379 research outputs found
Correctness of Velocity Evaluation of System Using Spatial Filter
In this paper, a velocity measurement method using the spatial filter is presented. Luminous emitance of the surface passing through the moving spatial filter and optical set is projected to the active area of photo-detector. The velocity determination is based on the frequency spectrum evaluation of the photo-detector output signal. The formula for velocity computing is derived first. Then, correctness of velocity evaluation in dependence on the surface and measuring system properties is discussed
Simplified Frame and Symbol Synchronization for 4–CPFSK with h=0.25
This paper examines the problem of rapid frame and symbol synchronization techniques intended particularly for constant envelope modulation formats M–CPFSK with modulation index h=1/M which are used in strictly bandwidth limited narrowband industrial applications. The data aided and non data aided versions of the algorithm based on digital frequency discrimination are discussed and compared against the synchronization techniques found in literature. Sample wise pattern correlation technique for joint frame and symbol synchronization is also studied. With the focus on a practical digital implementation the advantages and disadvantages of the described approaches are discussed
Implementation of Industrial Narrow Band Communication System into SDR Concept
The rapid expansion of the digital signal processing has penetrated recently into a sphere of high performance industrial narrow band communication systems which had been for long years dominated by the traditional analog circuit design. Although it brings new potential to even increase the efficiency of the radio channel usage it also forces new challenges and compromises radio designers have to face. In this article we describe the design of the IF sampling industrial narrowband radio receiver, optimize a digital receiver structure implemented in a single FPGA circuit and study the performance of such radio receiver architecture. As an evaluation criterion the communication efficiency in form of maximum usable receiver sensitivity, co-channel rejection, adjacent channel selectivity and radio blocking measurement have been selected
Valence modulations in CeRuSn
CeRuSn exhibits an extraordinary room temperature structure at 300~K with
coexistence of two types of Ce ions, namely trivalent Ce and
intermediate valent Ce, in a metallic environment. The ordered
arrangement of these two Ce types on specific crystallographic sites results in
a doubling of the unit cell along the -axis with respect to the basic
monoclinic CeCoAl-type structure. Below room temperature, structural modulation
transitions with very broad hysteresis have been reported from measurements of
various bulk properties. X-ray diffraction revealed that at low temperatures
the doubling of the CeCoAl type structure is replaced by a different modulated
ground state, approximating a near tripling of the basic CeCoAl cell. The
transition is accompanied by a significant contraction of the axis. We
present new x-ray absorption near-edge spectroscopy data at the Ce L
absorption edge, measured on a freshly cleaved surface of a CeRuSn single
crystal. In contrast to a previous report, the new data exhibit small but
significant variations as function of temperature that are consistent with a
transition of a fraction of Ce ions to the intermediate valence state,
analogous to the transition in elemental cerium,
when cooling through the structural transitions of CeRuSn. Such results in a
valence-modulated state
Field-Induced Magnetic and Structural Domain Alignment in PrO2
We present a neutron diffraction study of the magnetic structure of single
crystal PrO2 under applied fields of 0-6 T. As the field is increased, changes
are observed in the magnetic Bragg intensities. These changes are found to be
irreversible when the field is reduced, but the original intensities can be
recovered by heating to T > 122 K, then re-cooling in zero field. The
antiferromagnetic ordering temperature TN = 13.5 K and the magnetic periodicity
are unaffected by the applied field. We also report measurements of the
magnetic susceptibility of single crystal PrO2 under applied fields of 0-7 T.
These show strong anisotropy, as well as an anomaly at T = 122 +/- 2 K which
coincides with the temperature TD = 120 +/- 2 K at which a structural
distortion occurs. For fields applied along the [100] direction the
susceptibility increases irreversibly with field in the temperature range TN <
T < TD. However, for fields along [110] the susceptibility is independent of
field in this range. We propose structural domain alignment, which strongly
influences the formation of magnetic domains below TN, as the mechanism behind
these changes.Comment: 11 pages, 13 figures, 5 tables. Minor typographical changes in v
Low-coordinate iridium NHC complexes derived from selective and reversible C–H bond activation of fluoroarenes
Interaction of the reactive 14 VE {Ir(IBioxMe4)3}+ fragment with fluoroarenes results exclusively in ortho-C–H bond oxidative addition and formation of 16 VE Ir(III) derivatives [Ir(IBioxMe4)3(Ar)H]+ (Ar = 2-C6H4F, 2,3-C6H3F2, 2,4,6-C6H2F3). The C–H bond activation reactions occur under mild conditions and are reversible
Field-induced commensurate long-range order in the Haldane-gap system NDMAZ
High-field neutron diffraction studies of the new quantum-disordered S=1
linear-chain antiferromagnet Ni(CHN)N(ClO) (NDMAZ)
are reported. At T=70 mK, at a critical field T applied along the
(013) direction, a phase transition to a commensurate N\'{e}el-like ordered
state is observed. The results are discussed in the context of existing
theories of quantum phase transitions in Haldane-gap antiferromagnets, and in
comparions with previous studies of the related system
Ni(CHN)N(PF)
Biophysical characterization of a protein for structure comparison : methods for identifying insulin structural changes
Although protein structure has been studied for many decades it remains the case that we cannot state with confidence whether two samples have the same molecular structure, particularly in solution. The increasing number of biosimilar biopharmaceutical drugs that are being tested means this is not an academic exercise. In this work we consider how four well-established techniques: dynamic light scattering (DLS), circular dichroism (CD), nuclear magnetic resonance spectroscopy (NMR), and molecular modelling can be combined to provide information about the supposedly well-understood protein insulin. A goal of this work was to establish a systematic means of detecting differences between insulin samples as a function of pH, temperature, and the presence or absence of zinc, all of which are known to change the oligomerisation state and to affect molecular structure. We used the recently developed Secondary Structure Neural Network (SSNN) circular dichroism algorithm to facilitate analysis of the CD spectra
Communication Subsystems for Emerging Wireless Technologies
The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels
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