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Este trabalho analisa a qualidade dos combustíveis derivados de petróleo através de suas propriedades acústicas, visando assim um monitoramento contínuo e instantâneo. Analisa a variação da impedância acústica da gasolina com acréscimo de vários componentes como: tolueno, óleo diesel, querosene e álcool anidro. Os resultados obtidos mostram uma variação significativa embora não linear da impedância acústica nos combustíveis derivados de petróleo com acréscimo de tais substâncias. / This work is related with research project focused on the development of low cost and robust quality monitoring equipment and methods, suitable for application in the production of petrochemical compounds. The main objective of this work is to assess the quality of automotive gasoline through the analysis of its acoustic properties. More specifically, pure gasoline\'s acoustic impedance (defined as the product between its density and the velocity of propagation of an acoustic wave) is analyzed with respect to the addition of toluene, kerosene, ethanol and diesel fuel. Results show that the acoustic impedance is sensitive to the addition of such components, although this relation may be non-linear in some cases.

Este trabalho analisa a qualidade dos combustíveis derivados de petróleo através de suas propriedades acústicas, visando assim um monitoramento contínuo e instantâneo. Analisa a variação da impedância acústica da gasolina com acréscimo de vários componentes como: tolueno, óleo diesel, querosene e álcool anidro. Os resultados obtidos mostram uma variação significativa embora não linear da impedância acústica nos combustíveis derivados de petróleo com acréscimo de tais substâncias. / This work is related with research project focused on the development of low cost and robust quality monitoring equipment and methods, suitable for application in the production of petrochemical compounds. The main objective of this work is to assess the quality of automotive gasoline through the analysis of its acoustic properties. More specifically, pure gasoline\'s acoustic impedance (defined as the product between its density and the velocity of propagation of an acoustic wave) is analyzed with respect to the addition of toluene, kerosene, ethanol and diesel fuel. Results show that the acoustic impedance is sensitive to the addition of such components, although this relation may be non-linear in some cases.

Yes / This study presents a compact broadband wide-slot antenna with broadband left-hand circular polarization compatible with both LTE 42 and LTE 43 standards of 5G mid-band applications. The proposed antenna is fabricated on an FR4 dielectric substrate with overall dimensions of , where is the free space wavelength at the resonant frequency of the antenna. The antenna ground plane is etched to form a square radiating slot with a pair of rectangular ground stubs that are diagonally placed inside the slot. On the other side of the antenna, the feed line is loaded by horizontal and vertical stubs to improve the coupling between the feed line and the square slot. To generate a circular polarization, the feeding stubs cooperate with the pair of rectangular ground stubs to excite the radiating slot of the antenna at two different feeding points whose currents have approximately equal amplitude and 90o phase shift. The measured impedance bandwidth (BW) of the proposed wide-slot antenna is 16.2% (580 MHz along the band 3.3-3.88 GHz), while the observed axial ratio bandwidth (ARBW) is 12.2% (440 MHz in the 3.4-3.84 GHz band). The measured gain values are found to be larger than 2.5 dB along both standards of the 5G mid-band applications. / This work was supported in part by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/E022936/1, and in part by the European Union’s Horizon 2020 Research and Innovation Programme under Grant H2020-MSCA-ITN-2016 SECRET-722424.

Yes / In this paper, single-element and MIMO microstrip antenna with two pairs of unequal slits is proposed as a circularly polarized antenna with negligible back radiation for 5G mid-band handsets. The unequal pairs of slits are engraved on the antenna patch to guarantee the presence of the circular polarization (CP). The proximity-coupled feeding technique is used to excite the proposed microstrip antenna in order to provide larger antenna -10 dB bandwidth which approaches 10.8% (3.48-3.87 GHz). A novel analysis technique is proposed in this paper that demonstrates the 3D axial ratio pattern in order to generate CP in the broadside direction without affecting the structure of the ground plane which ensures weak back radiation. The 3 dB axial ratio bandwidth (ARBW) is found to be equal to 4.1% extended along the range (3.58-3.73 GHz). To make the design more compatible with the 5G mid-band handsets, the 2 × 2 MIMO structure of the proposed antenna with reduced mutual coupling (less than -20 dB) is also presented in this work. The simulation and measured results are in good agreement, and both verify the CP characteristics and the weak back radiation of the proposed antenna. / This paper is partially funded by British Council “2019 UK-China-BRI Countries Partnership Initiative Programme” with project titled “Adapting to Industry 4.0 Oriented International Education and Research Collaboration”.

