On the performance of improved quadrature spatial modulation

Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.     

High data rate measurements of droplet dynamics in a vertical gas-liquid annular flow

Two-dimensional phase Doppler anemometry techniques have been used to achieve simultaneous measurement of the velocity and size of individual droplets entrained into the gas core during upward annular gas-liquid flow. Data rates greatly exceeding those of other experimental techniques have been achieved. Information is presented on the centreline variation of droplet velocity and droplet size, together with size and velocity correlations, for a range of flowrates and hydrodynamic development lengths from 135 to 228.     

Strategic Resource Development Options in England and Wales

This paper describes the options which had to be considered for new water resources in the development of the † National Rivers Authority's water resource strategy for England and Wales. The options included interregional transfers, strategic reservoirs, and a range of unconventional schemes including aquifer recharge, effluent re-use, groundwater abstraction where levels are rising, desalination, and transfer by sea. The main options are described and comparative costs are presented.     

A Multi-radio 802.11 Mesh Network Architecture

The focus of this paper is to offer a practical multi-radio mesh network architecture that can realize the benefits of multiple radios. Our architecture provides solutions to challenges in three key areas. The first is the construction of a split wireless router that enables modular wireless mesh routers to be constructed from commodity hardware. The second is the design of a centralized channel assignment algorithm that considers the inter-dependence between channel assignment and routing in order to create high-throughput channel-diversified routes. Third is the design and implementation of several communication protocols that are necessary to make our architecture operational. Our system is comprehensively evaluated on a 20-node multi-radio wireless testbed. Results demonstrate that our architecture makes feasible the deployment of large-scale high-capacity multi-radio mesh networks built entirely with commodity hardware. Our implementation is available to the community for research and development purposes.     

Novel Approach for Modeling Wireless Fading Channels Using a Finite State Markov Chain

Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal‐to‐noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first‐order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.     

A study on buckling of thin conical frusta under axial loads

Experiments were performed wherein conical frusta of aluminium of thicknesses between 0.7 and 1.62 mm and semi-apical angles range of 16–29° were axially compressed in a universal testing machine. The load–deformation curves and deformed shapes of specimens were recorded. These deformed in axisymmetric concertina mode and non-symmetric diamond modes.A three dimensional numerical simulation was carried out for all samples tested under quasi-static loading using ANSYS^®. Various stages of collapse of the shell, including non-symmetrical lobe formation were simulated for the first time, and material, geometric and contact non-linearities were incorporated. The plastic region of the material curve was assumed to be piecewise linear. Tensile tests were performed on standard samples to obtain stress–strain curves. Results thus obtained compared well with the experiments.Based on the formation of rolling and stationary plastic hinges an analysis was also carried out to study the behaviour of shells under axial compression and results were compared with experimental and numerical results.     

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel are numerically investigated. The continuity, momentum and energy equations were solved by means of a finite volume method (FVM). The top and bottom walls of the channel are heated at a constant temperature. Nine different rib–groove shapes are considered in this study, which are three different rib shapes with three different groove shapes including rectangular, triangular and trapezoidal and they are interchanged with each other. Four different types of nanoparticles Al₂O₃, CuO, SiO₂, and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 25 nm to 80 nm, are dispersed in different base fluids (water, glycerin, engine oil) are used. In this study, several parameters such as different Reynolds numbers in the range of 5000 < Re < 20000, and different rib–groove aspect ratios in the range of 0.5 ≤ AR ≤ 4 are also examined to identify their effects on the heat transfer and fluid flow characteristics. The results indicate that the rectangular rib–triangular groove has the highest Nusselt number among other rib–groove shapes. The SiO₂ nanofluid has the highest Nusselt number compared with other nanofluid types. The Nusselt number increased as the nanoparticle volume fraction, Reynolds number and aspect ratio increased; however, it decreased as the nanoparticle diameter increased. It is found that the glycerin–SiO₂ shows the best heat transfer enhancement compared with other tested base fluids.     

Nutritional,Functional and Physical Properties of Extrudates from Blends of Cassava Flour with Cereal and Legume Flours

Low protein and poor functionality limit the use of cassava flour in snack foods, which were modified using blends with cereal and/or legume flours. Native, malted (using alpha-amylase) as well as malted and pre-gelatinized was blended with cereal (finger millet and whole wheat flours) and/or legume (chick pea flour). Extrudates were prepared at a screw speed of 100 rpm and die temperature of 180 °C. Malted flour based extrudates had lower starch content than native flour. Gram malted cassava based blends gave products with the highest protein. In vitro starch digestibility was the highest for pre-gelatinized flour based mixes. Extrudates with low fat and energy have scope as low calorie snacks for obese and diabetic people.     

Process optimization for bioethanol production from cassava starch using novel eco-friendly enzymes

Although cassava (Manihot esculenta Crantz) is a potential bioethanol crop, high operational costs resulted in a negative energy balance in the earlier processes. The present study aimed at optimizing the bioethanol production from cassava starch using new enzymes like Spezyme^® Xtra and Stargen™ 001. The liquefying enzyme Spezyme was optimally active at 90 °C and pH 5.5 on a 10% (w/v) starch slurry at levels of 20.0 mg (280 Amylase Activity Units) for 30 min. Stargen levels of 100 mg (45.6 Granular Starch Hydrolyzing Units) were sufficient to almost completely hydrolyze 10% (w/v) starch at room temperature (30 ± 1 °C). Ethanol yield and fermentation efficiency were very high (533 g/kg and 94.0% respectively) in the Stargen + yeast process with 10% (w/v) starch for 48 h. Raising Spezyme and Stargen levels to 560 AAU and 91.2 GSHU respectively for a two step loading [initial 20% (w/v) followed by 20% starch after Spezyme thinning]/initial higher loading of starch (40% w/v) resulted in poor fermentation efficiency. Upscaling experiments using 1.0 kg starch showed that Stargen to starch ratio of 1:100 (w/w) could yield around 558 g ethanol/kg starch, with a high fermentation efficiency of 98.4%. The study showed that Spezyme level beyond 20.0 mg for a 10% (w/v) starch slurry was not critical for optimizing bioethanol yield from cassava starch, although an initial thinning of starch for 30 min by Spezyme facilitated rapid saccharification-fermentation by Stargen + yeast system. The specific advantage of the new process was that the reaction could be completed within 48.5 h at 30 ± 1 °C.