Float life

Telecommunications systems reliable float life of 10 years at all foreseeable operating temperatures... 

An accelerated life-time test, at a temperature of 55°C and a float-voltage of 2.27 V per cell on 12-V, 50-Ah, front-terminal AGM batteries, confirms the expected life of 12 years at 20°C. At intervals of about two months, capacity was checked at the 10-h discharge rate, and the test results are shown in Fig. 13.15. During more than 300 days the capacity remained at a high level and rather stable. Afterwards, the capacity decreased significantly, and the test was stopped after 380 days when the capacity had dropped to 70% of the nominal value. The float life at 55°C is, therefore, 1 year, and this equates to a life of 12 years for a float operation at 20°C. 

Poaming in place, e.g., steering wheel, floats (life jacket, surfboards, buoys), heat insulation elements, protective clothing, prostheses, seals, noise protection... 

Obviously the float life depends on the battery temperature, too. Figure 17.18 indicates the life results of an accelerated test. In the solid line the values achieved between 50° and 70°C are plotted. The charge voltages were adapted according the values in Figure 17.14. The results follow very well the Arrhenius equation since a temperature increasing of 10°C decreases the float life always to 50%. The extrapolation indicates an average float life at room temperature of 10-12 years, which is identical with practice. 

Figure 17.18 Influence of temperature on float life of valve regulated gel batteries.

Float life The expected float life of the VRLA battery is greater than 8 years at room temperature, arrived at by using accelerated testing methods, specifically, at high temperatures. 

The primary failure mode of the VRLA battery can be defined as growth of the positive plate. Because this growth is the result of chemical reactions within the cell, the rate of growth increases with increasing temperature. In Fig. 24.20 the float life is plotted against temperature. The solid lines represent data from float-life tests performed at two float voltages, 2.3 and 2.4 V per cell. This graph can be used to determine the expected float life at various temperatures. End of life is defined as the failure of the cell to deliver 80% of rated capacity. 

Life For rechargeable batteries, the duration of satisfactory performance, measured in years (float life) or in the number of charge/discharge cycles (cycle life). 

In several cases, such as shellfish areas and aquatic reserves, the usual water quaUty parameters do not apply because they are nonspecific as to detrimental effects on aquatic life. Eor example, COD is an overall measure of organic content, but it does not differentiate between toxic and nontoxic organics. In these cases, a species diversity index has been employed as related to either free-floating or benthic organisms. The index indicates the overall condition to the aquatic environment. It is related to the number of species in the sample. The higher the species diversity index, the more productive the aquatic system. The species diversity index is computed by the equation K- = (S — 1)/logjg I, where S is the number of species and /the total number of individual organisms counted. 

Molecules am act one another. Fiuni that simple fact spring fundamentally important consequences. Rivers, lakes, and oceans exist because water molecules attract one another and form a liquid. Without that liquid, there would be no life. Without forces between molecules, our flesh would drip off our bones and the oceans would be gas. Less dramatically, the forces between molecules govern the physical properties of bulk matter and help to account for the differences in the substances around us. They explain why carbon dioxide is a gas that we exhale, why wood is a solid that we can stand on, and why ice floats on water. At very close range, molecules also repel one another. When pressed together, molecules resist further compression. 

A drop of water contains an unimaginable number of molecules, as our molecular inset shows. Water is essential to life as we know it. The simple yet unusual fact that solid water (ice) floats atop liquid water allows life to exist on our planet. Just as important is the fact that water dissolves an immense range of chemical compounds Water is the solvent of life. In fact, water is so important to our perspective of life that the search for water is a key feature of our quest to discover life in other quarters of the galaxy. The inset photo of the surface of Mars, for example, shows no sign of water at present, but some erosional features appear to have been caused by flowing water in the past. 

The density of ice is less than that of water so that ice floats. Having a frozen ice cap protects life below the ice, whereas a solid phase that sinks means that solid forming near the cold surface will sink, leaving new liquid to freeze and eventually freezing throughout any body of liquid. 

Expandable PS beads are a material devised to accommodate the transportation drawbacks of foams. Foams take up a lot of room, but not much weight, so a truck or boxcar cannot be used very efficiently. Expandable PS beads can be readily turned into foam at their destination. The beads are impregnated with a volatile liquid like pentane as they are extruded, chopped, and cooled. Later, on site, the beads are heated in small batches with steam. The vaporization temperature of the pentane is just below the melting point of the PS beads. As the beads soften, the pentane flashes (volatilizes) and causes the PS to foam. The polymer is then ready for molding. Coffee cups, ice chests, life preservers, buoys, and floats are often fabricated this way. 

Fm currently quite addicted to H. P. Lovecraft s stories. He received no serious attention during his lifetime, yet today he has a cult following." Many people around the world consider his tales of cosmic fungi, ancient Gods, and mysterious dreams to be works of genius, and they carefully study his every word. In the movie version of From Beyond, Doctor Pretorius encounters fishlike life forms that float through our world. We are not aware of these beings due to our limited sensorium, but brain stimulation can awaken humanity to see the new reality. 

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