Ambiguous Measurements Research Articles

Treatment motivation: An attempt for clarification of an ambiguous concept

Although the concept of treatment motivation is generally regarded as highly relevant, it has since long been surrounded by conceptual confusion, resulting in miscommunication, ambiguous measures, and contradictory conclusions of research. This article provides an analysis of three major sources of confusion in the conceptualization of treatment motivation: (a) negligence of the concepts' intrinsic relationship with behavior, (b) entanglement of the concept with its determining factors and behavioral consequences, and (c) conceptualization in a stage model. Following the conceptual analysis, causes of the problems and implications for clinical praxis and research are considered. Finally, a more adequate conceptualization of treatment motivation is proposed and suggestions for future research are made.

End-Stopping and the Aperture Problem: Two-Dimensional Motion Signals in Macaque V1

Our perception of fine visual detail relies on small receptive fields at early stages of visual processing. However, small receptive fields tend to confound the orientation and velocity of moving edges, leading to ambiguous or inaccurate motion measurements (the aperture problem). Thus, it is often assumed that neurons in primary visual cortex (V1) carry only ambiguous motion information. Here we show that a subpopulation of V1 neurons is capable of signaling motion direction in a manner that is independent of contour orientation. Specifically, end-stopped V1 neurons obtain accurate motion measurements by responding only to the endpoints of long contours, a strategy which renders them largely immune to the aperture problem. Furthermore, the time course of end-stopping is similar to the time course of motion integration by MT neurons. These results suggest that cortical neurons might represent object motion by responding selectively to two-dimensional discontinuities in the visual scene.

Minimizing the integer ambiguity search space for RTK

Differential GPS carrier phase measurements have much lower noise and multipath error than that of pseudorange measurements. The result is centimeter accuracy for Real-Time Kinematic (RTK). However, the measurement of the carrier phase has a constant unknown integer ambiguity. Several technical issues are related to solving the integer ambiguity correctly. They are: proper stochastic model, search space definition and initialization, search space reduction, state and standard deviation calculation, validation and rejection criteria for the unique and correct candidate. Search space reduction is critically important. It not only affects the ambiguity resolution speed, but also defines the ambiguity resolution success rate. The smaller the search space, the easier it is to find the unique and correct candidate set. The paper analyzes the integer ambiguity search space in its residual domain. The search space is minimized by: Analyzing the maximum independent integer ambiguity measurement set theoretically; Selecting the best initial measurement set that minimizes the search range of each satellite in the set and reduces the error effects from noise that may cause the wrong integer ambiguity solution for the remaining satellites not contained in the initial measurement set.

Propagation algorithms for attitude-related ambiguity resolution

A new approach for ambiguity resolution is presented and tested by means of Monte-Carlo simulations. This approach applies to both single and double phase differences sampled at a given instant, and to any number of baselines and lines of sight, provided the number of lines of sight exceeds a certain threshold. The algorithms are based on the combined global geometry of the baselines and lines of sight and thereby consider all geometric constraints that are inherent in the problem. The algorithms have been programmed and applied to a large number of different configurations of GPS sight lines, and limited to baselines of approximately 1 m in length and the GPS L1 frequency only. The cause of the occurrence of multiple solutions has been investigated. To check the adequacy and limitations of the new algorithms for practical application, it was assessed in which proportion the algorithms either failed to provide a result, provided a false result, or provided a good result as a function of number of baselines, lines of sight and accuracy of the ambiguous phase difference measurements.

Phase-shifted transmission/reflection-type hybrid extrinsic fabry-perot interferometric optical fiber sensors

Conventional interferometric optical fiber sensors, including the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor, have the drawback of ambiguous measurement directions and direction changes, because their signal processing using only fringe counting cannot present measurement direction information, such as tension/compression of strain or increment/decrement of temperature. An EFPI optical fiber sensor constructed with a transmission-type structure (TEFPI optical fiber sensor) can successfully compensate for this problem. However, it has low interferometric fringe visibility and requires somewhat sophisticated signal processing to detect the measurement direction changes. In this research, a hybrid EFPI optical fiber sensor is presented from which transmission-type and reflection-type sensor signals can be simultaneously acquired. The linear combination of the actual transmission-type and reflection-type signals is shown to have a shifted phase from the reflection-type signal according to measurement directions, and thus the phase behavior of lead/lag can present the measurement direction information. Because the hybrid sensor uses separated signals for the measurement quantity and direction, its signal processing is more robust than that of the TEFPI sensor. The sensor and signal processing algorithm were verified with the strain measurement experiments.

