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Per Cent Mille
A per cent mille or pcm is one one-thousandth of a percent. It can be thought of as a "milli-percent". It is commonly used in epidemiology, and in nuclear reactor engineering as a unit of reactivity. Epidemiology Statistics of crime rates, mortality and disease prevalence in a population are often given in Nuclear Reactivity In nuclear reactor engineering, a per cent mille is equal to one-thousandth of a percent of the reactivity, denoted by Greek lowercase letter rho. Reactivity is a dimensionless unit representing a departure from criticality, calculated by: :\rho=(k_-1)/k_ where keff denotes the effective multiplication factor for the reaction. Therefore, one pcm is equal to: :1~\text = \rho \cdot 10^5 This unit is commonly used in the operation of light-water reactor sites because reactivity values tend to be small, so measuring in pcm allows reactivity to be expressed using whole numbers. Related units * Percentage point difference of 1 part in 100 * Percentage ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and Risk factor (epidemiology), determinants of health and disease conditions in a defined population, and application of this knowledge to prevent diseases. It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying Risk factor (epidemiology), risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences. Major areas of epidemiological study include disease causation, transmission (medicine), transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percentage
In mathematics, a percentage () is a number or ratio expressed as a fraction (mathematics), fraction of 100. It is often Denotation, denoted using the ''percent sign'' (%), although the abbreviations ''pct.'', ''pct'', and sometimes ''pc'' are also used. A percentage is a dimensionless quantity, dimensionless number (pure number), primarily used for expressing proportions, but percent is nonetheless a unit of measurement in its orthography and usage. Examples For example, 45% (read as "forty-five percent") is equal to the fraction , or 0.45. Percentages are often used to express a proportionate part of a total. (Similarly, one can also express a number as a fraction of 1,000, using the term "per mille" or the symbol "".) Example 1 If 50% of the total number of students in the class are male, that means that 50 out of every 100 students are male. If there are 500 students, then 250 of them are male. Example 2 An increase of $0.15 on a price of $2.50 is an increase by a fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Per-unit System
In the power systems analysis field of electrical engineering, a per-unit system is the expression of system quantities as fractions of a defined base unit quantity. Calculations are simplified because quantities expressed as per-unit do not change when they are referred from one side of a transformer to the other. This can be a pronounced advantage in power system analysis where large numbers of transformers may be encountered. Moreover, similar types of apparatus will have the impedances lying within a narrow numerical range when expressed as a per-unit fraction of the equipment rating, even if the unit size varies widely. Conversion of per-unit quantities to volts, ohms, or amperes requires a knowledge of the base that the per-unit quantities were referenced to. The per-unit system is used in power flow, short circuit evaluation, motor starting studies etc. The main idea of a per unit system is to absorb large differences in absolute values into base relationships. Thus, rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dollar (reactivity)
A dollar is a unit of reactivity for a nuclear reactor, calibrated to the interval between the conditions of criticality and prompt criticality. Prompt criticality will result in an extremely rapid power rise, with the resultant destruction of the reactor, unless it is specifically designed to tolerate the condition. A cent is of a dollar. In nuclear reactor physics discussions, the symbols are often appended to the end of the numerical value of reactivity, such as 3.48$ or 21 ¢. Reactivity (denoted ρ or ΔK/K) is related to the effective neutron multiplication factor (''keff''), the average number of all neutrons from one fission that cause another fission. ρ = But in nuclear physics, it useful to talk about the reactivity contributed by just the prompt neutrons. This is the reactivity in dollars or cents. Reactivity in its most general sense would not be measured in dollars or cents. This is because keff measures the total value of reactivity, a summation of the react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
InHour
InHour is a unit of reactivity of a nuclear reactor. It stands for the inverse of an hour. It is equal to the inverse of the period in hours. One InHour is the amount of reactivity needed to increase the reaction from critical to where the power will increase by a factor of e in one hour. The unit is abbreviated ih or inhr, and is usually measured with a reactimeter. See also *Per cent mille A per cent mille or pcm is one one-thousandth of a percent. It can be thought of as a "milli-percent". It is commonly used in epidemiology, and in nuclear reactor engineering as a unit of reactivity. Epidemiology Statistics of crime rates, mort ... References Units of measurement {{energy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parts-per Notation
