Simple permutations poset

This article studies the poset of simple permutations with respect to the pattern involvement. We specify results on critically indecomposable posets obtained by Schmerl and Trotter to simple permutations and prove that if $\sigma, \pi$ are two simple permutations such that $\pi < \sigma$ then there exists a chain of simple permutations $\sigma^{(0)} = \sigma, \sigma^{(1)}, ..., \sigma^{(k)}=\pi$ such that $|\sigma^{(i)}| - |\sigma^{(i+1)}| = 1$ - or 2 when permutations are exceptional- and $\sigma^{(i+1)} < \sigma^{(i)}$. This characterization induces an algorithm polynomial in the size of the output to compute the simple permutations in a wreath-closed permutation class.Comment: 15 page

Longest Common Separable Pattern between Permutations

In this article, we study the problem of finding the longest common separable pattern between several permutations. We give a polynomial-time algorithm when the number of input permutations is fixed and show that the problem is NP-hard for an arbitrary number of input permutations even if these permutations are separable. On the other hand, we show that the NP-hard problem of finding the longest common pattern between two permutations cannot be approximated better than within a ratio of $sqrt{Opt}$ (where $Opt$ is the size of an optimal solution) when taking common patterns belonging to pattern-avoiding classes of permutations.Comment: 15 page

Susceptibility of irradiated steels to hydrogen embrittlement

Investigation determined whether irradiated pressure-vessel steels 4340 and 212-B are susceptible to hydrogen embrittlement and to catastrophic failure. Hydrogen-charging conditions which completely embrittled 4340 steel had negligible effect on 212-B steel in tensile and delayed-failure tests

Deciding the finiteness of the number of simple permutations contained in a wreath-closed class is polynomial

We present an algorithm running in time O(n ln n) which decides if a wreath-closed permutation class Av(B) given by its finite basis B contains a finite number of simple permutations. The method we use is based on an article of Brignall, Ruskuc and Vatter which presents a decision procedure (of high complexity) for solving this question, without the assumption that Av(B) is wreath-closed. Using combinatorial, algorithmic and language theoretic arguments together with one of our previous results on pin-permutations, we are able to transform the problem into a co-finiteness problem in a complete deterministic automaton

Average-case analysis of perfect sorting by reversals (Journal Version)

Perfect sorting by reversals, a problem originating in computational genomics, is the process of sorting a signed permutation to either the identity or to the reversed identity permutation, by a sequence of reversals that do not break any common interval. B\'erard et al. (2007) make use of strong interval trees to describe an algorithm for sorting signed permutations by reversals. Combinatorial properties of this family of trees are essential to the algorithm analysis. Here, we use the expected value of certain tree parameters to prove that the average run-time of the algorithm is at worst, polynomial, and additionally, for sufficiently long permutations, the sorting algorithm runs in polynomial time with probability one. Furthermore, our analysis of the subclass of commuting scenarios yields precise results on the average length of a reversal, and the average number of reversals.Comment: A preliminary version of this work appeared in the proceedings of Combinatorial Pattern Matching (CPM) 2009. See arXiv:0901.2847; Discrete Mathematics, Algorithms and Applications, vol. 3(3), 201

2-stack pushall sortable permutations

In the 60's, Knuth introduced stack-sorting and serial compositions of stacks. In particular, one significant question arise out of the work of Knuth: how to decide efficiently if a given permutation is sortable with 2 stacks in series? Whether this problem is polynomial or NP-complete is still unanswered yet. In this article we introduce 2-stack pushall permutations which form a subclass of 2-stack sortable permutations and show that these two classes are closely related. Moreover, we give an optimal O(n^2) algorithm to decide if a given permutation of size n is 2-stack pushall sortable and describe all its sortings. This result is a step to the solve the general 2-stack sorting problem in polynomial time.Comment: 41 page

Combinatorial specification of permutation classes

This article presents a methodology that automatically derives a combinatorial specification for the permutation class C = Av(B), given its basis B of excluded patterns and the set of simple permutations in C, when these sets are both finite. This is achieved considering both pattern avoidance and pattern containment constraints in permutations.The obtained specification yields a system of equations satisfied by the generating function of C, this system being always positiveand algebraic. It also yields a uniform random sampler of permutations in C. The method presentedis fully algorithmic

The Effects of California’s Paid Family Leave Program on Mothers’ Leave-Taking and Subsequent Labor Market Outcomes

This analysis uses March Current Population Survey data from 1999-2010 and a differences-in-differences approach to examine how California’s first in the nation paid family leave (PFL) program affected leave-taking by mothers following childbirth, as well as subsequent labor market outcomes. We obtain robust evidence that the California program more than doubled the overall use of maternity leave, increasing it from around three to six or seven weeks for the typical new mother – with particularly large growth for less advantaged groups. We also provide suggestive evidence that PFL increased the usual weekly work hours of employed mothers of one-to-three year-old children by 6 to 9% and that their wage incomes may have risen by a similar amount.

PENGARUH PROFITABILITAS, LIKUIDITAS DAN RISIKO BISNIS TERHADAP STRUKTUR MODAL ( Studi Pada Perusahaan Sektor Pertambangan Batubara Yang Terdaftar Di BEI Tahun 2013-2017)

Perusahaan sektor pertambangan batubara merupakan salah satu sektor ekonomi yang penting di Indonesia, karena memiliki kontribusi ekspor yang cukup besar. Hal ini tentunya membuat investor tertarik untuk berinvestasi pada perusaahaan pertambangan batubara. Penelitian ini bertujuan untuk menguji pengaruh profitabilitas, likuiditas dan risiko bisnis terhadap struktur modal melalui laporan keuangan tahunan yang disusun oleh perusaahaan pertambangan batubara yang terdaftar di Bursa Efek Indonesia (BEI) selama tahun 2013 sampai tahun 2017. Populasi yang digunakan dalam penelitian ini sebanyak 22 perusahaan sektor pertambangan batubara. Teknik pengambilan sampel menggunakan metode purposive sampling sehingga didapatkan 7 sampel perusahaan. Jenis penelitian ini merupakan penelitian kuantitatif, dengan menggunakan metode analisis regresi linier berganda. Hasil penelitian uji kelayakan model menunjukkan bahwa profitabilitas, likuiditas, dan risiko bisnis secara simultan berpengaruh signifikan terhadap struktur modal. Berdasarkan hasil uji hipotesis menunjukan bahwa profitabilitas berpengaruh negatif tidak signifikan dan risiko bisnis tidak berpengaruh terhadap struktur modal. Sedangkan, likuiditas berpengaruh negatif signifikan terhadap struktur moda