Abstract: A chainsaw guard for enhancing safe operation of a chain saw. The guard includes a housing providing a physical barrier that limits access to the cutter chain of the chain saw. The housing has an opening for exposing a selected portion of the cutter chain for cutting a target object such as the roof of a burning building or the exterior surface of a tree. A coupler adjustably connects the housing to the chain saw. To improve flexibility, the housing includes two sections that can move relative to each other. The housing alone or in cooperation with the object being cut succeeds in enclosing substantially all of the cutter chain at all times to prevent human injury by the cutter chain, and in keeping the cutting edge facing away from the user. The housing further reduces risk of injury by limiting the depth of the cut made by the chainsaw.

Abstract: The present invention improves the interaction of a virtual memory systems and a garbage collection system, thereby reducing garbage collection effort and improving virtual memory performance. The method includes the steps of: (1) developing a secondary memory (e.g. disk) dirty page map; (2) developing a saved state map from a primary memory (e.g. RAM) dirty page map; (3) using the secondary memory dirty page map and the primary memory dirty page map to effectively reduce the size of the base set; (4) performing a garbage collection routine on at least a segment of the heap based upon the effectively reduced base set; and (5) performing a virtual memory routine using the primary memory dirty page map and the saved state map. The apparatus of the present invention implements the method on a digital computer system with a combination of hardware and software.

Abstract: A phase shifter providing constant group delay and a wide instantaneous bandwidth is taught. In one embodiment, an input port is connected to an output port with a power splitter formed of a transformer connected between the input port and the output port, and having a center tap serving as a sum port. An impedance, such as a resistor, is connected in parallel with the transformer between the input port and the output port. A reactive network is connected between the sum port and ground, including one or more variable reactance device, such as a varactor, which alter the reactance of the reactive network in response to a control signal. Additional reactive elements are included in the reactive network to provide additional poles and zeros which change frequency in response to the variable reactance elements, in order to provide a group delay which is constant for various reactance values provided by the reactive network between the lowest frequency of interest and a higher frequency of interest.

Abstract: Disclosed is an improved thermal ink jet print head with an amorphous diffusion barrier that inhibits corrosion associated with ink. The head has a silicon substrate, a silicon dioxide insulating layer, a tantalum aluminum alloy (TaAl) resistive layer, and two separated gold conductive regions formed over the resistive layer. Ink is drawn into a channel bounded above by an orifice plate and below by the TaAl exposed between the two separated gold regions. The ink is superheated and expelled as fine droplets through the orifice plate. The invention minimizes corrosion by placing a thin corrosion-resistant layer of amorphous metallic alloy over the conductive layer, thereby improving durability of the print head.

Abstract: An orifice plate is thermally bonded to a thick film photopolymer spacer fabricated on a print head substrate using heat and compression. The compression is applied by pressurized gas to a pliable sheet covering the orifice plate and substrate assembly. Heat can be supplied through a vacuum chuck on which the assembly is mounted or from a heating element embedded in the pliable sheet. An apparatus comprising an air actuated ram with a flange having an o-ring seated within is used to seal the pliable sheet against the vacuum chuck circumferentially about the assembly. The ram includes a chamber with an open end which is sealed against the pliable sheet when in an engaged position. By filling the chamber with gas under sufficient pressure while heating the spacer forms a bond between the orifice plate and the assembly. After thermal bonding, curing of the photopolymer spacer can be completed in an oven.

Abstract: A wide dynamic range radio-frequency power sensor having a low-power sensor portion and a high-power sensor portion is described. Both sensing portions are connected to an input signal at the same time without the use of a signal splitter. In the preferred embodiment, a single radio-frequency load serves both sensor portions. Each sensor portion has its own output terminal. The low-power sensor portion includes a pair of diodes. The high-power sensor portion (which includes the radio-frequency load) may include a pair of diodes preceded by an attenuator, or a pair of thermocouples.

Abstract: A thin film recording head which utilizes polyimide as the coil encapsulant. The polyimide encapsulant is self planarizing and lends itself to processing of the coil vias, magnetic shunt vias and apex tapers. Methods of fabricating a thin film recording head and forming coil vias, magnetic shunt vias and apex tapers are also disclosed. In general, an insulating material is deposited on a bottom magnetic yoke. A first layer of polyimide is then deposited of the insulating material. Then, a three layer photoresist structure is deposited on the first layer of polyimide, which includes a transfer layer deposited between two layers of photoresist. The top layer of photoresist is developed and the transfer layer is etched. The first layer of photoresist is then etched into the polyimide layer to form troughs therein. The coil material is then deposited into the etched troughs. The coil material comprises a layer of metal having a relatively thin passivation layer deposited thereover.

