1,720,985 research outputs found
Sustainable Manufacturing through Digital Multi-Material 3D Printing
Full text linkThe utilisation of three-dimensional (3D) printing has become a well-established method for fabricating structural components across various materials such as polymers, metals and ceramics. Within this domain, multi-material 3D printing emerges as a pivotal advancement, offering prospects for rapid manufacturing, customised design, and structural innovation. Particularly, the incorporation of recycled materials into multi-material printing holds promise for promoting sustainability and recyclability in manufacturing processes. By leveraging multi-material printing techniques and incorporating recycled materials, this study aims to advance the sustainability agenda within manufacturing practices while concurrently exploring avenues to enhance material performance for practical engineering applications. This study focuses on the multi-material printing of pure polylactic acid (PLA) alongside recycled polylactic acid (rPLA), employing fused deposition modelling (FDM) as a cost-effective 3D printing technique. The research aims to identify the optimal composition for achieving desired material properties by exploring different percentages and layer placements of recycled material in combination with pure PLA. Detailed analysis of the mechanical properties of these 3D printed components was conducted, with the experimental results further validated through analysis of variance. The results of this study emphasis the mechanical advantages associated with the utilisation of multi-material 3D printing techniques. Moreover, the incorporation of both PLA and rPLA materials highlights the potential sustainability benefits inherent in these approaches
Enhancing Sustainability and Functionality with Recycled Materials in Multi-Material Additive Manufacturing
Full text linkThis study presents a novel multi‐material additive manufacturing (MMAM) strategy by combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to improve both performance and sustainability. Specimens were produced using fused deposition modelling (FDM) with various vPLA: rPLA ratios (33:67, 50:50, and 67:33) and two distinct layering approaches: one with vPLA forming the external layers and rPLA as the core, and a second using the reversed arrangement. Mechanical testing revealed that when vPLA is used as the exterior, printed components exhibit tensile strength and elongation improvements of 10–25% over conventional single‐material prints, while the tensile modulus is largely influenced by the distribution of the two materials. Thermal analysis shows that both vPLA and rPLA begin to degrade at approximately 330°C; however, rPLA demonstrates a higher end‐of‐degradation temperature (461.7°C) and increased residue at elevated temperatures, suggesting improved thermal stability due to enhanced crystallinity. Full‐field strain mapping, corroborated by digital microscopy (DM) and scanning electron microscopy (SEM), revealed that vPLA‐rich regions display more uniform interlayer adhesion with minimal voids or microcracks, whereas rPLA‐dominated areas exhibit greater porosity and a higher propensity for brittle failure. These findings highlight the role of optimal material placement in mitigating the inherent deficiencies of recycled polymers. The integrated approach of combining microstructural assessments with full‐field strain mapping provides a comprehensive view of interlayer bonding and underlying failure mechanisms. Statistical analysis using analysis of variance (ANOVA) confirmed that both layer placement and material ratio have a significant influence on performance, with high effect sizes highlighting the sensitivity of mechanical properties to these parameters. In addition to demonstrating improvements in mechanical and thermal properties, this work addresses a significant gap in the literature by evaluating the combined effect of vPLA and rPLA in a multi-material configuration. The results emphasise that strategic material distribution can effectively counteract some of the limitations typically associated with recycled polymers, while also contributing to reduced dependence on virgin materials. These outcomes support broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within additive manufacturing (AM). Overall, the study establishes a robust foundation for industrial-scale implementations, paving the way for future innovations in eco-efficient FDM processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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Carbonaceous composition analysis of PM2.5 and source apportionment of organic matter (OM) employing Fourier Transform-Infrared Spectroscopy (FT-IR) at low- and middle-income countries
