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Les jeux vidéo sont-ils une perte de temps

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Les jeux vidéo sont-ils une perte de temps

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Les jeux vidéos sont acceptables jusqu'à ce que vous préfériez jouer à des jeux plutôt que de passer du temps avec votre famille ou vos amis et de prendre soin de votre corps.

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Pourquoi les calculatrices ont été inventées?

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Pourquoi les calculatrices ont été inventées?

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Par désir d'aider son père à percevoir les impôts.

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Mathematician and inventor Blaise Pascal was born in Clermont-Ferrand, France on June 19, 1623. His mother passed away when he and his two sisters were very young, and their father Étienne became solely responsible for their upbringing. Étienne Pascal was a judge of the tax court in Clermont-Ferrand, who moved the family to Paris in part to further the education of his son, who was showing early potential for academic brilliance.

Pascal became interested in geometry at age 12, and taught himself quickly about the properties of figures. His father, personally taught his son at home with the help of tutors, had been reluctant to allow him to study mathematics before age 15, but he recognized his son's exceptional ability in the subject and gave him a copy of the book Euclid's Elements. By age 14, Pascal was meeting weekly with prominent French mathematicians - the group that would form the foundation for the French Academy - and by age 16 he was developing theories, beginning with his essay on conic sections. This work was published in 1640.

In December of 1639, Pascal's father had moved the family to Rouen where he took a job as tax collector for the region. Pascal's invention of the mechanical calculator in the early 1640s was born out of a desire to help his father in collecting taxes. He was the second person known to have created a device of this kind. A company by the name of Schickard had manufactured a type of mechanical calculator in 1624. Until 1645, Pascal worked on improvements to the machine, which was called the Pascaline. It resembled the mechanical calculators of the 1940s.

The French money system presented Pascal with many technological challenges, as there were, at the time, 20 sols in a livre and 12 deniers in a sol. This made his task much more difficult than it would have been if the system was based on factors of 100. Nevertheless, he was able to construct a machine that was reasonably accurate. The Pascaline could only add and subtract; multiplication and division were done using a series of additions and subtractions. The machine had eight movable dials that added up to eight figured long sums. Production of the machines started in 1642. Few machines were sold however, and manufacture ceased ten years later. Pascal worked on many versions of the devices, leading to his attempt to create a perpetual motion machine. He has been credited with introducing the roulette machine, which was a by-product of these experiments.

Meanwhile, Pascal continued to experiment in analytical geometry as well as physics. His father died in 1651, and in 1653 Pascal took over the family's estate. At that time, he began to concentrate fully on developing his theories, creating the arithmetical triangle, and together with Fermat, creating the calculus of probabilities. He also began a series of experiments on atmospheric pressure. He published the "Treatise on the Equilibrium of Liquids" in 1653.

In 1654, Pascal was spared in a near-deadly horse and carriage accident and became extremely religious. He was inspired to write on philosophical topics. Some of these writings have become very well-known, especially his "Provinciales" and "Pensées." He turned away from scientific work for several years, until in 1658 he completed a full account of the geometry of the cycloid. He died of cancer in 1662 at the age of 39, in Port Royal.

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Mathematician and inventor Blaise Pascal was born in Clermont-Ferrand, France on June 19, 1623. His mother passed away when he and his two sisters were very young, and their father Étienne became solely responsible for their upbringing.

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James Russell a créée les CD.

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James T. Russell (born 1931 in Bremerton, Washington) is an American inventor. He earned a BA in physics from Reed College in Portland in 1953. He joined General Electric's nearby labs in Richland, Washington, where he initiated many types of experimental instrumentation. He designed and built the first electron beam welder.

In 1965, Russell joined the Pacific Northwest National Laboratory of Battelle Memorial Institute in Richland. There, in 1965, Russell invented the overall concept of optical digital recording and playback. The earliest patents by Russell, US 3,501,586, and 3,795,902 were filed in 1966, and 1969. respectively. He built prototypes, and the first was operating in 1973. In 1973, 1974, 1975 his first invention viewed by about 100 companies, including Philips and Sony engineers, and more than 1500 descriptive brochures were sent out to various interested parties[citation needed ]. The concept was picked up by many technical and media magazines beginning in 1972[citation needed ].

