7,497 research outputs found
Automatic PCM guard-band selector and calibrator
Automatic method for selection of proper guard band eliminates human error and speeds up calibration process. There is also an option which allows a single channel to be calibrated, independently of other channels. Entire system is designed on 3- by 4-inch printed-circuit cards and may be used with any pulse code modulation system
Processes and process development in Japan
The commercialization of solar power generation necessitates the development of low cost manufacturing method of silicon suitable for solar cells. The manufacturing methods of semiconductor grade silicon (SEG-Si) and the development of solar grade silicon (SOG-Si) in foreign countries was investigated. It was concluded that the most efficient method of developing such materials was the hydrogen reduction process of trichlorosilane (TCS), using a fluidized bed reactor. The low cost reduction of polysilicon requires cost reductions of raw materials, energy, labor, and capital. These conditions were carefully reviewed. The overall conclusion was that a development program should be based on the TCS-FBR process and that the experimental program should be conducted in test facilities capable of producing 10 tons of silicon granules per year
Collinear-to-Spiral Spin Transformation without Changing Modulation Wavelength upon Ferroelectric Transition in Tb1-xDyxMnO3
Lattice modulation and magnetic structures in magnetoelectric compounds
Tb1-xDyxMnO3 have been studied around the ferroelectric (FE) Curie temperature
T_C by x-ray and neutron diffraction. Temperature-independent modulation
vectors through T_C are observed for the compounds with 0.50< x < 0.68. This
indicates that ferroelectricity with a polarization (P) along the c axis in the
RMnO3 series cannot be ascribed to such an incommensurate-commensurate
transition of an antiferromagnetic order as was previously anticipated. Neutron
diffraction study of a single crystal with x=0.59 shows that the FE transition
is accompanied by the transformation of the Mn-spin alignment from sinusoidal
(collinear) antiferromagnetism into a transverse spiral structure. The observed
spiral structure below T_C is expected to produce P along the c axis with the
`inverse' Dzialoshinski-Moriya interaction, which is consistent with the
observation.Comment: 9 pages, 4 figure
The small-scale structure of photospheric convection retrieved by a deconvolution technique applied to Hinode/SP data
Solar granules are bright patterns surrounded by dark channels called
intergranular lanes in the solar photosphere and are a manifestation of
overshooting convection. Observational studies generally find stronger upflows
in granules and weaker downflows in intergranular lanes. This trend is,
however, inconsistent with the results of numerical simulations in which
downflows are stronger than upflows through the joint action of gravitational
acceleration/deceleration and pressure gradients. One cause of this discrepancy
is the image degradation caused by optical distortion and light diffraction and
scattering that takes place in an imaging instrument. We apply a deconvolution
technique to Hinode/SP data in an attempt to recover the original solar scene.
Our results show a significant enhancement in both, the convective upflows and
downflows, but particularly for the latter. After deconvolution, the up- and
downflows reach maximum amplitudes of -3.0 km/s and +3.0 km/s at an average
geometrical height of roughly 50 km, respectively. We found that the velocity
distributions after deconvolution match those derived from numerical
simulations. After deconvolution the net LOS velocity averaged over the whole
FOV lies close to zero as expected in a rough sense from mass balance.Comment: 32 pages, 13 figures, accepted for publication in Ap
Quantum Phase Transitions to Charge Order and Wigner Crystal Under Interplay of Lattice Commensurability and Long-Range Coulomb Interaction
Relationship among Wigner crystal, charge order and Mott insulator is studied
by the path-integral renormalization group method for two-dimensional lattices
with long-range Coulomb interaction. In contrast to Hartree-Fock results, the
solid stability drastically increases with lattice commensurability. The
transition to liquid occurs at the electron gas parameter for the
filling showing large reduction from in the continuum
limit. Correct account of quantum fluctuations are crucial to understand
charge-order stability generally observed only at simple fractional fillings
and nature of quantum liquids away from them.Comment: 4 pages including 7 figure
Reflectance measurement of two-dimensional photonic crystal nanocavities with embedded quantum dots
The spectra of two-dimensional photonic crystal slab nanocavities with
embedded InAs quantum dots are measured by photoluminescence and reflectance.
In comparing the spectra taken by these two different methods, consistency with
the nanocavities' resonant wavelengths is found. Furthermore, it is shown that
the reflectance method can measure both active and passive cavities. Q-factors
of nanocavities, whose resonant wavelengths range from 1280 to 1620 nm, are
measured by the reflectance method in cross polarization. Experimentally,
Q-factors decrease for longer wavelengths and the intensity, reflected by the
nanocavities on resonance, becomes minimal around 1370 nm. The trend of the
Q-factors is explained by the change of the slab thickness relative to the
resonant wavelength, showing a good agreement between theory and experiment.
The trend of reflected intensity by the nanocavities on resonance can be
understood as effects that originate from the PC slab and the underlying air
cladding thickness. In addition to three dimensional finite-difference
time-domain calculations, an analytical model is introduced that is able to
reproduce the wavelength dependence of the reflected intensity observed in the
experiment.Comment: 24 pages, 7 figures, corrected+full versio
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