Cyclic experiment

IR Dichroism. Two types of IR-dichroism experiments were used in this study to follow segmental orientation. First, dynamic differential dichroism was used to follow chain orientation while the sample was elongated at a constant strain rate. This experiment was performed with different IR peaks which allowed a comparison of the molecular orientations for each blend constituent. Second, a cyclic experiment was used where the film was strained to a predetermined elongation, relaxed at the same strain rate until the stress was reduced to zero, and then elongated to a higher level of strain, and so forth. 

G. C. Blytas (Shell Development Co., Oakland, Calif. 94623) In Table I, how do you explain the difference in capacity and selectivity of NaY, 1/16-inch extrudate, and of the same sample ground to 20-40-mesh Is it an effect of the amount of binder present (which may change during grinding) or is it a kinetic effect (incomplete equilibration) In your fixed-bed cyclic experiments, what is the duration of the entire cycle ... 

To N mm threshold tearing energy from cyclic experiment... 

Figure 3.6. dC /dT versus temperature data for polystyrene in a cyclic experiment. 

Phase 2 consisted of a series of load-unload cycles conducted at the same rate as in Phase 1, but taken to progressively higher nominal strains Cmax on each cycle 1,2, 3. Between 3 and 5 cycles were possible before failure with most materials. These may be described as pseudo-cyclic experiments, to distinguish them from those in Phase 1 where the maximum strain was constant. As in Phase 1, for each... 

The light-induced shape-memory functionality of the polymers is quantified by cyclic, photomechanical experiments luider stress-controlled and/or strain-controlled conditions. These cyclic experiments have been designed in analogy to those characterizing a thermally-induced SME. 

In particular, the variations of peak current and peak potentials with scan rate are of interest. Normally, the behavior in single-scan and cyclic voltammetry will be different since the initial conditions for diffusion in a single scan experiment are necessarily different from those in a cyclic experiment where the time of relaxation of the concentration gradients in relation to the scan repetition time is an important factor. 

A simpler way to increase the precision of linear sweep and cyclic experiments is offered by the derivation of I — E curves. The potential at which the rapidly descending derivative curve passes the zero line defines Ep. With currently available instrumentation, Ep can be measured to +0.1 mV accuracy using analog differentiation of the currenttime response [125]. 

Fig. 2. Time (x) and scattering vector (Q) raqge for various scattering experiments on dynamics SANS ILL spectrometers Dll and DI7 relaxation after stepstrain, cyclic experiments, steady couette shear. Elastic neutron scattering ILL spectrometer D20, also real time experiment. Neutron Spin Echo (NSE) ILL spectrometer, inelastic measurement and classical quasielastic light scattering (QELS) (from Ref. )...

Fourier transform infrared spectroscopy (FTIR) has emerged as a valuable tool for rubber analysis. Siesler monitored the onset, progress and decay of strain-induced crystallization of a sulfur-cured NR during a cyclic experiment. The infrared absorbance of NR at 1126 cm assigned to C-CH3 in-plane deformation vibration is a band sensitive to crystallinity. A thickness reference band was taken to be the 1662 cm one assigned to v(C=C) stretching. The ratio of the absorbance bands at 1126 cm and 1662 cm revealed the reversible nature of strain-induced crystallization of NR. 

If we perform cyclic experiments at different strain amplitudes and plot the stabilised values of the stress amplitude, we arrive at the cyclic stress-strain diagram sketched in figure 10.29. Usually, it does not coincide with the result of a monotonous tensile or compressive test. If cyclic hardening occurs,... 

For the transport of water the diflhision coefficient is also an important factor. The cyclic experiments can now be used to test whether D is independent of the amount of water absorbed in a coating. This is normally assumed in studies of water uptake by organic coatings. To describe the diffusion in a one-dimensional system. Pick s law is used ... 

Beeause all coatings in the cyclic experiments have a thickness (6r) of around 90 pm and within the cycles the thickness is assumed to be constant (no swelling occurs), a comparison of the diffusion coefficient of water in the eycles ean be made. Beeause of the constant thickness 5x can be set to unity. Furthermore, the flux Jis equal to the inerease in water content in time, which is approximately proportional to 8C/5t (C = capacitance), whieh is the derivative of the curves in Figures 15 and 16. Finally, 8c is the change in relative humidity going from one atmosphere to another. 

With time-dependent fluids, the relation between shear stress and shear rate depends on the time and flow history of the fluid. They can be classified as either thixotropic or andthixotropic (or rheopecdc). For thixotropic fluids, the shear stress will decrease with time for a fixed value of shear rate. A simple explanation is that as the liquid is sheared, the structure breaks down. If a cyclic experiment is carried out, a hysteresis loop is formed. Examples include greases, printing inks, jelly, paints, and drilling muds. For andthixotropic (rheopecdc) fluids, the shear stress will increase with dme for a fixed value of shear rate. Examples include clay suspensions and gypsum suspensions. 

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