Modelling and Design of Advanced Reliable Circuits and Devices for Energy Efficiency

Reliable electronic systems, namely a set of reliable electronic devices connected to each other and working correctly together for the same functionality, represent an essential ingredient for the large-scale commercial implementation of any technological advancement. Microelectronics technologies and new powerful integrated circuits provide noticeable improvements in performance and cost-effectiveness, and allow introducing electronic systems in increasingly diversified contexts. On the other hand, opening of new fields of application leads to new, unexplored reliability issues. The development of semiconductor device and electrical models (such as the well known SPICE models) able to describe the electrical behavior of devices and circuits, is a useful means to simulate and analyze the functionality of new electronic architectures and new technologies. Moreover, it represents an effective way to point out the reliability issues due to the employment of advanced electronic systems in new application contexts. In this thesis modeling and design of both advanced reliable circuits for general-purpose applications and devices for energy efficiency are considered. More in details, the following activities have been carried out: first, reliability issues in terms of security of standard communication protocols in wireless sensor networks are discussed. A new communication protocol is introduced, allows increasing the network security. Second, a novel scheme for the on-die measurement of either clock jitter or process parameter variations is proposed. The developed scheme can be used for an evaluation of both jitter and process parameter variations at low costs. Then, reliability issues in the field of “energy scavenging systems” have been analyzed. An accurate analysis and modeling of the effects of faults affecting circuit for energy harvesting from mechanical vibrations is performed. Finally, the problem of modeling the electrical and thermal behavior of photovoltaic (PV) cells under hot-spot condition is addressed with the development of an electrical and thermal model.

Integrated analysis and design of optimization and up-scaling of inductively coupled plasma synthesis of nanoparticles

This study is focused on radio-frequency inductively coupled thermal plasma (ICP) synthesis of nanoparticles, combining experimental and modelling approaches towards process optimization and industrial scale-up, in the framework of the FP7-NMP SIMBA European project (Scaling-up of ICP technology for continuous production of Metallic nanopowders for Battery Applications). First the state of the art of nanoparticle production through conventional and plasma routes is summarized, then results for the characterization of the plasma source and on the investigation of the nanoparticle synthesis phenomenon, aiming at highlighting fundamental process parameters while adopting a design oriented modelling approach, are presented. In particular, an energy balance of the torch and of the reaction chamber, employing a calorimetric method, is presented, while results for three- and two-dimensional modelling of an ICP system are compared with calorimetric and enthalpy probe measurements to validate the temperature field predicted by the model and used to characterize the ICP system under powder-free conditions. Moreover, results from the modeling of critical phases of ICP synthesis process, such as precursor evaporation, vapour conversion in nanoparticles and nanoparticle growth, are presented, with the aim of providing useful insights both for the design and optimization of the process and on the underlying physical phenomena. Indeed, precursor evaporation, one of the phases holding the highest impact on industrial feasibility of the process, is discussed; by employing models to describe particle trajectories and thermal histories, adapted from the ones originally developed for other plasma technologies or applications, such as DC non-transferred arc torches and powder spherodization, the evaporation of micro-sized Si solid precursor in a laboratory scale ICP system is investigated. Finally, a discussion on the role of thermo-fluid dynamic fields on nano-particle formation is presented, as well as a study on the effect of the reaction chamber geometry on produced nanoparticle characteristics and process yield.

Non-Linear Analysis and Design of Synchronous Bearingless Multiphase Permanent Magnet Machines and Drives

