Learning automata based multi‐agent system algorithms for finding optimal policies in Markov games

Markov games, as the generalization of Markov decision processes to the multi‐agent case, have long been used for modeling multi‐agent systems (MAS). The Markov game view of MAS is considered as a sequence of games having to be played by multiple players while each game belongs to a different state of the environment. In this paper, several learning automata based multi‐agent system algorithms for finding optimal policies in Markov games are proposed. In all of the proposed algorithms, each agent residing in every state of the environment is equipped with a learning automaton. Every joint‐action of the set of learning automata in each state corresponds to moving to one of the adjacent states. Each agent moves from one state to another and tries to reach the goal state. The actions taken by learning automata along the path traversed by the agent are then rewarded or penalized based on the comparison of the average reward received by agent per move along the path with a dynamic threshold. In the second group of the proposed algorithms, the concept of entropy has been imported into learning automata based multi‐agent systems to improve the performance of the algorithms. To evaluate the performance of the proposed algorithms, computer experiments have been conducted. The results of experiments have shown that the proposed algorithms perform better than the existing algorithms in terms of speed and accuracy of reaching the optimal policy. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Pixel circuits and drive schemes for glass and elastic AMOLED displays

Abstract— Flexible AMOLED displays pose unique opportunities and challenges for a‐Si. Leveraging the existing a‐Si process infrastructure is the fastest and lowest‐cost route to flexible AMOLEDs. However, the displays must maintain high performance, long lifetimes, and high uniformity despite low‐temperature processes and mechanical stress. New pixel circuits and drive schemes shown here demonstrate that high‐performance flexible AMOLED displays are possible using well‐established a‐Si technology.     

AMOLED Pixel Circuit With Electronic Compensation of Luminance Degradation

A new voltage-programmed pixel circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) for active-matrix organic light-emitting diodes (AMOLEDs) is presented. In addition to compensating for the shift in threshold voltage of TFTs, the circuit is capable of compensating for OLED luminance degradation by employing the shift in OLED voltage as a feedback of OLED degradation     

Amylopectin Multiple Aldehyde Crosslinked Hydrogel as an Injectable and Self‐Healing Cell Carrier for Bone Tissue Engineering

Despite excellent processing and biological properties of gelatin for use as a cell carrier, none of the gelatin‐based hydrogel cell carriers reported to date offer all characteristics including quick formation, injectability, self‐healing, and durability, which are simultaneously required for an ideal system. Here, a gelatin‐based hydrogel with dynamic Schiff base linkages, so‐called “dynamic hydrogel,” as an injectable cell carrier consisting of gelatin and amylopectin multiple aldehyde (AMPA), with all the required characteristics is reported. Biocompatibility and osteoinductivity of the hydrogel are verified through the culture of human bone marrow‐derived mesenchymal stem cells (hBMSCs). As live/dead results show, hBMSCs are alive and highly viable ≈85–90% within the hydrogel after 5 days. According to bromodeoxyuridine cell proliferation assay, a significant increase in the number of the cells seeded in the hydrogel confirms its clinical significance for cell therapy. Most importantly, histological visualization using Mason's Trichrome staining indicates secretion of extracellular matrix around the cells loaded in the hydrogel and also expression level evaluation of the crucial osteogenic markers, confirms that the hydrogel can provide osteoinductive support for osteocyte differentiation of hBMSCs after 14 days. Therefore, this hydrogel provides more progress on the path toward bone tissue engineering and further treatment of bone diseases.     

