For a graph G with n vertices and m edges, we give a randomized Las Vegas algorithm that approximates a small balanced vertex separator of G in almost linear time. More precisely, we show the following, for any 2 3 ≤ α < 1 and any 0 < ε < 1 − α: If G contains an α-separator of size K, then our algorithm finds an (α + ε)-separator of size O(ε−1K2 log n) in time O(ε−1K3m log n) w.h.p. In particul...

Good flow and pressure control is essential for successful Underbalanced Drilling (UBD) operations. This work evaluates the use of Model Predictive Control (MPC) for integrated control of well conditions and the topside separation system during UBD. The downhole well pressure, separator liquid levels, and the separator pressure are controlled by manipulation of the rig pump, the choke, and the ...

We present I/O-efficient algorithms for computing optimal separator partitions of planar graphs. Our main result shows that, given a planar graph G with N vertices and an integer r > 0, a vertex separator of size O (N/√r) that partitions G into O(N/r) subgraphs of size at most r and boundary size O (√r) can be computed in O(sort(N)) I/Os, provided that M ≥ 56r log B. Together with the planar em...

Lithium-sulfur (Li-S) batteries have become promising candidates for electrical energy storage systems due to their high theoretical specific energy density, low cost and environmental friendliness. However, there are some technical obstacles of lithium-sulfur batteries to be addressed, such as the shuttle effect of polysulfides. Here, we introduced organically modified carbon nanotubes (CNTs) ...

We propose a class of graphs that would occur naturally in finite-element and finitedifference problems and we prove a bound on separators for this class of graphs. Graphs in this class are embedded in d-dimensional space in a certain manner. For d-dimensional graphs our separator bound is O(n(d−1)/d), which is the best possible bound. We also propose a simple randomized algorithm to find this ...

We introduce the notion of the width bounded geometric separator and develop the techniques for the existence of the width bounded separator in any d-dimensional Euclidean space. The separator is applied in obtaining 2 √ n) time exact algorithms for a class of NPcomplete geometric problems, whose previous algorithms take n √ n) time [2,5,1]. One of those problems is the well known disk covering...

Telecommunications providers expect products to perform reliably during operation in the field. Achieving the expected hardware reliability is due to an amalgamation of multiple factors. A significant contribution to reliable performance results from the incorporation of specific materials, which are very corrosion resistant and electrostatic discharge (ESD) safe during the design and manufactu...

Abstract The regulation of anions and cations at the atomic scale is great significance in membrane-based separation technologies. Ionic transport techniques could also play a crucial role developing high-performance alkali metal batteries such as metal-sulfur metal-selenium batteries, which suffer from non-uniform ions (e.g., Li + or Na ) detrimental shuttling effect polysulfide/polyselenide a...