Design and development.

Origins.

The idea for a Soviet armored ground-attack aircraft dates to the early 1930s, when Dmitry Pavlovich Grigorovich designed TSh-1 and TSh-2 armored biplanes. However, Soviet engines at the time lacked the power needed to provide the heavy aircraft with good performance. Il-2 was designed by Sergey Ilyushin and his team at the Central Design Bureau in 1938. TsKB-55 was a two-seat aircraft with an armoured shell weighing 700 kg (1,540 lb), protecting crew, engine, radiators, and the fuel tank. Standing loaded, the Ilyushin weighed more than 4,700 kg (10,300 lb), making the armoured shell about 15% of the aircraft's gross weight. Uniquely for a World War II attack aircraft, and similarly to the forward fuselage design of the World War I-era Imperial German Junkers J.I armored, all-metal biplane, the Il-2's armor was designed as a load-bearing part of the Ilyushin's monocoque structure, thus saving considerable weight. The prototype TsKB-55, which first flew on 2 October 1939, won the government competition against the Sukhoi Su-6 and received the VVS designation BSh-2 (the BSh stood for ""Bronirovani Shturmovik"" or armoured ground attack). The prototypes – TsKB-55 and TskB-57 – were built at Moscow plant #39, at that time the Ilyushin design bureau's base.  The BSh-2 was overweight and underpowered, with the original Mikulin AM-35 1,022 kW (1,370 hp) engine designed to give its greatest power outputs at high altitude. Because of this it was redesigned as the TsKB-57, a lighter single-seat design, with the more powerful 1,254 kW (1,680 hp) Mikulin AM-38 engine, a development of the AM-35 optimised for low level operation. The TsKB-57 first flew on 12 October 1940. The production aircraft passed State Acceptance Trials in March 1941, and was redesignated Il-2 in April. Deliveries to operational units commenced in May 1941.  The armament of Il-2 was subject to a competition. One of the first 1940 photographs of the Il-2 show it equipped with two MP-6 23 mm autocannons developed by Yakov Taubin () at OKB-16. The MP-6 gun weighed 70 kg and developed an initial muzzle velocity of 900 m/s. It operated on the short recoil principle and had a rate of fire of about 600 rpm. (The development of the MP-6 gun can be traced back to 1937. The initial version was tested in the spring of 1940 on a Bf 110 bought from Germany, because there was no suitable Soviet aircraft on which to mount it. In the summer of 1940 it was tested on the Pashinin I-21.) Factory trials of the MP-6 gun on the Il-2 were conducted in August 1940. In the early Il-2 prototypes, these guns were fed by 81-round clips. In flight, these clips sometimes became dislodged because of their large surface, which caused them to experience significant aerodynamic pressure. Competitive tests were conducted in the spring of 1941 between the MP-6 gun modified to belt-fed and the newly developed, gas-operated Volkov-Yartsev VYa-23, which had otherwise rather similar characteristics. The VYa-23 was declared the winner at this trial. Subsequently, in May 1941, development of the MP-6 gun was terminated and Taubin was arrested and summarily executed in October that year.

Technical description.

The Il-2 is a single-engine, propeller-driven, low-wing monoplane of mixed construction with a crew of two (one in early versions), specially designed for assault operations. Its most notable feature was the inclusion of armor in an airframe load-bearing scheme. Armor plates replaced the frame and paneling throughout the nacelle and middle part of the fuselage, and an armored hull made of riveted homogeneous armor steel AB-1 (AB-2) secured the aircraft's engine, cockpit, water and oil radiators, and fuel tanks.

Production.

In early 1941, the Il-2 was ordered into production at four factories, and was eventually produced in greater numbers than any other military aircraft in aviation history, but by the time Nazi Germany invaded the Soviet Union on 22 June 1941, only State Aviation Factory 18 at Voronezh and Factory 381 at Leningrad had commenced production, with 249 having been built by the time of the German attack.  Production early in the war was slow because after the German invasion the aircraft factories near Moscow and other major cities in western Russia had to be moved east of the Ural Mountains. Ilyushin and his engineers had time to reconsider production methods, and two months after the move Il-2s were again being produced. The tempo was not to Premier Stalin's liking, however, and he issued the following telegram to Shenkman and Tretyakov:  As a result, "the production of Shturmoviks rapidly gained speed. Stalin's notion of the Il-2 being 'like bread' to the Red Army took hold in Ilyushin's aircraft plants and the army soon had their Shturmoviks available in quantity."

Operational history.

Initial use and operational confusion.

The first use in action of the Il-2 was with the 4th ShAP (Ground Attack Regiment) over the Berezina River days after German invasion began. The aircraft was so new that the pilots had no training in flight characteristics or tactics, and the ground crew no training in servicing or re-arming. The training received enabled the pilots only to take-off and land; none of the pilots had fired the armament, let alone learned tactics. There were 249 Il-2s available on 22 June 1941. In the first three days, 4th ShAP had lost 10 Il-2s to enemy action, a further 19 were lost to other causes, and 20 pilots were killed. By 10 July, 4th ShAP was down to 10 aircraft from a strength of 65.

New tactics.

Tactics improved as Soviet aircrews became used to the Il-2's strengths. Instead of a low horizontal straight approach at 50 metres altitude, the target was usually kept to the pilot's left and a turn and shallow dive of 30 degrees was used, using an echeloned assault by four to twelve aircraft at a time. Although the Il-2's RS-82 and RS-132 rockets could destroy armored vehicles with a single hit, they were so inaccurate that experienced Il-2 pilots mainly used the cannon. Another potent weapon of the Il-2s was the PTAB shaped charge bomblets ("protivotankovaya aviabomba", "anti-tank aviation bomb"). They were designated PTAB-2.5-1.5, as they had a total weight of 2.5 kg (5.5 lb), and an explosive charge of 1.5 kg (3.3 lb). Up to 192 were carried in four external dispensers (cluster bombs) or up to 220 in the inner wing panels' internal ventral weapon bays. The HEAT charge could easily penetrate the relatively thin upper armor of all heavy German tanks. PTABs were first used on a large scale in the Battle of Kursk.  The Il-2 was thereafter widely deployed on the Eastern Front. The aircraft could fly in low light conditions and carried weapons able to defeat the thick armor of the Panther and Tiger I tanks.