Abstract: A broadband-tunable external fiber-cavity laser system includes a laser diode, and a single-mode optical fiber with an in-line fiber optic grating filter. The grating filter includes a grating with divergent ridges so that the periodicity at an exposed evanescent field can be adjusted by translating the grating transversely with respect to the fiber. The evanescent field of light transmitted along the fiber core is accessed at a side-polished region. The laser preferentially oscillates at the reflected wavelength, so that the laser output is tuned by moving the grating. The grating is manufactured by oblique exposure to a holographic wavefront, producing the divergent pattern.

Abstract: A digital integrating mixer is described including a bandpass filter for filtering an input signal, a comparator for comparing the filtered signal to a reference signal to provide an output which may be of one of two values. A cascaded string of D flip-flops samples the comparator output at predetermined times to provide a first and second type of sample. The time interval between any two samples of the same type is an integral multiple of the cycles of the input signal. The time interval between any two samples of different types is different from an integral multiple of a cycle of the input signal. The mixer also includes a counter which counts up when the sample is of the first value and counts down when the sample is of the second value, when the sample is of the first type, and counts in the opposite direction when the sample is of the second type. If the string of D flip-flops samples approximately an equal number of the first and second types of samples, DC offset in the mixer is reduced.

Abstract: A disk-drive-compatible magnetic tape cartridge is provided with a tape guide for accurately positioning a magnetic tape in relation to a disk drive head. The tape guide includes a positioning section to be aligned with a rotation axis of a center core assembly when the center core assembly is chucked on a turntable of the disk drive. The tape guide also includes a guide section defining a tape run path across the disk drive head. The guide section is formed integrally with the section to be aligned with the center core assembly and so distanced from the latter as to accurately position the magnetic tape with respect to the disk drive head. Since the tape guide has the positioning section and guide section integrally, the distance therebetween can be maintained precisely constant. Therefore, tracking by the disk drive head becomes easier to allow high-density recording.

Abstract: An information storage system records on a medium with a magneto-optical storage layer and a ferrimagnetic control layer. A higher power write beam is used to impose an upward magnetic orientation and a lower power write beam is used to impose a downward magnetic orientation in the domain. The control layer has an initial downward magnetic orientation, the magnetization of regions of the control layer can be inverted to an upward orientation temporarily while the region is heated above a compensation temperature. The magnetization of the region is restored to its initial downward orientation upon restoration of ambient temperature since neither the higher power nor the lower power write beam heats the control layer to its Curie temperature. The distributed optical and thermal properties of the medium are selected so that, upon heating of the medium by dissipated laser energy, the peak temperature of the control layer occurs after the peak temperature for the storage layer.

Abstract: A stylus contains a switch which makes contact in response to slight radial motion of the stylus tip relative to the stylus housing. Means for emitting radiation operates in response to switch closure, thereby emitting a beam of radiation out the tip. The stylus includes an internal power source, such as one or more batteries, for operation of the means for emitting radiation. When such internal power source is capable of being recharged, the stylus may include means for external connection to the recharging supply. In another embodiment, the stylus is capable of emitting more than one type of radiation which are distinguishable, such as by wavelength, modulation type, or other convenient means. In this manner, the stylus can be controlled by the user to emit different signals, which may be interpreted by a receiving device, for example, as different colors, or as a write signal versus an erase signal. In one embodiment, such an erase signal is emitted from the opposite end of the stylus as the write signal.

Abstract: A read/write head for a hard disk provides both a magneto-resistive read function and an inductive write function in a common gap. The inductive write function is provided by a current carrying coil which is magnetically coupled to top and bottom shields or pole tips which in turn induce the magnetic fields required for writing on the disk. Mutually biasing magneto-resistive read sensor are located between the shields, which serve to improve the resolution of the read function. During a read operation, read/write circuitry maintains a current in the coil which cancels, at least partially, magnetic fields induced by sensing and bias currents in the magneto-resistive heads which might other perturb information stored in the medium. This arrangement provides a read/write head with improved read/write resolution as required by emerging high density storage media in compact formats.

