2,280 research outputs found
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
A note on the gaps between consecutive zeros of the Riemann zeta-function
Assuming the Riemann Hypothesis, we show that infinitely often consecutive
non-trivial zeros of the Riemann zeta-function differ by at most 0.5155 times
the average spacing and infinitely often they differ by at least 2.69 times the
average spacing.Comment: 7 pages. Submitted for publicatio
RF photonic instantaneous frequency measurement using DC photo-detection
A microwave photonic instantaneous frequency measurement (IFM) system based on a photonic transversal approach and DC-detection is proposed and practically demonstrated. This system is able to measure the RF frequency and power level independently
Two output RF hybrid coupler using photonic transversal approach
A novel technique to implement a two output broad band RF hybrid coupler based on transversal signal processing is proposed and practically demonstrated. It features broadband frequency range, stable phase difference at outputs, 50 ohm input/output impedance, and low noise characteristics. This technique is suitable for non-coherent optic implementation
Reduced cost photonic instantaneous frequency measurement system
A wideband photonic instantaneous frequency measurement system is proposed and practically demonstrated. This system employs only a low-frequency inexpensive photodetector and thus the system cost is reduced
Amplitude independent RF instantaneous frequency measurement system using photonic Hilbert transform
A photonic instantaneous frequency measurement system capable of measuring both RF frequency and power simultaneously, is conceived and practically demonstrated. This system employs an RF photonic Hilbert transformer together with low-cost, low-frequency photo-detectors to obtain two orthogonal DC measurements. This system exhibits a frequency range of 1-10 GHz. Wider frequency range can be achieved through integration
Wideband RF photonic in-phase and quadrature-phase generation
A photonic implementation of a practical broadband RF Hilbert transformer is demonstrated by using a four-tap transversal system. An almost ideal 90° phase shift with less than 3 dB of amplitude ripple has been achieved from 2.4 to 17.6 GHz. An efficient method to realize both transformed (quadrature-phase) and reference (in-phase) signal has been achieved by using a coarse wavelength division multiplexing coupler. Extension of the transformer bandwidth and further improvements of its implementation are discussed
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