2,823 research outputs found
Isochoric, isobaric and ultrafast conductivities of aluminum, lithium and carbon in the warm dense matter (WDM) regime
We study the conductivities of (i) the equilibrium isochoric state
(), (ii) the equilibrium isobaric state (),
and also the (iii) non-equilibrium ultrafast matter (UFM) state () with the ion temperature less than the the electron temperature
. Aluminum, lithium and carbon are considered, being increasingly complex
warm dense matter (WDM) systems, with carbon having transient covalent bonds.
First-principles calculations, i.e., neutral-pseudoatom (NPA) calculations and
density-functional theory (DFT) with molecular-dynamics (MD) simulations, are
compared where possible with experimental data to characterize and . The NPA are
closest to the available experimental data when compared to results from
DFT+MD, where simulations of about 64-125 atoms are typically used. The
published conductivities for Li are reviewed and the value at a temperature of
4.5 eV is examined using supporting X-ray Thomson scattering calculations. A
physical picture of the variations of with temperature and density
applicable to these materials is given. The insensitivity of to
below 10 eV for carbon, compared to Al and Li, is clarified.Comment: 10 figure
A Rule-Based Approach to Analyzing Database Schema Objects with Datalog
Database schema elements such as tables, views, triggers and functions are
typically defined with many interrelationships. In order to support database
users in understanding a given schema, a rule-based approach for analyzing the
respective dependencies is proposed using Datalog expressions. We show that
many interesting properties of schema elements can be systematically determined
this way. The expressiveness of the proposed analysis is exemplarily shown with
the problem of computing induced functional dependencies for derived relations.
The propagation of functional dependencies plays an important role in data
integration and query optimization but represents an undecidable problem in
general. And yet, our rule-based analysis covers all relational operators as
well as linear recursive expressions in a systematic way showing the depth of
analysis possible by our proposal. The analysis of functional dependencies is
well-integrated in a uniform approach to analyzing dependencies between schema
elements in general.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
Level I Fieldwork Using Simulation: Student Performance Outcomes and Perceptions
The purpose of this study was to examine students’ perceptions and performance outcomes of a virtual fieldwork using Simucase® in conjunction with supplemental activities and debriefing opportunities. The simulation replaced Level I clinic-based fieldwork experiences that were cancelled due to COVID-19. Quantitative and qualitative data were collected using a modified evaluation tool to assess student performance outcomes and perceptions for students in the Year one Occupational Therapy Doctorate (OTD) cohort (n=57) and the Year two Master of Occupational Therapy (MOT) cohort (n=57) enrolled in a public university in the rural Midwest. Student ratings were compared using chi-square test of independence statistics and correlations with faculty ratings were estimated using Spearman’s correlation. Findings suggest that students performed high in most areas for six professional behaviors and five professional skills. Creswell and Creswell’s (2018) approach was used to analyze and compare student perceptions within cohorts to establish themes. Six themes were identified in students’ skill set and confidence with virtual fieldwork, and two themes were identified for ways to enhance the experience
Warm and Dry Spells (WDS) in Austral Winter over Central South America
The horizontal and vertical structure of unusually warm and dry spells (WDS) over the central parts of South America during the winter and post-winter months (JJAS) are studied. During WDS the mean temperature and humidity anomalies over central Brazil are about +4.1°C and −13.2%, respectively. The mean duration of WDS is 11 days and their mean frequency is less than one per year during the months of JJAS. Apparently, WDS have no preference for the phase of ENSO. Widespread and persistent subsidence in the middle troposphere is observed in tropical Brazil during WDS, which renders the lower tropospheric air warm and dry. The negative anomalies of the specific humidity are observed to be associated with the subsidence regions. A strong, slow moving ridge in the eastern South Pacific and a low-pressure center in northern Argentina are important surface characteristics during the WDS. A more detailed investigation of two specific WDS events, a strong event (August–September 1999) and a moderate one (June 2002), shows a blocking-like situation in the 500-hPa geopotential and surface pressure fields in the Pacific. The South Atlantic subtropical high somewhat approaches the continent. Strong northerlies over the central and eastern parts of Brazil are also observed in the lower troposphere. During WDS the regional circulation acquires summertime characteristics, except for the absence of precipitation, and the circulation in the meridional plane is in the opposite sense from the Hadley circulation. A frontal system, supported by a 500-hPa trough, advances into central Brazil, causing the dissipation of the anomalous situation
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