Fábio Santana Magnani

Estimating sustainability impact, total cost of ownership and dependability metrics on data center infrastructures

The advent of cloud computing has demanded more computational resources from data centers. Prominent issues are dependability, total cost of ownership and sustainability, which are significantly impacted by the redundant infrastructures needed to support cloud computing services. In this context, models are important to support data center designers to estimate previous issues before implementing the final infrastructure. This paper presents a set of formal models for estimating sustainability impact and dependability metrics in data center infrastructures with the support of an integrated environment, namely, ASTRO. Besides, we adopt reliability importance to identify the most critical components in system reliability in order to propose different data center power infrastructures.

Strategic and Tactical Evaluation of Conflicting Environment and Business Goals in Green Supply Chains

Customer requirements and local legislation are forcing companies to provide green products and services. Such driving forces have resulted in the study of green supply chains (SCs), which are SCs that take into account factors that may cause positive or negative environmental impacts. However, some environmental indicators are often at odds with business goals, leading to a conflict, which, in order to optimize several goals simultaneously, is usually resolved by utilizing multicriteria decision analysis. Other modeling techniques describe systems by considering temporal aspects and causal relations. Such is the case of Petri nets, which were previously widely used to analyze performance in the context of SCs. This paper presents a method that combines the strengths of both techniques to assess the environmental and business indicators of such systems. This method adopts the exergy and the global warming potential key environmental indicators. A case study is conducted to demonstrate the application of the proposed modeling technique.

Sustainability and dependability evaluation on data center architectures

Business service through the Internet, particularly the cloud computing paradigm, have demanded more computational resources from data centers to provide high-availability services. As consequence, issues such as operational costs and sustainability increase, mainly, due to the redundant infrastructures needed to support the data center operation. However, data center designers have slightly information on the sustainability impact, operational cost and availability of data center architectures. In this context, models are important to support data center designers to estimate the environmental impact, dependability as well as the cost associated to the infrastructure before implementing it. This paper presents a set of formal models for estimating sustainability impact and dependability metrics, supported by an integrated environment, namely, ASTRO.

Towards the Evaluation of Environment and Business Trade-offs in Supply Chains

Supply chains (SCs) are one of the most environment impacting systems. Analysis of such systems should thus take into account not only performance but also environment indicators. The amount of energy consumed for producing goods and the total emissions of greenhouse gases (GHG) of an activity are examples of such indicators. This paper presents a framework for assessing performance as well as Global Warming Potential (GWP) and exergy indicators in SCs. In order, exergy accounting helps on finding reliable GWP indicators for different energy sources adopted in the supply chain. This framework supports the evaluation of supply chains@? business and environment indicators trade-offs using a unified model. A real case study is conducted to demonstrate the application of the proposed modeling technique.

Impact analysis of maintenance policies on data center power infrastructure

The growth of engineering disciplines, such as maintainability and reliability, have been motivated by several factors, which include the ever growing of system complexity as well as the high cost associated to failures repairing activities and productivity reduction. This work adopts a methodology, which includes a hybrid modeling technique that considers the advantages of both stochastic Petri nets (SPN) and reliability block diagrams (RBD) to evaluate maintenance policies with different service level agreement (SLA). Dependability, cost and sustainability are also prominent features considered in the proposed methodology.

Influence of mathematical simplifications on the dynamic and energetic performance of an engine/motorcycle integrated model

