Exterior Of Objects Research Articles

Scale-invariance at the core of quantum black holes

We study spherically-symmetric solutions to a modified Einstein–Hilbert action with renormalization group (RG) scale-dependent couplings, inspired by Weinberg’s Asymptotic Safety scenario for quantum gravity. The RG scale is identified with the Tolman temperature for an isolated gravitational system in thermal equilibrium with Hawking radiation. As a result, the point of infinite local temperature is shifted from the classical black-hole horizon to the origin and coincides with a timelike curvature singularity. Close to the origin, the spacetime is determined by the scale-dependence of the cosmological constant in the vicinity of the Reuter fixed point: the free components of the metric can be derived analytically and are characterized by a radial power law with exponent . Away from the fixed point, solutions for different masses are studied numerically and smoothly interpolate between the Schwarzschild exterior and the scale-invariant interior. Whereas the exterior of objects with astrophysical mass is described well by vacuum general relativity, deviations become significant at a Planck distance away from the classical horizon and could lead to observational signatures. We further highlight potential caveats in this intriguing result with regard to our choice of scale-identification and identify future avenues to better understand quantum black holes in relation to the key feature of scale-invariance.

Approximate extraction of late-time returns via morphological component analysis

A fundamental challenge in acoustic data processing is to separate a measured time series into relevant phenomenological components. In the setting of sensing elastic objects using active sonar, we wish to separate the early-time returns (e.g., returns from the object's exterior geometry) from late-time returns caused by elastic or compressional wave coupling. Under the framework of morphological component analysis (MCA), we compare two separation models using the short-duration and long-duration responses as a proxy for early-time and late-time returns. Results are computed for broadside geometries using Stanton's elastic cylinder model as well as experimental data taken from an in-air circular synthetic aperture sonar (AirSAS) system, whose separated time series are formed into imagery. We find that MCA can be used to separate early and late-time responses in both the analytic and experimental cases without the use of time-gating. The separation process is demonstrated to be robust to noise and compatible with AirSAS image reconstruction. The best separation results are obtained with a flexible, but computationally intensive, frame based signal model, while a faster Fourier Transform based method is shown to have competitive performance.

Optimization of cylindrical grinding process parameters on austenitic stainless steel 304 using Taguchi based Grey Relational Analysis

A cylindrical grinding machine is used to grind and form an object's exterior and is generally used in finishing process. Though near-net shape technology is evolving, finishing processes are frequently required to achieve dimensional accuracy and a satisfactory surface quality. Cylindrical grinding machine can operate with different types of shapes, provided the workpiece should have a rotating axis at center. In this study, austenitic SS304 was selected as the material of workpiece. It is used for domestic as well as industrial applications. This research focuses on applying Taguchi technique and Grey Relational Analysis for selecting optimal cylindrical grinding process variables for austenitic stainless steel 304. The process parameters in grinding operation serve as the input factors, the combination of which greatly affects the output responses. The grinding process variables investigated in this research work are workpiece speed, longitudinal feed, transverse feed and flow rate of the coolant. The effect of these grinding factors is analyzed on the performance measures: surface roughness and material removal rate. The experimentation was done based on L9 orthogonal array generated using the Taguchi technique. Further, optimal grinding process parameters (work speed = 20 m/min, longitudinal feed = 6 m/min, transverse feed = 0.02 mm, coolant flow rate = 1.43 l/min) which satisfy both the responses (surface roughness = 0.395 µm and Material Removal Rate = 189.37 mm3/s) were predicted using Grey Relational Analysis.

Adaptive active contours without edges

In this paper, we develop a novel active contour model in PDE (partial differential equation) formulation, which is based on the Chan–Vese “active contours without edges” model and the Sobolev gradient. Our evolution PDE consists of an adaptive force which is derived from the L2 gradient of the fidelity term of the Chan–Vese functional, and a regularized force which is the Sobolev gradient of the contour length. For a two-phase piecewise constant image, we prove that the adaptive force has exactly opposite sign in the interior and exterior of objects, and the zero-level set of the evolution function can match with the boundary between objects and background in a single iteration if the initial function is suitably chosen as a sign-changing and bounded function. The proposed model has the advantages of flexible initialization and very fast segmentation process (so re-initialization is not necessary). The proposed model has been applied to both synthetic and real images with promising results.

Toward the Improvement of Image-Guided Interventions for Minimally Invasive Surgery: Three Factors That Affect Performance

The objectives were to measure the impact of specific features of imaging devices on tasks relevant to minimally invasive surgery (MIS) and to investigate cognitive and perceptual factors in such tasks. Although image-guided interventions used in MIS provide benefits for patients, they pose drawbacks for surgeons, including degraded depth perception and reduced field of view (FOV). It is important to identify design factors that affect performance. In two navigation experiments, observers fed a borescope through an object until it reached a target. Task completion time and object shape judgments were measured. In a motion perception experiment, observers reported the direction of a line that moved behind an aperture. A motion illusion associated with reduced FOV was measured. Navigation through an object was faster when a preview of the object's exterior was provided. Judgments about the object's shape were more accurate with a preview (compared with none) and with active viewing (compared with passive viewing). The motion illusion decreased with a rectangular or rotating octagonal viewing aperture (compared with circular). Navigation performance may be enhanced when surgeons develop a mental model of the surgical environment, when surgeons (rather than assistants) control the camera, and when the shape of the image is designed to reduce visual illusions. Unintentional contact between surgical tools and healthy tissues may be reduced during MIS when (a) visual aids permit surgeons to maintain a mental model of the surgical environment, (b) images are bound by noncircular apertures, and (c) surgeons manually control the camera.

The aesthetic dimension of the psychoanalytic process

This paper brings out one perspective on the experiences of the analytic couple, and transposes it into a general perspective on the analytic process: its aesthetic dimension. It is a combined epistemological and emotional perspective that is open to both participants. By an intense preoccupation with and distance to the object, the subject tries to reconcile the object's exterior form with its imagined content. This perspective offers itself most advantageously in highly emotional situations, in which analyst and analysand feel the pain of being outsiders to each other. They are thrown back on making guesses about the other's intimations. It can bring them into indifference or despair—or it can bring out an aesthetic experience. A situation, until now unbearable, suddenly reveals its surprising potential. The theoretical discussion will be illustrated by a discussion taken from the Talmud and by two clinical examples: one from the psychoanalysis with an infant and her mother, the other with a latency girl. The paper also accounts for the aesthetic as a philosophical and psychoanalytic concept. Some recurrent topics, especially those of form and content, reflect the aesthetic experience as our continuous struggle to reconcile outward form with interior content. This struggle will be formulated as a continuation of the infantile aesthetic conflict, following Meitzer.

Constructive Volume Geometry

We present an algebraic framework, called Constructive Volume Geometryn (CVG), for modelling complex spatial objects using combinational operations. By utilising scalar fields as fundamental building blocks, CVG provides high‐level algebraic representations of objects that are defined mathematically or built upon sampled or simulated datasets. It models amorphous phenomena as well as solid objects, and describes the interior as well as the exterior of objects. We also describe a hierarchical representation scheme for CVG, and a direct rendering method with a new approach for consistent sampling. The work has demonstrated the feasibility of combining a variety of graphics data types in a coherent modelling scheme.