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  • 1
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    Performance Analysis of the Korean Positioning System Using Observation Simulation (2020)
    In:  Remote Sensing
    Details
    Publication Date: 2021-01-18
    Description: The Korean government has a plan to build a new regional satellite navigation system called the Korean Positioning System (KPS). The initial KPS constellation is designed to consist of seven satellites, which include three geostationary Earth orbit (GEO) satellites and four inclined geosynchronous orbit (IGSO) satellites. KPS will provide an independent positioning, navigation, and timing (PNT) service in the Asia-Oceania region and can also be compatible with GPS. In the simulation for KPS, we employ 24 GPS as designed initially and 7 KPS satellites. Compared to the true orbit that we simulated, the averaged root mean square (RMS) values of orbit-only signal-in-space ranging errors (SISRE) are approximately 4.3 and 3.9 cm for KPS GEO and IGSO. Two different positioning solutions are analyzed to demonstrate the KPS performance. KPS standard point positioning (SPP) errors in the service area are about 4.7, 3.9, and 7.1 m for east (E), north (N), and up (U) components, respectively. The combined KPS+GPS SPP accuracy can be improved by 25.0%, 31.8%, and 35.0% compared to GPS in E, N, and U components. The averaged position errors for KPS kinematic precise point positioning (KPPP) are less than 10 cm. In the fringe of the KPS service area, however, the position RMS errors can reach about 40 cm. Unlike KPS, GPS solutions show high positioning accuracy in the KPS service area. The combined KPS+GPS can be improved by 28.7%, 27.1%, and 30.5% compared to GPS in E, N, and U components, respectively. It is noted that KPS can provide better performance with GPS in the Asia-Oceania region.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Charge Transport of Hydrochloric Acid Doped Polyaniline and Poly(o-toluidine) Fibers: Role of Processing (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 5871-5876 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00098a047
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  • 3
    Electronic Resource
    Electronic Resource
    Anomalous charge transport phenomena in molecular-based magnet V(TCNE)x⋅y(solvent) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6566-6568 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present charge transport studies on recently developed molecular-based magnets V(TCNE)x⋅y(solvent) (TCNE=tetracyanoethylene) which show local magnetic ordering at temperatures, T, as high as 400 K. V(TCNE)x⋅y(solvent) prepared from the solvent CH2Cl2 has σ(300 K)∼10−3 S/cm, and that prepared from the solvent CH3CN has σ(300 K)∼10−5 S/cm. The σ(T) of both materials follows the Mott 3D variable range hopping [log(T1/2σ)∝T−1/4] behavior. An anomalously strong T-dependent ac conductivity is likely caused by the short-range ferrimagnetic correlations. Cole–Cole analysis of the ac complex dielectric constant suggests there are two relaxation mechanisms, with an Arrhenius relation fitted to both. The microwave frequency response is consistent with audio frequency data and yields a localization length of ∼ 5 A(ring), comparable with the dimensions of a [TCNE]−. group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352565
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple stellar populations in the globular cluster ω Centauri as tracers of a merger event (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 402 (1999), S. 55-57 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The discovery of the Sagittarius dwarf galaxy, which is being tidally disrupted by and merging with the Milky Way, supports the view that the halo of the Galaxy has been built up at least partially by the accretion of similar dwarf systems. The Sagittarius dwarf contains several distinct ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/46985
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  • 5
    Electronic Resource
    Electronic Resource
    Electromagnetic radiation shielding by intrinsically conducting polymers (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2278-2280 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shielding efficiency of various intrinsically conducting polymers (ICPs) as a function of their intrinsic properties (conductivity and dielectric constant), thickness, and temperature is determined. Two types of shielding, reflection and absorption, by ICPs are discussed. The high shielding efficiencies of highly conducting doped polyaniline, polypyrrole, and polyacetylene are reported and compared to that of copper. The easy tuning of intrinsic properties by chemical processing suggests the wide applications of ICPs, especially polyaniline for shielding. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112717
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of silver solubility on microstructure and superconducting properties of YBa2Cu3−xAgxO7−δ superconductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2351-2355 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of silver (Ag) solubility on microstructure and superconducting properties of YBa2Cu3−xAgxO7−δ (0≤x≤0.5) superconductors has been evaluated. The solubility limit of Ag for copper sites in YBCO at ambient conditions (room temperature, atmospheric pressure) was evaluated to be x(approximately-equal-to)0.06. Analysis revealed the Ag content (x) of YBCO grains to be lower than the nominal Ag content (xn) used for fabrication, probably due to processing-related problems. Part of the Ag used for fabrication segregates on the YBCO grain boundaries. The segregated Ag particles are believed to pin YBCO grains, resulting in fine-grain microstructures. For low nominal Ag content, xn〈0.2, critical current density (Jc) increased from 98 to 160 A/cm2 as a function of increasing Ag content. These improvements are believed to be due to the increased oxygen content and associated microstructural changes in the YBCO. For higher nominal Ag content, xn(approximately-greater-than)0.2, however, Jc decreased rapidly with the increasing Ag content due to the precipitation of nonsuperconducting phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351088
