4,858 research outputs found
Star Formation and Gas Accretion in Nearby Galaxies
In order to quantify the relationship between gas accretion and star
formation, we analyse a sample of 29 nearby galaxies from the WHISP survey
which contains galaxies with and without evidence for recent gas accretion. We
compare combined radial profiles of FUV (GALEX) and IR 24 {\mu}m (Spitzer)
characterizing distributions of recent star formation with radial profiles of
CO (IRAM, BIMA, or CARMA) and HI (WSRT) tracing molecular and atomic gas
contents to examine star formation efficiencies in symmetric (quiescent),
asymmetric (accreting), and interacting (tidally disturbed) galaxies. In
addition, we investigate the relationship between star formation rate and HI in
the outer discs for the three groups of galaxies. We confirm the general
relationship between gas surface density and star formation surface density,
but do not find a significant difference between the three groups of galaxies.Comment: Accepted for publication in MNRAS, 18 pages, 9 figures, 1 tabl
Experimental verification and practical application of torquewhirl theory of rotordynamic instability
A theory developed by Vance in 1978 to explain the destabilizing effect of torque on a whirling rotor was experimentally verified. The measurements made on a specially designed test apparatus are described. New computer models were also developed to investigate the effect of torque on rotordynamic stability of multidisk flexible rotor bearing systems. The effect of torque was found to be most pronounced when the system is already marginally stable from other influences. The modifications required to include torque in a typical shaft transfer matrix are described, and results are shown which identify the type of rotor design most sensitive to load torque
Play materials
This chapter presents the role of play in fostering health and wellbeing in children, identifying that curriculum guidelines and policies today, in many countries, take cognisance of these important facets of development. The chapter discusses what experts, such as Laevers (1994, 2004), state about wellbeing and how his international scale on wellbeing has also been used in the Australian contexts (DECS, 2008). Other important elements of play which are central to children’s health and wellbeing are presented with timely examples of how play contexts give children the much needed opportunities to grow and play in a healthy and confident way. Issues relating to technological toys, war play, commercialisation of play materials and safety criteria for selecting toys and equipment, are also presented
Characterization of Vacuum Facility Background Gas Through Simulation and Considerations for Electric Propulsion Ground Testing
The background gas in a vacuum facility for electric propulsion ground testing is examined in detail through a series of cold flow simulations using a direct simulation Monte Carlo (DSMC) code. The focus here is on the background gas itself, its structure and characteristics, rather than assessing its interaction and impact on thruster operation. The background gas, which is often incorrectly characterized as uniform, is found to have a notable velocity within a test facility. The gas velocity has an impact on the proper measurement of pressure and the calculation of ingestion flux to a thruster. There are also considerations for best practices for tests that involve the introduction of supplemental gas flows to artificially increase the background pressure. All of these effects need to be accounted for to properly characterize the operation of electric propulsion thrusters across different ground test vacuum facilities
The Interstellar Medium and Star Formation in Edge-On Galaxies. II. NGC 4157, 4565, and 5907
We present a study of the vertical structure of the gaseous and stellar disks
in a sample of edge-on galaxies (NGC 4157, 4565, and 5907) using BIMA/CARMA
12CO (J = 1 --> 0), VLA H I, and Spitzer 3.6 micron data. In order to take into
account projection effects when we measure the disk thickness as a function of
radius, we first obtain the inclination by modeling the radio data. Using the
measurement of the disk thicknesses and the derived radial profiles of gas and
stars, we estimate the corresponding volume densities and vertical velocity
dispersions. Both stellar and gas disks have smoothly varying scale heights and
velocity dispersions, contrary to assumptions of previous studies. Using the
velocity dispersions, we find that the gravitational instability parameter Q
follows a fairly uniform profile with radius and is greater than or equal to 1
across the star forming disk. The star formation law has a slope that is
significantly different from those found in more face-on galaxy studies, both
in deprojected and pixel-by-pixel plots. Midplane gas pressure based on the
varying scale heights and velocity dispersions appears to roughly hold a
power-law correlation with the midplane volume density ratio.Comment: 26 pages, 26 figures, Accepted for publication in A
Effects of YouTube Video as Pre-Lecture Preparation
Classroom lectures convey course concepts more effectively when students have prepared in advance. Traditionally, students prepare for lectures by reading the course textbook. Textbooks are the default study material for most educational courses; however, some technical subjects are better conveyed in video format. Therefore, in this study, we encouraged students to supplement their learning resources with web-based video tutorials that provide detailed demonstrations with the respect to technical network configuration and management. YouTube is a video sharing website that can provide free educational tutorials and instructions on technical subject matter, where students can observe practical human-machine interaction to prepare for lectures and increase overall course performance on exams, assignments, and laboratory projects. Our goal was to compare the overall performance as well as the level of active class participation between two groups of the same computer networking course. We found that the group that used YouTube videos for pre-lecture preparation scored approximately 3% higher on exams but 5% lower on homework assignments than the control group (textbook only). There was no statistical significance between the two groups with respect to overall course grades. Study habits and degree of class participation of each student correlated more strongly with overall course performance than whether the student viewed the videos
Indoor Sport Facility Feasibility Study: Assessment, Value and Demand
A sport management organization proposed to build an indoor sport facility in a town close to a major urban area. The potential investors and stakeholders required that a feasibility study be conducted before an investment decision was made. The study examined the proposed facility through a traditional economic feasibility study and a market analysis to understand the market, possible future market demands, and potential growth opportunities. Included in the study are the key components and data analysis which led to a positive investment report
Next Generation Neutron Detection for Next Generation Nuclear Reactors
Track I: Power GenerationIncludes audio file (31 min.)As the demand for nuclear energy increases worldwide, and MO reactors come online, so does
the availability of spent fuel that may be used as a medium of terror. That is, fuel for and waste
or byproducts from fissile material refining and nuclear reactors (e.g. plutonium) pose a serious
threat with respect to radiological dispersal and nuclear bomb detonation. Radiological dispersal
can include fallout by means of water or atmospheric transport (e.g., dumping waste in a river)
while fissile trafficking can include the transport of plutonium across a border by seaport entry.
In order to safely increase the use of nuclear energy in Missouri, sensitive techniques for nuclear
detection must be developed. Presently available commercial detectors are not sensitive enough
to detect even large (~3kg) quantities of weapons grade plutonium that are hidden in a barrel of
water; our borders are effectively open to critical mass sized plutonium transport. Profs. Caruso,
Ching and Kruger (UMKC Physics) are developing detectors capable of a ten times increase in
detection sensitivity over existing commercial detectors that will provide a critical component to
the future Missouri nuclear safeguarding infrastructure
A New Approach for Practical Two Dimensional Data Fusion Utilizing a Single Eddy Current Probe
Interest in data fusion techniques have been growing in recent years due to the belief that a single NDE measurement may often be inadequate for providing sufficient information about the state of a test specimen. A variety of data fusion approaches have been proposed for combining results obtained by different methods, as well as different sensors, to provide comprehensive information about the material under test [1–4]. Techniques proposed to date range from blind superposition to approaches that involve the use of statistical and AI methods [5–7]
- …