Effectiveness as attack aircraft.

The true capabilities of the Il-2 are difficult to determine from existing documentary evidence. W. Liss in "Aircraft profile 88: Ilyushin Il-2" mentions an engagement during the Battle of Kursk on 7 July 1943, in which 70 tanks from the German 9th Panzer Division were claimed to be destroyed by Ilyushin Il-2s in just 20 minutes. In another report of the action on the same day, a Soviet staff publication states that: In the Battle of Kursk (Operation Citadel), General V. Ryazanov became a master in the use of attack aircraft "en masse", developing and improving the tactics of Il-2 operations in co-ordination with infantry, artillery and armored troops. Il-2s at Kursk used the "circle of death" tactic: up to eight Shturmoviks formed a defensive circle, each plane protecting the one ahead with its forward machine guns, while individual Il-2s took turns leaving the circle, attacking a target, and rejoining the circle. Ryazanov was later awarded the Gold Star of Hero of Soviet Union twice, and the 1st Assault Aviation Corps under his command became the first unit to be awarded the honorific title of Guards. In 1943, one loss corresponded to 26 Shturmovik sorties. About half of those lost were shot down by fighters, the rest falling to anti-aircraft fire.  Other studies of the fighting at Kursk suggest that very few of German armour losses were caused by the IL-2 or any other Soviet aircraft. In fact, total German tank losses in Operation Citadel amounted to 323 totally destroyed, the vast majority to anti-tank guns and armored fighting vehicles. In addition it is difficult to find any first-hand accounts by German panzer crews on the Eastern Front describing anything more than the occasional loss to direct air attack. The vast majority, around 95–98%, of tank losses were due to enemy anti-tank guns, tanks, mines, artillery, and infantry assault, or simply abandoned as operational losses (such as mechanical breakdown or running out of fuel), which mostly happened during the last eleven months of the war.  During the Battle of Kursk, VVS Il-2s claimed the destruction of no less than 270 tanks (and 2,000 men) in a period of just two hours against the 3rd Panzer Division. On 1 July, however, the 3rd Panzer Division's 6th Panzer Regiment had just 90 tanks, 180 less than claimed as destroyed. On 11 July (well after the battle), the 3rd Panzer Division still had 41 operational tanks. The 3rd Panzer Division continued fighting throughout July, mostly with 48th Panzer Corps. It did not record any extraordinary losses to air attack throughout this period. As with the other panzer divisions at Kursk, the large majority of the 3rd Panzer Division's tank losses were due to dug-in Soviet anti-tank guns and tanks.  Perhaps the most extraordinary claim by the VVS's Il-2s is that, over a period of four hours, they destroyed 240 tanks and in the process virtually wiped out the 17th Panzer Division. On 1 July, the 17th Panzer Division had only one tank battalion (the II./Pz Rgt 39), with 67 tanks, 173 less than claimed destroyed by the VVS. The 17th Panzer Division was not even in the main attack sector, but further south with the 1st Panzer Army's 24th Panzer Corps. The 17th Panzer did not register any abnormal losses due to aircraft in the summer of 1943, and retreated westwards with Army Group South later in the year, still intact.  The main problem with the Il-2 was the inaccuracy of its attacks. Towards the end of war, the Soviets were able to concentrate large numbers of Shturmoviks to support their main offensives. The effect, however, was often more psychological than actual physical destruction of targets, particularly against dug-in and armored targets. In the 9 June offensive in the Karelian Isthmus in Finland, the Finnish anti-aircraft forces were far too few in number to counter the armadas of Pe-2 and Il-2, but they quickly found that the Il-2 attacks generally missed their marks widely, particularly with bombs. While some attacks against large unprotected targets such as horse and truck convoys and railyards had devastating results, attacks against dug-in point targets were usually ineffective. The frequent duels between dug-in 20 and 40 mm AA guns and Il-2 attackers never resulted in the complete destruction of the gun, while many Il-2s were brought down in these attacks.  The heavy armor of the Il-2 also meant that it would typically carry only comparatively light bomb-loads, which together with the poor accuracy of its attacks made it a far less deadly attack aircraft than contemporary Allied fighter-bombers such as the Republic P-47 Thunderbolt and Hawker Typhoon. The rocket projectiles especially were not effective, even the larger RS-132 (of which four were carried) having a warhead with only of explosives, which compared poorly with the P-47's typical load of ten 5 inch (13 cm) HVARs, each having a warhead, or the 8 to 12 "60 lb" (27 kg) warheads of the Hawker Typhoon's RP-3 rockets. Likewise, the Shturmovik's bombs were usually only 50 kg (rarely 100 kg), too small to compensate for the typically wide variation from the target point. To compensate for the poor accuracy of the Il-2's bombsight, in 1943, the Soviet Command decided to use shaped-charge armor-piercing projectiles against enemy armored vehicles, and the PTAB-2.5-1.5 SCAP aircraft bomb was put into production. These small-calibre bombs were loaded directly into the bomb bays and were dropped onto enemy vehicles from altitudes up to 100 meters (328 ft). As each Il-2 could carry up to 192 bombs, a "fire carpet" 70 meters (229 ft.) long and 15 meters (49 ft) wide could cover the enemy tanks, giving a high "kill" probability. Pilots of 291st ShAP were the first to use the PTAB-2.5-1.5 bombs. During one sortie on 5 June 1943, six attack aircraft led by Lt. Col. A. Vitrook destroyed 15 enemy tanks in one attack, and during five days of the enemy advance, the 291st Division claimed to have destroyed or damaged 422 enemy tanks.

"The Flying tank".

