Cooperative Wireless Systems

This Ph.D. dissertation reports on the work performed at the Wireless Communication Laboratory - University of Bologna and National Research Council - as well as, for six months, at the Fraunhofer Institute for Integrated Circuit (IIS) in Nürnberg. The work of this thesis is in the area of wireless communications, especially with regards to cooperative communications aspects in narrow-band and ultra-wideband systems, cooperative links characterization, network geometry, power allocation techniques,and synchronization between nodes. The underpinning of this work is devoted to developing a general framework for design and analysis of wireless cooperative communication systems, which depends on propagation environment, transmission technique, diversity method, power allocation for various scenarios and relay positions. The optimal power allocation for minimizing the bit error probability at the destination is derived. In addition, a syncronization algorithm for master-slave communications is proposed with the aim of jointly compensate the clock drift and offset of wireless nodes composing the network.

Proxy sip/rtp/rtcp a supporto della mobilita: Prestazioni.

Scenario VoIP, tecnologia PjSip e descrizione dell'implementazione di un Proxy Relay per la soluzione di alcune problematiche SIP

Risk analysis of tractor rollover in the normal operation in field

Tractor rollover represent a primary cause of death or serious injury in agriculture and despite the mandatory Roll-Over Protective Structures (ROPS), that reduced the number of injuries, tractor accidents are still of great concern. Because of their versatility and wide use many studies on safety are concerned with the stability of tractors, but they often prefer controlled tests or laboratory tests. The evaluation of tractors working in field, instead, is a very complex issue because the rollover could be influenced by the interaction among operator, tractor and environment. Recent studies are oriented towards the evaluation of the actual working conditions developing prototypes for driver assistance and data acquisition. Currently these devices are produced and sold by manufacturers. A warning device was assessed in this study with the aim to evaluate its performance and to collect data on different variables influencing the dynamics of tractors in field by monitoring continuously the working conditions of tractors operating at the experimental farm of the Bologna University. The device consists of accelerometers, gyroscope, GSM/GPRS, GPS for geo-referencing and a transceiver for the automatic recognition of tractor-connected equipment. A microprocessor processes data and provides information, through a dedicated algorithm requiring data on the geometry of the tested tractor, on the level of risk for the operator in terms of probable loss of stability and suggests corrective measures to reduce the potential instability of the tractor.

Hadronic correlation functions with quark-disconnected contributions in lattice QCD

One of the fundamental interactions in the Standard Model of particle physicsrnis the strong force, which can be formulated as a non-abelian gauge theoryrncalled Quantum Chromodynamics (QCD). rnIn the low-energy regime, where the QCD coupling becomes strong and quarksrnand gluons are confined to hadrons, a perturbativernexpansion in the coupling constant is not possible.rnHowever, the introduction of a four-dimensional Euclidean space-timernlattice allows for an textit{ab initio} treatment of QCD and provides arnpowerful tool to study the low-energy dynamics of hadrons.rnSome hadronic matrix elements of interest receive contributionsrnfrom diagrams including quark-disconnected loops, i.e. disconnected quarkrnlines from one lattice point back to the same point. The calculation of suchrnquark loops is computationally very demanding, because it requires knowledge ofrnthe all-to-all propagator. In this thesis we use stochastic sources and arnhopping parameter expansion to estimate such propagators.rnWe apply this technique to study two problems which relay crucially on therncalculation of quark-disconnected diagrams, namely the scalar form factor ofrnthe pion and the hadronic vacuum polarization contribution to the anomalousrnmagnet moment of the muon.rnThe scalar form factor of the pion describes the coupling of a charged pion torna scalar particle. We calculate the connected and the disconnected contributionrnto the scalar form factor for three different momentum transfers. The scalarrnradius of the pion is extracted from the momentum dependence of the form factor.rnThe use ofrnseveral different pion masses and lattice spacings allows for an extrapolationrnto the physical point. The chiral extrapolation is done using chiralrnperturbation theory ($chi$PT). We find that our pion mass dependence of thernscalar radius is consistent with $chi$PT at next-to-leading order.rnAdditionally, we are able to extract the low energy constant $ell_4$ from thernextrapolation, and ourrnresult is in agreement with results from other lattice determinations.rnFurthermore, our result for the scalar pion radius at the physical point isrnconsistent with a value that was extracted from $pipi$-scattering data. rnThe hadronic vacuum polarization (HVP) is the leading-order hadronicrncontribution to the anomalous magnetic moment $a_mu$ of the muon. The HVP canrnbe estimated from the correlation of two vector currents in the time-momentumrnrepresentation. We explicitly calculate the corresponding disconnectedrncontribution to the vector correlator. We find that the disconnectedrncontribution is consistent with zero within its statistical errors. This resultrncan be converted into an upper limit for the maximum contribution of therndisconnected diagram to $a_mu$ by using the expected time-dependence of therncorrelator and comparing it to the corresponding connected contribution. Wernfind the disconnected contribution to be smaller than $approx5%$ of thernconnected one. This value can be used as an estimate for a systematic errorrnthat arises from neglecting the disconnected contribution.rn

