Characteristics of WWTP sludge after drying in greenhouse for agricultural purposes

The sludge generated by sewage treatment which meets regulatory standards can be used in agriculture. With this understanding, the focus of this study is the evaluation of the agricultural characteristics and inorganic substances in excess activated sludge, which was subjected to drying in a greenhouse. The variables (factor) evaluated during the drying process were: type of sludge (digested or not digested), addition of lime to the sludge, and the physical layout and rotation of sludge in the greenhouse. The parameters monitored for this assessment were moisture, volatile solids and pH. The greenhouse cover and sides were made of translucent plastic to allow the penetration of solar radiation and prevent water from entering. A impermeable floor was used. The sludge was generated in sewage treatment plants located in the metropolitan region of Grande Vitória, Espírito Santo, Brazil. The solar drying of wastewater sludge in a greenhouse presented satisfactory results.     

An upper bound for the distance between a zero and a critical point of a solution of a second order linear differential equation

This paper presents an upper bound for the distance between a zero and a critical point of a solution of the second order linear differential equation (p(x)y^′)^′+q(x)y(x)=0, with p(x),q(x)>0. It also compares it with previous results.     

Robot task plan representation by Petri nets: modelling, identification, analysis and execution

In this paper we introduce a framework to represent robot task plans based on Petri nets. Our approach enables modelling a robot task, analysing its qualitative and quantitative properties and using the Petri net representation for actual plan execution. The overall model is obtained from the composition of simple models, leading to a modular approach. Analysis is applied to a closed loop between the robot controller and the environment Petri net models. We focus here on the quantitative properties, captured by stochastic Petri net models. Furthermore, we introduce a method to identify the environment and action layer parameters of the stochastic Petri net models from real data, improving the significance of the model. The framework building blocks and a single-robot task model are detailed. Results of a case study with simulated soccer robots show the ability of the framework to provide a systematic modelling tool, and of determining, through well-known analysis methods for stochastic Petri nets, relevant properties of the task plan applied to a particular environment.     

An agent-based genetic algorithm for hybrid flowshops with sequence dependent setup times to minimise makespan

This paper deals with a variant of flowshop scheduling, namely, the hybrid or flexible flowshop with sequence dependent setup times. This type of flowshop is frequently used in the batch production industry and helps reduce the gap between research and operational use. This scheduling problem is NP-hard and solutions for large problems are based on non-exact methods. An improved genetic algorithm (GA) based on software agent design to minimise the makespan is presented. The paper proposes using an inherent characteristic of software agents to create a new perspective in GA design. To verify the developed metaheuristic, computational experiments are conducted on a well-known benchmark problem dataset. The experimental results show that the proposed metaheuristic outperforms some of the well-known methods and the state-of-art algorithms on the same benchmark problem dataset.     

Standardized code quality benchmarking for improving software maintainability

We provide an overview of the approach developed by the Software Improvement Group for code analysis and quality consulting focused on software maintainability. The approach uses a standardized measurement model based on the ISO/IEC 9126 definition of maintainability and source code metrics. Procedural standardization in evaluation projects further enhances the comparability of results. Individual assessments are stored in a repository that allows any system at hand to be compared to the industry-wide state of the art in code quality and maintainability. When a minimum level of software maintainability is reached, the certification body of TüV Informationstechnik GmbH issues a Trusted Product Maintainability certificate for the software product.     

Non‐linear analysis of shells with arbitrary evolving cracks using XFEM

A new formulation and numerical procedures are developed for the analysis of arbitrary crack propagation in shells using the extended finite element method. The method is valid for completely non‐linear problems. Through‐the‐thickness cracks in sandwich shells are considered. An exact shell kinematics is presented, and a new enrichment of the rotation field is proposed which satisfies the director inextensibility condition. To avoid locking, an enhanced strain formulation is proposed for the 4‐node cracked shell element. A finite strain plane stress constitutive model based on the logarithmic corotational rate is employed. A cohesive zone model is introduced which embodies the special characteristics of the shell kinematics. Stress intensity factors are calculated for selected problems and crack propagation problems are solved. Copyright © 2004 John Wiley & Sons, Ltd.     

Quantitative analysis of pore patterns on rat prostate nuclei using spatial statistics methods

Spatial statistics methods have been used to analyse the nuclear pore pattern in rat ventral prostate nuclei isolated from adult animals. The observed results show that: (1) pores on prostate nuclear membranes are not randomly distributed; (2) the data sets obtained from different micrographs are consistent with the same statistical model thus suggesting the existence of a typical pore distribution.     

Applying chemical engineering concepts to non-thermal plasma reactors

Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.