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Law of definite proportions

In chemistry, the law of definite proportion, sometimes called Proust's law or the law of definite composition, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio and does not depend on its source and method of preparation. For example, oxygen makes up about 8/9 of the mass of any sample of pure water, while hydrogen makes up the remaining 1/9 of the mass. Along with the law of multiple proportions, the law of definite proportions forms the basis of stoichiometry; the law of constant proportion was given by Joseph Proust in 1779. This observation was first made by the English theologian and chemist Joseph Priestley, Antoine Lavoisier, a French nobleman and chemist centered on the process of combustion. I shall conclude by deducing from these experiments the principle I have established at the commencement of this memoir, viz. that iron like many other metals is subject to the law of nature which presides at every true combination, to say, that it unites with two constant proportions of oxygen.

In this respect it does not differ from tin and lead, and, in a word every known combustible. The law of definite proportions might seem obvious to the modern chemist, inherent in the definition of a chemical compound. At the end of the 18th century, when the concept of a chemical compound had not yet been developed, the law was novel. In fact, when first proposed, it was a controversial statement and was opposed by other chemists, most notably Proust's fellow Frenchman Claude Louis Berthollet, who argued that the elements could combine in any proportion; the existence of this debate demonstrates that, at the time, the distinction between pure chemical compounds and mixtures had not yet been developed. The law of definite proportions contributed to, was placed on a firm theoretical basis by, the atomic theory that John Dalton promoted beginning in 1803, which explained matter as consisting of discrete atoms, that there was one type of atom for each element, that the compounds were made of combinations of different types of atoms in fixed proportions.

A related early idea was Prout's hypothesis, formulated by English chemist William Prout, who proposed that the hydrogen atom was the fundamental atomic unit. From this hypothesis was derived the whole number rule, the rule of thumb that atomic masses were whole number multiples of the mass of hydrogen; this was rejected in the 1820s and 30s following more refined measurements of atomic mass, notably by Jöns Jacob Berzelius, which revealed in particular that the atomic mass of chlorine was 35.45, incompatible with the hypothesis. Since the 1920s this discrepancy has been explained by the presence of isotopes. Although useful in the foundation of modern chemistry, the law of definite proportions is not universally true. There exist non-stoichiometric compounds; such compounds follow the law of multiple proportion. An example is the iron oxide wüstite, which can contain between 0.83 and 0.95 iron atoms for every oxygen atom, thus contain anywhere between 23% and 25% oxygen by mass. The ideal formula is FeO, but due to crystallographic vacancies it is about Fe0.95O.

In general, Proust's measurements were not precise enough to detect such variations. In addition, the isotopic composition of an element can vary depending on its source, hence its contribution to the mass of a pure stoichiometric compound may vary; this variation is used in radiometric dating since astronomical, oceanic and deep Earth processes may concentrate some environmental isotopes preferentially. With the exception of hydrogen and its isotopes, the effect is small, but is measurable with modern instrumentation. An additional note: many natural polymers vary in composition when "pure". Polymers are not considered "pure chemical compounds" except when their molecular weight is uniform and their stoichiometry is constant. In this unusual case, they still may violate the law due to isotopic variations

Claysville, Alabama

Claysville is an unincorporated community in Marshall County, United States. Claysville was named in honor of Henry Clay, served as the county seat of Marshall County from 1836 to 1838. During the American Civil War, Claysville became a strategic location, due to the ferry crossing of the Tennessee River. A Union Army garrison was located here during the latter part of the war; the 13th Wisconsin Volunteer Infantry Regiment was stationed here under the command of Colonel William P. Lyon. A post office operated under the name Claysville from 1831 to 1879

Time of Judgment

Time of Judgment is a series of roleplaying game scenario books for the World of Darkness settings of White Wolf Game Studio. These scenarios are presented as the semi-canonical endings of the original World of Darkness, as preparation for the new version of the setting; as the Time of Judgment approaches, vampires cease to exist, werewolves fight their last battle against the Wyrm, mages face their last test. The series ran for four hardback books; each setting received between six potential scenarios. Vampire: Gehenna, released in January 2004, began the Time of Judgment chronicle, providing four different scenarios and tips for Storytellers to end their Vampire: The Masquerade game sessions, its scenarios are. The focus is on character interaction as the Player Characters are among the sole survivors in an abandoned sanctuary, as all other vampiric forms are cleansed, with the Player Characters given a chance to interact with each other and turn to God before 40 Nights are over. "Fair is Foul", which concerns the mythology of Lilith and the struggles of her own descendants against those of her enemy, Caine.

