Search results

Barabási‐Albert and small‐world networks. In this model, the order‐disorder phase transition of the order parameter is well defined on small‐world networks. We calculate the value of the critical temperature Tc for several values of rewiring probability p of the directed small‐world network. For directed small‐world networks we obtained a second‐order phase transition for p = 0.2 and first‐order phase transition for p = 0.8. On directed Barabási‐Albert we show that phase transition do not exist for Ising model with spin S = 1, 3/2 and 2.

The purpose of this paper is to provide an overview of how quantitative analysis methods have been and can be used to improve the competitiveness of tourism destination. The focus of the study is social network analysis (SNA).

The research methodology is qualitative and consists of the review literature relevant to this thesis. This methodology is necessary to give an account of the methods and the techniques adopted for the data collection used in other economic sectors.

SNA is needed to analyze the creation and configuration of communities of practice within destination and to identify possible barriers to effective interaction. Essentially, it is a complex adaptive socio-economic system. It shares many (if not all) of the characteristics usually associated with such entities, namely, non-linear relationships among the components, self-organization and emergence of organizational structures, robustness to external shocks.

The most important limit of this paper is that all the results presented here do not concern a single case study. Future research studies will provide a larger number of cases and examples to give the necessary validation to the findings presented here.

This paper provides a view into the network of relationships that may give tourism organization managers a strong leverage to improve the flow of information and to target opportunities where this flow may have the most impact on regulatory or business activities.

SNA can help to detect actual expertise and consequently project the potential losses deriving from an inefficient flow of knowledge. In addition, the authors will be able to define roles in the organizational networks and make an evaluation of informal organizational structures over the formal ones. Traditional organizational theories lack a concrete correspondence with mathematical studies and in this respect the authors sought to identify a correspondence.

The purpose of this paper is to simulate a pseudo direct drive (PDD) by using permanent magnet arrays.

A 2D finite element model of the PDD was built. The static magnetic torque on air-gaps was obtained by Coulomb’s virtual work method using Ansys Maxwell software. To simulate the relative movement between input rotor and output rotor, two movement bands were applied.

The PDD’s torque relation was proved. The PDD simulated presents low cogging torque.

The manufacturing steps and materials applied in a construction of a coaxial magnetic gear, PDD’s main component, are presented.

The value of this paper is to present the numerical techniques applied to simulate a PDD and the manufacturing steps and materials applied in a construction of a coaxial magnetic gear.

The purpose of this paper is to simulate a magnetic gear full integrated generator (MGFIG) to apply in wind power generation.

A 2D finite element model of the MGFIG was built. The static magnetic torque on air-gaps was obtained by Maxwell stress tensor. In order to simulate the movement of both rotors in relation to the winding and modulators two movement bands were applied.

It was proved that the MGFIG magnetized with Halbach arrays is able to eliminate the cogging torque, improve the quality of the generated voltage waveform and decrease the core losses and permanent magnet eddy current losses.

The loss coefficients belonging to core material were found from the measured curves provided by an electrical manufacturer.

The originality of this paper is to improve the good characteristics of a MGFIG, such as a simple mechanical structure, good utilization of permanents magnet (PM) materials and lower manufacturing cost, by incorporating Halbach PMs arrays to decrease core and eddy current losses, improve the voltage waveform.

The purpose of this article is to compare maintenance policies based on Weibull and q-Weibull models.

This paper uses analytical developments, several figures and tables for graphical and numerical comparison. Previously published hydropower equipment data are used as examples.

Models for optimal maintenance interval determination based on q-Weibull distribution were defined. Closed-form expressions were found, and this allows the application of the method with small computational effort.

The use of the q-Weibull model to guide the definition of maintenance strategy allows decision-making to be more consistent with sample data. The flexibility of the q-Weibull model is able to produce failure rate modeling with five different formats: decreasing, constant, increasing, unimodal and U-shaped. In this way, the maintenance strategies resulting from this model should be more assertive.

Expressions for determining the optimal interval of preventive maintenance were deduced from q-Weibull distribution. Expected costs per maintenance cycle of Brazilian hydropower equipment were calculated with q-Weibull and Weibull distributions. These results were compared in terms of absolute values and trends. Although a large number of works on corrective and preventive maintenance have been proposed, no applications of the q-Weibull distribution were found in literature.

Corporate social responsibility (CSR) and corporate sustainability have gained prominence in the major capital markets. In Brazil, the São Paulo Stock Exchange (BM&FBovespa) has created the Corporate Sustainability Index (ISE) and the Carbon Efficient Index (ICO2), responsible for indicating the performance of sustainable companies. Therefore, this study proposes to examine and compare the stock returns of the sustainability index member companies with the returns of companies out of these indexes. In this methodology we selected the two principal negotiability indexes of that market (IBOV and IBrX50), which are indexes that meet the most traded stocks of BM&FBovespa, and calculated the average daily returns of the four indexes in order to make performance comparisons over the period 2005–2014, based on nonparametric statistical tests. Our findings indicate that the average returns of sustainability indexes were higher, but these differences were not statistically significant, confirming previous evidence. Additionally, by means of a cointegration test, we found that the indexes are cointegrated in the long term. These findings are limited to the analyzed emerging market and are also subject to the limitations of the estimated models. Thus, we can infer that presence in the sustainability indexes does not indicate statistically significant higher returns, which means that companies with sustainable practices in Brazil are not only concerned with economic performance, but also with social, cultural, and environmental issues. The main findings are aligned with the concept of triple bottom line, even in the case of an emerging market.

Even though the implementation of lean in health care environments is relatively recent, it has been receiving a lot of attention in recent years. Partly because of the fact that it is a recent field of practise and research and partly because the number of works developed in this field has grown rapidly, it is important to frequently update the perspectives on this field of investigation. Thus, this study aims to review the implementation of lean tools and techniques applied to hospital organizational areas in a five-year period, between 2014 and 2018, complementing some of the most relevant reviews already published. The most important criteria such as tools, methods and principles, hospital areas intervened, improvements and difficulties were assessed and quantified.

As starting point for this systematic literature review (SLR), a set of selected pre-existing review publications was used to support the current study and as the ground base for the expansion of the studies about lean health care. The current study contemplated 114 articles from a five-year period between 2014 and 2018. A subset of 58 of these articles was critically assessed to understand the application of lean tools and methods in different hospital areas.

The thorough analysis of selected articles show a lack of works in continuous improvement approaches when compared to the application of production organization methods, visual management and diagnosing and problem-solving tools. The reported improvement results demonstrate alignment with the principles and foundations of lean philosophy, but such results are presented in isolated initiatives and without robust evidence of long-term maintenance. Moreover, this study shows an evolution in the number of articles referring to lean implementation in hospital areas, but in its great majority, such articles report isolated implementations in different areas, not spreading those for the global organization. Thus, some of the main recommendations are the need to implement studies on complete flows of patients, drugs and materials, instead of isolated initiatives and strive to promote the cultural change of hospitals through structural changes, following new visions and strategic objectives, supported by real models of continuous structural and sustained improvement.

The current study develops a new perspective of the articles published under the thematic of lean health care, published in a recent period of five years, which are not completely covered by other works. Additionally, it explicitly applied, in an innovative way, an approach that used a set of previous reviews as the starting point for this SLR. In this way, it integrates approaches and categories from different SLRs, creating a framework of analysis that can be used by future researchers. Finally, it shows the most recent implementations of lean health care, exposing the current trends, improvements and also the main gaps.