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  • 1
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Tomographic imaging of the ionosphere is a recently developed technique that uses integrated measurements and computer reconstructions to determine electron densities. The integral of electron density along vertical or oblique paths is obtained with radio transmissions from low-earth-orbiting (LEO) satellite transmitters to a chain of receivers on the earth's surface. Similar measurements along horizontal paths can be made using transmissions from Global Position System (GPS) navigation satellites to GPS receivers on LEO spacecraft. Also, the intensities of extreme ultraviolet (EUV) emissions can be measured with orbiting spectrometers. These intensities are directly related to the integral of the oxygen ion and electron densities along the instrument line of sight. Two-dimensional maps of the ionospheric plasma are produced by analyzing the combined radio and EUV data using computerized ionospheric tomography (CIT). Difficulties associated with CIT arise from the nonuniqueness of the reconstructions, owing to limited angle measurements or nonoptimal receiver location. Improvements in both reconstruction algorithms and CIT measurement systems are being implemented to overcome these difficulties. New imaging systems being developed employ CIT for large area mapping of the plasma densities in the ionosphere. © 1998 American Institute of Physics.
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 4364-4368 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A stainless-steel chamber has been constructed and interfaced to a Fourier transform infrared spectrometer for the purpose of studying laboratory simulated atmospheric aerosols and clouds. The chamber is cylindrical in design and is comprised of a double-walled inner assembly that resides within an outer vacuum jacket. The volume of the aerosol sample region is 28 L. By circulating refrigerated methanol between the double walls of the inner assembly, constant temperature control of the sample region can be maintained between 187 and 300 K. A study of temperature uniformity within the chamber at 291, 240, and 187 K revealed a standard deviation in temperature of 1.6 K as determined from measurements made using five copper–constantan thermocouples. Good agreement is obtained between thermocouple measured temperatures and rotational temperatures computed from infrared absorption spectra of methane gas. The chamber described here has been used to examine heterogeneous chemistry of solid powder samples. A technique of generating an aerosol sample by rapidly dispersing a solid powder in a gas is presented. The half-life of a γ-alumina aerosol sample was measured to be 25 min. © 1996 American Institute of Physics.
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4893-4895 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: To improve the saturation magnetization (Ms) of cobalt ferrite thin films, metal/cobalt ferrite composite thin films were prepared by controlling the sputtering conditions such as oxygen concentration in sputtering gas, substrate temperature, composition of the thin films. With decreasing the oxygen ratio from 50% to 5% in sputtering gas and increasing the substrate temperature from room temperature to 400 °C, the Ms of the thin films was increased and the coercivity (Hc) decreased. The result was attributed to deposition of the metal/cobalt ferrite thin films. With increasing the metal ratio in the thin films, preferred orientation of (111) of cobalt ferrite was worsened in the thin films. The metal deposited in the thin films was identified as cobalt with (002) preferred orientation. In higher cobalt content than the stoichiometric composition of CoFe2O4, the thin films with high Ms and Hc could be deposited in the wide substrate temperature range of 200–400 °C. We can prepare the metal/cobalt ferrite composite thin films with Ms about 580 emu/cm3 and Hc 1700 Oe by controlled the sputtering conditions. The thin films are thought to be applicable to the magnetic recording media with high recording density. © 1996 American Institute of Physics.
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4115-4115 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: To match the requirements for development of transformer cores with lower iron losses, many new materials are under development including amorphous materials, 6.5% Si–Fe sheets and thin gauged 3% Si–Fe sheets. Among these materials, the thin gauged 3% Si–Fe sheets are attracting attention due to their good magnetic properties and scientific interest. Arai et al. reported that the magnetic properties of the sheets were comparable to those of the amorphous materials and (110)[001] preferred orientation of the sheets are developed by tertiary recrystallization.1 The 100 μm thick 3% Si–Fe sheets were prepared via conventional metallurgical processes including melting and casting, hot rolling to 25 mmT at 1200 °C, first cold rolling to 0.5 mmT, intermediate annealing at 800 °C for 30 min, second cold rolling to 0.25 mmT, intermediate annealing at 800 °C for 30 min, final cold rolling to 100 μm and final annealing at 1200 °C for 1 h in a vacuum of 5×10−6 Torr. Among these processes, the cold rolling process is an important one because preferred orientation of the sheets was developed in the process. Nakano et al. reported that there was an optimum cold rolling ratio to get required magnetic properties of the sheets.2 Recently, we found that the reduction rate, i.e., number of passes, as well as reduction ratio affected the preferred orientation and magnetic properties of the sheets. The number of passes in the first cold rolling process was changed from 7 to 60 and B10 values of the final sheets were changed from 1.30 to 1.84 T according to the number of passes. From x-ray experiments, it was found that intensity of (110) peak in the cold rolled and annealed sheets strongly affected the magnetic properties of the final sheets. We will discuss the relationship between the reduction rate and preferred orientation, and magnetic properties of the thin gauged 3% Si–Fe sheets. © 1997 American Institute of Physics.
