Analysis of Selective Laser Sintering print parameter modelling methodologies for energy input minimisation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Mechatronics at Massey University, Albany, New Zealand

Additive Manufacturing (AM) is the name given to a series of processes used to create solids, layer upon layer, from 3 Dimensional (3D) models. As AM experiences rapid growth there exists an opportunity for Selective Laser Sintering (SLS) to expand into markets it has not previously accommodated. One of the ways SLS can accomplish this is by expanding the range of materials that can be processed into useful products, as currently only a small number of materials are available when compared to other AM technologies. One of the biggest barriers to the adoption of materials is the danger inherent to high-energy processes such as SLS. The aim of this research was to identify opportunities to improve current methods for modelling the relationship between material specifications, and printing parameters. This was achieved by identifying existing models used to determine printing parameters for a new material, identifying weaknesses in current modelling processes, conducting experimentation to explore the validity of these weaknesses, and exploring opportunities to improve the model to address these weaknesses. The current models to determine printer parameters to achieve successful sintering include both the Sintering Window (SW) and the Energy Melt Ratio (EMR). These two models are complementary, and both are required to establish all common print parameters. They include both thermal and physical powder properties, but do not include any optical properties. This is significant because the nature of the SLS printing process relies on concentrated delivery of laser energy to achieve successful sintering. Analysis of two similar polyamide powders, one black and one white, identified that the two powders were similar thermally and physically, which meant the models predicted that they should both sinter successfully utilizing the same set of print parameters. Results of the experimental trials showed that no trials involving the white powder sintered successfully, and trials involving the black powder suffered from issues with either insufficient energy to successfully remove parts without damage, or excessive energy causing excess powder to bond to the part. Further experimentation was carried out to investigate the differences in optical properties using Fourier Transform Infrared Spectroscopy (FTIR) and Spectrofluorophotometry. FTIR revealed that there was a difference in absorption as a material property, indicating that differences in laser energy absorption could explain the results seen in the trials. Spectrofluorophotometry revealed minimal differences in fluorescence of the powders, suggesting it an unlikely source of energy loss. Future work is recommended to research a standardised form of testing setup that can be used to categorize the reflectance of a material, as current work relies on proprietary experimental setups. Finding methods of classifying the laser absorption that is easily available to operators would enable refinement of the EMR equation to reflect the energy losses during printing, and remove another barrier for adoption of new materials

Critique of network management systems and their practicality

Networks have become an integral part of the computing landscape, forming a global interconnection of a staggering number of heterogeneous systems and services. Current research focuses on policy based management and autonomous systems and involves the utilisation of very different languages and technologies in concert. This paper examines four current proposals for autonomous network management and analyses them using architectural modelling, against a measure of practicality, as expressed by scalability, reliability and maintainability. © 2010 IEEE

Motivation as a predictor of outcomes in school-based humanistic counselling

Recent years have seen a growth in the provision of counselling within UK secondary schools, and research indicates that it is associated with significant reductions in psychological distress. However, little is known about the moderators and mediators of positive therapeutic benefit. In the field of adult mental health, motivation has been found to be one of the strongest predictors of therapeutic outcomes, and it was hypothesised that this may also be a predictor of outcomes for young people in school-based counselling services. To assess the relationship between young people’s motivation for counselling and its effectiveness within a secondary school setting. Eighty-one young people (12 - 17 years old) who attended school-based humanistic counselling services in Scotland. Clients completed a measure of motivation for counselling at the commencement of their therapeutic work and a measure of psychological wellbeing at the commencement and termination of counselling. Motivation for counselling was not found to be significantly related to outcomes. The results indicate that the association between motivation and outcomes may be weaker in young people as compared with adults. However, a number of design factors may also account for the non-significant findings: insufficient participants, marginal reliability of the motivation measure and social desirability effects

A journey to client and therapist mutuality in person-centered psychotherapy: a case study

This aim of this case study was to build theory on the development of client–therapist mutuality in person-centered psychotherapy. A case study focusing on a 42-year-old female client who had presented for therapy following trauma within interpersonal relationships has been used. A reflective, theory-building, case study method was adopted that used data gathered from verbatim session notes and research interviews between the therapist (first author) and research supervisor (second author). Three primary therapeutic processes that contributed to the development of mutuality are discussed. First, the development of mutual empathy in the relationship; second, strategies for disconnection and staying out of relationship are identified. Third, client agency and mutuality is explored. In conclusion the study proposes that mutuality is a key construct within person-centered psychotherapy and develops as a natural consequence of the presence of Rogers’ therapeutic conditions

