The performance of low latency Network on Chip (NoC) architectures, which incorporate fast bypass paths to reduce communication latency, is limited by crosstalk induced skewing of signal transitions on link wires. As a result of crosstalk interactions between wires, signal transitions belonging to the same flit or bit vector arrive at the destination at different times and are likely to violate setup and hold time constraints for the design. This thesis proposes a two-step technique: TransSync- RecSync, to dynamically eliminate packet errors resulting from inter-bit-line transition skew. The proposed approach adds minimally to router complexity and involves no wire overhead. The actual throughput of NoC designs with asynchronous bypass designs is evaluated and the benefits of augmenting such schemes with the proposed design are studied. The TransSync, TransSync-2-lines and RecSync schemes described here are found to improve the average communication latency by 26%, 20% and 38% respectively in a 7X7 mesh NoC with asynchronous bypass channel. This work also evaluates the bit-error ratio (BER) performance of several existing crosstalk avoidance and error correcting schemes and compares them to that of the proposed schemes. Both TransSync and RecSync scheme are dynamic in nature and can be switched on and off on-the-fly. The proposed schemes can therefore be employed to impart unequal error protection (UEP) against intra-flit skewing on NoC links. In the UEP, a larger fraction of the energy budget is spent in providing protection to those parts of the data being transmitted on the link which have a higher priority, while expending smaller effort in protecting relatively less important parts of the data. This allows us to achieve the prescribed level of performance with lower levels of power. The benefits of the presented technique are illustrated using an H.264 video decoder system-on-chip (SoC) employing NoC architecture. We show that for Akyio test streams transmitted over 3mm long link wires, the power consumption can be reduced by as much as 20% at the cost of an acceptable degradation in average peak signal to noise ratio (PSNR) with UEP.

ABSTRACT Presently, many industrial applications of gear sets with skew axes, especially worm gear and hypoid gear, are most widely used. The main content of this thesis is to construct the contact analysis model of the line-contacted type tooth profile of gear sets with skew axes with assembly error. The influence of geometrical parameters of skew-axes gear to the transmission error is analyzed. The complex method for optimization is implemented to select the better skew-axes gear parameters with the best performance in transmission error with assembly error. To prove the presented analysis model, the optimized gear parameters are utilized to construct the solid model for analyzing the contact properties by using computer simulation program.

The torsional rigidity of tub-girder makes them ideal for use in curved bridges. The use on skewed support applications by bridge designers is limited as the behavior is complex and requires the use of advanced analysis tools. In consequence, a simplified analysis method to account for the effects of skew on tub-girder twist rotations and internal torques and how these affect the internal component forces was proposed. The combined effects of skew and curvature are studied by examining the results for analysis with different levels of sophistication for 18 representative bridges. The data generated constitutes the first systematic study on a large set of curved and skewed tub-girder bridges using consistent, refined 3D FEA models to model construction forces and deformations. Comparisons of the simplified analysis method to the refined 3D FEA analysis display the limitations of the simplified analysis and present potential sources of error. Furthermore, the results from the 3D FEA helped identify interactions between components and, therefore, an improved simplified procedure was proposed to account for the effects of the resulting increased stresses. In addition, the bridge erection procedures are discussed and specific examples illustrating the calculation of the fit-up forces is presented. These findings provided additional tools for the analysis process and erection engineering to account for the effects of skew. Lastly, further research needs considering the analysis of additional loading conditions and construction procedures are described.

Unordered choice models are commonly used in the field of transportation and several other fields to analyze discrete choice behavior. In the past decade, there have been substantial advances in specifying and estimating such models to allow unobserved taste variations and flexible error covariance structures. However, the current estimation methods are still computationally intensive and often break down when spatial dependence structures are introduced (due to the resulting high dimensionality of integration in the likelihood function). But a recently proposed method, the Maximum Approximate Composite Marginal Likelihood (MACML) method, offers an effective approach to estimate such models. The MACML approach combines a composite marginal likelihood (CML) estimation approach with an approximation method to evaluate the multivariate standard normal cumulative distribution (MVNCD) function. The composite likelihood approach replaces the likelihood function with a surrogate likelihood function of substantially lower dimensionality, which is then subsequently evaluated using an analytic approximation method rather than simulation techniques. This combination of the CML with the specific analytic approximation for the MVNCD function is effective because it involves only univariate and bivariate cumulative normal distribution function evaluations, regardless of the dimensionality of the problem. For my dissertation, I have four objectives. The first is to evaluate the performance of the MACML method to estimate unordered response models by undertaking a Monte Carlo simulation exercise. The second is to formulate and estimate a spatial and temporal unordered discrete choice model and apply this model to a land use change context and to the mode choice decision of school children. The third objective is to formulate a random coefficient model with non-normal mixing distributions on model parameters which can be estimated using the MACML approach. Finally, the fourth objective us to propose an improvement to the MACML method by incorporating a second order MVNCD function that is more accurate and evaluate its performance in estimating parameters for a variety of model structures. / text