A two-dimensional model to analyze the distribution of magnetic fields in the airgap of a PM electrical machines is studied. A numerical algorithm for non-linear magnetic analysis of multiphase surface-mounted PM machines with semi-closed slots is developed, based on the equivalent magnetic circuit method. By using a modular structure geometry, whose the basic element can be duplicated, it allows to design whatever typology of windings distribution. In comparison to a FEA, permits a reduction in computing time and to directly changing the values of the parameters in a user interface, without re-designing the model. Output torque and radial forces acting on the moving part of the machine can be calculated. In addition, an analytical model for radial forces calculation in multiphase bearingless Surface-Mounted Permanent Magnet Synchronous Motors (SPMSM) is presented. It allows to predict amplitude and direction of the force, depending on the values of torque current, of levitation current and of rotor position. It is based on the space vectors method, letting the analysis of the machine also during transients. The calculations are conducted by developing the analytical functions in Fourier series, taking all the possible interactions between stator and rotor mmf harmonic components into account and allowing to analyze the effects of electrical and geometrical quantities of the machine, being parametrized. The model is implemented in the design of a control system for bearingless machines, as an accurate electromagnetic model integrated in a three-dimensional mechanical model, where one end of the motor shaft is constrained to simulate the presence of a mechanical bearing, while the other is free, only supported by the radial forces developed in the interactions between magnetic fields, to realize a bearingless system with three degrees of freedom. The complete model represents the design of the experimental system to be realized in the laboratory.

Analysis and design of high performance multiphase electric drives for vehicle and aircraft applications

The first part of this thesis has focused on the construction of a twelve-phase asynchronous machine for More Electric Aircraft (MEA) applications. In fact, the aerospace world has found in electrification the way to improve the efficiency, reliability and maintainability of an aircraft. This idea leads to the aircraft a new management and distribution of electrical services. In this way is possible to remove or to reduce the hydraulic, mechanical and pneumatic systems inside the aircraft. The second part of this dissertation is dedicated on the enhancement of the control range of matrix converters (MCs) operating with non-unity input power factor and, at the same time, on the reduction of the switching power losses. The analysis leads to the determination in closed form of a modulation strategy that features a control range, in terms of output voltage and input power factor, that is greater than that of the traditional strategies under the same operating conditions, and a reduction in the switching power losses.

Dynamic computer simulations of electrophoresis: a versatile research and teaching tool

Software is available, which simulates all basic electrophoretic systems, including moving boundary electrophoresis, zone electrophoresis, ITP, IEF and EKC, and their combinations under almost exactly the same conditions used in the laboratory. These dynamic models are based upon equations derived from the transport concepts such as electromigration, diffusion, electroosmosis and imposed hydrodynamic buffer flow that are applied to user-specified initial distributions of analytes and electrolytes. They are able to predict the evolution of electrolyte systems together with associated properties such as pH and conductivity profiles and are as such the most versatile tool to explore the fundamentals of electrokinetic separations and analyses. In addition to revealing the detailed mechanisms of fundamental phenomena that occur in electrophoretic separations, dynamic simulations are useful for educational purposes. This review includes a list of current high-resolution simulators, information on how a simulation is performed, simulation examples for zone electrophoresis, ITP, IEF and EKC and a comprehensive discussion of the applications and achievements.

Response of interleukin-6 during euglycaemic and hyperglycaemic exercise in patients with type 1 diabetes mellitus

The aim of this randomized, single-blinded cross-over study was to investigate the response of interleukin-6 (IL-6) during moderate aerobic exercise in stable euglycaemia and hyperglycaemia in seven male patients with type 1 diabetes mellitus. IL-6 increased significantly over the entire study period in euglycaemia, but not in hyperglycaemia.

Nanomechanics to drive stem cells in injured tissues: insights from current research and future perspectives

Stem cells reside within tissue, ensuring its natural ability to repair an injury. They are involved in the natural repair of damaged tissue, which encompasses a complex process requiring the modulation of cell survival, extracellular matrix turnover, angiogenesis, and reverse remodeling. To date, the real reparative potential of each tissue is underestimated and noncommittal. The assessment of the biophysical properties of the extracellular environment is an innovative approach to better understand mechanisms underlying stem cell function, and consequently to develop safe and effective therapeutic strategies replacing the loss of tissue. Recent studies have focused on the role played by biomechanical signals that drive stem cell death, differentiation, and paracrinicity in a genetic and/or an epigenetic manner. Mechanical stimuli acting on the shape can influence the biochemistry and gene expression of resident stem cells and, therefore, the magnitude of biological responses that promote the healing of injured tissue. Nanotechnologies have proven to be a revolutionary tool capable of dissecting the cellular mechanosensing apparatus, allowing the intercellular cross-talk to be decoded and enabling the reparative potential of tissue to be enhanced without manipulation of stem cells. This review highlights the most relevant findings of stem cell mechanobiology and presents a fascinating perspective in regenerative medicine.

