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Topic Review
Deformable Mirror
Deformable mirrors (DM) are mirrors whose surface can be deformed, in order to achieve wavefront control and correction of optical aberrations. Deformable mirrors are used in combination with wavefront sensors and real-time control systems in adaptive optics. In 2006 they found a new use in femtosecond pulse shaping. The shape of a DM can be controlled with a speed that is appropriate for compensation of dynamic aberrations present in the optical system. In practice the DM shape should be changed much faster than the process to be corrected, as the correction process, even for a static aberration, may take several iterations. A DM usually has many degrees of freedom. Typically, these degrees of freedom are associated with the mechanical actuators and it can be roughly taken that one actuator corresponds to one degree of freedom.
  • 405
  • 03 Nov 2022
Topic Review
Kubota Engines
Kubota engines are diesel and spark ignition engines manufactured by Kubota Corporation. Besides gasoline-fueled for spark ignition engines, the company produces dual fuel, LPG-fueled, and natural-gas-fueled engines as well. The engines are widely used in various forms, such as: agricultural equipments, construction equipments, gensets, tractors, and marine propulsion. Beta Marine, an international company providing marine propulsion engines, uses various Kubota engines for fresh water and sea-going boats of various sizes.
  • 3.7K
  • 03 Nov 2022
Topic Review
Bayesian Model of Computational Anatomy
Computational anatomy (CA) is a discipline within medical imaging focusing on the study of anatomical shape and form at the visible or gross anatomical scale of morphology. The field is broadly defined and includes foundations in anatomy, applied mathematics and pure mathematics, including medical imaging, neuroscience, physics, probability, and statistics. It focuses on the anatomical structures being imaged, rather than the medical imaging devices. The central focus of the sub-field of computational anatomy within medical imaging is mapping information across anatomical coordinate systems most often dense information measured within a magnetic resonance image (MRI). The introduction of flows into CA, which are akin to the equations of motion used in fluid dynamics, exploit the notion that dense coordinates in image analysis follow the Lagrangian and Eulerian equations of motion. In models based on Lagrangian and Eulerian flows of diffeomorphisms, the constraint is associated to topological properties, such as open sets being preserved, coordinates not crossing implying uniqueness and existence of the inverse mapping, and connected sets remaining connected. The use of diffeomorphic methods grew quickly to dominate the field of mapping methods post Christensen's original paper, with fast and symmetric methods becoming available.
  • 263
  • 03 Nov 2022
Topic Review
Meo (Telecommunication Service)
MEO is a mobile and fixed telecommunications service and brand from Altice Portugal (formerly Portugal Telecom), managed by MEO - Serviços de Comunicações e Multimédia. The service was piloted in Lisbon in 2006 and was later extended to Porto and Castelo Branco.
  • 828
  • 03 Nov 2022
Topic Review
General Atomics Avenger
The General Atomics Avenger (formerly Predator C) is a developmental unmanned combat air vehicle built by General Atomics Aeronautical Systems for the U.S. military.
  • 1.6K
  • 03 Nov 2022
Topic Review
Passivation
Passivation, in physical chemistry and engineering, refers to coating a material so it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation in the air. As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shield against corrosion. Passivation of silicon is used during fabrication of microelectronic devices. In electrochemical treatment of water, passivation reduces the effectiveness of the treatment by increasing the circuit resistance, and active measures are typically used to overcome this effect, the most common being polarity reversal, which results in limited rejection of the fouling layer.[clarification needed] When exposed to air, many metals naturally form a hard, relatively inert surface layer, usually an oxide (termed the "native oxide layer") or a nitride, that serves as a passivation layer. In the case of silver, the dark tarnish is a passivation layer of silver sulfide formed from reaction with environmental hydrogen sulfide. (In contrast, metals such as iron oxidize readily to form a rough porous coating of rust that adheres loosely and sloughs off readily, allowing further oxidation.) The passivation layer of oxide markedly slows further oxidation and corrosion in room-temperature air for aluminium, beryllium, chromium, zinc, titanium, and silicon (a metalloid). The inert surface layer formed by reaction with air has a thickness of about 1.5 nm for silicon, 1–10 nm for beryllium, and 1 nm initially for titanium, growing to 25 nm after several years. Similarly, for aluminium, it grows to about 5 nm after several years. Surface passivation refers to a common semiconductor device fabrication process critical to modern electronics. It is the process by which a semiconductor surface such as silicon is rendered inert, and does not change semiconductor properties when it interacts with air or other materials. This is typically achieved by thermal oxidation, in which the material is heated and exposed to oxygen. In a silicon semiconductor, this process allows electricity to reliably penetrate to the conducting silicon below the surface, and to overcome the surface states that prevent electricity from reaching the semiconducting layer. Surface passivation by thermal oxidation is one of the key features of silicon technology, and is dominant in microelectronics. The surface passivation process was developed by Mohamed M. Atalla at Bell Labs in the late 1950s. It is commonly used to manufacture MOSFETs (metal-oxide-semiconductor field-effect transistors) and silicon integrated circuit chips (with the planar process), and is critical to the semiconductor industry. Surface passivation is also critical to solar cell and carbon quantum dot technologies.
  • 3.6K
  • 03 Nov 2022
Topic Review
SMT Placement Equipment
SMT (surface mount technology) component placement systems, commonly called pick-and-place machines or P&Ps, are robotic machines which are used to place surface-mount devices (SMDs) onto a printed circuit board (PCB). They are used for high speed, high precision placing of broad range of electronic components, like capacitors, resistors, integrated circuits onto the PCBs which are in turn used in computers, consumer electronics as well as industrial, medical, automotive, military and telecommunications equipment. Similar equipment exists for through hole components. This type of equipment is sometimes also used to package microchips using the flip chip method.
  • 422
  • 03 Nov 2022
Biography
José António Tenreiro Machado
Professor José António Tenreiro Machado, (see figure 1) was passionate about science. This manuscript intends to present his main research interests, pointing to the most relevant work that was published throughout his life. Moreover, a brief description of his early life and international academic career are also presented. His contributions to control, robotics, modeling, complex systems a
  • 899
  • 03 Nov 2022
Topic Review
CANT Z.501
The CANT Z.501 Gabbiano (Italian: Gull) was a high-wing central-hull flying boat, with two outboard floats. It was powered by a single engine installed in the middle of the main-plane and had a crew of 4–5 men. It served with the Italian Regia Aeronautica during World War II, as a reconnaissance aeroplane. During its debut in 1934, it set a world distance record. It was obsolete by 1940, but was still used throughout World War II, suffering many losses. A few remained in service until 1949.
  • 609
  • 03 Nov 2022
Topic Review
Lancia Delta Group A
The Lancia Delta Group A is a Group A rally car built for the Martini Lancia by Lancia to compete in the World Rally Championship. It is based upon the Lancia Delta road car and replaced the Lancia Delta S4. The car was introduced for the 1987 World Rally Championship season and dominated the World Rally Championship, scoring 46 WRC victories overall and winning the constructors' championship a record six times in a row from 1987 to 1992, in addition to drivers' championship titles for Juha Kankkunen (1987 and 1991) and Miki Biasion (1988 and 1989), making Lancia the most successful marque in the history of the WRC and the Delta the most successful car.
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  • 03 Nov 2022
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