Search results for "Shadow"
showing 10 items of 119 documents
Measurements of integrated direct, diffuse and global ultraviolet-B radiation
2015
Abstract We present the first multiyear set of simultaneous measurements of the global ultraviolet-B radiation and its two components: direct and diffuse. The measurements have been taken with four YES-UVB-1 radiometers: two radiometers to measure the diffuse radiation, one provided with a shadow band and the other with a shadow disk on a Sun tracker; a radiometer to measure the global horizontal radiation; and a Sun-tracking radiometer to measure the direct radiation with an especially designed radiance collimator. The diffuse minute-values measured with both instruments agree within a coefficient correlation of 1.00. The diffuse component represents at least 50% of the global UVB (ultravi…
Sign problem of the fermionic shadow wave function
2014
We present a whole series of methods to alleviate the sign problem of the fermionic shadow wave function in the context of variational Monte Carlo. The effectiveness of our techniques is demonstrated on liquid ^{3}He. We found that although the variance is reduced, the gain in efficiency is restricted by the increased computational cost. Yet, this development not only extends the scope of the fermionic shadow wave function, but also facilitates highly accurate quantum Monte Carlo simulations previously thought not feasible.
Observer for a thick layer of solid deuterium-tritium using backlit optical shadowgraphy and interferometry.
2007
Our work is in the context of the French "laser megajoule" project, about fusion by inertial confinement. The project leads to the problem of characterizing the inner surface, of the approximately spherical target, by optical shadowgraphy techniques. Our work is entirely based on the basic idea that optical shadowgraphy produces "caustics" of systems of optical rays, which contain a great deal of 3D information about the surface to be characterized. We develop a method of 3D reconstruction based upon this idea plus a "small perturbations" technique. Although computations are made in the special "spherical" case, the method is in fact general and may be extended to several other situations.
Determination of projection geometry from quantitative assessment of the distortion of spherical references in single-view projection radiography
2004
A method is introduced, inferring the three-dimensional (3-D) location from the 2-D radiographic shadow of an opaque spherical reference body of known radius by considering its elliptical distortion, the 2-D shadow location and a known source-to-receptor distance. Three noncollinear spheres fixed to a rigid object constitute all possible degrees of freedom, i.e., the entire 3-D imaging geometry. The method may be used (a) to determine the 3-D imaging geometry from a single 2-D view and (b) to correct for foreshortening of object distances coplanar with the plane defined by the sphere triplet. Apart from the mathematical background the article describes a small feasibility experiment, perfor…
Observation of the cosmic ray moon shadowing effect with the ARGO-YBJ experiment
2011
Cosmic rays are hampered by the Moon and a deficit in its direction is expected (the so-called Moon shadow). The Moon shadow is an important tool to determine the performance of an air shower array. Indeed, the westward displacement of the shadow center, due to the bending effect of the geomagnetic field on the propagation of cosmic rays, allows the setting of the absolute rigidity scale of the primary particles inducing the showers recorded by the detector. In addition, the shape of the shadow permits to determine the detector point spread function, while the position of the deficit at high energies allows the evaluation of its absolute pointing accuracy. In this paper we present the obser…
Looking for the Easy Way Out : Demographic Panic and the Twists and Turns of Long-Term Care Policy in Finland
2019
This chapter aims to map the twists and turns in the development of long-term care policy in Finland since the start of the 1990s. The main argument of the chapter is that these changes have to a large part been motivated by what is called here ‘demographic panic’, that is, fear of consequences of population ageing to the public purse. Various policy changes have taken place during the last three decades. Since the late 1980s, Finnish long-term care policies have been made under the shadow of the ‘demographic time bomb’ discourse that argues that care expenditures are to rise exponentially if determined action is not taken to curb the expenditures. As a result, the focus of policy has been …
Primo Levi: luci e ombre
2021
The article lists the significant occurrences of the twofold element of light and darkness in Primo Levi’s published works. After a methodological introduction, which highlights premises and purposes of this starting research, the article provides an overview following an order by literary genre: poetry, narrative, essay writing. The last chapter lists the relevant occurrences of the “gray” colour in the edited books before I Sommersi e I salvati, in order to identify a possible birthplace of the well-known notion “gray zone” and to detect Levi’s earlier use of the gray colour as an attribute of moral ambiguity.
Texture Guided Active Appearance Model Propagation for Prostate Segmentation
2010
Fusion of Magnetic Resonance Imaging (MRI) and Trans Rectal Ultra Sound (TRUS) images during TRUS guided prostate biopsy improves localization of the malignant tissues. Segmented prostate in TRUS and MRI improve registration accuracy and reduce computational cost of the procedure. However, accurate segmentation of the prostate in TRUS images can be a challenging task due to low signal to noise ratio, heterogeneous intensity distribution inside the prostate, and imaging artifacts like speckle noise and shadow. We propose to use texture features from approximation coefficients of Haar wavelet transform for propagation of a shape and appearance based statistical model to segment the prostate i…
The Life, Death and Miracles of Alan Mathison Turing
2010
The life of Alan Turing is described in many biographies. The best and most encyclopaedic of these is that of Andrew Hodges; quite pleasant is the agile volume by Gianni Rigamonti, Turing, il genio e lo scandalo (Flaccovio editore, Palermo, 1991). Both of these also make mention of his tragic end, which certainly casts a shadow on the mores English society at the time; but of course, who knows how other societies might have behaved?
Metal-Insulator Transition of Solid Hydrogen by the Antisymmetric Shadow Wave Function
2016
We revisit the pressure-induced metal-insulator-transition of solid hydrogen by means of variational quantum Monte Carlo simulations based on the antisymmetric shadow wave function. In order to facilitate studying the electronic structure of large-scale fermionic systems, the shadow wave function formalism is extended by a series of technical improvements, such as a revised optimization method for the employed shadow wave function and an enhanced treatment of periodic systems with long-range interactions. It is found that the superior accuracy of the antisymmetric shadow wave function results in a significantly increased transition pressure.