Ambiguous Measurements Research Articles

First‐break timing: Arrival onset times by direct correlation

In attenuating media, pulse characteristics evolve with propagation distance and saturation or pressure‐dependent changes in rock properties. This nonstationarity of the waveform complicates determination of meaningful traveltimes. As a result, depending on the time‐picking criteria used, substantially different values of interval velocity can be obtained. This problem is particularly severe in high‐frequency laboratory time‐of‐flight measurements on porous rock. A potentially less ambiguous measure of wave speed is the signal velocity that is calculated using the pulse onset time. Here, a semiautomated method is developed to determine this onset time in high‐fidelity, pressure‐dependent core measurements. The greatest value of Pearson’s correlation coefficient between segments of observed waveforms near the pulse onset and at an appropriate reference serves as the time determination criterion. Tests of the method on artificial data suggest the signal velocity may be determined to better than 0.3% for −60 dB noise or 1.2% for −37 dB noise. A real data set is tested, comprised of a series of ultrasonic (1 MHz) velocity measurements in microcracked rock to confining pressures of 300 MPa (∼45,000 psi). At the lowest confining pressure, where attenuation is greatest, signal onset and more conventionally derived traveltimes differ by more than 4%. This large discrepancy illustrates that care should be exercised when determining velocity in such attenuating materials. Conversely, the consistency of waveform attributes, such as the difference between the onset time and the first peak time or the apparent quality factor, is useful when estimating intrinsic material velocities in low‐porosity, microcracked carbonate and metamorphic rocks at high confining pressures.

Track fitting with ambiguities and noise: A study of elastic tracking and nonlinear filters

We present a study of track fitting in the presence of ambiguous measurements and noise. We consider four methods for solving the resulting assignment problem, two elastic arm algorithms and two nonlinear filters, including a novel development, the Deterministic Annealing Filter. We describe their basic features and investigate their relationships with each other and with other popular estimators, in particular with the EM algorithm. The performance of the methods is optimized by means of several simulation experiments. We study the influence of the annealing schedule on the performance and show that the application of advanced minimization methods is required in order to obtain reliable estimates of the track parameters. We compare the relative efficiencies and the computational costs of the four methods both under ideal conditions and with noise. A final experiment under realistic conditions focuses on the robustness of the proposed approach.

Plasticity of continuous fiber-reinforced metals

Continuous parallel alumina fiber-reinforced metals produced by pressure infiltration are tested in tension/compression along the fiber axis with a goal of measuring the influence exerted by long fibers on the flow stress of their matrix. In this configuration, the equistrain rule of mixtures, modified to take into account stresses due to differential lateral contraction, can be used to back-calculate the matrix flow stress from that of the composite. This method provides the least physically ambiguous measurement of matrix flow stress in the composite; however, experimental uncertainty can be high. This uncertainty is evaluated in detail for the present experiments, in which matrix in situ stress-strain curves are measured for cast 3M NEXTEL 610 and DUPONT FIBER FP reinforced pure and alloyed aluminum- and copper-based matrices of varying propensity for recovery and cross-slip. Within experimental uncertainty, data show no enhanced matrix work-hardening rates such as those those that have been measured with tungsten fiber-reinforced copper. It is found that the fibers alter the matrix plastic flow behavior by increasing the flow-stress amplitude of the matrix, and by rendering initial yield in compression more progressive than in initial tension. Essentially, all observed features of matrix/fiber interaction can be rationalized as attributable to dislocation emission in the matrix caused by thermal mismatch strains within the material during composite cooldown from processing temperatures.

Social categorization and category attribution: The effects of comparative and normative fit on memory and social judgment

The present study examined the effects of comparative and normative fit on categorization in memory and social category attribution. We set forth conflicting predictions about the effects of these manipulations. Based on Taylor, Fiske, Etcoff & Ruderman's (1978) perceptual salience hypothesis, social category salience was expected to be stronger when counter‐normative rather than normative category exemplars were presented. On the other hand, according to Oakes (1987) functional perspective on category salience, a reversed pattern of results was hypothesized. Our results contradicted Taylor's social‐cognitive approach and supported the Oakes predictions. In our experiment, social categorizations were activated to the extent that they provided a meaningful representation of social relationships. Social category salience was determined by both the relations between the persons compared (comparative fit) and the agreement between stimulus persons compared and perceivers pre‐existing stereotypical beliefs (normative fit). Furthermore, as hypothesized, we found evidence for differences in nature of both dependent measures. Specifically, it was shown that the attribution measure is a less ambiguous measure of social category salience than the category confusion paradigm (Taylor et al., 1978). Findings are discussed in regard to social identification, stereotype maintenance and current research on subtyping.

