324,233 research outputs found
Automatic balancing parameter selection for Tikhonov-TV regularization
No full textThis paper considers large-scale linear ill-posed inverse problems whose solutions can be represented as sums of smooth and piecewise constant components. To solve such problems we consider regularizers consisting of two terms that must be balanced. Namely, a Tikhonov term guarantees the smoothness of the smooth solution component, while a total-variation (TV) regularizer promotes blockiness of the non-smooth solution component. A scalar parameter allows to balance between these two terms and, hence, to appropriately separate and regularize the smooth and non-smooth components of the solution. This paper proposes an efficient algorithm to solve this regularization problem by the alternating direction method of multipliers (ADMM). Furthermore, a novel algorithm for automatic choice of the balancing parameter is introduced, using robust statistics. The proposed approach is supported by some theoretical analysis, and numerical experiments concerned with different inverse problems are presented to validate the choice of the balancing parameter
Robust estimation of structural orientation parameters and 2D/3D local anisotropic Tikhonov regularization
No full textUnderstanding the orientation of geologic structures is crucial for analyzing the complexity of the earths' subsurface. For instance, information about geologic structure orientation can be incorporated into local anisotropic regularization methods as a valuable tool to stabilize the solution of inverse problems and produce geologically plausible solutions. We introduce a new variational method that uses the alternating direction method of multipliers within an alternating minimization scheme to jointly estimate orientation and model parameters in 2D and 3D inverse problems. Specifically, our approach adaptively integrates recovered information about structural orientation, enhancing the effectiveness of anisotropic Tikhonov regularization in recovering geophysical parameters. The paper also discusses the automatic tuning of algorithmic parameters to maximize the new method's performance. Our algorithmis tested across diverse 2D and 3D examples, including structure-oriented denoising and trace interpolation. The results indicate that the algorithm is robust in solving the considered large and challenging problems, alongside efficiently estimating the associated tilt field in 2D cases and the dip, strike, and tilt fields in 3D cases. Synthetic and field examples show that our anisotropic regularization method produces a model with enhanced resolution and provides a more accurate representation of the true structures
Review article di: S. Gholami, "Selected Features of Bactrian Grammar", Wiesbaden: Harrassowitz, 2014
No full textIl lavoro consiste in un review article di un volume di Gholami che concerne alcuni aspetti caratterizzanti della morfologia del battrian
Physicochemical and antigenic properties correlation in Streptococcus gordonii vaccine vectors and development of a Streptococcus pneumoniae intra-tracheal mouse model of pneumonia
No full textIn the present thesis, the correlation between the physicochemical and antigenic properties of different recombinant Streptococcus gordonii vaccine vectors was studied. Evaluation of vaccine efficacy, antigenicity and immugenicity is a crucial step in developing vaccines, thus investigating a simple method to analyze vaccine efficacy besides other methods could be a major part of developing bacterial vaccine vectors. To approach this, isoelectric point measurements and zeta-potential titration as well as antigenicity and immunogenicity of S.gordonii vaccine vectors (with fbpA, RPS, gtfg genes mutations expressing H1 antigen) were used. These data showed that strains with more positive surface charge had higher heterologous antigen recognition and lower antibody responses in the serum of immunized mice. This correlation between surface charge and antigenicity and immunogenicity revealed the importance of using simple methods such as zeta potential titration and isoelectric point measurements to predict engineered vaccine vectors antigenicity and possible efficacy. In the second part of the thesis the immune recall in the days following Streptococcus pneumoniae lung infection by transcriptomic analysis was studied. S. pneumoniae is the most common bacterial cause of community-acquired pneumonia. Host-pathogen interaction is poorly understood, and factors that drive a more severe phenotype are unknown. One way to study host response to pathogen is using the stimulation of immune system cells with live or killed bacteria. We combined transcriptomic and cytokine level analysis on stimulated mouse splenocytes revealing the presence of a recall immune response involving both innate and adaptive immunity, stronger from the fourth day after infection. This model could analyze immune responses involved in pneumococcal infection as well as vaccine and experimental therapies efficacy in future studies. Finally, the development of a S. pneumoniae mouse model of pneumonia by intra-tracheal infection was set up. The nasopharynx of humans is the only natural reservoir for the pneumococci. To mimic human pneumonia, mice models are widely used. Bacteria can be administered to mice intranasally, intratracheally or as aerosols. Pneumococcal pneumonia was induced in mice by intra-tracheal inoculation with different doses of S. pneumoniae TIGR4. Data showed high colonization of bacteria in lung, liver and spleen starting 24 hours post-infection. Pneumonia mortalities were observed in all mice infected by 108 within 24 hours of infection. Further analysis should be done to investigate the host-pathogen interaction as well as vaccine and experimental therapies efficacy by using this model
A Scalable Framework for Multi-Robot Tele-Impedance Control
