The SED Machine: a robotic spectrograph for fast transient classification

Current time domain facilities are finding several hundreds of transient astronomical events a year. The discovery rate is expected to increase in the future as soon as new surveys such as the Zwicky Transient Facility (ZTF) and the Large Synoptic Sky Survey (LSST) come on line. At the present time, the rate at which transients are classified is approximately one order or magnitude lower than the discovery rate, leading to an increasing "follow-up drought". Existing telescopes with moderate aperture can help address this deficit when equipped with spectrographs optimized for spectral classification. Here, we provide an overview of the design, operations and first results of the Spectral Energy Distribution Machine (SEDM), operating on the Palomar 60-inch telescope (P60). The instrument is optimized for classification and high observing efficiency. It combines a low-resolution (R$\sim$100) integral field unit (IFU) spectrograph with "Rainbow Camera" (RC), a multi-band field acquisition camera which also serves as multi-band (ugri) photometer. The SEDM was commissioned during the operation of the intermediate Palomar Transient Factory (iPTF) and has already proved lived up to its promise. The success of the SEDM demonstrates the value of spectrographs optimized to spectral classification. Introduction of similar spectrographs on existing telescopes will help alleviate the follow-up drought and thereby accelerate the rate of discoveries.Comment: 21 pages, 20 figure

Expanding Dimensionality in Cinema Color: Impacting Observer Metamerism through Multiprimary Display

Television and cinema display are both trending towards greater ranges and saturation of reproduced colors made possible by near-monochromatic RGB illumination technologies. Through current broadcast and digital cinema standards work, system designs employing laser light sources, narrow-band LED, quantum dots and others are being actively endorsed in promotion of Wide Color Gamut (WCG). Despite artistic benefits brought to creative content producers, spectrally selective excitations of naturally different human color response functions exacerbate variability of observer experience. An exaggerated variation in color-sensing is explicitly counter to the exhaustive controls and calibrations employed in modern motion picture pipelines. Further, singular standard observer summaries of human color vision such as found in the CIE’s 1931 and 1964 color matching functions and used extensively in motion picture color management are deficient in recognizing expected human vision variability. Many researchers have confirmed the magnitude of observer metamerism in color matching in both uniform colors and imagery but few have shown explicit color management with an aim of minimized difference in observer perception variability. This research shows that not only can observer metamerism influences be quantitatively predicted and confirmed psychophysically but that intentionally engineered multiprimary displays employing more than three primaries can offer increased color gamut with drastically improved consistency of experience. To this end, a seven-channel prototype display has been constructed based on observer metamerism models and color difference indices derived from the latest color vision demographic research. This display has been further proven in forced-choice paired comparison tests to deliver superior color matching to reference stimuli versus both contemporary standard RGB cinema projection and recently ratified standard laser projection across a large population of color-normal observers

Comparison of methodologies to estimate state-of-health of commercial Li-ion cells from electrochemical frequency response data

Various impedance-based and nonlinear frequency response-based methods for determining the state-of-health (SOH) of commercial lithium-ion cells are evaluated. Frequency response-based measurements provide a spectral representation of dynamics of underlying physicochemical processes in the cell, giving evidence about its internal physical state. The investigated methods can be carried out more rapidly than controlled full discharge and thus constitute prospectively more efficient measurement procedures to determine the SOH of aged lithium-ion cells. We systematically investigate direct use of electrochemical impedance spectroscopy (EIS) data, equivalent circuit fits to EIS, distribution of relaxation times analysis on EIS, and nonlinear frequency response analysis. SOH prediction models are developed by correlating key parameters of each method with conventional capacity measurement (i.e., current integration). The practical feasibility, reliability and uncertainty of each of the established SOH models are considered: all models show average RMS error in the range 0.75%–1.5% SOH units, attributable principally to cell-to-cell variation. Methods based on processed data (equivalent circuit, distribution of relaxation times) are more experimentally and numerically demanding but show lower average uncertainties and may offer more flexibility for future application

