By the 2000s, the only big difference between a record being a hip hop record or an R&B record is whether its vocals are rapped or sung. R&B started to focus more on solo artists than groups. By 2005, the most famous R&B artists include Usher, Beyoncé (formerly of Destiny's Child), Ashanti, and Mariah Carey.
Soulful R&B continues to be popular, with artists such as Alicia Keys, R. Kelly, John Legend, and Toni Braxton. Some R&B singers have used parts of Caribbean music in their work.
Tungsten
Tungsten (sometimes named wolfram) is a chemical element on the periodic table. It has the chemical symbol W and it has the atomic number 74. It is a steel-gray to white colored metal. In chemistry, it is placed in a group of metal elements named the transition metals. Tungsten is found in several ores, including wolframite and scheelite.
Tungsten has a higher melting point than any other non-alloy that exists. The pure form (only tungsten) is mainly used in electrical equipment. Its compounds and alloys are used for many things, the most well known being its use in electrical filaments for light bulbs. It is also used in the filament and target in most X-ray tubes, superalloys, and in glass-to-metal seals.
Tungsten's density and hardness have many uses. In the military, for example, tungsten has been used in armor-piercing artillery.
Tungsten's density is almost the same as gold. Gold-plated tungsten ingots have been fraudulently passed off as solid gold.
Arc
An arc is a part of a circle. An arc is a curved line. The curve of an arc is constant and does not change (that is, an arc has constant curvature). It sometimes is portrayed as a dotted line.
In a circle, the arc from point A to point B is written as formula_1. We call the length of an arc an arc length. For an arc on a circle with radius "formula_2" subtended by an angle formula_3, its arc length is precisely formula_4.
Particulate
Particulates are very tiny pieces of a solid or liquid that are carried floating in a gas. When the tiny pieces are solid, it is called a smoke. When the tiny pieces are liquid, it is called an aerosol. Aerosols can be naturally found in clouds and geysers. There are also artificial aerosols such as haze and some air pollutants. Smokes can be found naturally in wildfires and volcanoes. Artificially, they can be found in cigarettes, factories and power plants. Both of them can cause air pollution and climate change.
Shorthand
Shorthand or stenography is a way of writing. Shorthand systems allow people to write much faster. Shorthand systems have been in use since antiquity. Now, they are not used as much, because there are dictation machines to record voices.
Sine wave
A sine wave is a curve with this shape:
This is a picture of a sine wave.
All waves can be made by adding up sine waves. The sine wave has a pattern that repeats. The length of this repeating piece of the sine wave is called the wavelength. The wavelength can be found by measuring the length or distance between one peak of a sine wave and the next peak. The wavelength can be found in many other ways too.
Waves are found everywhere in the natural world. Examples of waves:
All of these waves are the sum total of many signals.
Sine waves have a "length" called a wavelength. There are other properties of waves and sine waves, such as their frequency, amplitude, phase, and speed.
Sine waves repeat over time, so this makes them periodic. The time is takes for a part of the sine wave (one cycle) to travel before it repeats itself is called the period, represented by the letter T. The frequency of a sine wave is the number of oscillations it makes in one second. This is measured in Hertz, which have units of s. The frequency can be found by dividing 1/T (this is also called taking the reciprocal).
Collingwood Football Club
Collingwood Football Club, the Magpies, is a club which plays Australian Rules Football in the AFL. It comes from Collingwood, a suburb of Melbourne in Victoria. In the AFL/VFL, it has won 15 premierships.
The Collingwood Football Club was formed in February 1892. Collingwood played its first game in the Victorian Football Association on 7 May 1892, against Carlton. In 1902, Collingwood won its first premiership against the Essendon Football Club.
The Victorian Football League (VFL) formed in 1897. Collingwood was one of the original teams (along with Fitzroy, Melbourne, St Kilda, Carlton, Essendon, South Melbourne and Geelong). In the early years of the VFL, Collingwood was the most successful team; it won 11 premierships in the first 40 years. They won the most recent AFL premiership against St Kilda in 2010. The teams had to play a second match after the scores were equal at the end of the first Grand Final game.
Vibration
Vibration means quickly moving back and forth (or up and down) about a point of equilibrium. The vibration may be periodic (having a pattern) or random. Something that is vibrating may shake at the same time. If it vibrates in a regular way, it may produce a musical note because it can make the air vibrate. This vibration will send sound waves to the ear and to the brain.
In structural engineering including earthquake engineering, vibrations may be bad. They may cause the structure to fail.
The time it takes a vibrating object to go back and forth completely is the period. The number of back-and-forth movements in one second is its frequency, measured in Hertz (Hz). The farthest possible distance from the equilibrium point is the amplitude.
Free vibration occurs when vibration is set off with a push and allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at a 'Natural frequency' and gradually wind down.
Forced vibration is when an alternating force or motion is applied to a mechanical system. Examples of this type of vibration include
In forced vibration the frequency of the vibration is the frequency of the force or motion applied. The size of the effect depends on the actual mechanical system.
Molybdenum
Molybdenum is a chemical element. It has the chemical symbol Mo. It has the atomic number 42. It has 35 isotopes. The name Molybdenum is from the Greek meaning "leadlike". The color of pure molybdenum is silvery-white. It does not occur naturally, and is made from molybdenite.
It is used in alloys with other metals like stainless steel. It helps to make metal stronger, especially in high temperatures, and makes it less likely to rust. This makes it good for use in high speed tools, such as drills and saw blades. It is used in aircraft and missile parts, as well as in nuclear reactors. It is also not toxic, so it is used in making metal bowls for use in making food, medicines and other chemicals.
Molybdenum was used for many years before it was identified in 1778 by Swedish scientist, Carl Wilhelm Scheele. In 1782, Peter Jacob Hjelm was able to separate it into a dark powder he called "molybdenum". It was first mined in 1916 at Climax, near Leadville, in Colorado.
Solution
In chemistry, a solution is a homogeneous mixture of two or more substances. The substances that are dissolved are called solutes. The substance the solutes are dissolved in is called the solvent. An example from everyday experience is a solid like salt or sugar (which are crystalline solids), dissolved in a liquid (like water). Gases can dissolve in liquids. An example is carbon dioxide or oxygen in water. Liquids may dissolve in other liquids and gases in other gases.
The amount of solute added to the solvent determines the concentration of the solution. The solution with the large amount of solute is called a concentrated solution; the solution with less solute is called a dilute solution.
Examples of solid solutions are alloys and some minerals. For example, brass is an alloy of copper and zinc.
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