The present thrust in the electronics industry towards integrating multiple functions on a single chip while operating at very high frequencies has highlighted the need for efficient Electronic Design Automation (EDA) tools to shorten the design cycle and capture market windows. However, the increasing complexity in modern circuit design has made simulation a computationally cumbersome task. The notion of model order reduction has emerged as an effective tool to address this difficulty. Typically, there are numerous approaches and several issues involved in the implementation of model-order reduction techniques. Among the important ones of those issues is the problem of determining a suitable order (or size) for the reduced system. An optimal order would be the minimal order that enables the reduced system to capture the behavior of the original (more complex and larger) system up to a user-defined frequency. The contribution presented in this thesis describes a new approach aimed at determining the order of the reduced system. The proposed approach is based on approximating the impulse response of the original system in the time-domain. The core methodology in obtaining that approximation is based on numerically inverting the Laplace-domain of the representation of the impulse response from the complex-domain (s-domain) into the time-domain. The main advantage of the proposed approach is that it allows the order selection algorithm to operate directly on the time-domain form of the impulse response. It is well-known that numerically generating the impulse response in the time-domain is very difficult and its not impossible, since it requires driving the original network with the Dirac-delta function, which is a mathematical abstraction rather than a concrete waveform that can be implemented on a digital computer. However, such a difficulty is avoided in the proposed approach since it uses the Laplace-domain image of the impulse response to obtain its time-domain representation. The numerical simulations presented in the thesis demonstrate that using the time-domain waveform of the impulse response, computed using the proposed approach and properly filtered with a Butterworth filter, guides the order selection algorithm to select a smaller order, i.e., the reduced system becomes more compact in size. The phrase "smaller or more compact" in this context refers to the comparison with existing techniques currently in use, which seek to generate some form of time-domain approximations for the impulse response through driving the original network with pulse-shaped function (e.g., Gaussian pulse).

This study examines the linkages between output growth and output volatility in the G7 countries over the period 1958M2-2013M8. Using the VAR-based spillover index approach by Diebold and Yilmaz (2012) we find that: i) output growth and volatility are highly intertwined; ii) spillovers have reached unprecedented levels during the global financial crisis; and iii) the US has been the largest transmitter of growth and volatility shocks. Generalized impulse response analyses suggest moderate growth spillovers and sizable volatility spillovers across countries. Cross-variable effects indicate that volatility shocks lead to lower growth, while growth shocks reduce output volatility.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The musician needs to properly perceive the sound in rooms where it operates, either in an environment designed to be performed or to studying and practice music. For this, it is necessary that these sites are acoustically appropriate, enabling the development and enhancement of musical sound perception. In this study six classrooms of the music school of UFSM were characterized by acoustic impulse response measurements and computer simulation, and considered the user s feedback through questionnaires. The questionnaires enabled to understand the preferences of students and music teachers regarding the acoustic quality of a total of twenty rooms for music practice and teaching. Three study rooms and three collective classrooms were the most cited out of those available for the course, which were evaluated by acoustic impulse response, resulting in achieving specified objectives of the main parameters to assess the acoustic quality of rooms by ISO 3382: 2009. The information provided by the musicians proved to be coherent with the measurement data, as the rooms considered dry had presented reverberation times around 0.4 s, and the rooms considered reverberants had reverberation times (RT) around 1.5 s. The six rooms were characterized as clear and well defined rooms, with values for Clarity ranging between 1.0 and 2.0 dB for live rooms and around 22 dB for dry rooms. The definition has remained above 43% for all rooms with Central Time below 50 ms for rooms of greater clarity and less reverberant, and above 90 ms for the live rooms. In general, most rooms were considered weak in relation to acoustic conditioning, and only two out of twenty rooms were considered adequate by most musicians, without receiving considerable negative criticism, being one a study room with a volume of 79.9 m³ and TR equal to 0.4 seconds, and the other a collective classroom with a volume of 327.85 m³ and TR equal to 1.6 s. The computer simulation was efficient for the prediction of the acoustic behavior of the rooms in study and the data obtained in the simulations were compared to the just noticeable difference (JND) for acoustic parameters investigated (T30, EDT, C80, D50 and Ts). A good correlation was observed between measured and simulated data, particularly for parameters related to noise energy in the frequency range from 63 to 8.000 Hz. / O músico necessita perceber adequadamente o som nos recintos onde atua, seja em ambientes destinados à performance, seja em ambientes destinados ao estudo e prática musical. Para que isto seja possível é necessário que estes locais estejam acusticamente adequados, permitindo o desenvolvimento e aprimoramento da percepção sonora musical. No presente trabalho seis salas de aula do curso de graduação em Música da UFSM foram caracterizadas através de medições acústicas da resposta impulso e de simulação computacional, além de considerar a opinião dos usuários mediante questionários. Os questionários aplicados permitiram compreender as preferências dos estudantes e professores de música no que se refere à qualidade acústica de um total de vinte salas para prática e ensino musical. Três salas de estudo e três salas de aula coletiva foram as mais citadas dentre as disponíveis para o curso, as quais foram avaliadas acusticamente através da resposta impulso, resultando na obtenção dos principais parâmetros objetivos especificados para a avaliação da qualidade acústica de salas pela norma ISO 3382: 2009. As informações fornecidas pelos músicos se mostraram coerentes com os dados das medições, de forma que e as salas consideradas secas apresentaram tempos de reverberação (TR) em torno de 0,4 s, e as salas consideradas reverberantes apresentaram tempos de reverberação em torno de 1,5 s. As seis salas se caracterizaram como salas claras e definidas, com valores para Clareza variando entre 1,0 e 2,0 dB para as salas vivas e em torno de 22 dB para as salas secas. A Definição se manteve acima de 43% para todas as salas, com Tempo Central abaixo de 50 ms para salas mais claras e menos reverberantes e acima de 90 ms para as salas mais vivas. Em geral, a maioria das salas apresenta deficiências em relação ao condicionamento acústico, sendo que somente duas das vinte salas foram consideradas adequadas pela maioria dos músicos, sem receber críticas negativas consideráveis, sendo uma sala de estudo com volume de 79,9 m³ e TR igual a 0,4 s, e uma sala de aula coletiva com volume de 327,85 m³ e TR igual a 1,6 s. A simulação computacional se mostrou eficiente para predição do comportamento acústico das salas em questão e os dados obtidos nas simulações foram comparados em relação à diferença no limite do observável (JND) para os parâmetros acústicos investigados (T30, EDT, C80, D50 e Ts). Uma boa correlação foi observada entre dados medidos e simulados, principalmente para os parâmetros relacionados à energia sonora na faixa de frequência de 63 a 8.000 Hz.

