Angular Index Research Articles

Determination of Laser Tracker Angle Encoder Errors

Errors in the angle encoders of a laser tracker may potentially produce large errors in long range coordinate measurements. To determine the azimuth angle encoder errors and verify their values stored in the tracker’s internal error map, several methodologies were evaluated, differing in complexity, measurement time and the need for specialised measuring equipment. These methodologies are: an artefact-based technique developed by NIST; a multi-target network technique developed by NPL; and the classical precision angular indexing table technique. It is shown that the three methodologies agree within their respective measurement uncertainties and that the NPL technique has the advantages of a short measurement time and no reliance on specialised measurement equipment or artefacts.

Vortex structure of elegant Laguerre–Gaussian beams of fractional order

The transition of the vortex structure of fractional elegant Laguerre-Gaussian beams is discussed in detail as the angular mode index of the beam is continuously varied between integer values. Under this kind of variation, the vortices can be classified into five groups. Contrary to the behavior of the vortices of the nondiffracting Bessel beams of fractional order, the nodal lines of the vortices in the case of the fractional eLG beams exhibit intricate shapes.

Parallel Diagnosis Model of Fatigue Driving Based on Vehicle Running Status

To replenish the drowsy driving samples, the parallel diagnostic model with model analysis and signal analysis is developed for the fatigue driving prediction. The preview optimal artificial neural network and driver fatigue behavior model are applied to make mathematical models of the drowsy driving. The fatigue model for forward analysis is able to achieve the vehicle running status data, e.g. Steering wheel angle, the vehicle's yaw rate, lateral acceleration and other running parameters when the driver is fatigue. The driving fatigue model for inverse analysis is able to achieve the driver's state based on the vehicle running status data. To extract necessary characteristics of risk driving state, a method based on steering angle index (Amp_D2_Theta) and steering wheel angular velocity index (Amp_D2_Theta) is developed in this paper. It can overcome limitations of using a single index to describe the fatigue driving behavior. A comprehensive set of fatigue driving simulation tests is conducted to verify feasibilities of the parallel diagnostic model for fatigue driving. Driving simulator’s experimental results show that the parallel diagnostic model in driving fatigue diagnosis is feasible and efficient.

COMPARISON OF POINT MATCHING TECHNIQUES FOR ROAD NETWORK MATCHING

Abstract. Map conflation investigates the unique identification of geographical entities across different maps depicting the same geographic region. It involves a matching process which aims to find commonalities between geographic features. A specific subdomain of conflation called Road Network Matching establishes correspondences between road networks of different maps on multiple layers of abstraction, ranging from elementary point locations to high-level structures such as road segments or even subgraphs derived from the induced graph of a road network. The process of identifying points located on different maps by means of geometrical, topological and semantical information is called point matching. This paper provides an overview of various techniques for point matching, which is a fundamental requirement for subsequent matching steps focusing on complex high-level entities in geospatial networks. Common point matching approaches as well as certain combinations of these are described, classified and evaluated. Furthermore, a novel similarity metric called the Exact Angular Index is introduced, which considers both topological and geometrical aspects. The results offer a basis for further research on a bottom-up matching process for complex map features, which must rely upon findings derived from suitable point matching algorithms. In the context of Road Network Matching, reliable point matches provide an immediate starting point for finding matches between line segments describing the geometry and topology of road networks, which may in turn be used for performing a structural high-level matching on the network level.

Differences in Standing and Sitting Postures of Youth with Idiopathic Scoliosis from Quantitative Analysis of Digital Photographs

ABSTRACTThe objective of this study was to explore whether differences in standing and sitting postures of youth with idiopathic scoliosis could be detected from quantitative analysis of digital photographs. Standing and sitting postures of 50 participants aged 10–20-years-old with idiopathic scoliosis (Cobb angle: 15° to 60°) were assessed from digital photographs using a posture evaluation software program. Based on the XY coordinates of markers, 13 angular and linear posture indices were calculated in both positions. Paired t-tests were used to compare values of standing and sitting posture indices. Significant differences between standing and sitting positions (p < 0.05) were found for head protraction, shoulder elevation, scapula asymmetry, trunk list, scoliosis angle, waist angles, and frontal and sagittal plane pelvic tilt. Quantitative analysis of digital photographs is a clinically feasible method to measure standing and sitting postures among youth with scoliosis and to assist in decisions on therapeutic interventions.

