3,029 research outputs found
Error estimation of closed-form solution for annual rate of structural collapse
With the increasing emphasis of performance-based earthquake engineering (PBEE) in
the engineering community, several investigations have been presented outlining simplified
approaches suitable for performance-based seismic design (PBSD). Central to most of these
PBSD approaches is the use of closed-form analytical solutions to the probabilistic integral
equations representing the rate of exceedance of key performance measures. Situations where
such closed-form solutions are not appropriate primarily relate to the problem of extrapolation
outside of the region in which parameters of the closed-form solution are fit. This study
presents a critical review of the closed form solution for the annual rate of structural collapse.
The closed form solution requires the assumptions of lognormality of the collapse fragility
and power model form of the ground motion hazard, of which the latter is more significant
regarding the error of the closed-form solution. Via a parametric study, the key variables
contributing to the error between the closed-form solution and solution via numerical
integration are illustrated. As these key variables can not be easily measured it casts doubt on
the use of such closed-form solutions in future PBSD, especially considering the simple and
efficient nature of using direct numerical integration to obtain the solution
Energy efficiency of mmWave massive MIMO precoding with low-resolution DACs
With the congestion of the sub-6 GHz spectrum, the interest in massive
multiple-input multiple-output (MIMO) systems operating on millimeter wave
spectrum grows. In order to reduce the power consumption of such massive MIMO
systems, hybrid analog/digital transceivers and application of low-resolution
digital-to-analog/analog-to-digital converters have been recently proposed. In
this work, we investigate the energy efficiency of quantized hybrid
transmitters equipped with a fully/partially-connected phase-shifting network
composed of active/passive phase-shifters and compare it to that of quantized
digital precoders. We introduce a quantized single-user MIMO system model based
on an additive quantization noise approximation considering realistic power
consumption and loss models to evaluate the spectral and energy efficiencies of
the transmit precoding methods. Simulation results show that
partially-connected hybrid precoders can be more energy-efficient compared to
digital precoders, while fully-connected hybrid precoders exhibit poor energy
efficiency in general. Also, the topology of phase-shifting components offers
an energy-spectral efficiency trade-off: active phase-shifters provide higher
data rates, while passive phase-shifters maintain better energy efficiency.Comment: Published in IEEE Journal of Selected Topics in Signal Processin
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