Dissertations / Theses on the topic 'Timing'

Thesis (MMed)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: Background - Preeclampsia is a multi-system disease characterized by hypertension and proteinuria in pregnant women at greater than 20 weeks of gestational age. It remains one of the leading causes of maternal and foetal mortality and morbidity. While the cause of preeclampsia is essentially unknown, the important theories strongly implicate disturbed placental function in early pregnancy. Additionally, some researchers have investigated the possibility of a seasonal relationship with the incidence of preeclampsia. Differences in incidences of preeclampsia, examined exclusively on the basis of delivery timing, have also been noted to have seasonal variation, but results have been inconsistent. Objective - Our primary objective was to investigate the seasonal variation in preeclampsia in relation to the timing of conception and the timing of presentation with clinical disease over the period of one year. Methods - We performed a retrospective descriptive study of all women with preeclampsia who delivered at Tygerberg Hospital in 2010. Preeclampsia was diagnosed as hypertension associated with proteinuria after the 20th week of gestation. Names of patients were identified from labour ward records and data was collected and recorded on a data-sheet. Data were primarily analysed in relation to the season of delivery and also the season of the last menstruation. Summer was diagnosed as lasting from summer solstice to autumn equinox, autumn as lasting from autumn equinox until winter solstice, winter as lasting from winter solstice until spring equinox and spring as lasting from spring equinox until summer solstice. The data was analysed using the SPSS software (Statistical Package for Social Science). Discrete data was compared by calculating relative risks with 95% confidence limits, as well as the chi2 test. Fisher‘s exact test was used to compare ratios where the expected value in any cell of a two-by-two table is less than five. The means of normally distributed continuous data was compared by analysis of variance, while the medians of continuous data which are not distributed normally, where calculated using the non-parametric Mann Whitney u test. A p-value of < 0.05 was considered to be statistically significant, where applicable. Results - The peak incidence of preeclampsia was during winter with 32.2% of all cases occurring during this season. This was significantly higher than during the summer when only 169 (17.17%) cases of preeclampsia were delivered. When we analysed the data looking at the timing of menstruation (and therefore conception), we found that 292 (29.7%) patients that developed preeclampsia had their last menstrual period in the spring, with November the month of peak incidence. The lowest incidence was found in winter, with only 218 (22.2%) patients. Conclusion - We have confirmed a previous finding of a seasonal variation in the occurence of preeclampsia in Tygerberg Hospital. We have also confirmed that this seasonal variation is not only influenced by the timing of delivery, but also by the timing of conception.<br>AFRIKAANSE OPSOMMING: Agtergrond - Preeklampsie is ‘n multi-sisteem siekte wat gekenmerk word deur hipertensie en proteinurie. Dit word slegs gedurende swangerskap aangetref - gewoonlik na 20 weke. Dit is steeds een van die voorste oorsake van moederlike en fetale morbiditeit en mortaliteit. Terwyl die oorsaak van preeklampsie steeds onbekend is, dui die belangrikste teorië op versteurde plasentale ontwikkeling en funksionering vroeg in swangerskap. Sekere navorsers het ook die moontlikheid van ‘n seisonale patroon in die voorkoms van preeklampsie ondersoek. ‘n Seisonale patroon is wel identifiseer, maar dit is slegs gebasseer op die datum van verlossing en die resultate tussen studies wissel. Doel - Ons primêre doel was om die seisonale patroon in die insidensie van preeklampsie te ondersoek oor ‘n tydperk van een jaar en dan die datum van bevrugting te vergelyk met die datum van diagnose en verlossing. Metodiek - Ons het ‘n retrospektiewe beskrywende studie gedoen oor al die pasiënte met preeklampsie wat tydens 2010 by Tygerberg Hospitaal verlos is. Preeklampsie is gediagnoseer as hipertensie met geassosieerde proteinurie met aankoms na 20 weke. Die name van die pasiënte is verkry uit die kraamsaal-registers en data is versamel en op ‘n datastel aangebring. Data is primer geanaliseer in terme van die seisoen van verlossing en die seisoen waartydens die laaste maandstonde plaasgevind het. Die seisoene is as volg geklassifiseer : somer vanaf die summer solstice to autumn equinox, autumn as lasting from autumn equinox until winter solstice, winter as lasting from winter solstice until spring equinox and spring as lasting from spring equinox until summer solstice. Die data is geanaliseer met die SPSS sagteware (Statistical Package for Social Science). Diskrete data is vergelyk deur die relatiewe risiko’s te bereken met vertrouensintervalle van 95%, sowel as die chi2 toets. Fisher se eksakte toets is gebruik om ratios te vergelyk waar die verwagte waarde van enige sel in ‘n 2-by-2 tabel minder as 5 is. Die gemiddeldes van normaal-verspreide aaneenlopende data is vergelyk deur die analise van variance. Die mediane van aaneenlopende data wat nie normaal versprei was nie, is bereken met die non-parametriese Mann-Whitney-U-toets. ‘n P-warde van <0,05 is beskou as statisties betekenisvol, waar van toepassing. Resultate - Die piek –insidensie van preeklampsie was gedurende die wintermaande, met 32.2% van alle gevalle. Dit was betekenisvol hoër as die gedurende die somer, waar slegs 169 (17.17%) van gevalle verlos is. Toe ons die data analiseer na gelang van die datum van laaste menstruasie (en gevolglik bevrugting), het ons gevind dat 292 (29.7%) van die pasiënte wat preeklampsie ontwikkel het, het hul laaste maandstonde gedurende die lente ervaar. Die piek-insidensie was gedurende November. Daarteenoor is die laagste insidensie gevind in pasiënte met ‘n laaste menstruasie in die winter, met slegs 218 (22.2%) pasiënte. Gevolgtrekking - Ons het die vorige bevinding by Tygerberg Hospitaal van ‘n seisonale patroon in die ontwikkeling van preeklampsie bevestig. Ons het ook bevestig dat dit nie die datum van diagnose en verlossing is wat’n rol speel nie, maar wel die datum van laaste maandstonde en bevrugting.

