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  • 1
    Electronic Resource
    Electronic Resource
    A novel means of generating assembly sequences using the connector concept (1999)
    Springer
    Journal of intelligent manufacturing 10 (1999), S. 423-435 
    Details
    ISSN: 1572-8145
    Keywords: Assembly sequence planning ; connector ; component interaction ; connector-based assembly element ; connector-based assembly sequence graph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Assembly planning attempts to arrange product assembly sequences on the basis of the input of product description, similar assembly plans and assembly constraints. Assembly planning is frequently viewed as a creative thinking process, which requires extensive assembly planning experience. Assembly product modeling with mechanical connection functions has increasingly focused on assembly sequence planning. When considering the connection functions, the relationships between assembled components can act as a foundation for assembly clustering. Despite the merits of assembly sequence planning in lieu of considering connection functions, previous investigations have focused primarily on product representation with the connector concept. However, to our knowledge, generation of the assembly sequence on the basis of the connector concept has not been previously discussed. In this study, we present a novel means of generating assembly sequences on the basis of the connector concept. The proposed method initially defines different types of connectors and representation schemes. Through the definition and representation scheme, an assembly product can be decomposed into a set of connector-based assembly elements. The connector-based assembly elements then serve as input for an assembly sequence generation algorithm, which is connector-based, to generate an assembly sequence. The final output is a connector-based assembly sequence graph, resembling an assembly precedence diagram. In addition, this graph can act as the input for any line balance method when designing work elements for each assembly workstation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008971030395
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    Paper (German National Licenses)
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  • 2
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    Analysis of the Performance Characteristics of the Five-Channel Microtops II Sun Photometer for Measuring Aerosol Optical Thickness and Precipitable Water Vapor (2001)
    In:  CASI
    Details
    Publication Date: 2009-05-19
    Description: Five Microtops II sun photometers were studied in detail at the NASA Goddard Space Flight Center (GSFC) to determine their performance in measuring aerosol optical thickness (AOT or Tau(sub alphalambda) and precipitable column water vapor (W). Each derives Tau(sub alphalambda) from measured signals at four wavelengths lambda (340, 440, 675, and 870 nm), and W from the 936 nm signal measurements. Accuracy of Tau(sub alphalambda) and W determination depends on the reliability of the relevant channel calibration coefficient (V(sub 0)). Relative calibration by transfer of parameters from a more accurate sun photometer (such as the Mauna-Loa-calibrated AERONET master sun photometer at GSFC) is more reliable than Langley calibration performed at GSFC. It was found that the factory-determined value of the instrument constant for the 936 nm filter (k= 0.7847) used in the Microtops' internal algorithm is unrealistic, causing large errors in V(sub 0(936)), Tau(sub alpha936), and W. Thus, when applied for transfer calibration at GSFC, whereas the random variation of V(aub 0) at 340 to 870 nm is quite small, with coefficients of variation (CV) in the range of 0 to 2.4%, at 936 nm the CV goes up to 19%. Also, the systematic temporal variation of V(sub 0) at 340 to 870 nm is very slow, while at 936 nm it is large and exhibits a very high dependence on W. The algorithm also computes Tau(sub alpha936) as 0.91Tau(sub alpha870), which is highly simplistic. Therefore, it is recommended to determine Tau(sub alpha936) by logarithmic extrapolation from Tau(sub alpha675) and Tau(sub alpha 870. From the operational standpoint of the Microtops, apart from errors that may result from unperceived cloud contamination, the main sources of error include inaccurate pointing to the Sun, neglecting to clean the front quartz window, and neglecting to calibrate correctly. If these three issues are adequately taken care of, the Microtops can be quite accurate and stable, with root mean square (rms) differences between corresponding retrievals from clean calibrated Microtops and the AERONET sun photometer being about +/-0.02 at 340 nm, decreasing down to about +/-0.01 at 870 nm.
    Keywords: Instrumentation and Photography
    Format: text
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