Showing papers on "Shields published in 1988"

Recording heads with side shields

Abstract: Side shields are provided adjacent to the magnetic poles of recording heads. The side shields are used for read and write operations for both longitudinal and vertical recording. During read, the side shields intercept flux from adjacent tracks and shunts it around the sensor to magnetic ground. During write, side shields contain the write field of the head so that it does not corrupt the data on adjacent tracks. Embodiments are disclosed for both longitudinal and perpendicular or vertical recording.

Efficient high temperature radiant furnace

Abstract: A tubular radiant furnace having multiple radiation shields is capable of producing very high working temperatures in an extremely clean environment. A cool-walled quartz muffle tube surrounded by high temperature electrical heaters in a high temperature cavity defines the work chamber. Concentric radiation shields around the tube and the heaters are supplemented by end shields at both ends to form the high temperature cavity. The shields reduce the radiative loss from the tube and create a uniform high temperature cavity without adding significant thermal inertia to the system. The low thermal inertia leads to a fast response time for the furnace to heat up or cool down. A workpiece located within the working chamber sees the radiant field with a view factor that approaches 100 percent (100%), and this helps make possible the attainment of very high and uniform temperatures. The effect is enhanced by the proximity of the workpiece to the center of the working chamber. The furnace is capable of producing temperatures above 1,800K, and it is believed capable of operating in ranges up to 3,300K. Furnaces of this type are useful in the production of semiconductors and other materials that require very clean and uniform high temperature conditions. They are also useful in the production of materials that require very rapid heat up or cool down conditions.

The Shields of Phoenissae

Abstract: T HE SHIELDS of the Argive attackers in Euripides' Phoenissae occupy some thirty lines (1104-40)1 at the beginning of the Messenger's speech describing the first inconclusive battle. Despite convincing attempts to meet the difficulties presented by these lines, wholesale excision has often been proposed as a solution.2 These difficulties arise not only from the apparently meaningless symbols described on the shields, but also from the problematic relationship of the scene itself to the comparable passage in Seven Against Thebes, a relationship that the Euripidean lines seem deliberately to obscure and contradict. In this paper I want to investigate some of the crucial ways in which the scene measures its distance from the 'original' Aeschylean text of the Seven, and to suggest that the Euripidean passage can be read as the locus of an emphatic and self-aware intertextuality, in that its relation to another text or texts is part of what it thus advertises as its meaning and as the method of deciphering it. I shall proceed to offer interpretations of the individual shields, arguing that they signify in relation not only to their Aeschylean precedents but also to the central concerns of the present play. In contrast to the passage in the Seven, the Euripidean account is much reduced and impoverished; by no stretch of the imagination does it constitute the centre of the play, as do the Aeschylean shields. It is true that some sort of shield scene appears to be anticipated in several strategic references made to shields (120, 142,251,576,796, 1073), and more precisely by the teichoskopia and Eteocles' dismissive comment to Creon (751f: lJvofLa 0' (Kcl.O\"TOV o,aTp,{3~ 7TOAA~ A€Y£LV EX8pWV 1m' aVTo,!> TEtx£O\"LV Ka81JfL€VooV). But the scene is just as repeatedly rendered impossible, or at least unlikely, by other moves in the play that pre-empt its power and significance (we know all along, for instance, that the brothers intend to kill each other). And the description of the shields is robbed of any possible charge of terror or urgency by its postponement until the battle is over and the defeat of

Soldering and desoldering device

Abstract: A device for making or undoing welds between a component with several galvanic connections and a support is particularly suited for surface mounting. In order to direct a stream of hot gas or infrared radiation accurately onto the connections of the component and corresponding weld surfaces, a mask is provided which has openings that exactly match the configuration of the weld surface. Preferably, in the case of hot-air operation, a light source is arranged behind the mask in such a way that the predetermined pattern is reproduced exactly on the substrate in the form of points of light for positioning purposes. In one embodiment, the mask comprises two pairs of horizontally adjustable shields, the two pairs of shields being arranged at an angle of 90 degrees, the shields being made of a material of low thermal conductivity.