The present thesis employed psychophysical choice procedures to examine the role of the cerebellum in interval timing in Wistar rats within the context of W. H. Meck and R. M. Church's (1983) mode control model of timing and counting. Three competing hypotheses were examined: That the cerebellum functions as 1) an independent milliseconds timer; 2) part of an extended timing system where it contributes to scalar variance; and 3) part of an extended timing system where it contributes to constant rather than scalar variance. Counting was also evaluated as a way to examine a specific source of constant variance in timing. A review of the mode control model and sources of variance in counting and timing, together with consideration of the generalised Weber function, concluded that a single set of processes could accommodate performance across the milliseconds and seconds range timing as well as counting. Lesions to the cerebellar hemispheres but not the cerebellar vermis produced some deficits in a millisecond discrimination task (200 to 800 ms) but discriminations in the seconds range (2 to 8 s) were unaffected by either type of lesion. In contrast, comparative lesions to nucleus accumbens produced deficits in both time ranges. Cerebellar hemisphere lesions but not vermal lesions also produced deficits in numerical discrimination. These findings suggest that damage to the cerebellar hemispheres influences a source of constant variability, because constant variability is a prominent source of error during millisecond timing but is masked by other sources of variability when tinting longer durations (> 2 s). The deficits in numerical discrimination suggest that switch processes, a specific source of constant variance described by the mode control model, are disrupted by damage to the cerebellar hemispheres. Prior to the lesion work, an extensive examination was also made of timing and numerical performance to establish that intact rats could discriminate the numerosity of trial unique signals which obviate concerns about non-numerical confounds. This work provided an unequivocal demonstration that rats can count sequential events, but they do so according to H. Davis and J. Memmott's (1983) "last resort" hypothesis.

Mestrado em Finanças<br>O objetivo desta dissertação é examinar o impacto das eleições políticas na atividade empresarial. Para isso, coletamos dados de 16 países por um número variado de anos (dentro de uma faixa de 16 a 21 anos por país) para construir uma amostra de 3.056 observações. Os nossos dados vêm do Global Entrepreneurship Monitor Adult Population Survey e do Nordsieck, W. (1997) Parties and Elections in Europe, obtido em http://www.parties-and-elections.eu. Em seguida, estimamos um pooled Ordinary Least Squares (OLS) e um modelo de efeito fixo para ver como o momento das eleições afeta os níveis empresariais no país. Além disso, examinamos os efeitos de uma vitória inesperada. Os resultados obtidos sugerem que a Atividade Empreendedora Total aumenta durante um ano eleitoral e diminui no ano anterior, enquanto não há evidência estatística de qualquer efeito no ano seguinte.<br>Purpose of this dissertation is to examine the impact of political elections on entrepreneurial activity. In order to do so, we collect data from 17 countries for a varied number of years (within a range of 16 to 21 years per country) to build a sample of 3,056 observations. Our data comes from the Global Entrepreneurship Monitor Adult Population Survey and from Nordsieck, W. (1997) Parties and Elections in Europe retrieved from http://www.parties-and-elections.eu . We then estimate a pooled Ordinary Least Squares (OLS) and a fixed effect model to see how the elections timing affect entrepreneurial levels in the country. In addition, we examine the effects of an unexpected victory, Results obtained suggest that Total Entrepreneurial Activity increases during an election year and decreases the year before, while there is no statistical evidence of any effect in the year after.<br>info:eu-repo/semantics/publishedVersion

<p>Power control is one of the technologies used to utilize the radio resources as efficient as possible in WCDMA. The transmission power is adjusted to transmit with the lowest power level possible while the required received signal quality is maintained. Since there are large variation in channel quality over time, the power has to be adjusted to compensate for these variations. During moments of bad channel conditions a high transmission power has to be used which will to a greater extent interfere with other users in the system. </p><p>To solve this problem a concept called transmission timing was proposed. The basic idea is that the transmitter avoids data transmission during the short periods of bad channel conditions caused by fast fading. Higher bit rates can be used to compensate for this when the channel conditions are good. </p><p>In this thesis the performance of transmission timing applied to uplink data transmissions is evaluated. This is accomplished through a theoretical analysis as well as simulations of a cellular system using transmission timing. Lowered transmission power is achieved and thus lowered interference is induced. Simulations showed that the transmission power can be lowered by up to 1.6 dB compared to ordinary continuous transmission with equal average data rate. These results are however strongly dependent on the used radio environment. It is also showed that transmission timing provides increased system stability in case of rapid changes in the load situation.</p>

Rapid development processes and higher customer requirements lead to increasing integration of software solutions in the automotive industry’s products. Today, several electronic control units communicate by bus systems like CAN and provide computation of complex algorithms. This increasingly requires a controlled timing behavior. The following diploma thesis investigates how the timing analysis tool SymTA/S can be used in the software development process of the ZF Friedrichshafen AG.Within the scope of several scenarios, the benefits of using it, the difficulties in using it and the questions that can not be answered by the timing analysis tool are examined. (new: additional files)

Many of the tasks we complete every day require us to attend to the passing of time or to use time information in some way. Everyday tasks frequently require us to use time information in a strategic, deliberate, and explicit way, such as when we wish to steep a cup of tea for 3 minutes or must leave to meet a colleague in 5 minutes. Much of the previous research on timing has used very short duration tasks, in the range of seconds. Several models have been developed to account for timing in short duration tasks, but it is not known which model(s) best fit timing of everyday intervals. This dissertation research was designed to determine whether the AGM or memory storage models can account for timing in the range of everyday intervals. Experiment 1 investigated the underlying pattern of estimates in the range of 1-5 minutes. Participants produced underestimates for all intervals. Experiments 2 and 3 used a framing manipulation to investigate the role of memory chunking in timing everyday durations. Participants who were instructed to focus on the present task produced intervals that were longer than participants who were instructed to focus on a future task, consistent with the idea that a present frame serves as a better organizing structure for the interval and results in fewer chunks. According to memory storage models, the number of items in memory is compared to a stored value in reference memory to determine how much time has passed. When stimuli are organized more cohesively, resulting in fewer chunks, it takes a longer time to accumulate the target number of chunks. Experiment 4 used feedback and an attentional manipulation to investigate the role of reference memory and attention to timing. Participants produced more accurate intervals following feedback, consistent with the idea that reference memory for everyday intervals is inaccurate. Attention had no effect on estimate duration, which is inconsistent with the AGM. Taken together, the results from these experiments suggest that memory storage models are a better fit for timing in the range of everyday intervals.<br>Arts, Faculty of<br>Psychology, Department of<br>Graduate

In this thesis an investigation will be done on how time and frequency can be synchronized over Ethernet with help of Precision Time Protocol and Synchronous Ethernet. The goal is to achieve a high accuracy in the synchronization when a topology of 10 cascaded nodes is used. Different approaches may be used when implementing Precision Time Protocol for synchronization. They will be investigated and the best approach for a good accuracy will be proposed. Another question that this thesis will cover is how to recover a radio frequency, a multiple of 3.84 MHz from Ethernets 10.3125 GHz. By using hardware support for the timestamps and transparent clocks in the forwarding nodes the best accuracy is achieved for the time and phase synchronization. Combining this with Synchronous Ethernet for frequency synchronization, to get a traceable clock through the system, will lead to the best result. The total error does not need to be greater than 1.46~ns if the asymmetry in the medium is neglected and a welldesigned PCS and FIFO are used. Recovering the radio frequency from Ethernet is done by using the highest common frequency, either an integer phase locked loop or a fractional phase locked loop can be used. The fractional phase locked loop will give a better result but will contribute with spurs that the integer phase locked loop does not.

