692,575 research outputs found
Codes Cross-Correlation Impact on S-curve Bias and Data-Pilot Code Pairs Optimization for CBOC Signals
The aim of this paper is to analyze the impact of spreading codes cross-correlation on code tracking performance, and to optimize the data-pilot code pairs of Galileo E1 Open Service (OS) Composite Binary Offset Carrier (CBOC) signals. The distortion of the discriminator function (i.e., S-curve), due to data and pilot spreading codes cross-correlation properties, is evaluated when only the data or pilot components of CBOC signals are tracked, considering the features of the modulation schemes. Analyses show that the S-curve bias also depends on the receiver configuration (e.g., the tracking algorithm and correlator spacing). In this paper, two methods are proposed to optimize the data-pilot code pairs of Galileo E1 OS. The optimization goal is to obtain minimum average S-curve biases when tracking only the pilot components of CBOC signals for the specific correlator spacing. The S-curve biases after optimization processes are analyzed and compared with the un-optimized results. It is shown that the optimized data-pilot code pairs could significantly mitigate the intra-channel (i.e., data and pilot) codes cross-correlation,and then improve the code tracking performance of CBOC signals
Deposition of ZnO-Al (AZO) thin films for optical properties
Zinc Oxide (ZnO) is an inorganic compound and it is doped with aluminum to increase its capabilities.
Aluminum Zinc Oxide (AZO) thin films are semiconductor materials that have band gap energy of 3.3eV. Various method
of deposition have been study to growth AZO thin films. It has been extensively use in solar cell application, display
application, gas sensing purposes, and thin film transistors (TFTs). In this work, sol gel method and spin coating was used
to deposited AZO thin films. The ZnO sol-gel were synthesized using zinc acetate dihydrate as precursor, isopropanol as
solvent, diethanolamine as sol stabilizer, and distilled water as oxidation agent. Then, synthesized ZnO were doped with
different mole ratio of aluminum nitrate nanohydrate to produced AZO. The glass substrate was used as substrate and AZO
thin films were then calcinated at 300°C and 500°C. The characterization of AZO thin film were done using X-ray
Diffraction (XRD), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-Vis), Field Emission
Scanning Electron Microscope (FESEM), and Energy Dispersive X-ray spectroscopy (EDX). The XRD results show that
the ZnO with hexagonal wurtzite-type structure and temperature does have effect on the film intensity which related to
crystallinity of thin films. Through AFM analysis, the value of RMS decreases from 3.018 nm to 2.240 nm as the
temperature increases. Meanwhile, from UV-Vis result, it can be seen that AZO thin film have a high transmittance
percentage above 90% after wavelength 400 nm with band gap value of 3.3 eV. FESEM image show that the grain boundary
of AZO decrease with both parameter (mole ratio and calcinations temperature). Both parameters do have effect on AZO
thin film. EDX analysis shows that there are existence of zinc, oxide, and aluminum
Bond-order wave phase, spin solitons and thermodynamics of a frustrated linear spin-1/2 Heisenberg antiferromagnet
The linear spin-1/2 Heisenberg antiferromagnet with exchanges ,
between first and second neighbors has a bond-order wave (BOW) phase that
starts at the fluid-dimer transition at and is particularly
simple at . The BOW phase has a doubly degenerate singlet ground
state, broken inversion symmetry and a finite energy gap to the lowest
triplet state.
The interval has large and small finite size
corrections. Exact solutions are presented up to spins with either
periodic or open boundary conditions and for thermodynamics up to . The
elementary excitations of the BOW phase with large are topological
spin-1/2 solitons that separate BOWs with opposite phase in a regular array of
spins. The molar spin susceptibility is exponentially small for and increases nearly linearly with to a broad maximum. ,
spin chains approximate the magnetic properties of the BOW phase of
Hubbard-type models and provide a starting point for modeling alkali-TCNQ
salts.Comment: 10 pages, 12 figure
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