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Y Rahmatsamii - One of the best experts on this subject based on the ideXlab platform.
IEEE Transactions on Antennas and Propagation, 1999Co-Authors: J.m. Johnson, Y RahmatsamiiAbstract:
This paper introduces a novel technique for efficiently combining genetic algorithms (GAs) with method of moments (MoM) for integrated antenna design and explores a two example applications of the GA/MoM approach. Integral to efficient GA/MoM integration is the use of direct Z-Matrix manipulation (DMM). In DMM a "mother" structure is selected and its corresponding impedance or Z-Matrix is filled only once prior to beginning the GA optimiZation process. The GA optimiZer then optimiZes the design by creating substructures of the mother structure as represented by the corresponding subsets of the original mother Z-Matrix. Application of DMM with GA/MoM significantly reduces the total optimiZation time by eliminating multiple Z-Matrix fill operations. DMM also facilitates the use of Matrix partitioning and presolving to further reduce the optimiZation time in many practical cases. The design of a broad-band patch antenna with greater than 20% bandwidth and a dual-band patch antenna are presented as examples of the utility of GA/MoM with DMM. Measured results for the dual-band antenna are compared to numerical results. Excellent agreement between numerical and measured results is observed.
an efficient method for wide band characteriZation of periodic structures using a modified Z Matrix interpolationIEEE Antennas and Propagation Society International Symposium, 1997Co-Authors: A S Barlevy, Y RahmatsamiiAbstract:
The method of moments (MoM) is the most popular numerical technique for periodic structures such as frequency selective surfaces (FSS). The solution time for MoM in FSS applications is usually dominated by the calculation of the Z Matrix elements rather than the Matrix inversion. Therefore, reducing the time involved in calculating the Z Matrix elements can significantly reduce the total solution time. One way to reduce the calculation time of the Z Matrix elements is interpolation. The idea is to first sample the Matrix at N (usually 3) distinct frequency points, and then interpolate the Matrix elements at all other frequencies in the interpolation band. Once the Matrix is found using interpolation, the Matrix is inverted to find the induced currents, from which the scattered field can be calculated. The concept of interpolating the Z Matrix was first proposed by Newman (1988). We fine tune this technique to FSS, in order to maximiZe the accuracy over the largest possible bandwidth (as much as an 8:1 bandwidth with only 3 samples).
wide band evaluation of communications antennas using Z Matrix interpolation with the method of momentsIEEE Antennas and Propagation Society International Symposium, 1995Co-Authors: K L Virga, Y RahmatsamiiAbstract:
An important task associated with the evaluation and comparison of broadband antennas for communications applications involves performing simulations to predict the antenna performance over a wide range of frequencies. The method of moments (MoM) is one popular simulation methodology. Since the MoM impedance Matrix must be computed at each frequency, the computation over a wide frequency range can take a long time. In the paper, a method proposed by Newman  is revisited and applied to complex antenna structures being considered for modern personal communications applications. With this method, the impedance [Z] matrices for several relatively widely spaced frequencies are directly computed and stored. The elements of the impedance Matrix at an intermediate frequency are computed by interpolating the elements of the stored [Z] matrices. This method is particularly well-suited for the analysis of antennas for personal wireless applications. Such antennas are either small and low-profile or consist of thin wires. The paper presents the results of the [Z] Matrix interpolation method applied to both type of antennas; a planar inverted F antenna (PIFA) and a helix.
Sylvain Baize - One of the best experts on this subject based on the ideXlab platform.
E3 Ligase ITCH Interacts with the Z Matrix Protein of Lassa and Mopeia Viruses and Is Required for the Release of Infectious ParticlesViruses, 2020Co-Authors: Nicolas Baillet, Sophie Krieger, Xavier Carnec, Mathieu Mateo, Alexandra Journeaux, Othmann Merabet, Valérie Caro, Frédéric Tangy, Pierre-olivier Vidalain, Sylvain BaizeAbstract:
Lassa virus (LASV) and Mopeia virus (MOPV) are two closely related, rodent-born mammarenaviruses. LASV is the causative agent of Lassa fever, a deadly hemorrhagic fever endemic in West Africa, whereas MOPV is non-pathogenic in humans. The Z Matrix protein of arenaviruses is essential to virus assembly and budding by recruiting host factors, a mechanism that remains partially defined. To better characteriZe the interactions involved, a yeast two-hybrid screen was conducted using the Z proteins from LASV and MOPV as a bait. The cellular proteins ITCH and WWP1, two members of the Nedd4 family of HECT E3 ubiquitin ligases, were found to bind the Z proteins of LASV, MOPV and other arenaviruses. The PPxY late-domain motif of the Z proteins is required for the interaction with ITCH, although the E3 ubiquitin-ligase activity of ITCH is not involved in Z ubiquitination. The silencing of ITCH was shown to affect the replication of the old-world mammarenaviruses LASV, MOPV, Lymphocytic choriomeningitis virus (LCMV) and to a lesser extent Lujo virus (LUJV). More precisely, ITCH was involved in the egress of virus-like particles and the release of infectious progeny viruses. Thus, ITCH constitutes a novel interactor of LASV and MOPV Z proteins that is involved in virus assembly and release.
