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Effects of coatings on the quality factor of quartz crystal resonators operating at liquid helium temperature are analyzed. A first set of tests demonstrates the effects of gold and chromium electrodes at low temperature. The second set of tests involves a multilayer tantala/silica coating used to reach an extreme reflectance on mirrors such those used in optical cavities or Michelson interferometers...
Thermoelectric power plants have critical units, such as the boiler and the turbine-generator, which are complex multivariate systems. These units exhibit non-stationary behavior and multiple operational modes that imply constant changes of set points of key performance variables. A methodology based on MSPC (Multivariate Statistical Process Control) techniques and PCA (Principal Component Analysis)...
This paper presents studies and the implementation of a novel grid-connected PV system with storage. The goal of this project is to validate the operation and to determine the benefits and limitations of integrating storage with grid-connected PV systems. The objective is to evaluate the viability of using complementary electricity storage for meeting the local evening peak demands - “night-time peak...
The propagation of partially incoherent optical waves in nonlinear media is a subject of growing interest in different fields, e.g., incoherent solitons (IS), supercontinuum generation, random lasers or rogue waves [1]. In particular, the long term evolution of an incoherent optical wave is known to be characterized by a process of thermalization [2]. It refers to an irreversible evolution of the...
The usual physical picture of supercontinuum SC generation changes profoundly when high power long pulses are injected into a photonic crystal fiber (PCF) which exhibits two zero dispersion wavelengths (ZDWs). Besides the thermalized central part of the incoherent SC spectrum, the analysis reveals that the Raman effect is responsible for the generation of spectral incoherent solitons (SIS) [1] in...
Motion in PET studies degrades the image quality and introduces bias which is critical for high resolution scanners such as mCT, mMR, and HRRT. There are many publications related to motion correction in PET. They consider either Rigid-body or Non Rigid-body motion and use three methods for motion correction. In this work we will describe and compare three motion correction methods. The first method...
The use of Cherenkov light production and timing for TOF PET has been suggested, and there are papers indicating the possibility to improve timing in this way. The present paper, however, focuses only on count rate sensitivity issues by comparing a LSO-LSO system against a potential PbF2 system. This has been accomplished by using a simple two detector set up first looking at LSO-LSO coincidences...
Two region of interest were selected. A hot region is around the Basal Ganglia, and the other region is around the Cerebellum as shown in both figure 2. A time activity curve was then generated for both the hot and cold region for the same study being generated with 2D and 3D scatter correction. Figure 3-a shows the hot region for both scatter 2D and 3D. Both regions have the same trend and value...
A dedicated micro-resonator in a length-extension mode (LEM) has been developing for fundamental physics experiments, aiming to detect the quantum ground state of a resonator. The experiment is based on a high frequency, high quality factor and low mass micro-resonator, implemented in a high finesse Fabry-Perot cavity at cryogenic temperature. Very interesting preliminary measurements have been obtained...
In complete analogy with a system of classical particules colliding inside a gas medium, an incoherent optical field can evolve, owing to nonlinearity, towards a thermodynamic equilibrium state [1]. In this respect, the spatiotemporal dynamics of the light field is governed by the nonlinear Schrodinger equation and its equilibrium spectrum has been determined in the framework of the weak turbulence...
Analytic sensing is a new mathematical framework to estimate the parameters of a multi-dipole source model from boundary measurements. The method deploys two working principles. First, the sensing principle relates the boundary measurements to the volumetric interactions of the sources with the so-called “analytic sensor,” a test function that is concentrated around a singular point outside the domain...
We present a new micromechanical resonator designed for the observation of its quantum ground state (QGS). To reach QGS, a high frequency resonator with the lowest possible mass and the highest possible quality factor, coupled with an extremely sensitive measurement technique, has to be implemented. Using a high-finesse Fabry-Perot cavity with a mirror coated on the resonator, we expect benefits from...
Positron emission tomographs (PET) are currently almost exclusively designed as hybrid systems. The current standard is the PET/CT combination, while prototype PET/MRI systems are being studied by several research groups. One problem in these systems is that the transaxial field of view of the second system is smaller than that of the PET camera. The problem is limited for PET/CT, it is more pronounced...
The Conjugate Gradient (CG) method is an optimization algorithm used to determine the numerical solution of particular systems of linear equations which may be expressed as a symmetric and positive definite matrix. The CG method is iterative, so it can be applied to systems which are too large to be handled by direct methods. The CG method can also be used to solve unconstrained optimization problems...
Loop invariants play a major role in program verification. Though various techniques have been applied to automatic loop invariants generation, most interesting ones often generate only candidate invariants. Thus, a key issue to take advantage of these invariants in a verification process is to check that these candidate loop invariants are actual invariants. This paper introduces a new technique...
Sound translation into neural message at the first auditory synapse is of prime importance for providing organism with sound environment. Here, we compiled experimental features of the primary auditory neurons into a computational model, composed of two distinct compartments (i.e., afferent bouton and axon). Simulation of the model closely reproduces the whole biophysical properties of both excitatory...
The Siemens MR/PET-hybrid BrainPET scanner allows the simultaneous acquisition of PET listmode data and MR sequences. The full benefit of the 3D listmode data in terms of image quality is realised with a novel LOR space reconstruction based on PRESTO (PET REconstruction Software TOolkit). A pre-calculated, memory-resident system matrix has been applied for the iterative MLEM/OSEM reconstruction taking...
Iterative reconstruction has several advantages over analytical cone-beam reconstruction methods for three-dimensional x-ray computed tomography. Iterative methods tend to incorporate both system and statistical models which yield a better signal to noise ratio. Iterative reconstruction also produces adequate image quality at low count, enabling low-dose X-ray CT studies, at the expense of computational...
THE Siemens HRRT scanner is a complex PET tomograph, using 8 LSO/LYSO panel detectors and Depth Of Interaction(DOI) with a total of 119908 detector crystals. The Direct Normalization (DN) is the standard method used for sinogram-mode reconstruction. This paper investigates the use of an improved component-based normalization method for HRRT sinogram reconstruction. This method is originally used for...
Iterative 3D PET reconstruction represents a very computational challenge due to the large number of lines of response (LOR) collected for each data set. This iterative 3D reconstruction also needs a lot of iterations to achieve an acceptable PET reconstructed image. A preconditioned conjugate gradient (PCG) method was previously shown to have faster convergence rate than expectation maximization...
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