In 1955, Paul Erdős showed that the density of amicable numbers, relative to the positive integers, was 0.

Because this range of non-zero amplitude may be very broad or infinite, this definition is typically relaxed so that the bandwidth is defined as the range of frequencies in which the signal's spectral density is above a certain threshold relative to its maximum.

Most commonly, bandwidth refers to the 3-dB bandwidth, that is, the frequency range within which the spectral density ( in W / Hz or V < sup > 2 </ sup >/ Hz ) is above half its maximum value ( or the spectral amplitude, in V or V / Hz, is more than 70. 7 % of its maximum ); that is, above − 3 dB relative to the peak.

In some cases density is expressed as the dimensionless quantities specific gravity or relative density, in which case it is expressed in multiples of the density of some other standard material, usually water or air / gas.

Overall unemployment has been exacerbated by an influx of refugees from the wars in neighboring countries, attracted to Honduras, ironically, by its relatively low population density and relative peace.

Most mafic minerals are dark in color and the relative density is greater than 3.

Quantitative computed tomography differs from DXA in that it gives separate estimates of BMD for trabecular and cortical bone and reports precise volumetric mineral density in mg / cm < sup > 3 </ sup > rather than BMD's relative Z score.

An explanation of this is that although the logarithm of the lognormal density function is quadratic in, yielding a " bowed " shape in a log-log plot, if the quadratic term is small relative to the linear term then the result can appear almost linear.

Swimming relies on the natural buoyancy of the human body, with the relative density of the average body, compared to water, of 0. 98, creating a floating effect.

The relative density difference means that water supports the body during swimming, and therefore makes swimming low impact compared to surface activities such as running where weight is put on to the joints, and also creates resistance when moving through the water.

This map of shipping routes illustrates the relative density of commercial shipping in the world's oceans.

Each spot corresponds to a different type of variation in the electron density ; the crystallographer must determine which variation corresponds to which spot ( indexing ), the relative strengths of the spots in different images ( merging and scaling ) and how the variations should be combined to yield the total electron density ( phasing ).

Specific gravity usually means relative density with respect to water.

The term " relative density " is often preferred in modern scientific usage.

If a substance's relative density is less than one then it is less dense than the reference ; if greater than 1 then it is denser than the reference.

If the relative density is exactly 1 then the densities are equal ; that is, equal volumes of the two substances have the same mass.

If the reference material is water then a substance with a relative density ( or specific gravity ) less than 1 will float in water.

For example, an ice cube, with a relative density of about 0. 91, will float.

A substance with a relative density greater than 1 will sink.

where RD is relative density, ρ < sub > substance </ sub > is the density of the substance being measured, and ρ < sub > reference </ sub > is the density of the reference.

Just as radiative forcing provides a simplified means of comparing the various factors that are believed to influence the climate system to one another, global-warming potentials ( GWPs ) are one type of simplified index based upon radiative properties that can be used to estimate the potential future impacts of emissions of different gases upon the climate system in a relative sense.

For those gases, the relative radiative forcing will depend upon abundance and hence upon the future scenario adopted.

Similar to xenon, neon content observed in samples of volcanic gases is enriched in < sup > 20 </ sup > Ne, as well as nucleogenic < sup > 21 </ sup > Ne, relative to < sup > 22 </ sup > Ne content.

* v is the speed of the exhaust gases measured relative to the rocket.

It appears, then, that confronted with the problem of calculating the relative diameter of the atoms of which, he was convinced, all gases were made, he used the results of chemical analysis.

As distinct from the dust devil, it is improbable that the height reached by the fire gas vortex is greater than the visible height of the vertical flames because of turbulence in the surrounding gases that inhibit creation of a stable boundary layer between the rotating / rising gases relative to the surrounding gases.

Hence, for a given temperature and pressure, the molar volume is the same for all ideal gases and is known to the same precision as the gas constant: R = 8. 314 4621 ( 75 ) J mol < sup >− 1 </ sup > K < sup >− 1 </ sup >, that is a relative standard uncertainty of 9. 1 × 10 < sup >− 7 </ sup >, according to the 2010 CODATA recommended value.

Thus, the relative molecular weights of two gases are equal to the ratio of weights of equal volumes of the gases.

This effect is moderately well understood and leads to a cooling from the negative radiative forcing of about 0. 5 W / m < sup > 2 </ sup > relative to pre-industrial values, partially offsetting the larger ( about 2. 4 W / m < sup > 2 </ sup >) warming effect of greenhouse gases.