Thanks to the heavy armor protection, the Il-2 could take a great deal of punishment and proved difficult for both ground and aircraft fire to shoot down.  A major threat to the Il-2 was German ground fire. In postwar interviews, Il-2 pilots reported 20 mm (0.79 in) and 37 mm (1.46 in) artillery as the primary threat. While the fabled 88 mm (3.46 in) calibre gun was formidable, low-flying Il-2s presented too fast-moving a target for the 88's relatively low rate of fire, only occasional hits were scored. Similarly the attempts in Finland during the summer of 1944 to augment the small numbers of 20/40 mm AA in the field army by heavier 76 mm guns drawn from homeland defence proved also relatively ineffective and few Il-2s were downed despite attempting different tactics with time-fused fragmentation, contact-fused, and shrapnel ammunition: the heavy guns simply lacked the reaction times to take advantage of the brief firing opportunities presented by the low-altitude Il-2 attacks. Single-barrel 20 mm anti-aircraft guns were also found somewhat inadequate due to limited firepower: one or two shells were often not enough to destroy the Il-2, and unless the Il-2 was attacking the gun itself, thus presenting effectively a stationary target, scoring more hits during a firing opportunity was rare.  The armored tub, ranging from 5–12 mm (0.2–0.5 in) in thickness and enveloping the engine and the cockpit, could deflect all small arms fire and glancing blows from larger-caliber ammunition. Unfortunately the rear gunners did not have the benefit of all-around armor protection, especially from the rear and to the sides, and suffered about four times the casualties of pilots. Added casualties resulted from the Soviet policy of not returning home with unused ammunition which typically resulted in repeated passes on the target. Soviet troops often requested additional passes even after the aircraft were out of ammunition to exploit the intimidating effect Il-2s had on German ground troops, who gave it the nickname "The Flying Tank". "Luftwaffe" pilots called it "Zementbomber" (Concrete bomber). The Finnish nickname "maatalouskone" ("agricultural machine" or "tractor") derived from a word play with "maataistelukone" (ground attack aircraft, literally "ground combat aircraft" where "kone", literally "machine", in turn is shortened from "lentokone", aircraft, literally "flying machine")

Rear gunner.

Heavy losses to enemy fighters forced the reintroduction of a rear gunner; early Il-2s were field modified by cutting a hole in the fuselage behind the cockpit for a gunner sitting on a canvas sling armed with a 12.7 mm UBT machine gun in an improvised mounting. The semi-turret gun mount allowed the machine gun to be fired at angles of up to 35° upwards, 35° to starboard and 15° to port. Tests showed that maximum speed decreased by between 10 and 20 km/h (6.2–12.4 mph) and that the two-seater was more difficult to handle because the center of gravity was shifted backwards. At the beginning of March 1942, a production two-seat Il-2 with the new gunner's cockpit began manufacturer tests. The second cockpit and armament increased all-up weight by 170 kg (374 lb) so the flaps were allowed to be deployed at an angle of 17° to avoid an over-long takeoff run. The new variant had a lengthened fuselage compartment with an extended canopy offering some protection from the elements. Unlike the well-armoured cockpit of the pilot compartment with steel plating up to 12 mm (0.47 in) thick behind, beneath and on both sides as well as up to 65 mm thick glass sections, the rear gunner was provided with 6 mm (.23 in) thick armour, effective only against rifle-calibre rounds.  To improve performance, the Mikulin Design Bureau started work on an uprated AM-38 engine. The new engines produced 1,700 hp at takeoff and 1,500 hp at 750 meters. They gave an improved takeoff and low-altitude performance. On 30 October 1942, production Il-2s powered by AM38s were used on the Central Front for the first time when they successfully attacked Smolensk airfield occupied by Germans. The "Shturmovik" rear guns proved to be effective against hostile fighters, and during the service trials alone, gunners shot down seven Bf 109s and repulsed many attacks. In January 1943 two-seat attack aircraft powered by uprated AM-38F engines ("Forseerovannyy" – uprated) began to arrive at front line units.  Nonetheless, the death rate among the air gunners remained exceptionally high and it was only for late models produced after 1944 that the 13 mm (.5 in) rear plate of the armour shell was moved rearwards into the (wooden) rear fuselage to allow a gunner to sit behind the fuel tank. The armour did not extend to the rear or below although side armour panels were riveted to the rear armour plate to protect the ammunition tank for the UBT machine gun, providing some measure of protection. The modifications including adding the rear gunner and gun had added weight behind the center of gravity, resulting in "marginal" stability and handling characteristics that were "barely acceptable". The need to shift the aerodynamic center of the aircraft rearwards due to the weight of the added rear gunner and lengthened cockpit was the reason for the swept back outer wings in later Il-2s.

Air-to-air combat.

Owing to a shortage of fighters, in 1941–1942, Il-2s were occasionally used as fighters. While outclassed by dedicated fighters such as the Messerschmitt Bf 109 and Focke-Wulf Fw 190, in dogfights, the Il-2 could take on other "Luftwaffe" aircraft with some success. German front line units equipped with the Henschel Hs 126 suffered most of all from the ravages of Il-2s. Il-2 pilots also often attacked close formations of Junkers Ju 87s, as the 7.92 mm machine guns of the "Ju 87 Stukas" were ineffective against the heavily armoured "Shturmoviks". In the winter of 1941–1942, Il-2s were used against "Luftwaffe" transport aircraft, and became the most dangerous opponent of the Junkers Ju 52/3m. Pilots of 33rd GvShAP were the most successful in these operations. Other successful units were those in 1942–1943 operating near Stalingrad. Their targets were not only Ju 52s but also Heinkel He 111 and Focke-Wulf Fw 200 Condor bombers, delivering supplies to the besieged German troops.  While the Il-2 was a deadly air-to-ground weapon, and even a fairly effective interceptor against slow bombers and transport aircraft, heavy losses resulted from its vulnerability to fighter attack. Losses were very high, the highest of all types of Soviet aircraft, though given the numbers in service this is only to be expected. "Shturmovik" losses (including Il-10 type), in 1941–1945, were of 10,762 aircraft (533 in 1941, 1,676 in 1942, 3,515 in 1943, 3,347 in 1944 and 1,691 in 1945). The main defensive tactic was to fly low and reduce power as the fighter closed in. This could make the fighter overshoot and fly into the Il-2's firing zone.  During the Battle in Karelian Isthmus, Vyborg Offensive in summer 1944, Finnish 24th and 34th Fighter Squadrons and Luftwaffe II./JG 54 took a toll on Soviet Il-2 squadrons. In just 30 days (10 June – 9 July) Finnish and German fighter pilots shot down 111 and 53 Il-2s respectively.

Notable aircrew.