Accurate Colour Reproduction of Human Face using 3D Printing Technology

The colour of the face is one of the most significant factors in appearance and perception of an individual. With the rapid development of colour 3D printing technology and 3D imaging acquisition techniques, it is possible to achieve skin colour reproduction with the application of colour management. However, due to the complicated skin structure with uneven and non-uniform surface, it is challenging to obtain accurate skin colour appearance and reproduce it faithfully using 3D colour printers. The aim of this study was to improve the colour reproduction accuracy of the human face using 3D printing technology. A workflow of 3D colour image reproduction was developed, including 3D colour image acquisition, 3D model manipulation, colour management, colour 3D printing, postprocessing and colour reproduction evaluation. Most importantly, the colour characterisation methods for the 3D imaging system and the colour 3D printer were comprehensively investigated for achieving higher accuracy

Estimation of illuminants from color signals of illuminated objects

Color constancy is the ability of the human visual systems to discount the effect of the illumination and to assign approximate constant color descriptions to objects. This ability has long been studied and widely applied to many areas such as color reproduction and machine vision, especially with the development of digital color processing. This thesis work makes some improvements in illuminant estimation and computational color constancy based on the study and testing of existing algorithms. During recent years, it has been noticed that illuminant estimation based on gamut comparison is efficient and simple to implement. Although numerous investigations have been done in this field, there are still some deficiencies. A large part of this thesis has been work in the area of illuminant estimation through gamut comparison. Noting the importance of color lightness in gamut comparison, and also in order to simplify three-dimensional gamut calculation, a new illuminant estimation method is proposed through gamut comparison at separated lightness levels. Maximum color separation is a color constancy method which is based on the assumption that colors in a scene will obtain the largest gamut area under white illumination. The method was further derived and improved in this thesis to make it applicable and efficient. In addition, some intrinsic questions in gamut comparison methods, for example the relationship between the color space and the application of gamut or probability distribution, were investigated. Color constancy methods through spectral recovery have the limitation that there is no effective way to confine the range of object spectral reflectance. In this thesis, a new constraint on spectral reflectance based on the relative ratios of the parameters from principal component analysis (PCA) decomposition is proposed. The proposed constraint was applied to illuminant detection methods as a metric on the recovered spectral reflectance. Because of the importance of the sensor sensitivities and their wide variation, the influence from the sensor sensitivities on different kinds of illuminant estimation methods was also studied. Estimation method stability to wrong sensor information was tested, suggesting the possible solution to illuminant estimation on images with unknown sources. In addition, with the development of multi-channel imaging, some research on illuminant estimation for multi-channel images both on the correlated color temperature (CCT) estimation and the illuminant spectral recovery was performed in this thesis. All the improvement and new proposed methods in this thesis are tested and compared with those existing methods with best performance, both on synthetic data and real images. The comparison verified the high efficiency and implementation simplicity of the proposed methods

Model facial colour appearance and facial attractiveness for human complexions

Human facial complexion has been a subject of great interest in many areas of science and technology including dermatology, cosmetology, computer graphics, and computer vision. Facial colour appearance conveys vital personal information and influences social interactions and mate choices as contributing factors to perceived beauty, health, and age. How various colour characteristics affect facial preference and whether there are cultural differences are not fully understood. On the other hand, facial colour appearance cannot be simply quantified by colour measurement. Facial colour perception is distinctive. The perceptual aspects of facial colour appearance haven’t been precisely investigated. The present study aims to better understand the human colour perception of facial complexions. Psychophysical experiments were carried out to assess facial colour preference and facial colour appearance, respectively. A set of facial images of real human faces were used and the colour was rigorously controlled in those experiments so that the facial colour appearance could be evaluated based on the realistic skin models. Experiments on colour preference provided a thorough assessment of the relationships between various facial colour characteristics and preference judgements and meanwhile revealed large cultural differences between Caucasian and Chinese populations. A useful and repeatable analytical framework for facial preference modelling was provided. This work contributes to the growing body of research using realistic skin models and highlights the importance of examining various colour cues utilized in facial preference evaluation. Experiments on colour appearance for the first time precisely measured the overall colour perception of facial appearance. New indices WIS, RIS, and YIS were developed to accurately quantify perceived facial whiteness, redness, and yellowness. The perceptual difference between the colour appearance of the face stimuli and the nonface stimuli was discovered. Taken together, the present study shed new light on how our visual system perceives and processes colour information on human faces

