A Distributed Framework for Traffic Flow Management in the Presence of Unmanned Aircraft

The integration of unmanned aircraft systems (UAS) into the airspace system is a key challenge facing air traffic management today. An important aspect of this challenge is how to determine and manage 4-dimensional trajectories for both manned and unmanned aircraft, and how to appropriately allocate resources among different aircraft. An integrated approach requires solving the traditional Air Traffic Flow Management (ATFM) problem to balance the capacity and demand of airport and airspace resources, but at a significantly larger scale. In doing so, aircraft connectivity constraints of commercial flights must be satisfied. In addition to these and the resource capacity constraints, geofencing constraints for unmanned aircraft that keep them within or outside a certain region of the airspace, must also be incorporated. This paper presents a distributed implementation of an integer programming approach for solving large-scale ATFM problems in the presence of unmanned aircraft. Given desired mission plans and flight-specific operating and delay costs, the proposed approach uses column generation to determine optimal trajectories in space and time, in the presence of network and flight connectivity constraints, airport and airspace capacity constraints, and geofencing constraints. Using projected demand for the year 2030 from the United States with approximately 48, 000 passenger flights and 29, 000 UAS operations (on a wide range of missions) per day, we show that our implementation can find nearly-optimal trajectories for a 24-hour period in less than 4 minutes. Furthermore, a rolling horizon implementation (with 6-8 hour time windows) results in run times of less than a minute. In addition to being the largest instances of the ATFM problem solved to date, these results represent the first effort to incorporate UAS trajectories into airspace and airport resource sharing problems.United States. National Aeronautics and Space Administration (Small Business Innovative Grant

Scheduling Aircraft Landings under Constrained Position Shifting

Optimal scheduling of airport runway operations can play an important role in improving the safety and efficiency of the National Airspace System (NAS). Methods that compute the optimal landing sequence and landing times of aircraft must accommodate practical issues that affect the implementation of the schedule. One such practical consideration, known as Constrained Position Shifting (CPS), is the restriction that each aircraft must land within a pre-specified number of positions of its place in the First-Come-First-Served (FCFS) sequence. We consider the problem of scheduling landings of aircraft in a CPS environment in order to maximize runway throughput (minimize the completion time of the landing sequence), subject to operational constraints such as FAA-specified minimum inter-arrival spacing restrictions, precedence relationships among aircraft that arise either from airline preferences or air traffic control procedures that prevent overtaking, and time windows (representing possible control actions) during which each aircraft landing can occur. We present a Dynamic Programming-based approach that scales linearly in the number of aircraft, and describe our computational experience with a prototype implementation on realistic data for Denver International Airport

A Phase-Field Study on the Effects of Nanoparticles on Solidification and Grain Growth

Nanoparticle reinforced alloys offer the potential of high strength, high temperature alloys. While promising, during rapid solidification processes, alloys suffer from nanoparticle clustering, which can discount any strength benefit. An open-source phase-field model is developed using PRISMS-PF to explore the impact of nanoparticles and clustering on alloy solidification. Heterogenous nucleation and grain boundary pinning are explicitly included, and a wide range of nanoparticle area fractions and nucleation rates are modeled. At low area fractions less than 0.05, particle clustering increases grain size between 15-45% compared to a random distribution. Our quantitative analyses inform a modified Zener grain size relationship that not only depends on nanoparticle size and area fraction, but also on the nucleation rate. Grain size first drastically decreases before plateauing at higher nucleation rates. Our simulations reveal a strong preference of nanoparticles pinning grain boundaries. Pinning fraction increases rapidly with nucleation rate before saturating between 0.85-0.90. Across the range of area fractions and nucleation rates considered, the random and clustered grain sizes each collapse to a simple analytical expression that depends only on nanoparticle radius and pinning fraction. Comparisons against experimental data reveal the expressions deduced from our analyses fit reported grain sizes better than classic Zener analysis. A simple model of strength and cost tradeoffs indicates nanoparticles can be a cost-effective way to improve alloy strength

