Understanding Algorithm Performance on an Oversubscribed Scheduling Application

The best performing algorithms for a particular oversubscribed scheduling application, Air Force Satellite Control Network (AFSCN) scheduling, appear to have little in common. Yet, through careful experimentation and modeling of performance in real problem instances, we can relate characteristics of the best algorithms to characteristics of the application. In particular, we find that plateaus dominate the search spaces (thus favoring algorithms that make larger changes to solutions) and that some randomization in exploration is critical to good performance (due to the lack of gradient information on the plateaus). Based on our explanations of algorithm performance, we develop a new algorithm that combines characteristics of the best performers; the new algorithms performance is better than the previous best. We show how hypothesis driven experimentation and search modeling can both explain algorithm performance and motivate the design of a new algorithm

Magnetoacoustic waves and the Kelvin-Helmholtz instability in a steady asymmetric slab

Recent observations have shown that bulk flow motions in structured solar plasmas, most evidently in coronal mass ejections (CMEs), may lead to the formation of Kelvin–Helmholtz instabilities (KHIs). Analytical models are thus essential in understanding both how the flows affect the propagation of magnetohydrodynamic (MHD) waves, and what the critical flow speed is for the formation of the KHI. We investigate both these aspects in a novel way: in a steady magnetic slab embedded in an asymmetric environment. The exterior of the slab is defined as having different equilibrium values of the background density, pressure, and temperature on either side. A steady flow and constant magnetic field are present in the slab interior. Approximate solutions to the dispersion relation are obtained analytically and classified with respect to mode and speed. General solutions and the KHI thresholds are obtained numerically. It is shown that, generally, both the KHI critical value and the cut-off speeds for magnetoacoustic waves are lowered by the external asymmetry

Closure of EU Settlement Scheme risks leaving migrant Roma behind

The closure of the UK’s EU Settlement Scheme (EUSS) poses new challenges for migrant Roma in the UK and could further increase existing inequalities, create barriers to work for Roma, and contribute to ongoing marginalisation. Roma communities would benefit from continued frontline support in order to retain their full rights to live and work in the UK

An analytical model of the Kelvin–Helmholtz instability of transverse coronal loop oscillations

Recent numerical simulations have demonstrated that transverse coronal loop oscillations are susceptible to the Kelvin–Helmholtz (KH) instability due to the counterstreaming motions at the loop boundary. We present the first analytical model of this phenomenon. The region at the loop boundary where the shearing motions are greatest is treated as a straight interface separating time-periodic counterstreaming flows. In order to consider a twisted tube, the magnetic field at one side of the interface is inclined. We show that the evolution of the displacement at the interface is governed by Mathieu's equation, and we use this equation to study the stability of the interface. We prove that the interface is always unstable and that, under certain conditions, the magnetic shear may reduce the instability growth rate. The result, that the magnetic shear cannot stabilize the interface, explains the numerically found fact that the magnetic twist does not prevent the onset of the KH instability at the boundary of an oscillating magnetic tube. We also introduce the notion of the loop σ-stability. We say that a transversally oscillating loop is σ-stable if the KH instability growth time is larger than the damping time of the kink oscillation. We show that even relatively weakly twisted loops are σ-stable

EU children in Brexit Britain: re‐negotiating belonging in nationalist times

© 2019 The Authors. International Migration © 2019 IOM This article contributes to debates on identification, home and belonging by focusing on EU children in Brexit times. The article combines attention to the emotional and affective side of integration with a focus on the effects of the discursive practices of the state on these processes. The article explores how Italian children and their parents navigate the increasingly neo-assimilationist pressures in Britain. Specifically, it looks at children's ways of accommodating their parents’ values of mobility, multilingualism and transnationalism with the revived nationalist logic now dominant. The article argues for renewed scrutiny into the role of public discourses on migrants’ experiences, which illuminate the redrawing of the boundaries between inclusion and exclusion at moments of crisis

New Complexity Trade-Offs for the (Multiple) Number Field Sieve Algorithm in Non-Prime Fields

The selection of polynomials to represent number fields crucially determines the efficiency of the Number Field Sieve (NFS) algorithm for solving the discrete logarithm in a finite field. An important recent work due to Barbulescu et al. builds upon existing works to propose two new methods for polynomial selection when the target field is a non-prime field. These methods are called the generalised Joux-Lercier (GJL) and the Conjugation methods. In this work, we propose a new method (which we denote as $\mathcal{A}$) for polynomial selection for the NFS algorithm in fields $\mathbb{F}_{Q}$, with $Q=p^n$ and $n>1$. The new method both subsumes and generalises the GJL and the Conjugation methods and provides new trade-offs for both $n$ composite and $n$ prime. Let us denote the variant of the (multiple) NFS algorithm using the polynomial selection method ``{X} by (M)NFS-{X}. Asymptotic analysis is performed for both the NFS-$\mathcal{A}$ and the MNFS-$\mathcal{A}$ algorithms. In particular, when $p=L_Q(2/3,c_p)$, for $c_p\in [3.39,20.91]$, the complexity of NFS-$\mathcal{A}$ is better than the complexities of all previous algorithms whether classical or MNFS. The MNFS-$\mathcal{A}$ algorithm provides lower complexity compared to NFS-$\mathcal{A}$ algorithm; for $c_p\in (0, 1.12] \cup [1.45,3.15]$, the complexity of MNFS-$\mathcal{A}$ is the same as that of the MNFS-Conjugation and for $c_p\notin (0, 1.12] \cup [1.45,3.15]$, the complexity of MNFS-$\mathcal{A}$ is lower than that of all previous methods

RECENT TRENDS REGARDING DISTANCE PROTECTION A REVIEW

This paper is structured in six parts and aims to present actual trends regarding distance protection. In the first part is determined the importance of the topic and the requirement of using protections. In the second part is presented the evolution of the protection and automation systems. In part three is presented the distance protection with its past and present, with its principles. In part four are given examples of how the pickup characteristics of the the distance protection have evolved. Part five presents how actual protection functions are implemented and related to the distance protection which functions are new. Part six is dedicated to present the conclusions related to this paper

Genome-wide Association Study Identifies New Loci for Resistance to Leptosphaeria maculans in Canola

Blackleg, caused by Leptosphaeria maculans, is a significant disease which affects the sustainable production of canola. This study reports a genome-wide association study based on 18,804 polymorphic SNPs to identify loci associated with qualitative and quantitative resistance to L. maculans. Genomic regions delimited with 503 significant SNP markers, that are associated with resistance evaluated using 12 single spore isolates and pathotypes from four canola stubble were identified. Several significant associations were detected at known disease resistance loci including in the vicinity of recently cloned Rlm2/LepR3 genes, and at new loci on chromosomes A01/C01, A02/C02, A03/C03, A05/C05, A06, A08, and A09. In addition, we validated statistically significant associations on A01, A07 and A10 in four genetic mapping populations, demonstrating that GWAS marker loci are indeed associated with resistance to L. maculans. One of the novel loci identified for the first time, Rlm12, conveys adult plant resistance and mapped within 13.2 kb from Arabidopsis R gene of TIR-NBS class. We showed that resistance loci are located in the vicinity of R genes of A. thaliana and B. napus on the sequenced genome of B. napus cv. Darmor-bzh. Significantly associated SNP markers provide a valuable tool to enrich germplasm for favorable alleles in order to improve the level of resistance to L. maculans in canola

Optimization of Single-Satellite Operational Schedules Towards Enhanced Communication Capacity

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97112/1/AIAA2012-4610.pd