A Review of State-of-the-Art Large Sized Foam Cutting Rapid Prototyping and Manufacturing Technologies.

Purpose – Current additive rapid prototyping (RP) technologies fail to efficiently produce objects greater than 0.5?m3 due to restrictions in build size, build time and cost. A need exists to develop RP and manufacturing technologies capable of producing large objects in a rapid manner directly from computer-aided design data. Foam cutting RP is a relatively new technology capable of producing large complex objects using inexpensive materials. The purpose of this paper is to describe nine such technologies that have been developed or are currently being developed at institutions around the world. The relative merits of each system are discussed. Recommendations are given with the aim of enhancing the performance of existing and future foam cutting RP systems. Design/methodology/approach – The review is based on an extensive literature review covering academic publications, company documents and web site information. Findings – The paper provides insights into the different machine configurations and cutting strategies. The most successful machines and cutting strategies are identified. Research limitations/implications – Most of the foam cutting RP systems described have not been developed to the commercial level, thus a benchmark study directly comparing the nine systems was not possible. Originality/value – This paper provides the first overview of foam cutting RP technology, a field which is over a decade old. The information contained in this paper will help improve future developments in foam cutting RP systems

Using the Finite Element Method to Determine the Temperature Distributions in Hot-wire Cutting.

Hot-wire cutting is a common material removal process used to shape and sculpt plastic foam materials, such as expanded polystyrene (EPS). Due to the low cost and sculpt-ability of plastic foams they are popular materials for large sized (> 1 m³) prototypes and bespoke visual artefacts. Recent developments in robotic foam sculpting machines have greatly increased the ability of hot-tools to sculpt complex geometrical surfaces bringing the subject into the realm of subtractive rapid prototyping/manufacturing. Nevertheless foam cut objects are not being exploited to their full potential due to the common perception that hot-wires are a low accuracy cutting tool. If greater accuracy for hot-wires can be obtained, it could provide a low cost method of producing high value functional engineering parts. Polystyrene patterns for lost foam casting are one such possibility. A nonlinear transient thermal finite element model was developed with the purpose of predicting the kerf width of hot-wire cut foams. Accurate predictions of the kerfwidth during cutting will allow the tool paths to be corrected off-line at the tool definition stage of the CAM process. Finite element analysis software (ANSYS) was used to simulate the hot-wire plastic foam cutting. The material property models were compiled from experimental data and commonly accepted values found in literature. The simulations showed good agreement with the experimental data and thus the model is thought to be reliable. The simulations provide an effective method of predicting kerf widths, under steady state cutting conditions. Limitations and further developments to the model are described

Understanding Heisenberg's 'Magical' Paper of July 1925: a New Look at the Calculational Details

In July 1925 Heisenberg published a paper [Z. Phys. 33, 879-893 (1925)] which ended the period of `the Old Quantum Theory' and ushered in the new era of Quantum Mechanics. This epoch-making paper is generally regarded as being difficult to follow, perhaps partly because Heisenberg provided few clues as to how he arrived at the results which he reported. Here we give details of calculations of the type which, we suggest, Heisenberg may have performed. We take as a specific example one of the anharmonic oscillator problems considered by Heisenberg, and use our reconstruction of his approach to solve it up to second order in perturbation theory. We emphasize that the results are precisely those obtained in standard quantum mechanics, and suggest that some discussion of the approach - based on the direct computation of transition amplitudes - could usefully be included in undergraduate courses in quantum mechanics.Comment: 24 pages, no figures, Latex, submitted to Am. J. Phy

Measuring visual cortical oxygenation in diabetes using functional near-infrared spectroscopy

Aims: Diabetes mellitus affects about 6% of the world’s population, and the chronic complications of the disease may result in macro- and micro-vascular changes. The purpose of the current study was to shed light on visual cortical oxygenation in diabetic individuals. We then aimed to compare the haemodynamic response (HDR) to visual stimulation with glycaemic control, given the likelihood of diabetic individuals suffering from such macro- and micro-vascular insult. Methodology: Thirty participants took part in this explorative study, fifteen of whom had diabetes and fifteen of whom were non-diabetic controls. The HDR, measured as concentrations of oxyhaemoglobin [HbO] and deoxyhaemoglobin [HbR], to visual stimulation was recorded over the primary visual cortex (V1) using a dual-channel oximeter. The stimulus comprised a pattern-reversal checkerboard presented in a block design. Participants’ mean glycated haemoglobin (HbA1c) level (±SD) was 7.2±0.6% in the diabetic group and 5.5±0.4% in the non-diabetic group. Raw haemodynamic data were normalised to baseline, and the last 15 s of data from each ‘stimulus on’ and ‘stimulus off’ condition were averaged over seven duty cycles for each participant. Results: There were statistically significant differences in ∆[HbO] and ∆[HbR] to visual stimulation between diabetic and non-diabetic groups (p<0.05). In the diabetic group, individuals with type 1 diabetes displayed an increased [HbO] (p<0.01) and decreased [HbR] (p<0.05) compared to their type 2 counterparts. There was also a linear relationship between both ∆[HbO] and ∆[HbR] as a function of HbA1c level (p<0.0005). Conclusions: Our findings suggest that fNIRS can be used as a quantitative measure of cortical oxygenation in diabetes. Diabetic individuals have a larger HDR to visual stimulation compared to non-diabetic individuals. This increase in ∆[HbO] and decrease in ∆[HbR] appears to be correlated with HbA1c level

