When Does Communication Learning Need Hierarchical Multi-Agent Deep Reinforcement Learning

Abstract

Multi-agent systems need to communicate to coordinate a shared task. We show that a recurrent neural network (RNN) can learn a communication protocol for coordination, even if the actions to coordinate are performed steps after the communication phase. We show that a separation of tasks with different temporal scale is necessary for successful learning. We contribute a hierarchical deep reinforcement learning model for multi-agent systems that separates the communication and coordination task from the action picking through a hierarchical policy. We further on show, that a separation of concerns in communication is beneficial but not necessary. As a testbed, we propose the Dungeon Lever Game and we extend the Differentiable Inter-Agent Learning (DIAL) framework. We present and compare results from different model variations on the Dungeon Lever Game.     

Quantitative evaluation of pancreatic enhancement during dual-phase helical CT

PURPOSE: To determine the improvement in pancreatic enhancement at helical computed tomography (CT) performed with an early delay after administration of contrast material compared with that performed with a standard delay. MATERIALS AND METHODS: Dual-phase helical CT of the abdomen was performed in 120 patients with a 150-mL bolus of contrast material infused at 5 mL/sec. Early and standard delayed scanning was performed beginning at 20 seconds and 49-71 seconds, respectively. Regions of interest were measured in the head, body, and tail of the pancreas in 92 patients. The difference in enhancement between early and standard delayed scanning was calculated. RESULTS: Mean pancreatic enhancement was 82 HU +/- 3 (standard error) with an early delay, whereas enhancement on standard delay scans was 62 HU +/- 2 (P < .001). An improvement in enhancement greater than 10 HU was attained in 66 of 92 cases (72%). CONCLUSION: Pancreatic enhancement at helical CT with an early delay after contrast material administration is often significantly greater than the enhancement seen with a standard delay when a monophasic, rapidly infused bolus of contrast material is used.     

Isolation and characteristics of a protein-polysaccharide complex, secreted by Bifidobacterium adolescentis

Although self-help/mutual-help groups, like Alcoholics Anonymous, are important factors in the recovery of many chemically dependent individuals, the large dropout rates from such groups and the awareness that many who drop out do not return to dependent behavior raises interesting questions about other paths to sustained abstinence and recovery. Current emphasis on treatment outcome studies provides a means for researching factors in both those who recover with and without the assistance of self-help/mutual-help groups. The authors suggest some questions which might be investigated.     

Durability of polymeric glazing materials for solar applications

The economic viability of solar collector systems for domestic hot water (DHW) generation is strongly linked to the cost of such systems. Installation and hardware costs must be reduced by 50% to allow significant market penetration. An attractive approach to cost reduction is to replace glass and metal parts with less expensive, lighter weight polymeric components. Weight reduction decreases the cost of shipping, handling, and installation. The use of polymeric materials also allows the benefits and cost savings associated with well established manufacturing processes, along with savings associated with improved fastening, reduced part count, and overall assembly refinements. A key challenge is to maintain adequate system performance and assure requisite durability for extended lifetimes. Results of preliminary and ongoing screening tests for a large number of candidate polymeric glazing materials are presented. Based on these results, two specific glazings with moderate and poor weathering stability are selected to demonstrate how a service lifetime methodology can be applied to accurately predict the optical performance of these materials during in-service use. A summary is given for data obtained by outdoor exposure and indoor testing of polyvinyl chloride (PVC) and high temperature modified polycarbonate copolymer (coPC) materials, and an initial risk analysis is given for the two materials. Screening tests and analyses for service lifetime prediction are discussed. A methodology that provides a way to derive correlations between degradation experienced by materials exposed to controlled accelerated laboratory exposure conditions and materials exposed to in-service conditions is given, and a validation is presented for the methodology based upon durability test results for PVC and coPC.     

Factors affecting contrasting results between self-reported and performance-based levels of physical limitation

Molecular electrostatic potential (MEP) maps of certain 3-methoxy flavone derivatives having different anti-picornavirus activities have been studied. Geometries of the molecules were optimised and charge distributions computed using the AM1 molecular orbital method. Hybridization displacement charges (HDC) were combined with the L?wdin charge distributions to compute the MEP maps. Reliability of the method of computing MEP maps was tested by studying certain other molecules for which ab initio MEP results are available. The anti-picornavirus activities of the flavones have been shown to be related with negative MEP values in two regions, one near the 3-methoxy group and another in a diagonally opposite region near the substituent attached to the C7 atom of the molecules.     

Automated information system for controlling the sociopsychological adaptation of junior grade schoolchildren during learning activities

Acute graft rejection and delayed function are considered to be the major risk factors of short-term as well as long-term graft survival. We studied the impact of these factors on graft outcome among 109 renal transplant recipients. All recipients were treated with triple drug protocol. The recipients were divided into two groups: I group included 57 patients with delayed graft function (DGF), II group included 52 patients with immediate graft function (IGF). We studied graft survival, incidence of acute rejection, serum creatinine levels and the cause of graft loss for patients in both groups. Acute rejection episodes occurred in 49% of patients from DGF group and 45% of patients from IGF group. Graft survival in IGF group was better than in DGF group. Actuarial graft survival at 1, 2, 3 and 4 years in examined groups was 84%, 82%, 72%, 65% vs. 92%, 86%, 84%, 84%, respectively. One-year graft survival in patients with acute rejection from DGF group and IGF group was significantly lower than in patients who remained rejection free (69%, 74% vs. 94%, 96%). We concluded that delayed graft function decreases long-term graft survival, while immediate graft function has an excellent impact on graft outcome. Acute graft rejection is the strongest risk factor of graft loss.