Senior Lieutenant Anna Yegorova piloted 243 Il-2 missions and was decorated three times. One of these awards was the Gold Star of Hero of the Soviet Union that she had received "posthumously" in late 1944, since she was presumed dead after being shot down. She survived imprisonment in a German POW camp.  Guards Junior Lieutenant Ivan Grigorevich Drachenko, another Il-2 pilot, was one of only four men who was awarded the title Hero of the Soviet Union and who was also a Full Cavalier of the Order of Glory as a recipient of each of the Order of Glory's three classes. Despite having lost his right eye as a result of injuries sustained in a combat mission on August 14, 1943, he returned to flying status and continued to fly combat sorties until war's end.  Recipient of the "Hero of the Soviet Union", T. Kuznetsov, survived the crash of his Il-2 in 1942 when shot down returning from a reconnaissance mission. Kuznetsov escaped from the wreck and hid nearby. To his surprise, a German Bf 109 fighter landed near the crash site and the pilot began to investigate the wrecked Il-2, possibly to assist Kuznetsov, or to look for souvenirs. Thinking quickly, Kuznetsov ran to the German fighter and used it to fly home, barely avoiding being shot down by Soviet fighters in the process.  Lt. Col. Nelson Stepanyan flew an Il-2 and took part in a number of aerial battles and bombing sorties. He was shot down once but did return to the Soviet lines. On his final sortie in Liepāja, Latvia on 14 December 1944, his plane was hit by anti-aircraft fire, and although wounded, he flew his airplane into a German warship. Soviet sources assert that Stepanyan flew no fewer than 239 combat sorties, sank 53 ships, thirteen of which he did alone, destroyed 80 tanks, 600 armored vehicles, and 27 aircraft.

Variants.

The early two-seater prototype proved to be too heavy for the limited power of the early AM-35 engine. A redesigned single-seat version was soon developed and saw combat, particularly in the early phase of the war in the Soviet Union. While the Il-2 proved to be a deadly air-to-ground weapon, heavy losses were caused by its vulnerability to fighter attack. Consequently, in February 1942, the two-seat design was revived. The Il-2M, with a rear gunner under the stretched canopy, entered service in September 1942 with the surviving single-seaters eventually modified to this standard. Later changes included an upgrade from 20 mm to 23 mm or 37 mm cannons, aerodynamic improvements, use of wooden outer wing panels instead of metal and increased fuel capacity. In 1943, the Il-2 Type 3 or Il-2m3 came out with redesigned "arrow-wings" that possessed leading edges that were swept back 15 degrees on the outer panels, and nearly straight trailing edges, resulting in a wing planform somewhat like the AT-6 trainer. Performance and handling were much improved from the resulting shift of the Il-2's aerodynamic center rearwards with the revised "arrow wing" planform to correct the earlier problem, and this became the most common version of the Il-2. A radial engine powered variant of the Il-2 with the Shvetsov ASh-82 engine was proposed in 1942 to remedy projected shortages in the Mikulin inline engines. However, the ASh-82 was also used in the new Lavochkin La-5 fighter which effectively secured all available engines to the Lavochkin bureau. The radial engine Sukhoi Su-2 ground attack aircraft was produced in small quantities, but was generally considered unsuitable due to inadequate performance and lack of defensive armament.

The Ilyushin Il-2 (Cyrillic: Илью́шин Ил-2) Shturmovik (Cyrillic: Штурмови́к, "Shturmovík") was a ground-attack aircraft produced by the Soviet Union in large numbers during the Second World War. With 36,183 units of the Il-2 produced during the war, and in combination with its successor, the Ilyushin Il-10, a total of 42,330 were built, making it the single most produced military aircraft design in aviation history, as well as one of the most produced piloted aircraft in history along with the American postwar civilian Cessna 172 and the Soviet Union's own then-contemporary Polikarpov Po-2 "Kukuruznik" multipurpose biplane.

L'Iliouchine Il-2 "Chtourmovik" (ou "Šturmovik", en russe : Ильюшин ИЛ-2 Штурмовик) était l'un des meilleurs avions d'attaque au sol de la Seconde Guerre mondiale et il fut produit par l'URSS en grande quantité : plus de, ce qui est le record absolu de production pour un appareil militaire. Il fut surnommé « Le Bossu » par les Soviétiques et « La Mort Noire » par les Allemands.


Etymology.

The city's original name is unknown. Based on his analysis of a Mohenjo-daro seal, Iravatham Mahadevan speculates that the city's ancient name could have been "Kukkutarma" ("the city ["-rma"] of the cockerel ["kukkuta"]"). Cock-fighting may have had ritual and religious significance for the city, with domesticated chickens bred there for sacred purposes, rather than as a food source. Mohenjo-daro may also have been a point of diffusion for the eventual worldwide domestication of chickens.  Mohenjo-daro, the modern name for the site, has been variously interpreted as "Mound of the Dead Men" in Sindhi, and as "Mound of Mohan" (where Mohan is Krishna).

Location.

Mohenjo-daro is located west of the Indus River in Larkana District, Sindh, Pakistan, in a central position between the Indus River and the Ghaggar-Hakra River. It is situated on a Pleistocene ridge in the middle of the flood plain of the Indus River Valley, around from the town of Larkana. The ridge was prominent during the time of the Indus Valley Civilization, allowing the city to stand above the surrounding flood, but subsequent flooding has since buried most of the ridge in silt deposits. The Indus still flows east of the site, but the Ghaggar-Hakra riverbed on the western side is now dry.

Historical context.

Mohenjo-daro was built in the 26th century BCE. It was one of the largest cities of the ancient Indus Valley Civilization, also known as the Harappan Civilization, which developed around 3,000 BCE from the prehistoric Indus culture. At its height, the Indus Civilization spanned much of what is now Pakistan and North India, extending westwards to the Iranian border, south to Gujarat in India and northwards to an outpost in Bactria, with major urban centers at Harappa, Mohenjo-daro, Lothal, Kalibangan, Dholavira and Rakhigarhi. Mohenjo-daro was the most advanced city of its time, with remarkably sophisticated civil engineering and urban planning. When the Indus civilization went into sudden decline around 1900 BCE, Mohenjo-daro was abandoned.