No full textAs per World Health Organization (WHO), about 91% of the global population breathe polluted air leading to approximately 7 million premature deaths annually. These harmful impacts are disproportionate, with Low- and Middle-Income Countries (LMICs) at the forefront. In this study, we demonstrate the capability of cost-effective and non-destructive Fourier TransformInfrared Spectroscopy (FT-IR) method for providing particulate matter (PM) characterization at international Surface Particulate Matter Network (SPARTAN) sites. Polytetrafluoroethylene (PTFE) filters, collected with an AirPhoton SS5 Sampler, were analyzed for mass, organic carbon (OC), elemental carbon (EC), organic functional groups, organic matter (OM), inorganic ions, elements, and light absorption. The daily and seasonal variations in the PM2.5 composition at two African sites Pretoria, South Africa and Addis Ababa, Ethiopia is presented. The mean annual concentration of PM2.5 was 16.8 µg/m3 , and 22.5 µg/m3 at Pretoria, and Addis Ababa, respectively. OM and ammonium sulfate dominated the PM2.5 mass at Pretoria whereas OM, dust, and EC contributed significantly (roughly 25% each) towards the average PM2.5 concentrations in Addis Ababa. OM source classes and their geographical origins were also determined through the Positive Matrix Factorization (PMF) model, using the baseline-corrected FT-IR spectra, pollution roses, back-trajectory analysis, correlation plots with inorganic species, and fire data products at these two sites. Pretoria samples showed significant contribution from wildfires whereas Addis Ababa has significant impact from home charcoal and wood burning but none from wildfires. In a third project, the quality of the FT-IR OC and FT-IR EC data across the globally distributed SPARTAN network was evaluated using the Hybrid Integrating Plate and Sphere (HIPS) based black carbon (BC) and SPARTAN residual organic matter (OM) data. The daily and seasonal variations in the FT-IR OC and FT-IR EC concentrations for the 22 globally distributed SPARTAN sites were examined, and an inter-site comparison is presented. The outcomes of this study will contribute to a reduction in the PM2.5 exposures at these LMICs sites through informed decision-making by policy makers
Measurement of true ileal calcium digestibility of feed ingredients for broiler chickens : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand
Full text linkListed in 2017 Dean's List of Exceptional ThesesThe recent interest towards the use of digestible phosphorus (P) in poultry feed formulations necessitates the measurement of true calcium (Ca) digestibility of feed ingredients because of the close relationship between these two minerals for their absorption and post absorptive utilisation. When this thesis research was initiated, no published data were available on Ca digestibility of feed ingredients for broiler chickens. The major objective of the studies reported in this thesis was to determine the true Ca digestibility of feed ingredients for broiler chickens. In total, nine studies were conducted.
The first study (Chapter 4) was conducted to determine the effect of methodology on ileal endogenous Ca losses. Three methods, namely feeding a Ca- and P-free diet, maize gluten meal based diet and egg albumen based diet, were used. Ileal endogenous Ca losses differed among different methodologies. The highest ileal endogenous losses of 125 mg/kg dry matter intake (DMI) were recorded on the Ca- and P-free diet, followed by 77 and 43 mg/kg DMI on maize gluten meal and egg albumen diets, respectively.
In the second and third studies (Chapters 5 and 6), regression and direct methods, respectively, were used to determine the true Ca digestibility of meat and bone meal (MBM). The true Ca digestibility coefficient of MBM samples were ranged from 0.41 to 0.60. No difference was observed between true Ca digestibility coefficients of MBM determined by regression and direct methods. Since the direct method is less laborious and cost effective compared to regression method, this method was used in subsequent studies (Chapters 7 to 10) to determine the true Ca digestibility of a range of Ca sources.
In fourth and fifth studies (Chapters 7 and 8), the influence of dietary P,
particle size and Ca to non-phytate P ratio was investigated on the true Ca digestibility of limestone for broiler chickens. The true Ca digestibility of three limestone samples varied from 0.56 to 0.62. Supplementation with recommended dietary P (4.5 g/kg) increased the true Ca digestibility of limestone when compared to diets without P. An increase in particle size from <0.5 to 1-2mm improved the true ileal Ca digestibility of limestone. Widening the Ca to non-phytate P ratio reduced the true Ca digestibility of limestone for broiler chickens.
