Geometry of Policy Improvement

We investigate the geometry of optimal memoryless time independent decision making in relation to the amount of information that the acting agent has about the state of the system. We show that the expected long term reward, discounted or per time step, is maximized by policies that randomize among at most $k$ actions whenever at most $k$ world states are consistent with the agent's observation. Moreover, we show that the expected reward per time step can be studied in terms of the expected discounted reward. Our main tool is a geometric version of the policy improvement lemma, which identifies a polyhedral cone of policy changes in which the state value function increases for all states.Comment: 8 page

A Risk Comparison of Ordinary Least Squares vs Ridge Regression

We compare the risk of ridge regression to a simple variant of ordinary least squares, in which one simply projects the data onto a finite dimensional subspace (as specified by a Principal Component Analysis) and then performs an ordinary (un-regularized) least squares regression in this subspace. This note shows that the risk of this ordinary least squares method is within a constant factor (namely 4) of the risk of ridge regression.Comment: Appearing in JMLR 14, June 201

The comparison of the efficacy of intra-peritoneal instillation along with local infiltration with bupivacaine versus placebo for post-operative analgesia after laparoscopic tubal ligation

Background: Intra-peritoneal instillation of local anesthetics has been shown to minimize post-operative pain after laparoscopic surgeries. The present study was undertaken with the following aim to compare the efficacy of intra-peritoneal instillation and local infiltration with bupivacaine versus placebo for post-operative analgesia after laparoscopic tubal ligation. To correlate the advantages and side effects of the drugs during the procedure. To establish a protocol for the use of bupivacaine instillation and infiltration for post-operative analgesia after laparoscopic tubal ligation.Methods: A prospective study was carried out in a tertiary care hospital attached to a teaching medical institute. Institutional ethics committee approval was obtained for this randomized control study (double blind) including 50 women who will be divided in two groups. Group A will be administered intra-peritoneal bupivacaine along with local infiltration. Group B will be administered normal saline. Post-operative pain will be monitored by a blind observer and rescue analgesia will be administered at visual analogue score of 3.Results: Both the groups were comparable with respect to age and BMI. The mean duration of analgesia in Group A with bupivacaine was 315.60±79.9 min (Median 300 min).  The mean duration of analgesia in Group B with normal saline was 138.20±46.97 min (Median 150 min, p value <0.001).Conclusions: The study depicts a significant pain relief after use of bupivacaine. Bupivacaine instillation in the peritoneal cavity along with local infiltration of the drug gives prolongs pain relief as compared to normal saline

Ethylene-propylene Diene Rubber as a Futuristic Elastomer for Insulation of Solid Rocket Motors

The study carried out so far on the application of ethylene-propylene diene rubber (EPDM)in the field of insulation of case bonded solid rocket motors has been reviewed. The variousstudies by the authors (unpublished work) have also been reported. All these findings bring outthe excellent potential of EPDM as insulator in view of its ageing resistance, low-temperatureflexibility, low erosion rate, and low specific gravity

Effect of fillers and fire retardant compounds on hydroxy terminated polybutadiene based insulators

A series of polyurethane compositions have been formulated using hydroxy-terminated polybutadiene as polymeric binder and carbon black as a major filler. Various binder-to-filler ratios of the formulations were evaluated to get calendered sheets. The formulations have been characterised for pot-life and rollability and the calendered sheets for mechanical and thermal properties, bUm rate, glass transition temperature, shore hardness and density . The different fillers tried were varieties of carbon black as a major filler; metal oxides, silicates and organic compounds; and fire retardants, such as zinc borate, sodium metaborate, ammonium dihydrogen phosphate and antimony trioxide. The structure and morphology of the fillers have been correlated with the properties. The optimised composition has been evaluated in an end-burning motor, as an insulator for case-bonded application, using a typical composite propellant. The results of interface bonding between the propellant and the insulator have also been presented

The Computational Power of Optimization in Online Learning

We consider the fundamental problem of prediction with expert advice where the experts are "optimizable": there is a black-box optimization oracle that can be used to compute, in constant time, the leading expert in retrospect at any point in time. In this setting, we give a novel online algorithm that attains vanishing regret with respect to $N$ experts in total $\widetilde{O}(\sqrt{N})$ computation time. We also give a lower bound showing that this running time cannot be improved (up to log factors) in the oracle model, thereby exhibiting a quadratic speedup as compared to the standard, oracle-free setting where the required time for vanishing regret is $\widetilde{\Theta}(N)$. These results demonstrate an exponential gap between the power of optimization in online learning and its power in statistical learning: in the latter, an optimization oracle---i.e., an efficient empirical risk minimizer---allows to learn a finite hypothesis class of size $N$ in time $O(\log{N})$. We also study the implications of our results to learning in repeated zero-sum games, in a setting where the players have access to oracles that compute, in constant time, their best-response to any mixed strategy of their opponent. We show that the runtime required for approximating the minimax value of the game in this setting is $\widetilde{\Theta}(\sqrt{N})$, yielding again a quadratic improvement upon the oracle-free setting, where $\widetilde{\Theta}(N)$ is known to be tight

Fermionic Molecular Dynamics for nuclear dynamics and thermodynamics

A new Fermionic Molecular Dynamics (FMD) model based on a Skyrme functional is proposed in this paper. After introducing the basic formalism, some first applications to nuclear structure and nuclear thermodynamics are presentedComment: 5 pages, Proceedings of the French-Japanese Symposium, September 2008. To be published in Int. J. of Mod. Phys.

Effect of Additives on Liner Properties of Case-bonded Composite Propellants

A thin layer of liner is applied to ensure a good bond between the insulator and the propellant in case-bonded rocket motors. It also acts as a protective shield for the insulatorby providing a limited fire protection effect. Liner compositions should preferably be based on the same binder system used in the propellant formulations. As the liner has to hold the propellant and the insulator without debond under all the environmental conditions, it plays a key role in predicted performance of a rocket motor. Hence, studies were carried out to improve the liner properties using various hydroxyl compounds, such as butanediol, cardanol, trimethylol propane, pyrogallol, etc as additives. Butanediol and phloroglucinol combination gave the best results in terms of mechanical properties and interface properties for the liner compositions. The effect of filler content on the liner properties was also studied. The results showed that higher filler content does not affect interface properties. Considering the fire retardancy effect and reinforcement of antimony trioxide (S£203), the formulation containing higher Sb2O3 was selected. The studies on pot life/castable life of liner showed that propellant could be cast up to 6 days after liner coating, without adversely affecting the bonding and the bond strength