Evaluation of Aggregate Size and Shape by Means of Segmentation Techniques and Aggregate Image Processing Algorithms

Morphological properties of mineral aggregates are known to affect pavement and railroad track mechanistic behavior and performance significantly in relation to strength, modulus, and permanent deformation. With imaging technology, an objective and accurate measurement of aggregate particle size and shape properties can be obtained in a rapid, reliable, and automated fashion. But these advances in aggregate imaging must be brought to project sites and quarries in the field. This paper introduces field image-acquisition and image-processing techniques for extraction and analyses of size and shape properties of individual aggregate particles. Referred to as segmentation techniques, image-processing methods developed in this study analyzed two-dimensional field images of aggregates captured by a digital single-lens reflex camera. The segmented aggregate images were fed into the validated University of Illinois aggregate image analyzer to quantify particle size and shape properties by means of its image-processing algorithms for flat-and-elongated ratio, angularity index, and surface texture index. The developed method successfully determined the properties of coarse-aggregate samples collected from various depths in a layer of railroad track ballast. The promising preliminary results indicate that these segmentation techniques could be considered in the field for capturing several aggregate particles rapidly and reliably in a single image so that (a) size and shape properties of individual particles could be analyzed and (b) both spatial property variability and property changes with layer depth and usage (i.e., property degradation in time) could be evaluated under service loading.

Effectiveness of a new evaluation index of bicycle pedaling skill–Angular Velocity Variability Index

Effectiveness of a new evaluation index of bicycle pedaling skill–Angular Velocity Variability Index

Evaluation of image analysis methods used for quantification of particle angularity

AbstractAngularity is an important parameter in the characterization of particle morphology that is used to interpret the transport history of particles in sedimentary deposits. In the past, visual classification using silhouette charts was widely used to determine particle angularity, but this approach is subjective and time‐consuming. With advances in modern image analysis techniques and low‐cost software packages, it is possible to rapidly quantify particle angularity more objectively than using visual classification methods. This study re‐examines the performance of three existing image analysis methods and one new image analysis procedure, applied to six rock and sediment samples that were visually different in angularity. To facilitate comparison between the angularity results, measurements were reduced to rankings for each aggregate sample. These results show that the four image analysis methods rank the angularity of the samples differently, and that none rank the mean angularity index in the same order as the angularity ranking using visual classification. Therefore, further research is needed to develop an image analysis method that can quantify the angularity of sedimentary particles more precisely.

Craniofacial morphology and obstructive sleep apnoea-hypopnoea syndrome: a craniometric comparative analysis

The aim of this study was to define the relationship between paediatric obstructive sleep apnoea-hypopnea syndrome (OSAHS) and craniofacial morphovolumetric features through comparative craniometric analyses between affected children and controls based on conventional cephalometry. Cephalometric examinations of 40 children affected by OSAHS were retrospectively evaluated. Sixteen craniometric landmarks were identified, and 27 linear and angular indices related to craniofacial morphovolumetric features were measured. Subsequently, the same process of identifying landmarks and measuring indices was performed on the cephalometric examinations of 40 controls. For each index, we then calculated in both groups the mean, standard deviation, standard error and p value. By comparing the values obtained in the two series, we calculated the degree of significance of each difference between children with OSAHS and controls using the Student t test. Differences of only 5/27 linear and angular indices considered were not statistically significant between groups, thus confirming susceptibility to the disorder in relation to certain splanchnocranic morphovolumetric features. The most significant differences involved mandibular plane inclination and distance between landmark sella and hyoid bone, a reliable index being the vertical position of the latter. Despite the limitations associated with the 2D nature of conventional cephalometry, mainly related to projection and identification errors, and despite the upright position during examination, we consider the diagnostic value and information content of this technique high, thus reaffirming its role as a first-line imaging investigation in children with sleep-related breathing disorders.

Corrigendum to “Design of precision angular indexing system for calibration of rotary tables” [JMST 26 (3) (2012) 847–855

Corrigendum to “Design of precision angular indexing system for calibration of rotary tables” [JMST 26 (3) (2012) 847–855

Effect of crushed air-cooled blast furnace slag on mechanical properties of concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag (SCR) and crushed limestone (LCR) with 5–20 mm and 20–40 mm gradation were represented by numerical parameters including angularity number (AN) and index of aggregate particle shape and texture (IAPST). The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated. Fracture characteristics of concrete, interfacial structure between aggregates and matrix were analyzed. The experimental results show that porous and rough SCR increases contact area with matrix in concrete, concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste, which may increase interlocking and mechanical bond between aggregate and matrix in concrete. SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR. The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.