Guang-tsai Lei - One of the best experts on this subject based on the ideXlab platform.
Examination, Clarification, and OptimiZation of the Green's Function/ $Z$ -Matrix Models and Calculations for Rectangular Planar Microwave CircuitsIEEE Transactions on Microwave Theory and Techniques, 2011Co-Authors: Guang-tsai LeiAbstract:
In this paper, we examine the Green's function and Z-Matrix models commonly used in calculations for microwave planar circuits. We prove, for the first time, the pointwise convergence of the Green's function and the interchangeability of the integration and infinite summation used in deriving the Z-Matrix model. We also show the validity of interchanging the order of the double summation of the Z-Matrix. In a related vein, we point out some potential problem of performing series rearrangements in evaluating infinite sums. Through computational analysis, we will demonstrate that a stable and efficient algorithm for the Green's function and Z-Matrix calculations can be optimally obtained for all practical boundary port configurations of rectangular planar circuits.
H B Olaniyi - One of the best experts on this subject based on the ideXlab platform.
Applied Radiation and Isotopes, 2010Co-Authors: Felix S Olise, O K Owoade, H B OlaniyiAbstract:
Singly charged helium ((4)He(+)) induced PIXE technique was used for the elemental analysis of tin mining tailings. The procedure gave very good results especially when a correction was implemented for X-ray absorption in the low-Z region of the spectrum. The use of helium ions to induce X-ray emission was found to be adequate, especially in the case of the intermediate light elements (12<Z<21) where the nuclear reaction sensitivity decreases. Consequently, helium-induced X-ray emission analysis can be usefully applied for trace element detection of low-Z species in a higher Z Matrix as well as high-Z species in a lower Z Matrix.
Applied radiation and isotopes : including data instrumentation and methods for use in agriculture industry and medicine, 2010Co-Authors: Felix S Olise, O K Owoade, H B OlaniyiAbstract:
Singly charged helium ((4)He(+)) induced PIXE technique was used for the elemental analysis of tin mining tailings. The procedure gave very good results especially when a correction was implemented for X-ray absorption in the low-Z region of the spectrum. The use of helium ions to induce X-ray emission was found to be adequate, especially in the case of the intermediate light elements (12
K Suzuki - One of the best experts on this subject based on the ideXlab platform.
a new short bar method for 4tp admittance standards calibration by using a modified Z Matrix expression to improve signal to noise ratio s n for higher impedancesIEEE Transactions on Instrumentation and Measurement, 2009Co-Authors: K SuzukiAbstract:
This paper describes how to calibrate four-terminal-pair (4TP) admittance standards using a new short-bar method with a modified Z-Matrix expression containing a coefficient C 1 . The short-bar method is an effective way of measuring of a signal to the standard with better signal-to-noise ratio (S/N) for higher impedance standards, particularly 1 pF. This allows a 1-pF capacitor to be calibrated using direct measurement at frequencies reported for calibrations. As this method does not require the equivalent circuit for interpolation using measurements at frequencies beyond the reported frequencies, it can be applied to 4TP admittance calibration, where the 4TP sections have the same mechanical structure as lower impedance standards.
a new short bar method for 4tp admittance standards calibration by using modified Z Matrix expression to improve s n for higher impedanceConference on Precision Electromagnetic Measurements, 2008Co-Authors: K SuzukiAbstract:
This paper describes how to calibrate four-terminal-pair (4TP) admittance standards using a new short-bar method with modified Z-Matrix expression containing a correction term. The short-bar method is to measure the signal to correspond to the standard with better S/N for higher impedance standard, especially 1 pF. Therefore a 1 pF capacitor can be calibrated containing the direct measurement at reporting frequencies. As this method does not require the equivalent circuit, it can be applied to general 4TP admittance calibration.