An experimental investigation on heat transfer characteristics of multi-walled CNT-heat transfer oil nanofluid flow inside flattened tubes under uniform wall temperature condition

An experimental investigation on heat transfer characteristics of MWCNT-heat transfer oil nanofluid flow inside horizontal flattened tubes has been carried out under uniform wall temperature condition. Nanoparticle weight fractions were 0%, 0.1%, 0.2%, and 0.4%. The copper tubes of 14.5 mm I.D. were flattened and used as the test section of oblong shape with inside heights of 13.4 mm, 11.7 mm, 10.6 mm, and 8.6 mm. The nanofluid flowing inside the tube was heated inside a steam chamber to keep the temperature of the tube wall constant. The required data were acquired for laminar hydrodynamically fully developed regime. The effects of different parameters such as volumetric flow rate, nanoparticle weight fraction, and hydraulic diameter on the heat transfer behavior of the tested systems have been investigated experimentally. For a given flattened tube at a constant nanoparticle weight fraction, increasing volumetric flow rate results in heat transfer enhancement. In addition, as the tube profile becomes more flattened and the hydraulic diameter decreases, the heat transfer coefficient goes up at constant volumetric flow rate. Utilizing nanofluids instead of the base fluid, the heat transfer rate enhances remarkably. The higher the nanoparticles weight fraction, the more the rate of heat transfer enhancement. Finally, the results show that the amount of increase in heat transfer coefficient caused by employing nanofluid instead of the base fluid is comparable to what caused by flattening the tube.     

Effect of applied voltage on jet electric current and flow rate in electrospinning of polyacrylonitrile solutions

BACKGROUND: In the electrospinning process, through subjecting a pendent drop of a polymer solution to a high electric field, a fluid jet is ejected from the drop. To have a stable process, the rate at which the fluid is forced into the drop and the rate at which the fluid is carried away by the jet must be equal. A method is reported to find the point at which the flow into the drop is equal to the flow out of the drop. RESULTS: In the electrospinning of polyacrylonitrile solutions, by applying different voltages at a constant solution feed rate, two jet regimes were observed: stable jet and fluctuating jet regimes. The stable jet regime occurred at low voltages where the jet flow rate was lower than the feed rate, and the fluctuating jet regime occurred at higher voltages where the jet flow rate exceeded the feed rate. The highest voltage in the stable jet regime was the point where the jet flow rate was equal to the feed rate. This point was determined for different feed rates. CONCLUSION: By applying various voltages at different feed rates, and investigating the jet current, a curve showing stable processing points can be obtained. Copyright © 2008 Society of Chemical Industry     

Algorithms for matching 3D line sets

Matching two sets of lines is a basic tool that has applications in many computer vision problems such as scene registration, object recognition, motion estimation, and others. Line sets may be composed of infinitely long lines or finite length line segments. Depending on line lengths, three basic cases arise in matching sets of lines: 1) finite-finite, 2) finite-infinite, and 3) infinite-infinite. Case 2 has not been treated in the literature. For Cases 1 and 3, existing algorithms for matching 3D line sets are not completely satisfactory in that they either solve special situations, or give approximate solutions, or may not converge, or are not invariant with respect to coordinate system transforms. In this paper, we present new algorithms that solve exactly all three cases for the general situation. The algorithms are provably convergent and invariant to coordinate transforms. Experiments with synthetic and real 3D image data are reported.     

Combined heat and power economic dispatch by mesh adaptive direct search algorithm

The optimal utilization of multiple combined heat and power (CHP) systems is a complex problem. Therefore, efficient methods are required to solve it. In this paper, a recent optimization technique, namely mesh adaptive direct search (MADS) is implemented to solve the combined heat and power economic dispatch (CHPED) problem with bounded feasible operating region. Three test cases taken from the literature are used to evaluate the exploring ability of MADS. Latin hypercube sampling (LHS), particle swarm optimization (PSO) and design and analysis of computer experiments (DACE) surrogate algorithms are used as powerful SEARCH strategies in the MADS algorithm to improve its effectiveness. The numerical results demonstrate that the utilized MADS–LHS, MADS–PSO, MADS–DACE algorithms have acceptable performance when applied to the CHPED problems. The results obtained using the MADS–DACE algorithm are considerably better than or as well as the best known solutions reported previously in the literature. In addition to the superior performance, MADS–DACE provides significant savings of computational effort.