Search results

The purpose of this study is to characterize sintered hydroxyapatite (HA) samples produced by three-dimensional printing (3DP). This study is part of a project concerned with the fabrication of calcium phosphates implants by 3DP. However, before considering a more complex structure, like scaffolds or implants, a thorough knowledge of the role played by the sintering temperature on physical and mechanical the properties of porous HA is necessary.

The characteristics of sintered HA samples have been analyzed by means of x-ray diffraction, scanning electron microscope (SEM) and uniaxial compression tests. The 3DP parameters used to produce the HA samples were those who led to higher accuracy and mechanical stability.

Sintering temperature and powder morphology are critical factors influencing densification behavior, porosity, phase stability, mechanical strength and tangent modulus of the HA samples produced by 3DP. This study allowed us to conclude about the 3DP parameters to be used to produce porous HA specimens with the required integrity and dimensional accuracy, and the optimal post-processing sintering temperature which led to the best results in terms of porosity, microstructure, phase stability of HA and mechanical properties.

This paper provides a method to evaluate the manufacturability of calcium phosphate models produced by 3DP.

This paper aims to identify ways to establish an information system to aid users to enhance the effectiveness of self-regulated learning and solve the problem of learning domain unawareness. Many libraries are spacious and with a rich collection of books, the problem a newcomer may encounter in the wide library is spatial unawareness. In addition, people new to a particular field of study often encounter the problem of learning domain unawareness.

This paper presents an overview of self-regulated learning theory first. We realize the essential principles of self-regulated learning model in the library and developed a learning system that utilizes the concept of combining mobile augmented reality (AR), indoor navigation and data mining algorithms.

The proposed NO Donkey E-learning (NODE) system utilizes AR and innovative indoor positioning technology to fulfil the goal of navigation inside a library and solve the problems of spatial and learning domain unawareness. On the one hand, the system allows peers to communicate asynchronously to create a cloud-based information sharing community; the dual-track terminal (the website and the app interfaces) in the system could provide both educational functionalities and mobility for readers. On the other hand, AR navigation function integrates the information of reading paths, the real-space locations, real-time dynamic information, book introductions and readers’ comments to help readers have access to the topic-related books efficiently.

We found that although the library provides the floor plan and signs, such passive and fixed indication may cause spatial unawareness. People need system to show the bookshelf location and dynamic direction indicators when they walk in the wide library. However, most existing library information systems only provide readers with the function of book search, including which floor the book is on, call number and check-out status. In this sense, we propose that self-regulated learning theory integrated the new innovation technology is the solution for the above issues.

The system developed in this study, while viewing the real scenes inside the library through camera lens, provides related virtual educational information services and learning paths on screen and guides the public to do systematic self-regulated learning. With the functions of the “learning topic” and “knowledge sharing”, the learning system promotes the general public to self-monitor their learning progress and to use the sharing mechanism as the system structure to solve the two main problems of spatial unawareness and domain unawareness in learning in libraries, creating a truly innovative people-centred library information system.

Arbitrary constraints might be included into the problem domain in many engineering applications, which represent specific features such as multi-domain interfaces, cracks with small yield stresses, stiffeners attached on the plate for reinforcement and so on. To imprint these constraints into the final mesh, additional techniques need to be developed to treat these constraints properly.

This paper proposes an automatic approach to generate quadrilateral meshes for the geometric models with complex feature constraints. Firstly, the region is decomposed into sub-regions by the constraints, and then the quadrilateral mesh is generated in each sub-region that satisfies the constraints. A method that deals with constraint lines and points is presented. A distribution function is proposed to represent the distribution of mesh size over the region by using the Laplace equation. The density lines and points can be specified inside the region and reasonable mesh size distribution can be obtained by solving the Laplace equation.

An automatic method to define sub-regions is presented, and the user interaction can be avoided. An algorithm for constructing loops from constraint lines is proposed, which can deal with the randomly distributed constraint lines in a general way. A method is developed to deal with constraint points and quality elements can be generated around constraint points. A function defining the distribution of mesh size is put forward. The examples of constrained quadrilateral mesh generation in actual engineering analysis are presented to show the performance of the approach.