"Nightshade", a large-scale story which follows up on many metaplot hooks such as the rising of the antediluvian and rebirth of Saulot. "Crucible of God", is best described as a post-apocalyptic monster epic, with the antediluvian having rewritten the world to their ideals. Werewolf: Apocalypse, released in February 2004, providing four different scenarios for Werewolf: The Apocalypse game sessions. "The Last Battleground" covered the apocalypse as a great battle, taking place in the spirit realm, where the players would seek for any support before the final battle. "A Tribe Falls" covers what events could occur if one of the existing thirteen tribes fell'to the wyrm', like the Black Spiral Dancer tribe. "Weaver Ascendant" places the Weaver as the source of all problems in the cosmos, throws the characters into conflict with it. "Ragnarok" outlines what would happen if a giant asteroid were to collide with the world, igniting an apocalyptic war with the forces of the Wyrm. Mage: Ascension, released in March 2004, providing five different scenarios for Mage: The Ascension game sessions.

"Judgment", the most metaplot-heavy of the lot, features many current strands, which leads to all characters ascending while the universe becomes one great singularity. "The Revolution Will Be Televised" outlines a civil war in the Technocracy, with a view from the inside. "The Earth Will Shake" outlines what would happen if a giant asteroid were to collide with the world, in a different manner to the event in Werewolf. "A Whimper, Not A Bang" dealt with a threat from an alien lifeform, which had not been mentioned within the game for many years. These creatures are consuming the world's magic, not much affecting humans but producing the extinction of mages. "Hell On Earth" outlined what would happen were the Nephandi to win the battle and bring chaos to the world. World of Darkness: Time of Judgment released in March 2004, covered Changeling: The Dreaming, Demon: The Fallen, Hunter: The Reckoning, Kindred of the East, Mummy: The Resurrection, with each receiving between three and four scenarios.

Orpheus got its final book, End Game in 2004, but it was not considered part of the Time of Judgment. Wraith: The Oblivion had ended in 1999 due to lack of sales. Laws of Judgment ended the Mind's Eye Theatre line of World of Darkness live-action role-playing games. Laws of Judgment is a condensed adaptation of the Time of Judgment books, as well as the final Wraith: The Oblivion book, Ends of Empire. Laws of Judgment omitted the "Rising of Mount Meru" scenario for Kindred of the East, on the grounds that its themes did not fit with those of Mind's Eye Theatre, as well as the entire Demon: The Fallen scenario from World of Darkness: Time of Judgment, as Demon was never adapted to Mind's Eye Theatre format. There are three fiction novels that picture the end of times for Vampire: The Masquerade, Werewolf: The Apocalypse, Mage: The Ascension, respectively; these novels are "Gehenna", "The Last Battle", "Judgment Day". None of these are considered to be the canonical ending of the line, as the storylines are left open for each group to end them as they please.

Sean Riley et al.. Apocalypse. Stone Mountain: White Wolf Game Studio. ISBN 1-58846-323-0 Dean Shomshak et al.. Gehenna. Stone Mountain: White Wolf Game Studio. ISBN 1-58846-246-3 Jackie Cassada et al.. Laws of Judgment. Stone Mountain: White Wolf Game Studio. ISBN 1-58846-521-7

LCR meter

An LCR meter is a type of electronic test equipment used to measure the inductance and resistance of an electronic component. In the simpler versions of this instrument the impedance was measured internally and converted for display to the corresponding capacitance or inductance value. Readings should be reasonably accurate if the capacitor or inductor device under test does not have a significant resistive component of impedance. More advanced designs measure true inductance or capacitance, as well as the equivalent series resistance of capacitors and the Q factor of inductive components; the device under test is subjected to an AC voltage source. The meter measures the voltage across and the current through the DUT. From the ratio of these the meter can determine the magnitude of the impedance; the phase angle between the voltage and current is measured in more advanced instruments. The meter must assume a series model for these two elements. An ideal capacitor has no characteristics other than capacitance, but there are no physical ideal capacitors.

All real capacitors have a little inductance, a little resistance, some defects causing inefficiency. These can be seen as inductance or resistance in series with the ideal capacitor or in parallel with it, and so with inductors. Resistors can have inductance and capacitance as a consequence of the way they are constructed; the most useful assumption, the one adopted, is that LR measurements have the elements in series and that CR measurements have the elements in parallel. Leakage is a special case in capacitors, as the leakage is across the capacitor plates, that is, in series. An LCR meter can be used to measure the inductance variation with respect to the rotor position in permanent magnet machines. Handheld LCR meters have selectable test frequencies of 100 Hz, 120 Hz, 1 kHz, 10 kHz, 100 kHz for top end meters; the display resolution and measurement range capability will change with the applied test frequency since the circuitry is more sensitive or less for a given component as the test frequency changes.

