The complexity of recognizing linear systems with certain integrality properties

Let A be a 0 - 1 matrix with precisely two 1's in each column and let 1 be the all-one vector. We show that the problems of deciding whether the linear system Ax ≥ 1,x ≥ 0 (1) defines an integral polyhedron, (2) is totally dual integral (TDI), and (3) box-totally dual integral (box-TDI) are all co-NP-complete, thereby confirming the conjecture on NP-hardness of recognizing TDI systems made by Edmonds and Giles in 1984. © 2007 Springer-Verlag.preprin

Prediction and analysis of slab quality based on neural network combined with particle swarm optimization (PSO)

Based on the study of the mechanism of bloom crack, the main factors affecting the quality of bloom are determined. The intelligent optimization algorithm combining PSO and Back Propagation(BP) neural network is introduced to establish the prediction model based on typical defects. Collect on-site sample data, normalize it, and PSO is used to recalculate the weights and thresholds to accelerate the convergence and improve the accuracy and stability of the results. The experimental results show that the prediction accuracy of the optimized neural network model is high, and it is closer to the actual production of continuous casting

Water, waste, energy and food nexus in Brazil: Identifying a resource interlinkage research agenda through a systematic review

The resource nexus consists of a framework to address interlinkages between natural resources and systems that provide water, energy, food and waste management. It transcends traditional assessments conducted in “silos”, raising trade-offs and synergies that are rarely acknowledged. The nexus framework is intrinsically context-specific, as each respective region has particularities in terms of critical interlinkages. Brazil is the world's eighth largest economy [1] and is heavily reliant on natural resources. This paper considers Brazil to be a textbook case for nexus research that identifies critical interlinkages that are neglected by literature, which is typically based on single-resource analysis. It proposes a research agenda to advance resource nexus assessments and improve resource governance in Brazil. We propose a novel method for nexus research, systematically reviewing geographical context-specific papers in relevant single nexus dimensions and establishing resource interlinkages that characterise research gaps and policy priorities. We found that 36% of practices reviewed involve more than one resource at a time, characterising interlinkages not analysed by the literature. Lastly, selected quantitative indicators were used to identify critical interlinkages by analysing the representativeness of practices in the national context, and the relevance of synergies or trade-offs for Brazil. Critical interlinkages in Brazil were found to be irrigation for energy crop expansion (water, food and energy); transport biofuels and fuelwood (water, energy, food); deforestation for new pasture (water, energy, food); and hydropower generation (water and energy). These are, therefore, priorities for future nexus research and for efforts to address synergies and trade-offs in resource governance

The circumference of a graph with no K3, t-minor

It was shown by Chen and Yu that every 3-connected planar graph G contains a cycle of length at least | G |log 3 2, where | G | denotes the number of vertices of G. Thomas made a conjecture in a more general setting: there exists a function β (t) > 0 for t ≥ 3, such that every 3-connected graph G with no K3, t-minor, t ≥ 3, contains a cycle of length at least | G |β (t). We prove that this conjecture is true with β (t) = log8 t t + 1 2. We also show that every 2-connected graph with no K2, t-minor, t ≥ 3, contains a cycle of length at least | G | / tt - 1. © 2006 Elsevier Inc. All rights reserved.preprin

On the Temperature Dependence of the Lifetime of Thermally Isolated Metastable Clusters

The temperature dependence of the lifetime of the thermally isolated metastable N8 cubane up to its decay into N2 molecules has been calculated by the molecular dynamics method. It has been demonstrated that this dependence significantly deviates from the Arrhenius law. The applicability of the finite heat bath theory to the description of thermally isolated atomic clusters has been proved using statistical analysis of the results obtained.Comment: 14 pages, 4 figure

Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems

Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems

Mean-field theory of the spin-Peierls systems: Application to CuGeO3

A mean-field theory of the spin Peierls systems based on the two dimensional dimerized Heisenberg model is proposed by introducing an alternating bond order parameter. Improvements with respect to previous mean-field results are found in the one-dimensional limit for the ground state and the gap energies. In two dimensions, the analysis of the competition between antiferromagnetic long range order and the spin-Peierls ordering is given as a function of the coupling constants. We show that the lowest energy gap to be observed does not have a singlet-triplet character in agreement with the low temperature thermodynamic properties of CuGeO3.Comment: 3 Revtex pages. Submitted to Rapid Comm. Figures available upon reques

Eddy current studies from the undulator-based positron source target wheel prototype

The ef­fi­cien­cy of fu­ture positron sources for the next gen­er­a­tion of high-en­er­gy par­ti­cle col­lid­ers (e.g. ILC, CLIC, LHeC) can be im­proved if the positron-pro­duc­tion tar­get is im­mersed in the mag­net­ic field of ad­ja­cent cap­ture op­tics. If the tar­get is also ro­tat­ing due to heat de­po­si­tion con­sid­er­a­tions then eddy cur­rents may be in­duced and lead to ad­di­tion­al heat­ing and stress­es. In this paper we pre­sent data from a ro­tat­ing tar­get wheel pro­to­type for the base­line ILC positron source. The wheel has been op­er­at­ed at rev­o­lu­tion rates up to 1800rpm in fields of the order of 1 Tesla. Com­par­isons are made be­tween torque data ob­tained from a trans­duc­er on the tar­get drive shaft and the re­sults of fi­nite-el­e­ment sim­u­la­tions. Ro­tor­dy­nam­ics is­sues are pre­sent­ed and fu­ture ex­per­i­ments on other as­pects of the positron source tar­get sta­tion are con­sid­ered