Testing models of trophic dynamics: The problem of translating from model to nature

Abstract Mathematical models of interacting populations have a prominent position in population and community ecology, but are often criticized for not being testable. The authors reviewed tests of a particular model, the exploitation ecosystem hypothesis as it was formulated in Oksanen et al. (1981), in order to study problems that may be encountered when testing models. A general problem is how to determine if an experimental system should be regarded as within the model's theoretical domain or not. The theoretical domain defines the type of system the model is meant to apply to. It is noted that both liberal and strict domain definitions can be problematic. Most important is that a too liberal domain definition can result in false understanding (i.e. that it is falsely concluded that the processes included in the model are controlling the study system). Other problems encountered were more system‐specific. Equilibrium predictions were tested in experiments that were too short to reach steady state and in several studies ambiguous definitions and measurements of model variables were found such as productivity, biomass and the number trophic levels. It is concluded that a major obstacle when performing tests is the conceptual and methodological problems encountered when translating model abstractions into an empirical reality.

Women's Physical Activity: Conceptual Issues

Physical activity is essential to life, health, and well-being, and physical inactivity is a major public health problem. Women, especially those of advanced age and members of minority groups, are at particular risk for physical inactivity. The construct of physical activity is associated with conceptual ambiguity and inconsistent measurement strategies, some of which may not be relevant to the physical activity of women. This presents a barrier to meaningful use of the term and precise measurement. This article explores the construct of physical activity and relevant age and gender issues associated with its use and measurement. Selected research studies are reviewed as they pertain to the issues addressed. Implications for research and practice are discussed.

Ambiguity distance : an edge evaluation measure using fuzziness of edges

Most edge detection methods have parameters (threshold values or standard deviation of Gaussian operator for smoothing) to be set, and these parameters make much influence on the outputs of the detectors. In this paper we propose an objective parameter evaluation measure. We evaluate parameters based on the edge ambiguity measures of existence, location and formation. The existence and location ambiguity measures are derived from comparing fuzzy memberships of edgeness with detected edges, and the formation ambiguity measure assesses the connectedness and the total number of edge point in an edge image with respect to the image size. The parameters which produce the least ambiguous edges of a detection method for an image are selected as significant ones. No iterative visual interaction or prior knowledge of edges are needed for these evaluation measures. The effectiveness of the measures is demonstrated by applying the ambiguity measures to synthetic and real images.

FUZZY IMAGE PROCESSING AND RECOGNITION: UNCERTAINTY HANDLING AND APPLICATIONS

Image processing and analysis in fuzzy set theoretic framework is addressed. Various uncertainties involved in these problems and the relevance of fuzzy set theory in handling them are explained. Different image ambiguity measures based on fuzzy entropy and fuzzy geometry of image subsets are mentioned. A discussion is made on the flexibility in choosing membership functions. Illustrations of commonly used fuzzy image processing operations such as enhancement, edge detection segmentation, skeleton extraction, feature extraction are then provided, along with their significance and characteristics. Their applications to some real life problems, e.g., motion frame analysis, remotely sensed image analysis, modeling face images are finally described. An extensive bibliography is also provided.

Neural processing of gravito-inertial cues in humans. II. Influence of the semicircular canals during eccentric rotation.

All linear accelerometers, including the otolith organs, respond equivalently to gravity and linear acceleration. To investigate how the nervous system resolves this ambiguity, we measured perceived roll tilt and reflexive eye movements in humans in the dark using two different centrifugation motion paradigms (fixed radius and variable radius) combined with two different subject orientations (facing-motion and back-to-motion). In the fixed radius trials, the radius at which the subject was seated was held constant while the rotation speed was changed to yield changes in the centrifugal force. In variable radius trials, the rotation speed was held constant while the radius was varied to yield a centrifugal force that nearly duplicated that measured during the fixed radius condition. The total gravito-inertial force (GIF) measured by the otolith organs was nearly identical in the two paradigms; the primary difference was the presence (fixed radius) or absence (variable radius) of yaw rotational cues. We found that the yaw rotational cues had a large statistically significant effect on the time course of perceived tilt, demonstrating that yaw rotational cues contribute substantially to the neural processing of roll tilt. We also found that the orientation of the subject relative to the centripetal acceleration had a dramatic influence on the eye movements measured during fixed radius centrifugation. Specifically, the horizontal vestibuloocular reflex (VOR) measured in our human subjects was always greater when the subject faced the direction of motion than when the subjects had their backs toward the motion during fixed radius rotation. This difference was consistent with the presence of a horizontal translational VOR response induced by the centripetal acceleration. Most importantly, by comparing the perceptual tilt responses to the eye movement responses, we found that the translational VOR component decayed as the subjective tilt indication aligned with the tilt of the GIF. This was true for both the fixed radius and variable radius conditions even though the time course of the responses was significantly different for these two conditions. These findings are consistent with the hypothesis that the nervous system resolves the ambiguous measurements of GIF into neural estimates of gravity and linear acceleration. More generally, these findings are consistent with the hypothesis that the nervous system uses internal models to process and interpret sensory motor cues.

