Stokes phenomenon and matched asymptotic expansions

This paper describes the use of matched asymptotic expansions to illuminate the description of functions exhibiting Stokes phenomenon. In particular the approach highlights the way in which the local structure and the possibility of finding Stokes multipliers explicitly depend on the behaviour of the coefficients of the relevant asymptotic expansions

Synthesis of Kentucky’s Traveler Information Systems

After the United States Department of Transportation (USDOT) petitioned the Federal Communications Commission (FCC) to establish a dedicated phone number for real-time travel information services, the abbreviated 511 dialing code was founded in July 2000. The FCC reasoned that 511 services could reduce traffic congestion, air pollution, and the inefficient use of fossil fuels. 511 would, in turn, improve traveler safety. In 2010, the Federal Highway Administration (FHWA) mandated a set of requirements for systems that deliver real-time traffic information to the public. States DOTs were asked to comply with this mandate by November 2014. Many states, in addition to maintaining websites, also have dedicated mobile apps and a social media presence (e.g., one or multiple Twitter accounts) that communicate data on traffic and road conditions. Analysis of 511 usage data indicated that the number of phone calls received has dropped sharply since the mid-2000s. Conversely, the amount of traffic handled by KYTC’s websites and mobile apps has increased. Like the phone system, websites and mobile apps garner the most traffic during the winter months. Discussions with KYTC 511 stakeholders revealed that phone system will be less relevant — although necessary to maintain, particularly in rural areas. There was significant consensus among KYTC stakeholders about the strengths of the state’s current approach to delivering traffic information, and a number of improvements were put forward to enhance it in the future. A survey of Kentucky drivers revealed that a majority get their traffic information through digital content providers. Services such as Google and Waze are popular for retrieving maps and driving directions, while television and radio play an important role still, especially for the provision of information during hazardous weather. Government-provided services (i.e., 511, TRIMARC) are less popular among drivers, and only garner a fraction of the traffic of online services and traditional media. Discussions with other state DOTs revealed that many other states are currently in the process of rethinking their 511 and traveler information systems. Many plan to retool these over the next 2–3 years. While there was agreement among state DOTs that they will continue to provide authoritative traveler information, how they carry out this mandate is somewhat unclear

Discovery of an OVI Emitting Nebula around the Hot White Dwarf KPD 0005+5106

A survey of diffuse interstellar sight lines observed with the Far Ultraviolet Spectroscopic Explorer has led to the serendipitous discovery of a high-ionization nebula around the hot white dwarf KPD 0005+5106. The nebula has an OVI 1032A surface brightness of up to 25,000 photons/s/cm^2/sr, making it the brightest region of extended OVI emission in our survey. Photoionization models using the incident white dwarf continuum successfully reproduce the observed OVI intensity. The OVI emission arises in the highly ionized inner region of a planetary nebula around KPD 0005+5106. This newly discovered nebula may be one member of a class of high-ionization planetary nebulae that are difficult to detect in the optical, but which can be easily identified in the ultraviolet.Comment: accepted for publication in ApJL, 11 pages including 2 figure

FUSE Detection of Galactic OVI Emission in the Halo above the Perseus Arm

Background observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) toward l=95.4, b=36.1 show OVI 1032,1038 in emission. This sight line probes a region of stronger-than-average soft X-ray emission in the direction of high-velocity cloud Complex C above a part of the disk where Halpha filaments rise into the halo. The OVI intensities, 1600+/-300 ph/s/cm^2/sr (1032A) and 800+/-300 ph/s/cm^2/sr (1038A), are the lowest detected in emission in the Milky Way to date. A second sight line nearby (l=99.3, b=43.3) also shows OVI 1032 emission, but with too low a signal-to-noise ratio to obtain reliable measurements. The measured intensities, velocities, and FWHMs of the OVI doublet and the CII* line at 1037A are consistent with a model in which the observed emission is produced in the Galactic halo by hot gas ejected by supernovae in the Perseus arm. An association of the observed gas with Complex C appears unlikely.Comment: accepted for publication in ApJL, 11 pages including 3 figure

The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5

We report observations of the hot post-asymptotic giant branch star ZNG 1 in the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic Explorer (FUSE). From the resulting spectrum, we derive an effective temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) = 3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon (2.6% by mass), nitrogen (0.51%) and oxygen (0.37%) abundances. The spectrum shows evidence for a wind with terminal velocity near 1000 km/s and an expanding shell of carbon- and nitrogen-rich material around the star. The abundance pattern of ZNG 1 is suggestive of the ``born-again'' scenario, whereby a star on the white-dwarf cooling curve undergoes a very late shell flash and returns to the AGB, but the star's rapid rotation is more easily explained by a previous interaction with a binary companion.Comment: 8 pages, 2 PostScript figures, Latex with emulateapj5. Accepted for publication in ApJ Letter