Studio di un algoritmo di controllo di temperatura per ganasce termosigillanti in macchine per packaging

Gli obiettivi dell'elaborato sono lo studio e la programmazione di un algoritmo di controllo di temperatura per le superfici termosaldanti di macchine per il packaging (confezionatrici in film a file multiple) prodotte dal committente, OMAG srl. L'algoritmo è implementato tramite il software SoMachineMotion v.4.2, prodotto da Schneider Electrics spa. Il controllo è di tipo in anello chiuso in retroazione, con temocoppie e resistenze di riscaldamento con modulazione PWM. Ci si è inizialmente occupati di testare su banco prova varie tipologie di regolatori: a relay, a isteresi, a ricerca diretta del duty cycle, TBH, con approccio misto TBH/integratore di Clegg, PID. I diversi metodi di regolazione sono stati valutati sulla base di una serie di metri di giudizio (precisione dell'inseguimento, prestazioni statiche e dinamiche, flessibilità, peso computazionale, facilità implementativa), pesati secondo i requisiti imposti dal committente. Le metodologie selezionate sono state PID e TBH/Clegg integrator; quest'ultima ha dato risultati assai soddisfacenti, pur essendo un metodo monoparametrico. Si sono quindi studiate diverse modalità per la taratura del regolatore PID, in particolare: tuning in anello chiuso con metodo a relay per la fase di pretuning, algoritmo di Nelder-Mead, per la ricerca diretta continua dei valori che minimizzano l'errore integrale, per un selftuning adattivo. Si è infine proceduto ad implementare le soluzioni individuate in un software robusto, che rispetti gli standard del settore e si sono inoltre sviluppate una serie di funzionalità aggiuntive, quali: modulazione software PWM, preriscaldamento, handling errori/warning, filtraggio segnali in/out. Si è addizionalmente sviluppato un modello matematico predittivo dell'evoluzione del sistema, che potrebbe servire, in un futuro sviluppo, come base per un controllo model-based in cascata al controllo in retroazione studiato.

UAVNet: A Mobile Wireless Mesh Network Using Unmanned Aerial Vehicles

We developed UAVNet, a framework for the autonomous deployment of a flying Wireless Mesh Network using small quadrocopter-based Unmanned Aerial Vehicles (UAVs). The flying wireless mesh nodes are automatically interconnected to each other and building an IEEE 802.11s wireless mesh network. The implemented UAVNet prototype is able to autonomously interconnect two end systems by setting up an airborne relay, consisting of one or several flying wireless mesh nodes. The developed software includes basic functionality to control the UAVs and to setup, deploy, manage, and monitor a wireless mesh network. Our evaluations have shown that UAVNet can significantly improve network performance.

