Agile Development of Linux Schedulers with Ekiben

Kernel task scheduling is important for application performance, adaptability to new hardware, and complex user requirements. However, developing, testing, and debugging new scheduling algorithms in Linux, the most widely used cloud operating system, is slow and difficult. We developed Ekiben, a framework for high velocity development of Linux kernel schedulers. Ekiben schedulers are written in safe Rust, and the system supports live upgrade of new scheduling policies into the kernel, userspace debugging, and bidirectional communication with applications. A scheduler implemented with Ekiben achieved near identical performance (within 1% on average) to the default Linux scheduler CFS on a wide range of benchmarks. Ekiben is also able to support a range of research schedulers, specifically the Shinjuku scheduler, a locality aware scheduler, and the Arachne core arbiter, with good performance.Comment: 13 pages, 5 figures, submitted to Eurosys 202

A precise optical transmission spectrum of the inflated exoplanet WASP-52b

We have measured a precise optical transmission spectrum for WASP-52b, a highly inflated hot Jupiter with an equilibrium temperature of 1300 K. Two transits of the planet were observed spectroscopically at low resolution with the auxiliary-port camera (ACAM) on the William Herschel Telescope (WHT), covering a wide range of 4000-8750 \AA. We use a Gaussian process approach to model the correlated noise in the multi-wavelength light curves, resulting in a high precision relative transmission spectrum with errors on the order of a pressure scale height. We attempted to fit a variety of different representative model atmospheres to the transmission spectrum, but did not find a satisfactory match to the entire spectral range. For the majority of the covered wavelength range (4000-7750 \AA) the spectrum is flat, and can be explained by an optically thick and grey cloud layer at 0.1 mbar, but this is inconsistent with a slightly deeper transit at wavelengths $> 7750$ \AA. We were not able to find an obvious systematic source for this feature, so this opacity may be the result of an additional unknown absorber.Comment: Submitted to MNRAS 17 Jan 2017, revised version after comments from reviewer, 12 pages, 10 figure

Virtual Reality Applied to Welder Training

Welding is a challenging, risky, and time-consuming profession. Recently, there has been a documented shortage of trained welders, and as a result, the market is pushing for an increase in the rate at which new professionals are trained. To address this growing demand, training institutions are exploring alternative methods to train future professionals with the goals of improving learner retention of information, shortening training periods, and lowering associated expenses. The emergence of virtual reality technologies has led to initiatives to explore their potential for welding training. Multiple studies have suggested that virtual reality training delivers comparable, or even superior, results when compared to more conventional approaches, with shorter training times and reduced costs in consumables. Additionally, virtual reality allows trainees to try out different approaches to their work. The primary goal of this dissertation is to develop a virtual reality welding simulator. To achieve this objective effectively, the creation of a classification system capable of identifying the simulator’s key characteristics becomes imperative. Therefore, the secondary objective of this thesis is to develop a classification system for the accurate evaluation and comparison of virtual reality welding simulators. Regarding the virtual reality welding simulation, the HTC VIVE Pro 2 virtual reality equipment was employed, to transfer the user’s action from the physical to the virtual world. Within this virtual environment, it was introduced a suite of welding tools and integrated a Smoothed Particle Hydrodynamics simulator to mimic the weld creation. After conducting comprehensive testing that revealed certain limitations in welding quality and in the simulator performance, the project opted to incorporate a Computational Fluid Dynamics (CFD) simulator. The development of the CFD simulator proved to be a formidable challenge, and regrettably, its complete implementation was unattainable. Nevertheless, the project delved into three distinct grid architectures, from these, the dynamic grid was ultimately implemented. It also proficiently integrated two crucial solvers for the Navier-Stokes equations. These functions were implemented in the Graphics Processing Unit (GPU), to improve their efficiency. Upon comparing GPU and Central Processing Unit (CPU) performance, the project highlighted the substantial computational advantages of GPUs and the advantages it brings to fluid simulations.A soldadura é uma profissão exigente, perigosa e que requer um grande investimento de tempo para alcançar resultados satisfatórios. Recentemente, tem sido registada uma falta de profissionais qualificados na área da soldadura. Como resultado, o mer cado está a pressionar para um aumento do ritmo a que os novos trabalhadores são formados. Para responder a esta crescente procura, as instituições de formação estão a explorar métodos alternativos para formar futuros profissionais, com o objetivo de melhorar a retenção de informação, encurtar os períodos de treino e reduzir as despe sas associadas. Com o desenvolvimento de tecnologias nas áreas de realidade virtual e realidade aumentada, têm surgido iniciativas para explorar o potencial destas na formação de soldadura. Vários estudos sugeriram que a formação em realidade virtual proporciona resultados comparáveis, ou mesmo superiores, aos de abordagens mais convencionais, com tempos de formação mais curtos e reduções nos custos de consumíveis. Além disso, a realidade virtual permite aos formandos experimentar diferentes abordagens ao seu trabalho. O objetivo principal desta dissertação é o desenvolvimento de um simulador de soldadura em realidade virtual. Para atingir este objetivo de forma eficaz, torna-se imperativa a criação de um sistema de classificação capaz de identificar as características chave do simulador. Assim, o objetivo secundário desta dissertação é desenvolver um sistema de classificação para a avaliação e comparação precisas de simuladores de soldadura em realidade virtual. Relativamente ao simulador de soldadura em realidade virtual, foi utilizado o kit de realidade virtual HTC VIVE Pro 2, para transferir as ações do utilizador no mundo físico para o mundo virtual. No ambiente virtual, foi introduzido um con junto de ferramentas de soldadura e integrado um simulador de Hidrodinâmica de Partículas Suavizadas para simular a criação da solda. Após a realização de testes exaustivos que revelaram algumas limitações na qualidade da solda e no desempenho do simulador, o projeto optou por incorporar um simulador de Dinâmica de Fluidos Computacional (CFD). O desenvolvimento do simulador CFD revelou-se um desa fio formidável e, infelizmente, não foi possível completar a sua implementação. No entanto, o projeto aprofundou três arquiteturas de grelha distintas, das quais foi implementada a grelha dinâmica. O projeto também implementou duas funções cru ciais para resolver as equações de Navier-Stokes. As funções relativas ao simulador de fluidos foram implementadas na Unidade de Processamento Gráfico (GPU), a fim de melhorar a sua eficiência. Ao comparar o desempenho da GPU com o da Unidade Central de Processamento (CPU), o projeto evidenciou os beneficios computacionais das GPUs e as vantagens que trazem para as simulações de fluidos