Rediscovery and excavation.

The ruins of the city remained undocumented for around 3,700 years until R. D. Banerji, an officer of the Archaeological Survey of India, visited the site in 1919–20 identifying what he thought to be a Buddhist stupa (150–500 CE) known to be there and finding a flint scraper which convinced him of the site's antiquity. This led to large-scale excavations of Mohenjo-daro led by Kashinath Narayan Dikshit in 1924–25, and John Marshall in 1925–26. In the 1930s major excavations were conducted at the site under the leadership of Marshall, D. K. Dikshitar and Ernest Mackay. Further excavations were carried out in 1945 by Mortimer Wheeler and his trainee, Ahmad Hasan Dani. The last major series of excavations were conducted in 1964 and 1965 by George F. Dales. After 1965 excavations were banned due to weathering damage to the exposed structures, and the only projects allowed at the site since have been salvage excavations, surface surveys, and conservation projects. In the 1980s, German and Italian survey groups led by Michael Jansen and Maurizio Tosi used less invasive archeological techniques, such as architectural documentation, surface surveys, and localized probing, to gather further information about Mohenjo-daro. A dry core drilling conducted in 2015 by Pakistan's National Fund for Mohenjo-daro revealed that the site is larger than the unearthed area.

Architecture and urban infrastructure.

Mohenjo-daro has a planned layout with rectilinear buildings arranged on a grid plan. Most were built of fired and mortared brick; some incorporated sun-dried mud-brick and wooden superstructures. The covered area of Mohenjo-daro is estimated at 300 hectares. The "Oxford Handbook of Cities in World History" offers a "weak" estimate of a peak population of around 40,000.  The sheer size of the city, and its provision of public buildings and facilities, suggests a high level of social organization. The city is divided into two parts, the so-called Citadel and the Lower City. The Citadel – a mud-brick mound around high – is known to have supported public baths, a large residential structure designed to house about 5,000 citizens, and two large assembly halls. The city had a central marketplace, with a large central well. Individual households or groups of households obtained their water from smaller wells. Waste water was channeled to covered drains that lined the major streets. Some houses, presumably those of more prestigious inhabitants, include rooms that appear to have been set aside for bathing, and one building had an underground furnace (known as a hypocaust), possibly for heated bathing. Most houses had inner courtyards, with doors that opened onto side-lanes. Some buildings had two stories.

Major buildings.

In 1950, Sir Mortimer Wheeler identified one large building in Mohenjo-daro as a "Great Granary". Certain wall-divisions in its massive wooden superstructure appeared to be grain storage-bays, complete with air-ducts to dry the grain. According to Wheeler, carts would have brought grain from the countryside and unloaded them directly into the bays. However, Jonathan Mark Kenoyer noted the complete lack of evidence for grain at the "granary", which, he argued, might therefore be better termed a "Great Hall" of uncertain function. Close to the "Great Granary" is a large and elaborate public bath, sometimes called the Great Bath. From a colonnaded courtyard, steps lead down to the brick-built pool, which was waterproofed by a lining of bitumen. The pool measures long, wide and deep. It may have been used for religious purification. Other large buildings include a "Pillared Hall", thought to be an assembly hall of some kind, and the so-called "College Hall", a complex of buildings comprising 78 rooms, thought to have been a priestly residence.

Fortifications.

Mohenjo-daro had no series of city walls, but was fortified with guard towers to the west of the main settlement, and defensive fortifications to the south. Considering these fortifications and the structure of other major Indus valley cities like Harappa, it is postulated that Mohenjo-daro was an administrative center. Both Harappa and Mohenjo-daro share relatively the same architectural layout, and were generally not heavily fortified like other Indus Valley sites. It is obvious from the identical city layouts of all Indus sites that there was some kind of political or administrative centrality, but the extent and functioning of an administrative center remains unclear.

Water supply and wells.

The location of Mohenjo-daro was built in a relatively short period of time, with the water supply system and wells being some of the first planned constructions.

Flooding and rebuilding.

The city also had large platforms perhaps intended as defense against flooding. According to a theory first advanced by Wheeler, the city could have been flooded and silted over, perhaps six times, and later rebuilt in the same location. For some archaeologists, it was believed that a final flood that helped engulf the city in a sea of mud brought about the abandonment of the site. Gregory Possehl was the first to theorize that the floods were caused by overuse and expansion upon the land, and that the mud flood was not the reason the site was abandoned. Instead of a mud flood wiping part of the city out in one fell swoop, Possehl coined the possibility of constant mini-floods throughout the year, paired with the land being worn out by crops, pastures, and resources for bricks and pottery spelled the downfall of the site.

Notable artefacts.

Numerous objects found in excavation include seated and standing figures, copper and stone tools, carved seals, balance-scales and weights, gold and jasper jewellery, and children's toys. Many bronze and copper pieces, such as figurines and bowls, have been recovered from the site, showing that the inhabitants of Mohenjo-daro understood how to utilize the lost wax technique. The furnaces found at the site are believed to have been used for copperworks and melting the metals as opposed to smelting. There even seems to be an entire section of the city dedicated to shell-working, located in the northeastern part of the site. Some of the most prominent copperworks recovered from the site are the copper tablets which have examples of the untranslated Indus script and iconography. While the script has not been cracked yet, many of the images on the tablets match another tablet and both hold the same caption in the Indus language, with the example given showing three tablets with the image of a mountain goat and the inscription on the back reading the same letters for the three tablets. Pottery and terracotta sherds have been recovered from the site, with many of the pots having deposits of ash in them, leading archeologists to believe they were either used to hold the ashes of a person or as a way to warm up a home located in the site. These heaters, or braziers, were ways to heat the house while also being able to be utilized in a manner of cooking or straining, while others solely believe they were used for heating. Many important objects from Mohenjo-daro are conserved at the National Museum of India in Delhi and the National Museum of Pakistan in Karachi. In 1939, a representative collection of artefacts excavated at the site was transferred to the British Museum by the Director-General of the Archaeological Survey of India.

Mother Goddess Idol.

