skip to main content

Search for: All records

Creators/Authors contains: "Nelson, C."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. For years, there has been discussion about physical security in the maritime transportation system (MTS). That discussion has led to standards, regulations, etc. In recent years, there has been an increasing interest in cyber security in the MTS that has led to discussions about best practices for cyber security. It is likely that many future attacks on the MTS (and other systems) will be multi-modal, including both a cyber and a physical component. As a simple example, hacking into security cameras at a port increases vulnerability to a physical intrusion. Thus, a cyber attack could be a precursor to amore »physical attack, and in fact the opposite could also be the case. This paper presents scenarios of combined cyber and physical attacks and describes ways to understand their likelihood based on ease of attack and seriousness of potential consequences.« less
  2. Abstract The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hardmore »scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.« less
    Free, publicly-accessible full text available December 1, 2023
  3. Abstract The ATLAS experiment at the Large Hadron Collider has a broad physics programme ranging from precision measurements to direct searches for new particles and new interactions, requiring ever larger and ever more accurate datasets of simulated Monte Carlo events. Detector simulation with Geant4 is accurate but requires significant CPU resources. Over the past decade, ATLAS has developed and utilized tools that replace the most CPU-intensive component of the simulation—the calorimeter shower simulation—with faster simulation methods. Here, AtlFast3, the next generation of high-accuracy fast simulation in ATLAS, is introduced. AtlFast3 combines parameterized approaches with machine-learning techniques and is deployed tomore »meet current and future computing challenges, and simulation needs of the ATLAS experiment. With highly accurate performance and significantly improved modelling of substructure within jets, AtlFast3 can simulate large numbers of events for a wide range of physics processes.« less
    Free, publicly-accessible full text available December 1, 2023
  4. Decision makers in all kinds of organizations, and in particular those concerned with homeland security, need to be able to easily flag trends so that they can respond, for example with a reallocation of resources or a review of policies and procedures. This paper introduces a simple-to-use tool called the TrendFlagger that allows a decision maker to get evidence that a trend may be appearing without requiring statistical sophistication. The TrendFlagger will be illustrated using a source of data that organizations might use to study shipping trends and vessel behavior, the Automatic Identification System (AIS) now required by international agreementmore »on all ships of 300 gross tons or more and all passenger ships.« less
  5. Free, publicly-accessible full text available May 1, 2023