Mobile Agents in Interaction Spaces

Mobile agent systems are difficult to reason about and implement efficiently and safely. Theoretical work, most notably process calculi, provide solid semantics for mobile systems. However, the theory is often too abstract to match with the requirements of practical implementations. To fill this gap, intermediate models must be proposed. We present in this paper such a model named Interaction Spaces, a metaphor of geometrical spaces in which agents interact through simple transformations. The framework captures high-level distributed semantics, most notably asynchronous, multicast communications on FIFO channels. It also refines and implements the channel passing feature of the pi-calculus, together with the mobility of agent themselves. Above interaction spaces, we propose a full-fledged agent calculus and its associated operational semantics.     

Agent-based architecture for designing hybrid control systems

When designing very complex control strategy using hybrid technology, one usually faces the challenge of balancing effective realization of multi-control modeling with design simplicity. To better manage this difficulty we have used the agent paradigm as a simple and powerful bridge between asynchronous/distributed computation and Matlab environment. The proposed architecture has been used to design a complex hybrid control environment using multi-objective, fuzzy c-means, and genetic algorithms optimization to design hybrid control strategies suitable for the energy flows management on board of hybrid electric vehicles.     

Analysis of the Activated Sludge Process in an MBR under Starvation Conditions

An aerobic membrane bioreactor (MBR) at complete biomass retention was studied over a period of time under starvation conditions. Kinetic parameters were determined in a no‐feed batch test. The decay rate of activated sludge, k_d = 0.05 d^–1, was determined by tracking the decrease of MLSS. The ratio of MLVSS/MLSS was in the range 0.76–0.85. The pH values were between 7.02 and 8.23. As a function of different initial concentrations of MLSS, specific nitrification rates q_N, decreased from 4.23 to 0.02 mg‐N/(g MLVSS d) and specific biodegradation rates q_b increased from 0.23 to 1.90 mg‐COD/(g MLVSS d). From experimental data the kinetic constants for respiration, which followed Monod kinetics, were determined as q_O2max = 9.8 mg‐O₂/(g MLVSS h), K_x = 2.9 g/dm³. Additionally, a linear correlation between MLSS and mean floc size was found to exist during the biodegradation process.     

Sludge accumulation, characteristics, and pathogen inactivation in four primary waste stabilization ponds in central Mexico

To support the development of safe and feasible sludge management strategies, the accumulation rates of sludge and its characteristics were studied in four primary wastewater stabilization ponds (WSPs) in central Mexico (three facultative and one anaerobic). The accumulation rates and distribution of sludge were determined by measuring the thickness of the sludge layer at 8-40 locations throughout each pond. The average, per capita sludge accumulation rates ranged from 0.021 to 0.036m(3)/person/yr. In the anaerobic pond the sludge distribution was uniform throughout the pond, whereas in the three facultative ponds most of the sludge accumulated directly in front of the inlet. To measure the horizontal and vertical variation in the sludge characteristics, sludge cores were collected from 3 to 7 locations in three of the ponds. Each core was divided into 4 sub-samples in which various physical, chemical, and microbiological parameters were measured. In addition, the inactivation of several pathogen indicator organisms was studied in a batch of sludge for 7 months. Based on the microbiological results, it is concluded that reasonable estimates of the inactivation of fecal coliform bacteria, fecal enterococci, F+ coliphage, somatic coliphage, and Ascaris eggs in WSP sludge in central Mexico can be made using first-order rate constants of 0.1, 0.1, 0.01, 0.001, and 0.001d(-1), respectively. From the observed changes in the concentrations of total solids and the volatile to fixed solids ratio, empirical equations were developed to describe anaerobic degradation and compression, which are the two most important processes affecting the volume of sludge after its deposition.     

Standardized tests fail to assess the effects of antibiotics on environmental bacteria

Pharmaceuticals are designed and used because of their specific biological effects. Over the past decade, compounds from various classes of pharmaceuticals have been detected in the environment. Concern has grown about the adverse effects pharmaceuticals in the environment might potentially have on human and ecological health. A sound risk assessment is therefore urgently needed for pharmaceuticals. Standardized tests for assessing the effects of chemicals on environmental organisms are widely used for this purpose. However it is questionable whether classical standardized tests give reliable data needed for environmental risk assessment. In this study we investigated the suitability of the respiration inhibition test OECD 209 for the assessment of the effects of antibiotics, disinfectants and cytotoxics on sewage sludge bacteria. We found that inhibition concentrations can strongly depend on the test period and the type of compound. We conclude that tests to assess the effects of pharmaceuticals on environmental organisms such as bacteria have to be evaluated before their results can be used in environmental risk assessment.     

