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Adjustable angular drill block accurately transfers hole patterns from mating surfaces not normal to each other. Block applicable to transfer of nonperpendicular holes in mating contoured assemblies in aircraft industry. Also useful in general manufacturing to transfer mating installation holes to irregular and angular surfaces.
It is pointed out that the increasing computation power and rapidly falling cost of microprocessors and memories have given an impetus to the development of distributed computing systems. There are a number of potential benefits. A number of issues have to be resolved, however, before the full potential of a distributed processing system can be realized. The present investigation is concerned with one such issue, taking into account the effectiveness of implementing recovery blocks (RB's) in backward error recovery for a set of cooperating processes. A quantitative evaluation of three different recovery blocks employed in backward error recovery for concurrent processing is performed.
In many programs solving difference equations, problem size is restricted by the number of available memory cells. A strategy has been developed to permit trade-offs between the number of floating point operations required and storage requirements for the solution of certain problems such as block tridiagonal systems of equations. This is done by recomputing some intermediate results instead of storing them. Reducing the storage to the square root of the current requirement will roughly double the number of computations. In theory, if m is the order of each sub-matrix in the block tridiagonal matrix, one can solve any linear system with only 5 sq m + 1 temporary storage cells. This method lends itself to efficient use on computers with parallel processing or vector processing architectures. On these computers the larger number of floating point operations is more than offset by the decrease in I/O and the increased percentage of vector operations made possible by this algorithm.
The introduction and development of the block copolymerization concept in metal oxide gel synthesis will in the future generate a new class of glass/microcrystalline materials. By the year 2004, better scientific understanding of the chemical principles controlling the distribution of network formers or modifiers in silicate gels will permit the synthesis of architecturally well-defined block polymers with unique high-performance behavior.
The development of an X-band exciter, for use in the X-Band Uplink Subsystem, was completed. The exciter generates the drive signal for the X-band transmitter and also generates coherent test signals for the S- and X-band Block 3 translator and a Doppler reference signal for the Doppler extractor system. In addition to the above, the exciter generates other reference signals that are described. Also presented is an overview of the exciter design and some test data taken on the prototype. A brief discussion of the Block 3 Doppler extractor is presented.
The two dimensional block transform coding scheme based on the discrete cosine transform was studied extensively for image coding applications. While this scheme has proven to be efficient in the absence of channel errors, its performance degrades rapidly over noisy channels. A method is presented for the joint source channel coding optimization of a scheme based on the 2-D block cosine transform when the output of the encoder is to be transmitted via a memoryless design of the quantizers used for encoding the transform coefficients. This algorithm produces a set of locally optimum quantizers and the corresponding binary code assignment for the assumed transform coefficient statistics. To determine the optimum bit assignment among the transform coefficients, an algorithm was used based on the steepest descent method, which under certain convexity conditions on the performance of the channel optimized quantizers, yields the optimal bit allocation. Comprehensive simulation results for the performance of this locally optimum system over noisy channels were obtained and appropriate comparisons against a reference system designed for no channel error were rendered.
The performance of certain binary block codes with soft-decision decoding is evaluated by simulation. A construction is proposed to introduce memory on block codes, and simulation results are shown for a trellis code derived from the Nordstrom-Robinson code.
Three Landsat MSS scenes were processed to empirically determine the sampling intensity needed to characterize various land cover types including water, conifer, and hardwood. The block sizes used as the sampling units were 497 by 500 pixels (picture elements) and 248 by 250 pixels. It is found that, for a given accuracy criterion, the sampling intensity is dependent on the abundance of the cover type of interest in the MSS scene. The results also indicate that, when using the smaller block size, a smaller percentage of the scene has to be classified to obtain a given level of accuracy.
The ability of buspirone to prevent motion sickness and the mechanism of the buspirone action were tested in cats pretreated (s.c. injection) by buspirone 30 min before being subjected to motion stimulus (in a device described by Crampton and Lucot, 1985) or to an injection of an emetic drug xylazine (using only cats susceptible to motion sickness or to xylazine, respectively). Buspirone treatment was found to block motion sickness with an effective dose-50 of 0.46 mg/kg. Buspirone pretreatment (with 4.0 mg/kg) has also significantly blocked vomiting in cats later injected with 0.66 mg/kg xylazine. The results indicate that buspirone is acting at the vomiting center, the point of convergence for the separate mechanisms subserving chemically-induced emesis and motion sickness.
