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History of Measurement The earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction, and trade. Early standard units might only have applied to a single community or small region, with every area developing its own standards for lengths, areas, volumes and masses. Often such systems were closely tied to one field of use, so that volume measures used, for example, for dry grains were unrelated to those for liquids, with neither bearing any particular relationship to units of length used for measuring cloth or land. With development of manufacturing technologies, and the growing importance of trade between communities and ultimately across the Earth, standardized weights and measures became critical. Starting in the 18th century, modernized, simplified and uniform systems of weights and measures were developed, with the fundamental units defined by ever

Units of Radioactivity The International systems of units (SI) unit of radioactive activity is the becquerel (Bq), named in the honour of the scientist Henri Becquerel. One Bq is defined as one transformation (or decay or disintigration) per second. An older unit of radioactivity is the Curie, Ci, which was originally defined as "the quantity or mass of radium (element) emanation in equillibrium with one gram of radium. Today, curie is defined as 3.7 x 10^10 disintegrations per second, so that 1 curie = 3.7 x 10^10 Bq. The effect of ionizing radiation is often measured in units of grey for mechanical or sievert for damage to tissue. Mathematics of Radioactive Decay: 1. Universal law of Radioactive Decay Radioactive Decay  The law describes the statistical behaviour of a large number of nuclides, rather than individual atoms. In following formalism, the number of nuclides or the nuclide population N, is of course a discrete variable (a natural number) - but for any phy

Half-life of Radioactive Elements  Radioactive decay (also known  nuclear decay or radioactivity) is the process by which an unstable atomic nucleus loses energy (in terms of mass in its rest frame) by emitting radiation, such as an alpthingticle, beta particle with neutrino or only a neutrino in the case of electron capture or electron in the case of internal conversion. A material containing such unstable nuclei is considered  radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, proton emission. Radioactive decay is a stochastic (i.e. random) process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a collection of atoms, the collection's expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating. Th

Mechanics of writing a technical report is explained in a pseudo report format. The purpose of this pseudo report is to explain the contents of a typical engineering report. It can also be used as a template for an actual engineering report. With some adaptation, the format can be extended to other type of technical writings as well. A technical report (also scientific report) is a document that describes the process, progress, or results of technical or scientific research or the state of a technical or scientific research problem. It might also include recommendations and conclusions of the research. Unlike other scientific literature, such as scientific journals and the proceedings of some academic conferences, technical reports rarely undergo comprehensive independent peer review before publication. They may be considered as grey literature. Where there is a review process, it is often limited to within the originating organization. Similarly, there are no formal publishing proc