This thesis describes a model of speech timing, predicting at the syllable level, with sensitivity to rhythmic factors at the foot level, that predicts segmental durations by a process of accommodation into the higher-level timing framework. The model is based on analyses of two large databases of British English speech; one illustrating the range of prosodic variation in the language, the other illustrating segmental duration characteristics in various phonetic environments. Designed for a speech synthesis application, the model also has relevance to linguistic and phonetic theory, and shows that phonological specification of prosodic variation is independent of the phonetic realisation of segmental duration. It also shows, using normalisation of phone-specific timing characteristics, that lengthening of segments within the syllable is of three kinds: prominence-related, applying more to onset segments; boundary-related, applying more to coda segments; and rhythm/rate-related, being more uniform across all component segments. In this model, durations are first predicted at the level of the syllable from consideration of the number of component segments, the nature of the rhyme, and the three types of lengthening. The segmental durations are then constrained to sum to this value by determining an appropriate uniform quantile of their individual distributions. Segmental distributions define the range of likely durations each might show under a given set of conditions; their parameters are predicted from broad-class features of place and manner of articulation, factored for position in the syllable, clustering, stress, and finality. Two parameters determine the segmental duration . pdfs, assuming a Gamma distribution, and one parameter determines the quantile within that pdf to predict the duration of any segment in a given prosodic context. In experimental tests, each level produced durations that closely fitted the data of four speakers of British English, and showed performance rates higher than a comparable model predicting exclusively at the level of the segment.

"Timing diagrams are used in industrial practice as a specification language of circuit components. They have been formalized for efficient use in model checking. This formalization is often more succinct and convenient than the use of temporal logic. We explore the relationship between timing diagrams and temporal logic formulas by showing that closure under disjunction does not hold for timing diagrams. We give an algorithm that returns a disjunction (if any) of two given timing diagrams. We also give algorithms that decide satisfiability of a timing diagram and return exact time separations between events in a timing diagram. An Alloy specification for timing diagrams with one waveform has also been built."

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 88-100).<br>Timing is a key component in hippocampal encoding of space. I will discuss three lines of work related to this theme. First, I will describe the fine-timescale characteristics of single neurons in hippocampal subregion CAl, where theta oscillations organize groups of neurons into orderly sequences. While theta was once thought to be synchronized throughout CAl, it was recently shown instead to be offset in time along the long axis of the hippocampus. Considering distant pairs of neurons, our fundamental sequence spiking property may instead be systematically staggered by these offsets in the rhythms that pace them. I tested the impact of theta wave time offsets by recording place cell spike sequences from groups of neurons in distant parts of CAl, and found that place cell sequences more closely coordinate with each other than the underlying theta oscillations do. In regions that differ from one another by 13 milliseconds of theta delay, place cell sequences are typically aligned to within 5 milliseconds. This raises the possibility that theta wave offsets serve another purpose, perhaps timing the communication with brain areas connected to different parts of CAl, while compensatory mechanisms are in place to preserve the fine temporal alignment of place cell spatial information. Second, I will describe a tool for closed-loop experiments using information decoded from hippocampal ensembles. Place cell activity is typically extracted and analyzed only after an experiment has ended. But interrogating the timing of hippocampal information, enhancing or interfering with it, requires decoding that information immediately. I will discuss some of the difficulties and the eventual implementation of a system capable of sequence time-scale position decoding and then survey the future experimental applications.<br>by Gregory Hale.<br>Ph. D.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada<br>Shaped offset quadrature phase shift keying (SOQPSK) is a highly bandwidth efficient modulation technique used widely in military and aeronautical telemetry standards. It can be classified as a form of continuous phase modulation (CPM), but its major distinction from other CPM schemes is that it has a constrained (correlated) ternary data alphabet. CPM-based detection models for SOQPSK have been developed only recently. One roadblock standing in the way of these detectors being adopted is that existing symbol timing recovery techniques for CPM are not always applicable since the data symbols are correlated. We investigate the performance of one CPM-based timing error detector (TED) that can be used with SOQPSK, and apply it to the versions of SOQPSK used in military (MIL-STD SOQPSK) and telemetry group (SOQPSK-TG) standards. We derive the theoretical performance limits on the accuracy of timing recovery for SOQPSK, as given by the modified Cramer-Rao bound (MCRB), and show that the proposed TED performs close to these bounds in computer simulations and is free of false-lock points. We also show that the proposed scheme outperforms a non-data aided TED that was recently developed for SOQPSK. These results show that the proposed scheme has great promise in a wide range of applications due to its low complexity, strong performance, and lack of false-lock points.

International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada<br>The Western Space and Missile Center (WSMC) plans to precisely synchronize remote instrumentation site timing on the Western Test Range (WTR) using Global Positioning System (GPS) equipment being developed for Tri-Service range applications. This paper describes background information, current WTR timing capability, remote site synchronization requirements, a proposed GPS timing system configuration, and testing approach.

