1,721,429 research outputs found
An adaptive bilateral negotiation model for e-commerce settings
No full textThis paper studies adaptive bilateral negotiation between software agents in e-commerce environments. Specifically, we assume that the agents are self-interested, the environment is dynamic, and both agents have deadlines. Such dynamism means that the agents’ negotiation parameters(such as deadlines and reservation prices) are functions of both the state of the encounter and the environment. Given this, we develop an algorithm that the negotiating agents can use to adapt their strategies to changes in the environment in order to reach an agreement within their specific deadlines and before the resources available for negotiation are exhausted. In more detail, we formally define an adaptive negotiation model and cast it as a Markov Decision Process. Using a value iteration algorithm, we then indicate a novel solution technique for determining optimal policies for the negotiation problem without explicit knowledge of the dynamics of the system. We also solve a representative negotiation decision problem using this technique and show that it is a promising approach for analyzing negotiations in dynamic settings. Finally, through empirical evaluation, we show that the agents using our algorithm learn a negotiation strategy that adapts to the environment and enables them to reach agreements in a timely manner
Learning to negotiate optimally in non-stationary environments.
Get PDFWe Adopt the Markov chain framework to model bilateral negotiations among agents in dynamic environments and use Bayesian learning to enable them to learn an optimal strategy in incomplete information settings. Specifically, an agent learns the optimal strategy to play against an opponent whose strategy varies with time, assuming no prior information about its negotiation parameters. In doing so, we present a new framework for adaptive negotiation in such non-stationary environments and develop a novel learning algorithm, which is guaranteed to converge, that an agent can use to negotiate optimally over time. We have implemented our algorithm and shown that it converges quickly in a wide range of cases
Development of g-functions for large diameter shallow bore helical ground heat exchangers
No full textIn this paper, a new approach to calculate the transfer functions (g-functions) for simulating the thermal performance of large diameter, shallow bore helical Ground Heat Exchangers (He-GHE) is proposed using mean fluid temperature rather than borewall temperature. The g-functions are generated using a validated numerical Capacitance Resistance Model-Helical GHE (CaRM-He) for different bore diameters, bore depth and helical pipe pitch. Mathematical formulation is presented which allows calculation of the combined g-function for multiple bores using the g-functions for individual cases. A simplified resistance-based model which enables the calculation of traditional borewall temperature-based g-functions using the mean fluid g-functions for different mass flowrates is also presented. Finally, mean fluid temperature is calculated for an array of eight He-GHEs for Sacramento climate zone using (a) CaRM-He model, (b) mean fluid temperature-based g-function and (c) borewall temperature-based g-functions for maximum (0.128 kg s−1), reference (0.063 kg s−1) and minimum (0.057 kg s−1) mass flowrates. For the reference mass flowrate case, the predicted mean fluid temperature Root Mean Square Deviation (RMSD) between the CaRM-He simulation and the g-function approaches is less than 5% and 6% of the yearly average temperature difference between the inlet and outlet for the mean fluid and borewall based g-functions respectively. For the other mass flowrates, the RMSD in mean fluid temperature varies between 9% and 17% of the yearly average temperature difference between the inlet and outlet temperature. Overall, the proposed g-function approach can be used effectively to estimate the performance of large diameter helical GHEs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Exploiting district cooling network and urban building energy modeling for large-scale integrated energy conservation analyses
No full textResearch effort in analyzing the energy consumption of buildings in districts or cities is increasing as new paradigms of distributed energy production and sharing are spreading. In this work, the Urban Building Energy Model of the Quad, an area of the University of California Davis campus, is presented, validated, and analyzed for possible actions to reduce the district cooling energy consumption. Energy conservation measures involve buildings' air handling units and district chilled water generation. To investigate this system, a district cooling networks module has been developed in EUReCA, the Urban Building Energy Modeling tool used for the analyses. The model has been validated with energy demand and temperature data from 2018 to 2020, resulting in a district cooling demand deviation lower than 7% for 2018 and 2019. Normalized Root Mean Square Error is lower than 35% for each building, proving the reliability at the hourly time scale. Systems energy reduction actions like heat recovery units' installation and heuristic control of the air supply cooling temperature are beneficial in reducing the cooling demand, and they allow a more efficient discharging of the chilled water storage, reducing the average electricity price by load shifting during peak demand
A revised capacitance resistance model for large diameter shallow bore ground heat exchanger
No full textGround heat exchangers (GHE) for residential heat pumps have the advantage of rejecting (extracting) heat to a lower (higher) temperature sink (source) as compared with air source heat pumps. The thermal performance of shallow GHEs with larger diameter and of helical shape is modelled in this study using both a lumped parameter numerical model and a commercially available computational fluid dynamics (CFD) software. Measurements in a real test site single-family residence are also used for soil property calibration. The lumped parameter numerical model (Capacitance Resistance Model, CaRM) is validated against the CFD simulation results and improved in order to capture detailed heat transfer processes within the core of the GHE. As result, the new CaRM model is able to better simulate the thermal behaviour of the helical GHE without high computational resources of the CFD model. Detailed local and global temperatures predicted by the numerical models are presented and discussed. Results indicate that the new CaRM tool better matches the trend of the CFD model. The average root-mean-square deviation between the revised CaRM and CFD models are 0.29 °C for the average core temperature and 0.75 °C for the borewall temperature which is an improvement of 27% and 35% respectively, in comparison to the previous version of CaRM
Techno-economic parametric analysis of large diameter shallow ground heat exchanger in California climates
No full textA parametric study of a large diameter, shallow bore ground heat exchanger system coupled to a water-to-air heat pump is presented. The performance of this system is compared to an equivalent air-to-air heat pump system. Building loads from a single-family home in two different climate zones with different magnitudes and ratio of winter and heating loads are used in this study. In the first climate zone (Sacramento, CA), the winter load is two times the summer load while in the second climate zone (Riverside, CA), the winter and heating loads are nearly balanced. A validated capacitance–resistance numerical model (CaRM-HP) is used to model the heat transfer from the ground heat exchanger. System performance and installation costs are evaluated for varied parameters including borehole diameter of the helical coil, depth of helical coil, spacing, and configuration of the bore field. For all configurations considered, the ground-source heat pump system consumes less electricity annually than the air-source case. The GHE with 40.6 cm (16 in.) helix diameter, 6.09 m (20 ft) helix depth borehole, 1.27 cm (1⁄2 in.) nominal tubing diameter with bore backfilled with sand results in the lowest installed cost relative to saved energy for the analysed climate zones. For Sacramento, this configuration results in an installed cost 4.74/kWh saved per year and saved 28.5% of the electricity consumed by the air-source system. The installed cost of the He-GHE is compared against that of a photovoltaic array with and without battery storage on a time-dependent valuation energy basis
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