Accurate performance analysis of single and opportunistic AF relay cooperation with imperfect cascaded channel estimates

Given the significant gains that relay-based cooperation promises, the practical problems of acquisition of channel state information (CSI) and the characterization and optimization of performance with imperfect CSI are receiving increasing attention. We develop novel and accurate expressions for the symbol error probability (SEP) for fixed-gain amplify-and-forward relaying when the destination acquires CSI using the time-efficient cascaded channel estimation (CCE) protocol. The CCE protocol saves time by making the destination directly estimate the product of the source-relay and relay-destination channel gains. For a single relay system, we first develop a novel SEP expression and a tight SEP upper bound. We then similarly analyze an opportunistic multi-relay system, in which both selection and coherent demodulation use imperfect estimates. A distinctive aspect of our approach is the use of as few simplifying approximations as possible, which results in new results that are accurate at signal-to-noise-ratios as low as 1 dB for single and multi-relay systems. Using insights gleaned from an asymptotic analysis, we also present a simple, closed-form, nearly-optimal solution for allocation of energy between pilot and data symbols at the source and relay(s).

Albumin-mediated incorporation of water-insoluble therapeutics in layer-by-layer assembled thin films and microcapsules

The present study demonstrates a method to deliver hydrophobic drugs by incorporation into thin films and microcapsules fabricated via a layer-by-layer assembly approach. The hydrophobic molecule binding properties of albumin have been exploited for solubilization of a water-insoluble molecule, pyrene (model drug), by preparation of non-covalent conjugates with bovine serum albumin (BSA). Conjugation with BSA renders a highly negative zeta potential to the previously uncharged pyrene which favors the assembly formation by electrostatic interaction with a positively charged polyelectrolyte, chitosan (at acidic pH). The growth of the assembly was followed by monitoring pyrene absorbance with successive layer deposition. The thin film assembly was demonstrated to be capable of releasing its hydrophobic cargo under physiological conditions. We demonstrated the applicability of this approach by encapsulating a water-insoluble drug, curcumin. These assemblies were further loaded with the anti-cancer drug Doxorubicin. Biocompatible calcium carbonate microparticles were used for capsule preparation. The porous nature of the microparticles allows for the pre-encapsulation of therapeutic macromolecules like protein. The fabrication of protein encapsulated stable microcapsules with hydrophobic molecules incorporated into the shell of the microcapsules has been demonstrated. The microcapsules were further capable of loading hydrophilic molecules like Rhodamine B. Thus, using the approach described, a multi-agent carrier for hydrophobic and hydrophilic drugs as well as therapeutic macromolecules can be envisioned.

Estimation of intrinsic diffusion coefficients in a pseudo-binary diffusion couple

Major drawback of studying diffusion in multi-component systems is the lack of suitable techniques to estimate the diffusion parameters. In this study, a generalized treatment to determine the intrinsic diffusion coefficients in multi-component systems is developed utilizing the concept of a pseudo-binary approach. This is explained with the help of experimentally developed diffusion profiles in the Cu(Sn, Ga) and Cu(Sn, Si) solid solutions. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pattern-Formation During Self-organization in Three-Phase Eutectic Solidification

Eutectic growth is an interesting example for exploring the topic of pattern-formation in multi-phase systems, where the growth of the phases is coupled with the diffusive transport of one or more components in the melt. While in the case of binary alloys, the number of possibilities are limited (lamellae, rods, labyrinth etc.), their number rapidly increases with the number of components and phases. In this paper, we will investigate pattern formation during three-phase eutectic solidification using a state-of-the art phase-field method based on the grand-canonical density formulation. The major aim of the study is to highlight the role of two properties, which are the volume fraction of the solid phases and the solid-liquid interfacial energies, in the self-organization of the solid phases during directional growth. Thereafter, we will show representative phase-field simulations of a micro-structure in a real alloy (Ag-Al-Cu) using an asymmetric phase diagram as well as interfacial properties.