Electrode, electrocatalyst and electrolyte development for hybrid redox flow batteries

The development of new electrochemical devices and their subsequent widespread adoption alongside our energy grids is critical to support the incoming wave of renewable energy generation and the transition to net zero. Hybrid redox flow batteries are a promising alternative energy storage technology that could ultimately provide inexpensive and sustainable large scale energy storage solutions compared to their lithium-based counterparts. Technological improvements rely on improved understanding of the processes occurring in these devices. This thesis focuses on three aspects essential to all electrochemical devices – the electrode, electrocatalyst and electrolyte. First, electrochemical and tomographic imaging analyses are combined to understand the effect of electrode microstructure properties on the performance of a non-aqueous redox flow battery. With the help of a one dimensional model, mass-transfer coefficients are gathered from the experimentally determined polarisation curves and affirm the results positively linking electrode permeability to overall cell performance. Second, the synthesis and optimisation of a multifunctional, nitrogen-doped carbon based electrocatalyst is outlined. The active site of the electrocatalyst is examined using a suite of physical characterisation techniques and is shown to have intriguing versatility across the pH spectrum towards catalysing both oxygen and hydrogen fundamental reactions. This catalyst is then tested, with a variety of success, in two fuel cell devices and, alongside the electrodes tested in the first section, in a hydrogen-manganese hybrid redox flow battery. Finally, the aqueous liquid electrolyte involved in this hybrid redox flow battery is scrutinised. Two in-operando analytical techniques are developed, providing improved handles on real-time solution-phase manganese species concentration in the electrolyte. The production of solid manganese oxides significantly alters solution equilibria making the deconvolution of electrochemical and adjacent, simultaneous chemical processes complex.Open Acces

A panchromatic view of the evolution of supermassive black holes

This PhD Thesis is devoted to the accurate analysis of the physical properties of Active Galactic Nuclei (AGN) and the AGN/host-galaxy interplay. Due to the broad-band AGN emission (from radio to hard X-rays), a multi-wavelength approach is mandatory. Our research is carried out over the COSMOS field, within the context of the XMM-Newton wide-field survey. To date, the COSMOS field is a unique area for comprehensive multi-wavelength studies, allowing us to define a large and homogeneous sample of QSOs with a well-sampled spectral coverage and to keep selection effects under control. Moreover, the broad-band information contained in the COSMOS database is well-suited for a detailed analysis of AGN SEDs, bolometric luminosities and bolometric corrections. In order to investigate the nature of both obscured (Type-2) and unobscured (Type-1) AGN, the observational approach is complemented with a theoretical modelling of the AGN/galaxy co-evolution. The X-ray to optical properties of an X-ray selected Type-1 AGN sample are discussed in the first part. The relationship between X-ray and optical/UV luminosities, parametrized by the spectral index αox, provides a first indication about the nature of the central engine powering the AGN. Since a Type-1 AGN outshines the surrounding environment, it is extremely difficult to constrain the properties of its host-galaxy. Conversely, in Type-2 AGN the host-galaxy light is the dominant component of the optical/near-IR SEDs, severely affecting the recovery of the intrinsic AGN emission. Hence a multi-component SED-fitting code is developed to disentangle the emission of the stellar populationof the galaxy from that associated with mass accretion. Bolometric corrections, luminosities, stellar masses and star-formation rates, correlated with the morphology of Type-2 AGN hosts, are presented in the second part, while the final part concerns a physically-motivated model for the evolution of spheroidal galaxies with a central SMBH. The model is able to reproduce two important stages of galaxy evolution, namely the obscured cold-phase and the subsequent quiescent hot-phase