Neste trabalho são analisados os campos acústicos gerados por transdutores ultrassônicos planos e circulares, do tipo pistão plano, no modo pulso-eco, trabalhando como emissor e receptor de ondas, com freqüências de 1,6 MHz, 2,25 MHz e 5 MHz. As ondas emitidas por esses transdutores interagem com interfaces denominadas alvos, com diversas geometrias de superfícies, como planas e circulares, planas com cavidade do tipo alvéolo circular, e cone reto, todas compostas de alumínio e imersas em tanque com água. O campo acústico refletido varia de acordo com o tipo de geometria do alvo. Para essas analises foram produzidas e comparadas modelagens do campo acústico no software Matlab, por meio de dois modelos teóricos: método da resposta impulsiva e método da representação discreta. Foram analisados o tempo de computação produzido pelo método numérico com relação a discretização dos elementos de área do transdutor e do alvo, alem da influencia da conversão de modo nas respostas impulsivas simuladas para essas superfícies. Os resultados mostraram uma boa correlação entre os dois métodos teóricos, porem o de representação discreta possibilita o estudo em transdutores com geometria diferente do pistão plano, sem o uso de integrais complexas. As diferenças dos resultados experimentais e teóricos podem ser minimizadas por meio de uma escolha adequada da relação entre a discretização e comprimento de onda (Dx/), em que foi considerado um valor aceitável de erro relativo de 15% para Dx/ 0,68. Foi observado que o uso da conversão de modo na interface refletora influi apenas na amplitude do sinal de eco (atenuação) e não na forma do sinal. / This work deals with acoustic fields generated by ultrasonic broadband transducers as a planar circular piston, operating in pulse-echo mode, with frequencies of 1.6 MHz, 2.25 MHz and 5 MHz. The waves emitted by transducers interact with water-immersed aluminum targets of different geometries such as planar circular surfaces, concave circular cavity on plane surfaces, and right circular conical surfaces. The impulse response and the discrete representation methods were applied to model the echo responses, using the Matlab software. The influence of mode conversion over the simulated impulse responses for these surfaces was analyzed. The results show a good correlation between the two theoretical methods, but the discrete representation enables the study of arbitrary aperture transducers, with no need to solve complex integrals. The computational times of the discrete representation method was analyzed were respect to the spatial discretization of both the transducer aperture and the target. Experimental tests were carried out to validate the simulated results. Differences in experimental and theoretical results can be minimized by an appropriate choice of the discretization/wavelength ratio (Dx / ). A relative error of 15% was considered acceptable for Dx / 0,68. It was observed that the use of mode conversion at the reflected interface modifies only the amplitude of the echo signal (attenuation), but not its shape.