Effects of moderate electric fields on the post-harvest preservation of chestnuts

Ohmic heating (OH) was evaluated as a post-harvest technology to improve chestnuts shelf-life (Castanea sativa Mill.) by controlling molds and insect larvae proliferation. Chestnuts were processed by OH at 35, 45, and 55 °C and compared with untreated fruits and the conventional hydrothermal technology (HT - 50 °C for 45 min), which is the process currently used by the chestnut industry. Shelf-life studies were carried out at different atmospheric conditions for 60 days: (i) 25 °C and 40% relative humidity (RH); (ii) 5 °C and 70% RH. The results show that the OH conducted at 55 °C (OH-55 °C), combined with storage at 5 °C, was more effective in controlling molds and larvae growth than the other treatments. Moreover, under these conditions, chestnuts shelf-life could be extended for 60 days without substantial changes in the fruits color and texture. After the OH-55 °C treatment, lower losses of some nutrients and vitamin C were registered compared to HT. This study demonstrates for the first time that OH has the potential to be used by the chestnut industry for the post-harvest disinfestation of this fruit.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Enrique Pino-Hernández is a recipient of a fellowship supported by an advanced doctoral training program (call NORTE-69-2015-15), funded by the European Social Fund under the scope of Norte2020 – Programa Operacional Regional do Norte (NORTE-08-5369-FSE 000036). Ricardo N. Pereira and Luís Abrunhosa acknowledge FCT for their Assistant Research contract obtained under CEEC Individual 2017: reference CEECIND/02903/2017 and CEECIND/00728/2017, respectively.info:eu-repo/semantics/publishedVersio

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 103 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5

Using the example of the tidal stream of the Milky Way globular cluster Palomar 5 (Pal 5), we demonstrate how observational data on streams can be efficiently reduced in dimensionality and modeled in a Bayesian framework. Our approach combines detection of stream overdensities by a Difference-of-Gaussians process with fast streakline models, a continuous likelihood function built from these models, and inference with MCMC. By generating $\approx10^7$ model streams, we show that the geometry of the Pal 5 debris yields powerful constraints on the solar position and motion, the Milky Way and Pal 5 itself. All 10 model parameters were allowed to vary over large ranges without additional prior information. Using only SDSS data and a few radial velocities from the literature, we find that the distance of the Sun from the Galactic Center is $8.30\pm0.25$ kpc, and the transverse velocity is $253\pm16$ km/s. Both estimates are in excellent agreement with independent measurements of these quantities. Assuming a standard disk and bulge model, we determine the Galactic mass within Pal 5's apogalactic radius of 19 kpc to be $(2.1\pm0.4)\times10^{11}$ M$_\odot$. Moreover, we find the potential of the dark halo with a flattening of $q_z = 0.95^{+0.16}_{-0.12}$ to be essentially spherical within the radial range that is effectively probed by Pal 5. We also determine Pal 5's mass, distance and proper motion independently from other methods, which enables us to perform vital cross-checks. We conclude that with more observational data and by using additional prior information, the precision of this method can be significantly increased.Comment: 28 pages, 14 figures, submitted to ApJ (revised version), comments welcom

