3,990 research outputs found
How much laser power can propagate through fusion plasma?
Propagation of intense laser beams is crucial for inertial confinement
fusion, which requires precise beam control to achieve the compression and
heating necessary to ignite the fusion reaction. The National Ignition Facility
(NIF), where fusion will be attempted, is now under construction. Control of
intense beam propagation may be ruined by laser beam self-focusing. We have
identified the maximum laser beam power that can propagate through fusion
plasma without significant self-focusing and have found excellent agreement
with recent experimental data, and suggest a way to increase that maximum by
appropriate choice of plasma composition with implication for NIF designs. Our
theory also leads to the prediction of anti-correlation between beam spray and
backscatter and suggests the indirect control of backscatter through
manipulation of plasma ionization state or acoustic damping.Comment: 15 pages, 4 figures, submitted to Plasma Physics and Controlled
Fusio
Effect of well-width on the electro-optical properties of a quantum well
We record photoreflectance from Ge/GeSi modulation doped quantum wells
possessing V/cm perpendicular electric fields. Qualitatively very
different spectra are obtained from samples of well-width 100 \AA and 250 \AA.
Comparing the wavefunctions calculated from an \textbf{k.p}
theory, we find that while they remain confined in the narrower 100 \AA QW, the
electric field causes them to tunnel into the forbidden gap in the 250 \AA\
well. This implies that the samples should show a transition from the quantum
confined Franz-Keldysh effect to the bulk-like Franz-Keldysh effect. Close to
the band-edge where Franz-Keldysh effects are important, simulated
photoreflectance spectra reproduce the essential features of the experiment,
without any adjustable parameters.Comment: 8 pages, 8 figures. Submitted to Phys. Rev.
Cohesion, team mental models, and collective efficacy: Towards an integrated framework of team dynamics in sport
A nomological network on team dynamics in sports consisting of a multi-framework perspective is introduced and tested. The aim was to explore the interrelationship among cohesion, team mental models (TMM), collective-efficacy (CE), and perceived performance potential (PPP). Three hundred and forty college-aged soccer players representing 17 different teams (8 female and 9 male) participated in the study. They responded to surveys on team cohesion, TMM, CE and PPP. Results are congruent with the theoretical conceptualization of a parsimonious view of team dynamics in sports. Specifically, cohesion was found to be an exogenous variable predicting both TMM and CE beliefs. TMM and CE were correlated and predicted PPP, which in turn accounted for 59% of the variance of objective performance scores as measured by teams’ season record. From a theoretical standpoint, findings resulted in a parsimonious view of team dynamics, which may represent an initial step towards clarifying the epistemological roots and nomological network of various team-level properties. From an applied standpoint, results suggest that team expertise starts with the establishment of team cohesion. Following the establishment of cohesiveness, teammates are able to advance team-related schemas and a collective sense of confidence. Limitations and key directions for future research are outlined
Gravitational Repulsion within a Black-Hole using the Stueckelberg Quantum Formalism
We wish to study an application of Stueckelberg's relativistic quantum theory
in the framework of general relativity. We study the form of the wave equation
of a massive body in the presence of a Schwarzschild gravitational field. We
treat the mathematical behavior of the wavefunction also around and beyond the
horizon (r=2M). Classically, within the horizon, the time component of the
metric becomes spacelike and distance from the origin singularity becomes
timelike, suggesting an inevitable propagation of all matter within the horizon
to a total collapse at r=0. However, the quantum description of the wave
function provides a different understanding of the behavior of matter within
the horizon. We find that a test particle can almost never be found at the
origin and is more probable to be found at the horizon. Matter outside the
horizon has a very small wave length and therefore interference effects can be
found only on a very small atomic scale. However, within the horizon, matter
becomes totally "tachionic" and is potentially "spread" over all space. Small
location uncertainties on the atomic scale become large around the horizon, and
different mass components of the wave function can therefore interfere on a
stellar scale. This interference phenomenon, where the probability of finding
matter decreases as a function of the distance from the horizon, appears as an
effective gravitational repulsion.Comment: 20 pages, 6 figure
Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study
An experimental study has been conducted to examine the interaction of compressible flow structures such as
shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure
ratios ofP4
=P1 = 4, 8, and 12 have been employed, whereP4
is the driver gas pressure andP1
is the pressure within
the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66,
respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and
driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements
were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady
and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm
Autism and the U.K. secondary school experience
This research investigated the self-reported mainstream school experiences of those diagnosed on the autistic spectrum compared with the typically developing school population. Existing literature identifies four key areas that affect the quality of the school experience for students with autism: social skills, perceived relationships with teaching staff, general school functioning, and interpersonal strengths of the young person. These areas were explored in a mainstream U.K. secondary school with 14 students with autism and 14 age and gender matched students without autism, using self-report questionnaires and semi-structured interviews. Quantitative analyses showed consistent school experiences for both groups, although content analysis of interview data highlighted some differences in the ways in which the groups perceive group work, peers, and teaching staff within school. Implications for school inclusion are discussed, drawing attention to how staff awareness of autism could improve school experience and success for students with autism attending mainstream schools
Development of Craze and Impact Resistance in Glazing Plastics by Multiaxial Stretching
The loss of strength of cast polymethyl methacrylate plastic as a result of crazing is of considerable importance to the aircraft industry. Because of the critical need for basic information on the nature of crazing and the effects of various treatments and environmental conditions on its incidence and magnitude, an investigation of this phenomenon was undertaken. The following factors were examined: (1) the effect of stress-solvent crazing on tensile strength of polymethyl methacrylate; (2) the critical stress and strain for onset of crazing at various temperatures; (3) the effect of molecular weight on crazing; and (4) the effect of multiaxial stretching on crazing of polymethyl methacrylate and other acrylic glazing materials
The Category of Node-and-Choice Forms, with Subcategories for Choice-Sequence Forms and Choice-Set Forms
The literature specifies extensive-form games in many styles, and eventually
I hope to formally translate games across those styles. Toward that end, this
paper defines , the category of node-and-choice forms. The
category's objects are extensive forms in essentially any style, and the
category's isomorphisms are made to accord with the literature's small handful
of ad hoc style equivalences.
Further, this paper develops two full subcategories: for
forms whose nodes are choice-sequences, and for forms whose
nodes are choice-sets. I show that is "isomorphically enclosed"
in in the sense that each form is isomorphic to
a form. Similarly, I show that is
isomorphically enclosed in in the sense that each
form with no-absentmindedness is isomorphic to a
form. The converses are found to be almost immediate, and the
resulting equivalences unify and simplify two ad hoc style equivalences in
Kline and Luckraz 2016 and Streufert 2019.
Aside from the larger agenda, this paper already makes three practical
contributions. Style equivalences are made easier to derive by [1] a natural
concept of isomorphic invariance and [2] the composability of isomorphic
enclosures. In addition, [3] some new consequences of equivalence are
systematically deduced.Comment: 43 pages, 9 figure
Work‐Related Outcomes After a Myocardial Infarction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90385/1/phco.24.16.1515.50946.pd
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