A medição das propriedades viscoelásticas de líquidos por ultrassom tem sido um tema de pesquisa importante desde meados do século XX, principalmente, pela possibilidade de realizar medições em tempo real da viscosidade. O método de medição baseia-se na determinação do coeficiente de reflexão complexo (magnitude e fase) de ondas de cisalhamento refletidas da interface definida entre um sólido e uma amostra líquida. Enquanto a medição da magnitude é relativamente simples e precisa, a medição da fase é muito difícil devido à forte dependência da temperatura, que gera uma incerteza muito grande. No entanto, na medição da viscosidade em regime newtoniano somente a magnitude é requerida. Ocorre que os resultados experimentais reportados até o momento na literatura não coincidem quantitativamente com a teoria. Neste trabalho, uma nova técnica que permite determinar com boa precisão a magnitude do coeficiente de reflexão e, por conseguinte, a viscosidade de líquidos em regime newtoniano foi desenvolvida. Foi mostrado que a maioria dos líquidos testados apresentam comportamento newtoniano à frequência de trabalho de 1MHz, com exceção de alguns óleos automotivos de alta viscosidade, que possuem claramente comportamento viscoelástico. Desvios menores que 12,5% nas medições da viscosidade dinâmica de substâncias com moléculas relativamente simples, como glicerina e glicose, mostram a viabilidade da técnica. Também é proposto um novo método que permite calibrar o dispositivo de medição para monitorar a viscosidade de um líquido ou grupo de líquidos. Além disso, uma aplicação na monitoração da contaminação da água por substâncias oleosas é apresentada. / The ultrasonic measurement of viscoelastic properties of liquids has been an important research topic since the mid-twentieth century mainly due to the possibility of real-time viscosity measurements. The measurement technique is based on the determination of the complex reflection coefficient (magnitude and phase) of shear waves reflected from the solid-liquid interface. While magnitude measurement is relatively simple and precise, phase measurement is a difficult task due to strong temperature dependence that induces large errors. However, when the measurement is carried out under Newtonian regimen only the magnitude is required. Nonetheless, experimental results reported in literature until now do not agree quantitatively with the theory. In this work, it was developed a novel technique that accurately and precisely determines the reflection coefficient magnitude and, consequently, the Newtonian viscosity. Most tested liquids showed Newtonian behavior at the working frequency of 1 MHz except for some automotive oils of high viscosity, which showed an evident viscoelastic behavior. Deviations up to 12.5% in the dynamic viscosity measurement of substances with relatively simple molecules, such as glycerin and corn syrup, show the technique suitability. A calibration method of the measurement cell allowing the indirect viscosity measurement of a liquid or group of liquids is proposed. Moreover, a new application to oil-in-water contamination monitoring is presented.

In the traditional analysis of acoustic wave propagation in an ocean waveguide, it's generally assumed that acoustic properties, including density and sound speed profile at seabed are taken to be constant. However, recent experimental data provided by Hamilton~(1980)~ have shown that the sediment layer in the seabed experiences a transitional change in which the density and the sound speed vary continuously from one value at the top to another at the bottom of the layer. The objective of this study is to investigate the surface-generated ambient noise in an isovelocity waveguide with a non-homogeneous fluid sediment layer. The noise model was first proposed by Kuperman and Ingenito~(1980) in the study of surface-generated ambient noise using normal mode approach, and the model proposed by Robins (1993) in the study of the sediment layer change in which the density and the sound speed vary continuously. It is demonstrated that the noise intensity may be affected by the stratification mainly through the continuous spectrum, in that the continuous spectrum is equally important as the normal modes in the present analysis. The continuous variation of the sediment layer reduces the contrast of the interface, which in turn affects the wavenumber spectrum, particularly in the continuous spectrum region. The results show that the horizontal correlation length of the noise field increases as that of the noise random sourse increase, but the vertical correlation length of the noise field decreases as that of the noise random sourse increase.

