Multiple classical limits in relativistic and nonrelativistic quantum mechanics

The existence of a classical limit describing interacting particles in a second-quantized theory of identical particles with bosonic symmetry is proved. This limit exists in addition to a previously established classical limit with a classical field behavior, showing that the limit $\hbar \to 0$ of the theory is not unique. An analogous result is valid for a free massive scalar field: two distinct classical limits are proved to exist, describing a system of particles or a classical field. The introduction of local operators in order to represent kinematical properties of interest is shown to break the permutation symmetry under some localizability conditions, allowing the study of individual particle properties.Comment: 13 page

The History of the Portuguese Aviation - A Summary

This article is intended as a summary of a new area of study on the History of the Portuguese Aeronautics and Aerospace and addresses issues such as: the forthcoming of the aircraft at Portugal, its military and civilian use; the scope of early days concerning Portuguese intercontinental flights and their authors; the development of air navigation devices by Portuguese inventors in the 1920s and 30s; the Aeronautics industry and the need to develop expertise in Aeronautical/Aerospace Engineering in Portugal during the centuries XX and XXI.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

First Aerial South Atlantic Night Crossing

The history of the transatlantic flights began in 1919 when Albert C. Read’s team flew between Newfoundland and Lisbon, with a stopover at Azores, for fuel and repairs. The flight was made following a chain of 60 U.S. warships in order to guide it along its route and to provide assistance if needed. Two weeks later, John Alcock and Sir Arthur Whitten Brown made the first nonstop transatlantic flight from Newfoundland to County Galway, Ireland, covering more than 3000 km in just 16 hours of flight. In 1922, Gago Coutinho and Sacadura Cabral crossed the South Atlantic Ocean by air, for the first time using only internal means of navigation: a modified sextant and a course corrector; both devices proved its effectiveness. The Portuguese Aeronautics rejoiced auspicious days that time, with its aviation pioneers trying consecutively to reach more distant places along intercontinental flights. Several Around-the-World Flight Attempts were made in 1924: United States, England, France, Portugal, Argentina and Italy. However the circumnavigation purpose was only officially confirmed before the general public, when a considerable flying progress was achieved. In 1923, Gago Coutinho and Sacadura Cabral were contemplating to perform an Around the World Flight, a dream pursued also by Sarmento de Beires in 1924 and 1927. In 1927 and by following the knowledge obtained by Coutinho and Cabral, four Portuguese Airmen started an Around the World Flight Attempt in a mission that ended with seaplane sunk at the Ocean; however this mission was renamed after the seaplane loss and became known in the World as the First Aerial South Atlantic Night Crossing. For the first time in history, during the night of 16 to 17 March 1927, a Portuguese crew flew 2595 km over the Atlantic Ocean from Guinea, Africa to Fernando de Noronha Island, Brazil. The flight was made only by astronomical processes navigation resources that proved again to be absolutely feasible and trustworthy, regardless day or night lighting conditions.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Gago Coutinho and the Scientific Navigation

Gago Coutinho, jointly with another Portuguese aerial navigator, managed to perform the First Flight from Europe to the South Atlantic in 1922, a Journey exclusively guided by internal means of navigation. Despite Coutinho being a person with multi-purpose activity on several areas of knowledge, he became known and glorified in the World in 1922, as an air navigator, a position that he achieved due to an aerial navigation device that he also had invented. Coutinho developed a new sextant model that could be used to measure the altitude of a star (when flying overseas) without the need of the sea horizon. This new device was called precision sextant and was provided with an artificial horizon line defined with the help of a water bubble. Due to his knowledge of Navigation, Astronomy, Geography and Mathematics, Coutinho received from the Portuguese King D. Carlos I, several assignments at Africa and Asia. Gago Coutinho received several important official medals and prizes, including the Ph.D. Honoris Causa from the Universities of Lisbon and Oporto and authored several scientific publications. Coutinho received the distinct position of Admiral of the Portuguese Navy in 1958 and died in the following year.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