Τα σώματα, κυρίως τα μη αντιμεταθετικά, γενικά κατασκευάζονται ως σώματα κλασμάτων δακτυλίων, εντούτοις δεν έχουν όλοι οι δακτύλιοι σώμα κλασμάτων και για δοθέντα δακτύλιο μπορεί να είναι αρκετά δύσκολο να αποφανθούμε αν υπάρχει σώμα κλασμάτων. Στο κεφάλαιο 1 θα αναφέρουμε ορισμένες γενικές παρατηρήσεις πάνω στο είδος των συνθηκών, οι οποίες χαρακτηρίζουν την εμβάπτιση δακτυλίου σε σώμα κλασμάτων και δίνουμε αναγκαίες συνθήκες οι οποίες σχετίζονται με την τάξη των ελεύθερων modules. Στη συνέχεια περιγράφουμε τις συνθήκες του Ore για την εμβάπτιση αυτή, όπου γενικεύεται η αντιμεταθετική περίπτωση. Στο δεύτερο κεφάλαιο εισάγουμε στοιχεία από τη γενική θεωρία τοπολογικών δακτυλίων και modules. Πιο συγκεκριμένα, παρουσιάζονται θεμελιώδεις έννοιες και βασικά αποτελέσματα πάνω στους τοπολογικούς δακτύλιους και τα τοπολογικά σώματα, δίνοντας ιδιαίτερη έμφαση στα στρεβλά σώματα. Πιο συγκεκριμένα εξετάζουμε φραγμένα σύνολα, τοπολογικούς μηδενοδιαιρέτες, τοπολογικά μηδενοδύναμα στοιχεία και minimal τοπολογίες. Αναφέρουμε, επίσης αρκετά παραδείγματα τοπολογιών επί δακτυλίων και modules. Στο κεφάλαιο 3 ορίζουμε διατιμήσεις επί των στρεβλών σωμάτων και ασχολούμαστε με το πρόβλημα ύπαρξης ψευδό-διατιμήσεων σε δακτυλίους και modules. / Fields, especially skew fields, are generally constructed as the field of fractions of some ring, but of course not every ring has a field of fractions and for a given ring it may be quite difficult to decide if a field of fractions exists. In chapter 1 we shall bring some general observations on the kind of conditions to expect and give some necessary conditions relating to the rank of free modules. On the other hand there is the Ore condition generalizing the commutative case. Chapter 2 provides fundamental concepts and basic results on topological rings, modules and especially on skew fields. Under detailed consideration are bounded subsets, topological divisors of zero, topologically nilpotent elements and minimal topologies. There are also many examples of topologies on rings and modules. In chapter 3 we define norms on skew fields and discuss the problem of the existence of real-valued pseudonorms rings and modules.

Šiame baigiamajame magistro darbe išanalizuota įstrižai lenkiamos daugiasluoksnės sijos standumo priklausomybė nuo medžiagos tamprumo modulio ir sijos stiprumas nuo sijos geometrinių parametrų. Tyrimo objektu buvo pasirinkti du nelygiašoniai kampuočiai 100x63x6, 100x63x10 ir vienas lygiašonis 100x100x6. Kampuočiai užpildomi skirtingo tamprumo modulio medžiagomis. Sijos galas apkraunamas 10 kN jėga. Sijoje įstrižas lenkimas susidaro dėl kampučio ir užpildo tamprumo modulio skirtumo, todėl sijos standumo centro koordinatės nebesutampa su geometrinio centro koordinatėmis. Užpildytas kampuotis pasirinktas dėl praktinės naudos, nes jį užpildžius kita pigesne medžiaga, padidinamas jo standumas įstrižam lenkimui. Sija tampa kvadrato ar stačiakampio formos, kas leidžia lengviau montuoti siją jai skirtoje vietoje. Tyrimui atlikti panaudojami du metodai - tai analitiniai skaičiavimai ir BEM (Baigtinių Elementų Metodas). Rezultatuose palyginami rezultatai gauti iš analitinių skaičiavimų ir iš BEM. / In this Master of Science thesis was analyzed skew bended multilayer beams stiffness dependence on material elastic modulus and strength of the beam from the beam geometrical parameters and elastic modulus. As the Objects of investigation was selected two scalene angles 100x63x6, 100x63x10, and one isosceles 100x100x6. Scalene angles were filled with different materials of different elastic modulus. End of the beam was loaded 10 kN force. Skew bend in this multilayer beam arise because the elastic modulus of angles and filled materials are different, and then the coordinate system of stiffness center do not coincident with geometrical coordinate system. Filled angle was chosen for practical use, because when we filled it with another cheaper material, it could be increased the skew bending stiffness. Beam become square or rectangular, that allows easier installation of the beam in place. Survey used two methods - the analytical calculations and FEA (Finite Element Analysis). The results were obtained from analytical calculations and the FEA, and compared.