Prime sequences for asynchronous pulse repetition interval agile radar

We propose the use of prime sequences in pulse repetition agile radar to increase the immunity of the radar to reconnaissance and deceptive jamming. The prime sequences are mapped into state agile mapped (SAM) sequences and are used to determine the pulse repetition interval (PRI) of the radar. We show that this produces a system with low mutual interference between radars and with a low probability of ambiguous range measurement resulting in good resistance to active deceptive jamming.

Discussion on: ‘IM3HT Algorithm: A Joint Formulation of IMM and MHT for Multi-target Tracking’ by R. Torelli, A. Graziano and A. Farina

This paper considers the detection and tracking of dim targets for multiple pulse repetition frequency (PRF) pulsed Doppler radar systems through the use of multi-frame track-before-detect (TBD) methods. The main challenge is that each measurement frame is a mixture with measurements recorded, periodically, at different PRF settings, thus with different range and Doppler ambiguities. To achieve this goal, we propose variable step size multi-PRF and multi-frame (or scan) TBD (MP-MF-TBD) algorithm. Specifically, by incorporating the ambiguity factors related to both the range and velocity ambiguities, MP-MF-TBD first accomplishes the target SNR integration directly using multiple ambiguous measurement frames. After analyzing the properties of the over-threshold tracks, we further propose an efficient detection procedure, which can effectively eliminate the false tracks caused by the measurement ambiguities and accomplish the target kinematic state estimation and multi-PRF ambiguity resolution simultaneously. The proposed MP-MF-TBD does not require certain limitations on the PRF type (i.e., low, medium and high PRF) or the number of PRFs in pulsed Doppler radar systems, and appears to be robust to the target loss when target fall into a blind frequency band of certain PRFs. Extensive numerical simulations demonstrated the efficacy of the proposed MP-MF-TBD by comparing with classical techniques.

Humans as Ritual Victims in the Later Prehistory of Western Europe

The paper presented here addresses the issue of how far current evidence permits the admittance of ritual murder or human sacrifice in the European Iron Age. It argues from two basic premises: firstly that the notion of human sacrifice is the more acceptable within the context of strictly hierarchical, slave‐owning societies for whom human life was not, of itself, sacrosanct; secondly that, since there is a solid body of both literary and archaeological evidence for human sacrifice in antiquity, there is no intrinsic reason to deny its presence in later European prehistory. However, scrutiny of the data reveals that, if human sacrifice did take place in Iron Age Europe, it appears to have been both rare and special. More importantly, virtually all the evidence has a measure of ambiguity and is capable of alternative interpretation.

Tourism and legends archaeology of Heritage

The heritage industry and archaeology have had an uneasy relationship in the United Kingdom, a country with several sites and monuments of world touristic importance. This paper explores this interface within a distinctive locality, the village and Castle at Tintagel, Cornwall, where Arthurian legendary and literary associations have come to dominate many visitors’ expectations. The site is analysed as an integrated ‘‘heritage complex’’, where the commercial, literary and officio-academic ‘‘signs’’ currently create a measure of ambiguity and uncertainty for the casual visitor. The nature of the dilemma for officio-academic interpretation of the site is considered, as are ideas circulating among archaeologists vis-à-vis the provision of alternative accounts of the meaning and context of the complex as a whole.

Relations among Measures of Job Satisfaction, Role Conflict, and Role Ambiguity for a Sample of Greek Teachers

Scores on a measure of job satisfaction and their relation with scores on role conflict and role ambiguity were examined among 100 teachers (60 in primary schools and 40 in secondary schools) in Greece. Correlations for scores on Job Satisfaction with Role Conflict, and Ambiguity were inverse. In particular, scores on Role Conflict were correlated (–.45 with those on Supervision, –.37 with Working Conditions, and –.47 with Organization as a Whole), while scores on Role Ambiguity were correlated –.37 with scores on Work Itself and –.45 with those on Supervision.

