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"Wing, M"
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Computational thinking and thinking about computing
Computational thinking will influence everyone in every field of endeavour. This vision poses a new educational challenge for our society, especially for our children. In thinking about computing, we need to be attuned to the three drivers of our field: science, technology and society. Accelerating technological advances and monumental societal demands force us to revisit the most basic scientific questions of computing.
Journal Article
Particle physics experiments based on the AWAKE acceleration scheme
New particle acceleration schemes open up exciting opportunities, potentially providing more compact or higher-energy accelerators. The AWAKE experiment at CERN is currently taking data to establish the method of proton-driven plasma wakefield acceleration. A second phase aims to demonstrate that bunches of about 10 9 electrons can be accelerated to high energy, preserving emittance and that the process is scalable with length. With this, an electron beam of O (50 GeV) could be available for new fixed-target or beam-dump experiments searching for the hidden sector, like dark photons. The rate of electrons on target could be increased by a factor of more than 1000 compared to that currently available, leading to a corresponding increase in sensitivity to new physics. Such a beam could also be brought into collision with a high-power laser and thereby probe the completely unmeasured region of strong fields at values of the Schwinger critical field. An ultimate goal is to produce an electron beam of O (3 TeV) and collide with an Large Hadron Collider proton beam. This very high-energy electron–proton collider would probe a new regime in which the structure of matter is completely unknown. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration’.
Journal Article
Skin and Mechanoreceptor Contribution to Tactile Input for Perception: A Review of Simulation Models
We review four current quantitative models that simulate the response of mechanoreceptors in the glabrous skin to tactile stimulation. The aim is to inform researchers in psychology, sensorimotor science and robotics who may want to implement this type of quantitative model in their research. This approach proves relevant to understanding of the interaction between skin response and neural activity as it avoids some of the limitations of traditional measurement methods of tribology, for the skin, and neurophysiology, for tactile neurons. The main advantage is to afford new ways of looking at the combined effects of skin properties on the activity of a population of tactile neurons, and to examine different forms of coding by tactile neurons. Here, we provide an overview of selected models from stimulus application to neuronal spiking response, including their evaluation in terms of existing data, and their applicability in relation to human tactile perception.
Journal Article
VHEeP: a very high energy electron–proton collider
Based on current CERN infrastructure, an electron–proton collider is proposed at a centre-of-mass energy of about 9 TeV. A 7 TeV LHC bunch is used as the proton driver to create a plasma wakefield which then accelerates electrons to 3 TeV, these then colliding with the other 7 TeV LHC proton beam. Although of very high energy, the collider has a modest projected integrated luminosity of 10–100 pb
-
1
. For such a collider, with a centre-of-mass energy 30 times greater than HERA, parton momentum fractions,
x
, down to about
10
-
8
are accessible for photon virtualities,
Q
2
, of 1 GeV
2
. The energy dependence of hadronic cross sections at high energies, such as the total photon–proton cross section, which has synergy with cosmic-ray physics, can be measured and QCD and the structure of matter better understood in a region where the effects are completely unknown. Searches at high
Q
2
for physics beyond the Standard Model will be possible, in particular the significantly increased sensitivity to the production of leptoquarks. These and other physics highlights of a very high energy electron–proton collider are outlined.
Journal Article
An Attack Surface Metric
Measurement of software security is a long-standing challenge to the research community. At the same time, practical security metrics and measurements are essential for secure software development. Hence, the need for metrics is more pressing now due to a growing demand for secure software. In this paper, we propose using a software system's attack surface measurement as an indicator of the system's security. We formalize the notion of a system's attack surface and introduce an attack surface metric to measure the attack surface in a systematic manner. Our measurement method is agnostic to a software system's implementation language and is applicable to systems of all sizes; we demonstrate our method by measuring the attack surfaces of small desktop applications and large enterprise systems implemented in C and Java. We conducted three exploratory empirical studies to validate our method. Software developers can mitigate their software's security risk by measuring and reducing their software's attack surfaces. Our attack surface reduction approach complements the software industry's traditional code quality improvement approach for security risk mitigation and is useful in multiple phases of the software development lifecycle. Our collaboration with SAP demonstrates the use of our metric in the software development process.
