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  • American Institute of Physics (AIP)  (40)
  • 2000-2004  (11)
  • 1995-1999  (29)
  • 1950-1954
  • 1930-1934
  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional mapping of the plasma density in the upper atmosphere with computerized ionospheric tomography (CIT) : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2010-2021 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872872
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic linear energy transfer dependent molecular structural growth in polyethylene terephthalate (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4922-4927 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films (13 μm) of polyethelene terephthalate (PET) are irradiated by different swift metallic heavy ions (180 MeV Ag14+ and 200 MeV Au15+) with the projectile linear energy transfer (LET) (∼10–14 keV/nm), respectively. LET dependence on the molecular structural changes in PFT irradiated at different ion fluences has been studied by the Fourier transform infrared spectroscopy. The study has revealed that beyond a critical LET entirely different pathways of amorphization beginning with partial recrystallization at lower ion fluence impact occurs in PET, contrary to the earlier established results. At considerably higher LET (∼14 keV/nm), the most characteristic crystalline stretching and bending vibration bands such as at 850 cm−1 (CH2 rocking), 972 cm−1 (C(Double Bond)O stretching), 1341 and 1471 cm−1 (CH2 bending) in PET have shown a significant rise in the respective infrared absorbance intensities upon lower ion fluence (∼1011 ions/cm2) impact. The absence of previously reported unsaturations such as alkynes at both the LET beam used are also observed. Interestingly, the aromatic system also appears to be unstable and participating in the modification process, particularly at the higher LET (∼14 KeV/nm). Possible interpretations are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462424
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  • 3
    Electronic Resource
    Electronic Resource
    Plasma enhanced metalorganic chemical vapor deposition of amorphous aluminum nitride (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5825-5831 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform infrared, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were observed in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance–voltage, conductance–voltage (G–V), and current–voltage measurements were performed to reveal bulk and interface electrical properties. The electrical properties showed marked dependence on processing conditions of the AlN films. Clear peaks as observed in the G–V characteristics indicated that the losses are predominantly due to interface states. The interface state density ranged between 1010 and 1011 eV−1 cm−2. Annealing in hydrogen resulted in lowering of interface state density values. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413484
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  • 4
    Electronic Resource
    Electronic Resource
    Pulse stretching due to partial temporal overlap of two modes in a TEA CO2 laser (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 579-580 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pulse duration as long as 14 μs has been obtained from a single longitudinal mode TEA CO2 laser. Such stretching occurred under conditions for which oscillation on a higher order transverse mode followed that on the TEM00 mode with partial temporal overlap between the two. Control of the intracavity aperture size in conjunction with cavity length tuning helped realize such an oscillation condition. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150246
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  • 5
    Electronic Resource
    Electronic Resource
    On the recovery of a spark gap in a fast discharge circuit (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 4242-4244 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have shown theoretically that the maximum repetition rate attainable with a switch for both resistive and resonant charging is independent of the value of energy transferred through the switch in case of a very fast discharge. Experimental confirmation of this has been achieved with a resistively charged 20 kV pulse generator (C was varied from ≅5 to 35 nF) switched by a spark gap into a load whose resistance varied from few ohms to a kΩ. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149243
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  • 6
    Electronic Resource
    Electronic Resource
    Stress determination of micromembranes using laser vibrometry (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1965-1969 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A laser vibrometry based dynamic technique for biaxial residual stress determination in micromembranes is reported. Layered, low pressure chemical vapor deposition grown, rectangular shaped micromembranes are ultrasonically excited. The resulting micromembrane displacement, as a function of frequency and position, is recorded to yield resonance frequencies and associated vibrational mode numbers. The stress is determined from this information. Vibrations forced from ultrasonic pressure (∼25 Pa) resulted in peak displacements of tens of nanometers at resonance. For the sample set studied, the (3,1) mode resonance peak displayed the least damping in atmospheric testing and was used to establish stress levels ∼108 N/m2. A trend for this stress showing an overall decrease by ∼40% as a result of thermomechanical cycling was identified. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146952
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  • 7
    Electronic Resource
    Electronic Resource
    Latch proof operation of a switch of a high repetition rate laser with dc resonant charging (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4813-4816 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the operation of a high voltage high current switch in which command resonant charging capability is built in. Elimination of switch latch up problems do not require any extraneous and complex circuitry. The indigenously developed switch delivers power in excess of 3 kW into a dummy load typical of a TE laser at a pulse repetition rate of 200 Hz. The test on a real TEA CO2 laser load was, however, limited up to 50 Hz repetition rate beyond which the accumulation of dissociation products within the active volume led to arcing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146157
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  • 8
    Electronic Resource
    Electronic Resource
    Anomalous capacitance–voltage profiles in quantum wells explained by a quantum mechanical model (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2030-2032 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a quantum mechanical model for understanding and explaining the capacitance–voltage (C–V) carrier profiles observed in quantum wells (QW). The external field imposed on the QW during C–V profiling changes the carrier distribution of the system. This model considers the effects of field and quantum confinement of the carriers in the well. The results obtained by iterative solutions of Schrodinger's and Poisson's equations give a better understanding of the experiments than the previous models where quantum confinement is ignored. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364061
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  • 9
    Electronic Resource
    Electronic Resource
    Photonic band gaps with layer-by-layer double-etched structures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6749-6753 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Periodic layer-by-layer dielectric structures with full three-dimensional photonic band gaps have been designed and fabricated. In contrast to previous layer-by-layer structures the rods in each successive layer are at an angle of 70.5° to each other, achieved by etching both sides of a silicon wafer. Photonic band-structure calculations are utilized to optimize the photonic band gap by varying the structural geometry. The structure has been fabricated by double etching Si wafers producing millimeter wave photonic band gaps between 300 and 500 GHz, in excellent agreement with band calculations. Overetching this structure produces a multiply connected geometry and increases both the size and frequency of the photonic band gap, in very good agreement with experimental measurements. This new robust double-etched structure doubles the frequency possible from a single Si wafer, and can be scaled to produced band gaps at higher frequencies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363802
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrasound induced lubricity in microscopic contact (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1177-1179 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A physical effect of ultrasound induced lubricity is reported. We studied the dynamic friction dependence on out-of-plane ultrasonic vibration of a sample using friction force microscopy and a scanning probe technique, the ultrasonic force microscope, which can probe the dynamics of the tip–sample elastic contact at a submicrosecond scale. The results show that friction vanishes when the tip–surface contact breaks for part of the out-of-plane vibration cycle. Moreover, the friction force reduces well before such a break, and this reduction does not depend on the normal load. This suggests the presence on the surface of a layer with viscoelastic behavior. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120417
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