The role of domain walls on the vortex creep dynamics in unconventional superconducors

We investigate the influence of domain walls on the vortex dynamics in superconductors with multi-component order parameters. We show that, due to their complex structure domain walls can carry vortices with fractional flux quanta. The decay of conventional vortices into fractional ones on domain walls is examined. This decay presents an extraordinarily strong pinning mechanism for vortices and turns domain walls occupied with pinned fractional vortices into efficient barriers for the vortex motion. Therefore, domain walls can act as fences for the flux flow, preventing the decay of the remnant magnetic flux enclosed by them. Furthermore, the consequences of this property of domain walls on the vortex dynamics are discussed in connection with observed noise in the hysteresis cycle, using the Bean model of the critical vortex state. Based on this picture experimental data in the unconventional superconductors UPt$_3$, U$_{1-x}$Th$_x$Be$_{13}$ and Sr$_2$RuO$_4$ are interpreted.Comment: 18 pages, 9 figures, to appear in Progress of Theoretical Physic

Equilibration of Quantum hall edges in symmetry broken bilayer graphene

Equilibration of quantum Hall edges is studied in a high quality dual gated bilayer graphene device in both unipolar and bipolar regime when all the degeneracies of the zero energy Landau level are completely lifted. We find that in the unipolar regime when the filling factor under the top gate region is higher than the back gate filling factor, the equilibration is partial based on their spin polarization. However, the complete mixing of the edge states is observed in the bipolar regime irrespective of their spin configurations due to the Landau level collapsing at the sharp pn junction in our thin hBN (~ 15 nm) encapsulated device, in consistent with the existing theory

Equilibration of quantum hall edge states and its conductance fluctuations in graphene p-n junctions

We report an observation of conductance fuctuations (CFs) in the bipolar regime of quantum hall (QH) plateaus in graphene (p-n-p/n-p-n) devices. The CFs in the bipolar regime are shown to decrease with increasing bias and temperature. At high temperature (above 7 K) the CFs vanishes completely and the flat quantized plateaus are recovered in the bipolar regime. The values of QH plateaus are in theoretical agreement based on full equilibration of chiral channels at the p-n junction. The amplitude of CFs for different filling factors follows a trend predicted by the random matrix theory. Although, there are mismatch in the values of CFs between the experiment and theory but at higher filling factors the experimental values become closer to the theoretical prediction. The suppression of CFs and its dependence has been understood in terms of time dependent disorders present at the p-n junctions

An exceptional set estimate for restricted projections to lines in R3\mathbb{R}^3

Let $\gamma:[0,1]\rightarrow \mathbb{S}^{2}$ be a non-degenerate curve in $\mathbb{R}^3$, that is to say, $\det\big(\gamma(\theta),\gamma'(\theta),\gamma''(\theta)\big)\neq 0$. For each $\theta\in[0,1]$, let $l_\theta=\{t\gamma(\theta):t\in\mathbb{R}\}$ and $\rho_\theta:\mathbb{R}^3\rightarrow l_\theta$ be the orthogonal projections. We prove an exceptional set estimate. For any Borel set $A\subset\mathbb{R}^3$ and $0\le s\le 1$, define $E_s(A):=\{\theta\in[0,1]: \text{dim}(\rho_\theta(A))<s\}$. We have $\text{dim}(E_s(A))\le 1+\frac{s-\text{dim}(A)}{2}$.Comment: 11 pages. arXiv admin note: substantial text overlap with arXiv:2207.1384

Floor vibration serviceability in a multistory factory building

ArticleExperimental and analytical modal analysis and in-operation vibration measurements were performed on the massive concrete structural floors of several structurally connected ‘units’ of a six-level, multitenant industrial complex with total floor usable area exceeding 0.1 km2. The aim of the systematic study was to characterize vibration sources and factors that affect vibration serviceability, which is a major concern when changing usage patterns lead to conflicting requirements for vibration generation and tolerance for different types of industrial/ commercial user. This was a rare investigation aiming to provide information on specific performance and relevant technologies for occupancy decisions by tenants and building management of similar structures. Floors evaluated were within different types of industrial singleoccupant unit stacked up to six levels and having multibay floors with spans up to 12 m with first vibration mode frequencies greater than 8 Hz. These “high-frequency floors” display typical transient response behavior to footfalls, with response levels controlled by modal mass. Units were studied in typical operational conditions including warehousing, instrument assembly and testing, light electronic/mechanical manufacturing, and machining. Vibration sources included internal and external vehicles, human footfalls, and machinery. The study showed the most onerous form of loading to be forklift trucks and that higher level floors of the same type were least serviceable. Experimental modal analysis showed a surprising range of modal properties for nominally identical floors of the same type and the relevance to performance of modal mass

Individual Fired Brick Domestication in Nigeria

Individual fired brick domestication is not widely practiced; yet the fired brick has played and will continue to play an immense role in the global built environment. Its pivotal task of creating and sustaining architectural structures is ancient and has permeated through to contemporary times courtesy of clay's colossal vitality. Clay exploration and exploitation are perhaps most apparent in fired brick production, particularly in first-world countries with a diverse range of clayware such as bricks and tiles. This development has not been fully maximized in Nigeria as a result of the small number of refractory plants whose total production capacity is beneath the nation's building requirements. This scenario makes fired brick procurement costly and limits its accessibility; consequently, it promotes socio-built inequality among viable fired brick prospectors. In view of the aforementioned, this paper advocates individual fired brick domestication in Nigeria's rural and suburban settlements, providing concise practical details, from materials identification and mould fabrication to brick production. When fully harnessed, this is hoped to create jobs, alleviate the country's fired brick deficit, boost individual economic standing, communal economies and ultimately the national economy. Possibly it could serve as a template in similar settings around the world