This research experimentally shows the effect of sediment roughness characteristics on the acoustic reflection coefficient. This information is useful when trying to classify various types of sediment over an area. This research was conducted in an indoor laboratory tank at Applied Research Laboratories (ARL) at the University of Texas at Austin. A single beam echo-sounder (SBES) system was developed to project and receive a wideband (3 kHz to 30 kHz) acoustic pulse. A method was developed using the system transfer function to create a custom pulse that would minimize the dynamic range over the wide frequency band. A matched filtering and data processing algorithm was developed to analyze data over the full frequency bandwidth and over smaller frequency bands. Analysis over the smaller frequency bands showed the effect of the roughness on the reflection coefficient with respect to frequency. It was found that the reflection coefficient is significantly lower at the higher frequencies (above 20 kHz) than at the lower frequenices [sic] due to off specular scattering. It was also found that the variability of the reflection coefficient was significantly higher for the rough sediment than for the smooth sediment. / text

A microwave reflectometer is an instrument to measure a complex ratio between reflected and incident waves at an input port of a uniform transmission line that is terminated in a Device Under Test (DUT). The conventional reflectometer is formed by a four-port network with two ports connected to a microwave source and DUT, and the remaining ports coupled to a heterodyne receiver which acts as a Complex Ratio Detector (CRT). By using the heterodyne receiver technique, the two microwave signals at the input to CRT are converted in the linear manner to an Intermediate Frequency (IF) of hundreds of kHz where they are processed using digital means. As the ratio of two original microwave signals has to be preserved at IF, a very advanced electronic circuitry is required to accomplish the linear conversion process. This complicated electronic circuitry leads to a large size of the conventional reflectometer and its high price tag. Many applications require compact-size and low-cost reflectometers. They can be built using N-port networks, with N being greater than 5, equipped only in scalar (power) detectors. The thesis describes the concept of a multi-port reflectometer which determines the complex reflection coefficient of DUT with the use of scalar detectors instead of the complex ratio detector. It is shown that this device can be designed using an assembly of linear circuits in the form of quadrature (Q) and/or divider (D) hybrids. Assuming ideal operation of these components, it is shown that the reflection coefficient of DUT can be determined using simple mathematical operations on the power values measured by scalar detectors. Alternatively, it can be obtained from the intersection of power circles in a complex reflection coefficient plane. These simple mathematical expressions can be used to obtain an approximate real-time operation of reflectometer. For more accurate results, the multi-port has to be calibrated using calibration standards. A review of full calibration methods for a multi-port reflectometer is presented. In order to obtain wideband performance, the multi-port reflectometer has to be formed by components all having wideband performance. To obtain its low manufacturing cost, these components should preferably be of planar format and lead to a full integration of reflectometer. The thesis investigates a variety of planar couplers and dividers which can offer wideband performances. However, not all of them can lead to a fully integrated multi-port reflectometer. In order to overcome this shortfall, a multilayer microstrip-slot technique is proposed and investigated to obtain wideband components that can lead to a full integration of multi-port reflectometer. It is demonstrated that through the use of multilayer microstrip-slot technique, ultra wideband microwave 3-dB couplers and two-way dividers of in-phase or out-of-phase type can be designed. It is shown that the chosen configurations of dividers are compatible with the 3-dB couplers so that a fully integrated reflectometer can be formed. This compatibility is accomplished through the use of suitably designed microstrip to slotline transitions. An attractive feature of the designed couplers and dividers is that they are of sub-wavelength size and thus are very compact. A fine operation of these components is demonstrated via full electromagnetic wave simulations and experimental tests over and ultra wide frequency band of 3.1 to 10.6 GHz. Rogers substrate RO4003 featuring a relative dielectric constant of 3.38 and a loss tangent of 0.0027 is chosen as a microwave substrate for the design of these components. The design and analysis are carried out with the commercially available full EM simulator CST Microwave Studio while the experimental tests are done with the Vector Network Analyser, HP8510C. By using these components, an ultra wideband complex ratio measuring unit (CRMU), which is the heart of a multi-port reflectometer, is designed. This CRMU is fully integrated and of compact size. Its operation over an ultra wide frequency band is demonstrated via simulations. A particular attention is paid to its real-time mode of operation. Using this mode of operation, the complex ratio of two waves can be displayed on an oscilloscope using an analog electronics performing simple mathematical operations on the measured powers by detectors. While discussing the operation of CRMU, the attention is paid to the location and spacing of power circles centres (q-points) which are used for geometrical interpretation of operation of this device. Good operation of CRMU in this approximate operation mode indicates that the device will operate very well when it is fully calibrated. For simulations of CRMU, CST Microwave Studio, Agilent’s Advanced Design System (ADS) and MATLAB software are applied. Having accomplished the successful design of CRMU, the last step includes the formation of a fully integrated multi-port reflectometer. To this purpose an extra circuitry including multilayer microstrip-slot 3-dB couplers is added to CRMU. The purpose of this additional circuitry is to reroute the incident and reflected signals from the DUT to the input ports of CRMU. A few configurations of multi-port relectometer formed by multilayer microstrip-slot couplers or dividers are investigated via simulations with respect to real-time mode of operation. Then, the best performing configuration is selected for the final development. The device is manufactured in Rogers RO4003 substrate. Its S-parameters are measured with HP8510C analyser and compared with the simulated values. Having obtained a relatively good agreement between the simulated and measured results, the device is calibrated using multiple calibration standards. Its operation is verified for selected DUTs by comparing the measured reflection coeffcients with those obtained using the conventional VNA (HP8510C) over an ultra wide frequency band. A relatively good agreement is obtained between the two sets of measured results. The obtained results prove that the multilayer microstrip-slot technology can successfully be used for the development of a compact low-cost and fully integrated UWB multi-port reflectometer. Because of its compact size and good electrical performance, this device can be used in many microwave sub-systems offering a limited space for implementation of microwave measurements. The thesis shows that the accomplished multi-port device can also be used to build UWB communication transceivers. The concept of such UWB transceivers is addressed in the final sections of this thesis.

