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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Wireless personal communications 4 (1997), S. 277-298 
    ISSN: 1572-834X
    Keywords: Land Mobile Satellite Communications ; channel modeling ; diversity reception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Land mobile satellite communication systems at Ka/K band (30/20 GHz) are attracting more and more attention to researchers because of its frequency band availability and the possibility of using small earth stations and satellite antennas for the systems. However, the Ka/K-band communications also give significant challenges in the system design due to severe channel impairments expected from the satellite links. In this paper, K-band channel characteristics are studied and compared with those at L band. The channel is modeled as Rayleigh multipath fading with the line-of-sight (LOS) component following a lognormal distribution. The first and second-order statistics of the fading channel are studied. Dual-space diversity reception is investigated to combat the flat channel fading. The bit error rate performance of coherent binary phase shift keying (BPSK) with ideal bit and carrier phase synchronization over the fading channel at K band is evaluated theoretically and verified by computer simulations in the case with and without diversity reception.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 233-236 (Jan. 2003), p. 809-814 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 60 (1995), S. 601-606 
    ISSN: 1432-0630
    Keywords: PACS: 82.40.Tc; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ and X band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 60 (1995), S. 601-606 
    ISSN: 1432-0630
    Keywords: 82.40.Tc ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 16 (1995), S. S127 
    ISSN: 1572-8986
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Numerical modeling and experimental measurements have been performed to study the effects of powder carrier gas flow rates and powder sizes on the deposition offset in a plasma spray of yttria-stablized zirconia. The mathematical model involved simultaneous solution of the continuity, momentum and energy equations of the plasma gas, the dynamics and heat transfer of powder particles in the plasma, and the coupling effects between the plasma and panicles. Experiments included measurement of particle velocities by laser strobe technique and measurement of deposition offset. Calculated plasma temperatures and velocities are greater than 13,000 K and 2,000 m/s, respectively, in the vicinity of nozzle exit. For the plasma-particle momentum transfer, the drag coefficient was computed in two ways- with corrections accounting for the strongly varying plasma properties, and without these corrections. Calculated and experimental results, in respect to deposition offset, are in agreement to within 25% when calculated without varying properties corrections, and within about 40% with corrections; agreement in respect to average particle velocities is within 20% when calculated without varying properties corrections, and within the range 30–50% with corrections.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Acta applicandae mathematicae 39 (1995), S. 361-378 
    ISSN: 1572-9036
    Keywords: Primary 35Q51, 35Q53, 35C05, 68Q40 ; Secondary 34-04, 35-04 ; soliton theory ; symbolic programs ; Hirota method ; Painlevé test ; Lie symmetries ; conserved densities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Four symbolic programs, in Macsyma or Mathematica language, are presented. The first program tests forthe existence of solitons for nonlinear PDEs. It explicitly constructs solitons using Hirota's bilinear method. In the second program, the Painlevé integrability test for ODEs and PDEs is implemented. The third program provides an algorithm to compute conserved densities for nonlinear evolution equations. The fourth software package aids in the computation of Lie symmetries of systems of differential and difference-differential equations. Several examples illustrate the capabilities of the software.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modified self-consistent phonon theory when applied to the DNA double helix indicates the existence of fairly long-lived states in which single interbase H bonds are disrupted. One can then postulate a number of situations in which particular disrupted H bonds can enhance particular proton exchange. In this paper we postulate a number of such partially open states for a B-conformation GC base pair and calculate the probability of each of these states for a B-conformation poly(dG) · poly(dC). We compare these probabilities to those probabilities needed to explain various observed proton exchange rates. We propose that, for a GC base pair in B conformation, there are two amino proton exchangeable states - a cytosine amino proton exchangeable state and a guanine amino proton exchangeable state; both require the disruption of only the corresponding inter base H bond. The imino proton exchange, however, requires the disruption of all three inter base H bonds and this defines a third open state. Our calculated probabilities for a GC base pair in these three states are in fair agreement with available experimental estimates from measurements of amino and imino proton exchange.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 86 (1984), S. 121-124 
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Phytophthora spp. associated with leaf fall, stem canker and black stripe of rubbertree (Hevea brasiliensis Muell.-Arg.) in Xishuangbanna of Yunnan Province were isolated from leaves, bark, fruit and soil in the plantations. Of a total of 50 isolates, 42 were designated as P. citrophthora (R. E. Sm. & E. H. Sm.) Leonian, while the others were identified as P. palmivora (Butl.) Butl., P. colocasiae Rac. and P. cactorum (Leb. & Conn) Schroet. This appears to be the first report of P. citrophthora on Hevea brasiliensis.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1123-1127 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 59-63 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Current in vitro biocompatibility methods do not evaluate the degradation of biomaterials after contact with enzymes that might be present in the oral or systemic environment. In this study, two methods of in vitro enzyme degradation and a method for the separation of the degradative products by high performance thinlayer chromatography (HPTLC) are reported. In the first method two dental adhesives, Scotchbond and Scotchbond II, and two dental composites, Helimolar and P-50, were evaluated. These materials were incubated with four different enzymatic preparations for periods of up to 72 h. The enzymes were lipase, esterase, and liver enzyme extracts from both mouse and rat. Chloroform soluble products extracted from the aqueous phase were examined by HPTLC for decomposition products resulting from enzyme activity. The second method was similar, but analyzed the aqueous fraction directly without chloroform extraction. In this method five dental restorative materials, P-50, P-30, Scotochbond II, Silux, and Silux Plus, were incubated with a nonspecific porcine liver esterase. In addition to the polymerized biomaterials. Monomers containing methacrylic acid units were also hydrolyzed with esterase and analyzed by ion chromatography to establish the sensitivity of the enzyme simulator. Each biomaterial presented thin-layer zones not present before enzymatic action. These experiments provide support that aqueous enzymatic action may facilitate the hydrolytic weakening of polymeric biomaterials. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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