A goal-driven and agent-based requirements engineering framework*

The paper presents a requirements engineering framework (REF), where advanced requirements engineering techniques are combined with software quality modelling approaches to provide an environment within which the stakeholders and the analysts can easily cooperate to discover, organise, reconcile and validate the requirements for a new system. By adopting a basic and essential graphical notation, and a clear top-down methodology, REF allows for an effective involvement of the stakeholders, assisting and driving them to an early definition of the desired system's functionalities and quality attributes, while supporting the redesign of the encompassing organisational context to better exploit the new system's capabilities. As a case study, REF is applied to support the requirements engineering process for a complex software-intensive simulation system. Results demonstrate the feasibility of REF and the benefits it offers to the requirements engineering process, but also to the subsequent system development phases. As illustrated through the case study REF can, in fact, be usefully applied as a forerunner for unified modelling language (UML)-based approaches.*Part of this work was completed while the author was Senior Research Fellow with the Computing Information Systems Engineering Group, at the Royal Military College of Science, Cranfield University (UK)     

Dewatering of alumino-humic sludge: impacts of hydroxide

The paper draws together information on factors which influence the conditioning and dewatering behaviour of an alum sludge gained from the coagulation of a low-turbidity coloured water. A principal focus is the potential impact of aluminium hydroxide on the sludge character. Background information is provided on the composition of the source floc for the domain pH 6.0-6.5 and Al>2.0mg/l. From this, there were many pointers to the presence of Al(OH)(3)(s) within the floc. A series of comparisons were made between an alum sludge and a hydroxide suspension at a concentration equivalent to the coagulant fraction within the sludge. The parameters studied included floc size, floc density, polymer adsorption and dewatering behaviour at different time-scales. In all cases, there were strong similarities in the behaviour of the two suspensions-indicating the potential impact of the hydroxide. There was also evidence of common features being displayed by both the organic fractions and the hydroxide. It was suggested that some of the behavioural features might emanate from a common fractal structure within the source floc, the fractal dimension (approximately 1) being insensitive to composition.     

Motivating agents in software tutorials

Pedagogical agents can provide important support for the user in human–computer interaction systems. This paper examines whether a supplementary, motivating agent in a print tutorial can enhance student motivation and learning in software training. The agent served the role of motivator, attending the students to issues of task relevance and self-efficacy. The agent was presented in the tutorial by means of images and written messages. An experiment compared the agent condition with a no-agent (control) condition. Participants were 49 students (mean age 11.3 years) from the upper grades of elementary school. Data on motivation and learning were gathered before, during and after training. The findings revealed that students in the agent condition did significantly better on skills measures during and after training (i.e., performance indicators, posttest, and retention test). In addition, marginally significant differences favoring these students were found for flow experience during training and for motivational gains on task relevance and self-efficacy after training. The design strategies of the motivating agent are considered relevant for the creation of Animated Pedagogical Agents.     

支持电解质对污泥电解效果的影响研究

通过投加不同支持电解质进行污泥电解试验,考察污泥性质随电解时间的变化,分析支持电解质对电化学处理污泥的影响效果。结果表明,NaOH作为电解质时破解效果最佳,电解60min后,污泥SCOD由86.6mg/L升至423.8mg/L,污泥MLSS去除率达15.5%。与直接电解相比,投加支持电解质可以大幅度提升电解污泥的溶胞效果,实现污泥的减量,并改善污泥的沉降性能。     

情景分析下自治个体行为选择模型

研究一种基于情景分析下自治个体行为选择模型.首先,以相互依赖理论为基础,通过对情景的依赖性、一致性、控制性和平衡性等四个情景属性的深入分析,完成了自治个体对场景的分类.然后根根据情景分析在不同情景下的分析结果,对自治个体做出不同的行为选择.实验证明了使用情景分析算法可以有效地对情景进行划分,并有效指导自治个体的行为选择.