Evolutionary algorithms in dynamic environments

The file attached to this record is the author's final peer reviewed version.Evolutionary algorithms (EAs) are widely and often used for solving stationary optimization problems where the fitness landscape or objective function does not change during the course of computation. However, the environments of real world optimization problems may fluctuate or change sharply. If the optimization problem is dynamic, the goal is no longer to find the extrema, but to track their progression through the search space as closely as possible. All kinds of approaches that have been proposed to make EAs suitable for the dynamic environments are surveyed, such as increasing diversity, maintaining diversity, memory based approaches, multi-population approaches and so on

Geometrical effects of a subducted seamount on stopping megathrust ruptures

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 2011–2016, doi:10.1002/grl.50509.We have numerically simulated dynamic ruptures along a “slip-weakening” megathrust fault with a subducted seamount of realistic geometry, demonstrating that seamounts can act as a barrier to earthquake ruptures. Such barrier effect is calculated to be stronger for increased seamount normal stress relative to the ambient level, for larger seamount height-to-width ratio, and for shorter seamount-to-nucleation distance. As the seamount height increases from 0 to 40% of its basal width, the required increase in the effective normal stress on the seamount to stop ruptures drops by as much as ~20%. We further demonstrate that when a seamount is subducted adjacent to the earthquake nucleation zone, coseismic ruptures can be stopped even if the seamount has a lower effective normal stress than the ambient level. These results indicate that subducted seamounts may stop earthquake ruptures for a wide range of seamount normal stress conditions, including the case of the thrust fault being lubricated by seamount-top fluid-rich sediments, as suggested from observations in the Japan and Sunda Trenches.This work was supported by NSF grant EAR-1015221 and WHOI Deep Ocean Exploration Institute awards 27071150 and 25051162

Seismic structures of the Calico fault zone inferred from local earthquake travel time modelling

Author Posting. © The Authors, 2011. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 186 (2011): 760-770, doi:10.1111/j.1365-246X.2011.05055.x.We analysed high-frequency body waves of local earthquakes to image the damage zone of the Calico fault in the eastern California shear zone. We used generalized ray theory and finite difference methods to compute synthetic seismograms for a low-velocity fault zone (FZ) to model the direct and FZ-reflected P and S traveltimes of local earthquakes recorded by a temporary array across the fault. The low velocity zone boundaries were determined by apparent traveltime delays across the fault. The velocity contrast between the fault zone and host rock was constrained by the traveltime delays of P and S waves and differential traveltimes between the direct and FZ-reflected waves. The dip and depth extent of the low velocity zone were constrained by a systematic analysis of direct P traveltimes of events on both sides of the fault. We found that the Calico fault has a ∼1.3-km-wide low velocity zone in which the P- and S-wave velocity decreased 40 and 50 per cent, respectively, with respect to the host rock. The low velocity zone dips 70° northeast and extends 3 km in depth.This work is supported by the National Science Foundation under Grant No. EAR-0609969 and EAR-0838195

A memetic particle swarm optimisation algorithm for dynamic multi-modal optimisation problems

Copyright @ 2011 Taylor & Francis.Many real-world optimisation problems are both dynamic and multi-modal, which require an optimisation algorithm not only to find as many optima under a specific environment as possible, but also to track their moving trajectory over dynamic environments. To address this requirement, this article investigates a memetic computing approach based on particle swarm optimisation for dynamic multi-modal optimisation problems (DMMOPs). Within the framework of the proposed algorithm, a new speciation method is employed to locate and track multiple peaks and an adaptive local search method is also hybridised to accelerate the exploitation of species generated by the speciation method. In addition, a memory-based re-initialisation scheme is introduced into the proposed algorithm in order to further enhance its performance in dynamic multi-modal environments. Based on the moving peaks benchmark problems, experiments are carried out to investigate the performance of the proposed algorithm in comparison with several state-of-the-art algorithms taken from the literature. The experimental results show the efficiency of the proposed algorithm for DMMOPs.This work was supported by the Key Program of National Natural Science Foundation (NNSF) of China under Grant no. 70931001, the Funds for Creative Research Groups of China under Grant no. 71021061, the National Natural Science Foundation (NNSF) of China under Grant 71001018, Grant no. 61004121 and Grant no. 70801012 and the Fundamental Research Funds for the Central Universities Grant no. N090404020, the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant no. EP/E060722/01 and Grant EP/E060722/02, and the Hong Kong Polytechnic University under Grant G-YH60