Self-calibrated interferometric-intensity-based optical fiber sensors

This paper presents self-calibrated interferometric-intensity-based optical fiber sensors, which combine for the first time fiber interferometry and intensity-based devices into a single sensor system. The sensor involves an extrinsic Fabry-Perot (FP) interferometric cavity. The broadband light returned from the FP cavity is split into two channels in such a way that one channel has a coherence length much longer than the doubled air-gap separation in the sensor so the FP generates effective interference, while the coherence length in the other channel is so short that no effective interference takes place. As a result, the optical signal in the channel with a long coherence length yields information about the FP cavity length while the signal in the other channel is proportional only to the source power, fiber attenuation, and other optical loss factors in the optical path. To eliminate fringe direction ambiguity and relative measurement limitations associated with interferometric sensors, the sensor is designed such that it is operated over the linear range between a valley and a peak of one interference fringe in the first channel. Moreover, the ratiometric signal-processing method is applied for the signals in the two channels to obtain self-calibrating measurement to compensate for all unwanted factors, including source power variations and fiber bending losses. Various pressure and temperature sensors based on the self-calibrated interferometric/intensity-based scheme are designed, fabricated, and tested. Experimental results show that a resolution as high as 0.02% of full scale can be obtained for both the pressure and temperature measurements.

Situation assessment based on spatially ambiguous multisensor measurements

In most of the requirements met in situation assessment, sensor analysis has to be able to recognize in adverse conditions one hypothesis out of a set of hypotheses concerning, for instance, either the localization, the identity, or the number of targets. Implementing multiple complementary sensors is then of major interest, especially if they have orthogonal spatial resolutions. Nevertheless, when dealing with multiple targets in an area of interest this leads to ambiguities in data association, due to ghosts (erroneous matching), hidden targets, non-detections, and false alarms, and requires a suitable matching process. Furthermore, measurements may have a doubtful origin, and prior knowledge is understood to be often poorly defined, uncertain, or incomplete. So, the present synthesis proposes a generic modeling of this type of information in the framework of the theory of evidence, with closer attention being paid to the different ways data are processed in common cases. The decision process required by any assessment function for the identification of the most likely hypotheses is then discussed, and a global approach of the detection, matching, counting, localization, and classification functions is proposed that aims at exploiting all useful knowledge. The complementary contribution of the different sources of information involved, as well as the suitability of their processing, can be emphasized on a didactic example. © 2001 John Wiley & Sons, Inc.

Tolerance of ambiguity among MD/MBA students: implications for management potential.

Health care is increasingly characterized by uncertainty and turbulence. In an environment of rapid change, flexibility is critical to the success of managers and organizations. Future physician executives must also be open to change and must be able to deal with the uncertainties of management; they must be able to tolerate the ambiguity in management situations. This study uses tolerance of ambiguity measures to analyze students at six medical schools offering dual-degree (MD/MBA) programs. Students enrolled in dual-degree programs were assessed and compared with a control group of traditional medical students. MD/MBA students exhibit a higher tolerance of ambiguity than traditional medical students. As a characteristic associated with leadership ability, tolerance of ambiguity offers a potential indicator of future success as a physician executive. As such, tolerance of ambiguity might be used for selective admissions to medical school and as an indicator of a student's potential to transition between clinical and management functions. As students match personality traits with career choices, those who serve their learning needs must anticipate differences across selected disciplines, roles, and responsibilities.

Coherence Measures on Finite Fuzzy Sets

Comparison tools for fuzzy sets are an indispensable topic. Mostly of this tools deal with fuzzy sets from the view of similarity, order and so forth. A comparison tool based on coherence intuitive concept is presented. For constructing this concept, one start from three basics properties. A development of this tool is presented, equally coherence measures are connected with Fishburn-Yager's ambiguity measures. Two methods for constructing coherence measures are shown: one from ambiguity measures and other from metrics on [0, 1]m. Concretely, has been constructed various coherence measures from different ambiguity measures and different metrics. Equivalency between some coherence measures has been shown. This paper finish with numeric examples presented in order to check coherence measures displayed.

COHERENCE MEASURES ON FINITE FUZZY SETS

Comparison tools for fuzzy sets are an indispensable topic. Mostly of this tools deal with fuzzy sets from the view of similarity, order and so forth. A comparison tool based on coherence intuitive concept is presented. For constructing this concept, one start from three basics properties. A development of this tool is presented, equally coherence measures are connected with Fishburn-Yager's ambiguity measures. Two methods for constructing coherence measures are shown: one from ambiguity measures and other from metrics on [0, 1]m. Concretely, has been constructed various coherence measures from different ambiguity measures and different metrics. Equivalency between some coherence measures has been shown. This paper finish with numeric examples presented in order to check coherence measures displayed.