Variants of Open Adoptions

SUMMARY This analysis begins with the argument that conceptual ambiguity and related measurement inconsistencies have surfaced in the growing number of studies about open adoption -because the term subsumes a range of possibilities of contact between birth and adoptive families, as well as other sources of variation which affect the developing post-placement relationship between members of these two families. It then turns to the first report from a longitudinal study of adoptive (n = 41) and associated birth parents (n = 26) based on initial face-to-face (within six months of the placement); subsequent follow-up (telephone) interviews (18 months to two years post-placement) with these families and observations from over three years of fieldwork in the private agency which arranged these adoptions. Three post-placement patterns are identified and distinguished: Rejecters, Acceptors and Embracers. The paper concludes with a discussion about enabling conditions for successful post-placement openness.

Simplifying cartographic boundaries by using a normalized measure of ambiguity

This paper presents a method for smoothing noisy cartographic boundaries. The resulting smoothed description preserves the basic shape of the contour while smoothing out noise and unwanted detail. The performance of any simplification method relies on the quality of the levels of smoothing that represent the structures present. In our formulation the most important levels that best describe a given contour are determined by examining a measure of redundancy between each two successive smoothed curvature graphs along the boundary. These levels correspond to the locations of the local minima of such a measure of redundancy. Experimental results are presented showing that complicated planar curves such as cartographic boundaries can be smoothed to a high accuracy. It is proven also that an exaggerated noise added to the boundary can be handled by our method. The simplification therefore is reliable, robust, and very efficient.

The Testing Principle: Inductive Reasoning and the Ellsberg Paradox

We postulate the Testing Principle : that individuals ''act like statisticians'' when they face uncertainty in a decision problem, ranking alternatives to the extent that available evidence allows. The Testing Principle implies that completeness of preferences, rather than the sure-thing principle, is violated in the Ellsberg Paradox. In the experiment, subjects chose between risky and uncertain acts in modified Ellsberg-type urn problems, with sample information about the uncertain urn. Our results show, consistent with the Testing Principle, that the uncertain urn is chosen more often when the sample size is larger, holding constant a measure of ambiguity (proportion of balls of unknown colour in the urn). The Testing Principle rationalises the Ellsberg Paradox. Behaviour consistent with the principle leads to a reduction in Ellsberg-type violations as the statistical quality of sample information is improved, holding ambiguity constant. The Testing Principle also provides a normative rationale for the Ellsberg paradox that is consistent with procedural rationality.

Membrane potential and input resistance are ambiguous measures of sealing of transected cable-like structures

For many years, membrane potential (Vm) and input resistance have been used to characterize the electrophysiological nature of a seal (barrier) that forms at the cut end of a transected axon or other extended cytoplasmic structure. Data from a mathematical and an analog model of a transected axon and other theoretical considerations show that steady-state values of Vm and input resistance measured from any cable-like structure provide a very equivocal assessment of the electrical barrier (seal) at the cut end. Extracellular assessments of injury currents almost certainly provide a better electrophysiological measure of the status of plasma membrane sealing because measurements of these currents do not depend on the cable properties of extended cytoplasmic processes after transection.

On a measure of ambiguity

We consider a general characterization of a measure of ambiguity suggested by Fishburn and investigate the appropriateness of this characterization. It is shown that a number of concepts related to uncertainty and taken from fuzzy logic-measures of fuzziness, measures of specificity, and measures of possibility/certainty interval-satisfy this characterization. In addition, a measure from classical logic indicating the certainty of our knowledge of the truth or falsity of a proposition in the face of a collection of premises also satisfies the characterization of Fishburn. © 1995 John Wiley & Sons, Inc.

X-tron: an incremental connectionist model for category perception

A connectionist model for categorization (self-organization) even in the presence of multiple or mixed patterns has been presented. During self-organization, the network automatically adjusts the number of nodes in the hidden and output layers, depending on the complexity or nature of overlap between the patterns. An ambiguity measure is given based on how well the features are being interpreted by the network. From the ambiguity measure a certainty factor about the decision of the network is derived. The effect of noise on the certainty factor is investigated. A vigilance threshold is used to decide whether the network's decision is correct or not. Functionally the network consists of two parts, one of them categorizes the incoming patterns and the other monitors the performance of categorization. The characteristics of the model has also been demonstrated experimentally on both 1D binary strings and image patterns even when they are corrupted by additive, subtractive, and mixed noise.