It is debatable whether Russell's concepts, patents, prototypes, and literature[citation needed ] instigated and in some measure guided the optical digital revolution. Early optical recording technology, which forms the physical basis of videodisc, CD and DVD technology, was first published/filed by Dr. David Paul Gregg in 1958 and Philips researchers, Kramer and Compaan, in 1969. Russell's optical digital inventions were available publicly from 1970.

In 2000, Russell received The Vollum Award from Reed College.

As of 2004, Russell was doing consulting from an in-home lab, in Bellevue, Washington.

Major features of the early Russell patents:

The preferred embodiment of the scanning mechanism is awkward since the disc is not rotating but fixed. A scanning mirror with which the light is deflected is attached to a rotating shaft.

The entire disc or oblong sheet to be read is illuminated by a large playback light source at the back of the transparent plate instead by focused laser light in reflective mode. There is no objective lens for reading the data.

Dynamic track or focus servos are absent.

The patent specification mentions the use of a protective layer(s) or coating to prevent scratching during handling, but the layer does not offer significant benefits, as its task is merely to protect. Fingerprints and scratches will obscure the data read. In a CD, on the other hand, where a focused laser beam is used in conjunction with a protective layer at the reading side of the disc, scratches and fingerprints are out of focus, and thus not detected by the reading spot. As a result, the CD/DVD method offers a great resilience against disc anomalies, offering great playability.

Low information density. According to the patent specifications the spot diameter is around 10 micrometres. Thus, the areal information density is, according to the patent specifications, around a factor hundred less than that of a regular CD. This amounts to a capacity of 5 Mbytes for a disc of 12 cm diameter. The inevitable downside to this is that Russell's disc offers playing time less than one minute of digital CD sound. In case we have digital video at 30 Mbit/s, as claimed above, Russell's disc would be read in less than two seconds. How such extremely fast scanning could be implemented was not disclosed.

Photographically copying of data.

The patents do not address any details of the digital coding techniques used and/or details of methods how to solve the problems associated with extremely high bit rates of digital video signals. Due to limitations of electronics circuitry, there was no (MPEG) source coding at the time to lower the overall bit rates. The uncompressed bit rate of a color video signal is around 200 Mbit/s, and it is far from clear how the mechanical (scanning speed) and electronic challenges imposed by these enormous bit rates were solved. The patents do not mention error correction or other digital coding technology.

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James T. Russell (born 1931 in Bremerton, Washington) is an American inventor. He earned a BA in physics from Reed College in Portland in 1953. He joined General Electric's nearby labs in Richland, Washington, where he initiated many types of experimental instrumentation. He designed and built the first electron beam welder.

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Quand les moniteurs de fréquence cardiaque ont-ils été inventés?

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Quand les moniteurs de fréquence cardiaque ont-ils été inventés?

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Ils ont été créée en l'année 1977

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A heart rate monitor (HRM) is a personal monitoring device that allows one to measure/display heart rate in real time or record the heart rate for later study. It is largely used to gather heart rate data while performing various types of physical exercise. Measuring electrical heart information is referred to as Electrocardiography (ECG or EKG).

Medical heart rate monitoring used in hospitals is usually wired and usually multiple sensors are used. Portable medical units are referred to as a Holter monitor. Consumer heart rate monitors are designed for everyday use and do not use wires to connect.

Early models consisted of a monitoring box with a set of electrode leads which attached to the chest. The first wireless EKG heart rate monitor was invented in 1977 by Polar Electro as a training aid for the Finnish National Cross Country Ski team. As "intensity training" became a popular concept in athletic circles in the mid-80s, retail sales of wireless personal heart monitors started in 1983.

Modern heart rate monitors commonly use one of two different methods to record heart signals (electrical and optical). Both types of signals can provide the same basic heart rate data, using fully automated algorithms to measure heart rate, such as the Pan-Tompkins algorithm.

ECG ( Electrocardiography) sensors measure the bio-potential generated by electrical signals that control the expansion and contraction of heart chambers, typically implemented in medical devices.

PPG ( Photoplethysmography) sensors use a light-based technology to measure the blood volume controlled by the heart's pumping action.

