83 research outputs found
Topology of spin meron pairs in coupled Ni/Fe/Co/Cu(001) disks
No full textThe meron is a special topological object that carries only one-half of the topological charge unit. In condensed matter physics, a spin meron corresponds to one-half of a spin skyrmion. As compared to the many fascinating topological properties of skyrmion materials, little is known of the properties of spin merons especially about their formation. It was confirmed only recently that hedgehog merons could exist in pairs with opposite helicities via a spin flux closure. However, it is unclear whether a single hedgehog meron could ever exist by pairing with another type of meron. Using element-resolved magnetic imaging measurements on epitaxial trilayer disks, we show that a spin meron with a full range of helicity, including the hedgehog meron, can be stabilized by pairing with another vortex meron with a fine tuning of the magnetic coupling between the two merons. Furthermore, the meron divergence is fully controlled by the polarity of the vortex meron, independent of the vortex helicity.National Science Foundation [DMR-1504568]; Future Materials Discovery Program through the National Research Foundation of Korea [2015M3D1A1070467]; Science Research Center Program through the National Research Foundation of Korea [2015R1A5A1009962]; Office of Science, Office of Basic Energy Sciences; US Department of Energy [DE-AC02-05CH11231]SCI(E)[email protected]
Creation and annihilation of topological meron pairs in in-plane magnetized films
No full textMerons which are topologically equivalent to one-half of skyrmions can exist only in pairs or groups in two-dimensional (2D) ferromagnetic (FM) systems. The recent discovery of meron lattice in chiral magnet Co8Zn9Mn3 raises the immediate challenging question that whether a single meron pair, which is the most fundamental topological structure in any 2D meron systems, can be created and stabilized in a continuous FM film? Utilizing winding number conservation, we develop a new method to create and stabilize a single pair of merons in a continuous Py film by local vortex imprinting from a Co disk. By observing the created meron pair directly within a magnetic field, we determine its topological structure unambiguously and explore the topological effect in its creation and annihilation processes. Our work opens a pathway towards developing and controlling topological structures in general magnetic systems without the restriction of perpendicular anisotropy and Dzyaloshinskii–Moriya interaction. © 2019, The Author(s).TRU
The Mount Meron infrasound array: An infrasound array without a noise reduction system
No full textMeasurements of seismo-acoustic events by collocated seismic and infrasound arrays allow for studying the two wavefields that were produced by the same event. However, some of the scientific and technical constraints on the building of the two technologies are different and may be contradicting. For the case of a new station, an optimal design that will satisfy the constraints of the two technologies can be found. However, in the case of upgrading an existing array by adding the complementing technology, the situation is different. The site location, the array configuration and physical constraints are fixed and may not be optimal for the complementing technology, which may lead to rejection of the upgrade. The International Monitoring System (IMS) for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) includes 37 seismic arrays and 51 infrasound arrays. Although the CTBT verification regime is fixed in the treaty, an upgrade of the existing arrays by adding more technologies is possible. The Mount Meron seismic array (MMAI), which is part of the IMS, is composed of 16 sites. Microbarometers were installed at five MMAI sites to form the Mount Meron infrasound array. Due to regulation and physical constraints, it was not possible to relocate the sites nor to install analogue noise reduction filters (i.e. a pipe array). In this study, it is demonstrated that the installation of the MMAI infrasound array is beneficial despite the non-optimal conditions. It is shown that the noise levels of the individual array sites are between the high and median global noise levels. However, we claim that the more indicative measures are the noise levels of the beams of interest, as demonstrated by analysing the microbaroms originated from the Mediterranean Sea. Moreover, the ability to detect events relevant to the CTBT is demonstrated by analysing man-made events during 2011 from the Libya region
Zero-field skyrmion, meron, and vortex crystals in centrosymmetric hexagonal magnets
No full textWe investigate the interaction conditions to stabilize topological spin textures in centrosymmetric magnets without an external magnetic field. By performing the simulated annealing for an effective spin model with the momentum-resolved interaction on a two-dimensional triangular lattice, we find that the competing interactions between the finite -q channel and the uniform (q = 0) channel lead to a zero-field skyrmion crystal with the skyrmion number of +/- 1. Moreover, we obtain a variety of topological spin textures, such as a meron crystal, vortex crystal, and other multiple -Q states with and without a scalar chirality. We especially show that the bond-dependent anisotropic exchange interaction originating from the relativistic spin-orbit coupling plays an important role in inducing such topological spin textures, while the single-ion anisotropy does not
Process-based Modelling of Late Quaternary Morphology and Stratigraphy of the Northern Adriatic Basin