Journal Article
Discrimination of consonants in quiet and in noise in Mandarin-speaking children with normal hearing
Given the critical role of consonants in speech perception and the lack of knowledge on consonant perception in noise in Mandarin-speaking children, the current study aimed to investigate Mandarin consonant discrimination in normal-hearing children, in relation to the effects of age and signal-to-noise ratios (S/N).
A discrimination task consisting of 33 minimal pairs in monosyllabic words was designed to explore the development of consonant discrimination in five test conditions: 0, -5, -10, -15 dB S/Ns, and quiet.
Forty Mandarin-speaking, normal-hearing children aged from 4;0 to 8;9 in one-year-age increment were recruited and their performance was compared to 10 adult listeners.
A significant main effect of age, test conditions, and an interaction effect between these variables was noted. Consonant discrimination in quiet and in noise improved as children became older. Consonants that were difficult to discriminate in quiet and in noise were mainly velar contrasts. Noise seemed to have less effect on the discrimination of affricates and fricatives, and plosives appeared to be to be more difficult to discriminate in noise than in quiet. Place contrasts between alveolar and palato-alveolar consonants were difficult in quiet.
The findings were the first to reveal typical perceptual development of Mandarin consonant discrimination in children and can serve as a reference for comparison with children with disordered perceptual development, such as those with hearing loss.
Journal Article
Emittance preservation in a plasma-wakefield accelerator
Radio-frequency particle accelerators are engines of discovery, powering high-energy physics and photon science, but are also large and expensive due to their limited accelerating fields. Plasma-wakefield accelerators (PWFAs) provide orders-of-magnitude stronger fields in the charge-density wave behind a particle bunch travelling in a plasma, promising particle accelerators of greatly reduced size and cost. However, PWFAs can easily degrade the beam quality of the bunches they accelerate. Emittance, which determines how tightly beams can be focused, is a critical beam quality in for instance colliders and free-electron lasers, but is particularly prone to degradation. We demonstrate, for the first time, emittance preservation in a high-gradient and high-efficiency PWFA while simultaneously preserving charge and energy spread. This establishes that PWFAs can accelerate without degradation—an essential step toward energy boosters in photon science and multistage facilities for compact high-energy particle colliders.
High beam quality is key for particle-accelerator applications in high-energy physics and photon science. Here, authors demonstrate gigavolt-per meter acceleration of electron bunches in a plasma-wakefield accelerator with no degradation of emittance, while also preserving charge and energy spread.
Journal Article
Assessing the cumulative adverse effects of offshore wind energy development on seabird foraging guilds along the East Coast of the United States
Offshore wind farms are rapidly being permitted along the East Coast of the US, and with subsequent development could cumulatively affect seabird populations. Yet, the seabird guilds most likely at risk of cumulative effects have not been identified. Assessments of cumulative effects must first calculate the cumulative exposure of seabirds to areas suitable for offshore wind farms and then estimate how exposure will affect populations. This paper addresses this first need, and quantifies how three different wind farm siting scenarios could cumulatively expose seven seabird foraging guilds. The coastal bottom gleaner guild (sea ducks) would be exposed at similar rates regardless of siting decision, while other coastal guilds would be exposed at a higher rate when projects are built in shallow areas and close to shore rather than in high-wind areas. The pelagic seabird guild would be exposed at high rates when projects are built in high-wind areas. There was no single offshore wind siting scenario that reduced the cumulative exposure for all guilds. Based upon these findings, we identify the foraging guilds most likely to be cumulatively exposed and propose an approach for siting and mitigation that may reduce cumulative exposure for all guilds.
Journal Article