Iterative decoders such as Low-Density Parity-Check (LDPC) and turbo decoders have an inherent capability to correct the transmission errors that originate during communication over a hostile wireless channel. This capability has engendered the widespread use of LDPC and turbo decoders in current communications standards. As a result, signficant research efforts have been made in order to conceive efficient Very-Large-Scale Integration (VLSI) implementations of both LDPC and turbo decoders. Typically, these efforts have focused on optimizing only one of the various trade-offs associated with the hardware implementation of iterative decoders, such as the chip area, latency, throughput, energy efficiency or Bit Error Ratio (BER) performance. However, tolerance to timing errors that occur during the iterative decoding processing are typically not considered in these implementations. Owing to this, the BER performance and hardware efficiency of the proposed designs may be severely degraded, if timing errors occur during the iterative decoding process. Against this background, this thesis demonstrates that iterative decoders are capable of exploiting their inherent error correction capability to correct not only transmission errors, but also timing errors caused by overclocking and power supply variations. Moreover,we propose modifications to the iterative decoders designs, which further enhance their inherent tolerance to timing errors. We achieve this by considering the close relationship between the different trade-offs associated with the hardware implementation of iterative decoders, with the aim of achieving Pareto optimality, where none of these trade-offs can be further improved without degrading at least one of the others. Owing to this, our proposed timing-error-tolerant design methodology simultaneously considers the design constraints and parameters that affect not only the BER performance, but also the hardware efficiency of each implementation. We first investigate the benefits of stochastic computing in iterative decoders, by characterizing the inherent timing-error tolerance of Stochastic LDPC Decoders (SLDPCDs) and Stochastic Turbo Decoders (STDs). Moreover, we propose modifications to the SLDPCD and STD in order to further improve their inherent tolerance to timing errors. This is achieved by performing extensive transistor-level and post-layout simulations, in order to develop different timing analyses for determining the causes and effects of timing errors in these stochastic decoders. Following this, we propose a novel Reduced-Latency STD (RLSTD), which improves the latency of the state-of-the-art STD by an order of magnitude, without increasing its chip area or energy consumption. Our experimental results demonstrate that our proposed RLSTD achieves ultra-low-latencies required by next-generation Mission-Critical Machine-Type Communication (MCMTC). We also investigate the inherent tolerance to timing errors of a recently-proposed Fully-Parallel Turbo Decoder (FPTD). Furthermore, we propose a novel Reduced-Critical-Path Fully-Parallel Turbo Decoder (RCP-FPTD) algorithm and the employment of Better-Than-Worst-Case (BTWC) design techniques in FPTD and RCP-FPTD implementations, for the sake of improving their throughput and their tolerance to timing errors caused by overclocking. We demonstrate that the FPTD and RCP-FPTD implementations improve the throughput of the state-of-the-art turbo decoder by an order of magnitude. Finally, despite operating in the presence of timing errors, our proposed Better-Than-Worst-Case Reduced-Critical-Path Fully-Parallel Turbo Decoder (BTWC-RCP-FPTD) achieves throughputs on the order of tens of Gbps, which may be expected to be a requirement in next-generation wireless communication standards.

The question of how actions involving the interception of moving objects are perceptually timed is addressed. This question has been intimately bound up with a debate which sets the 'ecological' approach to perception and action (due to Gibson) in opposition to approaches which employ computational concepts. It is argued that modern versions of the two types of approach are not, in fact, opposed but are largely complementary and frequently equivalent. A general approach for tackling problems of peceptuo-motor control in humans and animals which integrates the two approaches is outlined. The problem of how interceptions of moving objects are perceptually controlled is investigated according to this general approach. First, the informational requirements of interceptive actions are analyzed. It is concluded that 'time-to-contact' information is critical for accurate timing. The hypothesis, due to Lee, that animals and people assume the relative velocity between target and interception point to be constant when computing time-to-contact is discussed. A scheme for the continuous control of interceptive timing based on this strategy is formulated. Having established how time-to-contact information might be used to control interceptive timing the question of the perceptual source of this informtion is examined. A mathematical analysis of the visual stimulus is provided which clarifies and extends Lee's theory concerning the visual source of time-to-contact information.

I mitt arbete undersöker jag vikten av timing i det vi gör som musiker när vi spelar. Genom min analys av Douze Études 1, med både egen övning och digitala verktyg, har jag kommit fram till hur timing kan skapa olika sound. Mitt arbete kommer täcka olika metoder av övning med digitala verktyg. Första delen av arbetet är en formanalys av etyden, då jag kommer gå igenom olika delar i stycket för att få en grundläggande översikt. Därefter går jag igenom min övningsprocess där jag detaljerat beskriver de problem som jag har stött på. Avslutningsvis dedicerar jag ett kapitel om övning med digitala verktyg där jag även kommer att ta upp logistiken och mentaliteten bakom övningen.<br><p>Inspelning av Delécluse Étude 1 skedde separat och därav kommer som en separat inspelning.</p><p>Examenskonserten ägde rum på Kungliga Musikhögskolan, Svarta Lådan den 26e maj 2017.</p><p>Program:</p><p>Twine - Rolf Wallin, för marimba och xylofon</p><p>Rollercoaster - Daniel Berg, Yaroslav Polikarpov, för vibrafon och marimba (uruppförande)</p><p>Blues for Gilbert - Mark Glentworth, solo stycke för vibrafon</p><p>Dancing Stars - George Hamilton Green (arr. av Jerker Johansson), för solo xylofon tillsammans med två marimbor.</p><p></p><p>Medverkande:</p><p>Aleksander Ullriksen, Maarja Nuut, Daniel Berg, Rikard Markstedt, Kristoffer Linder</p>

Kerb (Pronamide) is often ineffective when it is leached below germinating weed seeds with sprinkler irrigation. Efficacy can be improved by making delayed aerial applications after the sprinklers have been started and before weeds have become established. Tests were conducted to determine the optimal time of application. Optimal times varied with the season and ranged from two to three days after the sprinklers had started during the early season (Sept.) to five to six days during the late season (January).