An angular vegetation index for imaging spectroscopy data—Preliminary results on forest damage detection in the Bavarian National Park, Germany

A vegetation index (VI) is presented which is calculated as the inner angles of a triangle. The triangle is spanned between three distinct points (on a spectral curve of imaging spectroscopy data) which are defined for each individual pixel by the wavelength (x-axis) and the reflection value (y-axis). The ideal wavelengths of the three points are dependent on the response variable investigated. The case-study within this paper in which this angular VI is applied, aims at the development of an index to automatically detect spruce bark beetle infections in the Bavarian National Park, Germany. In order to determine the optimum wavelengths to separate damaged from non-damaged trees the three-angle-indices (TAIs) for all possible combinations of available wavelengths of HyMap imaging spectroscopy data in the vis–NIR-region (0.455–0.986μm) were calculated. The resulting 27,417 images served as input predictor variables to a genetic algorithm (GA) which used nearest centroid classifier as fitness functions to detect the most stable predictors and separate the six classes (three damage classes) defined within the study area.The fitness functions integrated in the GA reached classification accuracies of up to 94.8% when using forward selection models of the most stable genes featuring maximum 50 predictors. Based on those results, three from the original 27,417 predictors were extracted to map forest damages over the full image extent based on a support vector machines (SVMs) classification. We conducted the same experiment with 82 vegetation indices described in literature and achieved slightly lower GA overall accuracies of 86.8% using the nearest centroid classifier. The SVM maps produced with the three best VI predictors were comparable to the TAI results.

A computed tomography-based comparative cephalometric analysis of the Italian craniofacial pattern through 2,700 years

The aim of our study was to define the changes in morphovolumetric features of neurocranium, basicranium and splanchnocranium in the population of Campania, southern Italy, over the last 2,700 years. This was a very intense period for this region from both historical and evolutionary perspectives and was marked by the succession of colonisations, dominations and invasions by several European and non-European peoples, events that profoundly influenced the original genetic heritage, which subsequently became more complex. Unlike most previous authors, we based our craniometric comparative analysis on multidetector computed tomography (MDCT) studies of contemporary and ancient series dating to between the seventh and fifth centuries B.C. of skulls found in the Etruscan necropolis of Pompei and Pontecagnano. MDCT is extremely reliable in identifying landmarks and measuring linear and angular indices through the use of multiplanar and tridimensional reformations. While highlighting a remarkable stability of 22/32 of the indices considered, as an effect of the role of the genetic heritage in preserving morphovolumetric features in a given population, statistical analysis showed some interesting results: the main changes concerned the splanchnocranium and the occlusion, indicating a higher sensitivity of these districts to environmental factors, mainly related to diet. Conversely, neurobasicranial complex morphovolumetric features remained amazingly intact. In particular, the neurocranium increased in overall capacity in response to the growing brain and changed shape with a progressive shift to a dolichocranic, flattened frontal pattern; the basicranium shape was preserved, as indicated by the stability of the cranial base (NSBa) angle over time. The splanchnocranium, on the contrary, has undergone a dramatic involution, even conditioning gnathic structures with changes in palatal shape (more acute) and in the relationship between the jaws on the sagittal plane, resulting in increased prevalence of Angle's class I and III malocclusions.

Investigation of the shape, size, angularity and surface texture properties of coarse aggregates

The shape, size, angularity and surface texture properties of coarse aggregates were studied in this paper. Aggregates with different shapes were separated manually and the percentage by number of each shape was computed. The three sizes (length, width and thickness) of aggregates were extracted using an image analysis approach and their statistical distributions were studied. An indicator called angularity and surface texture (AT) index was developed to characterize the combined effect of the coarse aggregate angularity and surface texture based on two-dimensional aggregate images. The statistical distributions of the AT indices of different sized limestone and basalt aggregates and their composite AT indices were studied. The void contents of different sized limestone and basalt aggregates in loose condition were tested to validate the AT index.

A Vector-based Approach to Discriminate Radial Deformation and Axial Displacement of Transformer Winding and Determine Defect Extent

The transfer function is a well-known method to detect mechanical defects of transformer windings. After measurement of transfer functions, they must be evaluated to detect any anomaly in transformer windings. One of the main problems in this stage is lack of transparency. This article tries to solve this problem through a vector space-based perspective to diagnose radial deformation and axial displacement of transformer windings. To determine the severity of the winding deformation or displacement, the angular proximity index is used. The measurement results show the effectiveness of this index. Based on the verified model of the transformer, a dimensionality reduction technique is applied to transformer's transfer function to map it from its original high-dimensional vector space to a lower-dimensional one. It is shown that transfer functions of radially deformed and axially displaced windings are well separated visually in the reduced space.

