Array Location Research Articles

3D Seismic Imaging Without Stack: a Case History from the Irish Sea

Conventional 3D marine seismic surveys usually employ high-fold Common Midpoint (CMP) stacking techniques, long streamers, and elaborate positioning systems to determine both the source and receiver array locations for every shot. It is inevitable that the reflection responses occurring in seismic profiles obtained through the CMP stack process are spatially averaged. Responses are further averaged over a range of reflection incidence angles in consequence of the various offset distances represented in the CMP gather. Whilst these effects may benefit the continuity of reflected events in a processed section, they detract from the potential resolution that could be achieved through subsequent 3D migration and obscure detail that might otherwise contribute to a more rigorous interpretation.

Numerical study of an area array for nearfield sound‐pressure measurement

In a previous work [M. P. Hegelberg and R. D. Corsaro, J. Acoust. Soc. Am. 77, 1222–1228 [1985)], we described our experimental experience using a planar polymer hydrophone for area‐averaged acoustic pressure measurements in the nearfield of an acoustic source. This present paper addresses theoretically the accuracy of such a measurement. A numerical analysis based on the Rayleigh integral formulation is performed on the nearfield radiation from a circular projector (disk) with ka from 10–40. The spatial average of the acoustic pressure received by an area array in the front of this projector is computed in terms of the covered area parallel to the projector's surface. Its magnitude is shown to vary only slightly with changes in the array's location, even within the projector's nearfield region. The reflected wave from a plate of finite thickness is also investigated within this nearfield region by means of the image method. These simulated results are compared with experimental echo reduction measurements obtained under plane‐wave conditions.

Performance of the Tokamak Fusion Test Reactor bolometers

For the past year we have been making use of a horizontally viewing 19-channel array and a bolometer which views a narrow cross-sectional slice of the plasma. More recently, we have also obtained results from a second, vertically viewing array. Software has been developed to translate the data from general plasma and array locations to plasma minor radius and to do the Abel inversion with an antisymmetrical term included. Experience has been obtained on the noise and response-time characteristics, as well as the accuracy of total radiated power and radial profiles. Representative cases of radiated power profiles and local power balance are presented, as well as comparisons with other measurements of impurity concentration and trends with electron density and limiter coating. Although most of the ohmic-heating input power leaves by radiation, most of this loss occurs near the outer part of the plasma. Also, the behavior of power profiles during neutral beam injection is discussed briefly.

Evaluation of efficiently computed exact vibration characteristics of space platforms assembled from stayed columns

The exact stiffness matrix method computer program BUNVIS finds the natural frequencies and modes of vibration of rigidly jointed three dimensional frames which contain stayed columns very efficiently, by using substructuring and simple substitute columns to compute the stayed column stiffness. BUNVIS is described and applied to a tetrahedral truss which was designed for use in space and which has stayed columns as its members and 21 966 degrees of freedom at its nodes. Locating the first 4978 natural frequencies needed 2 h of VAX-11/780 CPU time and 5860 array locations. These natural frequencies appeared in groups for which the associated modes are discussed.

Visual search through color displays: effects of target-background similarity and background uniformity.

The effects of target-background similarity and background uniformity were investigated in two experiments in which subjects reported the presence or absence of an achromatic target item in arrays containing irrelevant chromatic items. In Experiment 1, both “present” and “absent” decision times were an increasing function of the similarity of a predefined target item to the background, and were shortened when the interitem similarity of the background set was increased. In Experiment 2, the effects of target-background similarity on the “present” decision were replicated when subjects were not informed on each trial as to which member of the target set might appear in the array, and the “absent” decision was faster when each row of the array comprised background items of a single color than when these items were allocated randomly to array locations. The results are interpreted in terms of the role of pre-attentive grouping operations.

The deployment of strong‐motion earthquake instrument arrays

AbstractThe International Workshop on Strong‐motion Earthquake Instrument Arrays was held during 2‐5 May 1978 in Honolulu, Hawaii. The goal of the workshop was to develop a workable plan for the possible future deployment of dense strong‐motion arrays with primary emphasis on ground motion studies. Topics considered by the workshop included: favourable array locations, the design of arrays for source mechanism and wave propagation studies, the design of arrays for local effects studies, array construction and operation, and implementation. This paper gives a summary of the recommendations and conclusions of the workshop.

