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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Injected Water on Hydraulic Fracturing Deduced from Acoustic Emission Monitoring (1997)
    Springer
    Pure and applied geophysics 150 (1997), S. 627-646 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Hydraulic fracturing, acoustic emission, fault plane solution, fracturing mechanism.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. —In order to investigate the effects of injected water in hydraulic fracturing, experiments were conducted on cubic granite specimens, comparing fracturings induced by conventional water injection with those induced by pressurization of a urethane sleeve, thereby realizing "hydraulic fracturing" without the use of fracturing fluid. In both experiments, a shear type mechanism was found to be dominant in fault plane solutions of AE events. However, in the case of water injection, cracks extended rapidly with large drops in hole water pressure and bursts of AE, whereas in pressurization by the urethane sleeve, cracks extended stepwise with no such large drops in hole pressure and no bursts of AE. The difference in crack extension in the two experiments can be analyzed by comparing relations between crack length and stress intensity factor of mode I at a crack tip. The observation and analysis indicate that existence of fracturing fluid like water helps initiated cracks to extend rapidly and widely in hydraulic fracturing in actual HDR fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050096
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  • 2
    Electronic Resource
    Electronic Resource
    Swirling flows in circular-to-rectangular transition ducts (1996)
    Springer
    Experiments in fluids 20 (1996), S. 401-409 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Swirling flows in three circular-to-rectangular transition ducts, each of them with an aspect ratio of 2.0 at the rectangular exit, have been studied experimentally. The swirling flows were produced by swirlers whose vane angles were at 5°, 10° and 20° inclinded to the incoming flow, respectively. Flow visualization experiments were made at selected cross-sectional planes in the transition ducts. Pressure and velocity measurements were obtained on the contoured duct walls and at the rectangular exit planes, respectively. The results show that the swirling flow pattern evolves into a skewed structure at the exit plane which, in connection with the wall pressure distributions, is asymmetric with respect to the centerline of either the top and bottom walls or the side walls. Moreover, an analysis based on the mean streamwise vorticity equation with the velocity data obtained immediately downstream of the rectangular exit plane indicates that the cross-stream Reynolds stress plays an important role in transporting the streamwise vorticity of the swirling flow into the surrounding fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189378
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  • 3
    Electronic Resource
    Electronic Resource
    Raman-spectroscopy study of PbTiO3 thin films grown on Si substrates by metalorganic chemical vapor deposition (1996)
    Springer
    Applied physics 62 (1996), S. 281-284 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.30.Hv; 63.20. ; e; 81.15.Gh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Raman spectra have been investigated in PbTiO3 thin films grown on Si by metalorganic chemical vapor deposition. A large grazing-angle scattering technique was taken to measure the temperature dependence of Raman spectra below room temperature. All Raman modes in the thin films are assigned and compared with those in the bulk single crystal, a new A 1(TO) soft mode at 104 cm-1 was recorded which satisfies the Curie-Weiss relation ω2=A(T c−T). Intensities of the A 1(1TO) and E(1TO) modes were anomalously strengthened with increasing temperature. Raman modes for the thin films exhibit remarkable frequency downshift and upshift which is related to the effect of internal stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575095
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  • 4
    Electronic Resource
    Electronic Resource
    Optical Properties of InGaN/GaN Multiple Quantum Wells (1998)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 264-268 (Feb. 1998), p. 1295-1298 
    Details
    ISSN: 1662-9752
    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
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/03/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.264-268.1295.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Vacuum arc plasma transport through a magnetic duct with a biased electrode at the outer wall (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3329-3331 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Metal plasma formed by a vacuum arc plasma source can be passed through a toroidal-section magnetic duct for the filtering of macroparticles from the plasma stream. In order to maximize the plasma transport efficiency of the filter the duct wall should be biased, typically to a positive voltage of about 10–20 V. In some cases it is not convenient to bias the duct, for example if the duct wall is part of the grounded vacuum system. However, a positively biased electrode inserted into the duct along its outer major circumference can serve a similar purpose. In this article, we describe our results confirming and quantifying this effect. We also show the parametric dependence of the duct transport on the experimental variables. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149913