Functional, structural and molecular plasticity of mammalian skeletal muscle in response to exercise stimuli

Biological systems have acquired effective adaptive strategies to cope with physiological challenges and to maximize biochemical processes under imposed constraints. Striated muscle tissue demonstrates a remarkable malleability and can adjust its metabolic and contractile makeup in response to alterations in functional demands. Activity-dependent muscle plasticity therefore represents a unique model to investigate the regulatory machinery underlying phenotypic adaptations in a fully differentiated tissue. Adjustments in form and function of mammalian muscle have so far been characterized at a descriptive level, and several major themes have evolved. These imply that mechanical, metabolic and neuronal perturbations in recruited muscle groups relay to the specific processes being activated by the complex physiological stimulus of exercise. The important relationship between the phenotypic stimuli and consequent muscular modifications is reflected by coordinated differences at the transcript level that match structural and functional adjustments in the new training steady state. Permanent alterations of gene expression thus represent a major strategy for the integration of phenotypic stimuli into remodeling of muscle makeup. A unifying theory on the molecular mechanism that connects the single exercise stimulus to the multi-faceted adjustments made after the repeated impact of the muscular stress remains elusive. Recently, master switches have been recognized that sense and transduce the individual physical and chemical perturbations induced by physiological challenges via signaling cascades to downstream gene expression events. Molecular observations on signaling systems also extend the long-known evidence for desensitization of the muscle response to endurance exercise after the repeated impact of the stimulus that occurs with training. Integrative approaches involving the manipulation of single factors and the systematic monitoring of downstream effects at multiple levels would appear to be the ultimate method for pinpointing the mechanism of muscle remodeling. The identification of the basic relationships underlying the malleability of muscle tissue is likely to be of relevance for our understanding of compensatory processes in other tissues, species and organisms.

Brain areas involved in medial temporal lobe seizures: a principal component analysis of ictal SPECT data

The study describes brain areas involved in medial temporal lobe (mTL) seizures of 12 patients. All patients showed so-called oro-alimentary behavior within the first 20 s of clinical seizure manifestation characteristic of mTL seizures. Single photon emission computed tomography (SPECT) images of regional cerebral blood flow (rCBF) were acquired from the patients in ictal and interictal phases and from normal volunteers. Image analysis employed categorical comparisons with statistical parametric mapping and principal component analysis (PCA) to assess functional connectivity. PCA supplemented the findings of the categorical analysis by decomposing the covariance matrix containing images of patients and healthy subjects into distinct component images of independent variance, including areas not identified by the categorical analysis. Two principal components (PCs) discriminated the subject groups: patients with right or left mTL seizures and normal volunteers, indicating distinct neuronal networks implicated by the seizure. Both PCs were correlated with seizure duration, one positively and the other negatively, confirming their physiological significance. The independence of the two PCs yielded a clear clustering of subject groups. The local pattern within the temporal lobe describes critical relay nodes which are the counterpart of oro-alimentary behavior: (1) right mesial temporal zone and ipsilateral anterior insula in right mTL seizures, and (2) temporal poles on both sides that are densely interconnected by the anterior commissure. Regions remote from the temporal lobe may be related to seizure propagation and include positively and negatively loaded areas. These patterns, the covarying areas of the temporal pole and occipito-basal visual association cortices, for example, are related to known anatomic paths.

Cell-type specific alterations of cortical interneurons in schizophrenic patients

In the human brain, cortical GABAergic interneurons represent an important population of local circuit neurons responsible for the intrinsic modulation of neuronal information and have been supposed to be involved in the pathophysiology of schizophrenia. We conducted a quantitative study on the differentiated three-dimensional morphological structure of two types of parvalbumin-immunoreactive interneurons in the anterior cingulate cortex (ACC) of schizophrenic patients versus controls. While type A interneurons ('small bipolar cells') showed a significant reduction of their soma size in schizophrenics, type B interneurons ('small multipolar cells') of schizophrenic patients exhibited a marked decrease in the extent of their dendritic system. These results further support the assumption of a considerable significance of the ACC, an important limbic relay centre, for the etiopathogenesis of schizophrenic psychoses.