Effects of Chronic Mild Stress on the Development of Atherosclerosis and Expression of Toll-Like Receptor 4 Signaling Pathway in Adolescent Apolipoprotein E Knockout Mice

Here, we investigated the effect of chronic mild stress (CMS) on the development of atherosclerosis as well as the expression of Toll-like receptors (TLRs) signaling pathway in adolescent apolipoprotein E knockout (apoE-/-) mice. Mice were subjected to daily CMS for 0, 4, and 12 weeks, respectively. To identify the expression of Toll-like receptor 4 signaling pathway in adolescent apolipoprotein E knockout mice subjected to CMS, we compared gene expression in aortas of stressed and unstressed mice using TLRs signaling pathway real-time PCR microarrays consisting of 87 genes. We found that atherosclerosis lesions both in aortic tress and sinuses of CMS mice were significantly increased linearly in response to duration of CMS exposure. Among 87 genes analyzed, 15 genes were upregulated in stressed mice, especially TLR4, myeloid differentiation factor 88 (MyD88), and IL-1β, and 28 genes were downregulated compared with nonstressed mice. CMS mice demonstrated markedly increased aortic atherosclerosis that were associated with significant increases in levels of expression of TLR4, MyD88, nuclear factor κB (NF-κB), MCP-1, IL-1β, TNF-α, and sICAM-1. Taken together, our results suggest an important role for TLR4 signaling pathway in atherosclerosis in a CMS mouse model

Iterative learning fault-tolerant control for differential time-delay batch processes in finite frequency domains

This paper develops a fault-tolerant iterative learning control law for a~class of~linear time-delay differential batch processes with actuator faults using the repetitive process setting. Once the dynamics are expressed in this setting, stability analysis and control law design makes use of the generalized Kalman-Yakubovich-Popov (KYP) lemma in the form of the corresponding linear matrix inequalities (LMIs). In particular, sufficient conditions for the existence of a fault-tolerant control law are developed together with design algorithms for the associated matrices. Under the action of this control law the ILC dynamics have a monotonicity property in terms of an error sequence formed from the difference between the supplied reference trajectory and the outputs produced. An extension to robust control against structured time-varying uncertainties is also developed. Finally, a simulation based case study on the model of a~two-stage chemical reactor with delayed recycle is given to demonstrate the feasibility and effectiveness of the new designs

Mechanism of progressive broad deformation from oceanic transform valley to off-transform faulting and rifting

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zhang, F., Lin, J., Zhou, Z., Yang, H., & Morgan, J. P. Mechanism of progressive broad deformation from oceanic transform valley to off-transform faulting and rifting. Innovation, 3(1), (2022): 100193, https://doi.org/10.1016/j.xinn.2021.100193.Oceanic transform faults (TFs) are commonly viewed as single, narrow strike-slip seismic faults that offset two mid-ocean ridge segments. However, broad zones of complex deformation are ubiquitous at TFs. Here, we propose a new conceptual model for the progressive deformation within broad zones at oceanic TFs through detailed morphological, seismic, and stress analyses. We argue that, under across-transform extension due to a change in plate motion, plate deformation occurs first along high-angle transtensional faults (TTFs) within the transform valleys. Off-transform normal faults (ONFs) form when across-transform deviatoric extensional stresses exceed the yield strength of the adjacent oceanic lithosphere. With further extension, these normal faults can develop into off-transform rift zones (ORZs), some of which can further develop into transform plate boundaries. We illustrate that such progressive complex deformation is an inherent feature of oceanic TFs. The new conceptual model provides a unifying theory to explain the observed broad deformation at global transform systems.We benefited from discussions with Drs. Tao Zhang, Huihui Weng, Yen Joe Tan, the SCSIO Deep Ocean Geodynamics Group, the CUHK Seismology Group, and the participants of the InterRidge transform fault workshop in France, 2018. This work was supported by the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0205), NSFC grants (41976064, 41890813, 41976066, 91628301, and 91858207), CAS grants (Y4SL021001, QYZDY-SSW-DQC005, 133244KYSB20180029, 131551KYSB20200021, and ISEE2021PY03), National Key R&D Program of China grants (2018YFC0309800 and 2018YFC0310105), the Guangdong Basic and Applied Basic Research Foundation (2021A1515012227), and Hong Kong Research Grant Council grants (14304820 and 14306119)

Fault-Plane Determination of the 18 April 2008 Mount Carmel, Illinois, Earthquake by Detecting and Relocating Aftershocks