High visibility two photon interference of frequency time entangled photons generated in a quasi phase matched AlGaAs waveguide

We demonstrate experimentally the frequency time entanglement of photon pairs produced in a CW pumped quasi phased matched AlGaAs superlattice waveguide. A visibility of 96.0+-0.7% without background subtraction has been achieved, which corresponds the violation of Bell inequality by 52 standard deviations

Artfully Exploring Quantum Physics

The Art and Light Project has successfully brought together artists and scientists from across the Dunedin community and created a forum for dialogue and understanding. Some beautiful art has been created which culminated in a well-attended exhibition at the Otago Museum. More than 60 years ago, C.P. Snow wrote4 in his wonderful little book of warning, The Two Cultures, that “There seems to be no place where the cultures meet. I am not going to waste time saying that this is a pity. It is much worse than that.” This exercise has attempted to bridge a little of that gap between the cultures of science and the arts. Moreover, I think that both artists and scientists alike would agree that the distinction is an artificial one. To illustrate this we have tried to express in this article the similarities in method and thought between creation—for they are both creative processes—in art and science.Moreover, the science we have tried to portray through this art and this article can be difficult to grasp. The exhibition itself has been a vehicle that has enabled us to engage with an audience that would not perhaps normally be exposed to quantum science. As a public outreach and educational exercise, this project has therefore been a resounding success. More importantly, it was a lot of fun

Effects of glaucoma and snoring on cerebral oxygenation in the visual cortex: a study using functional Near Infrared Spectroscopy (fNIRS)

Purpose: The purpose of this study was to investigate the effects of snoring and glaucoma on the visual Haemodynamic Response (HDR) using functional Near Infrared Spectroscopy (fNIRS). Methods: We recruited 8 glaucoma patients (aged 56-79), 6 habitual snorers (aged 26-61) and 10 healthy control participants (aged 21-78). Glaucoma patients were of varying subtypes and under care of ophthalmologists. Prior to testing visual acuity, blood pressure, heart rate and a medical history were taken. HDRs were recorded over the primary visual cortex (V1) using a reversing checkerboard paradigm. Results & Discussion: All participants showed the characteristic increase of Oxyhaemoglobin concentration ([HbO]) and decrease of Deoxyhaemoglobin concentration ([HbR]) during visual stimulation (p < 0.001, η2 = 0.78). Despite this, there were signifi cant group differences with a large effect size (η2 = 0.28). During visual stimulation normal participants had greater [HbO] compared to snorers and glaucoma patients (p < 0.01). Both glaucoma patients and snorers presented with comparable HDR for [HbO] and [HbR] in V1. Importantly, during visual stimulation, the increased [HbO] in glaucoma patients correlated well with their visual fi elds and self-reported activities of daily living (r = -0.98, r = -0.82, p < 0.05). Both glaucoma patients and snorers presented with an attenuated HDR in V1. Our results suggest a possible vascular link between these conditions

New Zealand and the Suez affair : a theoretical approach to the study of New Zealand's foreign policy responses to the 1956 Suez crisis

More than a quarter of a century has elapsed now since British and French troops stormed the beaches around Port Said in a vain attempt to force the Egyptian Government into accepting a new international convention to govern the passage of shipping through the Suez Canal. From a military standpoint the assault was a complete success - yet the Suez Campaign was not destined to be won or lost on the field of battle. At the United Nations, the Soviet Union and the United States combined, and with the support of the overwhelming majority of the Organisation's membership, forced the British and French to abandon their Suez venture. Australia and New Zealand were the only countries not directly involved in the fracas in Egypt, to actively support the British and French action. New Zealand and the Suez Affair is an attempt to provide some new insights into the Government's decision to support Britain during the crisis, by challenging the generally accepted view that New Zealand's Suez Policy originated in the hearts, rather than the minds, of New Zealand's leaders. The modus operandi employed to achieve this objective is essentially quite simple. Firstly, the available small state literature was examined in an effort to isolate the behaviour patterns that small states generally exhibit. The Government's Suez Policy was then examined and compared with the behaviour patterns suggested by the small state theorists. If, in the course of the analysis, it was found that New Zealand's policy conflicted with what is generally considered to be typical small state behaviour, then it was felt that the accusation of an emotionally based Suez policy would probably be proven a valid one. If on the other hand, New Zealand's policy appeared consistent with the suggested patterns, then it seemed likely that some other explanation would have to be found to explain the Government's actions. It was intended that the theoretical aspect of this work should furnish answers to all these questions. The conclusions that were reached upon completion of the analysis, tended to indicate that New Zealand's Suez Policy was, in fact, typical of the suggested small state patterns, and that contrary to the generally held belief, it was economic necessity and a belief in the rule of inter­ national law, rather than sentimental attachment to Britain, that dictated the Government's Suez Policy