A low complexity DSP driven analog impairment mitigation scheme for low-IF GNSS receivers

Due to the increasing demands for location based services within the wireless mass-market; there has been relentless pressure to reduce both the chip area and power dissipation of the user terminal. Low-IF receivers combine the advantages of superheterodyne and direct-conversion architectures offering a highly integrated solution while avoiding the issues associated with DC offsets and flicker noise. The main drawback of the low-IF architecture is its limited image rejection due to analog impairments. In this paper, the sources of the impairments are analyzed for a low-IF receiver operating at the GPS/Galileo L1 band together with a novel low-complexity solution to compensate for them in the DSP domain is proposed. For processing the combined GPS/Galileo L1 signal, a signal simulator we call GNSScope has been developed together with a low-IF receiver model to analyze the influence of the analog impairments. The idea behind our proposed novel adaptive compensator which estimates and compensates for the imbalances and mismatches is that in the absence of these mismatches no correlation exists between the desired and the image channels, which is not the case when impairments are present. Results show that through the deployment of the proposed approach, image-rejection performance can be enhanced by 75 dB. This enhancement in the image-rejection performance subsequently results in relaxed analog front-end specifications leading to high levels of integration making it possible for highly integrated software-defined Global Navigation Satellite Systems (GNSS) receiver to be realistically and economically designed and implemented

Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

Cataloged from PDF version of article.We investigated the tribological interaction between polytetrafluoroethylene (PTFE) and silicon oxide surfaces. A simple rig was designed to bring about a friction between the surfaces via sliding a piece of PTFE on a thermally oxidized silicon wafer specimen. A very mild inclination (similar to 0.5 degrees) along the sliding motion was also employed in order to monitor the tribological interaction in a gradual manner as a function of increasing contact force. Additionally, some patterns were sketched on the silicon oxide surface using the PTFE tip to investigate changes produced in the hydrophobicity of the surface, where the approximate water contact angle was 45 degrees before the transfer. The nature of the transferred materials was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS results revealed that PTFE was faithfully transferred onto the silicon oxide surface upon even at the slightest contact and SEM images demonstrated that stable morphological changes could be imparted onto the surface. The minimum apparent contact pressure to realize the PTFE transfer is estimated as 5 kPa, much lower than reported previously. Stability of the patterns imparted towards many chemical washing processes lead us to postulate that the interaction is most likely to be chemical. Contact angle measurements, which were carried out to characterize and monitor the hydrophobicity of the silicon oxide surface, showed that upon PTFE transfer the hydrophobicity of the SiO2 surface could be significantly enhanced, which might also depend upon the pattern sketched onto the surface. Contact angle values above 100 degrees were obtained. (C) 2014 AIP Publishing LLC

The effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials

The temperature dependent magnetization of nanocomposite alloys has been fit with a modified Handrich-Kobe equation with an asymmetric exchange fluctuation parameter combined with the Arrott-Noakes equation. The two equations of state are combined to calculate the entropy change in the magnetocaloric effect associated with the ferromagnetic to paramagnetic phase transformation. The complete fit for the M(T) of (Fe70Ni30)88Zr7B4Cu nanocomposite powder is accomplished by combining the two theories. We investigate the broadening of the second-order transition arising from asymmetric exchange parameters and resulting from the fluctuations of interatomic spacing found in an amorphous matrix and the asymmetric dependence of exchange energy on interatomic spacing. The magnetic entropy curve revealed extra broadening with a refrigeration capacity (RC) value of 135 J/kg at 5 T, which is comparable to (Fe76Cr8-xMoxCu1B15) ribbons, which have a RC value of 180 J/kg for the same applied field. Broadening of the magnetic entropy can lead to larger RC values and a wider working temperature range, making nanocomposite alloys promising for magnetocaloric applications

A Numerical Solution to Fractional Diffusion Equation for Force-Free Case

A collocation finite element method for solving fractional diffusion equation for force-free case is considered. In this paper, we develop an approximation method based on collocation finite elements by cubic B-spline functions to solve fractional diffusion equation for force-free case formulated with Riemann-Liouville operator. Some numerical examples of interest are provided to show the accuracy of the method. A comparison between exact analytical solution and a numerical one has been made

Intensive Care of a Weil's Disease With Multiorgan Failure

Leptospirosis is a commonly encountered type of zoonosis, especially in tropical regions. There is insufficient data regarding its frequency in non-tropical regions such as Turkey. Although leptospirosis presents with a mild icteric form in nearly 90% of cases, it can lead to Weils disease characterized by fever as well as fulminant hepatorenal and respiratory failure, in approximately 5 - 10% of cases. In this case report, we present a patient with Weil's disease, complicated with multiorgan failure

Single \pi^- production in np collisions for excess energies up to 90 MeV

The quasifree reaction np\to pp\pim was studied in a kinematically complete experiment by bombarding a liquid hydrogen target with a deuteron beam of momentum 1.85 GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector $\mathbb{P}_n$ which differed from event to event. A range of almost 90 MeV excess energy above threshold was covered. Energy dependent angular distributions, invariant mass spectra as well as fully covered Dalitz plots were deduced. Sizeable $pp$ FSI effects were found as were contributions of $p$ and $d$ partial waves. The behavior of the elementary cross section $\sigma_{01}$ close to threshold is discussed in view of new cross section data. In comparison with existing literature data the results provide a sensitive test of the spectator model.Comment: 21 pages, 9 figures, 4 tables, submitted to EPJ