Benchtop LCR meters sometimes have selectable test frequencies of more than 100 kHz. They include options to superimpose a DC voltage or current on the AC measuring signal. Lower end meters might offer the possibility to externally supply these DC voltages or currents while higher end devices can supply them internally. In addition benchtop meters allow the usage of special fixtures to measure SMD components, air-core coils or transformers. Inductance, capacitance and dissipation factor can be measured by various bridge circuits, they involve adjusting variable calibrated elements until the signal at a detector becomes null, rather than measuring impedance and phase angle. Early commercial LCR bridges used a variety of techniques involving the matching or "nulling" of two signals derived from a single source; the first signal was generated by applying the test signal to the unknown and the second signal was generated by using a combination of known-value R and C standards. The signals were summed through a detector.

When zero current was noted by changing the value of the standards and looking for a "null" in the panel meter, it could be assumed that the current magnitude through the unknown was equal to that of the standard and that the phase was the reverse. The combination of standards selected could be arranged to read out C and DF directly, the precise value of the unknown. An example of this is 1621 Capacitance Bridges. ESR meter Q meter "LCR Primer", IET Labs Inc. April 2012

Perfect World Games

Perfect World Games is a Chinese video game developer and video game publisher specializing in massively multiplayer online role-playing games. Perfect World was founded in 2004 by the president of Human Software Corporation; the company aims to market games with Chinese characteristics. Perfect World - 3D MMORPG - January 2006 Legend of Martial Arts - 3D MMORPG - September 2006 Perfect World II - 3D MMORPG - November 2006 Jade Dynasty - 3D MMORPG - May 2007 Chi Bi - 3D MMORPG - January 2008 Hot Dance Party - 3D MMORPG - March 2008 Pocketpet Journey West - 3D MMORPG - October 2008 Battle of the Immortals - 2.5D MMORPG - April 2009 Ether Saga Odyssey - 3D MMORPG - July 2009 Fantasy Zhu Xian - 2D MMORPG - October 2009 Dragon Excalibur - 2D MMORPG - October 2010 Forsaken World - 3D MMORPG - October 2010 Empire of the Immortals - 2.5D MMORPG - Q4 2010 War of the Immortals - 3D MMORPG - December 2012 Neverwinter - 3D MMORPG - June 2013* Swordsman Online - 3D MMORPG - July 2014 Final Fantasy Type-0 Online - Multiplayer action role-playing game for iOS, Android and Windows - 2017 Perfect World Mobile - Mobile MMORPG game for iOS, Android September 2019 Perfect World Entertainment is the company’s North American online games publisher specializing in immersive free-to-play MMORPGs founded in 2008.

Created in early 2010, in Amsterdam, Perfect World Europe focuses on localizing and operating massively multiplayer games in Europe. As of 2011, it has Jade Dynasty as well as Forsaken World in both German. Perfect World II - French, German - 3D MMORPG November 2006 Jade Dynasty - English - 3D MMORPG May 2007 Forsaken World - French, German - 3D MMORPG - October 2010 Star Trek Online - French, German - 3D MMORPG - February 2010 Blacklight: Retribution - 3D MMORPG - April 2012 War of the Immortals - French, German - 3D MMORPG - December 2012 Neverwinter - French, Italian, Polish, Russian - 3D MMORPG - June 2013 Swordsman Online - French, Turkish - 3D MMORPG - July 2014 Perfect World - 3D MMORPG Legend of Martial Arts - 3D MMORPG Zhu Xian - 3D MMORPG Chi Bi - 3D MMORPG Forsaken World - 3D MMORPG Champions Online - 3D MMORPG - September 2009 Tartaros Online - 3D MMORPG Black Shot - 3D Runic Games was a Seattle-based developer founded in 2008, acquired by Perfect World in 2010 and shut down in 2017.

On October 18, 2012, Valve announced an agreement granting Perfect World exclusive rights to market and distribute Dota 2 in mainland China. CEO Robert Hong Xiao stated that his company was "confident that adding this action strategy game to our diverse portfolio of games will bring additional world-class entertainment and premier gaming experiences to our players in China."On February 25, 2016, Perfect World hosted Dota 2's Shanghai Major. While the tournament itself was well received in regards to the player performances, the event garnered criticism due to delays on stream, spotty broadcasts and various other problems within the tournament, including the theft and deterioration of the competing teams' equipment. In the month that followed the event, the president of Perfect World, Yunfan Zhang, apologized for the issues with the event. On September 24, 2017, Valve announced on the Counter-Strike blog that Perfect World would be distributing Counter-Strike: Global Offensive in the Chinese market through the company's service.