Design of magnets inside cylindrical superconducting shields

Abstract: We discuss the design of magnets inside closed, cylindrical, superconducting shields. We give the Green function for the magnetic vector potential for cylindrically symmetric currents inside such a shield. The magnetic field everywhere inside the shield can be obtained from this function, which includes the effects of the induced shield currents exactly. We give the field for a thin solenoid as an example and discuss the convergence of the series solution for this case. The shield can significantly reduce the strength and improve the homogeneity of a magnet. The improvement in homogeneity is of particular importance in the design of correction coils. These effects, and the maximum field on the shield, are examined for a typical solenoid. The results given are also useful, although not exact, for long shields with one or two open ends.

Stiffness characteristics of longwall shields

Abstract: Since longwall strata activity is characterized by roof-to-floor and face-to-waste displacements, a model with two degrees of freedom was used to describe the load-displacement relationship of the shield structure. The model considers the support as an elastic body and relates horizontal and vertical resultant forces acting on the support to associated displacements as a function of the stiffness of the support structure. Stiffness coefficients under full canopy and base contact configurations were determined by controlled displacement loading of longwall shields in the Bureau's Mine Roof Simulator. These two-legged longwall shields of different manufacture were investigated. The stiffness characteristics of these shields were evaluated relative to two parameters, namely, shield height and setting pressure. The tests results indicate a reduction in shield stiffness for increasing height. Setting pressure was found to have less of an effect on shield stiffness, producing only a slight increase in stiffness as setting pressure increased. Similar trends were observed for all three shields, indicating a similarity in stiffness characteristics for shields of the same basic configuration.

Time domain calculation of electric field penetration through metallic shields

Abstract: A general procedure in the time domain is developed for calculating the transient electric fields that penetrate metal shields being driven by arbitrary waveforms. This method generalizes S.A. Schelkunoff's 1934 frequency-domain result to allow treatment of time-domain calculations. Applications to coaxial transmission line problems in the time domain are analyzed. The numerical implementation of the method in computer codes is discussed. >

A comparison of shielded and unshielded antennas for Alfven wave heating in a Tokamak

Abstract: Experimental results are presented which demonstrate the beneficial influence of Faraday shields on antennas used for Alfven wave heating in a Tokamak. For the RF power levels available in the experiment, the addition of the shields resulted in total suppression of the uncontrolled density rise observed using unshielded antennas. Evidence of an associated strong decrease in the power deposited in the scrape-off plasma, both by Langmuir currents drawn by the antennas and by direct wave excitation, is also presented.

New Cold Shields For Infrared Detectors

Abstract: New cold shields for infrared detectors are described, with which the signal-to-noise ratio was considerably improved. The function of two of these cold shields is based upon the use of intermediate images which make it possible to shield off housing radiation at very small incident angles to the optical axis. With these cold shields, the uniformity of the pictures was improved and the formation of undesirable background patterns was successfully eliminated.

Stationary induction apparatus

Abstract: PURPOSE:To surely prevent the localized overheating of tank structural materials while improving the simplification of a structure as well as its profitability by mounting a second magnetic shield so that leakage flux may make a detour at a peripheral part of an opening where a lead passes through. CONSTITUTION:Magnetic shields 8 allow a plurality of the magnetic shields 8A and 8B where strip-like thin silicon steel plates are laminated to be arranged in the vertical derection, in parallel one another. The magnetic shields are composed of a first magnetic shield where an opening is formed at a position facing the opening 9, thereby dividing a partial magnetic shield 8B in to upper and lower parts and a second magnetic shield 8C which is arranged at a peripheral part of the opening 9 of the first magnetic shield and is laminated by the vectangular thin silicon steel plates and has a hole where a lead passes through. Leakage flux coming in a tank 4 from a coil 2 flows in a magnetic circuit prepared by the second magnetic shield 8C having a high magnetic permeability and also leakage flux coming in the tank 4 from the coil 2 is suppressed to enter into the tank 4 having a low magnetic permeability and this configuration serves the purpose of decreasing the eddy-current loss and of preventing localized overheating of the side board of the tank 4.