Brazil is a major producer and consumer of motorcycles. In this context, the Department of Mechanical Engineering at the Federal University of Pernambuco offers three two-wheeled courses: Studies on Bicycles and Motorcycles (45 h, graduate students), Propulsion of Bicycles and Motorcycles (45 h, graduate students), and Motorcycle Engineering (60 h, under graduate students). All of them present a greater or lesser mixture of general topics (e.g. accidents, culture, market, history) and technical ones (e.g., technology description and mathematical modeling). On those courses, the calculations are made using empirical correlations, commercial packages, and also simple methods, which, although quantitatively weaker, have both didactic and theoretical advantages, as they consider the essence of the phenomena and reveal the strongest relations between the variables. In this paper, we present an integrated engine/motorcycle simple model that permits the manipulation of parameters, such as the combustion time, heat losses, drag and inertial resistances, gear shifting and others. Those model parameters are then varied to study their influence on the motorcycle behavior. Manipulating this model, students learn that both engine and motorcycle inefficiencies have the same order of influence on motorcycle economy, ethanol is less volumetrically efficient than gasoline, the change of sprockets can increase the maximal speed while deteriorating the mean speed, and other interesting practical concepts. The success of the courses can be gauged by the students’ enrollment, by the professors’ evaluation by the students, class participation, and by the strong commitment of the students to the final projects. Other highly probable cause for the success is the motorcycle itself, always a passionate subject for young people in general, and mechanical engineers in particular.

Robustness of Electricity and Chilled Water Supply Systems Subject to Change Technical and Economic

This paper presents a methodology to evaluate the economic robustness of thermal systems designed to supply air conditioning and electricity for shopping malls in an Brazilian northeastern state. The procedure uses a hybrid method to minimize the Net Present Value (NPV) of the life costs. The optimization considers technical and economic aspects such as curves of demand, tariff variation along the day, equipment efficiencies and costs. It was studied the robustness of the systems in relation to variations of fuel tariff, electricity tariff, engine price, dollar fluctuation and demand profile.

Business and Environment Performance Evaluation in Supply Chains: A Formal Model-Driven Approach

While economic and service level indicators were adequate to show the performance of supply chains (SCs) in the past, nowadays, environment indicators are gradually becoming more relevant (Beamon, 1999). Many prominent companies and academic research groups around the world are making efforts to provide environmentally responsible products and services. These topics are subjects of intensive study not only due to the respective impact of the production and transport systems in our planet but also particularly related to the image these companies aim to project to the society (Beamon, 1999; Srivastava, 2007). Moreover, supply chains’ managers must carry about optimizing an endless number of variables that might impact costs and operational performance. These variables usually get in conflict between themselves. For instance, increasing the amount of stored goods might reduce the lead time to customers, but also increase storage costs and environment impacting resources like energy. Modelling is quite often employed for quantitative analysis of SCs (Simchi-Levi et al., 2000). One of themain advantages in usemodelling techniques is the possibility of analyse “what-if” questions. Thereby, it is possible to evaluate different scenarios looking for themost optimized ones. Although the strict mathematical modelling is one of the most used approaches in the evaluation of SCs (Cohen & Lee, 1988; Sabri & Beamon, 2000; Simchi-Levi et al., 2005), it is not always the best option. Such a method requires some simplifications that might incur inaccurate results. Othermodelling techniques, like queueing networks (Gross, 2009), Markov Chains (Norris, 1998), and Petri Nets (Bolch et al., 2006; Desrochers & Al-Jaar, 1994; Jensen, 1997), might be adopted so as to overcome this problem. Petri nets were proposed by Carl Adam Petri in 1962 (Petri, 1962), and have evolved into a formalism employed in different areas such as informatics, electronics and chemistry since then. This modelling technique has a graphical representation that supports the specification and design of systems. Having a solid mathematical foundation, Petri nets are very well suited for the numerical evaluation of complex systems. Different extensions were proposed to this formalism, including the concept of time (Ramchandani, 1994) after Carl Petri’s initial work. Petri nets have been already adopted for evaluating manufacturing systems and SCs (Alves et al., 2010; Desrochers & Al-Jaar, 1994;Makajic-Nikolic et al., 2004; Silva & Maciel, 2005; Viswanadham & Raghavan, 2000). Stochastic Petri nets (SPNs) (Bolch et al., 2006; German, 1994; Haas, 2002; Marsan et al., 1995) deals with probabilistic distributed times, which are approximated to distribution functions like exponential, Erlang and uniform. Business and Environment Performance Evaluation in Supply Chains: A Formal Model-Driven Approach