Laser diode area melting for high speed additive manufacturing of metallic components

Additive manufacturing processes have been developed to a stage where they can now be routinely used to manufacture net-shape high-value components. Selective Laser Melting (SLM) comprises of either a single or multiple deflected high energy fibre laser source(s) to raster scan, melt and fuse layers of metallic powdered feedstock. However this deflected laser raster scanning methodology is high cost, energy inefficient and encounters significant limitations on output productivity due to the rate of feedstock melting. This work details the development of a new additive manufacturing process known as Diode Area Melting (DAM). This process utilises customised architectural arrays of low power laser diode emitters for high speed parallel processing of metallic feedstock. Individually addressable diode emitters are used to selectively melt feedstock from a pre-laid powder bed. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials. The melting capabilities of the DAM process were tested for low melting point eutectic BiZn2.7 elemental powders and higher temperature pre-alloyed 17-4 stainless steel powder. The process was shown to be capable of fabricating controllable geometric features with evidence of complete melting and fusion between multiple powder layers

THE EFFICACY OF FEEDBACK IN THE FIRST YEAR PROGRAMME: A COMPARISON OF THE VIEWS OF STUDENTS AND STAFF

Feedback has been defined as "information about the gap between actual performance level and the reference level, which is subsequently used to alter that gap". It is now widely acknowledged that feedback forms an essential part of the learning cycle, allowing students to assess their performance and make improvements to future work. However, despite acceptance of the importance of feedback by academics, results from the recent National Student Survey (2005) have highlighted students' general dissatisfaction with the feedback they receive. The purpose of this study was to examine the efficacy of feedback on the first year of the Biological Sciences degree at the University of Leicester, by comparison of the perceptions of students and staff on a number of aspects of the current feedback process. Although a structured approach to giving feedback is encouraged within the School of Biological Sciences, there will be remaining differences in the way staff and students conceptualise the roles of feedback and its format. The views of students studying on the 1st and 2nd years of the Biological Sciences degree were ascertained using a questionnaire addressing various aspects of feedback including, quantity, timing, use and quality. The response rates to the questionnaire were high for both years and the views of students with a range of academic abilities were represented; statistical analysis showed the data obtained to be reliable. In addition, focus groups were used to further explore the views of 1st year students. Semi-structured discussions were led by non-teaching staff, allowing for an informal environment to encourage full participation from students with a range of academic abilities. Staff views on the feedback process were sought during semi-structured one-on-one interviews, again allowing an informal environment for discussion. The staff cohort comprised the majority of 1st year module course convenors, a group of 1st year personal tutors, representative of most departments within the School of Biological Sciences and staff from the Student Learning Centre

A Low-Cost Smartphone Sensor-Based UV Camera for Volcanic SO2 Emission Measurements

Recently, we reported on the development of low-cost ultraviolet (UV) cameras, based on the modification of sensors designed for the smartphone market. These units are built around modified Raspberry Pi cameras (PiCams; ≈USD 25), and usable system sensitivity was demonstrated in the UVA and UVB spectral regions, of relevance to a number of application areas. Here, we report on the first deployment of PiCam devices in one such field: UV remote sensing of sulphur dioxide emissions from volcanoes; such data provide important insights into magmatic processes and are applied in hazard assessments. In particular, we report on field trials on Mt. Etna, where the utility of these devices in quantifying volcanic sulphur dioxide (SO2) emissions was validated. We furthermore performed side-by-side trials of these units against scientific grade cameras, which are currently used in this application, finding that the two systems gave virtually identical flux time series outputs, and that signal-to-noise characteristics of the PiCam units appeared to be more than adequate for volcanological applications. Given the low cost of these sensors, allowing two-filter SO2 camera systems to be assembled for ≈USD 500, they could be suitable for widespread dissemination in volcanic SO2 monitoring internationally

