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資料更新日期 113-04-26 21:00
Reservoir sampling. Reservoir sampling is a family of randomized algorithms for choosing a simple random sample, without replacement, of k items from a population of unknown size n in a single pass over the items. The size of the population n is not known to the algorithm and is typically too large for all n items to fit into main memory.
Renewable energy, green energy, or low-carbon energy is energy from renewable resources that are naturally replenished on a human timescale. Renewable resources include sunlight, wind, the movement of water, and geothermal heat.[1][2][3][4][5][6][7][excessive citations] Although most renewable energy sources are sustainable, some are not. For ...
Sodium carbonate (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ...
This article is about the physical properties of greenhouse gases. For how human activities are adding to greenhouse gases, see Greenhouse gas emissions. Greenhouse gases trap some of the heat that results when sunlight heats the Earth's surface. Three important greenhouse gases are shown symbolically in this image: carbon dioxide, water vapor ...
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive systems of most animal species, including humans. Hydrochloric acid is an ...
Beaufort scale. A ship in a force 12 (" hurricane -force") storm at sea, the highest rated on the Beaufort scale. The Beaufort scale / ˈboʊfərt / is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale .
The mole (symbol mol) is a unit of measurement, the base unit in the International System of Units (SI) for amount of substance, a quantity proportional to the number of elementary entities of a substance. One mole contains exactly 6.022 140 76 × 10 23 elementary entities (approximately 602 sextillion or 602 billion times a trillion), which can be atoms, molecules, ions, or other particles.
