Mechanical models of amplitude and frequency modulation

This paper presents some mechanical models for amplitude and frequency modulation. The equations governing both modulations are deduced alongside some necessary approximations. Computer simulations of the models are carried out by using available educational software. Amplitude modulation is achieved by using a system of two weakly coupled pendulums, whereas the frequency modulation is obtained by using a pendulum of variable length. Under suitable conditions (small oscillations, appropriate initial conditions, etc) both types of modulation result in significantly accurate and visualized simulations

Introducing a novel mesh following technique for approximation-free robotic tool path trajectories

Modern tools for designing and manufacturing of large components with complex geometries allow more flexible production with reduced cycle times. This is achieved through a combination of traditional subtractive approaches and new additive manufacturing processes. The problem of generating optimum tool-paths to perform specific actions (e.g. part manufacturing or inspection) on curved surface samples, through numerical control machinery or robotic manipulators, will be increasingly encountered. Part variability often precludes using original design CAD data directly for toolpath generation (especially for composite materials), instead surface mapping software is often used to generate tessellated models. However, such models differ from precise analytical models and are often not suitable to be used in current commercially available path-planning software, since they require formats where the geometrical entities are mathematically represented thus introducing approximation errors which propagate into the generated toolpath. This work adopts a fundamentally different approach to such surface mapping and presents a novel Mesh Following Technique (MFT) for the generation of tool-paths directly from tessellated models. The technique does not introduce any approximation and allows smoother and more accurate surface following tool-paths to be generated. The background mathematics to the new MFT algorithm are introduced and the algorithm is validated by testing through an application example. Comparative metrology experiments were undertaken to assess the tracking performance of the MFT algorithms, compared to tool-paths generated through commercial software. It is shown that the MFT tool-paths produced 40% smaller errors and up to 66% lower dispersion around the mean values

Adapting robot paths for automated NDT of complex structures using ultrasonic alignment

Automated inspection systems using industrial robots have been available for several years. The IntACom robot inspection system was developed at TWI Wales and utilizes phased array ultrasonic probes to inspect complex geometries, in particular aerospace composite components. To increase inspection speed and accuracy, off-line path planning is employed to define a series of robotic movements following the surface of a component. To minimize influences of refraction at the component interface and effects of anisotropy, the ultrasonic probe must be kept perpendicular to the surface throughout the inspection. Deviations between the actual component and computer model used for path-planning result in suboptimal alignment and a subsequent reduction in the quality of the ultrasonic echo signal. In this work we demonstrate methods for using the ultrasonic echo signals to adapt a robotic path to achieve a minimal variation in the reflected surface echo. The component surface is imaged using phased array probes to calculate a sparse 3D point cloud with estimated normal directions. This is done through a preliminary alignment path covering approximately 25% of the total surface to minimize the impact on overall inspection time. The data is then compared to the expected geometry and deviations are minimized using least-squares optimization. Compared to manual alignment techniques, this method shows a reduction in surface amplitude variation of up to 32%, indicating that the robot is following the surface of the component more accurately

Dual-release hydrocortisone improves hepatic steatosis in patients with secondary adrenal insufficiency: A real-life study

Background: Conventional glucocorticoid treatment has a significant impact on liver in patients with adrenal insufficiency. Dual-release hydrocortisone (DR-HC) provides physiological cortisol exposure, leading to an improvement in anthropometric and metabolic parameters. We aimed to evaluate the effects of 12-month DR-HC treatment on the hepatic steatosis index (HSI), a validated surrogate index of hepatic steatosis, in patients with secondary adrenal insufficiency (SAI). Methods: A total of 45 patients with hypopituitarism, 22 with hypogonadism, hypothyroidism, ACTH, and GH deficiencies, and 23 with hypogonadism, hypothyroidism, and ACTH deficiency, on replacement therapy for all the pituitary deficiencies, were switched from conventional hydrocortisone to DR-HC. At baseline and after 12 months, glucose and insulin levels, surrogate estimates of insulin sensitivity, and hepatic steatosis were evaluated through ultrasonography and HSI. Results: At diagnosis, ultrasonography documented steatosis in 31 patients (68.8%) while 33 (73.3%) showed high HSI. Hydrocortisone (HC) dose (beta = 1.231, p = 0.010), insulin resistance index (HOMA-IR) (beta = 1.431, p = 0.002), and insulin sensitivity index (ISI)-Matsuda (beta = -1.389, p = 0.034) were predictors of HSI at baseline. After 12 months of DR-HC, a significant decrease in body mass index (BMI) (p = 0.008), waist circumference (WC) (p = 0.010), fasting insulin (p = 0.041), HOMA-IR (p = 0.047), HSI (p < 0.001) and number of patients with HSI > 36 (p = 0.003), and a significant increase in sodium (p < 0.001) and ISI-Matsuda (p = 0.031) were observed. HOMA-IR (beta = 1.431, p = 0.002) and ISI-Matsuda (beta = -9.489, p < 0.001) were identified as independent predictors of HSI at 12 months. Conclusions: In adults with SAI, DR-HC is associated with an improvement in HSI, regardless of the dose used, mainly related to an improvement in insulin sensitivity

