Joint beam selection and user association strategy for beam space millimetre wave downlink systems

Beam space multiple‐input multiple‐output (B‐MIMO) systems operating at mmWave frequency in downlink uses different beam selection techniques for reducing the required number of radio frequency chains without apparent performance loss. In this paper, a joint beam selection and user association scheme with the objective of sum rate maximization is proposed. The proposed work on beam selection is based on a norm and uncorrrelation based approach, which considers channel correlation among the users so as to avoid inter‐user interference. Two different methods for beam user association with one modelled as a balanced assignment problem based on average sum assignment method and the other method that associates an optimal beam to every user by considering their channel gain values are also proposed along with beam selection. The proposed beam assignment methods are less complex and efficient in finding a suitable beam to every user within the cell. Simulation results show that the proposed method accomplish comparable performance in terms of sum rate and energy efficiency with appreciably low computational complexity relative to the existing methods in a correlated environment.     

Utilizing Space-Time Diversity for Wireless Communications

In this paper we consider the use of multiple antennas for wireless communication over fading channels.The fading we consider is quasi-static flat Rayleigh fading. For such a scenario optimal SNR schemes are derived when the transmitter knows the channel and when the transmitter does not know the channel. But in both cases the receiver has to estimate the channel. When the SNR during channel estimation is reasonably high we derive expressions to show the impact of channel estimation errors on SNR.     

Organometallic L-Alanine Cadmium Iodide Crystals for Optical Device Fabrication

Single crystals of L-alanine cadmium iodide (LACI) were grown by the slow evaporation technique at room temperature. A single-crystal X-ray diffraction (SXRD) model was used to evaluate the crystal structure of the as-grown LACI crystal. The energy dispersive X-ray (EDX) analysis and ultraviolet-visible-near infrared (UV-vis-NIR) transmittance studies were carried out, and the results reveal the presence of elements in the title compound. From the transmittance data, the optical bandgap as a function of photon energy was estimated, and the different optical constants were calculated. A fluorescence study was performed for the LACI crystal. Thermogravimetric and differential thermal analyses have also been studied to investigate the thermal property of the LACI crystal. The efficiency of the second harmonic generation (SHG) of the title crystal was investigated. The magnetic and electrical properties were estimated by the vibrating sample magnetometer (VSM) analysis and impedance study, respectively.     

Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe2 thin films

Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.     

Modeling of local controllers in distribution network applications

Local automatic controllers are an integral part of a modern distribution system. They control transformer load tap changer (LTC) positions and statuses of switched capacitors to ensure voltage and loading constraints are satisfied under changing operating conditions. Distribution network applications, which traditionally have been used for planning, account for the presence of local controllers in a simplified manner. Distribution management systems (DMS) bring network applications to the operational practice which requires much more detailed modeling of local controllers, both for the purpose of real-time power flow monitoring, and for centralized control. In the latter case, the local controllers create both opportunities and restrictions for DMS optimization functions such as volt/VAr control and feeder reconfiguration. This paper describes how the LTC and capacitor local controllers are modeled as a part of the power flow solution, and how they interact and affect DMS optimization functions. The impact of the local controller modeling on power flow, volt/VAr control and feeder reconfiguration is illustrated by numerical examples     

Adhesion of Dry Seasoning Particles onto Tortilla Chip

ABSTRACT: In a wind tunnel experiment, the amount of seasoning retained by a fried tortilla chip when exposed to air at different flow rates (0.516 to 1.115 m/s) and angles of inclination (0° to 60°) was measured. The inferred adhesion force of seasoning particle and chip surface using boundary layer theory increased with seasoning particle size (32 to 300 μm), oil content of tortilla chip (24% to 32%), viscosity (55.9 to 72.2 cP), and surface tension (27.5 to 34.1 mN/m) of oil and was in the range of 1.6 × 10⁻⁹to3.3 × 10⁻⁷N. The calculated values of adhesion force accounting for van der Waals, electrostatic, and capillary forces showed the same qualitative trend as the experimental data.     

Analysis of machining of FRPs using FEM

An initial attempt has been made to develop a mathematical model for machining of FRPs. The anisotropic theory of plasticity has been utilized. The analysis is carried out for four different FRP materials and for four different fibre orientation angles. A total Lagrangian formulation-based transient elasto-plastic finite element analysis has been adopted.