The detailed knowledge of the temporal behaviour of astrophysical objects is one of the main sources of information about physical processes occurring in several classes of objects. In this PhD thesis we investigated two different astrophysical topics, both of them linked to timing. We present the scientific analysis of the data collected from the Crab pulsar by means of the novel optical extremely fast-photon counters Aqueye and Iqueye, that have the best temporal resolution ever achieved in the optical domain (hundreds of picoseconds). Aqueye (Barbieri et al. 2008, 2009) was designed to be mounted at the Copernico telescope in Asiago. Iqueye (Naletto et al. 2009, 2010) is an improvedversion for the NTT telescope. Here we also discuss some ideas on modelling the millisecond variability observed in the X-ray flux from Low Mass X-ray Binaries with either a neutron star or a black hole. The timing analysis of the optical emission from the Crab pulsar requires to time-tag with extreme precision the photons as collected by an inertial observer. Therefore we must refer the time of arrival of photons (TOAs) to a reference frame that approximates an inertial frame to the level of precision needed. One usually refers TOAs to a reference system located at the solar system barycenter. Tempo2 (Hobbs et al. 2006, Edwards et al. 2006) is a software meant to model with extreme precision (up to 1 ns) TOAs as collected by an inertial observer. After baricentering TOAs a numerical code making use of a standard template was used to determine the phase of the mean peak of the Crab pulsar profile. By studying the phase behaviour it is possible to extract information about both the rotational period of the fast rotating neutron star and its derivatives. Moreover, the analysis of the phase-residuals left out after subtracting the standard pulsar timing model may reveal interesting features of the pulsar and its surroundings. With the anlysis of the residuals one can also check for possible discrepancies on the modelling. If some systematic residuals show up, then it is interesting to investigate the physical origin. Just to quote a few noticeable examples, we mention the discovery of the first extrasolar planetary system around the pulsar PSR B1257+12, obtained from the analysis of pulsar phase-residuals (Wolszczan & Frail 1992; Wolszczan 1994; Konacki & Wolszczan 2003). Other foundamental results deal with tests of General Relativity theory (Helfand et al. 1980; Kramer et al. 2006). Moreover, pulsar timing is now being planned as a tool to reveal gravitational wave (Stappers et al. 2006; Manchester 2010). The analysis of the optical phase-residuals of the Crab pulsar we performed has revealed poor corrections in the Roemer delay due to the Tempo2 configuration files. After correcting for them we can conclude that the rotational periods of the Crab pulsar measured by Aqueye/Iqueye agree with those quoted in the Jodrell Bank radio archive up to a few picoseconds. The TOAs from a photon-counter usually are affected by noise that obeys the Poisson statistics. We noticed possible discrepancies between the radio and optical rotational periods larger than the estimated Poissonian error, but a more extensive analysis of the pulsar timing noise and related errors is needed before any definitive conclusion can be drawn. We were able to measure the spin down of the neutron star already over a baseline of a few days. Discrepancies with that reported in the Jodrell Bank radio archive are underlined. By comparing the time of arrival of the optical peak at the solar system barycenter with that quoted in the Jodrell Bank radio ephemerides archive we find a radio-optical delay in agreement with that reported in the literature (Shearer et al. 2003; Oosterbroek et al. 2008), that is, an optical peak leading the radio one by about 120 microsec. We also noticed same radio-optical phase drift with time, which may be related to the radio-optical rotational period discrepancies mentioned above. A further investigation on the possible origin of these discrepancies led to the preliminary conclusion that the signal from the Crab pulsar may be affected by an extra-noise component, known as timing noise, not suitable described by the Poissonian statistics. Non-Poissonian noise in the signal from neutron stars has been reported by other authors (Boynton et al. 1972; Lyne et al. 1993; Scott et al. 2003; Hobbs et al. 2006b; Patruno et al. 2009), but using integration times of months or years. Further observations to confirm the existence of non-Poissonian noise in the Crab pulsar are needed. In this PhD thesis we also present some ideas on the origin of the millisecond X-ray timing variability in the X-ray flux from Low Mass X-ray Binaries (LMXBs), with either a black hole or a neutron star (e.g. van der Klis et al. 2004). These quasi-periodic oscillations (QPOs), at frequencies up to 1200 Hz, were discovered by means of the X-ray photon-counters on board of the Rossi X-ray Timing Explorer satellite (RXTE; Bradt et al. 1993). Millisecond time-scales are typical for matter orbiting close to the compact object. Therefore, timing studies of these sources could provide a way to investigate the motion of matter in a strongly curved space-time, thus probing General Relativity in the strong field limit. We describe some ideas on fitting relativistic frequencies in the Kerr metric to observed QPO frequencies in LMXBs. Using a grid of masses and specific angular momenta for the neutron star we show that numerical fits have a low χ2/dof for masses of the neutron star above 2 M⊙. Such masses are bigger than the canonical value 1.4M⊙ measured in double radio pulsars. However, in accreting bynary systems a mass of the neutron star larger than the canonical value has been measured (Casares et al. 2006, 2010). We note that precise measurements of neutron star masses by means of millisecond QPOs are uncertain because of the yet poorly understood phenomenology. If high frequency QPOs in the X-ray flux of LMXBs are produced by orbiting blobs of matter close to the compact object then a full-consistent modelling should also account for the interaction of the shape of the blob with the curved geometry of the space-time. In collaboration with the Department of Mathematics and Physics of the University of Ljubljana we ran simulations of light curves and power spectra produced by clumps of free particles orbiting a Schwarzschild black hole, that are deformed by tidal interaction. The numerical code was developed by (Cadez et al. 2008, Kostic et al. 2009). The numerical simulations reproduce the high frequency part of the power spectrum observed in the black hole LMXB XTE J1550-564 (Germanà et al. 2009).<br>Le proprietà della variabilità temporale nelle sorgenti astrofisiche sono di notevole interesse e riguardano una vasta gamma di fenomeni che si sviluppano in diversi tipi di oggetti. In questa tesi di dottorato abbiamo investigato due classi di fenomei astrofisici, entrambi legati a studi sulla varabilità temporale. La tesi presenta l'analisi scientifica dei dati raccolti dalla Crab pulsar con gli innovativi contatori di fotoni ottici Aqueye e Iqueye, la cui risoluzione temporale è la più alta mai raggiunta nel dominio ottico (centinaia di picosecondi). Aqueye (Barbieri et al. 2008, 2009) è stato progettato per essere montato al telescopio Copernico in Asiago. Iqueye (Naletto et al. 2009, 2010) è una versione innovativa e progettato per il telescopio NTT in La Silla. Altre investigazioni qui descritte riguardano lo sviluppo e la verifica di idee per interpretare e modellizzare la variabilità temporale al millisecondo osservata in sistemi binari X. Per quanto riguarda l'analisi scientifica dei dati dalla Crab pulsar, essa richiede che ai fotoni raccolti venga associato, con alta precisione, il rispettivo tempo di arrivo secondo un osservatore inerziale. Quindi dobbiamo riferire il tempo di arrivo dei fotoni (TOAs) ad un sistema di riferimento che approssimi al meglio uno inerziale. Solitamente i TOAs all'osservatorio vengono trasformati in TOAs misurati da un osservatore al baricentro del sistema solare. Tempo2 (Hobbs et al. 2006, Edwards et al. 2006) è un software sviluppato per modelizzare con estrema precisione (1 ns) i TOAs misurati in un sistema di riferimento inerziale. Dopo aver baricentrizzato i TOAs, abbiamo usato un codice numerico per calcolare la fase della Crab pulsar. Dallo studio dell'andamento della fase nel tempo è possibile misurare il periodo di rotazione della stella di neutroni e sue derivate. L'analisi dei residui in fase rispetto al modello standard può rivelare peculiarità della sorgente e dell'ambiente circostante. Con questo tipo di analisi e' possibile anche verificare la bontà del modello che corregge i tempi di arrivo al baricentro del sistema solare. Se c'è qualche discrepanza inaspettata allora è interessante investigare sulla sua origine fisica. Un risultato importante ottenuto dall'analisi dei residui in fase è stata la scoperta del primo sistema planetario extrasolare attorno alla pulsar PSR B1257+12 ( Wolszczan & Frail 1992; Wolszczan 1994; Konacki & Wolszczan 2003). Altri studi riguardano verifiche della teoria della Relatività Generale (Helfand et al. 1980; Kramer et al. 2006). Inoltre, il timing delle pulsars è stato proposto come potenziale strumento per la rivelazione di onde gravitazionali (Stappers et al. 2006; Manchester 2010). Dall'analisi dei residui in fase sono state notate inaccuratezze nel ricostruire i TOAs al baricentro del sistema solare, dovute a problemi con i files di configurazione del software Tempo2. Una volta risolti questi problemi, possiamo concludere che i periodi di rotazione della Crab pulsar misurati con Aqueye/Iqueye sono in accordo entro qualche picosecondo con quelli riportati nell'archivio radio del Jodrell Bank Observatory. I TOAs dei fotoni generano una componente di rumore che segue la statistica di Poisson. Le differenze tra i periodi radio e ottici sono maggiori dell'errore Poissoniano stimato. Con i dati raccolti da Aqueye/Iqueye e' stato possibile misurare la derivata prima del periodo di rotazione gia' con osservazioni su una base temporale di soli 2 giorni. Anche in questo caso abbiamo notato discrepanze maggiori dell'errore statistico. Misurando il tempo di arrivo del picco ottico al baricentro del sistema solare e confrontandolo con quello riportato nell'archivio radio, è stato ricavato il ritardo temporale del picco radio rispetto a quello ottico. Il picco ottico arriva circa 120 microsec in anticipo rispetto a quello radio, in accordo con altri osservatori (Shearer et al. 2003; Oosterbroek et al. 2008) . L'analisi ha anche rivelato un deriva della fase ottica rispetto a quella radio che sembra essere legata alle discrepanze gia' menzionate tra i periodi di rotazione. Ulteriori investigazioni hanno portato alla preliminare conclusione che il segnale ottico dalla Crab pulsar potrebbe essere influenzato da una componente di rumore che non segue la statistica di Poisson, conosciuto come timing noise. Rumore non Poissoniano nel segnale da stelle di neutroni è stato rivelato da diversi autori (Boynton et al. 1972; Lyne et al. 1993; Scott et al. 2003; Hobbs et al. 2006b; Patruno et al. 2009), comunque su basi temporali di mesi o anni. Ulteriori osservazioni sono necessarie per verificare la presenza di rumore non Poissoniano su scale di giorni. In questa tesi di dottorato è stata anche esplorata qualche idea sulla interpretazione e modelizzazione della variabilità temporale al millisecondo, osservata nel flusso X delle Low Mass X-ray Binaries (LMXBs; van der Klis 2004). Queste oscillazioni quasi-periodiche (QPOs), a frequenze fino a 1200 Hz, sono state rivelate con i contatori di fotoni X a bordo del satellite Rossi X-ray Timing Explorer (RXTE; Bradt et al. 1993) Oscillazioni al millisecondo sono tipiche del tempo scala orbitale a distanze prossime all'oggetto compatto. Lo studio temporale di queste sorgenti potrebbe essere un modo indiretto per studiare il moto della materia in uno spazio-tempo fortemente curvato, quindi per verificare la teoria della Relatività Generale in regime di campo forte. La tesi descrive qualche idea per interpolare le frequenze dei moti relativistici, calcolate per orbite nella metrica di Kerr, con i QPOs osservati nelle LMXBs. Abbiamo calcolato il chi-quadro ridotto (χ2/dof) su una griglia di masse e momenti angolari e notato che il minimo χ2/dof si ottiene per masse della stella di neutroni maggiori di 2 M⊙. Questi valori sono grandi rispetto alla usuale massa di una stella di neutroni (1.4M⊙) ottenuta dalle pulsar binarie. Comunque, in sistemi binari in accrescimento come le LMXBs, è stata misurata una massa della stella di neutroni maggiore di quella tipica (Casares et al. 2006, 2010). Va precisato che, utilizzare i QPOs al millisecondo per ottenere stime precise della massa di una stella di neutroni potrebbe non essere ancora un metodo sicuro, vista la complessità della fenomenologia e le tuttora poco chiare proprietà. Se i QPOs ad alta frequenza nel flusso X delle LMXBs sono prodotti da corpi che orbitano in prossimità dell'oggetto compatto, allora un modello consistente dovrebbe prendere in cosiderazione anche l'evoluzione della loro forma in uno spazio-tempo curvo. In collaborazione con il Dipartimento di Fisica e di Matematica dell'Università di Ljubljana abbiamo simulato curve di luce e spettri di potenza prodotti da un oggetto costituito da particelle libere orbitanti un buco nero di Schwarschild. Durante il moto orbitale la forma dell'oggetto è fortemente alterata dall'intensa forza mareale del buco nero (Cadez et al. 2008, Kostic et al. 2009). Tali simulazioni numeriche sono in grado di riprodurre lo spettro di potenza osservato nella LMXB con un buco nero XTE J1550-564 (Germanà et al. 2009).