No full textIn this article, we present an online scalable tele-impedance framework, which enables the individual and collaborative control of multiple different robotic platforms. The framework provides an intuitive low-cost interface with visual feedback and a SpaceMouse, through which the operator can define the desired task-level trajectories and impedance profiles. With a simple mouse click, the user can switch between the robots and the collaborative operation mode. The control, subsequently, manages the distribution of the required parameters into the involved robots. Thanks to the introduced virtual hand concept, where each robot is defined as a finger, new robots can be easily added or removed via their kinodynamic parameters. The proposed framework was evaluated with three different experiments: a simulated auscultation on a mock-up patient, a cooperative task where a robot drives the patient on a wheelchair and a different robot performs the auscultation, and a collaborative task where two robots relocate a container. The results demonstrate the capabilities of the framework in terms of adaptability to different robotic platforms, the number of robots involved, and the task requirements. Additionally, quantitative and subjective analysis of 12 subjects showed how the developed interface, even in the presence of inaccurate visual feedback, allowed a smooth and accurate execution of the tasks
Shelf life extension of white mushrooms (Agaricus bisporus) by low temperatures conditioning, modified atmosphere, and nanocomposite packaging material
No full textIn this work, we have explored a new integrated approach for the shelf life extension of button mushrooms (Agaricus bisporus). The effect of temperature (4 °C and 25 °C), packaging configuration (PET/coating/LLDPE oxygen barrier material over conventional PVC stretchable film), and modified atmosphere (15% O2/5% CO2/80% N2 over air) were monitored during 10 days of storage. The influence of a chitosan coating deposited on the cap surface was also investigated. Temperature was the most important factor in preserving the quality attributes of mushrooms over time. The test material had a positive impact on weight loss, cap opening percentage, and firmness of mushrooms compared with the control film (∼1.0% versus ∼7.1%; ∼55% versus ∼65%; and ∼10.3 N versus ∼7.6 N, respectively), which was ascribed to the excellent and good oxygen and water vapor barrier properties of the new material, respectively. Mushrooms packaged under the modified atmosphere behaved decidedly better after a prolonged storage time of 22 days at 4 °C. Impressively, after this extended temporal window, the mushrooms looked freshly packed by fully recovering their original color. We explained this striking observation in consideration of the oxygen that permeated the package during these additional 12 days of storage, which would have promoted a gradual resumption of respiratory activity in the overall metabolism of the mushrooms after the “freezing” effect of the rich-CO2 atmosphere inside the package
Impact Planning and Pre-configuration based on Hierarchical Quadratic Programming
No full textImpacts and other non-smooth behaviors are usually unwanted in robotic applications. However, several industrial tasks such as deburring, removing excess material, and assembling/fitting, involve impacts between objects, which can benefit from robotic automation due to the risks posed to human health. Towards this objective, in this paper, we propose a method for optimal impact planning and pre-configuration for torque-controlled robots. We thus employ a well-known impulsive contact model to plan the impact force and create a hierarchical quadratic programming based controller capable of minimizing the robot's peak torques by reconfiguring its joints optimally, before the impact occurs. The results obtained from multiple experiments during an industrial deburring task are discussed. Using a 7-DoF manipulator, we show consistent results, both in terms of accuracy of the impact force tracking with respect to the desired forces, and in terms of peak torques reduction and uniform torques distribution
A Reconfigurable Interface for Ergonomic and Dynamic Tele-Locomanipulation
No full textProlonged remote tele-locomanipulation of multi degrees-of-freedom mobile manipulators requires a compromise between the system's performance and the operator's ergonomics. Neglecting this demand can significantly affect either the task completion or the level of comfort to achieve it. However, the simultaneous consideration of these key factors has received less attention in the literature. To respond to this demand, in this work, we introduce a new teleoperation setup, which integrates the features of an ergonomic and a highly maneuverable interface into a unified solution. The ergonomic part of the interface implements a 3D mouse-like functionality, enabling the execution of long navigation tasks for the floating base. The highly manoeuvrable interface instead, enables the operator to perform dynamic or more precise manipulation by moving his/her arm in space. The locomotion and manipulation modes of the follower robot are controlled separately, which can be easily and seamlessly switched by the operator by pressing a button at any moment. Furthermore, due to the follower manipulator's redundancy, this robot is controlled by a hierarchical quadratic programming technique which enables the definition of a set of secondary tasks to be executed in the robot's nullspace. Finally, to demonstrate the advantages and disadvantages of the proposed user interfaces, five participants are asked to perform two different experiments: (i) target selection task on a moving surface and (ii) remote path tracking on a fixed surface. The quantitative and qualitative analyses show the effectiveness of the proposed interface during the teleoperation tasks, especially when it comes to the precise and dynamic task execution
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Distributed Finite-Time Secondary Control of Islanded Microgrids by Coupled Sliding-Mode Technique
No full textThis paper deals with the problem of voltage and frequency restoration in droop-controlled inverter-based islanded microgrids (MGs). The problem is solved using a novel tracking consensus secondary control protocol based on the sliding-mode approach, which not only guarantees the exact finite-time restoration among voltages and frequencies of an inverter-based islanded microgrid, but also preserves the active power sharing among distributed generations (DGs). For each distributed generator with no direct access to reference values, a finite-time distributed estimator is locally designed and implemented in each DG unit to provide the reference value of frequency and voltage in a finite time. Lyapunov analysis is employed to verify the associated stability and fast convergence time of the proposed controller. Finally, simulation results are are presented and analyzed to confirm the effectiveness of the proposed approach
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