Gabriel Alves

Performance modeling for evaluation and planning of Electronic Funds Transfer Systems

The Electronic Funds Transfer (EFT) Systems promote both financial benefits for the institutions that use them and potential conveniences for their customers. EFT Systems debiting and crediting individual bank accounts from points of sale (POS) terminals in different companies and providing cash on demand 24 hours a day through automatic tellers. In the EFT system, eventual workload peaks and fluctuations can cause degradation on system performance. Hence, the performance evaluation of EFT Systems has an enormous importance for Electronic Transactions providers, since the computing resources must be efficiently used in order to ensure high availability, reliability, scalability and security. This paper presents an stochastic model for performance evaluation and planning EFT systems processing and storage infrastructure considering load variation range. A case study is presented in order to describe the adequacy of presented approach and results.

Petri nets tools integration through Eclipse

The lack of a standard file format to represent Petri nets limits the reuse of models among Petri net tools. In order to reduce the impact of this limitation the Petri Net Markup Language (PNML) has been proposed. PNML is an interchange file format for Petri nets based on XML. This paper presents a framework, called EZPetri, based on PNML. EZPetri is a perspective and a set of plug-ins of the Eclipse platform. The union of Eclipse and PNML has demonstrated itself to be an effective instrument for integrating Petri net tools and applications. The paper discusses the principles of EZPetri and presents one application integrated into the framework: Power Consumption Analysis Framework. Such application has been developed with no knowledge about EZPetri. This is a demonstration of the integration facilities provided by the framework. EZPetri is thus an useful platform for combining existing Petri net tools and applications into a single environment, offering the Petri net community a new perspective of integration.

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.

A GSPN based approach to evaluate outbound logistics

The outbound logistics can determine the success or failure of an industry. It has a high participation in overall logistics costs and is a decisive factor for the Quality of Service (QoS). Measuring this activity and evaluating possible changes will help its management and can lead to a cost reduction and a better QoS. This paper proposes the use of predefined Generalized Stochastic Petri Nets (GSPN) components that allows the evaluation of vehicles utilization, storage levels and QoS indices. The model representing an outbound logistics scenario is obtained with a bottom-up approach, through the composition of these components, guaranteeing some expected GSPN properties. At the end of this paper, a study case made in a Brazilian meat processing industry is presented.

Stochastic evaluation of supply chains and replenishment policies with Petri net components

The outbound logistics deals with the transportation and storage of finished goods. It is one of the most complex and expensive activity of the supply chain management and is decisive for the Quality of Service (QoS). This paper proposes the use of pre-defined Petri net components to model and evaluate this activity. The model that represents an outbound logistics scenario is obtained with a bottom-up approach, guaranteeing some expected Petri nets properties. Furthermore, the use of pre-defined, validated components allows modelling and evaluating the supply chain entities and processes through a systematic procedure. In the end of this paper, results related to a real case study, conducted by considering the proposed models, is depicted.

An integrated environment for embedded hard real-time systems scheduling with timing and energy constraints

Embedded hard real-time systems have stringent timing constraints that must be satisfied for the correct functioning of the system. Additionally, there are systems where energy is another constraint that must also be satisfied. In order to satisfy such requirements, a pre-runtime scheduling is presented to find a feasible schedule satisfying both constraints. The proposed approach uses state space exploration for finding feasible schedules taking into account timing and energy constraints. The main problem with such method is the space size, which can grow exponentially. This paper shows how to minimize this problem, and presents a depth-first search method on a timed labeled transition system derived from the time Petri net model. EZPetri is an Eclipse perspective for Petri nets based on PNML. It provides facilities for integrating Petri net applications and existing Petri net tools. In this paper we demonstrate how the plug-in technology of Eclipse was employed to integrate the pre-runtime scheduling synthesis framework with the EZPetri environment. In order to depict the practical usability of the proposed approach, a pulse-oximeter case study is adopted to show how to find a feasible schedule.

Assessment of Bus Rapid Transit (BRT) Time Lags under Probabilistic Uncertainties

Large cities face growing mobility problems, due to the major traffic jams that result from high numbers of vehicles on the roads. In response, city and national governments have invested in alternative means of urban passenger transit, such as subways, trains, as well as Bus Rapid Transit (BRT). This article aims to analyze the BRT system, by attempting to calculate the probability of reaching a destination at a specific time, thereby providing a tool that can be employed to improve the system and increase passenger confidence in it. To this end, a Continuous Time Markov Chain (CTMC) model is proposed to represent the bus stations and compute the probability metric for arrival at the destination within the specified time frame. The model allows a mathematical function to calculate the probabilities for the corresponding architecture. Two case studies were conducted in order to verify the model and illustrate its potential value in the planning of BRT systems.

Performability Assessment of a Government Process in the Cloud

Governments can take advantage of cloud computing to deal with the pressures as well as challenges to reduce costs and improve service performance. In this context, the joint evaluation of performance and dependability (i.e., Performability) is very important, and stochastic modeling provides a prominent mechanism for assessing government services in the cloud and evaluation of distinct scenarios. This work proposes an approach based on stochastic Petri nets (SPN) for performability evaluation of Taxpayer Assistance Center (TAC) in the cloud. Performability techniques are considered, as failures in the process are taken into account and the respective impact in performance is analyzed. Results are presented to demonstrate the feasibility of the proposed approach, and they indicate that failures should not be neglected.

Transport mode assessment for inbound logistics: A study based on coffee industry

Over the years, inbound logistics has been prominent to many industries, as globalization has forced companies to increase productivity while reducing costs. Transport modes considerably impact the costs, and a proper evaluation should consider performance, failures as well as sustainability issues. This paper presents an approach based on stochastic Petri nets (SPN) for assessing different transport modes in inbound logistics for coffee industry taking into account performability and sustainability.

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