiver preamplifier. The switch is operable by an actuating rod mounted to the RF coil assembly structure, whose position is to be sensed, such that when the assembly is in place the switch contacts are closed, and open when the assembly is not in place. The opening and closing of the switch shunts the PIN diode in and out, respectively, of the T/R switch circuit, thereby changing the voltage drop across other PIN diodes in the circuit. This change is sensed by a comparator circuit, the output of which is indicative of the RF coil assembly position.

Abstract: A light weight, low speed, low cost dynamic balancing machine useful for wheel balancing includes a light weight base, sensors for detecting unbalanced signals and attendant noise, and a low energy drive employing a small electric motor driving elastic belts for rotating the body to be balanced.

Abstract: The gradient coil system for a nuclear spin tomography installation encloses a hollow cylindrical support body, the cylinder axis of which extends in the z direction of an orthogonal x-y-z coordinate system with the coordinate origin in the imaging center, in which direction also the magnetic field B.sub.z of a base generating a field gradient G.sub.z, at field magnet is oriented. The gradient coil system contains for least two ring-shaped individual coils which are arranged symmetrically to the x-y plane extending through the imaging center, and furthermore, pairs of saddle-shaped individual coils arranged symmetrically to this plane, for generating field gradients G.sub.x and G.sub.y. In this gradient coil system, the sound level caused in the hollow cylindrical support body is reduced by rigidly connecting the prefabricated G.sub.x and G.sub.

Abstract: A cavity resonator serves to generate magnetic dipole transitions in a sample, for instance for carrying out electron spin resonance measurements. The natural frequency of the cavity resonator (10) is influenced by a reduction in length of the E flux lines. To this end, conductive areas (20) are arranged at the points where the E flux lines are encountered. This results in an increase of the space factor, related to an unchanged specimen volume, and thus in an improvement of the measuring sensitivity.

Abstract: A method of detecting hazardous line voltages over a two-wire line for transferring digital information. At one end, the line is terminated by a hybrid coupler (G) and an apparatus for adaptive echo elimination. This apparatus generates a digital signal (d) constituting an unambiguous measure of the difference between the line impedance (Z.sub.L) and the hybrid impedance (Z). This signal is compared with two digital limiting values (d.sub.1,d.sub.2) an alarm being given should either these two values be reached or exceeded.

Abstract: A housing (A) which is connected with an internal combustion engine to be vibrated therewith. A diaphragm (B) is mounted in an interior chamber of the housing to undergo vibration therewith. The diaphragm is constructed to have a natural resonant frequency which substantially matches the knock frequency of the engine model for which the knock sensor is designed. The diaphragm is mounted to the housing by a central portion (20) such that an edge portion (24) undergoes maximum resonant displacement. To facilitate the passage of air from one side of the diaphragm to the other during near resonant displacement, a plurality of apertures (26) are provided through the diaphragm edge portion. In this manner, viscous drag is reduced which increases the magnitude of the resonant displacement and decreases the bandwidth or range of frequencies over which the diaphragm undergoes significant displacement.

Abstract: Method and apparatus to estimate the weight of the trees and logs in a stand of trees before harvesting to maximize the efficiency of aerial logging are disclosed. A hydrometer that has a chamber which accepts a small known volume core from the tree determines the density thereof. Statistical modeling permits weight estimations for the entire stand based on this density and other conventional information about the stand of trees.

Abstract: A patient alignment system utilizes stationary and mobile light fan beams for precisely positioning a patient for performing NMR studies. One assembly of preferably laser light sources is utilized to create a visible reference point for aligning a patient anatomical reference in the staged scan position. The reference position is then used as a reference to locate the scan volume and to automatically translate the patient so that the scan volume is in the optimum homogeneous region of the polarizing magnetic field. Two laser assemblies, each separately operable to provide a vertically movable laser fan beam, are used to locate a vertical reference point. The vertical reference point is used to retrospectively reconstruct images centered in the field of view. The vertical reference point is used to obtain prospectively image data to reconstruct magnified zoom or unmagnified images offset from the isocenter.

Abstract: A method and apparatus are set forth for measuring flow velocity of an element of interest in a compound within a pipe. In the preferred and illustrated embodiment, a static magnetic field is imposed on the flowing material of interest. Preferably, a uniform field of finite width is imposed. There is a first coil around the path for imposing an RF magnetic field at right angles to the static magnetic field. There is a relationship between the flowing material including the element, frequency of the RF field and static magnetic field intensity which aligns nuclei or electrons of the element. There is a second (detection) coil spaced downstream from the first coil, the second coil also being around the pipe. By turning the first coil off or on, the NMR or EMR signal observed at the second coil can be made to change abruptly as the "tagged" element flows to the second coil. By measuring the time of travel of the element of interest evidenced by the second coil signal, the flow velocity can be measured.

Abstract: A nuclear magnetic resonance spectrometer includes a device for sensing the angular position of the sample tube and a device for adding up the free induction decay signals. The RF pulses are applied to the sample according to the output signal from the sensing device when a certain location of the sample tube is at a first specific position and also when the certain location is at a second position diametrically opposite to the first position. The two free induction decay signals obtained in this way are added up by the adding device to prevent occurrence of peaks, known as spinning sidebands, at positions shifted from the peaks of an NMR spectrum by integral multiples of the rotational frequency of the sample when the axis of rotation of the sample tube does not coincide with the central line of the sample.

Abstract: A borehole gravimetry survey is carried out by making gravity measurements at a plurality of measurement stations along an interval of the borehole. A moving average gradient is determined for gravity measurements taken from consecutive pairs of such measurement stations over the borehole interval. Each moving average gradient is inverse filtered to reduce the effect of the weighted averaging on the gravity measurements, thereby increasing the vertical resolution of the data.

