Automated Negotiations under User Preference Uncertainty: A Linear Programming Approach

Autonomous agents negotiating on our behalf find applications in everyday life in many domains such as high frequency trading, cloud computing and the smart grid among others. The agents negotiate with one another to reach the best agreement for the users they represent. An obstacle in the future of automated negotiators is that the agent may not always have a priori information about the preferences of the user it represents. The purpose of this work is to develop an agent that will be able to negotiate given partial information about the user’s preferences. First, we present a new partial information model that is supplied to the agent, which is based on categorical data in the form of pairwise comparisons of outcomes instead of precise utility information. Using this partial information, we develop an estimation model that uses linear optimization and translates the information into utility estimates. We test our methods in a negotiation scenario based on a smart grid cooperative where agents participate in energy trade-offs. The results show that already with very limited information the model becomes accurate quickly and performs well in an actual negotiation setting. Our work provides valuable insight into how uncertainty affects an agent’s negotiation performance, how much information is needed to be able to formulate an accurate user model, and shows a capability of negotiating effectively with minimal user feedback

Fate and occurrence of alkylphenolic compounds in sewage sludges determined by liquid chromatography tandem mass spectrometry

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2009 Taylor & Francis.An analytical method has been developed and applied to determine the concentrations of the nonionic alkylphenol polyethoxylate surfactants and their metabolites, alkylphenoxy carboxylates and alkyphenols, in sewage sludges. The compounds were extracted with methanol/acetone (1:1 v/v) from sludge, and concentrated extracts were cleaned by silica solid‐phase extraction prior to determination by liquid chromatography tandem mass spectrometry. The recoveries, determined by spiking sewage sludge at two concentrations, ranged from 51% to 89% with method detection limits from 6 µg kg−1 to 60 µg kg−1. The methodology was subsequently applied to sludge samples obtained from a carbonaceous activated sludge plant, a nitrifying/denitrifying activated sludge plant and a nitrifying/denitrifying activated sludge plant with phosphorus removal. Concentrations of nonylphenolic compounds were two to three times higher than their octyl analogues. Long‐chain nonylphenol polyethoxylates (NP3–12EO) ranged from 16 µg kg−1 to 11754 µg kg−1. The estrogenic metabolite nonylphenol was present at concentrations ranging from 33 µg kg−1 to 6696 µg kg−1.Public Utilities Board of Singapore, Thames Water and Yorkshire Water

Comparison of a PWM Inverter and a Multilevel Inverter using the Switching Function Analysis for Harmonic Content and Efficiency

A conventional 3-level PWM Inverter and a Cascaded Multilevel Inverter, both rated at 230Vrms voltage output and 3KW are analysed using the Switching Function. The PWM signal for the 3-level inverter is derived by applying the Switching Function Technique to the equal area principle. For the Cascaded Multilevel Inverter the Switching Function Technique is initially applied to each H-bridge, and then added to derive the overall Switching Function for the Multilevel Inverter output. A new technique is employed to derive the pulse width of each H-bridge converter in order to construct the output voltage. Voltage expressions of the output voltages are derived for both topologies. The switching frequency is chosen to be the same for both inverters. To ensure the same number of commutations over a fundamental cycle for both inverters, the levels of the Multilevel Inverter must be properly selected to meet the PWM frequency of the conventional inverter. Frequency spectrum and expressions of THD of the output voltage are derived. The two inverters are compared in terms of THD and harmonic content of the output voltage. The efficiency is concluded from the number of switching instances and other parameters of the circuit

A solid-state fault current limiting and interrupting device (FCLID) with power factor correction

A Solid-State Fault Current Limiter and interrupting device (FCLID) with power factor correction suitable for low-voltage distribution networks employing the Switched Capacitor (SC) Circuit is presented. Some design parameters are investigated and some optimisation is applied. In this application the Switched Capacitor (SC) is inserted in series with the supply line via an isolating transformer, providing both power factor correction and limitation of the current to a pre-set value in the event of a fault. Interruption of the fault is also possible by setting both semiconductor switches in the off state. The voltage across the load is increased. Optimisation is applied to correct the power factor to an acceptable value of 0.85 and keep the load voltage within acceptable limits. Losses are estimated and rating of components is discussed

Supercapacitor application for PV power smoothing

© 2018 IEEE. The penetration of renewable energy technologies causes grid stability problems and voltage flickering due to fluctuations of the weather conditions, which affect the produced renewable power. The system is first analyzed in order to define the operating point and the controlling parameters, in which the produced power is shared correctly between the load and the grid at a power factor close to unity. The operating point is set by the duty cycle (D) of the DC-DC converter, the depth of modulation (Dm) of the inverter, and the phase angle (δ) between the output voltage of the inverter and the grid voltage. The simulated system is operated in an open-loop mode in order to investigate the effect of each parameter without the corrective action of the closed-loops of the MPPT and the load angle. After that, a preliminary investigation of a supercapacitor controlled storage application is performed in terms of the power flow. All calculated theoretical results are verified by the simulation results. This research forms the basis for an in-depth investigation of supercapacitor and battery storage in grid-connected systems