Design of precision angular indexing system for calibration of rotary tables

The indexing table was developed for angle measurements on machine tools. The measuring techniques, which have been reviewed in this paper, are currently available in manufacturing engineering to calibrate the angle measurement. The measuring principles of each equipment are outlined and their capabilities are also discussed. The new indexing table using 6 points kinematic concept and employing ball and vee grooves location was designed and manufactured to calibrate angle errors of rotary tables using a laser interferometer. The manufacturing method was evaluated to manufacture the accurate vee grooves. A special cam was designed and manufactured to translate rotation movement into lift-up and rotation movement. A CNC machining centre and indexing head were used to manufacture the cam. All parts of the new indexing table were manufactured with a manufacturing tolerance according to drawings, squareness and parallelism checked to obey the 6 points kinematic concept. Also these factors controlled the repeatability of the new indexing table. After installing the new indexing table, the performance was evaluated using rotary table operating in both the horizontal and vertical orientations.

Study of orbital angular momentum entangled photons entanglement in atmospheric channel

In this paper, we describe orbital angular momentum entangled photon pair entanglement in atmospheric channel. The Von Karman spectrum of turbulence is used to create a model of two-photon pair entanglement. The effects of atmospheric turbulence on the entanglement of entangled photon pairs of different orbital angular momentum bases are analyzed. The obtained results are as follows because of the presence of atmospheric turbulence, the entanglement of entangled photon pairs decreases with the increase of the propagation distance z in the atmosphere channel. The entanglement of the entangled photon pairs decreases with the increase of transmission distance. The bigger the turbulence intensity, the faster the entanglement decline and the shorter the propagation distanceis. In the same intensity of atmospheric turbulence of the atmospheric channel, the bigger the orbital angular momentum index, the slower the entanglement decline and the further the propagation distanceis.

Comparison of 2D and 3D image-based aggregate morphological indices

Significant progress has been made over the last two decades in the characterisation of aggregate shape using automated image analysis and processing methods. Aggregate shape characteristics have been quantified using three distinct shape parameters, namely the aggregate form, angularity and surface texture. Several mathematical procedures have been developed to quantify these parameters. For practical reasons, most of these procedures were limited to two-dimensional (2D) and utilised 2D aggregate images. This paper investigates the ability of some of the most widely used 2D aggregate form and angularity indices to describe the shape of five different types of aggregates (natural gravel, basalt, granite, diabase and slate). In addition, it provides a comparison between 2D and three-dimensional (3D) aggregate shape indices developed based on fitting the 3D aggregate shape using spherical harmonic functions.

Estimation of vegetation clumping index using MODIS BRDF data

The foliage clumping index quantifies the degree of the deviation of leaf spatial distribution in the canopy from the random case. It is of comparable importance for ecological models as the leaf area index for quantifying radiation interception and distribution in plant canopies. Previously, an improved angular index named normalized difference between hotspot and darkspot was proposed for retrieving the clumping index using multi-angle remote sensing data. Global maps of clumping index have been derived successfully from multi-angular Polarization and Directionality of Earth Reflectance (POLDER) data at ∼6 km resolution. In this article, we investigate whether it is feasible to derive the clumping index at 500 m resolution with the 16-day Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function model parameters product. The results are compared with an assembled set of field measurements from 63 different sites, covering five continents and diverse biomes.

Reliability of a quantitative clinical posture assessment tool among persons with idiopathic scoliosis

Objective To determine overall, test–retest and inter-rater reliability of posture indices among persons with idiopathic scoliosis. Design A reliability study using two raters and two test sessions. Setting Tertiary care paediatric centre. Participants Seventy participants aged between 10 and 20 years with different types of idiopathic scoliosis (Cobb angle 15 to 60°) were recruited from the scoliosis clinic. Main outcome measures Based on the XY co-ordinates of natural reference points (e.g. eyes) as well as markers placed on several anatomical landmarks, 32 angular and linear posture indices taken from digital photographs in the standing position were calculated from a specially developed software program. Generalisability theory served to estimate the reliability and standard error of measurement (SEM) for the overall, test–retest and inter-rater designs. Bland and Altman's method was also used to document agreement between sessions and raters. Results In the random design, dependability coefficients demonstrated a moderate level of reliability for six posture indices ( ϕ = 0.51 to 0.72) and a good level of reliability for 26 posture indices out of 32 ( ϕ ≥ 0.79). Error attributable to marker placement was negligible for most indices. Limits of agreement and SEM values were larger for shoulder protraction, trunk list, Q angle, cervical lordosis and scoliosis angles. The most reproducible indices were waist angles and knee valgus and varus. Conclusions Posture can be assessed in a global fashion from photographs in persons with idiopathic scoliosis. Despite the good reliability of marker placement, other studies are needed to minimise measurement errors in order to provide a suitable tool for monitoring change in posture over time.