The influence of the skin colour on the perceived attributes

Skin colour data are important for many applications such as medical, imaging, cosmetics. The present study was aimed to collect a comprehensive skin colour database, and to study the impact of the skin colour on the variety of facial impression attributes. Although many researchers and engineers have collected skin data，few of them studied the skin colours to measure the same locations on a large number of subjects from different ethnic groups using the same colour measuring instruments. As for studying the impact of the skin colour on the visual perceptions, many studies investigated the impact of the skin colour on the attractiveness, health and youth. Limited previous studies investigated the impact of the skin colour on the other impression attributes. The present study was divided into two experiments, Experiments 1 and 2. Experiment 1 was to accumulate the skin colour database, named the Leeds Liverpool skin colour (LLSC). It included skin colours of 188 people from four ethnic groups (Caucasian, Oriental, South Asian and African) and both genders. Three colour measuring methods were used to accumulate the skin colour of each subject’s 10 locations including facial locations (forehead, cheekbone, cheek, nose tip, chin and neck) and body locations (the back of the hand, inner forearm, outer forearm and fingertip). The colour measuring methods included a tele-spectroradiometer (TSR), a spectrophotometer (SP) and a set of skin colour chart used as a visual aid. Also, a characterised digital camera controlled by an imaging system was used to collect facial images. Before the data collection, the short-term repeatability of different settings of the TSR and the SP on measuring human skin colour in vivo was determined. And this was used to settle the measurement protocols of the two instruments. The LLSC database was later used to investigate the skin colour distribution between ethnic groups, between genders, between measuring methods. A skin whiteness and blackness scales based on the CIELAB L* and Cab* scales in CIELAB was developed by referencing the vividness and depth formulae, which was developed by Berns (2000). It was found that these scales and CIELAB hue angle can describe well the property of skin colour of each ethnic group. Experiment 2 was to investigate the impact of the skin colour on the facial impression attributes. Based on the LLSC database, the gamut of skin colour was defined. Twenty-three attributes used to describe facial skin colours were accumulated. They were classified into two groups (appearance and impression). Two experiments were carried out on a monitor to understand the impact of the skin colour on the perceived facial impression attributes. The first experiment (Experiment 2.1) was to study the relationship between different attributes by 10 observers. The results showed that only four dimensions were required to describe skin facial colours, which were named Likeable, Sociable, Feminine and Youth. The health was also selected because the traditional Chinese medicine has interested in it. The second experiment (Experiment 2.2) was to scale facial images selected from two ethnic groups and both genders by using these five impression attributes by 24 Chinese observers. The experimental results showed that there were systematic patterns between the impression attributes and the whiteness and hue angle scales. There are some differences between these images for each impression. The ethnic group had an impact on the judgement, but the difference between the Oriental and Caucasian female images was limited. Finally, mathematical models were successfully developed to predict the impressions from the skin whiteness and hue angle data

Methods for constructing 3D geological and geophysical models of flood basalt provinces

In this thesis, realistic 3D geological models of flood basalt provinces are constructed. These models are based on outcrop observations and remote sensing data from the North Atlantic Igneous Province, collected by a variety of methods including terrestrial laser scanning. Geophysical data are added to the models to make them suitable for generating synthetic seismic data. Flood basalt provinces contain a number of different volcanic facies, distinguished by their outcrop appearance and physical properties. These include tabular-classic and compound-braided lava flows, intrusions and hyaloclastites. 3D models are constructed for tabular-classic lava flows based on satellite data from Iceland and laser scanning data from a variety of locations. Models for compound-braided lava flows are based on terrestrial laser scanning data and field observations from the Faroe Islands and the Isle of Skye. An additional finding of this work is that volcanic facies can be differentiated in wireline log data from boreholes. Facies show characteristic velocity distributions which can be linked to onshore observations and used to understand volcanic facies in offshore boreholes. Data from boreholes on the Faroe Islands are used to add seismic velocities to the 3D geological models above. This thesis also develops methods and workflows for constructing 3D geological models of flood basalt lava flows. The collection of digital 3D data using terrestrial laser scanning is evaluated, and data processing workflows are developed