Organisms in temperate zones time reproduction to occur when conditions are optimal for raising offspring. However, individuals of many taxa vary in precise timing of breeding. The mechanisms underlying the existing variation are not well understood, particularly in females. I hypothesized that individual variation in daily (i.e., circadian) rhythms, which are highly conserved across taxa, are related to variation in reproductive timing. By measuring activity onset in two species of songbirds, we found that females beginning their day earlier also breed earlier. I further asked if sex-steroid hormones were related to onset of daily activity in free-living individuals. My results show that maximal levels of estradiol are correlated with onset of activity in free-living females. This suggests that circadian rhythms may influence much of the variation seen in timing of breeding and individual physiology influences circadian behavior. In addition to mechanisms underlying reproductive timing, I also investigated potential selective pressures that could act on timing decisions. Early breeding females often produce more and larger offspring, however, most of the population breeds later than this optimum, suggesting there are costs associated with early reproduction. To determine if early breeding females are better able to handle an additional energetic challenge, I injected incubating females with a mild antigen and monitored nest survival in early and late breeders. The immune challenge caused a significant increase in nest failure compared to controls and success did not differ between early and late breeders. Next, using a long-term dataset I asked whether females who breed early experience accelerated rates of aging via telomere loss. I found that early breeding females experience higher telomere attrition compared to females breeding later. Annual change in telomere length was not related to reproductive output, but females experiencing cooler temperatures during egg laying and incubation (i.e., laying earlier in the season) had higher telomere attrition. With telomere loss and length being important determinants of lifespan and longevity, higher telomere attrition in early breeders may be linked with reduced overwinter survival. A better understanding of mechanisms and costs will help determine how populations will adjust to, or suffer from, a changing climate.<br>NSF; ND EPSCoR; Sigma Xi; Mountain Lake Biological Station; Department of Biological Sciences; Environmental and Conservation Sciences Program; American Ornithologists Union; Wilson Ornithological Society

