Search for: All records

We use the excluded volume Hadron Resonance Gas (HRG) model with the most up-to-date hadron list to calculate η T/w at low temperatures and at finite baryon densities ρ B . This η T/w is then matched to a QCD-based shear viscosity calculation of the QGP for different profiles of η T/w across T,μ B including cross-over and critical point transitions. When compared to ideal hydrodynamic trajectories across T,μ B , we find that the η T/w (T,μ B ) profiles would require initial conditions at much larger baryon density to reach the same freeze-out point. 

Abstract We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter ofβUMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak (βUMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements ofβUMa in the near-infrared (Center for High Angular Resolution Astronomy (CHARA) Array, 1.149 ± 0.014 mas) and mid-infrared (Keck Nuller, 1.08 ± 0.07 mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of 1.07 ± 0.04 (stat) ± 0.05 (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum ofβUMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of 9700 ± 200 ± 200 K, consistent with ultraviolet spectrophotometry, and an age of 390 ± 29 ± 32 Myr, using MESA Isochrones and Stellar Tracks. This age is consistent with 408 ± 6 Myr from the CHARA Array angular diameter. 

n many countries, sharing has become a significant approach to problems of spectrum allocation and assignment. As this approach moves from concept to reality, it is reasonable to expect an increase in interference or usage conflict events between sharing parties. Scholars such as Coase, Demsetz, Stigler, and others have argued that appropriate enforcement is critical to successful contracts (such as spectrum sharing agreements) and Polinsky, Shavell, and others have analyzed enforcement mechanisms in general. While many ex-ante measures may be used, reducing the social costs of ex-ante enforcement means shifting the balance more toward ex-post measures. Ex post enforcement requires detection, data collection, and adjudication methods. At present, these methods are ad hoc (operating in a decentralized way between parties) or fairly costly (e.g., relying on the FCC Enforcement Bureau). The research presented in this paper is the culmination of an NSF-funded inquiry into how and what enforcement functions can be automated. 

Cooperative wireless networks, enabled by Cognitive Radios, facilitate mobile users to dynamically share access to spectrum. However, spectrum bands can be accessed illegitimately by malicious users. Therefore, the success of dynamic spectrum sharing relies on automated enforcement of spectrum policies. While the focus has been on ex ante spectrum enforcement, this work explores new approaches to address efficient ex post spectrum enforcement. The main objective of this work is to ensure maximum coverage of the area of enforcement and accurate detection of spectrum access violation. The first objective is achieved with the help of Lloyd's algorithm to divide the enforcement area into a set of uniformly sized coverage regions. The interference detection accuracy is achieved through crowdsourcing of the spectrum access monitoring to volunteers, based on their computational capabilities, location attributes and reputation. A simulation framework was developed in CSIM19 (C++ version) to analyze the performance of the proposed system over the entire area of enforcement. The results show that the proposed scheme ensures efficient coverage of all the channels and regions in the area of enforcement and a high average accuracy of detection. 

In many countries, sharing has become a significant approach to problems of spectrum allocation and assignment. As this approach moves from concept to reality, it is reasonable to expect an increase in interference or usage conflict events between sharing parties. Scholars such as Coase, Demsetz, Stigler, and others have argued that appropriate enforcement is critical to successful contracts (such as spectrum sharing agreements) and Polinsky, Shavell, and others have analyzed enforcement mechanisms in general. While many ex-ante measures may be used, reducing the social costs of ex-ante enforcement means shifting the balance more toward ex-post measures. Ex post enforcement requires detection, data collection, and adjudication methods. At present, these methods are ad hoc (operating in a decentralized way between parties) or fairly costly (e.g., relying on the FCC Enforcement Bureau). The research presented in this paper is the culmination of an NSF-funded inquiry into how and what enforcement functions can be automated. 

Enforcement, adjudication, and litigation enacted by the Federal Communications Commission (FCC) resides at an interesting intersection between traditional law and normative common property resource agreements – similar to those in common pool resources. Despite being granted specific legal powers by Congress, the FCC works to dissolve contentions that arise between spectrum incumbents through market dispute resolutions mediated through their Enforcement Bureau’s Market and Dispute Resolution Division (MDRD). The MDRD mediates and adjudicates a myriad of complaint types brought on by “market participants, entities, and organizations against common carriers, commercial and mobile data service providers, and/or utility pole operators” (EB-Market Disputes and Resolution Division, n.d.). The MDRD’s decision to promote resolutions between complainants and defendants is unique in terms of traditional enforcement mechanisms – especially as a primary regulatory agency. The initiative to have stakeholders mediate, negotiate, and ultimately settle their disputes on their level is reminiscent of dispute remediation tactics observed in common pool resource environments. To investigate this approach to enforcement, adjudication, and litigation further, we utilize the Institutional Analysis and Development (IAD) Framework developed by Elinor Ostrom. Used to scaffold a myriad of policy, regulatory, and traditional CPRs, the IAD Framework incites a unique investigation into the agreements that arise between disputing parties.