Differential Amplify-and-Forward Relaying in Time-Varying Rayleigh Fading Channels

This paper considers the performance of differential amplify-and-forward (D-AF) relaying over time-varying Rayleigh fading channels. Using the auto-regressive time-series model to characterize the time-varying nature of the wireless channels, new weights for the maximum ratio combining (MRC) of the received signals at the destination are proposed. Expression for the pair-wise error probability (PEP) is provided and used to obtain an approximation of the total average bit error probability (BEP). The obtained BEP approximation clearly shows how the system performance depends on the auto-correlation of the direct and the cascaded channels and an irreducible error floor exists at high signal-to-noise ratio (SNR). Simulation results also demonstrate that, for fast-fading channels, the new MRC weights lead to a better performance when compared to the classical combining scheme. Our analysis is verified with simulation results in different fading scenarios

Seismic Earth Pressure Development in Sheet Pile Retaining Walls: A Numerical Study

The design of retaining walls requires the complete knowledge of the earth pressure distribution behind the wall. Due to the complex soil-structure effect, the estimation of earth pressure is not an easy task; even in the static case. The problem becomes even more complex for the dynamic (i.e., seismic) analysis and design of retaining walls. Several earth pressure models have been developed over the years to integrate the dynamic earth pressure with the static earth pressure and to improve the design of retaining wall in seismic regions. Among all the models, MononobeOkabe (M-O) method is commonly used to estimate the magnitude of seismic earth pressures in retaining walls and is adopted in design practices around the world (e.g., EuroCode and Australian Standards). However, the M-O method has several drawbacks and does not provide reliable estimate of the earth pressure in many instances. This study investigates the accuracy of the M-O method to predict the dynamic earth pressure in sheet pile wall. A 2D plane strain finite element model of the wall-soil system was developed in DIANA. The backfill soil was modelled with Mohr-Coulomb failure criterion while the wall was assumed behave elastically. The numerically predicted dynamic earth pressure was compared with the M-O model prediction. Further, the point of application of total dynamic force was determined and compared with the static case. Finally, the applicability of M-O methods to compute the seismic earth pressure was discussed

The application of BIM tools to explore the dynamic characteristics of smart materials in a contemporary Shanashil building design element

Traditional architecture is known for its crafted facade features that respond to environmental, social and cultural requirements. Contemporary architecture produced façade features that attempted to enhance local design identity and local culture. Despite the advantages of modern technology, architectural elements have difficulties in fulfilling the idea of sustainable elegance that once traditional elements provided. This problem calls for an interdisciplinary design approach to deliver sustainable design solutions that positively adapt to the surrounding environment as well as maintain the state of elegance in design. With this in mind, the research aims to explore the role of new glass technologies to improve the performance and at the same time maintain the design value of traditional façade element “shanashil” in Baghdadi buildings. This research utilises BIM tools and uses smart materials to restore the lost value in design, which mimics the dynamic characteristics observed in nature, inspired by biomimetics strategies. Such qualities are found in the characteristics of smart dynamic glazing material particularly in the switchable, reversible properties of transparency and coloration efficiency. The material characteristics are attached to a 3D digital prototype to visualise the difference between dynamic and static properties through the use of technology tools Revit plugin and smart glazing virtual reality prototype. This research concludes that the dynamic characteristics of smart glazing materials are effective in delivering a multifunctional design quality to collectively blend in harmony with the surrounding environment

Entanglement witnesses arising from Choi type positive linear maps

We construct optimal PPTES witnesses to detect $3\otimes 3$ PPT entangled edge states of type $(6,8)$ constructed recently \cite{kye_osaka}. To do this, we consider positive linear maps which are variants of the Choi type map involving complex numbers, and examine several notions related to optimality for those entanglement witnesses. Through the discussion, we suggest a method to check the optimality of entanglement witnesses without the spanning property.Comment: 18 pages, 4 figures, 1 tabl

Cohen-Macaulay admissible clutters

There is a one-to-one correspondence between square-free monomial ideals and clutters, which are also known as simple hypergraphs. It was conjectured that unmixed admissible clutters are Cohen-Macaulay. We prove the conjecture for uniform admissible clutters of heights 2 and 3. For admissible clutters of greater heights, we give a family of examples to show that the conjecture may fail. When the height is 4, we give an additional condition under which unmixed admissible clutters are Cohen-Macaulay.Comment: 13 pages, final version to appear in J. Comm. Al