Thyroiditis—A model canine autoimmune disease

Publisher Summary This chapter discusses a model canine autoimmune disease that is thyroiditis. Thyroiditis is representative of a large number of autoimmune diseases in which immunological surveillance falters so that self and nonself become confused and the body attacks itself. In human medicine, autoimmunity is the cause of most common endocrine disorders. This appears to be true for dogs as well. A significant measure of the diagnostic ambiguity about canine hypothyroidism stems from our ignorance of the fundamental causes and contributing mechanisms underlying the autoimmune responses of dogs. The development of autoimmune disease generally involves a multistep process: an initiating event produces nonspecific trauma or inflammation that triggers a secondary immune reaction in a genetically predisposed individual. The endocrine gland is progressively destroyed by the autoimmune attack, and as the hormone titers change, clinical symptoms appear. The chapter reviews thyroiditis as a model for research on the general features of canine autoimmunity. One aim is to screen for canine alleles of the major histocompatibility complex (MHC) like those that have been associated with autoimmune disease in people.

Wording Effects in the Measurement of Role Conflict and Role Ambiguity: A Multitrait-Multimethod Analysis

A Multitrait-Multimethod(MTMM) matrix was used to evaluate the effect of item wording (i.e., comfort versus stress-worded) on measures of role conflict and role ambiguity. The results indicated that wording factors explained a significant amount of item variance. Moreover, several substantive correlations between role conflict, role ambiguity, and other constructs (e.g., role overload) were reduced when wording factors were taken into account. These findings point to the need to more fully consider and understand item wording. Future research should determine the cause of wording factors, which may be due to cognitive influences (e.g., carelessness), or may represent unmeasured substantive constructs, such as negative affectivity (NA) or social desirability.

Measuring facets of job ambiguity: Construct validity evidence.

In the past 2 decades, the importance of role ambiguity as an organizational variable has been well established. Recently, researchers have suggested that the lack of an instrument capable of measuring different facets of ambiguity may have impeded both theory development and application of research results. This article presents the development of an instrument capable of tapping 3 distinct aspects of job ambiguity (work method, scheduling, and performance criteria). Data relevant to the reliability, validity, and importance of the job ambiguity measures were gathered in a series of 4 studies. The results of several statistical analyses suggest that the 3 job ambiguity scales are reliable, valid, and meaningful

Wording effects in the measurement of role conflict and role ambiguity: A multitrait-multimethod analysis

A Multitrait-Multimethod(MTMM) matrix was used to evaluate the effect of item wording (i.e., comfort versus stress-worded) on measures of role conflict and role ambiguity. The results indicated that wording factors explained a significant amount of item variance. Moreover, several substantive correlations between role conflict, role ambiguity, and other constructs (e.g., role overload) were reduced when wording factors were taken into account. These findings point to the need to more fully consider and understand item wording. Future research should determine the cause of wording factors, which may be due to cognitive influences (e.g., carelessness), or may represent unmeasured substantive constructs, such as negative affectivity (NA) or social desirability.

University of Alberta norms of relative meaning frequency for 566 homographs

For many models of lexical ambiguity resolution, relative frequency of the different meanings of homographs (words with more than one meaning) is crucial. Although several homograph association norms have been published in the past, none has involved a large number of subjects responding to a large number of homographs, and most homograph norming studies are now at least a decade old. In Experiment 1, associations to 566 homographs were collected from an average of 192 subjects per homograph. Frequency of occurrence for the three most common meanings is reported, along with the corresponding associates, and a measure of the overall ambiguity of each homograph. Homographs whose meanings differed in part of speech were more ambiguous overall than homographs whose different meanings belonged to a single grammatical class. Homographs whose pronunciation depended on meaning (heterophones) were no more ambiguous than nonheterophones, and word frequency was unrelated to overall ambiguity. Estimates of homograph balance across different norming studies were compared, and homographs with two meanings of approximately equal relative meaning frequency (balanced homographs) and homographs with one clearly dominant meaning (polarized homographs) were identified. In Experiment 2, reliability of meaning categorizations was measured for a subset of the homographs in the first experiment. Meaning categorizations were shown to be highly reliable across raters.