Software simulation of time delay in teleoperation

Research done in the Space Robotics Laboratory at the University of Atlanta at Huntsville on the effects of time delay on teleoperation is discussed. The laboratory is configured around a Puma 562 robot with 6 degrees of freedom. A custom designed joystick controller with two joysticks, each with three degrees of freedom, is used to control the robot. These joysticks are connected to the robot controller through an analog to digital interface. Joystick calibration, a computer program called Joystick, and the VAL 2 robot control language are discussed

Monovision techniques for telerobots

The primary task of the vision sensor in a telerobotic system is to provide information about the position of the system's effector relative to objects of interest in its environment. The subtasks required to perform the primary task include image segmentation, object recognition, and object location and orientation in some coordinate system. The accomplishment of the vision task requires the appropriate processing tools and the system methodology to effectively apply the tools to the subtasks. The functional structure of the telerobotic vision system used in the Langley Research Center's Intelligent Systems Research Laboratory is discussed as well as two monovision techniques for accomplishing the vision subtasks

2D3D2D: a diagnostic approach to textile and fashion research practice

In the School of Art and Design, at Nottingham Trent University, a range of research methods and practices have developed through PhD and post doctoral study in relation to printed textile design and new technology. Individual research projects have addressed pattern (Bunce 1993); photographic imagery (Briggs 1997); colour (Leak 2001); non-repeating pattern (Carlisle 2003) and 2D/3D (Townsend 2003). Post-doctoral research (Briggs-Goode & Bunce 2001) and Townsend's research into 2D/3D informed a group project and exhibition Transforming Shape (2004). The outcomes created by Gillian Bunce, Amanda Briggs-Goode, Gillian Bunce, Rosemary Goulding and Katherine Townsend explored the relationships between innovative surface imagery and three-dimensional prototypes, based on the simple geometric forms of square, rectangle and circle

Isotropic cosmological singularities 1: Polytropic perfect fluid spacetimes

We consider the conformal Einstein equations for polytropic perfect fluid cosmologies which admit an isotropic singularity. For the polytropic index gamma strictly greater than 1 and less than or equal to 2 it is shown that the Cauchy problem for these equations is well-posed, that is to say that solutions exist, are unique and depend smoothly on the data, with data consisting of simply the 3-metric of the singularity. The analogous result for gamma=1 (dust) is obtained when Bianchi type symmetry is assumed.Comment: LaTeX, 43 pages, no figures, submitted to Ann. Phy

Abnormalities of the ventilatory equivalent for carbon dioxide in patients with chronic heart failure

Introduction. The relation between minute ventilation (VE) and carbon dioxide production (VCO2) can be characterised by the instantaneous ratio of ventilation to carbon dioxide production, the ventilatory equivalent for CO2 (VEqCO2). We hypothesised that the time taken to achieve the lowest VEqCO2 (time to VEqCO2 nadir) may be a prognostic marker in patients with chronic heart failure (CHF). Methods. Patients and healthy controls underwent a symptom-limited, cardiopulmonary exercise test (CPET) on a treadmill to volitional exhaustion. Results. 423 patients with CHF (mean age 63±12 years; 80% males) and 78 healthy controls (62% males; age 61±11 years) were recruited. Time to VEqCO2 nadir was shorter in patients than controls (327±204 s versus 514±187 s; P=0.0001). Univariable predictors of all-cause mortality included peak oxygen uptake (X 2 =53.0), VEqCO2 nadir (X 2 =47.9), and time to VEqCO2 nadir (X 2 =24.0). In an adjusted Cox multivariable proportional hazards model, peak oxygen uptake (X 2 =16.7) and VEqCO2 nadir (X 2 =17.9) were the most significant independent predictors of all-cause mortality. Conclusion. The time to VEqCO2 nadir was shorter in patients with CHF than in normal subjects and was a predictor of subsequent mortality. © 2012 Lee Ingle et al

