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Carbon nanotubes (CNTs) were dispersed into polyvinyl acetate (PVAc ) adhesive cured by radio frequency (RF) to investigate their loading effects on PVAc adhesive curing time and lap shear bond strength performance. Main factors are CNT loading (0.08, 0.25 and 0.41%), RF curing time (15, 30, 45, 60 seconds), and clamping pressure (100, 160, and 240 psi). Experimental results indicated that CNT loading had significant effects on PVAc curing time and lap shear bond strength. Specifically, single lap shear joints bonded with 0.41% CNT loading adhesive had significantly higher lap shear bond strengths than one with PVAc only (0% CNT loading). The curing time of PVAc dispersed with a 41% CNT loading (15 seconds) was 30 seconds shorter than the one with a 0% CNT loading (45 seconds).

No description available.

No description available.

No description available.

[pt] A crescente competitividade entre cadeias de suprimentos, proveniente de um cenário globalizado onde o mercado exige um forte desempenho das cadeias produtivas e flexibilidade com relação à qualidade, prazos e custos dos produtos, acentua a importância da participação da logística como um agente fomentador de inteligência estratégica entre as diversas disciplinas dos processos industriais. A necessidade de obtenção e gerenciamento de um fluxo ideal de informações e ações dentro dos atuais processos produtivos de uma SC - Supply Chain (cadeia de suprimentos) para responder de forma competitiva e segura às demandas vindas deste mercado, aliada ao desenvolvimento nos últimos anos da tecnologia sem fio (wireless) Radio Frequency Identification (Identificação por Rádio Freqüência), abre grandes oportunidades à aplicação do RFID na logística. Neste trabalho pretendeu-se dar continuidade ao trabalho intitulado Aplicações de tecnologias sem fio em operações logísticas, divulgado em Figueiredo (2004). Assim, de forma a complementar o trabalho de Figueiredo (2004), o propósito desta dissertação é dar maior visibilidade sobre o uso da tecnologia de RFID com aplicação voltada a processos logísticos, de forma a promover maior compreensão dos impactos desta tecnologia nas diversas aplicações industriais. Para tal, o presente trabalho analisa diversos estudos de casos reais abrangendo empresas que utilizam esta tecnologia, ou que estão em fase piloto de sua utilização no Brasil. Com base nos resultados de estudos de casos realizados pelo autor, puderam ser analisados alguns impactos nos usos e oportunidades do RFID nos processos logísticos. / [en] The growing competitiveness among supply chains, originated from a global scenery where the market demands a strong performance and flexibility regarding quality, periods and costs of the products from the productive chains, emphasizes the importance of the logistic participation as a promoting agent of strategic intelligence among the several disciplines of the industrial processes. The necessity of obtaining an efficient management system of information flow and actions inside the current productive processes of a SC - (Supply Chain) to answer in a safe and competitive way to the demands coming from this market, allied with the development of the wireless technology opens great opportunities to apply RFID (Radio Frequency Identification) technology to logistics. This work intends to continue the research conducted in Figueiredo (2004) entitled Aplicações de tecnologias sem fio em operações logísticas. Therefore, the main goal of this master dissertation is to give more visibility concerning the use of the RFID technology applied to logistic processes in a way to promote a better comprehension of the impacts of this technology in different industrial applications. In order to achieve its goal, this dissertation analyses different case studies with companies that use this technology or are in pilot phase of its use in Brazil. Regarding the results of case studies conducted by the author it was possible to analyze some impacts in the uses and opportunities of RFID in the logistics processes.

This research took place in 3 stages. In the first stage, lignin graphene (LG) was synthesized using a catalytic thermal conversion process. In stage 2, the time and temperature correlations for polyvinyl acetate (PVAc) and phenol resorcinol formaldehyde (PRF) adhesives were found and PRF showed stronger correlation when doped with carbon nanomaterials. Stage 3 evaluated the effect of the nanomaterials on radio frequency (RF) heating time and adhesive strength. It was found that all versions of the PRF adhesive resulted in higher shear strength values when cured in room temperature for 24 hours or in an oven at 170 °F for 30 minutes. The combination of PRF + 0.5 % LG and 120 s RF heating resulted in significantly higher block shear strengths when compared to the other RF heating durations. Pine lumber was selected as it is the single most important commercial/structural species in North America, by volume. A substantial portion of pine is directed to glue-laminated timber and cross-laminated timber. Both industries use or can use RF curing and as such both may benefit from improvements developed herein.

Radio astronomy synthesis imaging arrays are composed of many parabolic reflector antennas. These antennas are designed to be extremely sensitive to detect faint emissions from astronomical sources. Unfortunately, this also makes them susceptible to radio frequency interference (RFI) from man made sources such as orbiting satellites. The radio astronomy research group at Brigham Young University (BYU) is investigating methods to mitigate the effects of RFI in radio astronomy synthesis imaging. Though real-time RFI mitigation has been demonstrated for a large single dish telescope, for synthesis imaging arrays our prior work has consisted solely of algorithm development and computer simulations. To test our algorithms on experimental data we need an image synthesis array at BYU. The primary contribution of this Master's thesis is the design and construction of a working image synthesis array on the roof of the Clyde Building at BYU. This thesis describes the design of the antenna placement for the synthesis array. Antenna placement is the primary factor for determining image quality since the placement dictates the shape of the synthesized beam. Simulations were performed, prior to the array's construction, to predict the quality of images from the array. Another contribution of this thesis is signal processing code to generate correlations of the signals from the antennas. Code was written to calibrate measured data and generate an image from the correlations. Code was also written to steer the antennas and track astronomical phenomena. The performance of the array is evaluated in this thesis. The culmination of this thesis is a radio image of the supernova remnant Cassiopeia A. This thesis concludes with simulations of an RFI mitigation experiment that can be performed with the new array (pending certain improvements to the array).

Failure of a machine can lead to production downtime and significant financial losses. Condition monitoring is implemented to avoid such downtime and devices can be used to collect data used for monitoring machine health. Vibration data is the most common type of data used for predicting machine failure. To reduce the need for hazardous cables, such devices are often battery-operated, but this can decrease monitoring device lifespans to less than 3 years, if non-rechargeable batteries are used. This thesis first proposes a design framework for implementing radio frequency energy harvesting (RFEH) at a network level. All of the necessary inputs and parameters to ensure the successful implementation of RFEH for a wireless sensor network are explored. A second design framework is then proposed for using RFEH as a source of energy to power devices for condition monitoring. This includes a power analysis of all device components, as well as the design details for an implementation of wireless power transfer using a wireless transmitter and receiver. A comparison of different types of energy sources for the device is given, followed by a case study, using commercially-available components. A simulation is used to analyze the trade-offs for different values of RFEH parameters, trading off the total cost of implementation with the system's lifetime, based on total energy consumed.

This thesis work is mainly focused on studying RF performance degradation of a low noise amplifier (LNA) circuit due to hot carrier effect (HCE) in both the weak and strong inversion regions. Since the figures of merit for the RF circuit characterization are gain, noise figure, input, and output matching, the LNA RF performance drift is evaluated in a Cadence SpectreRF simulator subject to these features. This thesis presents hot carrier induced degradation results of an LNA to show that the HCE phenomenon is one of the serious reliability issues in the aggressively scaled RF CMOS design, especially for long-term operation of these devices. The predicted degradation from simulation results can be used design reliable CMOS RF circuits.