Abstract: A sensor for reading perpendicularly recorded media includes dual magneto-resistive elements. Directionally opposed currents through respective elements each serve both sensing and bias functions. A detector differentially detects changes in the resistance of the stripes so as to presume common mode noise rejection when reading perpendicular recording media. In addition, the opposing currents offset each other's interaction with the soft magnetic underlayer of the media, which interaction could otherwise perturb the information stored on the media. Provision is made for switching the relative direction of current flow to provide for reading longitudinally recorded media.

Abstract: A novel flat panel display is provided which allows for very precise and reliable detection of the location of the cursor with respect to the displayed image. Parallax problems are eliminated by focusing the displayed image on a panel by projecting the image through the panel. The location of the stylus is accurately determined, in one embodiment, utilizing prior art digitizing techniques together with the use of an erect, unity magnification imaging lens array for displaying the projected image. In another embodiment of this invention, accurate determination of the location of the stylus with respect to the displayed image is provided by causing the stylus to feed signals, for example optical signals, through a significant portion of the optical path used for displaying the image.

Abstract: In a computer device in accordance with the preferred embodiment of the invention, an instruction set which uses a two-instruction sequence to store the result of a comparison is provided. The two-instruction sequence, which uses no branch instructions, does not need to wait for condition resolution before storing conditional results. Additionally, it also is capable of implementing slightly more general operations than simply storing a zero or one value of a comparison. Basically, the instruction set in accordance with the invention compares two operands and unconditionally stores a zero, which represents a Boolean "false", into a selected destination. The instruction set then conditionally nullifies the instruction following it, thus effecting a highly efficient execution of a sequence of instructions compared to the prior art.

Abstract: A thermal ink jet printing system includes a drop detector which is used in a feedback loop to optimize operational drive pulse parameters. By optimizing the drive pulse, drop velocity can be set within an optimal range above a inflection point in the transfer function of a print head drop generator. This provides near maximal drop velocity while minimizing heat dissipation at the heater resistors which would otherwise impair reliability and print head life. The drive circuitry includes a microcontroller including a pulse controller, a test generator and an algorithm function. During a maintenance procedure, for example, during start-up, the test generator causes the pulse controller to test each of many drop generators with a series of fixed-voltage rectangular pulses of digitally increasing pulse width. The pulse width at which a drop is first detected and the velocity of each drop detected is correlated with the width of the pulse which generated that drop.

Abstract: A protective circuit for a semiconductor laser supplied with an excitation current by a current generator circuit is created using a transducer, whose output is controlled by the laser light, a limit circuit cooperating with the transducer and a current shunt circuit energized by the limit circuit and switched in parallel with the semiconductor laser. Once the permissible emitted light power is reached, excessive excitation current is diverted to the shunt circuit. Exemplary embodiments of the invention are found to achieve response times below 20 ns and are able to protect the semiconductor laser from overload currents even during power-on and power off.

Abstract: A method for testing layering processes of integrated circuit construction for random defects. A test structure is employed having a plurality of micro-patterns covering a wafer, the patterns being fabricated in accord with a unit process of an integrated circuit manufacturing operation. The patterns are fabricated either with a lower conductive level covered by an insulative layer and an upper conductive level, all having pads which may be probed at the upper level, or a single conductive layer. By repeating tests in various unit processes, random defects can be isolated to individual unit processes. Nine patterns are disclosed which form a universal test set.

Abstract: A lift-off process for patterning bottom shields used in thin film magnetic recording heads. The lift-off process comprises the steps of depositing a first layer of resist material (22) on a substrate (20) and hard baking the resist material (22). A transfer layer (24) is deposited over the first layer of resist material (22) and a second layer of resist material (26) is deposited on top of the transfer layer (24). The second layer of resist material (24) is then patterned and developed. The patterned structure is then etched to form a mask structure wherein the transfer layer (24) overhangs the first layer of resist material (22). An adhesion layer (30) and an amorphous magnetic alloy material (32) are then sequentially deposited on the exposed surface of the substrate (20). The amorphous magnetic alloy material (32) is sputter deposited at a pressure of about 3.4 mT, a condition that resists the stress in the amorphous alloy material to less than 10.sup.9 dynes per square centimeter.