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Lighting controls: evolution and revolution
No full textThe basic function of a lighting system is to provide a defined amount of light to a space according to context-appropriate design criteria while minimising energy use. Lighting control strategies based on occupancy and daylight adaptation have been consistently shown to substantially lower lighting energy use compared to fixed systems, and are now ubiquitous in building energy codes. The adoption of light emitting diodes and the integration of information and communication technologies enable lighting control systems to become smarter with a greater integration of sensing, data processing and connectivity, and to evolve into a platform for both lighting and non-lighting applications. We describe different lighting control strategies and their evolution with a focus on commercial office applications. To illustrate emerging approaches, we then discuss two particular smart lighting systems \u2013 a wireless, distributed lighting control system and a power-over-Ethernet, centralised lighting control system, with cloud connectivity. The role that a connected lighting system can play in the overall building eco-system is then discussed, and new applications and services that are enabled are presented. Finally, we discuss the challenges to the market adoption of connected smart lighting systems, and the arising opportunities for researchers and practitioners to realise one more round of high-value returns offered by lighting systems.Peer reviewed: YesNRC publication: Ye
On the learning curve attrition bias in additive factor modeling
No full textLearning curves are a crucial tool to accurately measure learners skills and give meaningful feedback in intelligent tutoring systems. Here we discuss various ways of building learning curves from empirical data for the Additive Factor model (AFM) and highlight their limitations. We focus on the impact of student attrition, a.k.a. attrition bias. We propose a new way to build learning curves, by combining empirical observations and AFM predictions. We validate this proposition on simulated data, and test it on real datasets.Peer reviewed: YesNRC publication: Ye
On-chip continuously tunable optical delay line based on cascaded Mach-Zehnder interferometers
No full textWe propose a novel integrated optical delay line based on cascaded Mach-Zehnder interferometers. It allows a continuous delay tuning, can achieve wideband operation and is experimentally demonstrated with a delay up to 125 ps.Peer reviewed: YesNRC publication: Ye
OSSOS. VIII. The transition between two size distribution slopes in the scattering disk
No full textThe scattering trans-Neptunian Objects (TNOs) can be measured to smaller sizes than any other distant small-body population. We use the largest sample yet obtained, 68 discoveries, primarily by the Outer Solar System Origins Survey (OSSOS), to constrain the slope of its luminosity distribution, with sensitivity to much fainter absolute H-magnitudes than previous work. Using the analysis technique in Shankman et al., we confirm that a single slope for the H-distribution is not an accurate representation of the scattering TNOs and Centaurs, and that a break in the distribution is required, in support of previous conclusions. A bright-end slope of \u3b1 b = 0.9 transitioning to a faint-end slope \u3b1 f of 0.4\u20130.5 with a differential number contrast c from 1 (a knee) to 10 (a divot) provides an acceptable match to our data. We find that break magnitudes H b of 7.7 and 8.3, values both previously suggested for dynamically hot Kuiper Belt populations, are equally non-rejectable for a range of \u3b1 f and c in our statistical analysis. Our preferred divot H-distribution transitions to \u3b1 f = 0.5 with a divot of contrast c = 3 at H b = 8.3, while our preferred knee H-distribution transitions to \u3b1 f = 0.4 at H b = 7.7. The intrinsic population of scattering TNOs required to match the OSSOS detections is 3
7 106 for H r < 12, and 9
7 104 for H r < 8.66 (D gsim 100 km), with Centaurs having an intrinsic population two orders of magnitude smaller.Peer reviewed: YesNRC publication: Ye
A novel approach for real-time prediction and prevention of tool chipping in intermittent turning machining
No full textAn integrated tool condition monitoring system, based on a novel signal processing approach, for online prediction and prevention of tool chipping in intermittent turning is presented. It identifies the unstable crack propagation features of the prefailure phase, independent of the cutting parameters and workpiece material. A correlation between the chipping size and these features was developed for decision making, to protect machined surfaces. Experimental validation results confirmed the accuracy of the proposed system. The time required for signal processing, decision making and communication with the machine controller allows stopping the operation before part damage. No such system is presently available.Peer reviewed: YesNRC publication: Ye
A rapid and simple single-stage method for Ca separation from geological and biological samples for isotopic analysis by MC-ICP-MS
No full textA new simple and rapid method was developed for the purification of Ca from geological and biological samples. The proposed separation protocol is based on DGA resin and consists of only three elution steps and two types of eluents (6.8 mL 4 mol L 121 HNO3 and 3 mL DI-water), which afford a straightforward separation of Ca with a high yield (95\u201399%), good purity and low blank level. Moreover, a vacuum box was employed which enables Ca purification for a batch of twelve samples within two hours, with greatly improved efficiency compared to conventional gravity flow separation methods. Ca isotopic ratios were measured by multi-collector inductively coupled plasma mass-spectrometry (MC-ICP-MS) using a standard\u2013sample bracketing method. Based on repeated measurements of NIST SRM 915a and Alfa Ca, the long-term reproducibility was evaluated at \ub10.07\u2030 (2SD) for \u3b444/42Ca. The validity of the proposed method was demonstrated by the analysis of thirteen international geological and biological reference materials with satisfactory results which are in good agreement with published values. Therefore, the proposed method can be used for a rapid and efficient determination of stable Ca isotopic ratios in geological and biological samples.Peer reviewed: YesNRC publication: Ye
A system for the measurement of electron stopping powers: proof of principle using a pure \u3b2-emitting source
No full textThe accuracy of the electron stopping powers of elements and compounds is of great importance to medical dosimetry, radiation therapy, and radiation transport simulations. This paper summarises the commissioning of a new high purity Germanium (HPGe) detector and presents a feasibility study confirming the suitability of a method to determine electron stopping power data.
A high-efficiency, HPGe detector was commissioned and found to match the manufacturer's performance specifications. A simple experiment was designed to obtain spectra acquired from a Sr-90/Y-90 radioactive check source with varying thicknesses of absorber (Al and Cu foils) placed between the source and the detector. The entire experimental arrangement was simulated using the EGSnrc radiation transport system. The Monte Carlo model of the detector accurately replicated the detector response to electrons and a quantitative analysis showed that the difference between the simulated and measured spectra was less than 1.5%, using the standard tabulated ICRU 37 stopping power data for the simulations.
Based on the experiment with the low-energy Sr-90/Y-90 source, it is anticipated that this method can be used with a well-characterized quasi-monoenergetic electron beam, as available from a research linear accelerated to yield accurate measurements to validate current tabulated stopping power data.Peer reviewed: YesNRC publication: Ye
An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102
No full textFast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin1,2,3. The only known repeating fast radio burst source4,5,6\u2014FRB 121102\u2014has been localized to a star-forming region in a dwarf galaxy7,8,9 at redshift 0.193 and is spatially coincident with a compact, persistent radio source7,10. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46\u2009
7\u2009105 radians per square metre to +1.33\u2009
7\u2009105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed11,12 only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole10. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula13 or supernova remnant14 surrounding a young neutron star.Peer reviewed: YesNRC publication: Ye