Model-based clustering allows for the identification of subgroups in a data set through the use of finite mixture models. When applied to high-dimensional microarray data, we can discover groups of genes characterized by their gene expression profiles. In this thesis, a mixture of skew-t factor analyzers is introduced for the clustering of high-dimensional data. Notably, we make use of a version of the skew-t distribution which has not previously appeared in mixture-modelling literature. Allowing a constraint on the factor loading matrix leads to two mixtures of skew-t factor analyzers models. These models are implemented using the alternating expectation-conditional maximization algorithm for parameter estimation with an Aitken's acceleration stopping criterion used to determine convergence. The Bayesian information criterion is used for model selection and the performance of each model is assessed using the adjusted Rand index. The models are applied to both real and simulated data, obtaining clustering results which are equivalent or superior to those of established clustering methods.

We explore using pulsed latches for timing optimization -- a first in the academic FPGA community. Pulsed latches are transparent latches driven by a clock with a non-standard (i.e. not 50%) duty cycle. As latches are already present on commercial FPGAs, their use for timing optimization can avoid the power or area drawbacks associated with other techniques such as clock skew and retiming. We propose algorithms that automatically replace certain flip-flops with latches for performance gains. Under conservative short path or minimum delay assumptions, our latch-based optimization, operating on already routed designs, provides all the benefit of clock skew in most cases and increases performance by 9%, on average, essentially for "free". We show that short paths greatly hinder the ability of using pulsed latches, and further improvements in performance are possible by increasing the delay of certain short paths.

We explore using pulsed latches for timing optimization -- a first in the academic FPGA community. Pulsed latches are transparent latches driven by a clock with a non-standard (i.e. not 50%) duty cycle. As latches are already present on commercial FPGAs, their use for timing optimization can avoid the power or area drawbacks associated with other techniques such as clock skew and retiming. We propose algorithms that automatically replace certain flip-flops with latches for performance gains. Under conservative short path or minimum delay assumptions, our latch-based optimization, operating on already routed designs, provides all the benefit of clock skew in most cases and increases performance by 9%, on average, essentially for "free". We show that short paths greatly hinder the ability of using pulsed latches, and further improvements in performance are possible by increasing the delay of certain short paths.

Malhas de relógio são arquiteturas de rede de relógio adequadas para distribuir confiavelmente o sinal de relógio na presença de variações de processo e ambientais. Tal propriedade se torna muito importante nas tecnologias submicrônicas onde variações têm um papel importante. A confiabilidade da malha de relógio é devido aos caminhos redundantes conectando o sinal de relógio até os receptores de forma que variações afetando um caminho possam ser compensadas pelos outros caminhos. A confiabilidade vem ao custo de mais consumo de potência e fiação. Desta forma fica claro o balanceamento necessário entre distribuir confiavelmente o sinal de relógio (mais redundância) e o consumo de potência e aumento de fiação. O clock skew é definido como a diferença entre os tempos de chegada do sinal de clock nos seus receptores. Quanto maior é o clock skew, mais lento o circuito precisa operar. Além de diminuir a velocidade do circuito, um valor alto de clock skew aumenta a probabilidade de o circuito não funcionar devido às variações. Neste trabalho, nos focamos no problema de clock skew. Inicialmente extraímos informações úteis de como o comprimento da fiação e a capacitância variam a medida que o tamanho da malha varia. São apresentadas fórmulas analíticas que encontram o tamanho ótimo para ambos objetivos e é apresentado um estudo de como o clock skew varia a medida que nos afastamos do tamanho ótimo da malha de relógio. Um método para a redução de clock skew através do deslocamento dos buffers também é apresentado. Tal melhoria no clock skew não afeta o consumo de potência já que o tamanho dos buffers e a malha não são alterados. / Clock meshes are a suitable clock network architecture for reliably distributing the clock signal under process and environmental variations. This property becomes very important in the deep sub-micron technology where variations play a main role. The clock mesh reliability is due to redundant paths connecting clock buffers to clock sinks, so that variations affecting one path can be compensated by other paths. This comes at cost of more power consumption and wiring resources. Therefore it is clear the tradeoff between reliably distributing the clock signal (more redundancy) and the power and resource consumption. The clock skew is defined as the difference in the arrival time of clock signal at clock sinks. The higher is the clock skew, the slower is the circuit. Besides slowing down the circuit operation, a high clock skew increases the probability of circuit malfunction due to variations. In this work we focus on the clock skew problem. We first extract some useful information on how the clock wirelength and capacitance change as the mesh size changes. We present analytical formulas to find the optimum mesh size for both goals and study how the clock skew varies as we move further away from the optimum mesh size. We also present a method for reducing the clock mesh skew by sliding buffers from the position where they are traditionally placed. This improvement comes at no increasing cost of power consumption since the buffer size and the mesh capacitance are not changed.