On June 12, 2018, Perfect World announced their subsidiary Perfect World Zhengqi would collaborate with Valve and build "Steam China". All games on Steam China will be checked by the Ministry of Culture of the People's Republic of China. Most Steam users criticized Perfect World. China Central Television has mentioned these concerns during their "Live News" on Channel 13. Official website

Spectral efficiency

Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, sometimes by the media access control; the link spectral efficiency of a digital communication system is measured in bit/s/Hz, or, less but unambiguously, in /Hz. It is the net bitrate or maximum throughput divided by the bandwidth in hertz of a communication channel or a data link. Alternatively, the spectral efficiency may be measured in bit/symbol, equivalent to bits per channel use, implying that the net bit rate is divided by the symbol rate or line code pulse rate. Link spectral efficiency is used to analyse the efficiency of a digital modulation method or line code, sometimes in combination with a forward error correction code and other physical layer overhead. In the latter case, a "bit" refers to a user data bit.

The modulation efficiency in bit/s is the gross bitrate divided by the bandwidth. Example 1: A transmission technique using one kilohertz of bandwidth to transmit 1,000 bits per second has a modulation efficiency of 1 /Hz. Example 2: A V.92 modem for the telephone network can transfer 56,000 bit/s downstream and 48,000 bit/s upstream over an analog telephone network. Due to filtering in the telephone exchange, the frequency range is limited to between 300 hertz and 3,400 hertz, corresponding to a bandwidth of 3,400 − 300 = 3,100 hertz; the spectral efficiency or modulation efficiency is 56,000/3,100 = 18.1 /Hz downstream, 48,000/3,100 = 15.5 /Hz upstream. An upper bound for the attainable modulation efficiency is given by the Nyquist rate or Hartley's law as follows: For a signaling alphabet with M alternative symbols, each symbol represents N = log2 M bits. N is the modulation efficiency measured in bpcu. In the case of baseband transmission with a baseband bandwidth B, the symbol rate can not exceed 2B symbols/s in view to avoid intersymbol interference.

Thus, the spectral efficiency can not exceed 2N /Hz in the baseband transmission case. In the passband transmission case, a signal with passband bandwidth W can be converted to an equivalent baseband signal, with upper cut-off frequency W/2. If double-sideband modulation schemes such as QAM, ASK, PSK or OFDM are used, this results in a maximum symbol rate of W symbols/s, in that the modulation efficiency can not exceed N /Hz. If digital single-sideband modulation is used, the passband signal with bandwidth W corresponds to a baseband message signal with baseband bandwidth W, resulting in a maximum symbol rate of 2W and an attainable modulation efficiency of 2N /Hz. Example 3: A 16QAM modem has an alphabet size of M = 16 alternative symbols, with N = 4 bit/symbol or bpcu. Since QAM is a form of double sideband passband transmission, the spectral efficiency cannot exceed N = 4 /Hz. Example 4: The 8VSB modulation scheme used in the ATSC digital television standard gives N=3 bit/symbol or bpcu. Since it can be described as nearly single-side band, the modulation efficiency is close to 2N = 6 /Hz.

In practice, ATSC transfers a gross bit rate of 32 Mbit/s over a 6 MHz wide channel, resulting in a modulation efficiency of 32/6 = 5.3 /Hz. Example 5: The downlink of a V.92 modem uses a pulse-amplitude modulation with 128 signal levels, resulting in N = 7 bit/symbol. Since the transmitted signal before passband filtering can be considered as baseband transmission, the spectral efficiency cannot exceed 2N = 14 /Hz over the full baseband channel; as seen above, a higher spectral efficiency is achieved if we consider the smaller passband bandwidth. If a forward error correction code is used, the spectral efficiency is reduced from the uncoded modulation efficiency figure. Example 6: If a forward error correction code with code rate 1/2 is added, meaning that the encoder input bit rate is one half the encoder output rate, the spectral efficiency is 50% of the modulation efficiency. In exchange for this reduction in spectral efficiency, FEC reduces the bit-error rate, enables operation at a lower signal to noise ratio.

An upper bound for the spectral efficiency possible without bit errors in a channel with a certain SNR, if ideal error coding and modulation is assumed, is given by the Shannon-Hartley theorem. Example 7: If the SNR is 1, corresponding to 0 decibel, the link spectral efficiency can not exceed 1 /Hz for error-free detection according to Shannon-Hartley regardless of the modulation and coding. Note that the goodput is lower than the maximum throughput used in the above calculations, because of packet retransmissions, higher protocol layer overhead, flow control, congestion avoidance, etc. On the other hand, a data compression scheme, such as the V.44 or V.42bis compression used in telephone modems, may however give higher goodput if the transferred data is not efficiently compressed. The link spectral efficiency of a wireless telephony link may be expressed as the maximum number of simultaneous calls over 1 MHz frequency spectrum in erlangs per megahertz, or E/MHz; this measure is affected by the source coding scheme.

It may be applied to analog as well as digital transmission. In wir