The aim of this work is understand how the Exchange rate volatility affects the cearensesâs exports. Many researchers have appointed that an increase in the exchange rate volatility generate risk factors on trade. Therefore, understand the relationship between volatility and trade is fundamental to forecast better the behavior of trade under instabilities of the exchange markets, as the recent international crisis. The period of analysis is from 2002 to 2011 and the data has monthly frequency. Two methodologies are used to investigate this relationship: short run, through impulse response function, obtained from a VEC; long run, through the Johansen cointegration test. The results showed that the exchange volatility reduces the exports of CearÃ. / O objetivo deste trabalho à entender como a volatilidade da taxa de cÃmbio afeta as exportaÃÃes cearenses. Diversos autores tÃm apontado que uma volatilidade da taxa de cÃmbio mais elevada pode estar associada a fatores de risco de exportaÃÃo e importaÃÃo. Dessa forma, entender o relacionamento entre esses componentes à fundamental para aumentar o poder de previsibilidade, especialmente, em perÃodos de instabilidade econÃmica, em que a volatilidade da taxa de cÃmbio tende a ser maior. Nesse trabalho, utilizou-se de dados com frequÃncia mensal entre 2002 a 2012. Duas anÃlises foram feitas: uma de curto prazo, atravÃs da abordagem de funÃÃes impulso resposta obtidas a partir de um VEC e outra de longo prazo atravÃs do teste de cointegraÃÃo de Johansen (1991). Dos resultados encontrados, verificou-se que a volatilidade da taxa de cÃmbio tem efeito sobre as exportaÃÃes cearenses tanto no curto quanto no longo prazo. Ambos, longo e curto prazo, a volatilidade da taxa de cambio reduz o quantum exportado, indicando que tal volatilidade pode ser interpretada como risco associado as exportaÃÃes.

The main focus of this thesis rests in the assessment of the quantitative easing policy impact on commodity prices and prices of commodity derivatives in the US. Several VAR models have been constructed in this paper to capture the relations between time series of monetary policy variables and commodity markets indices. The impulse-response analysis applied in the VAR models has discovered the causal connection between the QE policy and the value of commodity indices. The official announcement of initiation (extension) of the policy of the QE policy and its realization consisting of purchases of vast amount of treasury securities and federal agency debt and MBS has lead to the major commodity indices increase. Since this fact has been overlooked by Fed so far, its acceptance might enhance the realization of possible future QE policy and the valuation of the QE as a monetary policy alternative in conditions of zero-bound.

Thesis (M. Com. (Economics)) -- University of Limpopo, 2019 / Financial markets and quite a diverse number of financial instruments have been growing in a controlled manner in recent decades in terms of value and volume. Brazil, Russia, India, China and South Africa (BRICS) are distinguished as having the fast growing markets in the universe compared to other markets of emerging economies, according to their promising economic prospective and demographic power. This study investigated the effects of government stock on investment activity in BRICS countries. This study used panel autoregressive distributed lag model (PARDL), Engel-Granger causality test, impulse response functions (IRF) and variance decomposition tests. Such techniques were applied to the annual data for the periods 2001 to 2016 in order to determine the effects of government stock on investment activity. The variables (government stock on bonds, government stock on mutual banks, government stock on corporations and government stock on liquid assets), including gross fixed capital formation which is a measure of investment activity, were subjected to panel unit root tests and that confirmed different orders of cointegration. The existence of a long run relationship between investment activity and other macroeconomic variables used in this study was determined by means of the panel cointegration tests, where one lag was used. The PARDL showed that in the long run investment activity was positively influenced by government stock on mutual banks and government stock on liquid assets, and negatively related to government stock on bonds and government stock on corporations. The Engel-Granger causality test revealed existence of unidirectional movement between investment activity and government stock on corporations as well as from government stock on bonds to liquid assets. The impulse response function test showed the impulse percentage of fluctuation that the variables did contribute to each other, from various periods both in the short and long run. While the variance decomposition of investment indicated that Investment was shocked by its own innovations throughout all the periods. A critical evaluation is needed to avoid investment shocks, instability of investment activity, instability of financial markets and the economy as a whole.