Discovered by John Marshall in 1931, the idol appears to mimic certain characteristics that match the Mother Goddess belief common in many early Near East civilizations. Sculptures and figurines depicting women have been observed as part of Harappan culture and religion, as multiple female pieces were recovered from Marshall's archaeological digs. These figures were not categorized correctly, according to Marshall, meaning that where they were recovered from the site is not actually clear. One of said figures, pictured below, is 18.7 cm tall and is currently on display at the National Museum of Pakistan, in Karachi. The fertility and motherhood aspects on display on the idols is represented by the female genitalia that is presented in an almost exaggerated style as stated by Marshall, with him inferring that such figurines are offerings to the goddess, as opposed to the typical understanding of them being idols representing the goddess's likeness. Because of the figurines being unique in terms of hairstyles, body proportions, as well as headdresses and jewelry, there are theories as to who these figurines actually represent. Shereen Ratnagar theorizes that because of their uniqueness and dispersed discovery throughout the site that they could be figurines of ordinary household women, who commissioned these pieces to be used in rituals or healing ceremonies to help aforementioned individual women.

Dancing Girl.

A bronze statuette dubbed the "Dancing Girl", high and about 4,500 years old, was found in 'HR area' of Mohenjo-daro in 1926; it is now in the National Museum, New Delhi. In 1973, British archaeologist Mortimer Wheeler described the item as his favorite statuette:"She's about fifteen years old I should think, not more, but she stands there with bangles all the way up her arm and nothing else on. A girl perfectly, for the moment, perfectly confident of herself and the world. There's nothing like her, I think, in the world."  John Marshall, another archeologist at Mohenjo-daro, described the figure as "a young girl, her hand on her hip in a half-impudent posture, and legs slightly forward as she beats time to the music with her legs and feet." The archaeologist Gregory Possehl said of the statuette, "We may not be certain that she was a dancer, but she was good at what she did and she knew it". The statue led to two important discoveries about the civilization: first, that they knew metal blending, casting and other sophisticated methods of working with ore, and secondly that entertainment, especially dance, was part of the culture.

Priest-King.

In 1927, a seated male soapstone figure was found in a building with unusually ornamental brickwork and a wall-niche. Though there is no evidence that priests or monarchs ruled Mohenjo-daro, archaeologists dubbed this dignified figure a "Priest-King." The sculpture is tall, and shows a neatly bearded man with pierced earlobes and a fillet around his head, possibly all that is left of a once-elaborate hairstyle or head-dress; his hair is combed back. He wears an armband, and a cloak with drilled trefoil, single circle and double circle motifs, which show traces of red. His eyes might have originally been inlaid.

Pashupati seal.

A seal discovered at the site bears the image of a seated, cross-legged and possibly ithyphallic figure surrounded by animals. The figure has been interpreted by some scholars as a yogi, and by others as a three-headed "proto-Shiva" as "Lord of Animals".

Seven-stranded necklace.

Sir Mortimer Wheeler was especially fascinated with this artifact, which he believed to be at least 4,500 years old. The necklace has an S-shaped clasp with seven strands, each over 4 ft long, of bronze-metal bead-like nuggets which connect each arm of the "S" in filigree. Each strand has between 220 and 230 of the many-faceted nuggets, and there are about 1,600 nuggets in total. The necklace weighs about 250 grams in total, and is presently held in a private collection in India.

Conservation and current state.

An initial agreement to fund restoration was agreed through the United Nations Educational, Scientific, and Cultural Organization (UNESCO) in Paris on 27 May 1980. Contributions were made by a number of other countries to the project:  Preservation work for Mohenjo-daro was suspended in December 1996 after funding from the Pakistani government and international organizations stopped. Site conservation work resumed in April 1997, using funds made available by the UNESCO. The 20-year funding plan provided $10 million to protect the site and standing structures from flooding. In 2011, responsibility for the preservation of the site was transferred to the government of Sindh.  Currently the site is threatened by groundwater salinity and improper restoration. Many walls have already collapsed, while others are crumbling from the ground up. In 2012, Pakistani archaeologists warned that, without improved conservation measures, the site could disappear by 2030.

2014 Sindh Festival.

The Mohenjo-daro site was further threatened in January 2014, when Bilawal Bhutto Zardari of the Pakistan People's Party chose the site for Sindh Festival's inauguration ceremony. This would have exposed the site to mechanical operations, including excavation and drilling. Farzand Masih, head of the Department of Archaeology at Punjab University warned that such activity was banned under the Antiquity Act, saying "You cannot even hammer a nail at an archaeological site." On 31 January 2014, a case was filed in the Sindh High Court to bar the Sindh government from continuing with the event. The festival was held by PPP at the historic site, despite all the protest by both national and international historians and educators.

Climate.

Mohenjo-daro has a hot desert climate (Köppen climate classification "BWh") with extremely hot summers and mild winters. The highest recorded temperature is, and the lowest recorded temperature is. Rainfall is low, and mainly occurs in the monsoon season (July–September).

Mohenjo-daro (; ", "meaning 'Mound of the Dead Men'; ) is an archaeological site in the province of Sindh, Pakistan. Built around 2500 BCE, it was one of the largest settlements of the ancient Indus Valley Civilisation, and one of the world's earliest major cities, contemporaneous with the civilizations of ancient Egypt, Mesopotamia, Minoan Crete, and Norte Chico. Mohenjo-daro was abandoned in the 19th century BCE as the Indus Valley Civilization declined, and the site was not rediscovered until the 1920s. Significant excavation has since been conducted at the site of the city, which was designated a UNESCO World Heritage Site in 1980. The site is currently threatened by erosion and improper restoration.

Mohenjo-daro est un site important de la civilisation de la vallée de l'Indus, on y trouve les vestiges d'une des plus grandes cités de l'âge du bronze indien. Il est situé au Pakistan à 300 km au nord-nord-est de Karâchi.


History.