In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are * parts-per-million - ppm, * parts-per-billion - ppb, * parts-per-trillion - ppt, * parts-per-quadrillion - ppq, This notation is not part of the International System of Units - SI system and its meaning is ambiguous. Applications Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permyriad
A basis point (often abbreviated as bp, often pronounced as "bip" or "beep") is one hundredth of 1 percentage point. Changes of interest rates are often stated in basis points. For example, if an existing interest rate of 10 percent is increased by 1 basis point, the new interest rate would be 10.01 percent. The related term ''#Permyriad, permyriad'' means one part per ten thousand. Definition :1 basis point (bp) = 0.01%, 10−4, , or 0.0001. :10 bp = 0.1%, 10−3, , or 0.001. :100 bp = 1%, 10−2, , or 0.01. Basis points are used as a convenient unit of measurement in contexts where percentage differences of less than 1% are discussed. The most common example is interest rates, where differences in interest rates of less than 1% per year are usually meaningful to talk about. For example, a difference of 0.10 percentage points is equivalent to a change of 10 basis points (e.g., a 4.67% rate increases by 10 basis points to 4.77%). In other words, an increase of 100 basis points ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permille
The phrase per mille () indicates parts per thousand. The associated symbol is , similar to a per cent sign but with an extra zero in the divisor. Major dictionaries do not agree on the spelling, giving other options of per mil, per mill, permil, permill, permille. The word is the cognate in Dutch, German, Finnish and Swedish, and is sometimes seen as a loanword in English with the same meaning as ''per mille''. (Page 258) The symbol is included in the General Punctuation block of Unicode at .Unicode.General Punctuation. 2014. Accessed 5 Aug 2014. There is also an Arabic-Indic per mille sign at . Examples Blood alcohol concentration Promille and permille are likely best known as shorthand terms for Blood Alcohol Concentration, where 1 promille corresponds to 1 gram of alcohol per liter of blood. Promille is used in the legal limits of blood-alcohol content for driving a road vehicle in some countries: for example: 0.5‰ or 0.8‰. Cost per mille Sales and marketin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percentage Point
A percentage point or percent point is the unit (measurement), unit for the difference (mathematics), arithmetic difference between two percentages. For example, moving up from 40 percent to 44 percent is an increase of 4 percentage points (although it is a 10-percent increase in the quantity being measured, if the total amount remains the same). In written text, the unit (the percentage point) is usually either written out, or abbreviated as ''pp'', ''p.p.'', or ''%pt.'' to avoid confusion with percentage increase or decrease in the actual quantity. After the first occurrence, some writers abbreviate by using just "point" or "points". Differences between percentages and percentage points Consider the following hypothetical example: In 1980, 50 percent of the population smoked, and in 1990 only 40 percent of the population smoked. One can thus say that from 1980 to 1990, the prevalence of smoking decreased by 10 ''percentage points'' (or by 10 percent of the population) or by ''20 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Reactor
A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons production and Research reactor, research. Fissile material, Fissile nuclei (primarily uranium-235 or plutonium-239) absorb single neutron, neutrons and split, releasing energy and multiple neutrons, which can induce further fission. Reactors stabilize this, regulating Neutron absorber, neutron absorbers and neutron moderator, moderators in the core. Fuel efficiency is exceptionally high; Enriched uranium#Low-enriched uranium (LEU), low-enriched uranium is 120,000 times more energy dense than coal. Heat from nuclear fission is passed to a working fluid Nuclear reactor#By coolant, coolant. In commercial reactors, this drives Turbine, turbines and electrical generator shafts. Some reactors are used for district heating, and isotopes, isoto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light-water Reactor
The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron reactors are the most common type of nuclear reactor, and light-water reactors are the most common type of thermal-neutron reactor. There are three varieties of light-water reactors: the pressurized water reactor (PWR), the boiling water reactor (BWR), and (most designs of) the supercritical water reactor (SCWR). History Early concepts and experiments After the discoveries of fission, moderation and of the theoretical possibility of a nuclear chain reaction, early experimental results rapidly showed that natural uranium could only undergo a sustained chain reaction using graphite or heavy water as a moderator. While the world's first reactors ( CP-1, X10 etc.) were successfully reaching criticality, uranium enrichment began to develop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