Estudo teórico e experimental da velocidade do som em sistemas contendo hidrocarbonetos

A descoberta de reservatórios de petróleo na camada do pré-sal abriu novas perspectivas para a economia brasileira. A grandes profundidades, com elevado teor de CO2 e submetidos a altas pressões e temperaturas, a exploração de petróleo das camadas de pré-sal constitui um considerável desafio tecnológico. Neste contexto, o conhecimento dos coeficientes de compressibilidade são fundamentais para o estudo do comportamento termodinâmico e escoamento dos fluidos destes campos de produção. Com este objetivo, foram determinadas experimentalmente nesta dissertação a massa específica e a velocidade do som de sistemas envolvendo quatro hidrocarbonetos puros: n-decano, n-hexadecano, decalina e tetralina, assim como para sistemas multicompostos envolvendo estes hidrocarbonetos e para uma amostra de condensado de petróleo. Os resultados obtidos permitiram o cálculo dos coeficientes de compressibilidade isentrópica, isotérmica e isentálpica. É apresentada uma avaliação sobre a capacidade de se correlacionar dados experimentais de velocidade do som aos dados calculados pelas equações de estado de Peng-Robinson e Lee-Kesler com regras de mistura: (i) Spencer e Danner e (ii) Lee-Kesler

Agrupamento espacial em robótica de enxame.

Os Sistemas Multi-Robôs proporcionam vantagens sobre um robô individual, quando da realização de uma tarefa com maiores velocidade, precisão e tolerância a falhas. Os estudos dos comportamentos sociais na natureza têm permitido desenvolver algoritmos bio-inspirados úteis na área da robótica de enxame. Seguindo instruções simples e repetitivas, grupos de robôs, fisicamente limitados, conseguem solucionar problemas complexos. Quando existem duas ou mais tarefas a serem realizadas e o conjunto de robôs é heterogêneo, é possível agrupá-los de acordo com as funcionalidades neles disponíveis. No caso em que o conjunto de robôs é homogêneo, o agrupamento pode ser realizado considerando a posição relativa do robô em relação a uma tarefa ou acrescentando alguma característica distintiva. Nesta dissertação, é proposta uma técnica de clusterização espacial baseada simplesmente na comunicação local de robôs. Por meio de troca de mensagens entre os robôs vizinhos, esta técnica permite formar grupos de robôs espacialmente próximos sem precisar movimentar os robôs. Baseando-se nos métodos de clusterização de fichas, a técnica proposta emprega a noção de fichas virtuais, que são chamadas de cargas, sendo que uma carga pode ser estática ou dinâmica. Se uma carga é estática permite determinar a classe à qual um robô pertence. Dependendo da quantidade e do peso das cargas disponíveis no sistema, os robôs intercambiam informações até alcançar uma disposição homogênea de cargas. Quando as cargas se tornam estacionárias, é calculada uma densidade que permite guiar aquelas que estão ainda em movimento. Durante as experiências, foi observado visualmente que as cargas com maior peso acabam se agrupando primeiro enquanto aquelas com menor peso continuam se deslocando no enxame, até que estas cargas formem faixas de densidades diferenciadas para cada classe, alcançando assim o objetivo final que é a clusterização dos robôs.

gcs-ma: a group communication system for mobile agents

Reliable messaging is a key component necessary for mobile agent systems. Current researches focus on reliable one-to-one message delivery to mobile agents. But how to implement a group communication system for mobile agents remains an open issue, which is a powerful block that facilitates the development of fault-tolerant mobile agent systems. In this paper, we propose a group communication system for mobile agents (GCS-MA), which includes totally ordered multicast and membership management functions. We divide a group of mobile agents into several agent clusters,and each agent cluster consists of all mobile agents residing in the same sub-network and is managed by a special module, named coordinator. Then, all coordinators form a ring-based overlay for interchanging messages between clusters. We present a token-based algorithm, an intra-cluster messaging algorithm and an inter-cluster migration algorithm to achieve atomicity and total ordering properties of multicast messages, by building a membership protocol on top of the clustering and failure detection mechanisms. Performance issues of the proposed system have been analysed through simulations. We also describe the application of the proposed system in the context of the service cooperation middleware (SCM) project.

