991 research outputs found
Evaluation of a composite mobile holographic nondestructive test system
A simplified theoretical model for the interpretation of the double-exposure holographic interference fringe loci due to the general three-dimensional displacements was derived for the specific composite mobile holographic nondestructive test system. The model, representing a good approximation to a more tedious theoretical result, predicts that a combination of in-plane and out-of-plane displacements of the surface will produce concentric circular-shaped fringe patterns with locations of their center affected by the displacements. Appropriate experiments were designed and carried out for the test of the validity of the theory. These experiments include the taking of double-exposure holograms of in-plane translations and combined in-plane and out-of-plane translations. The simplified model agreed quite well with the experimental results. Experimentally observed effects due to the curvature of the test plate and the variations of the angles of incidence of the laser light suggest that in order for the simplified model to be able to predict the test results more accurately, incidence and reflection of the laser light should be chosen as nearly perpendicular to the surface of the tested object as possible
On the fate of singularities and horizons in higher derivative gravity
We study static spherically symmetric solutions of high derivative gravity
theories, with 4, 6, 8 and even 10 derivatives. Except for isolated points in
the space of theories with more than 4 derivatives, only solutions that are
nonsingular near the origin are found. But these solutions cannot smooth out
the Schwarzschild singularity without the appearance of a second horizon. This
conundrum, and the possibility of singularities at finite r, leads us to study
numerical solutions of theories truncated at four derivatives. Rather than two
horizons we are led to the suggestion that the original horizon is replaced by
a rapid nonsingular transition from weak to strong gravity. We also consider
this possibility for the de Sitter horizon.Comment: 15 pages, 3 figures, improvements and references added, to appear in
PR
Correspondence between Jordan-Einstein frames and Palatini-metric formalisms
We discuss the conformal symmetry between Jordan and Einstein frames
considering their relations with the metric and Palatini formalisms for
modified gravity. Appropriate conformal transformations are taken into account
leading to the evident connection between the gravitational actions in the two
mentioned frames and the Hilbert-Einstein action with a cosmological constant.
We show that the apparent differences between Palatini and metric formalisms
strictly depend on the representation while the number of degrees of freedom is
preserved. This means that the dynamical content of both formalism is
identical.Comment: 6 pages, to appear in Mod. Phys. Lett.
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Value-Based Routing and Preference-Based Routing in Customer Contact Centers
Telephone call centers and their generalizations—customer contact centers—usually handle several types of customer service requests (calls). Since customer service representatives (agents) have different call-handling abilities and are typically cross-trained in multiple skills, contact centers exploit skill-based routing (SBR) to assign calls to appropriate agents, aiming to respond properly as well as promptly. Established agent-staffing and SBR algorithms ensure that agents have the required call-handling skills and that call routing is performed so that constraints are met for standard congestion measures, such as the percentage of calls of each type that abandon before starting service and the percentage of answered calls of each type that are delayed more than a specified number of seconds. We propose going beyond traditional congestion measures to focus on the expected value derived from having particular agents handle various calls. Expected value might represent expected revenue or the likelihood of first-call resolution. Value might also reflect agent call-handling preferences. We show how value-based routing (VBR) and preference-based routing (PBR) can be introduced in the context of an existing SBR framework, based on static-priority routing using a highly-structured priority matrix, so that constraints are still met for standard congestion measures. Since an existing SBR framework is used to implement VBR and PBR, it is not necessary to replace the automatic call distributor (ACD). We show how mathematical programming can be used, with established staffing requirements, to find a desirable priority matrix. We select the priority matrix to use during a specified time interval (e.g., 30-minute period) by maximizing the total expected value over that time interval, subject to staffing constraints
Increasing Physical Activity Among African-American Women and Girls
WHITT-GLOVER, M. C., D. J. BRAND, M. E. TURNER, S. A. WARD, and E. M. JACKSON. Increasing physical activity among African-American women and girls. Curr. Sports Med. Rep., Vol. 8, No. 6, pp. 318-324, 2009. The benefits of physical activity on diseases and risk factors are well known. Despite the known benefits, many segments of the population, particularly African-American women and girls, do not obtain adequate levels of physical activity. Strategies are needed to identify successful and sustainable interventions to increase physical activity among this population. We reviewed literature published between 2007 and 2009 that focused on increasing physical activity or fitness among this population. We identified 37 studies, 11 of which focused on increasing physical activity. This article summarizes the findings from those 11 studies and provides recommendations for improving strategies to increase physical activity in African-American women and girls
Wastewater-based Estimation of Substances Discharged at the Rest Areas along the State Highways in Kentucky
The availability of licit and illicit stimulants and its adverse consequences on public health has emerged as a major drug threat to communities in the United States. Despite several drug-involved traffic incidents along the interstate highways, this report represents the first comprehensive and quantitative report of drugs discharged at the rest areas along the interstate highways. In this National Institute of Justice-funded study, the amount of several discharged drugs focusing on stimulants but also including opioids and prescription antipsychotics are being measured in raw wastewater collected from five rest areas and a truck servicing facility using a state-of-the-art mass spectrometry technique. Three stimulants (cocaine, methamphetamine, and amphetamine), two opioids (hydrocodone and tramadol), THC metabolite, and four antidepressants (venlafaxine, citalopram, fluoxetine, and sertraline) were detected in all of the collected wastewater samples in the early phases of the project. Methamphetamine was the most prevalent stimulant (40.0-1240 mg/d) followed by the cocaine metabolite (9.18-385 mg/d) and amphetamine (14.9-97.9 mg/d). The rest area users normalized methamphetamine discharge in Christian County rest area (I-24E) was 1.8 folds higher than in Whitehaven rest area (I-24W) and 7.8 folds higher than in the Laurel County truck service facility (I-75). The significantly higher ratio of cocaine and its metabolite (\u3e1.0) found in the Whitehaven rest area suggested the possibility of a direct discharge of cocaine in two select days in October. Overall, we established a unique collaboration among the Appalachian High Intensity Drug Trafficking Area (HIDTA), the Kentucky Transportation Cabinet, Cabinet for Health and Family Services, Murray State University and the University of Kentucky
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