A solution procedure is presented for predominantly supersonic viscous flows. The procedure approximately solves the Navier-Stokes equations by marching blocks of grid points in the streamwise direction and solving the fully elliptic equations within each block. In this manner elliptic effects of limited streamwise extent may be accurately calculated. Results are presented for calculations of a Mach 2 laminar flat-plate shock/boundary-layer interaction, and for a Mach 10 hypervelocity interceptor.
Set of clamps and mounting block developed for use in determining tensile moduli and damping properties of films in manually operated or automated commercial viscoelastometer. These clamps and block provide uniformity of sample gripping and alignment in instrument. Dependence on operator and variability of data greatly reduced.
The solution of a block tridiagonal matrix using parallel processing is demonstrated. The multiprocessor system on which results were obtained and the software environment used to program that system are described. Theoretical partitioning and resource allocation for the Gaussian elimination method used to solve the matrix are discussed. The results obtained from running 1, 2 and 3 processor versions of the block tridiagonal solver are presented. The PASCAL source code for these solvers is given in the appendix, and may be transportable to other shared memory parallel processors provided that the synchronization outlines are reproduced on the target system.
Heat flow values and heat generation data calculated from the concentration of heat producing radioactive elements, U, Th and K in surface rocks were analyzed. The South Indian Craton according to Drury et al., can be divided into various blocks, separated by late Proterozoic shear belts. The northern block comprises Eastern and Western Dharwar Cratons of Rogers (1986), Naqvi and Rogers (1987) and a part of the South Indian granulite terrain up to a shear system occupying the Palghat-Cauvery low lands. The geothermal data analysis clearly demonstrates that the present thermal characteristics of the above two Archaean terrains of the Indian and Australian Shields are quite similar. Their crustal thermal structures are likely to be similar also.
The construction of computational fluid dynamics (CFD) codes for complicated regions is greatly simplified by a composite-block grid structure since, with the use of a surrounding layer of points on each block, a flow code is then only required basically to operate on rectangular computational regions. The necessary correspondence of points on the surrounding layers (image points) with interior points (object points) is set up by the grid code and made available to the CFD solution code.
A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.
The performance (bit-error rate vs. signal-to-noise ratio) of two different interleaving systems, block interleaving and the newer helical interleaving are compared. Both systems are studied with and without error forecasting. Without error forecasting, the two systems have identical performance. When error forecasting is used with shallow interleaving, helical interleaving gains, but less than 0.05 dB, over block interleaving. For higher interleaving depth, the systems have almost indistinguishable performance.
A set of film clamps and a mounting block for use in the determination of tensile modulus and damping properties of films in a manually operated or automated Rheovibron is diagrammed. These clamps and mounting block provide uniformity of sample gripping and alignment in the instrument. Operator dependence and data variability are greatly reduced.
The Short Wave Spectrometer (SWS) is one of the two spectrometers for the Infrared Space Observatory (ISO). It consists of a pair of grating spectrometers and a Fabry-Perot interferometer. Together, the grating spectrometers cover the wavelength range 2.4 to 45 microns, at a resolution between 1000 and 2000. The Fabry-Perot interferometer, in series with one of the grating spectrometers, provides a resolution of about 20,000 at the wavelengths between 15 and 35 microns. The SWS is being built by the Space Research Organization of the Netherlands and the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The spectrometer has 52 discrete detectors, most of which are bulk detectors. In the design of the spectrometer, the main emphasis is on the sensitivity of the individual channels, rather than on the number of detectors. This was one of the main reasons to select non-destructive read-out circuits, with a separate heated-JFET pre-amplifier for each individual detector. The signals are amplified and filtered in parallel. The engineering tests on the SWS detector block have not yet been completed. The design of the detector block is described and the present problem areas are indicated.