Abstract: A magnetic shielding member is provided, according to one aspect of the invention, which can be used to effectively shield a borehole core from ambient magnetic fields during drilling of a core specimen from the borehole core. The shielding member comprises a first portion and a second portion, wherein the first portion is hollow and has a first opening in a wall thereof, and wherein the second portion is hollow and includes a sidewall which extends outwardly from the exterior surface of the first portion so as to surround the first opening. The second portion sidewall extends to an open end which defines a second opening. Each portion is constructed of a high permeability ferromagnetic material having permeability characteristics herein defined. In use, a borehole core is positioned in the chamber defined within the first portion, and a drill bit is inserted through the first and second openings so as to extend into the chamber and come into cutting contact with the borehole core.

Abstract: The volume of interest is excited. An array of pickup coils with water cores provide an array of signals whose frequencies indicate the magnetic field distribution. These frequencies are estimated and used to produce controlled magnetic field inhomogeneities which substantially cancel the undesired inhomogeneities in the field. The control signals can be stored and updated with each subsequent excitation.

Abstract: A method and apparatus for measuring vibrational forces emitted by a reaction wheel assembly during rotation of its rotor includes a low mass carriage (12) supported on a large mass base (10). The carriage (12) is in the form of an octagonal frame having an opening which is adapted for receiving the reaction wheel assembly (W) supported thereon by means of a mounting ring (22). The carriage (12) is supported on the base (10) by means of air bearings (A) which support the carriage in a generally frictionless manner when supplied with compressed air from a source (50). A plurality of carriage brackets (34) and a plurality of base blocks (30) provide for physical coupling of the base (10) and carriage (12). The sensing axes of the load cells (B) are arranged generally parallel to the base (10) and connected between the base and carriage such that all of the vibrational forces emitted by the reaction wheel assembly (W) are effectively transmitted through the sensing axes of the load cells.

Abstract: In an MRI system of the present invention, data of a reconstruction starting point, a sampling interval of projection data for respective lines along a specific line direction in a reconstruction image matrix and a predetermined correction coefficient value of the projection data are transferred to a constant generating circuit. In response to these data, the data of the sampling interval and the correction coefficient value for the specific line direction by every projection are generated, and the reconstruction starting points of the respective lines are sequentially generated. An output from the constant generating circuit is supplied to a reconstructor. In the reconstructor, the sampling interval is added to the reconstruction starting point, thereby obtaining reconstruction sampling positions of the projection data for the line direction corresponding to the reconstruction starting point.

Abstract: Advanced analytic methods and formulas have been developed for 2- and 3- mineral solutions in complex lithology reservoirs. Required logs are density, neutron, acoustic, and photoelectric absorption index (PE curve). On the basis of developed mathematic models of complex reservoirs the limitations and maximum possible errors in the determination of porosities and lithologic compositions are presented for each method. In most cases, the formulas developed are simple enough to be used with programmable calculators.

Abstract: A cylindrical coil for providing a magnetic field having a substantially linear gradient in an axial direction within the volume of the cylinder, as can be utilized in NMR apparatus, includes a cylindrical coil support structure and electrically conductive winding turns wound on the outer surface of the support structure. The winding turns are electrically insulated from each other and are located such that the axial density of the winding turns increases linearly from the center of the coil to each axial end thereof. Preferably, the winding turns are located so that the angular position .phi. of the spiral path of the windings on the surface of the cylindrical support structure satisfies the relationship determined by the equation ##EQU1## The coil may also include additional electrically conductive winding turns for compensating for variations in the linearity of the magnetic field gradient which are due to the coil being of finite length.

Abstract: A method and apparatus for establishing the rate at which fluid is transferred between an offshore well 16 and the formations 20 surrounding the well 16 in the course of drilling the well 16 from a floating drilling rig 14. A drilling fluid handling system 31 is used to inject drilling fluid into the well 16. A marine riser 22 extending from the sea bottom 18 to the rig 14 is provided to return the drilling fluid to the rig 14. The riser 22 is provided with a slip joint 26 to accommodate wave induced heave of the rig 14. Inflow and outflow flowmeters 42,44 are provided to monitor the rates at which drilling fluid is injected into the well 16 and returned to the rig 14. The return flow rate signal is filtered to mitigate the cyclical variations resulting from extension and contraction of the slip joint 26. A signal processing system 46 is provided to maintain the time constant applied in the filtering process at an optimum level as the rate and magnitude of rig heave varies with time.

Abstract: A method of determining the minimum level of enrichment required to render a substantially miscible gas miscible in a liquid hydrocarbon by observing the behavior of liquid hydrocarbon droplets as they fall through samples of enriched gas of incrementally increasing levels of enrichment. The lowest level of enrichment at which the droplet is observed to dissipate in the enriched gas is the minimum level of enrichment.

Abstract: Method of dynamic balancing of rotating machines in assembled condition, the machines being symmetrical to their center of weight. The effective value of the speed of radial vibrations arising from unbalance when the machine is running at no-load speed and is vibro-isolated from the surrounding media are measured by measuring the relative acceleration phases of the vibrations. Correction masses are estimated for each balancing plane by dividing the measured effective speed values by a constant characterizing the machines of a given type, which is determined beforehand. When the machine is dismantled, correction masses are placed in the balancing planes at angles obtained from the determined relative acceleration phases plus 270.degree. they added along the directional rotation of the rotor of the machine. These angles are measured according to a mark on the shaft of the machine.