A process of osmosis through semipermeable membranes was first observed in 1748 by Jean-Antoine Nollet. For the following 200 years, osmosis was only a phenomenon observed in the laboratory. In 1950, the University of California at Los Angeles first investigated desalination of seawater using semipermeable membranes. Researchers from both University of California at Los Angeles and the University of Florida successfully produced fresh water from seawater in the mid-1950s, but the flux was too low to be commercially viable until the discovery at University of California at Los Angeles by Sidney Loeb and Srinivasa Sourirajan at the National Research Council of Canada, Ottawa, of techniques for making asymmetric membranes characterized by an effectively thin "skin" layer supported atop a highly porous and much thicker substrate region of the membrane. John Cadotte, of FilmTec Corporation, discovered that membranes with particularly high flux and low salt passage could be made by interfacial polymerization of "m"-phenylene diamine and trimesoyl chloride. Cadotte's patent on this process was the subject of litigation and has since expired. Almost all commercial reverse-osmosis membrane is now made by this method. By the end of 2001, about 15,200 desalination plants were in operation or in the planning stages, worldwide.  In 1977 Cape Coral, Florida became the first municipality in the United States to use the RO process on a large scale with an initial operating capacity of 11.35 million liters (3 million US gal) per day. By 1985, due to the rapid growth in population of Cape Coral, the city had the largest low-pressure reverse-osmosis plant in the world, capable of producing 56.8 million liters (15 million US gal) per day (MGD).  Formally, reverse osmosis is the process of forcing a solvent from a region of high solute concentration through a semipermeable membrane to a region of low-solute concentration by applying a pressure in excess of the osmotic pressure. The largest and most important application of reverse osmosis is the separation of pure water from seawater and brackish waters; seawater or brackish water is pressurized against one surface of the membrane, causing transport of salt-depleted water across the membrane and emergence of potable drinking water from the low-pressure side.  The membranes used for reverse osmosis have a dense layer in the polymer matrix—either the skin of an asymmetric membrane or an interfacially polymerized layer within a thin-film-composite membrane—where the separation occurs. In most cases, the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high-concentration side of the membrane, usually 2–17 bar (30–250 psi) for fresh and brackish water, and 40–82 bar (600–1200 psi) for seawater, which has around 27 bar (390 psi) natural osmotic pressure that must be overcome. This process is best known for its use in desalination (removing the salt and other minerals from sea water to produce fresh water), but since the early 1970s, it has also been used to purify fresh water for medical, industrial and domestic applications.

Fresh water applications.

Drinking water purification.

Around the world, household drinking water purification systems, including a reverse osmosis step, are commonly used for improving water for drinking and cooking.  Such systems typically include a number of steps: The latest developments in the sphere include nano materials and membranes.  In some systems, the carbon prefilter is omitted, and a cellulose triacetate membrane is used. CTA (cellulose triacetate) is a paper by-product membrane bonded to a synthetic layer and is made to allow contact with chlorine in the water. These require a small amount of chlorine in the water source to prevent bacteria from forming on it. The typical rejection rate for CTA membranes is 85–95%.  The cellulose triacetate membrane is prone to rotting unless protected by chlorinated water, while the thin film composite membrane is prone to breaking down under the influence of chlorine. A thin film composite (TFC) membrane is made of synthetic material, and requires chlorine to be removed before the water enters the membrane. To protect the TFC membrane elements from chlorine damage, carbon filters are used as pre-treatment in all residential reverse osmosis systems. TFC membranes have a higher rejection rate of 95–98% and a longer life than CTA membranes.  Portable reverse osmosis water processors are sold for personal water purification in various locations. To work effectively, the water feeding to these units should be under some pressure (280 kPa (40 psi) or greater is the norm). Portable reverse osmosis water processors can be used by people who live in rural areas without clean water, far away from the city's water pipes. Rural people filter river or ocean water themselves, as the device is easy to use (saline water may need special membranes). Some travelers on long boating, fishing, or island camping trips, or in countries where the local water supply is polluted or substandard, use reverse osmosis water processors coupled with one or more ultraviolet sterilizers.  In the production of bottled mineral water, the water passes through a reverse osmosis water processor to remove pollutants and microorganisms. In European countries, though, such processing of natural mineral water (as defined by a European directive) is not allowed under European law. In practice, a fraction of the living bacteria can and do pass through reverse osmosis membranes through minor imperfections, or bypass the membrane entirely through tiny leaks in surrounding seals. Thus, complete reverse osmosis systems may include additional water treatment stages that use ultraviolet light or ozone to prevent microbiological contamination.  Membrane pore sizes can vary from 0.1 to 5,000 nm depending on filter type. Particle filtration removes particles of 1 μm or larger. Microfiltration removes particles of 50 nm or larger. Ultrafiltration removes particles of roughly 3 nm or larger. Nanofiltration removes particles of 1 nm or larger. Reverse osmosis is in the final category of membrane filtration, hyperfiltration, and removes particles larger than 0.1 nm.

Decentralized use: solar-powered reverse osmosis.

A solar-powered desalination unit produces potable water from saline water by using a photovoltaic system that converts solar power into the required energy for reverse osmosis. Due to the extensive availability of sunlight across different geographies, solar-powered reverse osmosis lends itself well to drinking water purification in remote settings lacking an electricity grid. Moreover, Solar energy overcomes the usually high-energy operating costs as well as greenhouse emissions of conventional reverse osmosis systems, making it a sustainable freshwater solution compatible to developing contexts. For example, a solar-powered desalination unit designed for remote communities has been successfully tested in the Northern Territory of Australia.  While the intermittent nature of sunlight and its variable intensity throughout the day makes PV efficiency prediction difficult and desalination during night time challenging, several solutions exist. For example, batteries, which provide the energy required for desalination in non-sunlight hours can be used to store solar energy in daytime. Apart from the use of conventional batteries, alternative methods for solar energy storage exist. For example, thermal energy storage systems solve this storage problem and ensure constant performance even during non-sunlight hours and cloudy days, improving overall efficiency.

Military use: the reverse osmosis water purification unit.

