Search results
Results from the WOW.Com Content Network
In 1999, evidence for time variability of the fine-structure constant based on observation of quasars was announced [9] but a much more precise study based on CH molecules did not find any variation. [10] [11] An upper bound of 10 −17 per year for the time variation, based on laboratory measurements, was published in 2008. [12]
Conversely, the measure is symmetric when the change decreases by an equivalent amount e.g. a halving is equal to a log 2 fold change of −1, a quartering is equal to a log 2 fold change of −2 and so on. This leads to more aesthetically pleasing plots, as exponential changes are displayed as linear and so the dynamic range is increased.
Time metrology or time and frequency metrology is the application of metrology for timekeeping, including frequency stability. [28] [29] Its main tasks are the realization of the second as the SI unit of measurement for time and the establishment of time standards and frequency standards as well as their dissemination. [30]
Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. [1] For liquids, it corresponds to the informal concept of thickness; for example, syrup has a higher viscosity than water. [2]
Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
Molar concentration or molarity is most commonly expressed in units of moles of solute per litre of solution. [2] For use in broader applications, it is defined as amount of substance of solute per unit volume of solution, or per unit volume available to the species, represented by lowercase : [3]
Rates on a 15-year mortgage stand at an average 6.13% for purchase and 6.17% for refinance — no change from 6.13% for purchase and down 3 basis points from 6.14% for refinance this time last week.
Parts-per notation is also employed to denote the change, stability, or uncertainty in measurements. For instance, the accuracy of land-survey distance measurements when using a laser rangefinder might be 1 millimeter per kilometer of distance; this could be expressed as "Accuracy = 1 ppm." [a]