Experimental Evidence of Non-Linear Dissipation Using Acoustic Micro-Lapses

Non-linear material behaviour is observed experimentally in a laboratory using a new method called Acoustic Micro-Lapses (AML). In this approach, the shooting of two waves is synchronised in a way that the second wave (TW) is to sense the fluctuations in material stiffness induced by the first (PW). The tests include four samples; twenty trials are performed for each sample by increasing time-delays between the waves. The recorded waves are decoupled and compared to determine spectral differences by computing a quantity proportional to the energy difference as function of the increasing time delay (). For a tight sandstone and aluminium samples, the random behaviour of implies that TW finds the same equilibrium conditions as PW. The Lucite and the Berea sandstone depict distinct maxima, implying that TW sensed the transitory perturbations induced by PW. Therefore, it is inferred that PW and TW must propagate with different phase speeds. To assess the previous results, quasi-static modelling is performed using two time delayed step functions. The corresponding creep compliance shows a strong discontinuity when the second step is applied, implying the existence of two unrelaxed moduli. This supports the lab data in that the two waves must have different dispersion relations such that they propagate with different speeds

General properties of cosmological models with an Isotropic Singularity

Much of the published work regarding the Isotropic Singularity is performed under the assumption that the matter source for the cosmological model is a barotropic perfect fluid, or even a perfect fluid with a $\gamma$-law equation of state. There are, however, some general properties of cosmological models which admit an Isotropic Singularity, irrespective of the matter source. In particular, we show that the Isotropic Singularity is a point-like singularity and that vacuum space-times cannot admit an Isotropic Singularity. The relationships between the Isotropic Singularity, and the energy conditions, and the Hubble parameter is explored. A review of work by the authors, regarding the Isotropic Singularity, is presented.Comment: 18 pages, 1 figur

Does the Sun Shrink with Increasing Magnetic Activity?

We have analyzed the full set of SOHO/MDI f- and p-mode oscillation frequencies from 1996 to date in a search for evidence of solar radius evolution during the rising phase of the current activity cycle. Like Antia et al. (2000), we find that a significant fraction of the f-mode frequency changes scale with frequency; and that if these are interpreted in terms of a radius change, it implies a shrinking sun. Our inferred rate of shrinkage is about 1.5 km/y, which is somewhat smaller than found by Antia et al. We argue that this rate does not refer to the surface, but rather to a layer extending roughly from 4 to 8 Mm beneath the visible surface. The rate of shrinking may be accounted for by an increasing radial component of the rms random magnetic field at a rate that depends on its radial distribution. If it were uniform, the required field would be ~7 kG. However, if it were inwardly increasing, then a 1 kG field at 8 Mm would suffice. To assess contribution to the solar radius change arising above 4Mm, we analyzed the p-mode data. The evolution of the p-mode frequencies may be explained by a magnetic^M field growing with activity. The implications of the near-surface magnetic field changes depend on the anisotropy of the random magnetic field. If the field change is predominantly radial, then we infer an additional shrinking at a rate between 1.1-1.3 km/y at the photosphere. If on the other hand the increase is isotropic, we find a competing expansion at a rate of 2.3 km/y. In any case, variations in the sun's radius in the activity cycle are at the level of 10^{-5} or less, hence have a negligible contribution to the irradiance variations.Comment: 10 pages (ApJ preprint style), 4 figures; accepted for publication in Ap

Pseudo-dissection of ascending aorta in inferior myocardial infarction

Acute aortic dissection is a cardiac emergency which can present as inferior myocardial infarction. It has high morbidity and mortality requiring prompt diagnosis and treatment. Rapid advances in non-invasive imaging have facilitated the early diagnosis of this condition and in ruling out this potentially catastrophic illness. We report an interesting case of a 57-year old man who presented with inferior myocardial infarction requiring thrombolysis and temporary pacing wire for complete heart block. An echocardiogram was highly suspicious of aortic dissection. CT scan confirmed that the malposition of the temporary pacing wire through the aorta mimicked aortic dissection