RELIABILITY OF DIFFERENT METHODS OF DETERMINING INDIVIDUAL INTER-STROKE INTERVALS IN SPRINT KAYAKING

The purpose of this study was to explore the reliability of methods for rapidly determining inter-stroke intervals (ISI) of individual kayakers. One participant performed two 150 m trials at a rate of 80 single-strokes/min. ISI were calculated using two criterion measures, visual identification of blade immersion (VID) and peaks in longitudinal acceleration of the kayak hull (ACC). These were compared to ISI from peak footrest force (FRP), initiation of footrest force (FRT), paddle Y axis rotational velocity (PAP) and paddle X axis acceleration (PAA). Least products regression analysis (LPR) revealed that FRP showed the highest reliability, with no fixed or proportional bias compared to VID or ACC. High ISI during the initial strokes influenced the results of the LPR, as such a framework for investigating the reliability of ISI using LPR is suggested where the initial strokes are removed prior to analysis

The development of a low-cost, near infrared, high-temperature thermal imaging system and its application to the retrieval of accurate lava lake temperatures at Masaya volcano, Nicaragua

Near infrared thermal cameras can provide useful low-cost imaging systems for high temperature applications, as an alternative to ubiquitous mid-/long-wavelength infrared systems. Here, we present a new Raspberry Pi-based near infrared thermal camera for use at temperatures of ≈ > 500 °C. We discuss in detail the building of the optical system, calibration using a Sakuma-Hattori model and quantification of uncertainties in remote temperature retrievals. We then present results from the deployment of the system on Masaya Volcano, Nicaragua, where the active lava lake was imaged. Temperatures reached a maximum of 1104 ± 14 °C and the lake radiati ve power output was found to range between 30 and 45 MW. To the best of our knowledge, this is the first published ground-based data on the thermal characteristics of this relatively nascent lava lake, which became visible in late 2015

The PiSpec: A Low-Cost, 3D-Printed Spectrometer for Measuring Volcanic SO2 Emission Rates

Spectroscopy has been used to quantify volcanic gas emission rates, most commonly SO2, for a number of decades. Typically, commercial spectrometers costing 1000s USD are employed for this purpose. The PiSpec is a new, custom-designed, 3D-printed spectrometer based on smartphone sensor technology. This unit has ≈1 nm spectral resolution and a spectral range in the ultraviolet of ≈280–340 nm, and is specifically configured for the remote sensing of SO2 using Differential Optical Absorption Spectroscopy (DOAS). Here we report on the first field deployment of the PiSpec on a volcano, to demonstrate the proof of concept of the device’s functionality in this application area. The study was performed on Masaya Volcano, Nicaragua, which is one of the largest emitters of SO2 on the planet, during a period of elevated activity where a lava lake was present in the crater. Both scans and traverses were performed, with resulting emission rates ranging from 3.2 to 45.6 kg s−1 across two measurement days; these values are commensurate with those reported elsewhere in the literature during this activity phase (Aiuppa et al., 2018; Stix et al., 2018). Furthermore, we tested the PiSpec’s thermal stability, finding a wavelength shift of 0.046 nm/∘C between 2.5 and 45∘C, which is very similar to that of some commercial spectrometers. Given the low build cost of these units (≈500 USD for a one-off build, with prospects for further price reduction with volume manufacture), we suggest these units hold considerable potential for volcano monitoring operations in resource limited environments

Thermal Sensation in Older People with and without Dementia Living in Residential Care: New Assessment Approaches to Thermal Comfort Using Infrared Thermography

The temperature of the indoor environment is important for health and wellbeing, especially at the extremes of age. The study aim was to understand the relationship between self-reported thermal sensation and extremity skin temperature in care home residents with and without dementia. The Abbreviated Mental Test (AMT) was used to discriminate residents to two categories, those with, and those without, dementia. After residents settled and further explanation of the study given (approximately 15 min), measurements included: tympanic membrane temperature, thermal sensation rating and infrared thermal mapping of non-dominant hand and forearm. Sixty-nine afebrile adults (60–101 years of age) were studied in groups of two to five, in mean ambient temperatures of 21.4–26.6 °C (median 23.6 °C). Significant differences were observed between groups; thermal sensation rating (p = 0.02), tympanic temperature (p = 0.01), fingertip skin temperature (p = 0.01) and temperature gradients; fingertip-wrist p = 0.001 and fingertip-distal forearm, p = 0.001. Residents with dementia were in significantly lower air temperatures (p = 0.001). Although equal numbers of residents per group rated the environment as ‘neutral’ (comfortable), resident ratings for ‘cool/cold’ were more frequent amongst those with dementia compared with no dementia. In parallel, extremity (hand) thermograms revealed visual temperature demarcation, variously across fingertip, wrist, and forearm commensurate with peripheral vasoconstriction. Infrared thermography provided a quantitative and qualitative method to measure and observe hand skin temperature across multiple regions of interest alongside thermal sensation self-report. As an imaging modality, infrared thermography has potential as an additional assessment technology with clinical utility to identify vulnerable residents who may be unable to communicate verbally, or reliably, their satisfaction with indoor environmental conditions