Arc-flash analysis of utility power systems

The electric utility business is an inherently dangerous area to work in with employees exposed to many potential hazards daily. One such hazard is an arc flash. An arc flash is a rapid release of energy, referred to as incident energy, caused by an electric arc. Due to the random nature and occurrence of an arc flash, one can only prepare and minimize the extent of harm to themself, other employees and damage to equipment due to such a violent event. Effective January 1, 2009 the National Electric Safety Code (NESC) requires that an arc-flash assessment be performed by companies whose employees work on or near energized equipment to determine the potential exposure to an electric arc. To comply with the NESC requirement, Minnesota Power’s (MP’s) current short circuit and relay coordination software package, ASPEN OneLinerTM and one of the first software packages to implement an arc-flash module, is used to conduct an arc-flash hazard analysis. At the same time, the package is benchmarked against equations provided in the IEEE Std. 1584-2002 and ultimately used to determine the incident energy levels on the MP transmission system. This report goes into the depth of the history of arc-flash hazards, analysis methods, both software and empirical derived equations, issues of concern with calculation methods and the work conducted at MP. This work also produced two offline software products to conduct and verify an offline arc-flash hazard analysis.

Development and simulation of DSP filters for transformer differential protection / by Oskar Reynisson.

Transformer protection is one of the most challenging applications within the power system protective relay field. Transformers with a capacity rating exceeding 10 MVA are usually protected using differential current relays. Transformers are an aging and vulnerable bottleneck in the present power grid; therefore, quick fault detection and corresponding transformer de-energization is the key element in minimizing transformer damage. Present differential current relays are based on digital signal processing (DSP). They combine DSP phasor estimation and protective-logic-based decision making. The limitations of existing DSP-based differential current relays must be identified to determine the best protection options for sensitive and quick fault detection. The development, implementation, and evaluation of a DSP differential current relay is detailed. The overall goal is to make fault detection faster without compromising secure and safe transformer operation. A detailed background on the DSP differential current relay is provided. Then different DSP phasor estimation filters are implemented and evaluated based on their ability to extract desired frequency components from the measured current signal quickly and accurately. The main focus of the phasor estimation evaluation is to identify the difference between using non-recursive and recursive filtering methods. Then the protective logic of the DSP differential current relay is implemented and required settings made in accordance with transformer application. Finally, the DSP differential current relay will be evaluated using available transformer models within the ATP simulation environment. Recursive filtering methods were found to have significant advantage over non-recursive filtering methods when evaluated individually and when applied in the DSP differential relay. Recursive filtering methods can be up to 50% faster than non-recursive methods, but can cause false trip due to overshoot if the only objective is speed. The relay sensitivity is however independent of filtering method and depends on the settings of the relay’s differential characteristics (pickup threshold and percent slope).

Pupil phase apodization for achromatic imaging of extra-solar planets

Direct imaging of extra-solar planets in the visible and infrared region has generated great interest among scientists and the general public as well. However, this is a challenging problem. Diffculties of detecting a planet (faint source) are caused, mostly, by two factors: sidelobes caused by starlight diffraction from the edge of the pupil and the randomly scattered starlight caused by the phase errors from the imperfections in the optical system. While the latter diffculty can be corrected by high density active deformable mirrors with advanced phase sensing and control technology, the optimized strategy for suppressing the diffraction sidelobes is still an open question. In this thesis, I present a new approach to the sidelobe reduction problem: pupil phase apodization. It is based on a discovery that an anti-symmetric spatial phase modulation pattern imposed over a pupil or a relay plane causes diffracted starlight suppression sufficient for imaging of extra-solar planets. Numerical simulations with specific square pupil (side D) phase functions, such as ... demonstrate annulling in at least one quadrant of the diffraction plane to the contrast level of better than 10^12 with an inner working angle down to 3.5L/D (with a = 3 and e = 10^3). Furthermore, our computer experiments show that phase apodization remains effective throughout a broad spectrum (60% of the central wavelength) covering the entire visible light range. In addition to the specific phase functions that can yield deep sidelobe reduction on one quadrant, we also found that a modified Gerchberg-Saxton algorithm can help to find small sized (101 x 101 element) discrete phase functions if regional sidelobe reduction is desired. Our simulation shows that a 101x101 segmented but gapless active mirror can also generate a dark region with Inner Working Distance about 2.8L/D in one quadrant. Phase-only modulation has the additional appeal of potential implementation via active segmented or deformable mirrors, thereby combining compensation of random phase aberrations and diffraction halo removal in a single optical element.

