9,104 research outputs found
Valve, normally closed, titanium Pyronetics model 1426
Performance tests of the explosive actuated, normally closed titanium valve 1426, are outlined. The valves are used to control hydrazine flow in a monopropellant thruster. Data cover pressure tests, internal and external leakage tests, flow control tests, and actuator tests. No failures were noted in any of the tests
Exponential decay properties of a mathematical model for a certain fluid-structure interaction
In this work, we derive a result of exponential stability for a coupled
system of partial differential equations (PDEs) which governs a certain
fluid-structure interaction. In particular, a three-dimensional Stokes flow
interacts across a boundary interface with a two-dimensional mechanical plate
equation. In the case that the PDE plate component is rotational inertia-free,
one will have that solutions of this fluid-structure PDE system exhibit an
exponential rate of decay. By way of proving this decay, an estimate is
obtained for the resolvent of the associated semigroup generator, an estimate
which is uniform for frequency domain values along the imaginary axis.
Subsequently, we proceed to discuss relevant point control and boundary control
scenarios for this fluid-structure PDE model, with an ultimate view to optimal
control studies on both finite and infinite horizon. (Because of said
exponential stability result, optimal control of the PDE on time interval
becomes a reasonable problem for contemplation.)Comment: 15 pages, 1 figure; submitte
Commercially-and-socially-oriented postal services
The main goal of this paper is show how postal communication service, which has been strengthened with the technology development in the last century, is nowadays commercially-and-socially-oriented very important for human life. Furthermore, I will prove how postal service becomes overwhelming for some not communicated, far and isolated geographic areas in developing countries, to get in touch with people and businesses from around the world. Over one hundred of Postal Operators were interviewed in Peru between 2004 and 2006, around 25% of total, which said that distance and security are not longer considered as a challenge for postal services thanks to new Information and Communication Technologies (ICT) and Internet; which in turn has facilitated (i) social communication, (ii) financial services, (iii) e-commerce and (iv) international business, bolstered by postal services. This last issue can be proved with high correlation statistics between the international postal (and courier) shipments and the exportation of non traditional goods, as well as importation of goods in Peru; moreover, some international remittances from around the world are making through the postal transferences. Consequently, Peruvian authorities, especially from the Ministry of Transport and Communications, must consider the importance of postal and/or courier services in the elaboration of public policies to pursuit the socioeconomic development.Postal services; financial postal; international business; communication; e-commerce;
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