They are only effective on some gases, depending on the freezing and boiling points of the gas relative to the cryopump's temperature.

In other words, the relative rates of effusion of two gases at the same temperature and pressure are given by the inverse ratio of the square roots of the masses of the gas particles.

Purified nitrogen and argon gases are most commonly used as inert gases due to their high natural abundance ( 78 % N < sub > 2 </ sub >, 1 % Ar in air ) and low relative cost.

He was the first to correctly measure the relative infrared absorptive powers of the gases nitrogen, oxygen, water vapour, carbon dioxide, ozone, methane, etc.

Because all atmophile elements are either gases or form volatile hydrides, atmophile elements are strongly depleted on earth as a whole relative to their solar abundances owing to losses from the atmosphere during the formation of the Earth.

Apart from the intrinsic importance of knowing relative gas concentrations ( e. g. to estimate the extent of greenhouse warming ), their isotopic composition can provide information on the sources of gases.

** Vapour density, a relative density used for gases

The chamber is used as containing in typical experimental conditions a mixture of the gases argon, isobutane and freon at the relative proportions of two thirds of the first gas, with almost one third of the second and a much smaller percentage ( 0. 5 %) of the third.

In 1803, John Dalton proposed Dalton's Law, which describes relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture.

The important properties of shielding gases are their thermal conductivity and heat transfer properties, their density relative to air, and how easy they undergo ionization.

Says he, `` I may never imagine that in the struggle between personal and supra-personal responsibility it is possible to make a compromise between the ethical and the purposive in the shape of a relative ethic ; ;

A relative newcomer in outdoor signs is Mylar polyester film, now used as a printed overlay for trans-illuminated signs ( see below ).

The result of the observations is Af where the phase angle, Q, is measured in degrees from new moon and the probable errors include absolute as well as relative errors.

There is another means which should show the direction and relative value of the stresses in viscoelastic fluids that is not mentioned as such in the literature, and that is the shape of the suspended drops of low viscosity fluids in shear fields.

The relative forces can be calculated from the various radii of curvature if we assume: ( A ) The surface tension is uniform on the surface of the drop.

The last column shows the rate of exchange that would have been observed at a relative intensity of 4 ( 14.7 cm. distance ) calculated on the assumptions that the incident light intensity is inversely proportional to the square of the distance of the lamp from the cell and that the rate is directly proportional to the incident light intensity.

If such is the case, the particles within a distance of about Af of the Earth will have, relative to the Earth, a kinetic energy less than their potential energy and they will be captured into orbits about the Earth.

One issue that must be faced is the relative difficulty of analysis of different phonologic subsystems.

For the purposes of this discussion, the problem of relative prices is encompassed in these two variables, since GNP includes other prices.

This is stated to emphasize the necessity for an over-all concept of submarine defense, one which would provide positions of relative importance to ASW elements based on projected potentialities.

The concept of unity, in which positive and negative are attributes of the same force, in which good and evil are relative, ever-changing, and always joined to the same phenomenon -- such a concept is still reserved to the physical sciences and to the few who have grasped the history of ideas.

To understand American politics is, simply, to know people, to know the relative weight of names -- who are heroes, who are straw men, who controls, who does not.

Thus, giving grades and promotions based only on an individual's performance relative to a small local group, as is common, may reduce cooperative behaviors in the group.

This is the notion that particular cultures should not be judged by one culture's values or viewpoints, but that all cultures should be viewed as relative to each other.

The last stage in the development of the Kouros type is the late archaic period ( 520 – 485 BC ), in which the Greek sculpture attained a full knowledge of human anatomy and used to create a relative harmonious whole.

The emphasis is given in anatomy, and it is one of the first attempts to represent a kind of motion, and beauty relative to proportions, which appear mostly in post-Archaic art.

In the Pollard script, an abugida, vowels are indicated by diacritics, but the placement of the diacritic relative to the consonant is modified to indicate the tone.

Following each individual brick should be a layer of adobe mortar, recommended to be at least an inch thick to make certain there is ample strength between the brick ’ s edges and also to provide a relative moisture barrier during the seasons where the arid climate does produce rain.

This means that the programmer must know a " language " that is effective relative to the target computing agent ( computer / computor ).

This is particularly bad if the standard deviation is small relative to the mean.