Testing test speed effects

An epidemiological study tested the effects of chronic exposure to jet fuel in factory workers (Knave et al. 1978). This study found significant increases in neurasthenia (i.e., fatigue, depressed mood, lack of initiative, dizziness, and sleep disturbances) in the exposed subjects when compared to unexposed controls from the same factory. Also, attention and sensorimotor speed were impaired in the exposed workers, but... 

Based on effects caused in monkeys and rats, the following are expected in humans 20,000 ppm for 60 minutes, coma and possibly death 10,000 ppm for 30 minutes, marked incoordination 2000ppm for 5 minutes, disturbance of equilibrium. Human subjects exposed to 900-1000ppm for 20 minutes experienced light-headedness, incoordination, and impaired equilibrium transient eye irritation has also been reported at similar concentrations. Impairments in psychomotor task performance such as reaction time, perceptual speed, and manual dexterity have been demonstrated at levels around 350ppm. Other studies at similar exposure levels have failed to show any impairment, but the type of task chosen to test behavioral effects and the times at which behavioral measures were sampled during the course of exposure may explain the variations from study to study." ... 

The basic method is a closely specified test intended for quality control or the comparison of bonding systems, but could readily be extended to investigate the effects of test piece dimensions, peeling angle, test speed, etc. 

Recently, Pople et al. [16] and Gadre et al. [17,18] have realized nearly two orders of magnitude increase in the speed of ab initio EP calculations using the GAUSSIAN 92 [19] and INDMOL codes, respectively. This achievement will certainly open new areas for ab initio applications in the near future. Pople et al. tested the effectivity of their method on a large oligonucleotide molecule... 

More recently, Stip et al. (2000) summarized the literature on lithium-induced memory problems Several studies have shown cognitive impairment in short-term memory, long-term memory and psychomotor speed in bipolar patients taking lithium. Their study aimed at testing the effect of lithium in normal subjects in a double-blind, 3-week study. They found that lithium-treated volunteers had long-term memory deficits on recalling words compared to the placebo group. 

Further work was carried out with 3% - 5% of co-sputtered nickel to evaluate the effects of film thickness and test speed and load. He found that the life of a co-sputtered film increased almost linearly with coating thickness, while that of a conventional film reached a maximum at a thickness of about 4000 nm (40,000A), These are far thicker than coatings described by other authors. A comparison of life... 

The evolution of the effective toughness, Ketr (deduced graphically), towards the apparent toughness, Kjmax (calculated for aAV = 0.5 using equation 1), over 5 decades of test speed - at room temperature - and from -30 to 60°C - at 0.001 m/s, i.e. in the ductile range for both grades - can be summarised as follows according to Fig. 6 and 7 ... 

Fig. 6. Evolution of the apparent toughness, Kimm, and the effective toughness, Keir, for iPP/EPR-1 and iPP/EPR-2 tested over a wide range of test speeds at room temperature.

Fig. 9. Size of the plastic zone, rp, and effective acture resistance, K tr, plotted against the logarithm of the test speed. Grey zone transition zone, incertainty about the values tp and K fp. Material iPP/EPR-1 tested at room...

Indeed, as obvious from both exemples given in Fig. 2, the transition could thus be determined accurately within 0.1-0.2 decades of test speeds with few samples in a relative short time frame. Moreover, as the apparent values (Kimax) are always lower than the effective parameters (Keff), none of the material descriptor would be overestimated. In addition, since Kjmax-values have been shown to provide a semi-quantitative evaluation (in terms of test speed or temperature) of fracture resistance parameters, a coherent material comparison would be possible over the whole investigated range. This remark remains true as long as the grades have similar rp. For iPP grades, it should be checked (and considered with more caution) when materials exhibit different particle and matrix melt flow rates, or different crystalline structures. It should also be investigated in detail when different polymer families (ABS versus HIPS or rubber modified iPP) are compared. 

Fig. 25. Effect of testing speed on radk concentration in polychlo-rt ene at 123 K. Pre-orientation 300% (after Ref. ))...

The photo shows an X-15 rocket-powered aircraft used to test the effects of high-speed, high-altitude flight on humans and materials. The rocket engines, mounted under the wing of a B52 bomber, are powered by the reaction of H2 and O2. Data from 199 runs made by such aircraft were used in the development of the space shuttle. 

The final transition, Transition II, occurs at a test speed about two decades above that at which Transition I is seen. The unstable fracture already occurs in the linear domain of the force-displacement curve (a in Figure 3). This transition is related to the total disappearance of toughening effects. The absence of a whitened zone on the specimen is noticeable. Under these conditions, the KImax = Klc and GImax = Glc values measured for the 2 L15 system are even lower at high test speeds than those measured for the neat PMMA. 

Major Pathways and Reactions Effects. As seen above the experimental data (flame speeds, flame widths and NO concentrations) are well described by the kinetic mechanism. A schematic of the whole kinetic chain for the combustion of the nitrogeneous species is shown in Figure 4. The relative influence of reactions on a species are determined by a flux analysis (13, ). This is a flame averaged analysis, but it typically gives results similar to a comparison of net reaction rates in the reaction zone. To further test the effect of the specific reaction changes we recalculate selected flames. 

Because plastics are temperature and time dependent, by virtue of their viscoelasticity, both parameters must be defined where comparisons between materials are to be made. The test temperature is typically the standard one as noted in Chapter 6. although nonstandard conditions are used to measure the effect of temperature. The test is normally carried out at one of the standard test speeds, chosen from a set of values given in the standard. These recommended speeds are shown in Table 2. Note that for modulus measurement the test speed is normally I mm/min. 

Ashton and Valentin compared the performance of an Airmix, Nautamix, Oblicone and Z-biade mixer using equi-sized particles of sand and calcite. The mixture quality achieved approached that of the random mixture quality in all four mixers but this condition was achieved most rapidly in the Airmix followed by the Oblicone, Nauta and Z-blade mixers. When testing the effect of mixer variables on the quality of mixing achieved it was found that the tumbler mixer permance was very dependent on rotational speed. 

---