http://hdl.handle.net/2440/1 2021-01-25T20:52:45Z http://hdl.handle.net/2440/129600 Title: Operation of the ATLAS trigger system in Run 2 Author: Aad, G.; Abbott, B.; Abbott, D.C.; Abud, A.A.; Abeling, K.; Abhayasinghe, D.K.; Abidi, S.H.; AbouZeid, O.S.; Abraham, N.L.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Acharya, B.S.; Achkar, B.; Adam, L.; Bourdarios, C.A.; Adamczyk, L.; Adamek, L.; Adelman, J.; Adersberger, M.; et al. Abstract: The ATLAS experiment at the Large Hadron Collider employs a two-level trigger system to record data at an average rate of 1 kHz from physics collisions, starting from an initial bunch crossing rate of 40 MHz. During the LHC Run 2 (2015–2018), the ATLAS trigger system operated successfully with excellent performance and flexibility by adapting to the various run conditions encountered and has been vital for the ATLAS Run-2 physics programme. For proton-proton running, approximately 1500 individual event selections were included in a trigger menu which specified the physics signatures and selection algorithms used for the data-taking, and the allocated event rate and bandwidth. The trigger menu must reflect the physics goals for a given data collection period, taking into account the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout, online processing farm, and offline storage. This document discusses the operation of the ATLAS trigger system during the nominal proton-proton data collection in Run 2 with examples of special data-taking runs. Aspects of software validation, evolution of the trigger selection algorithms during Run 2, monitoring of the trigger system and data quality as well as trigger configuration are presented. 2020-01-01T00:00:00Z http://hdl.handle.net/2440/129410 Title: Nonlinear guided wave mixing in pipes for detection of material nonlinearity Author: Yeung, C.; Ng, C.T. Abstract: Pipes have multiple applications in daily life and they are subjected to different types of defects. Nonlinear guided wave has attracted significant attention in detecting microstructural change at early stage of material deterioration. Extensive research using wave mixing with different wave modes has focused on plate-like structures. However, limited experimental studies have been conducted on the detection of material nonlinearity in pipes using two interacting guided waves. This study investigates nonlinear features generated due to mixing of torsional guided waves and material nonlinearity in pipes at low frequency range. The nonlinear theory of elasticity is implemented in a three-dimensional (3D) finite element (FE) method to simulate the effect of material nonlinearity on torsional guided wave mixing. The phenomenon of nonlinear features generated due to torsional guided wave mixing is investigated by 3D FE models. There is good agreement between the data obtained in the laboratory and numerical simulation results. This study demonstrates the existence of the combinational harmonic generation experimentally and provides physical insight into the phenomenon of nonlinear wave mixing. The findings of this study can further advance the damage detection techniques based on material nonlinearity in wave mixing. 2020-01-01T00:00:00Z http://hdl.handle.net/2440/129398 Title: Feature-based diversity optimization for problem instance classification Author: Gao, W.; Nallaperuma, S.; Neumann, F. Abstract: Understanding the behaviour of heuristic search methods is a challenge. This even holds for simple local search methods such as 2-OPT for the Traveling Salesperson problem. In this paper, we present a general framework that is able to construct a diverse set of instances which are hard or easy for a given search heuristic. Such a diverse set is obtained by using an evolutionary algorithm for constructing hard or easy instances which are diverse with respect to different features of the underlying problem. Examining the constructed instance sets, we show that many combinations of two or three features give a good classification of the TSP instances in terms of whether they are hard to be solved by 2-OPT. Description: OnlinePubl 2020-01-01T00:00:00Z http://hdl.handle.net/2440/129169 Title: Transcranial low-intensity pulsed ultrasound stimulation induces neuronal autophagy Author: Huang, X.; Niu, L.; Meng, L.; Lin, Z.; Zhou, W.; Liu, X.; Huang, J.; Abbott, D.; Zheng, H. Abstract: Autophagy, or cellular self-digestion, is an essential process for eliminating abnormal protein in mammalian cells. Accumulating evidence indicates that increased neuronal autophagy has a protective effect on neurodegenerative disorders. It has been reported that low-intensity pulsed ultrasound (LIPUS) can non-invasively modulate neural activity in the brain. Yet, the effect of LIPUS on neuronal autophagy is still unclear. The objective of this study was to examine whether LIPUS stimulation could induce neuronal autophagy. Primary neurons were treated by LIPUS with frequency of 0.68 MHz, pulse repetition frequency (PRF) of 500 Hz, spatial peak temporal-average intensities (ISPTA) of 70 and 165 mW/cm2. Then immunofluorescent analysis of LC3B was carried out for evaluating neuronal autophagy. Further, 0.5 MHz LIPUS was non-invasively delivered to the cortex and hippocampus of adult mice (n = 16) with PRF of 500 Hz and ISPTA of 235 mW/cm2. The LC3BII/LC3BI ratio and p62 (autophagic markers) were measured by western blot analysis. In in vitro study, the expression of LC3B in primary neurons was statistically improved after LIPUS stimulation was implemented for 4 hours (p < 0.01). With the increase of irradiation duration or acoustic intensity of LIPUS stimulation, the expression of LC3B in primary neurons was increased. Furthermore, transcranial LIPUS stimulation increased the LC3BII/LC3BI ratio (p < 0.05), and decreased the expression of p62 (p < 0.05) in the cortex and hippocampus. We concluded that LIPUS provides a safe and capable tool for activating neuronal autophagy in vitro and in vivo. Description: Early access 05 October 2020. OnlinePubl 2020-01-01T00:00:00Z