The sixth study (Chapter 9) was conducted to determine the effect of Ca source and particle size on the true Ca digestibility and total tract retention. Limestone and oyster shell were used as Ca sources. No difference was observed between the true Ca digestibility of limestone and oyster shell. An increase in particle size from <0.5 to 1-2 mm increased both the Ca digestibility and retention of both Ca sources, and increased the Ca concentration of gizzard contents.
The study reported in Chapter 10 was conducted to determine the true Ca digestibility of dicalcium phosphate (DCP), monocalcium phosphate (MCP), canola meal, poultry by-product meal and fish meal, and to compare the effect of dietary adaptation length on true Ca digestibility of DCP and MCP. The true Ca digestibility coefficients of these feed ingredients were lower than MBM, limestone and oyster shell, and ranged from 0.24 to 0.33. It was speculated that the length of adaption to the assay diets may be responsible for the lower than expected estimates. The effect of dietary adaptation length (24, 48 or 72 hrs) was subsequently examined, but had no effect on true Ca digestibility of DCP and MCP.
In the final study (Chapter 11), the true Ca digestibility of DCP was determined using different methodologies (regression, difference and direct methods). The true Ca digestibility coefficients of DCP were 0.34 and 0.21 with direct and different methods, respectively. A very low digestibility coefficient of 0.13 was determined by the regression method.
In conclusion, the true Ca digestibility coefficient of major Ca sources (limestone, oyster shell and MBM) is not high and varied from 0.40 to 0.70. Particle size of limestone and oyster shell influenced Ca digestibility, with coarser particles having higher digestibility. The direct method appears to be suitable for the determination of true Ca digestibility of limestone, oyster shell and MBM, but may not be appropriate for other Ca sources with intrinsic imbalance of Ca and P
Data mining of audiology
No full textThis thesis describes the data mining of a large set of patient records from the hearing aid clinic at James Cook University Hospital in Middlesbrough, UK. As typical of medical data in general, these audiology records are heterogeneous, containing the following three different types of data: Audiograms (graphs of hearing ability at different frequencies) Structured tabular data (such as gender, date of birth and diagnosis) Unstructured text (specific observations made about each patient in a free- text or comment field) This audiology data set is unique, as it contains records of patients prescribed with both ITE and BTE hearing aids. ITE hearing aids are not generally available on the British National Health Service in England, as they are more expensive than BTE hearing aids. However, both types of aids are prescribed at James Cook University Hospital in Middlesbrough, UK, which is also an important feature of this data. There are two research questions for this research: Which factors influence the choice of ITE (in the ear) as opposed to BTE (behind the ear) hearing aids? For patients diagnosed with tinnitus (ringing in the ear), which factors influence the decision whether to fit a tinnitus masker (a gentle sound source, worn like a hearing aid, designed to drown out tinnitus)? A number of data mining techniques, such as clustering of audiograms, association analysis of variables (such as, age, gender, diagnosis, masker, mould and free text keywords) using contingency tables and principal component analysis on audiograms were used to find candidate variables to be combined into a decision support system (OSS) where unseen patient records are presented to the system, and the relative likelihood that a patient should be fitted with an ITE as opposed to a BTE aid or a tinnitus with masker as opposed to tinnitus not with masker is returned. The DSS was created using the techniques of logistic regression, Nalve Bayesian analysis and Bayesian network, and these systems were tested using 5 fold cross validations to see which of the techniques produced the better results. The advantage of these techniques for the combination of evidence is that it is easy to see which variables contributed to the final d~~Jpion. The constructed models and the data behind them were validated by"presenting them to the Principal audiologist, Dr. Robertshaw at James Cook University Hospital in Middlesbrough for comments and suggestions for improvements. The techniques developed in this thesis for the construction of prediction models were also used successfully on a different audiology data set from Malaysia. These decisions are typically made by audiology technicians working in the out- patient clinics, on the basis of audiogram results and in consultation with the patients. In many cases, the choice is clear cut, but at other times the technicians might benefit from a second opinion given by an automatic system with an explanation of how that second opinion was arrived at.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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