Tachoastrometry: astrometry with radial velocities

Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky. By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured. We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 \ms, which corresponds to a separation between the two components at the time of the observations of 18 $\pm2$ milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record pairs of spectra rotated by 180 degrees, thus reducing systematic effects. We compute and provide the function expressing the shift of the centroid of a seeing-limited image in the presence of a narrow slit.The proposed technique is simple to use and our test shows that it is amenable for deriving astrometry with milli-arcsecond accuracy or better, beyond the diffraction limit of the telescope. The technique can be further improved by using simple devices to simultaneously record the spectra with 180 degrees angles.With tachoastrometry, radial velocities and astrometric positions can be measured simultaneously for many double line system binaries in an easy way. The method is not limited to binary stars, but can be applied to any astrophysical configuration in which spectral lines are generated by separate (non-rotational symmetric) regions.Comment: Accepted for publication in A&

COMPARATIVE ANALYSES OF THE THERMAL PERFORMANCE OF REFRIGERANTS R134A, R245fa, R407C AND R600a DURING FLOW BOILING IN A MICROCHANNELS HEAT SINK

A comparative study of the performance of of refrigerants R134a, R407C, R245fa and R600a during flow boiling was performed for a 123x494 µm2 heat sink composed of 50 parallel rectangular microchannels. Heat transfer experimental results for heat fluxes up to 310 kW/m2, mass velocities from 300 to 800 kg/(m2 s), liquid subcoolings of 5 and 10 °C and saturation temperature close to 30 ºC were obtained. Global heat transfer coefficients (footprint) up to 10 kW/(m2 °C) were found. The liquid superheating necessary for the onset of nucleate boiling (ONB) was also characterized, and the fluids R245fa and R407C presented the highest and lowest, respectively, superheating to trigger the boiling process. Moreover, for a fixed averaged vapor quality, the average effective heat transfer coefficient increases with increasing mass velocity and liquid subcooling. The refrigerants R600a and R407C presented the highest and the lowest heat transfer coefficients, respectively. Five heat transfer predictive methods from literature provided accurate predictions of the data for R134a, R245fa and R600a, capturing most of the data trends. No one method provided accurate predictions of the heat transfer coefficient data of R407C

Transient Charging and Discharging of Spin-polarized Electrons in a Quantum Dot

We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance (TMR) are calculated using both nonequilibrium Green function and master equation techniques. Both parallel and antiparallel leads' magnetization alignments are analyzed. Our main findings are: a dynamical spin accumulation that changes sign in time, a short-lived pulse of spin polarized current in the emitter lead (but not in the collector lead), and a dynamical TMR that develops negative values in the transient regime. We also observe that the intra-dot Coulomb interaction can enhance even further the negative values of the TMR.Comment: 7 pages, 6 figures. Typos corrections corresponding to the published versio

Implementar o modelo de produção Lean na ITV para promover sistemas eco eficientes

O modelo de produção Lean é um modelo de organização da produção focado no cliente e na entrega atempada de produtos eliminando os desperdícios (i.e. atividades que não acrescentam valor ao produto) e respeitando as pessoas e o ambiente para reduzir os custos e aumentar a produtividade. Para o conseguir, este modelo recorre a princípios e ferramentas com objetivo de melhorar os processos e os fluxos de materiais, de informação e de pessoas. Nesta procura de melhoria é obrigatório reduzir os consumos de água, energia, matérias-primas e emissão de substâncias tóxicas que vão contaminar o solo, ar e água. Evidencia-se assim, neste artigo, esta relação entre o modelo de produção Lean e a eco-eficiência dos sistemas de produção, designada na literatura anglo-saxónica como Lean-Green.The Lean production model is a model of production organization focused on the customer and timely delivery of products, eliminating waste (e.g activities that do not add value to the product) and respecting people and the environment to reduce costs and increase productivity. To achieve this, this model uses principles and tools in order to improve the processes and flow of materials, information and people. In this quest for improvement it is mandatory to reduce the consumption of water, energy, raw materials and emission of toxic substances that will contaminate the soil, air and water. In this article, emphasis is given on the relationship between the model of lean manufacturing and ecoefficiency of production systems, known in the literature as Lean-Green

Remote ischemic preconditioning in patients with intermittent claudication

OBJECTIVE: Remote ischemic preconditioning (RIPC) is a phenomenon in which a short period of sub-lethal ischemia in one organ protects against subsequent bouts of ischemia in another organ. We hypothesized that RIPC in patients with intermittent claudication would increase muscle tissue resistance to ischemia, thereby resulting in an increased ability to walk. METHODS: In a claudication clinic, 52 ambulatory patients who presented with complaints of intermittent claudication in the lower limbs associated with an absent or reduced arterial pulse in the symptomatic limb and/or an ankle-brachial index <0.90 were recruited for this study. The patients were randomly divided into three groups (A, B and C). All of the patients underwent two tests on a treadmill according to the Gardener protocol. Group A was tested first without RIPC. Group A was subjected to RIPC prior to the second treadmill test. Group B was subjected to RIPC prior to the first treadmill test and then was subjected to a treadmill test without RIPC. In Group C (control group), both treadmill tests were performed without RIPC. The first and second tests were conducted seven days apart. Brazilian Clinical Trials: RBR-7TF6TM. RESULTS: Group A showed a significant increase in the initial claudication distance in the second test compared to the first test. CONCLUSION: RIPC increased the initial claudication distance in patients with intermittent claudication; however, RIPC did not affect the total walking distance of the patients

Lean thinking contributions for Industry 4.0: a systematic literature review

Lean Thinking has successfully challenged mass production practices, providing greater flexibility in production systems and processes, resulting in "leaner" products and supply chains, i.e., with less waste. More recently, the term Industry 4.0 emerged. It was first used in Germany in 2011 to refer to the 4th industrial revolution. It aims to connect the physical and virtual worlds in industrial production and has become increasingly popular with the many opportunities and business models that can be consolidated through new technologies. With such automation associated with Industry 4.0, questions arise about the interoperability between the two approaches and the role of Lean in this ongoing industrial revolution. Therefore, a systematic literature review was carried out in order to answer the research questions, and to identify the role of Lean in this scenario. The review was conducted for the period from 2011 to 2018 and resulted in a total of 26 articles being analyzed. This paper's focus is the effect of Lean Thinking as a facilitator, within the scope of Industry 4.0. It is also clear that this is an emerging research area, with most of the selected studies published between 2017 and 2018. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.This work has been supported by FCT - Fundacao para a Ciencia e Tecnologia within the Project Scope: UID/CEC/00319/2019

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