A case for taking the dual role of counsellor-researcher in qualitative research

This is an Accepted Manuscript of an article published by Taylor & Francis in Qualitative Research in Psychology on 3rd August 2016, available online: https://doi.org/10.1080/14780887.2016.1205694There is ongoing debate about whether the challenges of practice-based research in counselling, with clients’ discourses providing the raw data, can be overcome. This article begins by considering the argument of whether taking a dual role of counsellor-researcher within case study research is a legitimate qualitative approach. A case example using sand-tray in short-term therapy with adults from a pluralistic perspective is provided to demonstrate how the challenges of the dual role can be managed to produce effective research findings. It is suggested that this approach closes the gap between research and practice to produce findings that are highly relevant to the counselling context. The ethical considerations of taking a dual role of counsellor-researcher are considered, and opportunities and challenges when adopting this approach are identified

The Life Cycle Assessment of Cyanide Containers in Ghana

As a precious metal gold has been valued by humanity from time immemorial. Today gold is turned into gold bars forming the basis of the World’s international monetary system. When complexed in ore gold needs to undergo metallurgical extraction processes to eliminate unwanted ions before being smelted and used as the metal. Cyanide is used during these metallurgical processes. The economy of the West African country of Ghana relies heavily on gold production for its economic sustainability. Most of the gold mining companies in Ghana have international origins and receive most of their input for gold extraction from international sources. Sodium cyanide is imported into Ghana in  wooden intermediate bulk containers for further distribution to the mining companies. A life cycle assessment was completed to determine the burden that this packaging, which includes the wooden intermediate bulk container, a polyethylene liner and a polypropylene liner places on the environment when they are disposed. The International Organisation of Standardisation (ISO) 14040 management standard was used as a methodological framework in which the goal and scope was defined, a life cycle inventory and life cycle impact assessment was conducted. This enabled the most important issues to be identified. In the final phase consistency, completeness and sensitivity tests were completed and the results interpreted.

The Impact of Parameterized Convection on the Simulation of Crop Processes

Global climate and weather models are a key tool for the prediction of future crop productivity, but they all rely on parameterizations of atmospheric convection, which often produce significant biases in rainfall characteristics over the tropics. The authors evaluate the impact of these biases by driving the General Large Area Model for annual crops (GLAM) with regional-scale atmospheric simulations of one cropping season over West Africa at different resolutions, with and without a parameterization of convection, and compare these with a GLAM run driven by observations. The parameterization of convection produces too light and frequent rainfall throughout the domain, as compared with the short, localized, high-intensity events in the observations and in the convection-permitting runs. Persistent light rain increases surface evaporation, and much heavier rainfall is required to trigger planting. Planting is therefore delayed in the runs with parameterized convection and occurs at a seasonally cooler time, altering the environmental conditions experienced by the crops. Even at high resolutions, runs driven by parameterized convection underpredict the small-scale variability in yields produced by realistic rainfall patterns. Correcting the distribution of rainfall frequencies and intensities before use in crop models will improve the process-based representation of the crop life cycle, increasing confidence in the predictions of crop yield. The rainfall biases described here are a common feature of parameterizations of convection, and therefore the crop-model errors described are likely to occur when using any global weather or climate model, thus remaining hidden when using climate-model intercomparisons to evaluate uncertainty

Regional probabilities of precipitation change: A Bayesian analysis of multimodel simulations

Tebaldi et al. [2005] present a Bayesian approach to determining probability distribution functions (PDFs) of temperature change at regional scales, from the output of a multi-model ensemble, run under the same scenario of future anthropogenic emissions. The main characteristic of the method is the formalization of the two criteria of bias and convergence that the REA method [Giorgi and Mearns, 2002] first quantified as a way of assessing model reliability. Thus, the General Circulation Models (AOGCMs) of the ensemble are combined in a way that accounts for their performance with respect to current climate and a measure of each model's agreement with the majority of the ensemble. We apply the Bayesian model to a set of transient experiments under two SRES scenarios. We focus on predictions of precipitation change, for land regions of subcontinental size. We highlight differences in the PDFs of precipitation change derived in regions where models find easy agreement, and perform well in simulating present day precipitation, compared to regions where models have large biases, and/or their future projections disagree. We compare results from the two scenarios, thus assessing the consequences of the two alternative hypotheses, and present summaries based on their averaging

Some open questions in TDDFT: Clues from Lattice Models and Kadanoff-Baym Dynamics

Two aspects of TDDFT, the linear response approach and the adiabatic local density approximation, are examined from the perspective of lattice models. To this end, we review the DFT formulations on the lattice and give a concise presentation of the time-dependent Kadanoff-Baym equations, used to asses the limitations of the adiabatic approximation in TDDFT. We present results for the density response function of the 3D homogeneous Hubbard model, and point out a drawback of the linear response scheme based on the linearized Sham-Schl\"uter equation. We then suggest a prescription on how to amend it. Finally, we analyze the time evolution of the density in a small cubic cluster, and compare exact, adiabatic-TDDFT and Kadanoff-Baym-Equations densities. Our results show that non-perturbative (in the interaction) adiabatic potentials can perform quite well for slow perturbations but that, for faster external fields, memory effects, as already present in simple many-body approximations, are clearly required.Comment: 15 pages, submitted to Chemical Physic