Search results for "Computer-aided design"
showing 10 items of 312 documents
Computationally Efficient Analysis of Microwave Injection-Locked Amplifiers
2011
In this paper, some preliminary results on a novel approach to the analysis of injection-locked amplifiers are presented. The proposed method is based on a behavioral block modeling of the circuit in the fundamental-frequency dynamical phasor domain. The first-order exact perturbation refined treatment developed provides, in the end, explicit equations describing the entrained oscillation amplitude and phase dynamics. A secondary simplification then can be adopted in case of low-level injection, to determine a closed form expression for the locking bandwidth, generalizing the well known Adler’s one. By virtue of its semi-analytical nature, the proposed approach turns out to be much more eff…
Analysis of Bias-Shift Effects in Free-Running and Injection-Locked Negative Resistance Oscillators
2012
In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…
VisAdapt: A Visualization Tool to Support Climate Change Adaptation.
2017
In this article we present the design and implementation of the web-based visualization tool VisAdapt, developed to support homeowners in the Nordic countries to assess anticipated climate change and climate related risks which are expected to negatively impact their living conditions. The tool guides the user through a three-step visual exploration process to facilitate the exploration of risks and adaptation measures, specifically adapted to the user. VisAdapt has been developed over the course of two years in close collaboration with domain experts and end users to ensure the validity of the included data and the efficiency of the visual interface. Although VisAdapt is designed for Nordi…
Molecular dynamics, dynamic site mapping, and highthroughput virtual screening on leptin and the Ob receptor as anti-obesity target.
2014
Body weight control is a mechanism finely regulated by several hormonal, metabolic, and nervous pathways. The leptin receptor (Ob-R) is crucial for energy homeostasis and regulation of food uptake. Leptin is a 16 kDa hormone that is mainly secreted by fat cells into the bloodstream, and under normal circumstances, circulating levels are proportionate to the fat body mass. Sensing of elevated leptin levels by the hypothalamic neurocircutry activates a negative feedback loop resulting in reduced food intake and increased energy expenditure. Decreased concentrations lead to opposite effects. Therefore rational design of leptin agonists constitute an appealing challenge in the battle against ob…
A decade of research into player communities in online games
2013
The social dynamics of player communities in online games have been the subject of much research during the last decade. Following a systematic review of empirical research publications from 2000–2010, this article synthesizes the key methods and concepts researchers have used to study and characterize player communities. It also synthesizes the key aspects and operationalizations researchers have concentrated on. The analysis shows that qualitative approaches have been more common than quantitative ones. The concepts used to characterize player communities were often not clearly defined or overlapped in meaning. Yet they revealed a prevalence of micro (groups or teams), meso (guilds or org…
A collaborative virtual reality environment for liver surgery planning
2021
Abstract Surgical planning software is a key component in the treatment of tumor diseases. However, desktop-based systems provide only limited visualization and interaction opportunities. Moreover, collaborative planning among members of a surgical team is only possible to a limited extent. In this work, a collaborative virtual reality (VR) environment to assist liver surgeons in tumor surgery planning is presented. Our aim is to improve virtual resection planning between surgeons in a remote or co-located environment. The system allows surgeons to define and adjust virtual resections on patient-specific organ 3D surfaces and 2D image slices. Changes on both modalities are synchronized, whi…
Automatic segmentation and 3D reconstruction of intravascular ultrasound images for a fast preliminar evaluation of vessel pathologies.
2007
Abstract Intravascular ultrasound (IVUS) imaging is used along with X-ray coronary angiography to detect vessel pathologies. Manual analysis of IVUS images is slow and time-consuming and it is not feasible for clinical purposes. A semi-automated method is proposed to generate 3D reconstructions from IVUS video sequences, so that a fast diagnose can be easily done, quantifying plaque length and severity as well as plaque volume of the vessels under study. The methodology described in this work has four steps: a pre-processing of IVUS images, a segmentation of media–adventitia contour, a detection of intima and plaque and a 3D reconstruction of the vessel. Preprocessing is intended to remove …
A VR-based serious game for studying emotional regulation in adolescents
2015
[EN] We all use more or less adapted strategies to confront adverse emotional situations in our lives without being psychologically affected. Emotional Regulation (ER) strategies that we use determine the way in which we feel, express and behave. Moreover, ER strategies are particularly important in adolescents, a population in the age when the deficits of ER strategies can be linked to the appearance of numerous mental health disorders such as depression or anxiety, or disruptive behaviors. Thus, the early detection of dysfunctional ER strategies and the training in adaptive ER strategies will help us to prevent the future occurrence of possible behavioral and psychosocial disorders. In th…
A supervised learning framework of statistical shape and probability priors for automatic prostate segmentation in ultrasound images
2013
Prostate segmentation aids in prostate volume estimation, multi-modal image registration, and to create patient specific anatomical models for surgical planning and image guided biopsies. However, manual segmentation is time consuming and suffers from inter-and intra-observer variabilities. Low contrast images of trans rectal ultrasound and presence of imaging artifacts like speckle, micro-calcifications, and shadow regions hinder computer aided automatic or semi-automatic prostate segmentation. In this paper, we propose a prostate segmentation approach based on building multiple mean parametric models derived from principal component analysis of shape and posterior probabilities in a multi…
Factors influencing transfer accuracy of cone beam CT-derived template-based implant placement.
2011
Objectives The aim of the present investigation was the analysis of the factors presumptively affecting the accuracy outcome of cone-beam computed tomography (CBCT)-derived laboratory-based surgical guides for implant placement in partially edentulous patients. Materials and methods In 52 partially edentulous patients a total of 132 implants were placed following CBCT diagnostics with the aid of laboratory-fabricated, tooth-borne templates. Based on the image fusion technique measurements were done to calculate linear and angular deviations between virtually planned and placed implants. The implant sites were stratified according to four factors that presumably may influence the transfer ac…