4,727 research outputs found
Radiation damage in lithium-counterdoped n/p silicon solar cells
Lithium counterdoped n+/p silicon solar cells were irradiated with 1 MV electrons and their post irradiation performance and low temperature annealing properties were compared to that of the 0.35 ohm cm control cells. Cells fabricated from float zone and Czochralski grown silicon were investigated. It was found that the float zone cells exhibited superior radiation resistance compared to the control cells, while no improvement was noted for the Czochralski grown cells. Room temperature and 60 C annealing studies were conducted. The annealing was found to be a combination of first and second order kinetics for short times. It was suggested that the principal annealing mechanism was migration of lithium to a radiation induced defect with subsequent neutralization of the defect by combination with lithium. The effects of base lithium gradient were investigated. It was found that cells with negative base lithium gradients exhibited poor radiation resistance and performance compared to those with positive or no lithium gradients; the latter being preferred for overall performance and radiation resistance
Common Statistical Pitfalls in Basic Science Research
In this review, we focused on common sources of confusion and errors in the analysis and interpretation of basic science studies. The issues addressed are seen repeatedly in the authors\u27 editorial experience, and we hope this article will serve as a guide for those who may submit their basic science studies to journals that publish both clinical and basic science research. We have discussed issues related to sample size and power, study design, data analysis, and presentation of results. We then illustrated these issues using a set of examples from basic science research studies
Comparative performance of diffused junction indium phosphide solar cells
A comparison is made between indium phosphide solar cells whose p-n junctions were processed by open tube capped diffusion, and closed tube uncapped diffusion, of sulfur into Czochralski grown p-type substrates. Air mass zero, total area, efficiencies ranged from 10 to 14.2 percent, the latter value attributed to cells processed by capped diffusion. The radiation resistance of these latter cells was slightly better, under 1 MeV electron irradiation. However, rather than being process dependent, the difference in radiation resistance could be attributed to the effects of increased base dopant concentration. In agreement with previous results, both cells exhibited radiation resistance superior to that of gallium arsenide. The lowest temperature dependency of maximum power was exhibited by the cells prepared by open tube capped diffusion. Contrary to previous results, no correlation was found between open circuit voltage and the temperature dependency of Pmax. It was concluded that additional process optimization was necessary before concluding that one process was better than another
Gravitational and electroweak unification by replacing diffeomorphisms with larger group
The covariance group for general relativity, the diffeomorphisms, is replaced
by a group of coordinate transformations which contains the diffeomorphisms as
a proper subgroup. The larger group is defined by the assumption that all
observers will agree whether any given quantity is conserved. Alternatively,
and equivalently, it is defined by the assumption that all observers will agree
that the general relativistic wave equation describes the propagation of light.
Thus, the group replacement is analogous to the replacement of the Lorentz
group by the diffeomorphisms that led Einstein from special relativity to
general relativity, and is also consistent with the assumption of constant
light velocity that led him to special relativity. The enlarged covariance
group leads to a non-commutative geometry based not on a manifold, but on a
nonlocal space in which paths, rather than points, are the most primitive
invariant entities. This yields a theory which unifies the gravitational and
electroweak interactions. The theory contains no adjustable parameters, such as
those that are chosen arbitrarily in the standard model.Comment: 28 pages
Equivalence of Nonstatic Two-Pion-Exchange Nucleon-Nucleon Potentials
Off-shell aspects of the one-pion-exchange potential and their relationship
to different forms of the nonstatic (subleading-order) chiral two-pion-exchange
nucleon-nucleon potential are discussed. Various types of off-shell behavior
are categorized and numerous examples are given. Recently derived potentials
based on chiral approaches are supplemented by a rather general form of the
two-pion-exchange potential derived using old-fashioned methods. The latter is
closely related to a general form of one-pion-exchange relativistic corrections
and nonstatic two-pion-exchange three-nucleon forces developed long ago.Comment: 16 pages, latex -- Phys. Rev. C (to appear) -- Published versio
Renormalization in Nonrelativistic Quantum Mechanics
The importance and usefulness of renormalization are emphasized in
nonrelativistic quantum mechanics. The momentum space treatment of both
two-body bound state and scattering problems involving some potentials singular
at the origin exhibits ultraviolet divergence. The use of renormalization
techniques in these problems leads to finite converged results for both the
exact and perturbative solutions. The renormalization procedure is carried out
for the quantum two-body problem in different partial waves for a minimal
potential possessing only the threshold behavior and no form factors. The
renormalized perturbative and exact solutions for this problem are found to be
consistent with each other. The useful role of the renormalization group
equations for this problem is also pointed out.Comment: 16 page
A Finite Quantum Gravity Field Theory Model
We discuss the quantization of Delta gravity, a two symmetric tensors model
of gravity. This model, in Cosmology, shows accelerated expansion without a
cosmological constant. We present the transformation which
defines the geometry of the model. Then we show that all delta type models live
at one loop only. We apply this to General Relativity and we calculate the one
loop divergent part of the Effective Action showing its null contribution in
vacuum, implying a finite model. Then we proceed to study the existence of
ghosts in the model. Finally, we study the form of the finite quantum
corrections to the classical action of the model.Comment: Latex, 33 page
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