Gas turbine prime movers fuelled by LNG as a future alternative for sustainable power in marine propulsion: current emission policy assessment and exhaust quality evaluation

In recent years, climate change has dramatically shown its effects in terms of fluctuations of temperatures because of increased global warming due to greenhouse gas emissions. Pollution control is strongly linked to atmospheric acidification and contaminants in combustion exhausts. In such a contest, marine propulsion is actually a key player that is accounting for a substantial contribution to pollution. Kyoto protocol’s obligations established decarbonisation as a compulsory commitment and contaminant constraints are defined by current emission policy and regulations both on a global and on a regional basis. In this paper, a study is carried out in order to develop a framework for current emission policy and assessment of exhausts due to constraints imposed on fuel choice. Gas fuelled marine propulsion, implemented through state-of-the-art GT areoderivative prime movers, powered by LNG, is analysed from the environmental point of view. The pollutant emissions from various size GT models are evaluated through both GT datasheets and commercial (as well as self-coded) software, in order to assess the validity of LNG as an alternative fuel option for future sustainable marine applications

Feasibility of mini combined cycles for naval applications

The objective of energy production with low environmental impact will have, in the near future, high potential of development also for naval applications. The containment of pollutant emissions can be achieved by the combined use of an innovative mini gas-steam combined cycle with thermal energy cogeneration to feed the ship thermal utilities, in place of the current Diesel engine application, and liquefied natural gas as fuel (LNG). The present work is focused on the definition of the architecture of the plant, by selecting optimal distribution of pressure and temperature and repartition of power between Gas Turbine (GT), Steam Turbine (ST) and thermal utilities, as well as on the choice and sizing of the individual components. The main purpose is the definition of a compact, high efficiency, system. The proposed basic mini-cycle ranges from 2 MW to 10 MW electric power. Thanks to the combined heat and power cogeneration plant adopted, for an overall electrical efficiency of about 30%, a total return (thermal + electricity) of about 75% can be achieved. An example of plant providing large power, in a partially modular arrangement is also proposed

Torakalna hernijacija kralješnične moždine

Herniation of the spinal cord through a dural defect is a rather rare deformity and very easily misdiagnosed as retromedullary occult intraspinal arachnoid cyst or meningocele. The possible origin of the dural defect can be traumatic, iatrogenic or unknown, so in these cases, congenital with great probability. On the thoracal part of the spinal column it shows a rather characteristic and misleading appearance. The anomaly leads to progressive Brown-Sequard syndrome, and the case history can be extremely long. Surgical repair of the dural defect results in improvement, or even complete recovery, if performed in time. These are the facts that emphasize the importance of early diagnosis.Hernijacija kralježnične moždine kroz duralne defekte prilično je rijetka deformacija koja se vrlo lako pogrešno dijagnosticira kao retromedularna okultna intraspinalna arahnoidna cista ili kao meningokela. Uzrok duralnog defekta može biti traumatski, jatrogeni ili nepoznat, a u ovim je slučajevima vrlo vjerojatno prirođen. Torakalni dio kralježnice pokazuje prilično karakterističan izgled, no koji može zavarati. Poremećaj uzrokuje pojavu progresivnog Brown-Séquardova sindroma, a anamneza može biti izrazito dugotrajna. Ako se provede na vrijeme, kirurško zatvaranje duralnog defekta dovodi do poboljšanja, pa čak i do potpunog oporavka, .to upućuje na važnost rane dijagnoze

Effects of different tooth bleaching systems on the roughness and superficial morphology of enamel and a restorative composite resin

Objetivo: Avaliar as alterações de rugosidade e morfologia superficial do esmalte e da resina composta após diferentes técnicas de clareamento dental. Material e método: incisivos bovinos íntegros foram selecionados, sendo que cavidades padronizadas foram confeccionadas na face vestibular, as quais foram restauradas com resina composta. Os dentes foram distribuídos em grupos, de acordo com o tratamento proposto: G1-clareamento com peróxido de carbamida (PC) 10%; G2 - clareamento com peróxido de hidrogênio (PH) a 38%; G3- clareamento com PH a 38% associado à foto-ativação com LED. Para G1, o agente clareador foi aplicado por 8 horas diárias durante 21 dias. Para\ud G2 e G3, foram realizadas 3 sessões de clareamento, caracterizadas por 3 aplicações do gel clareador por 15 minutos, com intervalos de 7 dias entre as sessões, sendo que em G3 o gel clareador foi ativado com LED (470nm) por 6 minutos. As superfícies do esmalte e da resina composta foram avaliadas antes e após o procedimento clareador através de um rugosímetro e de um microscópio de força atômica. Resultados: Os resultados demonstraram diferença significante da rugosidade do esmalte antes e após o clareamento apenas para G1, em relação ao controle (Wilcoxon, p<0,05). Para a resina composta, nenhum dos grupos apresentou diferença estatística em relação ao controle (Mann-Whitney, p>0,05). Conclusão: O aumento da rugosidade do esmalte aconteceu apenas quando o clareamento foi realizado através da aplicação de um gel com 10% de PC. Nenhum dos procedimentos clareadores avaliados nesta pesquisa interferiram na rugosidade e morfologia da resina composta.CNPq (135181/2010-0; 30129/2010-1