Timing can be defined as the ability to perceive temporal sequences and regulate timed behaviors. As in other animals, our ability to make accurate time estimations is crucial in order to accomplish several activities. Organisms can process time over a wide range of durations ranging from microseconds to days. In the middle of these extremes is the hundreds of milliseconds to seconds range which is important for many everyday behaviors, such as walking, speaking and dancing. Yet, how this is managed remains poorly understood. Some central issues with regard time processing in this particular time range are whether timing is governed by one, or by several different mechanisms, possibly invoked by different effectors used to perform the timing task, as well as, if cognitive capacities are also involved in rhythmic motor timing. This thesis includes three studies. Study I investigated the effects of short- term practice on a motor timing task. Analyses of the timing variability indicated that a substantial amount of learning occurred in the first hour of practice and declined afterwards, exhibiting no trend for further decrease across the remaining 60 or 210 minutes. This effect was similar across effector, amount of feedback, and interval duration. Our results suggested that training effects influenced mainly motor precision and raised the question of whether motor timing training influenced also cognitive capacities. Study II investigated the relationship between motor timing and cognition. Specifically, participants had to train a sensorimotor synchronization task (SMS) over several days, and the question was whether this training would improve cognitive performance. A near transfer effect was found between the sensorimotor synchronization task and the sustained attention task, indicating that sustained attention is involved in motor timing. Study III compared the timing variability between the eyes and the hands, as a function of four different intervals, in order to examine whether these systems are temporally controlled by the same or different mechanism(s). The results showed several positive correlations in variability, between the eye and the finger movements, which, however, were significant only for the longer intervals. In addition, they were differences in variability between the eye and the hand, for the different interval durations. In general, the pattern of results from these studies suggested that voluntary motor timing is managed by overlapping distributed mechanisms and that these mechanisms are related to systems that manage cognitive processes, such as attention. The results partially explain the well-known relationships between cognitive ability and timing.

<p>XMM-Newton is a X-ray telescope launched december 1999, by the European Space Agency, ESA. On board XMM-Newton are two EPIC-MOS X-ray detectors. The detectors are build by Charged Coupled Devices (CCDs), of Metal Oxide Semi-conductor type. The EPIC-MOS cameras have four science operating modes. This project aims to evaluate the calibration for one of these four modes, the timing mode.</p><p>The evaluation is divided into two parts. The first part is the evaluation of the flux calibration, performed by analysing various observation made in timing mode. The second part is the evaluation of timing properties by performing timing analysis of XMM-Newton observations of the Crab nebula compared to observations made in the radio wavelengths.</p>

Reproductive timing often affects reproductive success. Plants and animals in a multitude of habitats time reproduction to coincide with environmental conditions that are conducive to fertilization or offspring growth and survival. Many marine organisms time the release of planktonic larvae with large amplitude nocturnal tides. These conditions sweep the newly hatched offspring away from shore, and high densities of predators, while diurnally feeding predators are inactive. Experimental work has supported the hypothesis that these strong cycles of reproduction are driven by the avoidance of predators. However, how planktonic predation risk varies across interacting environmental cycles remains unclear. I used tethered adult and larval brine shrimp to assess the risk of predation across diel, tidal amplitude and seasonal cycles (upwelling vs. nonupwelling). The proportion of prey items lost was higher during the day than at night for larvae, but showed the opposite trend for adults. On the Pacific coast of Panama, the pattern of higher diurnal predation on larvae remained consistent across seasons, but risk increased overall during upwelling. Thus, the release of larvae at night should indeed increase early larval survival. Matching reproductive timing with particular times in environmental cycles may be hampered by the inverse effect of temperature on developmental rate. For brooding organisms that reproduce across seasonal changes in temperature, changes in incubation period will result in errors in timing of larval release if adjustments to temperature are not made. Using laboratory and field experiments, I examined the effect of temperature and temperature variation on the timing of larval release of two species of fiddler crabs both of which usually release larvae during large amplitude nocturnal tides. I found that Uca terpsichores maintained timing in the field during low but constant temperature but made errors in timing when temperature varied during incubation. Uca deichmanni maintained accurate and precise timing of larval release in the field despite variable temperature but released larvae late in cold conditions in the lab. To determine whether these species reduce temperature-induced timing errors by shifting when they mate, I measured courtship intensity across seasonal temperature changes at field sites with different thermal properties. Both species exhibit strong cycles of courtship linked with tidal amplitude that result in their strong cycles of larval release. I found that courtship cycles and tidal amplitude for U. deichmanni remained strongly correlated across spatial and temporal differences in temperature. In contrast, the relationship between courtship and tidal amplitude for U. terpsichores changed across sites and with seasonal temperature variation. U. terpsichores respond to temperature variation by changing when they mate while U. deichmanni do not. Predictions for the effect of climate change on seasonal upwelling of cold water include increased variability and increased intensity in upwelling. The predictive nature of adjustment by U. terpsichores means that they may be more vulnerable to timing errors with increased temperature variability while behavioural adjustments by U. deichmanni during incubation may make them more vulnerable to increased intensity of upwelling. The combination of timing errors that result from upwelling induced temperature variation and the seasonal increase in predation risk during upwelling may have significant impacts on early larval survival.<br>Le moment de reproduction a souvent une influence sur le succès reproducteur. Chez les plantes et les animaux, plusieurs espèces provenant de divers habitats synchronisent leur reproduction avec les conditions environnementales favorables à la fertilisation ou à la croissance et la survie de leur progéniture. Plusieurs organismes marins adaptent la libération de leurs larves planctoniques aux marées nocturnes de plus grande amplitude. Lors de ces marées, les larves récemment écloses sont éloignées du rivage, où l'on retrouve la plus forte densité de prédateurs potentiels, et échappent également aux prédateurs diurnes. Jusqu'à présent, des études expérimentales ont soutenu l'hypothèse que les périodes de reproduction étaient déterminées par l'évitement des prédateurs. Cependant, malgré l'importance des effets de la prédation sur le rythme de vie des organismes marins, l'impact d'autres facteurs environnementaux cycliques pouvant avoir des effets sur le risque de prédation n'a pas été démontré. Afin d'étudier cette possibilité, j'ai utilisé des artémies adultes et au stade larvaire comme proies afin d'évaluer le risque de prédation à travers les cycles journaliers, saisonniers et d'amplitude des marées (remontée d'eau vs. non-remontée d'eau). Mes résultats ont démontré que la proportion de proies perdues lors de ces expériences variait de façon significative entre le jour et la nuit, ainsi qu'entre le type de proie (adulte ou larve). Pour les adultes artémias, le risque de prédation était plus grand la nuit que durant le jour ; contrairement aux larves où leur risque de prédation était plus grand le jour. Sur la côte Pacifique du Panama, le cycle journalier des larves artémias s'est maintenu de manière constante à travers les saisons mais le risque de prédation a augmenté durant la période de remontée d'eau. En conséquence, le taux de survie des larves primitives devrait augmenter si les périodes de reproduction sont contrôlés avec précision. Cependant, le fait de synchroniser le cycle de reproduction avec des périodes optimales dans des cycles environnementaux peut être entravé par l'effet inverse que la température peut avoir sur le rythme de développement. Pour les espèces ovipares se reproduisant à l'année, donc sujets à des variations de température, des ajustements doivent être faits quant à la période d'incubation, sinon cela pourrait entraîner des erreurs au niveau du moment propice à la libération des larves. En combinant des expériences en laboratoire et sur le terrain, j'ai examiné l'effet de la température et des variations de température sur le moment de libération des larves de deux espèces de crabes violonistes qui normalement libèrent leurs larves lors des marées du printemps. Mes résultats ont montré que, sur les sites de recherche, l'espèce Uca terpsichores a maintenu le bon moment de libération des larves lors des périodes constantes de basses températures, mais que des erreurs ont été observées lorsque le changement de température se produisait durant la période d'incubation. La seconde espèce, U. deichmanni, a su maintenir le bon moment de libération des larves sur les sites de recherche, et ce malgré des changements de température, mais un délai dans la libération des larves a été observé dans des conditions de basse température en laboratoire. Afin de déterminer si ces deux espèces réduisent l'effet des erreurs causées par les changements de température sur la libération des larves en modifiant le moment de l'accouplement, j'ai mesuré l'intensité de la parade (cour) durant les changements saisonniers de température dans plusieurs sites de recherche ayant différentes conditions thermiques. Les résultats montrent que le cycle de cour des deux espèces est fortement lié aux cycles et aux amplitudes des marées et il semble que cela ait un effet important sur le moment de libération des larves.

