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Fundamental concepts
Published in Bernard S. Massey, John Ward-Smith, Mechanics of Fluids, 2018
Bernard S. Massey, John Ward-Smith
There are circumstances where great precision is not required and just a general indication of magnitude is sufficient. In such cases we refer to the order of magnitude of a quantity. To give meaning to the term, consider the following statements concerning examples taken from everyday life: the thickness of the human hair is of the order 10−4 m; the length of the human thumb nail is of order 10−2 m; the height of a human is of order 1 m; the height of a typical two-storey house is of order 10 m; the cruise altitude of a subsonic civil aircraft is of order 104 m. These examples cover a range of 8 orders of magnitude. The height of a human is typically 4 orders of magnitude larger than the thickness of the human hair. The cruise altitude of an airliner exceeds the height of a human by 4 orders of magnitude. In this context, it is unimportant that the height of most humans is nearer 2 m, rather than 1 m. Here we are simply saying that the height of a human is closer to 1 m rather than 10 m, the next nearest order of magnitude.
Introduction
Published in Vaughn Nelson, Kenneth Starcher, Introduction to Bioenergy, 2017
Vaughn Nelson, Kenneth Starcher, Vaughn Nelson, Kenneth Starcher
In terms of consumption, production, supply, and demand, estimates are needed and in many cases an order of magnitude (OM) calculation will suffice. By order of magnitude, we mean an answer (one significant or at most two significant digits) to a power of 10. For problems and estimations, the answers cannot be more accurate than the least accurate data input, so significant digits must be used. More information on exponents, OM calculations, significant digits, and steps for solving problems and presenting results is presented in Appendix A1, Mathematics.
Underwater Sensor Networks
Published in Jonathan Loo, Jaime Lloret Mauri, Jesús Hamilton Ortiz, Mobile Ad Hoc Networks, 2016
The underwater acoustic channel can be characterized as follows [11]: Narrow bandwidth: Just a few hundred kilohertz, limited by absorption [1]Multipath fadingHigh attenuationBandwidth dependent on frequency and range: According to acoustic telemetry studies [12], the bandwidth × range product is limited, approximately 40 kbps × km—a low value as compared to that of the terrestrial radio. For example, in the IEEE 802.11b/a/g standard, it is 5 Mbps × km (ratio of 1:100).High latency: The speed of sound in water is approximately 1.5 × 103 m/s. The speed of light in vacuum, used in terrestrial communication, is almost 3 × 108 m/s (ratio of 1:10,000, i.e., a difference of 5 orders of magnitude).
Correlation of ISO 16840-2:2007 impact damping and hysteresis measures for a sample of wheelchair seating cushions
Published in Assistive Technology, 2018
Susan J. Hillman, James Hollington, Neil Crossan, Carmen Torres-Sánchez
It is perhaps not surprising however that these measurements are not strongly correlated because, although they both consider time dependent properties of the cushions, the time scales over which they are relevant are very different. The thickness measures used in the computation of h250 and h500, for example, are taken after each load has been applied for 120 s ± 10 s, whereas the impact damping measures examine changing accelerations after an impact, which is typically completed in around one second. This constitutes a difference of approximately two orders of magnitude.