The construction and operation of cascade reservoirs has changed the natural hydrological cycle in the Yalong River Basin, and reduced the accuracy of hydrological forecasting. The impact of cascade reservoir operation on the runoff of the Yalong River Basin is assessed, providing a theoretical reference for the construction and joint operation of reservoirs. In this paper, eight scenarios were set up, by changing the reservoir capacity, operating location, and relative location in the case of two reservoirs. The aim of this study is to explore the impact of the capacity and location of a single reservoir on runoff processes, and the effect of the relative location in the case of joint operation of reservoirs. The results show that: (1) the reservoir has a delay and reduction effect on the flood during the flood season, and has a replenishment effect on the runoff during the dry season; (2) the impact of the reservoir on runoff processes and changes in runoff distribution during the year increases with the reservoir capacity; (3) the mitigation of flooding is more obvious at the river basin outlet control station when the reservoir is further downstream; (4) an arrangement with the smaller reservoir located upstream and the larger reservoir located downstream can maximize the benefits of the reservoirs in flood control.
In this paper, a novel modulation scheme called enhanced asymmetrically clipped DC-biased optical OFDM (eADO-OFDM) is proposed to accommodate different demands of multi-users in downlink multiple access for visible light communication systems. Meanwhile, to satisfy various dimming levels, enhanced negative ADO-OFDM (eNADO-OFDM) is investigated and combined with eADO-OFDM for multiplexing transmission. By adjusting the proportion of these two signals, the dimming control scheme can be achieved, while the entire dynamic range of light-emitting diodes is exploited. In order to achieve superior transmission performance, the optimal power allocation under the desired dimming level is studied to minimize the overall bit error rate (BER). Moreover, to obtain more accurate estimation, an iterative receiver with interference cancellation, in which the pairwise averaging and pairwise clipping are exploited, is proposed. The simulation results show that the proposed scheme can effectively carry out the dimming control with wide dimming range for illumination and achieve superior BER performance at the same signalto-noise ratio compared to the conventional counterparts, while only a few iterations are required. INDEX TERMS Visible light communications (VLC), enhanced asymmetrically clipped DC biased optical OFDM (eADO-OFDM), interference cancellation, power allocation, dimming control.
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