BRCA1-regulated nuclear innate sensing of Herpesviral genome by IFI16 and IFI16’s acetylation is critical for its cytoplasmic trafficking and induction of innate responses: DOI: 10.14800/ics.1076

Sensing of invading DNA virus genomes appear to be triggered by a number of host cell DNA sensors depending on their subcellular localization which stimulate innate anti-viral responses such as the activation of type-I interferons (IFNs) and/or inflammasomes resulting in the  production of inflammatory IL-1? and IL-18 cytokines. With growing understanding of diverse identities whether these proteins function alone or  with other host cell molecules and the post-translational modifications affecting their functions are under intense investigations. Nuclear resident IFI16 have been shown to sense the episomal DNA genomes of herpes viruses resulting in the induction of IFI16-inflammasome and/or interferon responses. Here, we highlight our recent finding regarding the role of cellular  BRCA1, a transcription factor and DNA damage response protein, forming a distinct complex with IFI16 to regulate the nuclear innate sensing of herpes viral DNA and subsequent IFI16-ASC-procaspase-1 inflammasome complex formation and distribution to the cytoplasm leading into caspase-1 and IL-1? production. BRCA1 is also responsible for the cytoplasmic IFI16-STING signalosome activation and induction of IFN-? during de novo KSHV and HSV-1 infection. Our concurrent studies have also revealed that the histone acetyl transferase p300 mediated acetylation of nuclear IFI16 is a dynamic post-genome recognition event responsible for Ran dependent nuclear to cytoplasmic trafficking of IFI16 during herpesvirus infection. This post-translational modification is essential for IFI16-ASC interaction and inflammasome activation as well as for the association with STING in the cytoplasm resulting in IRF-3 phosphorylation, nuclear pIRF-3 localization and interferon-? production. Collectively, these comprehensive studies highlight that BRCA1 plays a hitherto unidentified immunomodulatory role to facilitate the anti-viral functions of IFI16 and acetylation of nuclear IFI16 is a necessary post-translational modification for innate responses during herpesvirus infection. These studies open up a new understanding of virus-host interplay, viral genome sensing and host innate anti-viral defense mechanisms

Kaposi’s Sarcoma Associated Herpesvirus Entry into Target Cells

Herpesvirus infection of target cells is a complex process involving multiple host cell surface molecules (receptors) and multiple viral envelope glycoproteins. Kaposi’s sarcoma associated herpesvirus (KSHV or HHV-8) infects a variety of in vivo target cells such as endothelial cells, B cells, monocytes, epithelial cells, and keratinocytes. KSHV also infects a diversity of in vitro target cells and establishes in vitro latency in many of these cell types. KSHV interactions with the host cell surface molecules and its mode of entry in the various target cells are critical for the understanding of KSHV pathogenesis. KSHV is the first herpesvirus shown to interact with adherent target cell integrins and this interaction initiates the host cell pre-existing signal pathways that are utilized for successful infection. This chapter discusses the various aspects of the early stage of KSHV infection of target cells, receptors used and issues that need to be clarified, and future directions. The various signaling events triggered by KSHV infection and the potential role of signaling events in the different stages of infection are summarized providing the framework and starting point for further detailed studies essential to fully comprehend the pathogenesis of KSHV

BRCA1-regulated nuclear innate sensing of Herpesviral genome by IFI16 and IFI16’s acetylation is critical for its cytoplasmic trafficking and induction of innate responses

