тема уже была
https://bbs.cs-s.ru/showthread.php?...;threadid=16785
так что давайте лучше поговорим: а зачем же тут такая странная и ненужная кнопочка "поиск"???
вот вырезка, тут даже по русски написано:
..............Português (Portuguese)
n. - meia-vida (f) (Fís.)
Русский (Russian)
период полураспада
Español (Spanish)
n. - media vida................
т
half-life (hăf'līf', häf'-)
n.
Physics. The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.
Biology.
The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes. Also called biological half-life.
The time required for the radioactivity of material taken in by a living organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay.
Encyclopedia
half-life, measure of the average lifetime of a radioactive substance (see radioactivity) or an unstable subatomic particle. One half-life is the time required for one half of any given quantity of the substance to decay. For example, the half-life of a particular radioactive isotope of thorium is 8 minutes. If 100 grams of the isotope are originally present, then only 50 grams will remain after 8 minutes, 25 grams after 16 minutes (2 half-lives), 12.5 grams after 24 minutes (3 half-lives), and so on. Of course the 87.5 grams that are no longer present as the original substance after 24 minutes have not disappeared but remain in the form of one or more other substances in the isotope's radioactive decay series. Individual decays are random and cannot be predicted, but this statistical measure of the great number of atoms in the sample is very accurate. The half-life of a radioactive isotope is a characteristic of that isotope and is not affected by any change in physical or chemical conditions.
Investment
Average Life
An estimate of the number of terms to maturity, taking the possibility of early payments into account. Average life is calculated using the weighted average time to the receipt of all future cash flows.
Investopedia Says: This is often used in sinking funds.
See Also: Duration, Maturity, Principal, Sinking Fund Provision
Science
half-life
In physics, a fixed time required for half the radioactive nuclei in a substance to decay. Half-lives of radioactive substances can range from fractions of a second to billions of years, and they are always the same for a given nucleus, regardless of temperature or other conditions. If an object contains a pound of a radioactive substance with a half-life of fifty years, at the end of that time there will be half a pound of the radioactive substance left undecayed in the object. After another fifty years, a quarter-pound will be left undecayed, and so on.
Scientists can estimate the age of an object, such as a rock, by carefully measuring the amounts of decayed and undecayed nuclei in the object. Comparing that to the half-life of the nuclei tells when they started to decay and, therefore, how old the object is. (See radioactive dating.)
Medical
half-life
n.
The time required for half the nuclei of a specific radionuclide or radioactive substance to undergo radioactive decay. Also called physical half-life.
The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes. Also called biological half-life.
The time required for the radioactivity of material taken in by or administered to an organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay. Also called effective half-life.
Cosmic Lexicon
Half-life
The amount of time required for half of the mass of a radioactive isotope to decay.
WordNet
Note: click on a word meaning below to see its connections and related words.
The noun half-life has one meaning:
Meaning #1: the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)
Synonym: half life
Wikipedia
half-life
The half-life of a radioactive substance is the time required for half of a sample to undergo radioactive decay.
More generally, for a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. (This article is a narrow discussion of half-life. For phenomena where half-life is applied, see "Related topics" below.)
After # of
Half-lives Percent of quantity
remaining
0 100%
1 50
2 25
3 12.5
4 6.25
5 3.125
6 1.5625
7 0.78125%
The table at right shows the reduction of the quantity in terms of the number of half-lives elapsed.
Quantities subject to exponential decay are commonly denoted by the symbol N. (This convention suggests a decaying number of discrete items. This interpretation is valid in many, but not all, cases of exponential decay.) If the quantity is denoted by the symbol N, the value of N at a time t is given by the formula:
where
N0 is the initial value of N (at t=0)
λ is a positive constant (the decay constant).
When t=0, the exponential is equal to 1, and N(t) is equal to N0. As t approaches infinity, the exponential approaches zero.
In particular, there is a time such that:
Substituting into the formula above, we have:
Thus the half-life is 69.3% of the mean lifetime.
Related topics
Exponential decay
Mean lifetime
Radioactive decay
Tables of nuclides with color-coding of half-lives:
Isotope table (divided) with
Isotope table (complete)
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations
Translations for: Half-life
Nederlands (Dutch)
halveringstijd (bij radioactiviteit)
Français (French)
période, demi-vie
Deutsch (German)
n. - (Phys.) Halbwertszeit
Ελληνική (Greek)
n. (φυσ.) ημιζωή, (μτφ.) αδράνεια, σκούριασμα
Italiano (Italian)
tempo in cui materiale radioattivo perde metà della sua radioattività, emivita
Português (Portuguese)
n. - meia-vida (f) (Fís.)
Русский (Russian)
период полураспада
Español (Spanish)
n. - media vida
Svenska (Swedish)
n. - halveringstid (fys.)
中国话 (Simplified Chinese)
n. - 半衰期
中國話 (Traditional Chinese)
n. - 半衰期
日本語 (Japanese)
n. - 半減期
العربيه (Arabic)
(الاسم
العمر النصفي, الزمن الضروري لتفكيك نصف ذرات مادة ذات نشاط إشعاعي
עברית (Hebrew)
n. - מחצית חיים (פיזיקה
, הזמן שלוקח לרדיו-אקטיביות או לתכונה אחרת של חומר להיחלש ב-%05
If you are unable to view some languages clearly, click here.
To select your translation preferences click here.
Mentioned In
half life is mentioned in the following topics:
biological half-life actinon
nobelium effective half-life
Hydrogen-6 AMX Half-Life Server Mod
G-Man thoron
Excs-sourceCtl half-life (disambiguation)
More>
Форумы на Наша-Life » Мир Half-Life » Сюжет и устройство вселенной Half-Life » Что означает словосочетание "Half-life"?
24-06-2005 