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  • 6
    Electronic Resource
    Electronic Resource
    Free excitonic transitions in GaN, grown by metal-organic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7001-7004 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic processes of the free excitonic transitions in GaN grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. The recombination lifetimes of the A and B excitons have been measured at different temperatures and excitation intensities, from which radiative recombination lifetimes of about 0.35 and 0.3 ns for the A and B excitons, respectively, have been obtained. An increase in excitation power has resulted in a drastic enhancement in the radiative decay rate as well as in the exciton photoluminescence quantum yield, suggesting the excitonic transitions may provide gain for laser actions in GaN. The high quality as well as high purity of the investigated MOCVD sample has been demonstrated by the observations of (1) the free A- and B-excitonic transitions, (2) excited states of the free excitons, (3) narrow free excitonic emission linewidths (1.7 meV at 10 K), (4) low electron concentration, and (5) high electron mobilities (∼600 cm2/V s). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362448
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  • 7
    Electronic Resource
    Electronic Resource
    An HREELS study of π* and σ* negative ion resonances of c(8×2) benzoate on Cu(110) (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 5942-5947 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: For the c(8×2) benzoate on Cu(110) system, multiple unoccupied states have been measured through negative ion resonances by high-resolution electron-energy-loss spectroscopy (HREELS). Based on the azimuthal and polar angle dependences, we assign contributions from B2 and A1 states to a resonant feature in the 〈001〉 direction and contributions from B1 and A1 states in the 〈110〉 direction. The B2 state is observed close to 4.7 eV and the B1 feature is centered at 6.5 eV. The angular and azimuthal dependence of the C–H stretch intensity in HREELS at resonance is consistent with their assignment and the results of ab initio calculations. Overtone intensity shows an exponential decay as a function of overtone quantum number. From the overtone frequencies, an anharmonicity of 0.0272 is obtained which leads to a dissociation energy of the C–H bond of about 81 kcal/mol. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476005
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  • 8
    Electronic Resource
    Electronic Resource
    Charge transfer in charge-coupled devices fabricated on AlGaN/GaN heterostructures (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1403-1405 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fabrication and operation characteristics of linear array charge-coupled devices on AlGaN/GaN heterostructures are reported. In transistor mode, a three-stage device behaved as a multiple-gated field effect transistor with a transconductance of 12.8 mS/mm. In shift register mode, charge packages can be injected at one side and detected at the other side with a delay corresponding to the number of transfer electrodes of the device. At a transfer frequency of 6 MHz, the devices exhibited an estimated charge transfer efficiency of 0.94. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121957
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  • 9
    Electronic Resource
    Electronic Resource
    Electron transport in AlGaN–GaN heterostructures grown on 6H–SiC substrates (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 707-709 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated two-dimensional electron transport in doped AlGaN–GaN heterostructures (with the electron sheet concentration ns(approximate)1013 cm−2) grown on conducting 6H–SiC substrates in the temperature range T=0.3–300 K. The electron mobility in AlGaN–GaN heterostructures grown on SiC was higher than in those on sapphire substrates, especially at cryogenic temperatures. The highest measured Hall mobility at room temperature was μH=2019 cm2/V s. At low temperatures, the electron mobility increased approximately five times and saturated below 10 K at μH=10250 cm2/V s. The experimental results are compared with the electron mobility calculations accounting for various electron scattering mechanisms. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120852
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  • 10
    Electronic Resource
    Electronic Resource
    Scattered refractive index profiles of thin silicon oxide film on silicon substrate (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 5868-5870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Randomly scattered depth profiles of refractive index are experimentally observed on thin silicon dioxide films on silicon substrates by means of conventional ellipsometry and gradually chemical etching. Computer simulations with an abrupt model and random uncertainties in ellipsometric angles Ψ and Δ show very similar behavior as experiments, and the distribution of the measured profile in the near interface region is in good agreement with 0.02° standard deviation in Ψ. Simulations also indicate that even very small errors in Ψ, as small as 0.001°, can result in divergent depth profile of the refractive index in the near interface region. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366404
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