117,311 research outputs found
Low-Cost Houses for Self-Construction with Precast Wall Panels
No full textThe experience is described of a low-cost housing project developed in the past years in Costa Rica. suited for its particular climate and social conditions. The construction system provides precast prestressed concrete panels with thin cross-section, that can be moved and erected by few non specialized people. without the help of machinery. A full one-family house is easily built by the users with some help, The structure is made of bearing wall panels, clamped in a channel on foundation and linked together on top by a wooden rod. Wooden truss-beams support a light roof and realize a horizontal diaphragm, too, System's main features are: safety (dimensioned against wind and seismic actions), security (concrete walls); flexibility of lay-out and ease of adding rooms for enlarging the house; economy (self-construction); pleasing appearance. More than 1200 house's have been built with it, in the frame of a government granted program
Flat Array Antennas for Ku-Band Mobile Satellite Terminals
No full textThis work presents the advances in the development of two innovative flat array antennas for Ku-band mobile satellite terminals. The first antenna is specifically conceived for double-deck trains to allow a bi-directional high data rate satellite link. The available circular surface (diameter 80 cm) integrates both a transmitting and a receiving section, operating in orthogonal linear polarizations. The TX frequency range is fully covered while the RX bandwidth is around 1 GHz arbitrarily allocated on the DVB range depending on requirements. The beam is steered in elevation through a phased array architecture not employing costly phase shifters, while the steering in azimuth is mechanical. Active BFNs allow excellent performance in terms of EIRP and G/T, maintaining extremely low profile. High antenna efficiency and low fabrication cost are ensured by the employment of innovative SIW (Substrate Integrated Waveguide) structures. The second antenna, receiving-only, is designed for radio/video streaming services in mobile environment. Full DVB coverage is achieved thanks to cavity-backed patches operating in double linear polarization. Two independent broadband active BFNs allow simultaneous reception of both polarizations with full tracking capabilities and a squintless beam steering from 20∘ to 60∘ in elevation. A minimum gain of 20 dBi and G/T >−3 dB/∘K are achieved, while maintaining extremely compact size and flat profile. In the design of both antennas fabrication cost is considered as a driving factor, yet providing high performance with a flat profile and thus resulting in a great commercial potentiality
Design and Realization of a MEMS Tunable Reflectarray for mm-Wave Imaging Application
No full textElectronic beam scanning reflectarrays represent a very interesting solution to obtain reconfigurable antennas at mm-wave frequencies. The potentialities of such systems could be further increased in terms of costs and performance by employing MEMS devices. In this paper we present the design and the simulated results of a two-layer MEMS tuneable reflectarray. This antenna is designed for outdoor passive mm-waves imaging applications (35 GHz). The target is to realize a low cost, fast, small and light antenna system to be implemented in portable devices. The manufacturing of the prototype is on the way at the ITC-irst (Trento – IT) laboratories
W-band beam-steerable MEMS-based reflectarray
No full textThis paper presents recent advances on reconfigurable reflectarrays at the University of Perugia. In particular, the activities carried out in the framework of the FP7 project ARASCOM (“MEMS and Liquid Crystal based” Agile Reflectarray Antennas for Security and COMmunication). As for ARASCOM outcomes, the purpose of the project is the design of a very large reconfigurable reflectarray controlled with micro-electro-mechanical systems (MEMS) for mm-wave imaging system at 76.5 GHz. A system with sufficient resolution to detect concealed weapons impose challenging requirements on the antenna, which shall be made of hundreds of thousands elements. The problem has been addressed by exploiting some innovative solutions and architectures that will be described in this document. In particular, the dimensioning of the reflectarray, the proposed 1-bit geometry of elementary cell, and the innovative biasing control architecture are reported together with the MEMS design and fabrication and the experimental results of a demonstrating board that validated the adopted procedure.</jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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