An automatic approach to constrained quadrilateral mesh generation is presented in this paper. It can generate required quality meshes for special applications with complex internal feature constraints.

Tourism is Mexico's largest source of foreign exchange, only surpassed by remittances and foreign direct investment, and is one of the most wealth-generating economic activities in the country. However, measures to mitigate the Covid-19 pandemic – such as the suspension of flights and strict restrictions on people's mobility – have caused great economic damage to the tourism industry, and with it, to large regions in the country. This chapter aims to determine the national and regional impacts of Covid-19 on Mexican tourism and analyze potential recovery scenarios. To this end, the study looks at tourism performance in Mexico in 2020 and compares it to the experience of the H1N1 influenza epidemic of 2009. The methodology uses a spatial econometric model to simulate potential impacts and prospective recovery scenarios. Finally, recommendations for tourism policy consider new trends in tourism, namely the rise in tourism advertising through digital platforms, the surge in domestic, rural and environmental tourism, and the development of a more informed, demanding and selective consumer.

This article aims to identify management practices that evidence how internal control have been considered essential, from the edition of the State Constitutional Amendment no. 75 of 2012, within the public administration of the executive branch of the State of Ceará, during the period 2012–2021.

The study relates the identified management practices to COSO (The Committee of Sponsoring Organizations) methodology “Internal Environment” component categories. The research is classified as basic, exploratory and bibliographic, on the theme of internal control in scientific articles published between 2015 and 2021, and documental, carried out through official documents, including the 27 Brazilian constitutions.

Existence of management practices that corroborate the essentiality of internal control in Ceará.

The study is limited to evidencing the control practices implemented in Ceará, not evaluating them as to their quality.

Contributions on control on constitutional-legal bases for other Brazilian Federation States.

Possibility of introducing the research theme into various branches of scientific knowledge, such as political science and contributing to public organizations to implement policies with the proper application of resources for the benefit of society.

The originality of the research is in demonstrating the essentiality of internal control in the State of Ceará, from the edition of management acts performed by the executive branch, based on Constitutional Amendment 75 of 2012, which did not become a dead letter of the law, enabling other states of the federation to do the same.

This paper aims to study the influence of the binder saturation level on the accuracy and on the mechanical properties of three-dimensional (3D)-printed scaffolds for bone tissue engineering.

To study the influence of the liquid binder volume on the models accuracy, two quality test plates with different macropore sizes were designed and produced. For the mechanical and physical characterisation, cylindrical specimens were used. The models were printed using a calcium phosphate powder, which was characterised in terms of composition, particle size and morphology, by X-ray diffraction (XRD), laser diffraction and Scanning electron microscopy (SEM) analysis. The sample’s physical characterisation was made using the Archimedes method (porosity), SEM, micro-computer tomography (CT) and digital scan techniques, while the mechanical characterisation was performed by means of uniaxial compressive tests. Strength distribution was analysed using a statistical Weibull approach, and the dependence of the compressive strength on the porosity was discussed.

The saturation level is determinant for the structural characteristics, accuracy and strength the models produced by three-dimensional printing (3DP). Samples printed with the highest saturation showed higher compressive strengths (24 MPa), which are over the human trabecular bone. The models printed with lower saturations presented the highest accuracy and pore interconnectivity.

This study allowed to acquire important knowledge concerning the effects of shell/core saturation on the overall performance of the 3DP. With this information it is possible to devise scaffolds with the required properties for bone scaffold engineering.

The paper aims to deliver a general review of the methods used to pursue the concept of a “sustainable university”.

The research was Internet based, and it included research papers, books, conference proceedings, technical reports and Internet Web sites. The review was divided in two main parts: sustainability implementation methods and assessment and report tools. In turn, the practices used on universities to implement included more “traditional” environmental sustainability initiatives and a more updated sustainable management systems.

