Hybrid Model for Short-Term Water Demand Forecasting Based on Error Correction Using Chaotic Time Series

open access articleShort-term water demand forecasting plays an important role in smart management and real-time simulation of water distribution systems (WDSs). This paper proposes a hybrid model for the short-term forecasting in the horizon of one day with 15 minute time steps, which improves the forecasting accuracy by adding an error correction module to the initial forecasting model. The initial forecasting model is firstly established based on the least square support vector machine (LSSVM), the errors time series obtained by comparing the observed values and the initial forecasted values is next transformed into chaotic time series, and then the error correction model is established by the LSSVM method to forecast errors at the next time step. The hybrid model is tested on three real-world district metering areas (DMAs) in Beijing, China, with different demand patterns. The results show that, with the help of the error correction module, the hybrid model reduced the mean absolute percentage error (MAPE) of forecasted demand from (5.64%, 4.06%, 5.84%) to (4.84%, 3.15%, 3.47%) for the three DMAs, compared with using LSSVM without error correction. Therefore, the proposed hybrid model provides a better solution for short-term water demand forecasting on the tested cases

Seismic Performance Assessment of Water Distribution Systems Based on Multi-Indexed Nodal Importance

open access articleSeismic performance assessment of water distribution systems (WDSs) based on hydraulic simulation is essential for resilience evaluation of WDSs under earthquake disasters. The assessment is mainly to determine how the water supply will be affected due to pipe breaks caused by the earthquake, with the water supply loss estimated based on the loss of supply to nodes. Existing research works usually use the average or overall performance metric of all user nodes as the system performance indicator without considering user nodes' individual performance and criticality. This paper proposes a framework to evaluate the importance of user nodes considering post-earthquake rescue service and the seismic performance of individual user nodes in the WDS, which supports the pipeline renovation plan to improve the performance of critical user nodes. The importance of user nodes is evaluated by a multi-index model, including the indices for daily service, post-earthquake rescue service, and network topology influence of user nodes. These indices evaluate the importance of user nodes in terms of their roles for daily water service, emergent rescue service, and water transmission to other nodes, respectively. Fragility model of pipelines evaluates the earthquake-induced damages of the WDS, and the seismic performance assessment of the WDS system is performed by the hydraulic model of the WDS with pipeline damages. The proposed framework is implemented in an actual WDS; the results show that the importance classification to user nodes by multi-index approach can identify the critical user nodes for post-earthquake rescue service, which traditional methods may ignore. The importance classification and seismic performance of individual user nodes make it feasible to check the seismic performance of critical user nodes and formulate a targeted pipeline renovation plan to focus limited resources on critical user nodes

Seismic Resilience Enhancement of Urban Water Distribution System Using Restoration Priority of Pipeline Damages

The malfunction of the water distribution system (WDS) following severe earthquakes have significant impacts on the post-earthquake rescue. Moreover, the restoration priority of earthquake-induced pipeline damages plays an important role in improving the post-earthquake serviceability of WDS and the “seismic resilience”. Thus, to enhance the seismic resilience of WDS, this study develops a dynamic cost-benefit method and introduces three existing methods to determine the restoration priority of pipeline damages based on a quantitative resilience evaluation framework. In this resilience evaluation framework, the restoration priority is firstly determined. Then the time-varying performance of post-earthquake WDS is modeled as a discrete event dynamic system. In this model, the system state changes after the reparation of pipeline damage, and the system performance is simulated by a hydraulic model to be consistent with the system state. In this study, this method is also tested and compared with other existing methods, and the results show that the system resilience corresponding to the restoration priority obtained by this method is close to that obtained by the global optimization method with a relative difference of less than 3%, whereas the calculation complexity is about 0.4% of the optimization model. It is concluded that this proposed method is valid

Growth Characteristics of Different Exopalaemon carinicauda Populations Under Low and High Salinity Conditions

【Objective】In order to explore the growth characteristics of Exopalaemon carinicauda under different salinity conditions, the growth patterns and relationship between body length and body weight were compared to provide references for the healthy breeding of E. carinicauda.【Method】The growth parameters of E. carinicauda under lowsalinity (5.0 ‰ ±1.0 ‰) and high-salinity (22.0 ‰ ±1.0 ‰) conditions were analyzed, including body length and body weight.【Result】(1) The growth trends of E. carinicauda populations from Fengxian and Ninghai were rather similar, which grew faster under low-salinity model. The average daily increments of body length and body weight of Fengxian population were 0.0203 cm and 0.0194 g under high-salinity model, while those were 0.0252 cm and 0.0265 g under lowsalinity model; the average daily increments of body weight of Ninghai population under high-salinity model and low-salinity model were 0.0183 g and 0.0254 g, which were slower than those of Fengxian population; (2) The relationship between body length and body weight of E. carinicauda populations from Fengxian and Ninghai was correlated as the power function, and their regression equations were: Fengxian population under high-salinity model: W=0.024L2.731 (R2=0.971), Fengxian population under low-salinity model: W=0.023L2.765 (R2=0.992), Ninghai population under high-salinity model: W=0.022L2.807 (R2=0.993), Ninghai population under low-salinity model: W=0.028L2.643 (R2=0.990). All of their b values were less than 3, which showed allometric growth patterns; (3) There were linear relationships between body length and breeding time in Fengxian and Ninghai populations under two salinity models, while power function relationships between body weight and breeding time under low-salinity model, in which the index function of Fengxian population was: Y=0.500e0.014t (R2=0.971), and that of Ninghai population was: Y=0.017t1.0148 (R2=0.977); (4) The trends of fullness of E. carinicauda populations were similar, which were highest at the beginning of the experiment and then gradually decreased to the lowest in the 150 day-age.【Conclusion】In general, the experimental populations under low-salinity breeding environment grow significantly faster than they do under high-salinity breeding environment, and low-salinity model is more conducive to their growth and reproduction

Lyophilization-Free Approach to the Fabrication of Conductive Polymer Foams Enabling Photo-Thermo-Electrical-Induced Cell Differentiation under Global Illumination

In this study, we fabricate conductive polymer (PEDOT:PSS) foams with tunable density and mechanical properties via a new and efficient lyophilization-free method and use asymmetric acid treatment to create a PEDOT:PSS scaffold with asymmetric light absorptivity, which helps generate the asymmetric photo-thermo-electrical conversion under simple global illumination. Distinct light absorptivity along the scaffold has been proved to be related to the different doping states via asymmetric acid treatment. Such noninvasive photo-thermo-electrical stimulation significantly induces the expressions of genes related to neural differentiation under an illumination intensity of 240 mW/cm2 for only 30 min. This research will not only provide a new approach to fabricate conductive polymer foams via the lyophilization-free method but also enable the global illumination to provoke the photo-thermo-electrical effect of conductive polymers with asymmetric light absorptivity for thermoelectric conversion and biomedical potential applications in tissue engineering for therapeutic purposes