Abstract: A treatment fluid containing bio-fibers composed of fibrous structural protein, such as keratin, which demonstrates the ability for proppant transport, resistance to degradation in the presence of many degradants, and selective degradation to other degradants. Methods of using the treatment fluid include introducing the treatment fluid in a well bore and selectively degrading one or more of the treatment fluid components.

Abstract: A thermocouple probe 10 suitable for use in a gas turbine engine comprises a thermocouple element 12 which is coaxially arranged inside a protective sheath 16. The thermocouple element 12 is resiliently supported by a helical member 18 which insulates the element 12 from deleterious vibrations induced in the sheath 16. In use, the thermocouple probe 10 projects through an aperture 30 in the casing 32 of a gas chamber 34. Vibrations in the probe 10 are further reduced by ensuring that the longitudinal axis AA of the probe is angularly offset from the central axis BB of the aperture 30, such that the outer periphery of the sheath 16 is in contact with the inner periphery of the aperture 30 in two diametrically opposite and axially offset locations.

Abstract: A thermocouple probe 10 suitable for use in a gas turbine engine comprises a thermocouple element 12 which is coaxially arranged inside a protective sheath 16. The thermocouple element 12 is resiliently supported by a helical member 18 which insulates the element 12 from deleterious vibrations induced in the sheath 16 by alternately contacting the protective sheath (16) and the thermocouple element (12).

Abstract: In a micromachined silicon pressure sensor comprising a resonantly vibratable beam supported on a diaphragm, the beam is indirectly excited into resonant vibration by directing an optical excitation signal at the beam resonant frequency onto a part of the sensor other than the beam, preferably the diaphragm. Preferably, the optical excitation signal is of a wavelength to which the sensor is fairly transparent, and is directed through the beam and diaphragm to be absorbed by a suitable coating on the underside of the diaphragm. The optical excitation signal produces local heating, and the resulting expansions and contractions at the beam resonant frequency propagate through the sensor structure to excite the beam into resonant vibration. Another optical signal is used to detect the frequency of vibration of the beam, and a positive feedback loop maintains the frequency of the excitation signal equal to the detected beam vibration frequency.

Abstract: It is proposed to store spent nuclear fuel elements in welded-shut steel containers, which are filled with argon at about 2 atmospheres pressure. It is desirable to be able periodically to check the containers for leaks. The invention proposes to do this by providing apparatus for sensing the pressure within the container from outside the container. To achieve this, a pressure responsive bellows is mounted inside the container, such that changes in the container pressure move a metal plate attached to the bellows towards or away from a portion of the inside wall of the container. Then, if the container starts to develop a leak, the pressure will begin to drop, and the gap between the metal plate and the wall will change. This gap can be sensed from outside the container, by an ultrasonic pulse echo technique. Preferably, the bellows and plate are mounted within the head of the combined valve and lifting pintle by which the container is sealed.

Abstract: A data receiver is required to detect successive 50-bit frames of data which are transmitted without any pause between frames and with a start bit value of 1 as the only start-of-frame indication. Error detection and correction is obtained by appending at the transmitter a 13-bit check word to 36 data bits (and the start bit), the value of the check word being chosen such that division of the error-free composite 49-bit code word by a predefined generator polynomial yields a syndrome (remainder) of zero. Calculation of a new syndrome value by the receiver at the speed necessary during initial frame synchronization (i.e. for each successive bit) is effected with an iterative procedure in which the previous syndrome value is left-shifted one place and the newly received digit is appended to it; the generator polynomial is added to the result by modulo-2 arithmetic if the most significant digit of the shifted syndrome word is a 1; and the remainder of -2.sup.

Abstract: A probe for sensing direction of flow of an injected current pulse along a conductor of a circuit under test is linked to an ATE, to be triggered to inject the pulse during a test sequence at a step previously found by the ATE to establish a faulty state in the circuit. Thus, the faulty one of several components connected to a circuit node can be identified. The probe itself can also be used independently, and injects an approximately triangular-waveform current pulse which has a steep rising edge and a less steep falling edge, thereby inducing a voltage pulse which is asymmetric about the zero voltage level and thus permits discrimination of the direction of current flow. The probe may have a single current injection contact disposed between the limbs of a bifurcated core for the pick-up coil.

Abstract: A receiver, for receiving a signal comprising a carrier signal modulated with a digital signal, comprises a circuit for demodulating the received signal to produce an output signal which contains the digital signal. Because of repeated filtering, the digital signal is typically in the form of an approximately sinusoidal signal, which has a component whose frequency is equal to half the basic bit rate of the digital signal: because of noise, this component is subject to considerable timing jitter. To overcome this, the output signal is digitized and applied to a digital correlator, where it is correlated with a reference signal whose frequency is also equal to half the basic bit rate of the digital signal. The reference signal is preferably derived from a phase-locked loop locked to the carrier frequency.

Abstract: A receiver, for receiving a signal comprising a carrier signal modulated with a digital signal, comprises means for demodulating the received signal to produce an output signal which contains the digital signal. Because of repeated filtering, the digital signal is typically in the form of an approximately sinusoidal signal, which has a component whose frequency is equal to half the basic bit rate of the digital signal: because of noise, this component is subject to considerable timing jitter. To overcome this, the output signal is digitized and applied to a digital correlator, where it is correlated with a reference signal whose frequency is also equal to half the basic bit rate of the digital signal. The reference signal is preferably derived from a phase-locked loop locked to the carrier frequency.