Particle tracks fitted on the Riemann sphere

We present a novel method of fitting trajectories of charged particles in high-energy physics particle detectors. The method fits a circular arc to two-dimensional measurements by mapping the measurements onto the Riemann sphere and fitting a plane to the transformed coordinates of the measurements. In this way, the non-linear task of circle fitting, which in general requires the application of some iterative procedure, is turned into a linear problem which can be solved in a fast, direct and non-iterative manner. We illustrate the usefulness of our approach by stating results from two simulation experiments of tracks from the ATLAS Inner Detector Transition Radiation Tracker (TRT). The first experiment shows that with a significantly lower execution time, the accuracy of the estimated track parameters is virtually as good as the accuracy obtained by applying an optimal, non-linear least-squares procedure. The second experiment focuses on track parameter estimation in the presence of ambiguous measurements. For this purpose, we have developed a new version of the Elastic Arms algorithm called the Elastic Planes algorithm. The algorithm produces results which are almost identical to the results from an optimal version of the Elastic Arms algorithm. The computational cost of our algorithm, however, is much lower.

Putting the stress back into role stress: improving the measurement of role conflict and role ambiguity

Traditional measures of role conflict and role ambiguity assess the frequency with which a person experiences issues with role expectations. The cognitive model of stress developed by Lazarus and Folkman in 1984 emphasizes that a potentially stressful episode does not actually create distress unless it is appraised as threatening. This study takes the first step towards integrating these two approaches, by adding threat appraisals to the traditional measures of conflict and ambiguity. Surveys were distributed to all employees of an electronics/software firm, measuring role stress, physical and psychological strain, several work related attitudes, and withdrawal behaviors. The new measure of role conflict was more predictive of the strain outcomes than was the traditional measure of role conflict, and in general shows promise as a better way of measuring role stress.

Proton spectroscopic imaging of polyacrylamide gel dosimeters for absolute radiation dosimetry

Proton spectroscopy has been evaluated as a method for quantifying radiation induced changes in polyacrylamide gel dosimeters. A calibration was first performed using BANG-type gel samples receiving uniform doses of 6 MV photons from 0 to 9 Gy in 1 Gy intervals. The peak integral of the acrylic protons belonging to acrylamide and methylenebisacrylamide normalized to the water signal was plotted against absorbed dose. Response was approximately linear within the range 0-7 Gy. A large gel phantom irradiated with three, coplanar 3 × 3 cm square fields to 5.74 Gy at isocentre was then imaged with an echo-filter technique to map the distribution of monomers directly. The image, normalized to the water signal, was converted into an absolute dose map. At the isocentre the measured dose was 5.69 Gy (SD = 0.09) which was in good agreement with the planned dose. The measured dose distribution elsewhere in the sample shows greater errors. A T2 derived dose map demonstrated a better relative distribution but gave an overestimate of the dose at isocentre of 18%. The data indicate that MR measurements of monomer concentration can complement T2-based measurements and can be used to verify absolute dose. Compared with the more usual T2 measurements for assessing gel polymerization, monomer concentration analysis is less sensitive to parameters such as gel pH and temperature, which can cause ambiguous relaxation time measurements and erroneous absolute dose calculations.

THE RELATIONSHIP BETWEEN UNCERTAINTY AND VERTICAL INTEGRATION

This paper shows that uncertainty is a multidimensional theoretical concept, which has empirical implications for the relationship with vertical integration. In a survey of empirical work that tests the relation between uncertainty and vertical integration, this paper demonstrates that performance ambiguity and general measures of uncertainty are positively related with vertical integration, technological uncertainty is negatively related, while market uncertainty and complexity are not systematically related to vertical integration.

Using Newton's law and geophysical bounds on mass density contrast to ensure consistency between gravity and height data

In this paper we advocate the use of Newton's law of gravitational attraction to ensure perfect consistency between gravity and height data. Starting with the absolute gravity on the topography we decompose this signal into a number of quantities associated with physics of the system. To model gravitational attraction from topography we use DTM and Newton's law of gravitational attraction. A residual part of the gravity signal is interpreted as inconsistency between gravity and heights. In the paper we discuss a method by which such inconsistency (at least in principle) can be decomposed into a “gravity error” and a “terrain error”. In practice such separation is not possible because the two types of error are nearly 100% correlated. The inconsistency can be interpreted as a measure of ambiguity of the gravity-terrain models which are consistent with a set of measured/interpolated data. We discuss the influence of such ambiguity on the accuracy of the geoid for the investigated area of Jutland, Denmark.