燕沟基本农田粮食稳产高产综合配套技术及试验示范

提出了以新修梯田耕作栽培技术和作物抗旱节水技术为中心的燕沟流域基本农田粮食高产综合配套技术体系 ,并在燕沟流域经过 3年试验示范 ,使粮食生产潜力实现率由原来的 2 3%～ 48% ,平均已达到 5 4 %～ 64% ,典型的抗旱节水综合试验示范地块的潜力实现率提高到 78%～ 87% ;作物平均单产和水分利用效率较原来分别提高了 63%和 5 9.1 % ,粮食单产平均较 1 997年翻了两番 ,粮食产量较 1 997年提高了 33.7%～ 62 .1 % ,人均产粮达到了 5 0 0 kg以上 ,基本实现了减地不减产和增产增效的效果

灾难救援机器人研究现状、关键性能及展望

对日本、美国和中国等国家灾难救援机器人的研究现状和研究计划进行综述。根据世界各国救援机器人技术的研究现状,结合救援机器人在实际应用中取得的经验和教训,归纳和总结出救援机器人的关键性能为：存活能力、运动能力、感知能力、通信能力和作业能力。研究结果表明,灾难救援机器人研究逐步从试验研究转入到实际应用,多种技术融合化、多智能体网络化是今后灾难救援机器人研究的发展方向。防灾、减灾和救灾事关人民生命和财产安全,是国家公共安全的重要组成部分。救援机器人技术是国家发展迫切需要的战略必争的核心技术之一,将在国民经济和安全中起着重要作用并具有重大的战略意义。

基于数字制造环境的可重构装配线仿真分析平台

以某汽车变速箱装配生产线制造系统为背景,应用多Agent制造及Holon制造模式改造传统装配生产线以提升其柔性与重构能力·针对基于agent与holon混合思想的可重构装配生产线的基础框架与实现等理论提供分析验证环境,提出应用数字制造技术构建面向可重构装配线的数字仿真验证平台·在分析面向重构装配线的仿真平台功能特征的基础上,构建了数字仿真验证平台的框架·研究了仿真平台开发中的系统集成、可视化仿真、可重构装配线性能分析等关键技术,最后给出了仿真平台的实例系统·

一个面向异构多UUV协作任务的分层式控制系统

针对异构多UUV协作任务,提出了基于多智能体系统的分层式体系结构(MAHA).在个体层面,将UUV智能体的思维状态分为社会心智和个体心智两个层次分别实现,更加符合人类社会协作模式;在群体层面,提出了复杂海洋环境下UUV群体结构的评价准则,并据此将MAHA与现有结构进行了对比分析.此外,利用面向对象的Petri网理论建立了系统的协作模型,有效降低了系统建模的复杂性.最后,水下多目标搜索使命的实例研究表明,MAHA能够保证异构UUV之间进行有效的协作.

基于多代理和规则调度的敏捷调度系统研究

研究了在敏捷制造环境下制造车间生产过程的动态调度问题。针对敏捷化调度的特殊要求 ,提出了综合运用多代理机制与规则调度实现敏捷化制造车间生产过程动态调度的方法 ,建立了基于多代理生产组织和运行模式的生产过程动态调度系统框架结构 ,研究了在多代理结构的基础上实现规则调度的方法 ,创建了适应实际生产环境的代理的模型结构 ,并以一类敏捷加工车间动态调度的仿真研究说明所提出方法的思路和可行性。

基于KQML语言的合同网协议模型及实现

本文首先分析了基于 KQML会话的 Multi- Agent系统 ( MAS)构成及其特点 ,然后提出了基于 CORBA、KQML的合同网协议 ( CNP)系统模型及 Agent通信模型 ,并针对此合同网模型 ,结合调度系统实例分析了其中 KQML语言的形式化表达方式