Kicking foot swing planes and support leg kinematics in rugby place kicking: Differences between accurate and inaccurate kickers

Place kicking is a complex whole-body movement that contributes 45% of the points scored in international Rugby Union. This study compared the kicking foot swing plane characteristics of accurate and inaccurate kickers, underpinned by differences in their support leg and pelvis kinematics at support foot contact, to identify key technique characteristics. Motion capture data (240 Hz) were collected from 33 experienced kickers, and distinct groups of accurate (n = 18) and inaccurate (n = 8) kickers were identified based on their performance characteristics. All accurate kickers were capable of kicking successfully from at least 33.3 m, whereas all inaccurate kickers would have missed left from distances greater than 30.7 m. The accurate group exhibited a moderately shallower swing plane inclination (50.6 ± 4.8° vs. 54.3 ± 2.1°) and directed the plane moderately further to the right of the target (20.2 ± 5.4° vs. 16.7 ± 4.1°). At support foot contact, the accurate group placed their support foot moderately less far behind the ball (0.08 ± 0.08 m vs. 0.12 ± 0.04 m) and positioned their centre of mass moderately further to the support leg side (0.77 ± 0.07 m vs. 0.72 ± 0.01 m) due to a moderately greater stance leg lean (29.3 ± 4.1° vs. 26.8 ± 3.2°). The kicking foot swing plane is highly planar in rugby place kicking but its orientation differs between accurate and inaccurate kickers. These plane characteristics may be controlled by support foot placement and support leg and pelvis kinematics at support foot contact

Low-cost 3D printed 1 nm resolution smartphone sensor-based spectrometer: instrument design and application in ultraviolet spectroscopy.

We report on the development of a low-cost spectrometer, based on off-the-shelf optical components, a 3D printed housing, and a modified Raspberry Pi camera module. With a bandwidth and spectral resolution of ≈60  nm and 1 nm, respectively, this device was designed for ultraviolet (UV) remote sensing of atmospheric sulphur dioxide (SO2), ≈310  nm. To the best of our knowledge, this is the first report of both a UV spectrometer and a nanometer resolution spectrometer based on smartphone sensor technology. The device performance was assessed and validated by measuring column amounts of SO2 within quartz cells with a differential optical absorption spectroscopy processing routine. This system could easily be reconfigured to cover other UV-visible-near-infrared spectral regions, as well as alternate spectral ranges and/or linewidths. Hence, our intention is also to highlight how this framework could be applied to build bespoke, low-cost, spectrometers for a range of scientific applications

Potential for improved radiation thermometry measurement uncertainty through implementing a primary scale in an industrial laboratory

A primary temperature scale requires realising a unit in terms of its definition. For high temperature radiation thermometry in terms of the International Temperature Scale of 1990 this means extrapolating from the signal measured at the freezing temperature of gold, silver or copper using Planck’s radiation law. The difficulty in doing this means that primary scales above 1000 °C require specialist equipment and careful characterisation in order to achieve the extrapolation with sufficient accuracy. As such, maintenance of the scale at high temperatures is usually only practicable for National Metrology Institutes, and calibration laboratories have to rely on a scale calibrated against transfer standards. At lower temperatures it is practicable for an industrial calibration laboratory to have its own primary temperature scale, which reduces the number of steps between the primary scale and end user. Proposed changes to the SI that will introduce internationally accepted high temperature reference standards might make it practicable to have a primary high temperature scale in a calibration laboratory. In this study such a scale was established by calibrating radiation thermometers directly to high temperature reference standards. The possible reduction in uncertainty to an end user as a result of the reduced calibration chain was evaluated