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Abstract:Combined open channel flow is encountered in many hydraulic engineering structures and processes, such as irrigation ditches and wastewater treatment facilities. Extensive experimental studies have conducted to investigate combined flow characteristics. Nevertheless, there is no simple relationship that can fully describe the velocity profiles in a turbulent flow. The artificial neural network (ANN) has great computational capability for solving various complex problems, such as function approximation. The main objective of this study is to evaluate the applicability of the ANN for simulating velocity profiles, velocity contours and estimating the discharges accordingly. The velocity profiles measured by an acoustic doppler velocimeter in the open channel of the Chihtan purification plant, Taipei, with different discharges at fixed measuring section and different depths are presented. The total number of data sets is 640 and the data sets are split into two subsets, i.e. training and validation sets. The backpropagation algorithm is used to construct the neural network. The results demonstrate that the velocity profiles can be modelled by the ANN, and the ANN constructed can nicely fit the velocity profiles and can precisely predict the discharges for the conditions investigated.

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Abstract-Varactor tuned printed planar inverted-F antennas (PIFA) are investigated. The low-profile printed antennas are fabricated together with the layouts of its DC control circuits and other RF/baseband circuit footprints. A surface mounted (SMT) varactor is applied as a frequency-tuning element at the middle of the long radiating arm in PIFA. Passive lumped DC bias circuits are implemented with good isolation. Both single and dual-band varactor tuned PIFA antennas are investigated. For a single-band PIFA, prototype designs show the in-band frequency (return loss is <10 dB) is tunable from 1.6 GHz to 2.3 GHz when the bias voltage varies from 0 V to 9.5 V. Measured results show about 70∼75% efficiency and 2∼3 dB maximum gain. For a dual band PIFA with two varactor loadings, both the 800∼900 MHz and 1.7∼2.2 GHz bands are tuned individually by a varactor. By varying low-band capacitance, the operation frequency is tuned from 780 MHz to 1020 MHz, with little change on the higher frequency band. By varying high-band capacitance, the operation frequency is tuned from 1700 MHz to 2140 MHz, with little change on the lower frequency. Measurement shows antenna radiation efficiencies within operation bands are about 55% at the low band and about 45% at the high band. The proposed frequency reconfigurable antennas could be useful for personal mobile terminal applications.

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