The First Aerial Journey from Portugal to Macau

On 1920, Brito Pais and Sarmento Beires tried an unsuccessful flight attempt from Amadora, Lisbon to Madeira Island onboard an airplane Breguet XIV A2, named “Cavaleiro Negro”. Despite the scarce means of navigation both navigators managed to reach Madeira, which failed to land due to dense fog. On their way back after 8 hours of flight time, they alight at the Atlantic Ocean for lack of fuel and were rescued at about 500 km from Lisbon. On 1922, Gago Coutinho and Sacadura Cabral conducted the First Aerial Cross of the South Atlantic, flying from Lisbon to Rio de Janeiro. The Portuguese Aeronautics rejoiced auspicious days that time, with its aviation pioneers trying consecutively to reach more distant places along intercontinental flights. On 1923, Gago Coutinho and Sacadura Cabral were contemplating to perform an Around the World Flight. However, Sacadura died in 1924, while piloting an airplane acquired for the circumnavigation voyage. Later on 1924 the pilots Brito Pais and Sarmento Beires idealized the conducting of an aerial flight from Lisbon to Macau as an aspiration for a future Portuguese Around the World Flight attempt: on 7 April 1924, those pilots departed from Vila Nova de Milfontes in a Breguet XIV Bn2 airplane, starting their Journey to Macau. During a flight stage on 7 May an engine failure forced them to crash the airplane at India; on 30 May, both pilots managed to continue the Voyage in a De Havilland DH9 aircraft before being forced to end their attempt in 20 June in flying over Macau. A typhoon hindered their efforts to land and the airplane was crash landed in Chinese Territory about 800 meters from the Hong Kong Border. On 25 June 1924, they were shuttled back to Macau by boat. Brito Pais, Sarmento Beires and Manuel Gouveia returned to Portugal, via North America, visiting several Portugueses nuclei at China, Japan, United States and England. They went to Portugal on 9 September, after having flown a total of 16,760 km in 117:41 h facing often extremely adverse atmospheric conditions, sandstorms and inaccurate navigation maps.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Sacadura Cabral and the Dawn of Portuguese Aviation

Sacadura Cabral was one of the two Portuguese navigators that crossed by air the South Atlantic in the beginning of the 20th century. From 1901 to 1915 Sacadura was at Mozambique and Angola where he developed geodetic and geographical missions of the greatest importance for Portuguese interest at Africa. With the Great World War requirements as a Navy Officer with 34 years old he decided to serve Portugal at the Aviation. In 1915 he went to France and obtained its pilot license. In 1916 Sacadura returned to Portugal and begun its instructor pilot career. He developed the “path corrector” which he created to compensate the drift caused by wind. In 1922 Sacadura made the First Air cross from Europe to South Atlantic. In 1923 he proposes himself to make an attempt to the First Air Circumnavigation Journey. He developed all its possible efforts to initiate this journey in March of 1924; however some delays had forced him to postpone the journey. Sacadura received important official medals and prizes, including the PhD Honoris Causa from the Universities of Lisbon and Oporto. In 1924 he died before he could carry out its Circumnavigation Air Journey.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Experimental Study of Two Impinging Jets Aligned With a Crossflow

Laser Doppler measurements provide information on the flowfield created by twin impinging jets aligned with a low velocity crossflow. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 104, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = Vj/Uo of 22.5, and an inter-jet spacing of S = 6D. The results show a large penetration of the first (upstream) jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that is most relevant for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Description of a Eulerian–Lagrangian Approach for the Modeling of Cooling Water Droplets

The present paper describes a tool developed in-house for the modeling of free-falling water droplet cooling processes. A two-way coupling model is employed to account for the interactions between the droplets and the carrier fluid, following a Eulerian-Lagrangian approach. In addition, a stochastic separated flow technique is employed, involving random sampling of the fluctuating fluid velocity. In physical modeling, two empirical correlations are considered for determining the heat and mass transfer coefficients, with the possibility of accounting for vibrations. The numerical results indicate the preponderance of the interactions between droplet and carrier fluid at various humidity ratios.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

First Flight from Europe to the South Atlantic

The History of the transatlantic flights goes back to 1919 and began with a flight performed from Newfoundland to Lisbon; two weeks later another flight was performed between Newfoundland and Ireland. On 1922, the Portuguese airmen Gago Coutinho and Sacadura Cabral crossed the South Atlantic Ocean by air in a flight performed exclusively with internal means of navigation: a new instrument that consisted in a type of sextant improved with two spirit levels to provide an artificial horizon and also with the help of a “path corrector”. Despite this journey had lasted 79 days to cross South Atlantic Ocean, their flight time was only 62:26 minutes, and they’ve flown 8,383 nautical miles, using 3 different hydroplanes christened: Lusitania, Pátria and Santa Cruz. Despite this journey had lasted 79 days, their flight time was only 62 h 26 m; they’ve flown 8,383 nautical miles using 3 different hydroplanes christened: Lusitania, Pátria and Santa Cruz. The new artificial horizon sextant had proven itself while flying over the ocean, without external references.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio