Performance of Data-Rate Analysis of Massive MIMO System Using User Grouping

Wireless Personal Communications - The major challenges in massive MIMO networks are to increase the system throughput and capacity with low complexity and reliability of the wireless communication...     

Electrical Resistivity of Titanium Diboride and Zirconium Diboride

The electrical resistivities of hot-pressed samples of Ti_{1- x} Zr _x B₂ ( x = 0.0, 0.3, 0.5, 0.7, 1.0) were measured by a four-point ac technique over the range 298 to 1573 K in an argon atmosphere. The hot-pressed samples for the intermediate compositions were found to be mixtures of two solid-solution phases. The resistivities for all compositions were found to increase linearly with temperature and can be described by ρ( T ) =ρ₂₉₈+φ( T - 298). The room-temperature resistivity ρ298 (μΩ cm) and the temperature coefficient of resistivity φ (nΩ·cm/K) for ZrB₂ were determined to be 7.8 and 10, both of which increase with the content of TiB₂. These values for TiB₂ were determined to be 20.4 and 36, respectively.     

Sedimentation behavior of mixed solid particles

During the material relocation phase of core-disruptive accidents in sodium-cooled fast reactors, the sedimentation behavior of fragmented debris discharged from the reactor core into the lower plenum region leading to a debris-bed formation is crucial in regard to in-vessel retention and safety concerns. The height of the beds formed may influence both the cooling of the bed from the decay heat in the fuel and the neutronic characteristics. To develop an experimental database of bed formation behavior, a series of experiments using simulant materials, namely, Al₂O₃, ZrO₂, and stainless steel, were performed under gravity-driven discharge of solid particles from a nozzle into a quiescent cylindrical water pool. The bed height was measured for particles of different size, density, and sphericity, and an injection nozzle with varying diameter, injection velocity, and injection height. From these experiments, an empirical correlation was established to predict the bed height for both homogeneous and mixed particles for the different properties. This correlation reproduces reasonably well the experimental trend in bed height with critical factors, which were identified in this and previous experiments.     

Design of NS3 VLC module and performance analysis of ad hoc network under VLC and Wi‐Fi layers

Visible light communication (VLC) is the branch of optical wireless communications that uses light‐emitting diodes for the dual purpose of illumination and very‐high‐speed data communication. The main motivation behind the current work is finding alternatives to the saturated radio frequency spectrum, radio frequency security issue, and vulnerability to interferences. The current work is aimed at developing a module for the physical layer of a VLC‐based ad hoc network in network simulation 3. The VLC physical layer module is developed by using the optical signal modules available in the network simulator. The work also includes modelling of VLC‐based transmitter, wireless optical channel, and the optical receiver. Furthermore, the implementation and evaluation of the VLC‐based physical layer is carried out over a typical ad hoc network under different performance metrics. The designed ad hoc network is also tested under Wi‐Fi module followed by its comparison with corresponding ad hoc network under VLC module. The comparison is based on bit error rate curves, system throughput, and gain in received signal‐to‐noise ratio mainly. Finally, the suitability of different modulation schemes is also investigated in the current work for both Wi‐Fi– and VLC‐based ad hoc networks.     

Exergetic performance and comparative assessment of bottoming power cycles operating with carbon dioxide–based binary mixture as working fluid

This paper presents CO₂-toluene (CO₂-C₇H₈) binary mixture as working fluid to enhance the energetic and exergetic performance of CO₂ bottoming power cycles in warm ambient conditions. A criterion for selection of CO₂-based binary mixture is defined, and 0.9 CO₂/0.1 C₇H₈ composition is decided based on the required minimum cycle temperature compatible with ambient conditions. Bottoming simple regenerative cycle (BSRC) and bottoming preheating cycle (BPHC) configurations are selected, and their realistic operating conditions are determined based on sensitivity analysis. The performance of bottoming cycles using CO₂-C₇H₈ binary mixture is compared with the bottoming cycles using pure CO₂ as working fluid at different ambient temperatures. It is observed that the cycles operating with pure CO₂ can only perform better at lower ambient temperature conditions, whereas, at the increased ambient temperatures, bottoming cycles with CO₂-C₇H₈ binary mixture outperform and produce significant gains in exergetic and energetic performance compared with pure CO₂ bottoming cycles. A maximum gain of exergetic efficiency for BSRC and BPHC observed is 26.83% and 18.71%, respectively, at an operating ambient temperature of 313 K, whereas an overall gain in energetic efficiencies for BSRC and BPHC observed is 28.92% and 10.12%, respectively. Taking into consideration thermodynamic performance, overall UA (product of overall heat transfer coefficient and heat transfer area for the heat exchanger) and specific investment cost, BPHC configuration is suggested as reasonable choice for higher ambient temperature conditions.     

Octane Rating of Gasoline and Octane Booster Additives

Gasoline is a petroleum-derived liquid that is used primarily as a fuel in internal combustion engines (ICE), particularly spark ignition Otto Engine. Gasoline is a blend of hydrocarbons with some contaminants, including sulfur, nitrogen, oxygen, and certain metals. The four major constituent groups of gasoline are olefins, aromatics, paraffins, and napthenes. Octane number (ON) is measure of the ignition quality or flammability of gasoline. The ONs are Research Octane Number (RON) and Motor Octane Number (MON). RON is measured relative to a mixture of isooctane and n-heptane. Antiknock Index (AKI) is a measure of a fuel's ability to resist engine knock or octane quality. The AKI is an arithmetic average of RON and MON. The ON decreases with an increase chain length in the hydrocarbon molecule. The ONs increase with carbon chain branching. Another way of increasing the ON is used gasoline octane boosters as additives, such as tetraethyl lead (TEL), methyl tertiary-butyl ether (MTBE), and ferrocene. Aromatic alcohols, ethanol, and methanol also increase the ON of gasoline. The advantage to adding oxygenates, such as MTBE, methanol, and ethanol, to gasoline is that they cause very little pollution when they burn and are cleaner fuels.     

Buckling of Laminated Composite Plates by a New Element Based on Higher Order Shear Deformation Theory

The simple higher-order shear deformation theory proposed by Reddy has been successfully implemented in a triangular element recently developed by the authors. In this paper the element is applied to buckling of composite plates to study its performance. In this plate theory the transverse shear stress has parabolic through thickness variation and it is zero at top and bottom surfaces of the plate. Moreover, it does not introduce any additional unknown in the formulation. Thus, the plate theory is quite simple and elegant but it cannot be implemented in most of the elements, as the plate theory demands C 1 continuity of transverse displacement along the element edges. This has inspired the authors to develop this new element, which has shown an excellent performance in static analysis of composite plates. To demonstrate the performance of the element in the problem of buckling, examples of isotropic and composite plates under different situations are solved. The results are compared with the analytical solutions and other published results, which show the precision and range of applicability of the proposed element in the present problem.     

Influence of non‐structural components on lateral stiffness of tall buildings

A building is a complex assemblage of both structural and non‐structural components (NSC). Although many NSC, such as partition walls, external walls, parapet walls, stairwells, elevator shafts and so forth, are connected directly to the structural system, their behaviour and stiffening effects under lateral loading have normally been ignored by design engineers, despite significant advances in computer technology and the availability of modern computational resources. The performance of structures can be greatly improved by the increase in strength arising from the NSC; on the contrary, this increase in strength also accompanies an increase in the initial stiffness of the structure, which may consequently attract additional seismically induced lateral inertia forces. This paper is concerned with the estimation of the lateral stiffness contributed by the NSC to the total stiffness of three common forms of tall building structures constructed in Hong Kong. Both dynamic tests and numerical modelling of the buildings have been carried out for this purpose. Natural period estimates from dynamic tests and from analyses using calibrated finite element models were found to be in remarkable agreement. Significant stiffness contributions from NSC to the total lateral stiffness of tall buildings have been observed in the study. The extent of the contributions depends on the structural form and the type of components. Other contributions to the additional stiffness have also been analysed for comparison in the study. Copyright © 2005 John Wiley & Sons, Ltd.     

The Influences of Fibre Parameters on the Tensile and Flexural Response of Lightweight Thermoplastic Kenaf Fibre Reinforced Metal Composites

ABSTRACT

The increasing demand for high performance and lightweight materials has stimulated the development of alternative materials, namely fiber metal laminates (FMLs). FML is a sandwich structure which is formed by bonding the metallic layers with composite as core constituent using an adhesive agent. In this study, the mechanical behavior of FMLs with the core constituents of environmental friendly kenaf bast fiber reinforced polypropylene composites bonded with aluminum skin layers was investigated. The effects of fiber compositions (50, 60, and 70 wt.%), fiber lengths (30, 60, 90 mm), and alkali treatment on the mechanical responses of FML were investigated. The overall results revealed that the increase of fiber composition and fiber length reduces the mechanical strength of FML owing to the agglomeration of natural fibers when the fiber length exceeds the critical limit. However, the chemical treated kenaf bast fiber reinforced FML showed a significant enhancement of the mechanical properties in comparison to the non-treated fiber reinforced FML owing to the improved fiber-matrix adhesion level.