We developed a sliding-window cross-correlation (SCC) detection technique and applied the technique to continuous waveforms recorded by the Cooperative New Madrid Seismic Network stations following the 18 April 2008 Illinois earthquake. The technique detected more than 120 aftershocks down to M_L 1.0 in the 2 week time window following the mainshock, which is three times more than the number of aftershocks reported by the seismic network. Most aftershocks happened within 24 hrs of the mainshock. We then relocated all events by the double-difference relocation algorithm. Accurate P- and S-wave differential arrival times between events were obtained by waveform cross correlation. After relocation, we used the L1 norm to fit all located events by a plane to determine the mainshock fault plane. The best-fit plane has a strike of 292°±11° and dips 81°±7° to the northeast. This plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks. By combining the aftershock locations and focal mechanism solutions, we conclude that the 18 April earthquake occurred on a nearly vertical left-lateral strike-slip fault orienting in the west-northwest–east-southeast direction. The fault coincides with the proposed left-stepping Divide accommodation zone in the La Salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the Midcontinent

Output Information Based Fault-Tolerant Iterative Learning Control for Dual-Rate Sampling Process with Disturbances and Output Delay

For a class of single-input single-output (SISO) dual-rate sampling processes with disturbances and output delay, this paper presents a robust fault-tolerant iterative learning control algorithm based on output information. Firstly, the dual-rate sampling process with output delay is transformed into discrete system in state-space model form with slow sampling rate without time delay by using lifting technology; then output information based fault-tolerant iterative learning control scheme is designed and the control process is turned into an equivalent two-dimensional (2D) repetitive process. Moreover, based on the repetitive process stability theory, the sufficient conditions for the stability of system and the design method of robust controller are given in terms of linear matrix inequalities (LMIs) technique. Finally, the flow control simulations of two flow tanks in series demonstrate the feasibility and effectiveness of the proposed method

Along-strike variation in slab geometry at the southern Mariana subduction zone revealed by seismicity through ocean bottom seismic experiments

Author Posting. © The Authors, 2019. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 218(3), (2019): 2122-2135, doi: 10.1093/gji/ggz272.We have conducted the first passive Ocean Bottom Seismograph (OBS) experiment near the Challenger Deep at the southernmost Mariana subduction zone by deploying and recovering an array of 6 broad-band OBSs during December 2016–June 2017. The obtained passive-source seismic records provide the first-ever near-field seismic observations in the southernmost Mariana subduction zone. We first correct clock errors of the OBS recordings based on both teleseismic waveforms and ambient noise cross-correlation. We then perform matched filter earthquake detection using 53 template events in the catalogue of the US Geological Survey and find >7000 local earthquakes during the 6-month OBS deployment period. Results of the two independent approaches show that the maximum clock drifting was ∼2 s on one instrument (OBS PA01), while the rest of OBS waveforms had negligible time drifting. After timing correction, we locate the detected earthquakes using a newly refined local velocity model that was derived from a companion active source experiment in the same region. In total, 2004 earthquakes are located with relatively high resolution. Furthermore, we calibrate the magnitudes of the detected earthquakes by measuring the relative amplitudes to their nearest relocated templates on all OBSs and acquire a high-resolution local earthquake catalogue. The magnitudes of earthquakes in our new catalogue range from 1.1 to 5.6. The earthquakes span over the Southwest Mariana rift, the megathrust interface, forearc and outer-rise regions. While most earthquakes are shallow, depths of the slab earthquakes increase from ∼100 to ∼240 km from west to east towards Guam. We also delineate the subducting interface from seismicity distribution and find an increasing trend in dip angles from west to east. The observed along-strike variation in slab dip angles and its downdip extents provide new constraints on geodynamic processes of the southernmost Mariana subduction zone.We express our appreciation to the science parties and crew members of the R/V Shiyan 3 for deployment and collection of the OBS instruments during the Mariana expeditions. This study is supported by the Hong Kong Research Grant Council Grants (No. 14313816), Faculty of Science at CUHK, Chinese Academy of Sciences (No. Y4SL021001, QYZDY-SSW-DQC005, 133244KYSB20180029), the National Natural Science Foundation of China (No. 41890813, 91628301, 41676042, U1701641, 41576041, 91858207 and U1606401), the National Key R&D Program of China (2018YFC0309800 and 2018YFC0310100). Generic Mapping Tools (Wessel & Smith 1991) and PSSAC (developed by Prof Lupei Zhu) are used for data analysis and figure preparation in this study. Constructive comments from Dr Lidong Bie and two anonymous reviewers are helpful in improving the manuscript