ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Collection
Keywords
Language
Years
  • 1
    Publication Date: 2023-06-17
    Description: Knowledge of pressure-dependent static and dynamic moduli of porous reservoir rocks is of key importance for evaluating geological setting of a reservoir in geo-energy applications. We examined experimentally the evolution of static and dynamic bulk moduli for porous Bentheim sandstone with increasing confining pressure up to about 190 MPa under dry and water-saturated conditions. The static bulk moduli (Ks) were estimated from stress–volumetric strain curves while dynamic bulk moduli (Kd) were derived from the changes in ultrasonic P- and S- wave velocities (~ 1 MHz) along different traces, which were monitored simultaneously during the entire deformation. In conjunction with published data of other porous sandstones (Berea, Navajo and Weber sandstones), our results reveal that the ratio between dynamic and static bulk moduli (Kd/Ks) reduces rapidly from about 1.5 − 2.0 at ambient pressure to about 1.1 at high pressure under dry conditions and from about 2.0 − 4.0 to about 1.5 under water-saturated conditions, respectively. We interpret such a pressure-dependent reduction by closure of narrow (compliant) cracks, highlighting that Kd/Ks is positively correlated with the amount of narrow cracks. Above the crack closure pressure, where equant (stiff) pores dominate the void space, Kd/Ks is almost constant. The enhanced difference between dynamic and static bulk moduli under water saturation compared to dry conditions is possibly caused by high pore pressure that is locally maintained if measured using high-frequency ultrasonic wave velocities. In our experiments, the pressure dependence of dynamic bulk modulus of water-saturated Bentheim sandstone at effective pressures above 5 MPa can be roughly predicted by both the effective medium theory (Mori–Tanaka scheme) and the squirt-flow model. Static bulk moduli are found to be more sensitive to narrow cracks than dynamic bulk moduli for porous sandstones under dry and water-saturated conditions.
    Description: Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)
    Keywords: ddc:550.78 ; Porous sandstone ; Static bulk modulus ; Dynamic bulk modulus ; Narrow (compliant) cracks ; Equant (stiff) pores
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2024-02-14
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Aseismic slip may occur during a long preparatory phase preceding earthquakes, and what controls it remains poorly understood. In this study, we explored the role of load point velocity and surface roughness on slow slip during the preparatory stage prior to stick‐slip events. To that end, we conducted displacement‐rate controlled friction experiments by imposing varying load point velocities on sawcut granite samples with different surface roughness at a confining pressure of 35 MPa. We measured the average slip along the fault with the recorded far‐field displacements and strain changes, while acoustic emission sensors and local strain gages were used to capture local slip variations. We found that the average amount of aseismic slip during the preparatory stage increases with roughness, whereas precursory slip duration decreases with increased load point velocity. These results reveal a complex slip pattern on rough faults which leads to dynamic ruptures at high load point velocities.〈/p〉
    Description: Plain Language Summary: Earthquakes occur mostly along preexisting faults in the earth crust. These faults exhibit various geometrical complexities and are subjected to different strain rates. In the laboratory, we produce earthquake analogs by sliding sawcut granite blocks. We vary the geometrical complexity of the faults by roughening their surfaces and modify the strain rate by displacing the blocks at varying velocities. Under these different conditions, we measure how the forces accumulated by friction are released, by measuring stresses and displacements applied on the block's edges, using local strain deformation sensors, and by recording very small earthquakes occurring during sliding along the sawcut faults. We find that smooth sawcut faults tend to release all the energy accumulated very abruptly, after a very small amount of slip, regardless of the load point velocity applied. The processes leading to failure in the case of a rough fault are much more complex, involving a large amount of slip, and numerous small earthquakes which are distributed heterogeneously in space and time.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Acoustic emissions highlight the complex preparatory phase prior stick‐slips on rough faults〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Preparatory slip increases with roughness and the duration of the preparatory phase decreases with increasing load point velocity〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Rough and heterogeneous faults are more stable than smooth faults, but can become unstable with a small increase of load point velocity〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: SAIDAN
    Description: https://doi.org/10.5281/zenodo.6411819
    Keywords: ddc:550.78 ; rock friction ; roughness ; dynamic rupture ; acoustic emissions
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 32 (Feb. 2008), p. 93-98 
    ISSN: 1662-8985
    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
    Notes: This paper presents bonding technology of aluminum alloy by hot-dipping tin. Thedissolution curve of copper in molten tin liquid was obtained in the experiment of hot-dipping Sn.Optimal hot-dipping parameter which was suitable for soldering was designed. To elucidatecharacteristics of interfacial evolution, the microstructure of the coatings, soldered joint wereanalyzed using optical microscopy, SEM and EDX. The shear strength of soldered joints was testedas high as 39.9Mpa, which is high enough to achieve the requirement of electronic industry
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 131-133 (Oct. 2007), p. 393-398 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The thermal donor formation at 425oC - 450oC in Ge doped Czochralski (GCZ) siliconhaving about 1016 cm-3 Ge content pretreated by rapid thermal annealing (RTA) and conventionalfurnace annealing (CFA) has been investigated using low-temperature infrared spectroscopy(LT-IR). The measurements prove that lightly Ge doping can enhance the formation of thermaldouble donors in the initial stage of the low temperature annealing after RTA process. Ge inducedadditional grown-in oxygen precipitates during silicon ingot growth and the abundantself-interstitials during RTA may be the reason for the enhancement. However, after extending theannealing time at the low temperatures, the thermal donor concentration in the GCZ silicon is lowerthan that in the conventional CZ silicon. In final, the mechanism is also discussed
