Algebraic Attack on the Alternating Step(r,s)Generator

The Alternating Step(r,s) Generator, ASG(r,s), is a clock-controlled sequence generator which is recently proposed by A. Kanso. It consists of three registers of length l, m and n bits. The first register controls the clocking of the two others. The two other registers are clocked r times (or not clocked) (resp. s times or not clocked) depending on the clock-control bit in the first register. The special case r=s=1 is the original and well known Alternating Step Generator. Kanso claims there is no efficient attack against the ASG(r,s) since r and s are kept secret. In this paper, we present an Alternating Step Generator, ASG, model for the ASG(r,s) and also we present a new and efficient algebraic attack on ASG(r,s) using 3(m+n) bits of the output sequence to find the secret key with O((m^2+n^2)*2^{l+1}+ (2^{m-1})*m^3 + (2^{n-1})*n^3) computational complexity. We show that this system is no more secure than the original ASG, in contrast to the claim of the ASG(r,s)'s constructor.Comment: 5 pages, 2 figures, 2 tables, 2010 IEEE International Symposium on Information Theory (ISIT2010),June 13-18, 2010, Austin, Texa

Predication at the interface

We try to show that predication plays a greater role in syntax than commonly assumed. Specifically, we wil argue that predication to a large extent determines both the phrase structure of clauses and trigger syntactic processes that take place in clauses. If we are on the right path, this implies that syntax is basically semantically driven, given that predication is semantically construed

Weld sequence optimization: the use of surrogate models for solving sequential combinatorial problems

The solution of combinatorial optimization problems usually involves the consideration of many possible design configurations. This often makes such approaches computationally expensive, especially when dealing with complex finite element models. Here a surrogate model is proposed that can be used to reduce substantially the computational expense of sequential combinatorial finite element problems. The model is illustrated by application to a weld path planning problem

Does variation in GP practice matter for the length of sick leave? A multilevel analysis based on Norwegian GP—patient data

In many countries, the social insurance system is under pressure from an ageing population. An increasing number of people are on sickness benefits and disability pensions in Norway. The general practitioner (GP) is responsible for assessing work capacity and issuing certificates for sick leave based on an evaluation of the patient. Although many studies have analysed certified sickness absence and predictive factors, very few studies focus on the length of sick leave and no studies assess its variation between patients, GPs or geographical areas within a multilevel framework. This study aims to analyse factors explaining the variation in the length of certified sick leave and to disentangle patients, GPs and municipality sources of variation in sickness durations for the whole population of Norwegian workers in 2003. This study uses a unique Norwegian administrative data set that merges data from different sources. The study uses amatched patient—GP data set, and employs amultilevel random intercept model to separate out patient, GP and municipality-level explained and unexplained parts of the variation in the certified sickness durations. We find that all observed patient and GP characteristics are significantly associated with the length of sick leaves (LSL). However, 98% of the variation in the LSL is attributed to patient factors rather than influenced by variations in GP practice or differences in municipality-level characteristics. Medical diagnosis is an important observed factor explaining certified sickness durations. Low variations across GPs may imply that the gatekeeping role of Norwegian GPs is weak compared with their advocate role.general practitioners (GPs); length of sick leave; multilevel regression models; matched GP—patient data

Strain controlled oxygen vacancy formation and ordering in CaMnO3_3

We use first-principles calculations to investigate the stability of bi-axially strained \textit{Pnma} perovskite CaMnO$_3$ towards the formation of oxygen vacancies. Our motivation is provided by promising indications that novel material properties can be engineered by application of strain through coherent heteroepitaxy in thin films. While it is usually assumed that such epitaxial strain is accommodated primarily by changes in intrinsic lattice constants, point defect formation is also a likely strain relaxation mechanism. This is particularly true at the large strain magnitudes ($>$4%) which first-principles calculations often suggest are required to induce new functionalities. We find a strong dependence of oxygen vacancy defect formation energy on strain, with tensile strain lowering the formation energy consistent with the increasing molar volume with increasing oxygen deficiency. In addition, we find that strain differentiates the formation energy for different lattice sites, suggesting its use as a route to engineering vacancy ordering in epitaxial thin films.Comment: 7 pages, 7 figure

Teachers' Sickness Absence in Primary Schools: A Panel Data Multilevel Analysis

This paper uses longitudinal employer–employee data and multilevel models to examine both observed and unobserved variation of the probability and length of certified and self-certified sickness absence for Norwegian primary school teachers. We argue that self-certified absences are particularly prone to moral hazard. We find that most of the observed teacher, school and municipality characteristics are significantly associated with the probability and the length of sickness absence. However, most of the unexplained variation is attributed to teacher factors rather than influenced by variation at the school or municipality levels. Teacher characteristics that may be associated with less attachment to the workplace increase the probability of self-certified absences. Moreover, the unexplained variation in schools and at municipality level is higher for self-certified than for certified sickness absence. There may be some scope for reducing self-certified absence by improving work conditions or changing administrative practices, but our main policy conclusion is that to reduce sickness absence, the main focus must be on individual health and the incentives to report sick.sickness absence; employer-employee data; multilevel analysis

The N-Effect More Competitors, Less Competition

This article introduces the N-effect—the discovery that increasing the number of competitors (N) can decrease competitive motivation. Studies 1a and 1b found evidence that average test scores (e.g., SAT scores) fall as the average number of test takers at test-taking venues increases. Study 2 found that individuals trying to finish an easy quiz among the top 20% in terms of speed finished significantly faster if they believed they were competing in a pool of 10 rather than 100 other people. Study 3 showed that the N-effect is strong among individuals high in social-comparison orientation and weak among those low in social-comparison orientation. Study 4 directly linked the N-effect to social comparison, ruling out ratio bias as an explanation of our results and finding that social comparison becomes less important as N increases. Finally, Study 5 found that the N-effect is mediated by social comparison. Limitations, future directions, and implications are discussed