239,886 research outputs found
Optimal Lattice-Reduction Aided Successive Interference Cancellation for MIMO Systems
In this letter, we investigated the optimal minimummean-squared-error (MMSE) based successive interference cancellation (SIC) strategy designed for lattice-reduction aided multiple-input multiple-output (MIMO) detectors. For the sake of generating the MMSE-based MIMO symbol estimate at each SIC detection stage, we model the so-called effective symbols generated with the aid of lattice-reduction as joint Gaussian distributed random variables. However, after lattice-reduction, the effective symbols become correlated and exhibit a non-zero mean. Hence, we derive the optimal MMSE SIC detector, which updates the mean and variance of the effective symbols at each SIC detection stage. As a result, the proposed detector achieves a better performance compared to its counterpart dispensing with updating the mean and variance, and performs close to the maximum likelihood detector. Index Terms—Lattice-reduction, multiple antennas, MIMO, symbol detection, SIC detector
Computation of topside ionograms from N/h/ profiles
Computation of topside ionograms from electron concentration profile
An evaluation of multiband photography for rock discrimination
The author has identified the following significant results. With the advent of ERTS and Skylab satellites, multiband imagery and photography have become readily available to geologists. The ability of multiband photography to discriminate sedimentary rocks was examined. More than 8600 in situ measurements of band reflectance of the sedimentary rocks of the Front Range, Colorado, were acquired. Statistical analysis of these measurements showed that: (1) measurements from one site can be used at another site 100 miles away; (2) there is basically only one spectral reflectance curve for these rocks, with constant amplitude differences between the curves; and (3) the natural variation is so large that at least 150 measurements per formation are required to select best filters. These conclusions are supported by subjective tests with aerial multiband photography. The designed multiband photography concept for rock discrimination is not a practical method of improving sedimentary rock discrimination capabilities
Microscopic picture of aging in SiO2
We investigate the aging dynamics of amorphous SiO2 via molecular dynamics
simulations of a quench from a high temperature T_i to a lower temperature T_f.
We obtain a microscopic picture of aging dynamics by analyzing single particle
trajectories, identifying jump events when a particle escapes the cage formed
by its neighbors, and by determining how these jumps depend on the waiting time
t_w, the time elapsed since the temperature quench to T_f. We find that the
only t_w-dependent microscopic quantity is the number of jumping particles per
unit time, which decreases with age. Similar to previous studies for fragile
glass formers, we show here for the strong glass former SiO2 that neither the
distribution of jump lengths nor the distribution of times spent in the cage
are t_w-dependent. We conclude that the microscopic aging dynamics is
surprisingly similar for fragile and strong glass formers.Comment: 4 pages, 7 figure
Photoreceptors for a light biotransducer: a comparative study of the electrical responses of two (type-1)-opsins
The increasing interest in photoactivated proteins as natural replacement of
standard inorganic materials in photocells drives to the compared analysis of
bacteriorhodopsin and proteorhodopsin, two widely diffused proteins belonging
to the family of \textit{type-1} opsins. These proteins share similar
behaviours but exhibit relevant differences in the sequential chain of the
amino acids constituting their tertiary structure. The use of an impedance
network analogue to model the protein main features provides a microscopic
interpretation of a set of experiments on their photoconductance properties. In
particular, this model links the protein electrical responses to the tertiary
structure and to the interactions among neighbouring amino acids. The same
model is also used to predict the small-signal response in terms of the Nyquist
plot. Interesting enough, these rhodopsins are found to behave like a wide gap
semiconductor with intrinsic conductivities of the order of S/cm.Comment: 19 pages, 15 figure
Evolution of quantum systems with a scaling type of time-dependent Hamiltonians
We introduce a new class of quantum models with time-dependent Hamiltonians
of a special scaling form. By using a couple of time-dependent unitary
transformations, the time evolution of these models is expressed in terms of
related systems with time-independent Hamiltonians. The mapping of dynamics can
be performed in any dimension, for an arbitrary number of interacting particles
and for any type of the scaling interaction potential. The exact solvability of
a "dual" time-independent Hamiltonian automatically means the exact solvability
of the original problem with model time-dependence.Comment: 9 page
Model verification of large structural systems
A methodology was formulated, and a general computer code implemented for processing sinusoidal vibration test data to simultaneously make adjustments to a prior mathematical model of a large structural system, and resolve measured response data to obtain a set of orthogonal modes representative of the test model. The derivation of estimator equations is shown along with example problems. A method for improving the prior analytic model is included
Grid generation strategies for turbomachinery configurations
Turbomachinery flow fields involve unique grid generation issues due to their geometrical and physical characteristics. Several strategic approaches are discussed to generate quality grids. The grid quality is further enhanced through blending and adapting. Grid blending smooths the grids locally through averaging and diffusion operators. Grid adaptation redistributes the grid points based on a grid quality assessment. These methods are demonstrated with several examples
An underground cosmic ray muon telescope for observation of cosmic ray anisotropy
A telescope housed in a tunnel laboratory has an overburden of 573 hg cm(-2) and is located under the center of a saddle-shaped landscape. It is composed of triple layers of proportional counters, each layer of area approx. 4m x 2m and their separation 0.5m. Events are selected by triple coincidence and software track identification. The telescope is in operation for over a year and the overall count rate is 1280 hr(-1). The structure and operation of the system is reported
MAG3D and its application to internal flowfield analysis
MAG3D (multiblock adaptive grid, 3D) is a 3D solution-adaptive grid generation code which redistributes grid points to improve the accuracy of a flow solution without increasing the number of grid points. The code is applicable to structured grids with a multiblock topology. It is independent of the original grid generator and the flow solver. The code uses the coordinates of an initial grid and the flow solution interpolated onto the new grid. MAG3D uses a numerical mapping and potential theory to modify the grid distribution based on properties of the flow solution on the initial grid. The adaptation technique is discussed, and the capability of MAG3D is demonstrated with several internal flow examples. Advantages of using solution-adaptive grids are also shown by comparing flow solutions on adaptive grids with those on initial grids
- …