Morphologic grading of emphysema is useful in the selection of candidates for unilateral or bilateral reduction pneumoplasty

Objective: Radiologic morphology of emphysema proves useful in the selection of candidates for bilateral reduction pneumoplasty. We developed a simple morphologic grading system capable of identifying subsets of patients who had maximal functional improvement after unilateral or bilateral operation. Methods: Fifty-two patients who underwent unilateral (n = 34) or bilateral (n = 18) reduction pneumoplasty were evaluated. Emphysema morphology was visually scored by digital roentgenograms and high-resolution computed tomography. In each lung, severity of emphysema (ES), heterogeneity (DHT) and hyperinflation (DHF) degrees, were assessed. Asymmetric ratio of emphysema (ARE) between the lungs was expressed as: higher ES/lower ES scores. Morphometric data were correlated with absolute preoperative-postoperative FEV1 change (Delta FEV1). Results: No difference was found between the unilateral and the bilateral group for ES and DHT. DHF was greater in the bilateral group (3.1 vs. 2.7, P = 0.02) whereas ARE was greater in the unilateral group (1.29 vs. 1.05, P = 0.0001). Stepwise logistic regression extracted as best predictors of maximal Delta FEV1, ARE (odds ratio = 238, Wald test P = 0.04) in the unilateral group, and DHT (odds ratio = 24, P = 0.03) in the bilateral group. Unilateral group Delta FEV1 was greater in patients with ARE greater than or equal to 1.3 (0.44 vs. 0.241, P = 0.02). Bilateral group Delta FEV1 was greater in patients with DEET > 1 (0.50 vs. 0.31 1, P = 0.03). No difference was found when comparing Delta FEV1 resulting from unilateral RP and ARE greater than or equal to 1.3, and bilateral RP (0.44 vs. 0.41 1, not significant). Conclusions: This morphologic grading system identified subsets of patients who had maximal functional benefit from unilateral or bilateral reduction pneumoplasty and might be useful in the preoperative screening of candidates for either approach. (C) 2000 Published by Elsevier Science B.V

Baryon structure in a quark-confining non-local NJL model

We study the nucleon and diquarks in a non-local Nambu-Jona-Lasinio model. For certain parameters the model exhibits quark confinement, in the form of a propagator without real poles. After truncation of the two-body channels to the scalar and axial-vector diquarks, a relativistic Faddeev equation for nucleon bound states is solved in the covariant diquark-quark picture. The dependence of the nucleon mass on diquark masses is studied in detail. We find parameters that lead to a simultaneous reasonable description of pions and nucleons. Both the diquarks contribute attractively to the nucleon mass. Axial-vector diquark correlations are seen to be important, especially in the confining phase of the model. We study the possible implications of quark confinement for the description of the diquarks and the nucleon. In particular, we find that it leads to a more compact nucleon.Comment: 21 pages (RevTeX), 18 figures (eps

A cooperative mobile robot and manipulator system (Co-MRMS) for transport and lay-up of fibre plies in modern composite material manufacture