Design and prototyping of a network-enabled low-cost low-power seismic sensor monitoring system

Esta tese explora recentes desenvolvimentos em tecnologias de informação, comunicações e sensores no campo da sismologia. A tese aborda o potencial das redes de monitorização sísmica de elevada densidade na melhoria da resolução da actividade sísmica observada e, consequentemente, na melhor compreensão dos processos físicos que estão na base da ocorrência de terramotos. A tese argumenta que a tecnologia de sistemas de microelectromecânica (MEMS), usada na produção de acelerómetros de pequena dimensão, tem aplicabilidade e elevado potencial no domínio da sismologia. Acelerómetros MEMS já facilitaram a instalação de redes sísmicas de elevada densidade com superior resolução espacial pela Universidade da Califórnia (Rede Sísmica Comunitária) e pela Universidade de Évora (Rede Sísmica de Sensores do Alentejo), esta última ainda em fase de instalação. Neste contexto, a tese descreve o trabalho conduzido no desenho e desenvolvimento de sistemas de sensores baseados em acelerómetros MEMS. Este trabalho inclui a conceptualização de componentes de arquitectura usados para a implementação de quatro protótipos. Adicionalmente, foram também desenvolvidos os componentes necessários para a operação e gestão da rede de sensores, que inclui servidores dedicados a operar software especificamente desenvolvido neste trabalho. A tese descreve também a instalação e avaliação de protótipos, usando como base de comparação uma estação sísmica de elevado desempenho, recorrendo inclusivamente à actividade sísmica resultante de dois eventos sísmicos. A tese conclui que a arquitectura conceptualizada para o sistema sensor e para a rede de sensores demonstrou ser eficaz. Adicionalmente, embora a tecnologia MEMS seja promissora, ainda exibe limitações que limitam a sua aplicabilidade no domínio da sismologia, especificamente na observação de eventos sísmicos moderados e fortes. Conclui-se também que a instalação de acelerómetros MEMS em conjunto com sismómetros pode trazer benefícios na observação de actividade sísmica. Espera-se também que futuras gerações de acelerómetros MEMS possam ter uma adoção generalizada na sismologia; ABSTRACT: This thesis exploits advances in information technologies, communications and sensor systems to the field of seismology. It addresses the potential for high-density networks for seismic monitoring aiming to improve the resolution of the recorded seismic activity and, consequently, to improve the understanding of the physical processes that cause earthquakes, as well as to gather more detailed seismic characterisation of studied regions. It argues that microelectromechanical systems (MEMS) technology, used to produce small size accelerometers, has a potential application in seismology. Indeed, MEMS accelerometers have enabled the deployment of high-density seismic networks capable of monitoring seismic activity with high spatial resolution, such as CalTech's Community Seismic Network (CSN) and University of Évora’s SSN-Alentejo, currently in the deployment phase. In this context, this thesis describes the work conducted to design and develop low-cost seismic sensor systems, based on low-cost MEMS accelerometers. This work includes the conceptualisation of the architectural components that were implemented in four prototypes. Moreover, server-side components, necessary to operate and manage the sensor network, as well as to provide visualisation tools for users, are also developed and presented. This work also describes the field deployment and evaluation of selected prototypes, using a high-performance seismic station as the reference sensor for comparison, based on generated signals and two recorded seismic events. It is concluded that the herein conceptualised architecture for the high-dense network and sensor prototypes has been demonstrated to be effective. Moreover, albeit promising, MEMS accelerometers still exhibit performance limitations constraining their application in seismology addressing moderate and strong motion. In addition, MEMS accelerometers characteristics complement seismometers, thus installing MEMS accelerometers with seismometers, may provide additional insights concerning seismic activity and seismology in general. It is also expected that next generation MEMS accelerometers will be capable to compete with traditional seismometers, becoming the de facto technology in seismology

High-resolution survey for planetary companions to young stars in the Taurus Molecular Cloud

Direct imaging in the infrared at the diffraction limit of large telescopes is a unique probe of the properties of young planetary systems. We survey 55 single class I and class II stars in Taurus in the L' filter using natural and laser guide star adaptive optics and the near-infrared camera (NIRC2) of the Keck II telescope, in order to search for planetary mass companions. We use both reference star differential imaging and kernel phase techniques, achieving typical 5-sigma contrasts of ~6 magnitudes at separations of 0.2" and ~8 magnitudes beyond 0.5". Although we do not detect any new faint companions, we constrain the frequency of wide separation massive planets, such as HR 8799 analogues. We find that, assuming hot-start models and a planet distribution with power-law mass and semi-major axis indices of -0.5 and -1, respectively, less than 20% of our target stars host planets with masses >2 MJ at separations >10 AU.Comment: 16 pages, 14 figures, accepted for publication in MNRA