Abstract: A probe for sensing direction of flow of an injected current pulse along a conductor of a circuit under test is linked to an ATE, to be triggered to inject the pulse during a test sequence at a step previously found by the ATE to establish a faulty state in the circuit. Thus, the faulty one of several components connected to a circuit node can be identified. The probe itself can also be used independently, and injects an approximately triangular-waveform current pulse which has a steep rising edge and a less steep falling edge, thereby inducing a voltage pulse which is asymmetric about the zero voltage level and thus permits discrimination of the direction of current flow. The probe may have a single current injection contact disposed between the limbs of a bifurcated core for the pick-up coil.

Abstract: An electronic multiplying circuit, primarily intended for use in an electronic watthour meter, comprises a variable-transconductance multiplier of the type comprising two emitter-coupled pairs of transistors, the collectors of one pair being cross-coupled with the collectors of the other pair. In order to permit the effective polarity of one of the input signals to the multiplier to be reversed from time to time for drift correction purposes, this input signal is applied to a semiconductor switching circuit, which applies it alternately to the respective bases of a further emitter-coupled pair of transistors. The collectors of the transistors of this further pair are connected in series with the coupled emitters of respective ones of the emitter-coupled pairs in the variable-transconductance multiplier.

Abstract: A line buffer circuit for coupling an interface to a data highway without requiring separate signal paths for sense and drive functions, comprises a unity-gain voltage amplifier coupling a line in the highway to the respective interface terminal for the sense function, and a current source connected to sink current from the highway line to ground for the drive function. The current source is controlled so that the current passing through it is proportional to the magnitude of the current passing from the amplifier through the interface terminal.

Abstract: A displacement transducer comprises a charge coupled device having a plurality of light sensitive stages arranged in a line. An obturating member connected to a member whose displacement is to be transduced is disposed between the charge coupled device and a light source. As the obturating member is moved, it varies the amount of light received by the respective stages of the charge coupled device, so that the charge distribution in the charge coupled device is representative of the position of the obturating member and therefore of the member whose displacement is to be transduced.

Abstract: In a spectrum analyzer, the analogue signal to be analyzed is periodically sampled and digitized, and the digit samples are formed into R successive arrays each containing 2N successive samples and each overlapping the previous array by 50%. The forward Fourier transforms of each array are then successively formed, and an array of 2P complex points is formed from the result of each transform, where L-P/2 and L+P/2-1 are the points which represent the upper and lower limits of a Vernier band to be studied in detail and each array extends from points L-P to L+P-1 (i.e. each array is twice the width of the Vernier band, and the Vernier band is symmetrically disposed therein): additionally, each array for which L and R are odd is complemented. The arrays thus formed are then each multiplied by a window function (effectively equivalent to a band pass filter), and the result is subjected to the inverse Fourier transform to form respective further arrays of 2P points.

Abstract: The analogue storage circuit includes a charge transfer device such as a charge-coupled device (CCD) and a quantizing circuit. The charge transfer device is arranged to shift an analogue signal from its input to its output, the analogue signal being subject to a change in magnitude during such shifting.The quantizing circuit receives the analogue signal from the output of the charge transfer device and quantizes that signal at a respective one of several substantially discrete levels. The quantizing circuit is arranged to apply the quantized analogue signal to the input of the charge transfer device, whereby in operation the analogue signal is circulated round the loop defined by the charge transfer device and the quantizing circuit. The quantizing circuit is further arranged to quantize the analogue signal, upon each subsequent receipt thereof, at the same one of the discrete levels.

Abstract: The analogue storage circuit comprises a nonlinear amplifier for amplifying an input voltage. The amplifier includes means for generating a sequence of predetermined voltages, each predetermined voltage being higher than the preceding one in the sequence. A plurality of voltage level responsive circuits are each connected to receive the input signal and a respective one of said predetermined voltages and are each arranged to change from a first state to a second state as the input voltage passes through a level of equality with the respective predetermined voltage in a given direction. An output circuit is provided, as well as a plurality of voltage follower circuits each having a first input connected to receive a respective one of the predetermined voltages and an output connected to the input of the output circuit.

Abstract: A highly linear AC to DC conversion system comprises a variable gain amplifier via which an AC signal to be converted is applied to an AC/DC converter. The output of the AC/DC converter is compared with a reference level and a control signal dependent on the difference therebetween adjusts the gain of the variable gain amplifier so as to reduce the difference. The output of the AC/DC converter is also applied to one input of a comparator, whose DC output is applied via the variable gain amplifier to the other input of the comparator. The variable gain amplifier has exactly the same gain for both AC and DC signals. It can then be shown that the DC output signal produced by the comparator is very accurately linearly related to the magnitude of the AC input signal.

Abstract: A thermocouple probe 10 suitable for use in a gas turbine engine comprises a thermocouple element 12 which is coaxially arranged inside a protective sheath 16. The thermocouple element 12 is resiliently supported by a helical member 18 which insulates the element 12 from deleterious vibrations induced in the sheath 16. In use, the thermocouple probe 10 projects through an aperture 30 in the casing 32 of a gas chamber 34. Vibrations in the probe 10 are further reduced by ensuring that the longitudinal axis AA of the probe is angularly offset from the central axis BB of the aperture 30, such that the outer periphery of the sheath 16 is in contact with the inner periphery of the aperture 30 in two diametrically opposite and axially offset locations.