Transformer modeling ATP : internal faults & high-frequency discretization

Power transformers are key components of the power grid and are also one of the most subjected to a variety of power system transients. The failure of a large transformer can cause severe monetary losses to a utility, thus adequate protection schemes are of great importance to avoid transformer damage and maximize the continuity of service. Computer modeling can be used as an efficient tool to improve the reliability of a transformer protective relay application. Unfortunately, transformer models presently available in commercial software lack completeness in the representation of several aspects such as internal winding faults, which is a common cause of transformer failure. It is also important to adequately represent the transformer at frequencies higher than the power frequency for a more accurate simulation of switching transients since these are a well known cause for the unwanted tripping of protective relays. This work develops new capabilities for the Hybrid Transformer Model (XFMR) implemented in ATPDraw to allow the representation of internal winding faults and slow-front transients up to 10 kHz. The new model can be developed using any of two sources of information: 1) test report data and 2) design data. When only test-report data is available, a higher-order leakage inductance matrix is created from standard measurements. If design information is available, a Finite Element Model is created to calculate the leakage parameters for the higher-order model. An analytical model is also implemented as an alternative to FEM modeling. Measurements on 15-kVA 240?/208Y V and 500-kVA 11430Y/235Y V distribution transformers were performed to validate the model. A transformer model that is valid for simulations for frequencies above the power frequency was developed after continuing the division of windings into multiple sections and including a higher-order capacitance matrix. Frequency-scan laboratory measurements were used to benchmark the simulations. Finally, a stability analysis of the higher-order model was made by analyzing the trapezoidal rule for numerical integration as used in ATP. Numerical damping was also added to suppress oscillations locally when discontinuities occurred in the solution. A maximum error magnitude of 7.84% was encountered in the simulated currents for different turn-to-ground and turn-to-turn faults. The FEM approach provided the most accurate means to determine the leakage parameters for the ATP model. The higher-order model was found to reproduce the short-circuit impedance acceptably up to about 10 kHz and the behavior at the first anti-resonant frequency was better matched with the measurements.

Simulating in vivo-like Synaptic Input Patterns in Multicompartmental Models

In the laboratory of Dr. Dieter Jaeger at Emory University, we use computer simulations to study how the biophysical properties of neurons—including their three-dimensional structure, passive membrane resistance and capacitance, and active membrane conductances generated by ion channels—affect the way that the neurons transfer synaptic inputs into the action potential streams that represent their output. Because our ultimate goal is to understand how neurons process and relay information in a living animal, we try to make our computer simulations as realistic as possible. As such, the computer models reflect the detailed morphology and all of the ion channels known to exist in the particular neuron types being simulated, and the model neurons are tested with synaptic input patterns that are intended to approximate the inputs that real neurons receive in vivo. The purpose of this workshop tutorial was to explain what we mean by ‘in vivo-like’ synaptic input patterns, and how we introduce these input patterns into our computer simulations using the freely available GENESIS software package (http://www.genesis-sim.org/GENESIS). The presentation was divided into four sections: first, an explanation of what we are talking about when we refer to in vivo-like synaptic input patterns

Reduced olfactory bulb volume in adults with a history of childhood maltreatment

The human olfactory bulb (OB) is the first relay station of the olfactory pathway and may have the potential for postnatal neurogenesis in early childhood. In animals, chronic stress affects the OB and olfactory functioning. For humans, it has been shown that major depressive disorder is accompanied by reduced OB volume and reduced olfactory function. However, it is not clear if major stress in childhood development also affects olfactory functioning and OB volume in humans. OB volume was measured and olfactory function was tested in 17 depressive patients with and 10 without a history of severe childhood maltreatment (CM). CM patients exhibited a significantly reduced olfactory threshold and identification ability. The OB volume of the CM patients was significantly reduced to 80% of the non-CM patients. In conclusion, postnatal neurogenesis might be by reduced in CM, which may affect olfactory function of the brain in later life. Alternatively, a reduced OB volume may enhance psychological vulnerability in the presence of adverse childhood conditions although other areas not analyzed in this study may also be involved.