Combing ratio

Figure 2. Relationship between cleaning efficiency and combing ratio for three feed rates with constant saw speed (adapted from (37)).

Attempts have been made to improve the mechanical properties of these cements by adding reinforcing fillers (Lawrence Smith, 1973 Brown Combe, 1973 Barton et al, 1975). Lawrence Smith (1973) examined alumina, stainless steel fibre, zinc silicate and zinc phosphate. The most effective filler was found to be alumina powder. When added to zinc oxide powder in a 3 2 ratio, compressive strength was increased by 80 % and tensile strength by 100 % (cements were mixed at a powder/liquid ratio of 2 1). Because of the dilution of the zinc oxide, setting time (at 37 °C) was increased by about 100%. As far as is known, this invention has not been exploited commercially. 

Calculations of h have since been made for certain combs (20, 35) and randomly branched structures (20). Kurata and Fukatsu (20) found that the ratio h/g% (which would be unity if the hydrodynamic radius had a fixed ratio to the radius of gyration) was not constant, but a function of g0 depending on the type of branching. Also, they found that as the degree of branching (as measured by the number of sub-chains) increased, h/g% approached a limit, also dependent on the type of branching. They suggested however that the inequality ... 

In several cases the melt viscosity of a series of lightly-branched polymers has been determined as a function of MW, and compared with that of linear polymers, and it has been found or may be deduced from the published data that there is a cross-over molecular weight, below which the branched polymer is less viscous, but above which it more viscous, than the linear polymer of equal MW. This behaviour is observed with some comb-shaped polystyrenes (35) and poly(vinyl acetate)s (59, 89), star polybutadienes (57, 58, 123), and randomly-branched polyethylenes (56,61). Jackson has found (141) that if the ratio ZJZC of the number of chain atoms at the cross-over point, Zx, to the number at the kink in the log 0 — logM curve, Zc, [as given in Ref. (52)], is plotted against nb, the number of branches, a reasonable straight line is obtained, as in Fig. 5.1. 

The ratio of elastic constants Ku, calculated for the S-effect according to the equation (4) appeared to be (Kn (polymer XIV)/Kn (polymer XIII)) x 1 100 and (Ku (polymer XVI)/Kn (polymer XV)) x 1 36. Yet, as we have just indicated, taking into account molecular masses of the LC polymers and reducing k, values for various polymers to equal values of DP one may come to substantially different values for ratios of constants presented. It is necessary to note that up to date no quantitative data on the determination of elastic constants of LC polymers has been published (excluding the preliminary results on Leslie viscosity coefficients for LC comb-like polymer127)). Thus, one of the important tasks today is the investigation of elastic and visco-elastic properties of LC polymers and their quantitative description. 

Schroeder proposed a reverberator consisting of parallel comb filters and series allpass filters [Schroeder, 1962], shown in figure 3.14. The delays of the comb filters are chosen such that the ratio of largest to smallest is about 1.5 (Schroeder suggested... 

Combing these equations enables one to estimate values from either of two ratios shown as follows ... 

The absolute frequency of the fundamental IS — 2S transition in atomic hydrogen has now been measured to 1.8 parts in 1014, an improvement by a factor of 104 in the past twelve years. This improvement was made possible by a revolutionary new approach to optical frequency metrology with the regularly spaced frequency comb of a mode locked femto-second multiple pulsed laser broadened in a non-linear optical fiber. Optical frequency measurement and coherent mixing experiments have now superseded microwave determination of the 2S Lamb shift and have led to improved values of the fundamental constants, tests of the time variation of the fine structure constant, tests of cosmological variability of the electron-to-proton mass ratio and tests of QED by measurement of g — 2 for the electron and muon. 

Studies of 0/ 0 isotope variations in several vascular plant species, mosses and environmental surface bog water from temperate peat bogs (Switzerland) used as climatic archives for paleoclimatic reconstruction were reported by Menot-Combes et 8 0-values in organic material were determined by the online continuous flow method after sample pyrolysis at 1080 °C in the presence of glassy carbon in a Carlo-Erba elemental analyzer. The gases obtained (CO, N2 and H2O) were separated by passing them through a water trap and a GC column in a helium carrier gas. The isotope composition of CO was measured with a VG Prism II isotope ratio mass spectrometer relative to the VSMOW isotope standard. The overall analytical uncertainty is 0.08%o for water 8 0-values." ... 

The Tg may also increase as a result of increased interactions between ion pairs and the formation of ion clusters. The increase in Tg is nearly linear with the ratio Li /EO, even up to a ratio of 0.5 for LiCF3S03 solubilized in PM MS-8 or in the identical poly(methacrylate) comb polymer (Figure 3). The rise in Tg is much more rapid for the poly(methacrylate) comb polymer than for the polysiloxane. The free-volume mechanism of ion conduction is confirmed in our system by the linearity of temperature-dependent conductivity plots when the Vogel-Tammann-Fulcher (VTF) expression a = exp [-K T - rj] (in which is the ideal Tg and and K are constants) (i, 2, 9) is applied. 

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