Thermal Infrared Radiometric Calibration of the Entire Landsat 4, 5, and 7 Archive (1982-2010)

Landsat's continuing record of the thermal state of the earth's surface represents the only long term (1982 to the present) global record with spatial scales appropriate for human scale studies (i.e., tens of meters). Temperature drives many of the physical and biological processes that impact the global and local environment. As our knowledge of, and interest in, the role of temperature on these processes have grown, the value of Landsat data to monitor trends and process has also grown. The value of the Landsat thermal data archive will continue to grow as we develop more effective ways to study the long term processes and trends affecting the planet. However, in order to take proper advantage of the thermal data, we need to be able to convert the data to surface temperatures. A critical step in this process is to have the entire archive completely and consistently calibrated into absolute radiance so that it can be atmospherically compensated to surface leaving radiance and then to surface radiometric temperature. This paper addresses the methods and procedures that have been used to perform the radiometric calibration of the earliest sizable thermal data set in the archive (Landsat 4 data). The completion of this effort along with the updated calibration of the earlier (1985 1999) Landsat 5 data, also reported here, concludes a comprehensive calibration of the Landsat thermal archive of data from 1982 to the presen

Observations and Recommendations for the Calibration of Landsat 8 OLI and Sentinel 2 MSI for Improved Data Interoperability

Combining data from multiple sensors into a single seamless time series, also known as data interoperability, has the potential for unlocking new understanding of how the Earth functions as a system. However, our ability to produce these advanced data sets is hampered by the differences in design and function of the various optical remote-sensing satellite systems. A key factor is the impact that calibration of these instruments has on data interoperability. To address this issue, a workshop with a panel of experts was convened in conjunction with the Pecora 20 conference to focus on data interoperability between Landsat and the Sentinel 2 sensors. Four major areas of recommendation were the outcome of the workshop. The first was to improve communications between satellite agencies and the remote-sensing community. The second was to adopt a collections-based approach to processing the data. As expected, a third recommendation was to improve calibration methodologies in several specific areas. Lastly, and the most ambitious of the four, was to develop a comprehensive process for validating surface reflectance products produced from the data sets. Collectively, these recommendations have significant potential for improving satellite sensor calibration in a focused manner that can directly catalyze efforts to develop data that are closer to being seamlessly interoperable

Raman and infrared phonon features in a designed cubic polymorph of CaTa2O6

At room temperature, calcium tantalite (CaTa2O6) is known to exhibit three stable polymorphs, depending on the crystal growth conditions. In this work, the laser-heated pedestal growth method was used to obtain CaTa2O6 single crystal fibers in its quenched (ordered) cubic polymorph, attractive for optical applications. X-ray diffraction, Raman scattering and infrared spectroscopy showed that the fibers grew into the centrosymmetrical Pm3 space group. The growth axis was determined as [001]. The cylindrical fibers (20 mm long and 400 μm wide) showed good optical quality, without cracks or striations, but with small facets, parallel to crystal edges or to in-plane edge bicetrices. A comprehensive set of the optical phonons for this cubic structure was obtained, consisting of 13 (of 16 foreseen) triply degenerate polar phonons, and all the 21 predicted Raman modes. By using special scattering geometries, the Raman bands were attributed to their corresponding irreducible representations. In general, the phonons showed rather large damping constants, which do not compromise the designed optical applications in compact lasers but increase the losses in the microwave range, even though the dielectric response is quite adequate for microwave applications. Quenched defects and crystal polymorphism can be at the origin of the large phonon damping.CNPqFINEPFAPEMIGFAPES

Mastering Cryogenic Propellants

No abstract availabl

Modulation of spinal excitability following neuromuscular electrical stimulation superimposed to voluntary contraction

Purpose. Neuromuscular electrical stimulation (NMES) superimposed on voluntary muscle contraction has been recently shown as an innovative training modality within sport and rehabilitation, but its effects on the neuromuscular system are still unclear. The aim of this study was to investigate acute responses in spinal excitability, as measured by the Hoffmann (H) reflex, and in maximal voluntary contraction (MVIC) following NMES superimposed to voluntary isometric contractions (NMES+ISO) compared to passive NMES only and to voluntary isometric contractions only (ISO). Method. Fifteen young adults were required to maintain an ankle plantar-flexor torque of 20% MVC for 20 repetitions during each experimental condition (NMES+ISO, NMES and ISO). Surface electromyography was used to record peak-to-peak Hreflex and motor waves following percutaneous stimulation of the posterior tibial nerve in the dominant limb. An isokinetic dynamometer was used to assess maximal voluntary contraction output of the ankle plantar flexor muscles. Results. H-reflex amplitude was increased by 4.5% after the NMES+ISO condition (p < 0.05), while passive NMES and ISO conditions showed a decrease by 7.8% (p < 0.05) and no change in reflex responses, respectively. There was no change in amplitude of maximal motor wave and in MVIC torque during each experimental condition. Conclusion. The reported facilitation of spinal excitability following NMES+ISO could be due to a combination of greater motor neuronal and corticospinal excitability, thus suggesting that NMES superimposed onto isometric voluntary contractions may provide a more effective neuromuscular stimulus and, hence, training modality compared to NMES alone