Papers by Keyword: Cellular

Abstract: The growing environmental concern throughout the globe has led architects & engineers to design energy efficient buildings. Consequently, they are looking for building materials that can reduce the energy consumption in buildings to maintain the comfort level. Use of proper thermal insulating materials can reduce the energy required for heating or cooling of the buildings. Presently mineral wool and various foams are used for this purpose. Efforts are being made to use wastes in making thermal insulation materials so that the impact on environment can be further reduced. Cork granules are obtained as waste from the cork processing industries that make ‘bottle stoppers’ as a main product. These granules have a low density and could be used as lightweight aggregates for making concrete with low thermal conductivity. This article describes the physico-mechanical properties of lightweight cementitious composites made using cork granules. Further, environmental benefits of their application in thermal insulation of buildings has been discussed.

Abstract: The VHF radio can overcome line-of-sight transmission by “repeaters,” which pick up weak signals, amplify and retransmit them on a different frequency. However, repeaters can interfere with each other unless they are far enough apart or transmit on sufficiently separated frequencies. In this paper, we propose such a system using the continuous tone-coded squelch system (CTCSS) to mitigate interference problems. This system associates to each repeater a separate sub-audible tone that is transmitted by all users who wish to communicate through that repeater. The repeater responds only to receive signals with its specific tone.

Abstract: Very high frequency (VHF) is widely used in radio and television broadcasting. In order to improve the quality of service (QoS) and signal transmission distance, the repeaters be applied to lengthen the transmitting distance of VHF and expand the coverage of radio stations. Under ensuring the QoS, the reduction cost is very important. In this paper, focusing on the different coverage of repeaters, we discuss the minimum number of repeaters to cover a whole circular area, and the square model and cellular model are proposed. Then we analyze the case in view of the simplex communication and duplex communication. Furthermore, the influence of the location of the radio station to the minimum number of repeaters needed is discussed. Finally, we discuss how the minimum number of repeaters changes with the change of the numbers of radio stations. The minimum number of repeaters to cover the circle area will increase as the radius of the repeaters coverage decreases. The radio station in the center of the circle flat can broadcast to the farthest area and the radio station in the fringe area can’t broadcast to farther area. In simplex communication, the minimum number of repeaters with n radio stations in the circle are is n-1 times greater than that with only one radio station.

Abstract: This paper presents a crowding niche cellular genetic algorithm (referred to NCGA) aiming at solving the problems of local convergence and non-uniform population distribution in traditional genetic algorithm. The selecting operation in traditional genetic algorithm is improved by bringing in the concept of neighbors of cellular genetic algorithm, and the population distribution is greatly enhanced by introducing crowding niche mechanism, which betters the ability of global searching and helps to avoid the population local convergence. Meanwhile, the paper describes the crowding niche cellular genetic algorithm in details and compares it with simple genetic algorithm （SGA） and simple niche genetic algorithm （NGA）; the comparison results reveal that, NCGA outperforms the other two algorithms in terms of convergence rate and population diversity.

Abstract: Wireless sensor networks (WSNs) are vulnerable to a variety of malicious attacks, especially the packet dropping attack, making security an important research field. Since prevention based techniques are less helpful for guarding against inside attacks, intrusion detection (ID) techniques are indispensable to provide advanced protection. This paper proposes an innovative cellular ID framework for packet dropping attack, which takes the deployment of passive listening nodes into consideration. Performance evaluation made in VisualSense demonstrates its high detection accuracy.

Abstract: Closed form expressions for the Cosserat constants for circular cell honeycombs are derived using a combination of non-dimensional analysis and numerical analysis. The expressions for the four in-plane Cosserat compliances, which are the plane strain bulk compliance, the shear compliance, the micropolar compliance and the bending compliance are derived in terms of the cell size, cell thickness and the linear elastic properties of the cell wall material. Numerical analyses are performed to verify the accuracy of the derived constants by considering different combinations of geometric parameters and different numbers of cells for the honeycombs. It is shown that the closed form expressions are an accurate representation of the Cosserat constants of circular cell honeycombs.

Abstract: This paper discusses the penetration behavior of fully supported sandwich panels with micro-lattice and foam cores, and composite skins. This behaviour is of importance during foreign object impact and perforation of sandwich structures. Experimental results are given for quasi-static penetration of micro-lattice and foam blocks, and it is shown that these two cellular materials are comparable. Experimental results are also given for drop weight penetration of fully supported skinned panels, and it is shown that skin failure and core penetration are also similar for the two core materials. It is concluded that there is scope for improving the performance of micro-lattice structure and so making such material superior to that of aluminium foam.