Abstract: In a data storage system providing access to a production dataset and snapshot copies of the production dataset, a production meta bit map identifies blocks of storage that are invalid in the production dataset. If a block in the production dataset is invalid when a snapshot copy is being made, then there is no need to copy the block to storage for the snapshot before writing to the block. Moreover, if a block in the production dataset supporting a snapshot copy is dynamically invalidated, it may be kept in the production dataset until it is written to. For this purpose, a respective snapshot copy of the meta bit map is made and kept with each of the snapshot datasets, and the snapshot copies of the meta bit map are merged in order to indicate the blocks that are invalid for all of the snapshots.

Abstract: A periodic multi-bit digital signal is synthesized having a frequency that is specified by the frequency of a periodic reference signal that is asynchronous with respect to a sampling clock of the periodic digital signal. In a digital video system, for example, a digital color subcarrier is synthesized and synchronized to a reference frequency of a crystal oscillator that is asynchronous with respect to a digital system clock for the digital video system. The periodic digital signal is generated by an adjustable digital oscillator clocked by the sampling clock. The frequency or phase of the periodic digital signal is compared to the frequency or phase of the periodic reference signal to produce an adjustment value for adjusting the periodic digital signal to synchronize the periodic digital signal with the periodic reference signal. The digital oscillator, for example, generates the periodic digital signal at the sampling rate by periodically incrementing an accumulator with the adjustment value.

Abstract: A data display, preferably having screens or windows, is built from data in a data base according to a hierarchy of display knowledge. Therefore, the data values themselves are separate from the knowledge or rules that specify how the data values are displayed to a user. In particular, the display knowledge is arranged in a hierarchy so that an individual item of display knowledge may be applicable to a wide range of data values representing the attributes of a number of different objects. In many cases, the range of data values or the attributes which the data values represent can be changed without any need to change the display knowledge. In other cases, only minor changes to the display knowledge are needed to properly display values for new or different data. These minor changes, for example, need only be made by changing the lowest level in the hierarchy of the display knowledge or associating items of display knowledge in the lowest level with different display knowledge in the higher levels.

Abstract: For enabling a resolver (120) to have absolute position sensing over a wide displacement range while still obtaining the resolution, accuracy and precision obtainable by operation in an incremental mode, the resolver is provided with a number of terminals (.phi..sub.1, .phi..sub.1, .phi..sub.2, .phi..sub.2) for providing offset pitch phase indications (C.sub.1, C.sub.2) as a function of position. A microcomputer (171) is programmed to execute a decoding procedure (160) for reading the offset pitch phase indications and from them computing the absolute position. This method is applicable to linear as well as rotary position sensing. By using multiplexing, digital signal processing and large-scale circuit integration (170) for interfacing the resolver (120) to the microcomputer (171), the method can achieve absolute position sensing with high reliability and low cost.

Abstract: For enabling a resolver to have absolute position sensing over a wide displacement range while still obtaining the resolution, accuracy and precision obtainable by operation in an incremental mode, the resolver is provided with a number of terminals for providing offset pitch phase indications as a function of position. A microcomputer is programmed to execute a decoding procedure for reading the offset pitch phase indications and from them computing the absolute position. This method is applicable to linear as well as rotary position sensing. By using multiplexing, digital signal processing and large-scale circuit integration for interfacing the resolver to the microcomputer, the method can achieve absolute position sensing with high reliability and low cost. The offset pitch phase indications are readily provided by inductive coupling between a multiplicity of windings, including a set of offset pitch windings connected to the terminals.

Abstract: A computer graphic interface allows a user to obtain descriptive information concerning a feature of a displayed image by pointing to the location of the feature. Conversely, the user may enter descriptive textual information, and the locations of responsive features are indicated. The data processing and memory storage requirements are minimized by encoding information about the image as a pixel bit map, and a color map in which the addresses or indices of the color map are correlated with the addresses or pointers to strings of descriptive information. Each color map address corresponds to a predefined set of features and descriptive information about those features. Since the pixel bit map defines a color map address for each location on the image, suitable programming of the color map can insure proper correlation of descriptive information with corresponding locations on the image.

Abstract: The copper corrosion rate is minimized to a certain discharge limit by providing a chlorine-bromide treatment in which the chemical feed rate of bromide is increased to an amount required to decrease the copper corrosion rate to the rate required to meet the discharge limit. The inventors made the unexpected and surprising discovery that an increase in the chemical feed rate of bromide--even when the chlorine feed rate is constant--has the effect of reducing copper corrosion. Therefore, this effect is useful for adjusting the copper corrosion rate to an optimum rate to most economically achieve a certain discharge limit.

Abstract: A multi-directional contactless controller senses the displacement of a manipulator with respect to a reference frame along two orthogonal directions and is also provided with a resiliently biased cam and cam follower disposed between the manipulator and the reference frame for providing tactile feedback and returning the manipulator to a central position. For specific applications, the cam surface is programmed with various regions having different restoring forces or rest positions. Access to these regions can be conditioned by selectively activated solenoids or by a requirement for overt operator input. Similarly, a selectively activated solenoid can be used to conditionally prohibit exit from these regions or to selectively return the controller to the central null position.

Abstract: Hand-held chemical applicators are provided for applying chemicals such as herbicide to selected plants while surrounding plants are shielded from accidental contact. The chemical is forcefully applied by gripping or pressing a selected portion of the plant against an applicator pad containing the chemical. The amount of applied chemical is controlled by variation of the pressure or area of contact between the plant and the pad. Preferably a pair of pads are mounted to the opposing surfaces of the distal portions of pincers or tongs to define an application zone between the pads. Absorbent pads are used for applying liquid chemicals, and chemicals from a pad in the form of a solid bar or cake are applied with the aid of an absorbent pad carrying a solvent and cooperating with the bar or cake.