Because “traditional” sustainability environmental sustainability initiatives have flaws, more recent tools were developed to help manage sustainability. Two sustainability management systems specifically oriented to universities are outlined on this paper. They both highlight the advantage of disposing a systematized management system; the need of address environmental issues and putting special attention on the use of resources, especially energy, on campus buildings; the social responsibility of the institution; and educational and research sustainability activities that must be taken on universities. Managing sustainability in a university would be facilitated if the procedure used to implement sustainability is aligned with the tool used that assesses its performance.

The paper presents an updated review of the efforts that universities have made in contributing to a sustainable development. It includes methods and tools used to manage sustainability within a university, including the ones used to implement, assess and report it. The paper also intends to highlight the need of consistency and coherence between the implementation method and the assessment and report tools.

Destination management organizations perform a very important role regarding the management of tourism destinations. Destination management systems are a key technological infrastructure for these organizations. However, in the literature, it is not clear what are the factors that promote the implementation of these systems, neither what are the factors that contribute to their success. This study aims to propose and test two research models to overcome these research gaps.

The first model refers to the determinants of the implementation of destination management systems, and the second model refers to the determinants of the success of those systems. The models are tested with data collected through a questionnaire survey from destination management organizations of five European countries, which are among the leaders in international tourism receipts.

Concerning the factors that promote the implementation of destination management systems, this study reveals the importance of the diversity of partnerships that the private sector establishes in the destination, of advantages resulting from governance and of partners' involvement in the functions of destination management organizations. Concerning the factors that promote the success of these systems, this study highlights the importance of a phased implementation, the fact that a high number of functionalities in the system prevents success and the importance of having a revenue model that can support financial and operating costs.

The study provides important theoretical and practical contributions to the successful implementation of destination management systems by destination management organizations.

The purpose of this paper is to describe synchronous, remote tutoring for the Deaf STEM Community Alliance's virtual academic community (VAC). The alliance addresses critical barriers for students who are deaf or hard of hearing (D/HH) in postsecondary science, technology, engineering, and mathematics (STEM) majors.

A mixed-method approach (qualitative content analysis and descriptive statistics) documents project activities.

Google+ Hangouts was used for remote tutoring. Participants completed 57 tutoring sessions. Participants found tutoring beneficial, especially for its convenience. Technical assistance and feedback systems were created to support participants. Grade point averages (GPA) and retention remained stable.

Research on this project continues. Small sample size is a limitation of the study. Ongoing research investigates how remote technology and social media impact learning for students who are D/HH.

Scholarship on social media for educational purposes is minimal. While specifics of particular social media platforms vary, recruitment, technical assistance, and establishing feedback mechanisms are common issues for VACs. Outcomes from this study will be used to improve this VAC and create documentation for replication.

The Deaf STEM Community Alliance provides supportive resources to underrepresented students in STEM majors. Improved GPA and retention in STEM majors will generate more individuals qualified for STEM careers. Research on VACs creates opportunities to understand how technology and networked communities change knowledge and learning.

The Deaf STEM Community Alliance is a unique project for postsecondary students in STEM fields who are D/HH. The information is valuable to educators interested in using social media for instruction.

This paper intends to quantify the impact of anticipating a capacity expansion, treated as a risky investment in a strategic vertical integration.

This paper adapts the real option methodology to a time frame model. It uses a case study to investigate the vertical integration approach.

The integration value depends on the demand critical level under market volatility. The existence of demand positive jumps affects the demand critical value and the integration decision moment.

The numerical example is limited to a single organization, but the findings allow a generalization of the proposed framework.

The model helps managers to more accurately decide to change from outsourcing to an integration strategy and defer commitment until future uncertainties, related with market and lack of information, can be partially solved. Finally, the paper provides a time framework for a strategic decision support system.

The research in this paper differs from previous literature mainly in four aspects: it quantifies the integration decision under demand uncertainty; its model determines critical demand quantities as the trigger moment for a capacity investment; it examines the impact, on the trigger moment, of the uncertainties in demand for products; and its model incorporates positive shocks impacts in products' demand, making a closer approach to the reality.