Final Calibration of the Berkeley Extreme and Far-Ultraviolet Spectrometer on the ORFEUS-SPAS I and II Missions

The Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) flew as part of the ORFEUS telescope on the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The data obtained by this instrument have now entered the public domain. To facilitate their use by the astronomical community, we have re-extracted and re-calibrated both data sets, converted them into a standard (FITS) format, and placed them in the Multimission Archive at Space Telescope (MAST). Our final calibration yields improved wavelength scales and effective-area curves for both data sets.Comment: To appear in the January 2002 issue of the PASP. 17 pages with 9 embedded postscript figures; uses emulateapj5.st

Generalized Master Equations for Non-Poisson Dynamics on Networks

The traditional way of studying temporal networks is to aggregate the dynamics of the edges to create a static weighted network. This implicitly assumes that the edges are governed by Poisson processes, which is not typically the case in empirical temporal networks. Consequently, we examine the effects of non-Poisson inter-event statistics on the dynamics of edges, and we apply the concept of a generalized master equation to the study of continuous-time random walks on networks. We show that the equation reduces to the standard rate equations when the underlying process is Poisson and that the stationary solution is determined by an effective transition matrix whose leading eigenvector is easy to calculate. We discuss the implications of our work for dynamical processes on temporal networks and for the construction of network diagnostics that take into account their nontrivial stochastic nature

Developing a Baseline for Customer Satisfaction in the Kentucky Transportation Cabinet\u27s Department of Vehicle Regulation

Among the Kentucky Transportation Cabinet’s (KYTC) business units, the Department of Vehicle Regulation (DVR) has the most interactions with members of the public and other government agencies. Given its high profile and public visibility, it is critical for the department to provide high-quality customer service. Lacking data on customer perceptions of DVR’s level of service, the department commissioned researchers at the Kentucky Transportation Center (KTC) to conduct a baseline and rebaseline customer satisfaction surveys. Along with administering surveys to external customers, KTC’s research team also polled DVR staff to gauge employee morale and identify areas which could be improved. Approximately 90% of departmental staff believe that DVR provides a high level of customer service, and most viewed the department’s divisions favorably. Staff, however, noted the importance of fostering an open, equitable, and collaborative workspace as well as the importance of having up-to-date technological tools to perform daily job functions. With respect to the baseline and rebaseline external customer surveys, this study measured a slight decline in overall customer satisfaction. In the baseline survey, 81% of respondents were very or somewhat satisfied with the service they received; in the rebaseline survey 77% said the same. Regression modeling found a strong negative relationship between number of call escalations (i.e., call transfers) and customer satisfaction; call duration had a smaller but negative impact on customer satisfaction. Survey respondents expressed a growing preference for using electronic means (email, website) to interact with DVR. Moving forward, it will be critical for DVR to dedicate resources to improving its website and streamlining other modes of electronic communication, reducing the number of call escalations, and shortening average call durations – particularly hold times

A complex ray-tracing tool for high-frequency mean-field flow interaction effects in jets

This paper presents a complex ray-tracing tool for the calculation of high-frequency Green’s functions in 3D mean field jet flows. For a generic problem, the ray solution suffers from three main deficiencies: multiplicity of solutions, singularities at caustics, and the determining of complex solutions. The purpose of this paper is to generalize, combine and apply existing stationary media methods to moving media scenarios. Multiplicities are dealt with using an equivalent two-point boundary-value problem, whilst non-uniformities at caustics are corrected using diffraction catastrophes. Complex rays are found using a combination of imaginary perturbations, an assumption of caustic stability, and analytic continuation of the receiver curve. To demonstrate this method, the ray tool is compared against a high-frequency modal solution of Lilley’s equation for an off-axis point source. This solution is representative of high-frequency source positions in real jets and is rich in caustic structures. A full utilization of the ray tool is shown to provide excellent results<br/

Asymptotic analysis for singularly perturbed convection-diffusion equations with a turning point

Turning points occur in many circumstances in fluid mechanics. When the viscosity is small, very complex phenomena can occur near turning points, which are not yet well understood. A model problem, corresponding to a linear convection-diffusion equation (e.g., suitable linearization of the Navier-Stokes or B&amp;#769;nard convection equations) is considered. Our analysis shows the diversity and complexity of behaviors and boundary or interior layers which already appear for our equations simpler than the Navier-Stokes or B&amp;#769;nard convection equations. Of course the diversity and complexity of these structures will have to be taken into consideration for the study of the nonlinear problems. In our case, at this stage, the full theoretical (asymptotic) analysis is provided. This study is totally new to the best of our knowledge. Numerical treatment and more complex problems will be considered elsewhere.open91