Sensing of invading DNA virus genomes appear to be triggered by a number of host cell DNA sensors depending on their subcellular localization which stimulate innate anti-viral responses such as the activation of type-I interferons (IFNs) and/or inflammasomes resulting in the  production of inflammatory IL-1β and IL-18 cytokines. With growing understanding of diverse identities whether these proteins function alone or  with other host cell molecules and the post-translational modifications affecting their functions are under intense investigations. Nuclear resident IFI16 have been shown to sense the episomal DNA genomes of herpes viruses resulting in the induction of IFI16-inflammasome and/or interferon responses. Here, we highlight our recent finding regarding the role of cellular  BRCA1, a transcription factor and DNA damage response protein, forming a distinct complex with IFI16 to regulate the nuclear innate sensing of herpes viral DNA and subsequent IFI16-ASC-procaspase-1 inflammasome complex formation and distribution to the cytoplasm leading into caspase-1 and IL-1β production. BRCA1 is also responsible for the cytoplasmic IFI16-STING signalosome activation and induction of IFN-β during de novo KSHV and HSV-1 infection. Our concurrent studies have also revealed that the histone acetyl transferase p300 mediated acetylation of nuclear IFI16 is a dynamic post-genome recognition event responsible for Ran dependent nuclear to cytoplasmic trafficking of IFI16 during herpesvirus infection. This post-translational modification is essential for IFI16-ASC interaction and inflammasome activation as well as for the association with STING in the cytoplasm resulting in IRF-3 phosphorylation, nuclear pIRF-3 localization and interferon-β production. Collectively, these comprehensive studies highlight that BRCA1 plays a hitherto unidentified immunomodulatory role to facilitate the anti-viral functions of IFI16 and acetylation of nuclear IFI16 is a necessary post-translational modification for innate responses during herpesvirus infection. These studies open up a new understanding of virus-host interplay, viral genome sensing and host innate anti-viral defense mechanisms

Predicting Airspace Congestion using Approximate Queueing Models

We present an approximate method for the analysis of queueingdelays in highly dynamic networks with schedule-based stochasticarrivals and time-varying service times. We also develop anintuitively appealing network flow model representation of theproblem and compare the performance of both models to a much moredetailed simulation on several sample networks. The two approachesare applied to the problem of estimating queueing delays in theairspace, which is modeled as a node-capacitated network withtime-varying capacity constraints and aircraft departure-timeuncertainty. We demonstrate the use of these models in airspacecongestion prediction and airline schedule evaluation

Development of discontinuous Galerkin method for nonlocal linear elasticity

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2007.Includes bibliographical references (p. 75-81).A number of constitutive theories have arisen describing materials which, by nature, exhibit a non-local response. The formulation of boundary value problems, in this case, leads to a system of equations involving higher-order derivatives which, in turn, results in requirements of continuity of the solution of higher order. Discontinuous Galerkin methods are particularly attractive toward this end, as they provide a means to naturally enforce higher interelement continuity in a weak manner without the need of modifying the finite element interpolation. In this work, a discontinuous Galerkin formulation for boundary value problems in small strain, non-local linear elasticity is proposed. The underlying theory corresponds to the phenomenological strain-gradient theory developed by Fleck and Hutchinson within the Toupin-Mindlin framework. The single-field displacement method obtained enables the discretization of the boundary value problem with a conventional continuous interpolation inside each finite element, whereas the higher-order interelement continuity is enforced in a weak manner. The proposed method is shown to be consistent and stable both theoretically and with suitable numerical examples.by Ram Bala Chandran.S.M

A Dynamic Programming Algorithm for Robust Runway Scheduling

Abstract-An algorithm for generating schedules of airport runway operations that are robust to perturbations caused by system uncertainty is presented. The algorithm computes a tradeoff curve between runway throughput and the probability that random deviations of aircraft from the schedule violate system constraints and require intervention from air traffic controllers. The algorithm accommodates various operational constraints imposed by the terminal-area system such as minimum separation requirements between successive aircraft, earliest and latest times for each aircraft, precedence constraints among aircraft and the limited flexibility in deviating from the First-Come-First-Served (FCFS) order afforded to air traffic controllers (a concept known as Constrained Position Shifting). When the maximum allowable number of position shifts from the FCFS order is bounded by a constant, the complexity of the algorithm is O(n(L/ǫ) 3 ), where n is the number of aircraft, L is largest difference between the latest and earliest arrival time over all aircraft, and ǫ is the desired output accuracy