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  • Z 1 region  (1)
  • ammonia  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 121 (1995), S. 225-236 
    ISSN: 1436-5073
    Keywords: ammonia ; sensor ; colorimetric ; plastic ; optical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preparation and characterization of three different plastic thin-film colorimetric sensors for gaseous ammonia is described. In the film sensors, the neutral form of a pH-sensitive dye (Bromophenol Blue, Bromocresol Green or Chlorophenol Red) was encapsulated in a plastic medium, either poly(vinyl butyral) or ethylcellulose plasticized with tributyl phosphate. Each of these film optodes gave a reproducible and reversible response towards gaseous ammonia. The sensitivity of the film sensors towards ammonia was found to be strongly dependent upon the pK a of the encapsulated dye. Thus, the film with Chlorophenol Red (pK a = 6.25), proved to be very insensitive (operating range: 0.29% 〈 %NH3 〈 100%), whereas the film with Bromophenol Blue (pK a = 4.1), was much more sensitive (operating range: 0.0003% 〈 %NH3 〈 0.11%). The sensitivity of a plastic film sensor decreased markedly with increasing operating temperature and the 90% response (15–38 s) and recovery (820-127 s) times were slow and activation-controlled.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2754
    Keywords: stress structure ; singularity ; Z 1 region ; stress triaxialityRσ ; CTOD ; shear lip ; interpolative method ; degree parameter of the plane strain state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract Based on [1], the stress structures of the smooth region and shear lip of the specimens have been investigated in the paper. The characteristics of the stress structure in the smooth region have been found that the variable z can separated out; the stresses in the midsection can be obtained by the plane strain FEM results or HRR structure modified by the stress triaxiality. The effects of load level and thickness on the stress structure can be reflected by the distribution of CTOD along the thickness direction. The obtained expressions of the stresses are very simple and visualized. The analyses of the stress structure in the shear lip show that the stresses can be obtained by different methods of interpolation to a certain precise degree. A new degree parameter of the plane strain state has been put forward and studied. The parameter can reflect relatively well the variation of the kind and thickness of the specimen as well as the load level. The fracture parameter has also been investigated to be sure that it can be obtained by modified CTOD with the stress triaxiality.
    Type of Medium: Electronic Resource
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