A medição das propriedades viscoelásticas de líquidos por ultrassom tem sido um tema de pesquisa importante desde meados do século XX, principalmente, pela possibilidade de realizar medições em tempo real da viscosidade. O método de medição baseia-se na determinação do coeficiente de reflexão complexo (magnitude e fase) de ondas de cisalhamento refletidas da interface definida entre um sólido e uma amostra líquida. Enquanto a medição da magnitude é relativamente simples e precisa, a medição da fase é muito difícil devido à forte dependência da temperatura, que gera uma incerteza muito grande. No entanto, na medição da viscosidade em regime newtoniano somente a magnitude é requerida. Ocorre que os resultados experimentais reportados até o momento na literatura não coincidem quantitativamente com a teoria. Neste trabalho, uma nova técnica que permite determinar com boa precisão a magnitude do coeficiente de reflexão e, por conseguinte, a viscosidade de líquidos em regime newtoniano foi desenvolvida. Foi mostrado que a maioria dos líquidos testados apresentam comportamento newtoniano à frequência de trabalho de 1MHz, com exceção de alguns óleos automotivos de alta viscosidade, que possuem claramente comportamento viscoelástico. Desvios menores que 12,5% nas medições da viscosidade dinâmica de substâncias com moléculas relativamente simples, como glicerina e glicose, mostram a viabilidade da técnica. Também é proposto um novo método que permite calibrar o dispositivo de medição para monitorar a viscosidade de um líquido ou grupo de líquidos. Além disso, uma aplicação na monitoração da contaminação da água por substâncias oleosas é apresentada. / The ultrasonic measurement of viscoelastic properties of liquids has been an important research topic since the mid-twentieth century mainly due to the possibility of real-time viscosity measurements. The measurement technique is based on the determination of the complex reflection coefficient (magnitude and phase) of shear waves reflected from the solid-liquid interface. While magnitude measurement is relatively simple and precise, phase measurement is a difficult task due to strong temperature dependence that induces large errors. However, when the measurement is carried out under Newtonian regimen only the magnitude is required. Nonetheless, experimental results reported in literature until now do not agree quantitatively with the theory. In this work, it was developed a novel technique that accurately and precisely determines the reflection coefficient magnitude and, consequently, the Newtonian viscosity. Most tested liquids showed Newtonian behavior at the working frequency of 1 MHz except for some automotive oils of high viscosity, which showed an evident viscoelastic behavior. Deviations up to 12.5% in the dynamic viscosity measurement of substances with relatively simple molecules, such as glycerin and corn syrup, show the technique suitability. A calibration method of the measurement cell allowing the indirect viscosity measurement of a liquid or group of liquids is proposed. Moreover, a new application to oil-in-water contamination monitoring is presented.