Posttraumatic stress disorder and dyslipidemia: previous research and novel findings from patients with PTSD caused by myocardial infarction

Based on a brief systematic review suggesting dyslipidemia in posttraumatic stress disorder (PTSD), we studied, for the first time, levels of blood lipids in patients with a DSM-IV diagnosis of PTSD caused by myocardial infarction (MI).

Preventing vasospasm improves outcome after aneurysmal subarachnoid hemorrhage: rationale and design of CONSCIOUS-2 and CONSCIOUS-3 trials

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH) is a frequent but unpredictable complication associated with poor outcome. Current vasospasm therapies are suboptimal; new therapies are needed. Clazosentan, an endothelin receptor antagonist, has shown promise in phase 2 studies, and two randomized, double-blind, placebo-controlled phase 3 trials (CONSCIOUS-2 and CONSCIOUS-3) are underway to further investigate its impact on vasospasm-related outcome after aSAH. Here, we describe the design of these studies, which was challenging with respect to defining endpoints and standardizing endpoint interpretation and patient care. Main inclusion criteria are: age 18-75 years; SAH due to ruptured saccular aneurysm secured by surgical clipping (CONSCIOUS-2) or endovascular coiling (CONSCIOUS-3); substantial subarachnoid clot; and World Federation of Neurosurgical Societies grades I-IV prior to aneurysm-securing procedure. In CONSCIOUS-2, patients are randomized 2:1 to clazosentan (5 mg/h) or placebo. In CONSCIOUS-3, patients are randomized 1:1:1 to clazosentan 5, 15 mg/h, or placebo. Treatment is initiated within 56 h of aSAH and continued until 14 days after aSAH. Primary endpoint is a composite of mortality and vasospasm-related morbidity within 6 weeks of aSAH (all-cause mortality, vasospasm-related new cerebral infarction, vasospasm-related delayed ischemic neurological deficit, neurological signs or symptoms in the presence of angiographic vasospasm leading to rescue therapy initiation). Main secondary endpoint is extended Glasgow Outcome Scale at week 12. A critical events committee assesses all data centrally to ensure consistency in interpretation, and patient management guidelines are used to standardize care. Results are expected at the end of 2010 and 2011 for CONSCIOUS-2 and CONSCIOUS-3, respectively.

Randomized clinical trial comparing percutaneous closure of patent foramen ovale (PFO) using the Amplatzer PFO Occluder with medical treatment in patients with cryptogenic embolism (PC-Trial): rationale and design

Background Several studies have shown an association of cryptogenic stroke and embolism with patent foramen ovale (PFO), but the question how to prevent further events in such patients is unresolved. Options include antithrombotic treatment with warfarin or antiplatelet agents or surgical or endovascular closure of the PFO. The PC-Trial was set up to compare endovascular closure and best medical treatment for prevention of recurrent events. Methods The PC-Trial is a randomized clinical trial comparing the efficacy of percutaneous closure of the PFO using the Amplatzer PFO occluder with best medical treatment in patients with cryptogenic embolism, i.e. mostly cryptogenic stroke. Warfarin for 6 months followed by antiplatelet agents is recommended as medical treatment. Randomization is stratified according to patients age (<45 versus ≥45 years), presence of atrial septal aneurysm (ASA yes or no) and number of embolic events before randomization (one versus more than one event). Primary endpoints are death, nonfatal stroke and peripheral embolism. Discussion patients were randomized in 29 centers of Europe, Canada, and Australia. Randomization started February 2000. Enrollment of 414 patients was completed in February 2009. All patients will be followed-up longitudinally. Follow-up is maintained until the last enrolled patient is beyond 2.5 years of follow-up (expected in 2011).

Tooth wear and erosion: methodological issues in epidemiological and public health research and the future research agenda

This paper addresses methodological issues in the field of tooth wear and erosion research including the epidemiological indices, and identifies future work that is needed to improve knowledge about tooth wear and erosion.