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Towards a Theory of Practice: Critical Transdisciplinary Multiliteracies
About the book: Education institutions and organizations throughout the world are currently being held accountable for achieving and maintaining historically unmatched standards of academic quality and performance. Accreditation bodies; policy makers; boards of trustees; and teacher, parent, and student groups all place educational institutions and organizations under unprecedented accountability pressures. The aim of this volume is to explore and better understand how these pressures are impacting a broad range of social and cultural issues and, subsequently, how these issues impact student motivation and learnin
On the Numerical Dispersion of Electromagnetic Particle-In-Cell Code : Finite Grid Instability
The Particle-In-Cell (PIC) method is widely used in relativistic particle
beam and laser plasma modeling. However, the PIC method exhibits numerical
instabilities that can render unphysical simulation results or even destroy the
simulation. For electromagnetic relativistic beam and plasma modeling, the most
relevant numerical instabilities are the finite grid instability and the
numerical Cherenkov instability. We review the numerical dispersion relation of
the electromagnetic PIC algorithm to analyze the origin of these instabilities.
We rigorously derive the faithful 3D numerical dispersion of the PIC algorithm,
and then specialize to the Yee FDTD scheme. In particular, we account for the
manner in which the PIC algorithm updates and samples the fields and
distribution function. Temporal and spatial phase factors from solving
Maxwell's equations on the Yee grid with the leapfrog scheme are also
explicitly accounted for. Numerical solutions to the electrostatic-like modes
in the 1D dispersion relation for a cold drifting plasma are obtained for
parameters of interest. In the succeeding analysis, we investigate how the
finite grid instability arises from the interaction of the numerical 1D modes
admitted in the system and their aliases. The most significant interaction is
due critically to the correct represenation of the operators in the dispersion
relation. We obtain a simple analytic expression for the peak growth rate due
to this interaction.Comment: 25 pages, 6 figure
Realization of the Large Mixing Angle Solar Neutrino Solution in an SO(10) Supersymmetric Grand Unified Model
An SO(10) supersymmetric grand unified model proposed earlier leading to the
solar solution involving ``just-so'' vacuum oscillations is reexamined to study
its ability to obtain the other possible solar solutions. It is found that all
four viable solar neutrino oscillation solutions can be achieved in the model
simply by modification of the right-handed Majorana neutrino mass matrix, M_R.
Whereas the small mixing and vacuum solutions are easily obtained with several
texture zeros in M_R, the currently-favored large mixing angle solution
requires a nearly geometric hierarchical form for M_R that leads by the seesaw
formula to a light neutrino mass matrix which has two or three texture zeros.
The form of the matrix which provides the ``fine-tuning'' necessary to achieve
the large mixing angle solution can be understood in terms of Froggatt-Nielsen
diagrams for the Dirac and right-handed Majorana neutrino mass matrices. The
solution fulfils several leptogenesis requirements which in turn can be
responsible for the baryon asymmetry in the universe.Comment: 14 pages including 2 figure
Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models
The study for lepton flavor violation combined with the neutrino oscillation
may provide more information about the lepton flavor structure of the grand
unified theory. In this paper, we study two lepton flavor violation processes,
and , in the context of supersymmetric SO(10)
grand unified models. We find the two processes are both of phenomenological
interest. In particular the latter may be important in some supersymmetric
parameter space where the former is suppressed. Thus, Z-dacay may offer another
chance for looking for lepton flavor violation.Comment: 26 pages, 10 figure
Comparisons of luminaires: Efficacies and system design
Lighting designs for architectural (aesthetic) purposes, vision and safety, and plant growth have many features in common but several crucial ones that are not. The human eye is very sensitive to the color (wavelength) of light, whereas plants are less so. There are morphological reactions, particularly to the red and blue portions of the light spectrum but, in general, plants appear to accept and use light for photosynthesis everywhere over the PAR region of the spectrum. In contrast, the human eye interprets light intensity on a logarithmic scale, making people insensitive to significant differences of light intensity. As a rough rule, light intensity must change by 30 to 50% for the human eye to recognize the difference. Plants respond much more linearly to light energy, at least at intensities below photosynthetic saturation. Thus, intensity differences not noticeable to the human eye can have significant effects on total plant growth and yield, and crop timing. These factors make luminaire selection and lighting system design particularly important when designing supplemental lighting systems for plant growth. Supplemental lighting for plant growth on the scale of commercial greenhouses is a relatively expensive undertaking. Light intensities are often much higher than required for task (vision) lighting, which increases both installation and operating costs. However, and especially in the northern regions of the United States (and Canada, Europe, etc.), supplemental lighting during winter may be necessary to produce certain crops (e.g., tomatoes) and very useful to achieve full plant growth potential and crop timing with most other greenhouse crops. Operating costs over the life of a luminaire typically will exceed the initial investment, making lighting efficacy a major consideration. This report reviews tests completed to evaluate the efficiencies of various commercially-available High-Pressure Sodium luminaires, and then describes the results of using a commercial lighting design computer program, Lumen-Micro, to explore how to place luminaires within greenhouses and plant growth chambers to achieve light (PAR) uniformity and relatively high lighting efficacies. Several suggestions are presented which could encourage systematic design of plant lighting systems
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