Hardware and software complexity of future critical real-time systems challenges the scalability of traditional timing analysis methods. Measurement-Based Probabilistic Timing Analysis (MBPTA) has recently emerged as an industrially-viable alternative technique to deal with complex hardware/software. Yet, MBPTA requires certain timing properties in the system under analysis that are not satisfied in conventional systems. In this thesis, we introduce, for the first time, hardware and software solutions to satisfy those requirements as well as to improve MBPTA applicability. We focus on one of the hardware resources with highest impact on both average performance and Worst-Case Execution Time (WCET) in current real-time platforms, the cache. In this line, the contributions of this thesis follow three different axes: hardware solutions and software solutions to enable MBPTA, and MBPTA analysis enhancements in systems featuring caches. At hardware level, we set the foundations of MBPTA-compliant processor designs, and define efficient time-randomised cache designs for single- and multi-level hierarchies of arbitrary complexity, including unified caches, which can be time-analysed for the first time. We propose three new software randomisation approaches (one dynamic and two static variants) to control, in an MBPTA-compliant manner, the cache jitter in Commercial off-the-shelf (COTS) processors in real-time systems. To that end, all variants randomly vary the location of programs' code and data in memory across runs, to achieve probabilistic timing properties similar to those achieved with customised hardware cache designs. We propose a novel method to estimate the WCET of a program using MBPTA, without requiring the end-user to identify worst-case paths and inputs, improving its applicability in industry. We also introduce Probabilistic Timing Composability, which allows Integrated Systems to reduce their WCET in the presence of time-randomised caches. With the above contributions, this thesis pushes the limits in the use of complex real-time embedded processor designs equipped with caches and paves the way towards the industrialisation of MBPTA technology.<br>La complejidad de hardware y software de los sistemas críticos del futuro desafía la escalabilidad de los métodos tradicionales de análisis temporal. El análisis temporal probabilístico basado en medidas (MBPTA) ha aparecido últimamente como una solución viable alternativa para la industria, para manejar hardware/software complejo. Sin embargo, MBPTA requiere ciertas propiedades de tiempo en el sistema bajo análisis que no satisfacen los sistemas convencionales. En esta tesis introducimos, por primera vez, soluciones hardware y software para satisfacer estos requisitos como también mejorar la aplicabilidad de MBPTA. Nos centramos en uno de los recursos hardware con el máximo impacto en el rendimiento medio y el peor caso del tiempo de ejecución (WCET) en plataformas actuales de tiempo real, la cache. En esta línea, las contribuciones de esta tesis siguen 3 ejes distintos: soluciones hardware y soluciones software para habilitar MBPTA, y mejoras de el análisis MBPTA en sistemas usado caches. A nivel de hardware, creamos las bases del diseño de un procesador compatible con MBPTA, y definimos diseños de cache con tiempo aleatorio para jerarquías de memoria con uno y múltiples niveles de cualquier complejidad, incluso caches unificadas, las cuales pueden ser analizadas temporalmente por primera vez. Proponemos tres nuevos enfoques de aleatorización de software (uno dinámico y dos variedades estáticas) para manejar, en una manera compatible con MBPTA, la variabilidad del tiempo (jitter) de la cache en procesadores comerciales comunes en el mercado (COTS) en sistemas de tiempo real. Por eso, todas nuestras propuestas varían aleatoriamente la posición del código y de los datos del programa en la memoria entre ejecuciones del mismo, para conseguir propiedades de tiempo aleatorias, similares a las logradas con diseños hardware personalizados. Proponemos un nuevo método para estimar el WCET de un programa usando MBPTA, sin requerir que el usuario dentifique los caminos y las entradas de programa del peor caso, mejorando así la aplicabilidad de MBPTA en la industria. Además, introducimos la composabilidad de tiempo probabilística, que permite a los sistemas integrados reducir su WCET cuando usan caches de tiempo aleatorio. Con estas contribuciones, esta tesis empuja los limites en el uso de diseños complejos de procesadores empotrados en sistemas de tiempo real equipados con caches y prepara el terreno para la industrialización de la tecnología MBPTA.

Thesis (Ph. D.)--University of California, San Diego, 2006.<br>Title from first page of PDF file (viewed May 18, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 110-113).

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Kenan-Flagler Business School." Discipline: Business Administration; Department/School: Business School, Kenan-Flagler.