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  • 7
    Electronic Resource
    Electronic Resource
    Complex dielectric constant measurement of samples of various cross sections using a microwave impedance bridge (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2653-2657 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microwave impedance bridge covering from 8.2 to 12.4 GHz used for measuring complex dielectric constants over a wide temperature range is described. This apparatus is suited for materials formed into solid posts having different cross sections. The effective diameters for use in the analysis of circular, elliptical, or rectangular cross-section posts are presented. The effective diameters are applied to determine the complex dielectric constant of rectangular-shaped conducting polymer film. The frequency and temperature dependence of the dielectric constant and conductivity are presented, and compared with those obtained using a microwave cavity perturbation technique at 6.5 GHz. The bridge results are well suited for independent determination of the depolarization factor of a rectangular post for use in analysis of results of the cavity perturbation method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144665
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  • 8
    Electronic Resource
    Electronic Resource
    High frequency electromagnetic interference shielding response of mixtures and multilayer films based on conducting polymers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 513-518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electromagnetic interference (EMI) shielding efficiency (SE) is measured for conductive polyaniline and its mixtures containing conducting powders. The frequency ranges of the EMI SE is 10 MHz–1 GHz by using the ASTM D4935-89 technique. The EMI SE of hydrochloric acid doped polyaniline containing silver (Ag) powder is ∼46 dB at room temperature, which indicates that the materials can be commercially applied to shielding against electromagnetic (EM) radiation. The theoretical SE is calculated by using measured dc conductivity, which is compared to the experimental data. We observe that the SE increases with increasing dc conductivity. A model to account for the increase of the SE through the chemical doping and mixing process is presented. The theory for the calculation of the EMI SE of multilayer films based on conducting polymers is discussed in terms of boundary conditions for electric and magnetic fields of EM plane waves. The high frequency (≥300 MHz) EMI shielding response of the monolayer and multilayer films with the same thickness is theoretically compared. The frequency dependence of SE of monolayer films shows a constant behavior at low frequency and an oscillating behavior with a single period at high frequency. The SE of multilayer films, consisting of the high H and low L conducting layers with the same thickness as that of monolayer films in total, shows a constant behavior at low frequency (≤10 GHz) and an oscillating behavior with two major periods at high frequency (〉10 GHz). The SE of H–L–H layers is smaller than that of H–H–H layers at low frequency. However, there exist frequency ranges where the SE of H–L–H layers is larger than that of H–H–H layers (for example, from 35–70 GHz). The result suggests that the coherent multiple reflections at the internal interfaces of H–L–H layers contribute to an increase of SE. We observe that the effect of coherent multiple reflections decreases as the thickness of the layer increases. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373688
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  • 9
    Electronic Resource
    Electronic Resource
    Simulation of three-point bending at large deflections by an elastoplastic contact analysis (1989)
    Springer
    Experimental mechanics 29 (1989), S. 460-465 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Three-point bending is simulated by an elaborate numerical procedure based on an elastoplastic, large deflection, contact analysis. A minimization formulation is used, which is equivalent to the incremental form posed as partial differential equations with inequalities. A sequential quadratic programming approach based on the finite-element technique is adopted as a method of solution. To examine the validity of the simulation method, experiments are carried out for specimens that have various widths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02323868
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of residence time distribution in the extrusion process including the effect of 3-D circulatory flow (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 959-970 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is of great importance to accurately measure or predict the Residence Time Distribution (RTD) in designing extruders and/or in setting up a proper operating condition, because chemical reactions depend significantly on the RTD and temperature when chemical reactions take place during the extrusion process. A previous method to predict the RTD can analytically determine RTD, Residence Time Distribution Function f(t) and Cumulative Residence Time Distribution Function F(t), based on a simplified two-dimensional velocity field in an extruder. However, this previous method cannot accurately take into account the three-dimensional circulatory flow inside the extruder. The present paper suggests a new method to accurately determine the RTD taking into account the three-dimensional circulatory flow and presents a new formula derived to calculate f(t). In order to demonstrate the applicability of the new method including the circulatory flow effect, RTD, f(t) and F(t) were calculated based on a three-dimensional velocity field obtained via a quasi-three-dimensional finite element analysis. It was found that the previous method has a tendency to underestimate the RTD, owing to the neglect of the three-dimensional circulatory flow in comparison with the new method.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760331505
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