Uncertainty in action-value estimation affects both action choice and learning rate of the choice behaviors of rats

The estimation of reward outcomes for action candidates is essential for decision making. In this study, we examined whether and how the uncertainty in reward outcome estimation affects the action choice and learning rate. We designed a choice task in which rats selected either the left-poking or right-poking hole and received a reward of a food pellet stochastically. The reward probabilities of the left and right holes were chosen from six settings (high, 100% vs. 66%; mid, 66% vs. 33%; low, 33% vs. 0% for the left vs. right holes, and the opposites) in every 20–549 trials. We used Bayesian Q-learning models to estimate the time course of the probability distribution of action values and tested if they better explain the behaviors of rats than standard Q-learning models that estimate only the mean of action values. Model comparison by cross-validation revealed that a Bayesian Q-learning model with an asymmetric update for reward and non-reward outcomes fit the choice time course of the rats best. In the action-choice equation of the Bayesian Q-learning model, the estimated coefficient for the variance of action value was positive, meaning that rats were uncertainty seeking. Further analysis of the Bayesian Q-learning model suggested that the uncertainty facilitated the effective learning rate. These results suggest that the rats consider uncertainty in action-value estimation and that they have an uncertainty-seeking action policy and uncertainty-dependent modulation of the effective learning rate

GT2004-53683 OPTIMAL OPERATIONAL PLANNING OF COGENERATION SYSTEMS WITH MICROTURBINE AND DESICCANT AIR-CONDITIONING UNITS

ABSTRACT Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant airconditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning. NOMENCLATURE A : coefficient for unit conversion from J to Wh, Wh/J a : latent heat of vaporization of water, kJ/kg B, C : coefficients of proportion, kg/m b : specific heat at constant pressure of air, kJ/(kg·°C) c : specific heat of water, kJ/(kg·°C) E : electricity, kWh/h F : natural gas consumption, m 3 /h h : specific enthalpy, kJ/kg J : hourly energy charge, yen/h m : mass flow rate, kg/h p, q, r, p′, q′, r′ : performance characteristic values of equipment Q : heat flow rate, kWh/h s : sensible heat factor t : temperature, °C u : input energy flow rate of equipment, m 3 /h, kWh/h v : velocity of process air, m/h x : absolute humidity, kg/kg y : output energy flow rate of equipment, kWh/h δ : binary variable expressing on/off status of operation η c : evaporative effectiveness of EC2 η e : effectiveness on regeneration air side of SHW η s : effectiveness on process air side of SHW ϕ : unit cost of energy charge, yen/m 3 , yen/kWh ( ), ( ) : lower and upper limit

Functional Ingredients Extraction from Garcinia mangostana Pericarp by Liquefied Dimethyl Ether

The mangosteen (Garcinia mangostana Linn.) pericarp contains rich xanthone, a one kind of the polyphenols in the non-edible portion. In recent years, xanthones have been noted as a functionality such as anti-cancer effect and is expected as pharmaceuticals and health supplements. In this work, extraction of xanthones from mangosteen pericarp by using liquefied DME were investigated. Wet powder and cube samples were used as a raw material. Experimental conditions were 35°C, 0.8 MPa with various amounts of sample (1, 3, 6 g). Extracted components were analyzed by using high performance liquid chromatography (HPLC). As a result, it was confirmed that eight kinds of xanthones such as alpha-mangostin, 3-Isomangostin, Mangostanol, 8-Desoxygartanin, Gartanin, Garcinone E, 9-Hydroxycalabaxanthone, beta-Mangostin were extracted. The highest yield of alpha-mangostin (42.9 mg/g_dry sample) was obtained with a powder sample of 6 g loaded. Final alpha-magostin corresponded to about 104% of the ethanol extraction with wet mangosteen pericarp, and 72% of the dried sample. Therefore, it was considered that in the extraction of xanthones from the mangosteen, liquefied DME extraction was valid

Melting of excitonic insulator phase by an intense terahertz pulse in Ta2_2NiSe5_5

In this study, the optical response to a terahertz pulse was investigated in the transition metal chalcogenide Ta$_2$NiSe$_5$, a candidate excitonic insulator. First, by irradiating a terahertz pulse with a relatively weak electric field (0.3 MV/cm), the spectral changes in reflectivity near the absorption edge due to third-order optical nonlinearity were measured and the absorption peak characteristic of the excitonic phase just below the interband transition was identified. Next, by irradiating a strong terahertz pulse with a strong electric field of 1.65 MV/cm, the absorption of the excitonic phase was found to be reduced, and a Drude-like response appeared in the mid-infrared region. These responses can be interpreted as carrier generation by exciton dissociation induced by the electric field, resulting in the partial melting of the excitonic phase and metallization. The presence of a distinct threshold electric field for carrier generation indicates exciton dissociation via quantum-tunnelling processes. The spectral change due to metallization by the electric field is significantly different from that due to the strong optical excitation across the gap, which can be explained by the different melting mechanisms of the excitonic phase in the two types of excitations.Comment: 66 pages, 11 figures, 2 table