摘要:
Starting from a process for producing a rod-like preform, in particular for optical fibers, in which a tubular blank whose refractive index changes, viewed in the radial direction is fed to a heating zone, is softened there, and in the softened state is shaped to give the preform, a method is described for producing preforms which are hyperpure and low in defects, in which the blank used is one whose refractive index decreases, viewed in the radial direction, from the outside inwards, starting from at least one interface which is at a sufficient distance from the outer surface of the blank, of which that part which has been softened in the heating zone is introverted apart from an outer skin, and by which the preform is formed in the longitudinal axis of the tubular blank, counter to the direction in which the latter is fed to the heating zone, and in which the remaining outer skin is drawn off as a rod in the feed direction of the blank.
摘要:
A process is known for the tool-free reshaping of a tubular hollow body of amorphous, especially vitreous material to a rod by pressure constriction wherein a pressure depression below atmospheric pressure is sustained in the tubular part by continual evacuation during the constriction, while the hollow body is continually fed horizontally, at a given speed of rotation, to a heating zone, and there its viscosity is so lowered that, as a result of the pressure difference between the absolute value of pressure below atmospheric pressure in the hollow body and the external pressure acting on the hollow body, the hollow body becomes constricted to form a rod in the closing zone and the rod is continually pulled from the closing zone at a given rotatory speed; in order by such a process to produce homogeneous, rod-shaped bodies from hollow bodies in a single procedure and at reasonable cost, the outside dimensions and inside dimensions of the hollow body, the viscosity of the vitreous material in the closing zone, the pressure difference between the absolute value of pressure below atmospheric pressure in the hollow body and the external pressure, the level of the pressure constriction, the rate of withdrawal of the rod and the rate of feed of the hollow body, as well as the rotatory speeds of the rod and hollow body, are selected such that a spur of smaller cross-sectional dimensions than those of the rod is formed in the axis of the hollow body from the closing zone in a direction contrary to the direction of withdrawal of the rod.
摘要:
Granular silicon dioxide is placed in a treatment chamber which is heated to a temperature ranging from 700.degree. to 1300.degree. C. The chamber is then rotated for a prescribed period of time to mix the grains while a gaseous atmosphere of chlorine and/or hydrogen chloride is passed through the treatment chamber. The mixing period is followed by a resting period which is at least ten times longer than the mixing time. During the resting period the grains are exposed to a constant electric field having a strength of 600 to 1350 V/cm applied across the chamber. The foregoing cycle is repeated several times. For working the process a device is used which includes a quartz glass rotary tube into which hollow silicon carbide electrodes extend.
摘要:
An RF device includes a substrate and a series circuit of a tunable RF component and a DC blocking capacitor. The series circuit is arranged on the substrate and couples an RF signal terminal to a fixed voltage terminal that is electrically isolated from the RF signal terminal. The tunable RF component is coupled to the RF signal terminal, the DC blocking capacitor is coupled to the fixed voltage terminal and a driver terminal is coupled to the tunable RF component.
摘要:
A switching circuit employs MEMS devices. In connection with various example embodiments, signal switching circuit couples primary and secondary data link connectors having at least two channels and an electrode for each channel. A MEMS switch is coupled to each channel in of the secondary data link connectors, and includes a suspended membrane, first and second contact electrodes (one being in the membrane) and a biasing circuit that biases the membrane for moving the membrane between open and closed positions to contact the electrodes. A switch controller circuit selectively controls the application of an actuation voltage to each of the biasing circuits, thereby selectively actuating the membranes between the open and closed positions for routing signals between the primary and secondary data link connectors.
摘要:
A capacitive ultrasound transducer includes a first electrode, a second electrode, and a third electrode, the third electrode including a central region disposed in collapsibly spaced relation with the first electrode, and a peripheral region disposed outward of the central region and disposed in collapsibly spaced relation with the second electrode. The transducer further includes a layer of a high dielectric constant material disposed between the third electrode and the first electrode, and between the third electrode and the second electrode. The transducer may be operable in a collapsed mode wherein the peripheral region of the third electrode oscillates relative to the second electrode, and the central region of the third electrode is fully collapsed with respect to the first electrode such that the dielectric layer is sandwiched therebetween. Piezoelectric actuation, such as d31 and d33 mode piezoelectric actuation, may further be included. A medical imaging system includes an array of such capacitive ultrasound transducers disposed on a common substrate.
摘要:
A transducer (800) is provided where a membrane (830) is formed over a front substrate (615); and a piezoelectric layer (820) is formed over the membrane (830) at an active portion (821) and peripheral portions located adjacent the active portion (821). A patterned conductive layer including first and second electrodes (840, 845) is formed over the piezoelectric layer (820). Further, a back substrate structure is provided having supports (822, 824) located at the peripheral portions adjacent the active portion (821). The height (826) of the supports (822, 824) is greater than a combined height (828) of the patterned piezoelectric layer and the patterned conductive layer. Many transducers may be connected to form an array, where a controller may be provided for controlling the array, such as steering a beam of the array, and processing signals received by the array, for presence or motion detection and/or imaging, for example.
摘要:
The invention relates to electronic device having an operation temperature range, wherein the electronic device comprises a tunable capacitor (CST) comprising a first electrode (BE), a second electrode (TE), and a dielectric (FEL) arranged between the first electrode (BE) and the second electrode (TE). The dielectric (FEL) comprises dielectric material (FEL) having a value of a relative dielectric constant (εr) varying at least within the operation temperature range. The electronic device further comprises a temperature varying means (RES) being thermally coupled to the tunable capacitor for providing a temperature of the dielectric (FEL) causing a predetermined capacitance of the tunable capacitor (CST). The invention, which relies on the idea of varying temperature to vary a capacitance of a capacitor stack, provides an alternative tunable capacitor type for the known types. Advantageous embodiments feature high-tuning ratio, small device area, and stable capacitance value in case the temperature is well controlled. The invention further relates to a semiconductor device comprising the electronic device in accordance with the invention, to an electronic circuit comprising such electronic device, and to a method of manufacturing such electronic device.
摘要:
A transducer (800) is provided where a membrane (830) is formed over a front substrate (615); and a piezoelectric layer (820) is formed over the membrane (830) at an active portion (821) and peripheral portions located adjacent the active portion (821). A patterned conductive layer including first and second electrodes (840, 845) is formed over the piezoelectric layer (820). Further, a back substrate structure is provided having supports (822, 824) located at the peripheral portions adjacent the active portion (821). The height (826) of the supports (822, 824) is greater than a combined height (828) of the patterned piezoelectric layer and the patterned conductive layer. Many transducers may be connected to form an array, where a controller may be provided for controlling the array, such as steering a beam of the array, and processing signals received by the array, for presence or motion detection and/or imaging, for example.
摘要:
A capacitive ultrasound transducer includes a first electrode, a second electrode, and a third electrode, the third electrode including a central region disposed in collapsibly spaced relation with the first electrode, and a peripheral region disposed outward of the central region and disposed in collapsibly spaced relation with the second electrode. The transducer further includes a layer of a high dielectric constant material disposed between the third electrode and the first electrode, and between the third electrode and the second electrode. The transducer may be operable in a collapsed mode wherein the peripheral region of the third electrode oscillates relative to the second electrode, and the central region of the third electrode is fully collapsed with respect to the first electrode such that the dielectric layer is sandwiched therebetween. Piezoelectric actuation, such as d31 and d33 mode piezoelectric actuation, may further be included. A medical imaging system includes an array of such capacitive ultrasound transducers disposed on a common substrate.