Measurements in a reverberation chamber use spatially averaged squared pressure to calculate sound absorption, sound power, and other sound measurements. While a reverberation chamber provides an approximation of a diffuse sound field, variations in the measurements introduce uncertainty in measurement results. Room qualification procedures require a sufficient number of source-receiver locations to obtain suitable measurements. The total acoustic energy density provides greater spatial uniformity than squared pressure, which requires fewer source-receiver positions to produce similar or better accuracy in measurement results. This paper explores the possibility of using energy density in place of squared pressure, using methods outlined in current ISO standards, by describing several experimental and analytical results.

This research examines the impact of external shocks on Nigeria’s output performance for the period 1981 – 2015. It aims to bring to the fore the importance of considering external shocks during policy design and implementation. The multivariate VAR and VECM frameworks were used to evaluate the impact of the shock variables on Nigeria’s output performance and to achieve the stated objectives. Findings show that the external shock and domestic policy variables have short-run effects on Nigeria’s output performance. Also, all the measures of external shocks and domestic policies display some viable information in explaining the variabilities in Nigeria’s output performance over the horizon. The comparison between the results of the VECM and the unrestricted VAR shows that the unrestricted VAR model outperformed the VECM. The overall result of the study confirms the view about the vulnerability of the Nigerian economy to external shocks. These shocks explain more than half of the variance in real output performance and have varying effects on output performance in Nigeria. The dynamic response of output performance to each of the defined shock variables show that output performance responds rapidly to the shock variables, while its response to the domestic economic variables is seemingly moderate. Finally, the variance decomposition show that international crude oil price and terms of trade have the largest share in accounting for the variability in output performance, followed closely by the shares of capital inflows and monetary policy.

Floors have traditionally been designed only for strength and deflection serviceability. As technological advances have been made in medical, scientific and micro-electronics manufacturing, many types of equipment have become sensitive to vibration of the supporting floor. Thus, vibration serviceability has become a routinely evaluated limit state for floors supporting sensitive equipment. Equipment vibration tolerance limits are sometimes expressed as waveform peak acceleration, and are more often expressed as narrowband spectral acceleration, or one-third octave spectral velocity. Current floor vibration prediction methods, such as those found in the American Institute of Steel Construction Design Guide 11, Floor Vibrations Due to Human Activity, the British Steel Construction Institute P354, Design of Floors for Vibration: a New Approach and the British Concrete Centre CCIP-016 A Design Guide for Footfall Induced Vibration of Structures, have limitations. It has been observed that non-structural components such as light-weight partitions could significantly change floor dynamic properties. Current prediction methods do not provide a fundamental frequency manual prediction method nor finite element modeling guidance for floors with non-structural components. Current prediction methods only predict waveform peak acceleration and do not provide predictions for frequency domain response including narrowband spectral acceleration or one-third octave spectral velocity. Also, current methods are not calibrated to provide a specific level of conservatism. This research project provides (1) a fundamental frequency manual prediction method for floors with lightweight partitions; (2) an improved finite element modeling procedure for floors with light-weight partitions; (3) a procedure to predict the vibration response in narrow-band spectrum and one-third octave band spectrum which can be directly compared with vibration tolerance limits; and (4) a simplified experimental procedure to estimate the floor natural frequencies. An experimental program including four steel-framed building floors and a concrete was completed. Modal tests were performed on two of the steel-framed buildings and the concrete building using an electrodynamic shaker. Experimental modal analysis techniques were used to estimate the modal properties: natural frequencies, mode shapes, and damping ratios. Responses to walking excitation were measured several times in each tested bay for individuals walking at different walking speeds. During each test, the walker crossed the middle of the bay using a metronome to help maintain the intended cadence. The proposed method was used to predict the modal properties and responses to walking. The measurements are used to assess the precision of the proposed methods and to calibrate the prediction methods to provide a specific probability that the actual response will exceed the predicted response. Comparison of measurements and predictions shows the proposed methods are sufficiently accurate for design usage.