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    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
    Notes: Horizontal air-cooled low-pressure hot-wall CVD (LP-HWCVD) system is developed toget high quality 4H-SiC epilayers. Homoepitaxial growth of 4H-SiC on off-oriented Si-face (0001)4H-SiC substrates purchased from Cree is performed at a typical temperature of 1500°C with apressure of 40 Torr by using SiH4+C2H4+H2 gas system. The surface morphologies and structuraland optical properties of 4H-SiC epilayers are characterized with Nomarski optical microscope,atomic force microscopy (AFM), x-ray diffraction, Raman scattering, and low temperaturephotoluminescence (LTPL). The background doping of 32 μm-thick sample has been reduced to2-5×1015 cm-3. The FWHM of the rocking curve is 9-16 arcsec. Intentional N-doped and B-doped4H-SiC epilayers are obtained by in-situ doping of NH3 and B2H6, respectively. Schottky barrierdiodes with reverse blocking voltage of over 1000 V are achieved preliminarily
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    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
    Notes: The in-situ p-type doping of 4H-SiC grown on off-oriented (0001) 4H-SiC substrates was performed with trimethylaluminum (TMA) and/or diborane (B2H6) as the dopants. The incorporations of Al and B atoms and their memory effects and the electrical properties of p-type 4H-SiC epilayers were characterized by secondary ion mass spectroscopy (SIMS) and Hall effect measurements, respectively. Both Al- and B-doped 4H-SiC epilayers were p-type conduction. It was shown that the profiles of the incorporated boron and aluminum concentration were in agreement with the designed TMA and B2H6 flow rate diagrams. The maximum hole concentration for the Al doped 4H-SiC was 3.52×1020 cm-3 with Hall mobility of about 1 cm2/Vs and resistivity of 1.6~2.2×10-2 Wcm. The heavily boron-doped 4H-SiC samples were also obtained with B2H6 gas flow rate of 5 sccm, yielding values of 0.328 Wcm for resistivity, 5.3×1018 cm-3 for hole carrier concentration, and 7 cm2/Vs for hole mobility. The doping efficiency of Al in SiC is larger than that of B. The memory effects of Al and B were investigated in undoped 4H-SiC by using SIMS measurement after a few run of doped 4H-SiC growth. It was clearly shown that the memory effect of Al is stronger than that of B. It is suggested that p-type 4H-SiC growth should be carried out in a separate reactor, especially for Al doping, in order to avoid the join contamination on the subsequent n-type growth. 4H-SiC PiN diodes were fabricated by using heavily B doped epilayers. Preliminary results of PiN diodes with blocking voltage of 300 V and forward voltage drop of 3.0 V were obtained
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 556-557 (Sept. 2007), p. 109-112 
    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
    Notes: Homoepitaxial growth of 4H-SiC p+/π/n- multi-epilayer on n+ substrate and in-situ dopingof p+ and π-epilayer have been achieved in the LPCVD system with SiH4+C2H4+H2. The surfacemorphologies, homogeneities and doping concentrations of the n--single-epilayers and the p+/π/n-multi-epilayers were investigated by Nomarski, AFM, Raman and SIMS, respectively. AFM andRaman investigation showed that both single- and multi-epilayers have good surface morphologiesand homogeneities, and the SIMS analyses indicated the boron concentration in p+ layer was at least100 times higher than that in π layer. The UV photodetectors fabricated on 4H-SiC p+/π/n-multi-epilayers showed low dark current and high detectivity in the UV range
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    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
    Notes: 3C-SiC is a promising material for the development of microelectromechanical systems(MEMS) applications in harsh environments. This paper presents the LPCVD growth of heavilynitrogen doped polycrystalline 3C-SiC films on Si wafers with 2.0 μm-thick silicon dioxide (SiO2)films for resonator applications. The growth has been performed via chemical vapor depositionusing SiH4 and C2H4 precursor gases with carrier gas of H2 in a newly developed vertical CVDchamber. NH3 was used as n-type dopant. 3C-SiC films were characterized by scanning electronmicroscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), secondaryion mass spectroscopy (SIMS), and room temperature Hall Effect measurements. It was shown thatthere is no voids at the interface between 3C-SiC and SiO2. Undoped 3C-SiC films show n-typeconduction with resisitivity, Hall mobility, and carrier concentration at room temperature of about0.56 [removed info]⋅cm, 54 cm2/Vs, and 2.0×1017 cm-3, respectively. The heavily nitrogen doped polycrystalline3C-SiC with the resisitivity of less than 10-3 [removed info]⋅cm was obtained by in-situ doping. PolycrystallineSiC resonators have been fabricated preliminarily on these heavily doped SiC films with thicknessof about 2 μm. Resonant frequency of 49.1 KHz was obtained under atmospheric pressure
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 575-578 (Apr. 2008), p. 174-179 
    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
    Notes: This paper analyzes the forming process methods of fin used in CPU chip to emit heat.The whole process is blanking, the first forging forming, the second forging (sizing), and trimming.The chamfer design of CPU fin blank is simulated by finite element analysis. The optimizedchamfer 1.6 mm is available. Semi-enclosed cold forging of progressive dies is put forward. Thenewly designed transfer unit is applied, which unifies the merit of high efficiency of the progressivedies and the high material-using ratio of the project die. Quick disassembly structure is designedand pins are used as quick disassembly pins by means of ball bearing bushing. The uniqueprocessing of the shearing scrap structure is adopted when designing the inverted trimming dies.Compared with the traditional die, the mechanization and electrization are realized to increase theproduction efficiency and get highly precise CPU fin
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...