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  • 5
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A tertiary crystal growth method was used to fabricate thin gauged 3% Si–Fe sheets in order to reduce the thickness of the sheets without deteriorating soft magnetic properties. During the investigation, the magnetic properties of final annealed sheets were found to be directly related to the magnetic properties of final cold rolled sheets. X-ray and transmission electron microscopy were used to understand the above relation. It was found that the fraction of (110) grains at the surface of the final cold rolled sheets significantly affected the final magnetic properties of the final annealed sheets. On the basis of the above argument, the final magnetic properties of the thin gauged Si–Fe sheets can be predicted by the B10 values of the final cold rolled sheets. © 1998 American Institute of Physics.
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4994-4999 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nitrogen ions were implanted into ZnSxSe1−x epilayers grown on p-GaAs (100) substrates by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Dopant activation and annealing out the implant damage were achieved by a postannealing process in a N2 ambient. Schottky structures employing the implanted p-type ZnSxSe1−x were fabricated and device efficacy was examined by photoluminescence (PL) spectroscopy, current–voltage (I–V), current–voltage temperature (I–V–T), and high frequency capacitance–voltage (C–V) measurements. PL spectra showed a clear donor–acceptor pair (DAP) recombination at an energy of 2.735 and 2.72 eV, in both MBE and MOCVD ZnSSe epilayers, respectively, regardless of the postannealing temperatures. The diode conduction in forward bias proceeds by the combination of thermionic and tunneling emission. C–V measurement proved the maximum doping concentration to be around 1017 cm−3 after ion implantation. © 1997 American Institute of Physics.
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2328-2333 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: p-i-n photodiodes were fabricated on nitrogen ion implanted undoped ZnSe/n-type ZnSe epilayers grown on n+GaAs (100) substrates by molecular beam epitaxy. To obtain a quasi-uniform p layer doping profile, nitrogen ions at multiple energies and ion doses were implanted at room temperature. The activation of implanted species was carried out by an optimized post-annealing in a nitrogen ambient. Optical studies were performed on the implanted/annealed devices by photoluminescence spectroscopy at 10 K, which indicated donor–acceptor pairs at an energy of 2.7 eV and its phonon replicas with 30 meV intervals. The circular p-i-n diodes with a 1 mm diam contact area showed a device breakdown voltage to be linearly dependent on the thickness of the undoped ZnSe epilayer. For p-i-n diodes fabricated on an initial 0.5 μm thick undoped ZnSe layer, an ideality factor of 1.19 and a reverse bias breakdown voltage of 12 V was observed. A large photocurrent, good linearity with light intensity, and low dark current were observed. A photocurrent/dark current ratio 〉105 was obtained at an illumination intensity of 100 mW/cm2. These devices exhibited a responsivity of 0.025 A/W at a wavelength of 460 nm through the top 200 Å thick metal contacts.© 1998 American Institute of Physics.
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6614-6616 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: (Co1−xFex)Pt films were grown on a glass substrate by a rf sputtering and then annealed at 650–700 °C in a high vacuum. All the as-sputtered (Co1−xFex)Pt films deposited below 400 °C had a disordered structure and showed very low coercivities. With increasing the deposition temperature and Fe contents, the (111) texture was weakened in as-deposited (Co1−xFex)Pt ternary films. Vibrating sample magnetometer and x-ray diffraction data show that Co atoms in the L10 CoPt phase were substituted with Fe atoms. In-plane coercivities of these films decreased almost linearly with increasing Fe content which seemed to be due to the decrease of a crystalline anisotropy energy. © 1998 American Institute of Physics.
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 596-598 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have observed visible electroluminescence (EL) from silicon nanocrystallites which are embedded in a-Si:H films prepared in a plasma enhanced chemical vapor deposition system. The EL spectra are in the range of 500–850 nm with two peaks located at about 630–680 and 730 nm, respectively. We found that the intensity of EL peaks is related closely to the conductivity of the deposited films. The carrier conduction path is discussed in terms of the material structural characteristics, and a tentative explanation of the light emission mechanism is proposed. © 1996 American Institute of Physics.
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 698-700 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Three photoluminescence (PL) bands at 340–370, 400–430, and 740 nm were observed at room temperature in a-Si:H:O films fabricated by plasma enhanced chemical vapor deposition without any postprocessing. The violet-blue emission is very strong and stable, and its intensity is closely related to the oxygen content in the films, which can be controlled by the applied dc biases on the sample substrates during deposition. The first two PL peaks are ascribed to Si–O related species, and the last one to the quantum size effect of the nanocrystallites embedded in the a-Si:H:O matrix. © 1997 American Institute of Physics.
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