No full textThe thesis is devoted to calibration of a process-based numerical model and its application to simulation of the Late Quaternary history and stratigraphy of the Northern Adriatic Sea. Tests aimed at assessing the sensitivity of the model to initial and boundary conditions were conducted, based on geomorphologic and stratigraphic data culled from literature. Based on these tests, wave-generated erosion and diffusion coupled with current-induced removal and transportation algorithms were adopted to simulate intensification of the Western Adriatic Coastal Current (WACC) by the Bora Wind during the Late Holocene. Different scenarios have been assessed to examine the model’s ability to reproduce the stratigraphic architecture of the Adriatic Basin. Model results for the prodelta of the Po River at the north-western low-gradient shelf are represented by a continuous subaqueous delta, which forms an elongated coast-hugging deposit. The central Apennine part of the western shelf, which has a comparatively steep gradient, is characterized by the presence of fluvio-deltaic lobes deposited by the Apennine Rivers. The sediment budget has been calculated based on the isopach maps of modelled stratigraphy. A total sediment mass of abut 800 Gt was supplied to the basin over the time span corresponding to TST and HST (~19 kyr). Volumetric estimates indicate that roughly 87% of the supplied sediments have been preserved on the shelf. This suggests an export of ~13% to the MAD and to the southern part of the basin. The result is compatible with literature, where 10% of the sediment has been reported to move south of the Gargano promontory. Over the past 5.5 kyr, 256 Gt of sediment has been preserved on the shelf and is stored in the HST, corresponding to an average rate of deposition about 46 Mt yr-1, which is ~4 Mt yr-1 more than study reports. The rate of fluvial sediment supply (52 Mt yr-1) during formation of the HST suggests an export of ~6 Mt yr-1 to deeper parts of the basin below the effective hydrodynamic base.GeotechnologyCivil Engineering and Geoscience
Exploring Distributive Justice In Many-Objective Optimization: A Comparative Analysis of A Priori and A Posteriori Approaches to Implementing Distributive Justice Principles
No full textAddressing the global challenge of water scarcity, particularly in the context of Sustainable Development Goal 6, underscores the critical need for effective water resource management. Central to this management is the control of dams in river basins, which poses complex decision-making challenges often labeled as wicked problems. Many-Objective Optimization, a powerful tool in modeling water systems, grapples with conflicting objectives, and the complexity heightens when integrating Distributive Justice principles. Distributive Justice, aiming to equitably distribute resources, is crucial in the context of water distribution for reservoir management. While current modeling approaches predominantly apply Distributive Justice principles A Posteriori, this study focuses on their A Priori incorporation, evaluating their impact on trade-offs and decision-making processes within the framework of Many-Objective Optimization.The investigation delves into Utilitarianism, Egalitarianism, and Prioritarianism, representing varied Distributive Justice perspectives. These frameworks are translated into mathematical models to provide insights into how societal values influence water resource allocation. The research centers on managing contentious shared water resources within the Eastern Nile River Basin. A comparative analysis between A Priori and A Posteriori integration of Distributive justice principles reveals distinct Pareto-optimal trade-offs. The findings underscore significant differences between a priori and a posteriori approaches, with Utilitarian integration enhancing overall system performance, egalitarian integration diversifying solutions, and prioritarian integration yielding sharper trade-offs. This study contributes valuable insights to the ethical considerations in many-objective optimization. It also offers guidance for policymakers and water resource managers by providing clear terminology to discuss and evaluate different approaches that are fitting within the policymaker's scope.Engineering and Policy Analysi
Technology and Customers’ Experiences in Fashion Physical Stores: The Case of Sweden
No full textTitle: Technology and Consumers’ Experiences in Fashion Physical Stores: The Case of Sweden Level: Master Thesis in Business Administration Author: Meron Kebede Abebaw; Willard Kingstone Matukuta Supervisor: Agneta Sundström, PhD Examiner: Maria Fregidou-Malama, PhD Date: May, 2018 Aim: The aim of this study is to analyze whether in-store digital technology in fashion retailers are used to change the customers’ shopping experience and behavior. Method: This study chooses qualitative research and used both primary and secondary data collection as method. Results and conclusions: This study have reached to conclude that: with the current advances in technology, physical stores can use in-store technology to give customers a new experience; physical stores perceive that using in-store digital technology will change customers shopping experience. Also, marketing mix inputs and technology affect customers’ behavior. Suggestions for future research: For future research, how smart fitting rooms may influence the customer experience in the physical store will be important to study. Researchers can also consider understanding customer responses to in-store technology. Finally, a customer’s perspective to both suggestions should improve the knowledge on whether digital solutions are preferred in in-store shopping or not. Contributions of the thesis: This thesis contributes to the current state of theories on in-store technology by showing atmosphere has effect on customers’ experiences and behavior in addition to the marketing mix. On the managerial perspective, analyzing the installation of this technology will enable to identify its effect on customers’ experiences and behavior. In addition, on the societal perspective, the behavior of customers will help in motivating younger generation to utilize this in-store technology
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Human rights law-making in the United Nations:a critique of instruments and process /
No full textThe author examines the methods employed by the UN in adopting human rights instruments, and concludes that the present system of law-making is inadequate
Author Correction: Africa needs context-relevant evidence to shape its clean energy future
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