Compensation for integerization errors in simulated EPR spectra

EPR spectra of free radicals can be simulated in a digital computer array from a lineshape function and a series of spectral lines. When their spacings do not coincide with those represented by an integral number of array locations, errors in the spectral envelope may result.

A BASIC program to randomly generate members of a weighted set

Writing a program to randomly select and printout members of a given set (of letters, integers, words, etc.) is a relatively simple matter. All that is needed is an array in which the members may be stored, together with a random number generator which can generate numbers in the range 1 to L, where there are L members in the set. If the members of the set are stored, for example, in Array Locations A£(1) to A£(L), we might have:

The role of perceptual salience and type of instruction in children’s recall of relevant and incidental dimensional values

Kindergarten and sixth-grade children were asked to recall the array locations of dimensional values in tasks in which instructions about the relevant dimension and the salience of the task dimensions were varied. For half of the subjects within each age group, the more salient dimension was relevant and the less salient dimension was incidental to problem solution. For the remaining subjects, the procedure was reversed. Before presenting the task within each salience condition, half of the subjects were shown the values of the relevant dimension and told to remember them. The results offered no support for the position that older subjects are cognitively better able than younger subjects to select relevant and to ignore incidental information. For younger and older subjects, both relevant and incidental recall were superior for values of the more salient dimension. Prior instructions about which dimension was relevant had no effect on recall.

The recall of relevant and incidental dimensional values as a function of perceptual salience, cognitive set, and age

In two experiments, subjects were presented an array of compound stimuli consisting of values from four, salience-assessed dimensions. Solution to an initial problem required recall of the array locations of values from only the most salient dimension. In addition to perceptual salience, instructions designed to establish cognitive sets for remembering value locations of certain dimensions were varied to explore the roles of these perceptual and cognitive variables in determining recall. In Experiment I, which involved subjects from grades kindergarten, third, and sixth, older subjects recalled more incidental as well as relevant information than younger subjects, and although instructions to remember values of a less salient incidental dimension facilitated their recall, the same instructions also facilitated the recall of values of a more salient incidental dimension even though no reference was made to those values. In Experiment II, adult recall of both relevant and incidental information was affected by instructions about differing numbers and types of dimensions. Adults and the oldest children did not differ in total information recalled, and there was no evidence for an increase with age in the cognitive ability to select only that information that was relevant to solving the initial problem. The results were discussed in terms of developmental changes in memory capacity and the absolute salience of the task information.

Children's Use of Component Patterns of Faces in Multidimensional Recall Problems

ODOM, RICARD D., and LEMOND, CAROLYN M. Children's Use of Component Patterns of Faces in Multidimensional Recall Problems. CmLD DEVELOPMENT, 1974, 45, 527--531. Photographs of human faces arranged in a left-to-right array were presented to 6-year-olds and followed by probes to assess the recall of the array location of each photograph. Facial expression and facial identity were varied among the photographs in the array, and the results, like those of perceptual salience research, indicated that recall of the component patterns was affected by the categories to which they belonged. Perceptual sensitization techniques, designed to increase the salience of the expression and identity categories, appeared to affect only the identity category. Overall, the results provide support for the general applicability of a perceptual salience interpretation of the development of problem solving.

Array detection and location of core shadow events

Abstract The spectral features and slowness vector of the PKIKP and PP signals recorded clearly at the Gauribidanur Seismic Array (GBA) from four underground explosions (mb = 5.6, 5.9, 6.2 and 6.6) at the Nevada Test Site (NTS) were studied in detail. From the spectral similarity which characterizes their phase-summed signals, in the band 0.5 cps to 1.5 cps, it has been possible to synthesize reference signals, corresponding to these phases. By “chirping” these signals against the appropriately-phased array beams, the onset of these phases were identified for such events down to mb = 5.3. Application of techniques of velocity and frequency filtering to the GBA records corresponding to 16 well-recorded NTS events (Δ ∼ 127.7° and the San Fernando earthquake of February 9, 1971 Δ ∼ 129.9°) has failed to reveal any precursor to the principal PKP phase which corresponds to the DF branch (PKIKP) of the Bolt (1968) curve. It is found that only the PP phase shows significant spectral differences between the earthquake and the set of explosions investigated.