Definitions of Screening


The sieve is a tool formed by a ring that has a mesh. This utensil is used to ahecha : clean grains or seeds. By using the screen, it is possible to remove unwanted solid substances that are mixed with the grains.

When the grains are made to pass through the sieve, it is possible to separate the smaller elements from the larger ones thanks to the mesh. This removes impurities that are not useful. When screening wheat, for example, chaff can be excluded.

The screen mesh holes have different sizes according to their use. This feature depends on what is to be removed: if you want to remove dust, to cite one case, the openings must be tiny.

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The simplest sieve model is also known by other names, such as juera, zaranda, harnero and cribo. Its ring is wide but shallow, and it is made of wood. As mentioned above, hole sizes vary depending on the use of the tool, as well as the type of grain intended to be made. The material that is usually used for the bottom of the screen is rawhide, and this is the part that is drilled.

In Spain, for example, there was a profession called ahachador. These people had several sieves, each with holes of different sizes and layouts, and they carried out their work for third parties. Briefly, the procedure consisted of taking the grain little by little, in small amounts that were easy to process, and resting the sieve against the waist and then moving from side to side with the body, until finally hitting the In a circular motion, they tilted her forward and suddenly pushed her away.

Far from being arbitrary, this co-ordinated movement brought together the unwanted parts lighter than the wheat at the front edge of the sieve, so that when jerked aside, raised and lowered, they fell to the ground while on the sieve the good grain remained. Needless to say, this task was difficult to master, requiring a lot of practice and precision, as well as great physical endurance to repeat for several hours.

The idea of ​​screening also has other meanings. In the field of botany, the septa found in certain plant vessels is called sieve. These partitions have holes that are crossed by the sap.

Screening, on the other hand, is a selection process that is characterized by its rigor. For example: “After four months of exams, I managed to pass the screening: I am now part of the National Institute of Technological Sciences”, “Those who manage to pass the screening will join the professional staff”, “In this organization there is no screening, everyone is welcome”.

In the context of mathematics, sieves are algorithms used for factoring integers into prime factors. The Eratosthenes sieve and the Atkin sieve are some of these algorithms.

The algorithm called the Eratosthenes sieve allows all the prime numbers that are below a given one to be thrown, which must belong to the set of natural numbers (those that are used to count elements, that is, they are positive integers). It begins with 2 and a table is made that ends at that limit, which is represented by the letter n.

The Atkin sieve is based on the Eratosthenes sieve but offers a certain degree of optimization. It has the same objective as the previous one and avoids some steps, although it adds others.