Electrical

The electrical monitors consist of two elements: a monitor/transmitter, which is worn on a chest strap, and a receiver. When a heartbeat is detected a radio signal is transmitted, which the receiver uses to display/determine the current heart rate. This signal can be a simple radio pulse or a unique coded signal from the chest strap (such as Bluetooth, ANT, or other low-power radio links). Newer technology prevents one user's receiver from using signals from other nearby transmitters (known as cross-talk interference) or eavesdropping. Note the older Polar 5.1 kHz radio transmission technology is usable underwater. Both Bluetooth and Ant+ use the 2.4 GHz radio band, which cannot send signals underwater.

More recent devices use optics to measure heart rate by shining light from an LED through the skin and measuring how it scatters off blood vessels. In addition to measuring the heart rate, some devices using this technology are able to measure blood oxygen saturation (). Some recent optical sensors can also transmit data as mentioned above.

Newer devices such as cell phones or watches can be used to display and/or collect the information. Some devices can simultaneously monitor heart rate, oxygen saturation, and other parameters. These may include sensors such as accelerometers, gyroscopes, and GPS to detect speed, location and distance.

In recent years, it has been common for smartwatches to include heart rate monitors, which has greatly increased popularity. Some smart watches, smart bands and cell phones often use PPG sensors.

Fitness metrics

Garmin, Polar Electro, Suunto and Fitbit are vendors selling consumer heart rate products. Most companies use their own proprietary heart rate algorithms.

The newer, wrist based heart rate monitors have achieved almost identical levels of accuracy as their chest strap counterparts with independent tests showing up to 95% accuracy, but sometimes more than 30% error can persist for several minutes. Optical devices can be less accurate when used during vigorous activity or when used underwater.

Currently heart rate variability is less available on optical devices. Apple introduced HRV data collection to the Apple Watch devices in 2018.

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A heart rate monitor (HRM) is a personal monitoring device that allows one to measure/display heart rate in real time or record the heart rate for later study. It is largely used to gather heart rate data while performing various types of physical exercise. Measuring electrical heart information is referred to as Electrocardiography (ECG or EKG).

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Il a été créée dans Atlanta, Géorgie.

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Some scholars credit Dayton, Ohio, native Charles Francis Jenkins and a colleague with inventing the motion picture projector. In 1891, Jenkins worked as a stenographer for the federal government in Washington, DC. In his free time, Jenkins tried to develop a motion picture projector. By 1892, he had succeeded in developing a machine that could project small moving pictures on a wall or screen, but the pictures were too small to be viewed by a large audience.

In 1895, Jenkins entered into a business relationship with Thomas Armat. Together, the two men improved Jenkins's early invention. The two inventors unveiled their projector at the Cotton States Exposition in Atlanta, Georgia, in September 1895. Armat and Jenkins charged people twenty-five cents to view moving pictures, which were projected from the phantoscope, Jenkins's and Armat's projector. Many historians give credit to Jenkins and Armat for also developing the movie theater to show their films at the Cotton States Exposition.

Jenkins's and Armat's relationship did not last. In October, Jenkins took one of the three phantoscopes that the two men had manufactured to Richmond, Indiana, his boyhood home, to show residents his moving pictures. He also filed a patent for the phantoscope, claiming that he was the sole inventor, although an earlier patent claimed that Jenkins and Armat were joint presenters. In the end, the U.S. Patent Office granted Jenkins and Armat the patent, rejecting Jenkins's claim that he was solely responsible for the phantoscope. Angered with the Patent Office's decision, Jenkins continued to say that he had developed the phantoscope in 1894 and projected images for audiences in Richmond, Indiana, as early as June 6, 1894. Jenkins also entered into an agreement with the Columbia Phonograph Company to manufacture the phantoscope. In the meantime, Armat began negotiations to sell the phantoscope patent to Thomas Alva Edison. Jenkins later sold his rights to the phantoscope to Armat, who then sold the rights to Edison.

Thomas Alva Edison's laboratory at West Orange, New Jersey had perfected the motion picture camera and a "peephole" viewer to see motion pictures beginning in 1888. Edison had not followed through with a projection system because the single person viewers were successful. Seeing that a public projection system was needed, Edison acquired the rights to the phantoscope and marketed it as the "Vitascope". In 1896, Edison began selling his own "Projectoscope" or Projecting Kinescope.

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Some scholars credit Dayton, Ohio, native Charles Francis Jenkins and a colleague with inventing the motion picture projector. In 1891, Jenkins worked as a stenographer for the federal government in Washington, DC. In his free time, Jenkins tried to develop a motion picture projector.