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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3629-3632 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron attachment cross sections are reported in the energy range 0–160 meV, and at resolutions of 6.0–6.5 meV (FWHM) for the molecules CF3SO3H (triflic acid), (CF3SO2)2O (triflic anhydride), and CF3I (methyl iodide). Use is made of the Kr photoionization method. Attachment line shapes are deconvoluted from the spectral slit (electron energy) function, and are converted to cross sections by normalization to thermal attachment rate constants at 300 K. Rate constants as a function of mean electron energy are calculated from the cross sections using a Maxwellian electron energy distribution function. Present data are compared with flowing-afterglow, Langmuir-probe (FALP) results in triflic acid and anhydride, and with high-Rydberg ionization results in CF3I.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 58-61 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An analysis of the molecular effusive flow pattern through a narrow rectangular slit orifice is given in terms of the arrival flux on a parallel detector plane. It is shown that the advantage of having an orifice in the form of a long narrow slit in terms of a pronounced peaked incident beam at the detector plane is only achieved at detector plane separations less than the length of the orifice slit. At separations of the detector plane larger than twice the slit length the arrival flux distribution asymptotically approaches that of an infinitesimal orifice source of arbitrary shape. This is in contrast to recent calculations of flux density versus off-axis detector position reported by Perram and Dorko in Rev. Sci. Instrum. 54, 275 (1983).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 11 (1996), S. 289-302 
    ISSN: 1573-1383
    Keywords: Active Noise Control ; Genetic Algorithm ; FIR Filtering ; Parallel Real-Time Architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A modified model, in the form of an FIR filter, is proposed for the modelling of the acoustic dynamics of an active noise control system. This is a low order filter formulation but consists of two independent elements—a time delay and a d.c. gain. Empirical data has shown that this model constitutes a good representation of the equivalent high order FIR filter and has the additional feature of being a high frequency noise filtering device. Because of its specific structure, the time delay and gain must be identified independently. This restricts the use of the conventional least mean squares technique for parameter optimization, as the cost function intrinsically comprises multimodal error surfaces. The use of Genetic Algorithms could be the best solution to address this issue but their unpredictable response in real-time require some special attention. A fully developed active noise control system, based on the Genetic Algorithm, to achieve the objective of noise reduction is described. To further guarantee the reliability of this approach, a supervisory scheme is incorporated for governing the real-time learning operations. A parallel hardware architecture, using two independent TMS320C30 digital signal processors, is designed for such implementation. The experimental results indicate that this approach to noise control is sound, and that noise reduction of more than 15dB(A) is consistently obtained.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 16 (1995), S. 245-255 
    ISSN: 1572-9567
    Keywords: digital image analysis ; electron beam melting ; high temperature ; liquid metals and alloys ; pendant drop method ; surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A quasi-containerles pendant drop method for measuring the surface tension of molten metals and alloys is being developed. The technique involves melting the end of a high-purity metal rod by bombardment with an electron beam to form a pendant drop under ultra-high-vacuum conditions to minimize surface contamination. The magnified image of the drop is captured from a high-resolution CCD camera. The digitized image of the drop is then analyzed to compute the surface tension. A computer program has been developed that reads the pixel intensities from a graphics file containing the digital image. The code searches for the edge of the drop along rows and columns of pixels and stores the edge coordinates in an array. It then computes an optimized theoretical drop shape by solving the Young-Lapface differential equation from which the quantity of surface tension is deduced. This technique has been demonstrated with the surface tension measurement of molten zirconium metal.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 21 (2000), S. 793-804 
    ISSN: 1572-9567
    Keywords: digital image analysis ; electron beam melting ; high-temperature liquid metals ; melting point ; pendant drop ; quasi-containerless ; surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The surface tensions of liquid metals, Zr, Ni, Ti, Mo, and Nb, have been measured at their melting points using the quasi-containerless pendant drop method. This method involves melting the end of a high-purity metal rod by bombardment with an electron beam to form a pendant drop under ultrahigh-vacuum conditions to minimize surface contamination. The magnified image of the drop is captured from a high-resolution CCD camera and digitized using a frame-grabber. The digital image is analyzed by reading the pixel intensities from a graphics file. The edge coordinates of the drop along rows and columns of pixels are searched by a computer program and stored in an array. An optimized theoretical drop shape is computed from the edge coordinates by solving the Young–Laplace differential equation to deduce the surface tension. The measured surface tensions are compared with available experimental results and theoretical calculations.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 19 (2000), S. 41-60 
    ISSN: 1573-1383
    Keywords: Codesign ; FPGA ; Spring Forming Machine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A new approach to design a high precision real-time control system for a spring forming machine is presented. This system is designed to satisfy the required high motor speed command signal and the product to product tolerance is limited to 0.1%. An innovative variable pulse generation algorithm is proposed for the activation of the motor in order to meet the stringent specifications. Because of the high speed command, software implementation of this algorithm would not be viable as this is intended to be a low cost automation system. To further enhance the system performance, an overall system architecture to incorporate a hardware solution is proposed. This new architecture comprises hardware and software functionality such that the codesign methodology is employed for the partitioning of the design procedures. Within this architecture, software development includes a user-friendly, safety and fault detection facility to improve the human-machine interface. This new precision control system meets the required performance specifications with only two-pieces of 2K gates Field Programmable Gate Array (FPGA) Actel chips are required for the implementation.
    Type of Medium: Electronic Resource
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