Composite materials are widely used in industry due to their light weight and specific performance. Currently, composite manufacturing mainly relies on manual labour and individual skills, especially in transport and lay-up processes, which are time consuming and prone to errors. As part of a preliminary investigation into the feasibility of deploying autonomous robotics for composite manufacturing, this paper presents a case study that investigates a cooperative mobile robot and manipulator system (Co-MRMS) for material transport and composite lay-up, which mainly comprises a mobile robot, a fixed-base manipulator and a machine vision sub-system. In the proposed system, marker-based and Fourier transform-based machine vision approaches are used to achieve high accuracy capability in localisation and fibre orientation detection respectively. Moreover, a particle-based approach is adopted to model material deformation during manipulation within robotic simulations. As a case study, a vacuum suction-based end-effector model is developed to deal with sagging effects and to quickly evaluate different gripper designs, comprising of an array of multiple suction cups. Comprehensive simulations and physical experiments, conducted with a 6-DOF serial manipulator and a two-wheeled differential drive mobile robot, demonstrate the efficient interaction and high performance of the Co-MRMS for autonomous material transportation, material localisation, fibre orientation detection and grasping of deformable material. Additionally, the experimental results verify that the presented machine vision approach achieves high accuracy in localisation (the root mean square error is 4.04 mm) and fibre orientation detection (the root mean square error is 1.84 18) and enables dealing with uncertainties such as the shape and size of fibre plies

Predictive factors of polycystic ovary syndrome in girls with precocious pubarche

Objective: The aim of this study is to clarify, in girls with premature pubarche (PP), the influence of premature androgenization on the prevalence of polycystic ovary syndrome (PCOS). Design and patients: Ninety-nine PP girls, 63 who developed PCOS and 36 who did not develop PCOS, were retrospectively included. Clinical, anthropometric, and metabolic parameters were evaluated at the time of diagnosis of PP and after 10 years from menarche to find predictive factors of PCOS. Results: Young females with PP showed a PCOS prevalence of 64% and showed a higher prevalence of familial history of diabetes (P = 0.004) and a lower prevalence of underweight (P = 0.025) than PP-NO-PCOS. In addition, girls with PP-PCOS showed higher BMI (P < 0.001), waist circumference (P < 0.001), total testosterone (P = 0.026), visceral adiposity index (VAI) (P = 0.013), total cholesterol (P < 0.001), LDL-cholesterol (P < 0.001), non-HDL cholesterol (P < 0.001) and lower age of menarche (P = 0.015), ISI-Matsuda (P < 0.001), DIo (P = 0.002), HDL cholesterol (P = 0.026) than PP-NO-PCOS. Multivariate analysis showed that WC (P = 0.049), ISI-Matsuda (P < 0.001), oral disposition index (DIo) (P < 0.001), VAI (P < 0.001), total testosterone (P < 0.001) and LDL-cholesterol (P < 0.001) are independent predictive factors for PCOS in girls with PP. Conclusions: Our study established a strong association between multiple risk factors and development of PCOS in PP girls. These risk factors are predominantly related to the regulation of glucose, lipid, and androgen metabolism. Among these factors, WC, ISI-Matsuda, DIo, VAI, total testosterone, and LDL-cholesterol predict PCOS

Comprehensive simulation of cooperative robotic system for advanced composite manufacturing: A case study

Composite materials are widely used because of their light weight and high strength properties. They are typically made up of multi-directional layers of high strength fibres, connected by a resin. The manufacturing of composite parts is complex, time-consuming and prone to errors. This work investigates the use of robotics in the field of composite material manufacturing, which has not been well investigated to date (particularly in simulation). Effective autonomous material transportation, accurate localization and limited material deformation during robotic grasping are required for optimum placement and lay-up. In this paper, a simulation of a proposed cooperative robotic system, which integrates an autonomous mobile robot with a fixed-base manipulator, is presented. An approach based on machine vision is adopted to accurately track the position and orientation of the fibre plies. A simulation platform with a built-in physics engine is used to simulate material deformation under gravity and external forces. This allows realistic simulation of robotic manipulation for raw materials. The results demonstrate promising features of the proposed system. A root mean square error of 9.00 mm for the estimation of the raw material position and 0.05 degrees for the fibre orientation detection encourages further research for developing the proposed robotic manufacturing system