Physical Sciences and Mathematics Commons^™

The Halo Occupation Distribution Of X-Ray-Bright Active Galactic Nuclei: A Comparison With Luminous Quasars, Jonathan Richardson, Suchetana Chatterjee, Zheng Zheng, Adam D. Myers, Ryan Hickox

Dartmouth Scholarship

We perform halo occupation distribution (HOD) modeling of the projected two-point correlation function (2PCF) of high-redshift (z~1.2) X-ray-bright active galactic nuclei (AGN) in the XMM-COSMOS field measured by Allevato et al. The HOD parameterization is based on low-luminosity AGN in cosmological simulations. At the median redshift of z~1.2, we derive a median mass of (1.02+0.21/-0.23)x10^{13} Msun/h for halos hosting central AGN and an upper limit of ~10% on the AGN satellite fraction. Our modeling results indicate (at the 2.5-sigma level) that X-ray AGN reside in more massive halos compared to more bolometrically luminous, optically-selected quasars at similar redshift. The modeling …

A Simulation-Based Study Of Server Location Selection Rules In Manets Utilising Threshold Cryptography, Alastair Nisbet

Australian Information Security Management Conference

Truly Ad Hoc wireless networks where a spontaneous formation of a network occurs and there is no prior knowledge of nodes to each other present significant security challenges, especially as entirely online configuration of nodes with encryption keys must be performed. Utilising threshold cryptography in this type of MANET can greatly increase the security by requiring servers to collaborate to form a single Certificate Authority (CA). In this type of CA responsibility for certificate services is shared between a threshold of servers, greatly increasing security and making attack against the CA considerably more difficult. Choosing which nodes to take on …

Evidence For 20th Century Climate Warming And Wetland Drying In The North American Prairie Pothole Region, Brett A. Werner, W. Carter Johnson, Glenn R. Guntenspergen

Natural Resource Management Faculty Publications

The Prairie Pothole Region (PPR) of North America is a globally important resource that provides abundant and valuable ecosystem goods and services in the form of biodiversity, groundwater recharge, water purification, flood attenuation, and water and forage for agriculture. Numerous studies have found these wetlands, which number in the millions, to be highly sensitive to climate variability. Here, we compare wetland conditions between two 30-year periods (1946–1975; 1976–2005) using a hindcast simulation approach to determine if recent climate warming in the region has already resulted in changes in wetland condition. Simulations using the WETLANDSCAPE model show that 20th century climate …

The Fast And Furious Decay Of The Peculiar Type Ic Supernova 2005ek, M. R. Drout, A. M. Soderberg, P. A. Mazzali, J. T. Parrent

Dartmouth Scholarship

We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude of M_R = –17.3 and decaying by ~3 mag in the first 15 days post-maximum, SN 2005ek is among the fastest Type I supernovae observed to date. The spectra of SN 2005ek closely resemble those of normal SN Ic, but with an accelerated evolution. There is evidence for the onset of nebular features at only nine days post-maximum. Spectroscopic modeling reveals an ejecta mass of ~0.3 M _☉ that is dominated by oxygen (~80%), while the pseudo-bolometric light …

The Evolution Of Modular Product Architectures And The Emergence Of Platform Ecosystems, C. Jason Woodard, Eric K. Clemons

Research Collection School Of Computing and Information Systems

While a large body of research has examined the advantages and disadvantages of modularity in product design, studies of modularization have tended to focus on settings in which a product’s architecture is determined by a single designer or designers within a single organization. In this paper, we ask whether modularity can arise in a decentralized setting where high-value designs are rewarded but designers’ ability to coordinate with each other and anticipate the consequences of their actions is limited—in short, whether modularity can evolve. To answer this question, we developed an agent-based model in which boundedly rational firms combine components into …

Characterization Of Optical Communication In A Leader-Follower Unmanned Underwater Vehicle Formation, Firat Eren, Shachak Pe'eri, May-Win Thein

