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Mixing Power Requirement Determination in Agitated Drum Using Dimensional Analysis
76-88Views:335The mixing of granular materials in an agitated drum can be characterized by the dimensionless power equation. The equation was created by dimensional analysis, for which the parameters affecting the mixing power requirement were collected based on the literature. The most important of these are the rotational speed, the drum loading factor, the geometric and physical properties of the mixing drum and the granular materials. The dimensionless power equation is used to estimate with reasonable accuracy the Power number within the given range of applicability , which has been validated by measurements. From the Power number, the mixing power requirement of the mixed granular material can be calculated, which can be used as operational data for selecting the mixing motor.
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Segmenting the Impact of Organizational Structure and Leadership on Project Resilient and Project Success in the Ethiopian Construction Industry: a FIMIX-PLS & PLS-POS Approach
73-103Views:100This research looks at the vital roles of leadership and organisation design in the attainment of project resilience and success in the construction sector. Informed by contemporary theories on organisational resilience and leadership, a framework was developed and rigorously tested against data using Partial Least Squares Structural Equation Modelling (PLS-SEM) and with more advanced techniques of segmentation (FIMIX-PLS and PLS-POS) to identify and take into consideration unobserved heterogeneity. Using data collected from project professionals, resilient leadership and adaptive organisation design were shown to be critical to project resilience, but the effect of leadership and organisation design on project resilience differed from segment to segment as well as across demographics. The ex-post analysis suggested that the awareness of resilience, practical experience and higher education exacerbated the relationships between aspects of resilient leadership and project resilience, as well as between adaptive organisation design and project resilience. The analysis also showed that relationships between leadership, organisational structure, and resilience can be mediated by demographic factors, such as awareness, experience, and education. The findings highlighted the importance of fostering inclusive, participative type leadership styles and continuous forms of experiential learning to enhance resilience outcomes. The value of specific indicators such as team participation in decision making or the leader's self-confidence was also identified as being critical aspects of resilient organisational structures and effective leadership. The implications of this study were important for each group of stakeholders: organisations should encourage resilience-based leadership, experiment with multi-dimensional flexible team structures and create a culture of continued, experiential learning and communications as knowledge and industries evolve. The theoretical contributions that validated the effects of segments of latent variables and offered insight into the added value of using segmentation were positive contributions to theory. Limitations, such as sample size and sector, stimulate avenues for future work and in particular reinforce the case for longitudinal, cross-sector research to build sectors’ internal and external constructs of project resilience. Future research needs to apply multi-facilitated empirical, qualitative and advanced analytics means to enable further quantification, and complexity in project survival, success and resilience.
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Comparative Study of Surface Treatment Procedures for Dental Implants
12-32Views:237Nowadays, the most common type of implant in dentistry is a partial tooth replacement, such as a crown, or a complete tooth replacement. Today, many manufacturers offer implants made of a wide variety of materials and designs. These restorations must meet strict standards, one of the most stringent being surface roughness. Since proper bone-to-implant contact only occurs with adequate surface roughness, several methods are used to achieve the correct value. After reviewing the results of experiments carried out by several research groups, it is concluded that the surface roughness, the shape of the implant fixation screw, the shape of the thread and the thread elevation used to achieve the desired roughness together determine the success of the implantation. The average surface roughness required for osseointegration is considered to be optimal for values between 1 and 100 µm. In most cases, the surface roughness of commercially available dental prostheses is Ra 1-2 µm, but this can be modified by various grinding, acid etching and polishing processes to suit the application. Acid etching is a common technique for roughness reduction, which is the most effective in reducing surface roughness of dental restorative materials (mostly titanium alloys), thus bringing the roughness within the desired range. The result of acid etching is influenced by the concentration of acid, the temperature of the acid bath and the time spent in the acid. The acid used for the surface treatment is important and is most commonly sulphuric acid, hydrochloric acid or hydrogen fluoride (HF) and combinations of these. The study shows that the most optimal results are obtained with HF. Replacements are nowadays largely made by additive manufacturing, which allows for customised replacements and, due to dimensional accuracy, reduces the time and cost of post-processing, i.e. the surface treatment can be used to achieve the desired surface roughness and size at the same time. As a result, newer materials are being used for clinical prostheses and surface treatment should be applicable to all materials. The most optimal solution is a combination of grit blasting and acid etching. With this technology, the surface roughness for all materials reaches the optimum value of 1-100 µm, sometimes 1-2 µm, but can be further reduced below 1 µm by polishing. The study investigates the role of surface roughness, the surface roughness should only be reduced up to a certain value, approximately 0.5 µm, as smooth surfaces have limited or no potential for osseointegration.