Center for Coastal and Ocean Mapping

As part of the research to development an optical communication design of a leader-follower formation between unmanned underwater vehicles (UUVs), this paper presents light field characterization and design configuration of the hardware required to allow the use of distance detection between UUVs. The study specifically is targeting communication between remotely operated vehicles (ROVs). As an initial step in this study, the light field produced from a light source mounted on the leader UUV was empirically characterized and modeled. Based on the light field measurements, a photo-detector array for the follower UUV was designed. Evaluation of the communication algorithms to monitor …

Simulating Inflation, Ryan M. Heathcote

Senior Honors Theses

Inflation is a common problem in modern economics, and it seems to persist, requiring government financial policy intervention on a regular basis in order to properly manage. The mechanics of inflation are difficult to understand, since the best metric modern society has for inflation involves taking samples of prices across the country. A simulation can give deeper insight into more than the mere fact that prices rise over time: a simulation can help to answer the “why” question. The problem with this statement is that developing a simulation is not as simple as writing some code. A simulation is developed …

In Silico Surveillance: Evaluating Outbreak Detection With Simulation Models, Bryan Lewis, Stephen Eubank, Allyson M. Abrams, Ken Kleinman

Public Health Department Faculty Publication Series

Background

Detecting outbreaks is a crucial task for public health officials, yet gaps remain in the systematic evaluation of outbreak detection protocols. The authors’ objectives were to design, implement, and test a flexible methodology for generating detailed synthetic surveillance data that provides realistic geographical and temporal clustering of cases and use to evaluate outbreak detection protocols.

Methods

A detailed representation of the Boston area was constructed, based on data about individuals, locations, and activity patterns. Influenza-like illness (ILI) transmission was simulated, producing 100 years ofin silico ILI data. Six different surveillance systems were designed and developed using gathered cases …

Special Issue: M&S Optimization Applications In Industry And Engineering, Part 2, Rafael Diaz, Andreas Tolk

VMASC Publications

(First paragraph) Welcome to the second part of the special issue on modeling and simulation (M&S) optimization applications in industry and engineering. This issue incorporates additional publications that reflect various applications and areas of simulation and optimization.

Electric Field Standing Wave Effects In Ft-Ir Transflection Spectra Of Biological Tissue Sections: Simulated Models Of Experimental Variability, Tomasz P. Wrobel, Barbara Wajnchold, Hugh Byrne, Malgorzata Baranska

Articles

The so-called electric field standing wave effect (EFSW) has recently been demonstrated to significantly distort FT-IR spectra acquired in a transflection mode, both experimentally and in simulated models, bringing into question the appropriateness of the technique for sample characterization, particularly in the field of spectroscopy of biological materials. The predicted effects are most notable in the regime where the sample thickness is comparable to the source wavelength. In this work, the model is extended to sample thicknesses more representative of biological tissue sections and to include typical experimental factors which are demonstrated to reduce the predicted effects. These include integration …

Collective Librations Of Water Molecules In The Crystal Lattice Of Rubidium Bromide: Experiment And Simulation, L M. Lepodise, J Horvat, Roger A. Lewis

Australian Institute for Innovative Materials - Papers

Terahertz spectroscopy of RbBr reveals four prominent absorption lines at room temperature and a further 15 lines at 10 K. Via density-functional-theory (DFT) numerical modelling using the PBE0 hybrid GGA functional, all the absorptions are identified as correlated librations of water molecules in the RbBr lattice. Each libration mode is a combination of rocking, wagging and twisting motions of the water molecules. The number of libration lines and numerical modelling show that the C2v symmetry of water in RbBr is broken. Our modelling shows that the distribution of libration amplitudes and phases for different water molecules in the RbBr unit …

Mesoscopic Methods In Engineering And Science, Jos Derksen, Dmitry Eskin, Li-Shi Luo, Manfred Krafczyk

Mathematics & Statistics Faculty Publications

(First paragraph) Matter, conceptually classified into fluids and solids, can be completely described by the microscopic physics of its constituent atoms or molecules. However, for most engineering applications a macroscopic or continuum description has usually been sufficient, because of the large disparity between the spatial and temporal scales relevant to these applications and the scales of the underlying molecular dynamics. In this case, the microscopic physics merely determines material properties such as the viscosity of a fluid or the elastic constants of a solid. These material properties cannot be derived within the macroscopic framework, but the qualitative nature of the …