A reverse osmosis water purification unit (ROWPU) is a portable, self-contained water treatment plant. Designed for military use, it can provide potable water from nearly any water source. There are many models in use by the United States armed forces and the Canadian Forces. Some models are containerized, some are trailers, and some are vehicles unto themselves.  Each branch of the United States armed forces has their own series of reverse osmosis water purification unit models, but they are all similar. The water is pumped from its raw source into the reverse osmosis water purification unit module, where it is treated with a polymer to initiate coagulation. Next, it is run through a multi-media filter where it undergoes primary treatment by removing turbidity. It is then pumped through a cartridge filter which is usually spiral-wound cotton. This process clarifies the water of any particles larger than 5 μm and eliminates almost all turbidity.  The clarified water is then fed through a high-pressure piston pump into a series of vessels where it is subject to reverse osmosis. The product water is free of 90.00–99.98% of the raw water's total dissolved solids and by military standards, should have no more than 1000–1500 parts per million by measure of electrical conductivity. It is then disinfected with chlorine and stored for later use.  Within the United States Marine Corps, the reverse osmosis water purification unit has been replaced by both the Lightweight Water Purification System and Tactical Water Purification Systems. The Lightweight Water Purification Systems can be transported by Humvee and filter per hour. The Tactical Water Purification Systems can be carried on a Medium Tactical Vehicle Replacement truck, and can filter per hour.

Water and wastewater purification.

Rain water collected from storm drains is purified with reverse osmosis water processors and used for landscape irrigation and industrial cooling in Los Angeles and other cities, as a solution to the problem of water shortages.  In industry, reverse osmosis removes minerals from boiler water at power plants. The water is distilled multiple times. It must be as pure as possible so it does not leave deposits on the machinery or cause corrosion. The deposits inside or outside the boiler tubes may result in under-performance of the boiler, reducing its efficiency and resulting in poor steam production, hence poor power production at the turbine.  It is also used to clean effluent and brackish groundwater. The effluent in larger volumes (more than 500 m/day) should be treated in an effluent treatment plant first, and then the clear effluent is subjected to reverse osmosis system. Treatment cost is reduced significantly and membrane life of the reverse osmosis system is increased.  The process of reverse osmosis can be used for the production of deionized water.  Reverse osmosis process for water purification does not require thermal energy. Flow-through reverse osmosis systems can be regulated by high-pressure pumps. The recovery of purified water depends upon various factors, including membrane sizes, membrane pore size, temperature, operating pressure, and membrane surface area.  In 2002, Singapore announced that a process named NEWater would be a significant part of its future water plans. It involves using reverse osmosis to treat domestic wastewater before discharging the NEWater back into the reservoirs.

Food industry.

In addition to desalination, reverse osmosis is a more economical operation for concentrating food liquids (such as fruit juices) than conventional heat-treatment processes. Research has been done on concentration of orange juice and tomato juice. Its advantages include a lower operating cost and the ability to avoid heat-treatment processes, which makes it suitable for heat-sensitive substances such as the protein and enzymes found in most food products.  Reverse osmosis is extensively used in the dairy industry for the production of whey protein powders and for the concentration of milk to reduce shipping costs. In whey applications, the whey (liquid remaining after cheese manufacture) is concentrated with reverse osmosis from 6% total solids to 10–20% total solids before ultrafiltration processing. The ultrafiltration retentate can then be used to make various whey powders, including whey protein isolate. Additionally, the ultrafiltration permeate, which contains lactose, is concentrated by reverse osmosis from 5% total solids to 18–22% total solids to reduce crystallization and drying costs of the lactose powder.  Although use of the process was once avoided in the wine industry, it is now widely understood and used. An estimated 60 reverse osmosis machines were in use in Bordeaux, France, in 2002. Known users include many of the elite-classed growths (Kramer) such as Château Léoville-Las Cases in Bordeaux.

Maple syrup production.

In 1946, some maple syrup producers started using reverse osmosis to remove water from sap before the sap is boiled down to syrup. The use of reverse osmosis allows about 75–90% of the water to be removed from the sap, reducing energy consumption and exposure of the syrup to high temperatures. Microbial contamination and degradation of the membranes must be monitored.

Low alcohol beer.

When beer at normal alcohol concentration is subject to reverse osmosis, both water and alcohol pass across the membrane more readily than the other components, leaving a "beer concentrate". The concentrate is then diluted with fresh water to restore the non-volatile components to their original intensity.

Hydrogen production.

For small-scale hydrogen production, reverse osmosis is sometimes used to prevent formation of mineral deposits on the surface of electrodes.

Aquariums.

Many reef aquarium keepers use reverse osmosis systems for their artificial mixture of seawater. Ordinary tap water can contain excessive chlorine, chloramines, copper, nitrates, nitrites, phosphates, silicates, or many other chemicals detrimental to the sensitive organisms in a reef environment. Contaminants such as nitrogen compounds and phosphates can lead to excessive and unwanted algae growth. An effective combination of both reverse osmosis and deionization is the most popular among reef aquarium keepers, and is preferred above other water purification processes due to the low cost of ownership and minimal operating costs. Where chlorine and chloramines are found in the water, carbon filtration is needed before the membrane, as the common residential membrane used by reef keepers does not cope with these compounds.  Freshwater aquarists also use reverse osmosis systems to duplicate the very soft waters found in many tropical water bodies. Whilst many tropical fish can survive in suitably treated tap water, breeding can be impossible. Many aquatic shops sell containers of reverse osmosis water for this purpose.

Window cleaning.

An increasingly popular method of cleaning windows is the so-called "water-fed pole" system. Instead of washing the windows with detergent in the conventional way, they are scrubbed with highly purified water, typically containing less than 10 ppm dissolved solids, using a brush on the end of a long pole which is wielded from ground level. Reverse osmosis is commonly used to purify the water.

Landfill leachate purification.

Treatment with reverse osmosis is limited, resulting in low recoveries on high concentration (measured with electrical conductivity) and fouling of the RO membranes. Reverse osmosis applicability is limited by conductivity, organics, and scaling inorganic elements such as CaSO4, Si, Fe and Ba. Low organic scaling can use two different technologies, one is using spiral wound membrane type of module, and for high organic scaling, high conductivity and higher pressure (up to 90 bars) disc tube modules with reverse-osmosis membranes can be used. Disc tube modules were redesigned for landfill leachate purification, that is usually contaminated with high levels of organic material. Due to the cross-flow with high velocity it is given a flow booster pump, that is recirculating the flow over the same membrane surface between 1.5 and 3 times before it is released as a concentrate. High velocity is also good against membrane scaling and allows successful membrane cleaning.

Desalination.

Areas that have either no or limited surface water or groundwater may choose to desalinate. Reverse osmosis is an increasingly common method of desalination, because of its relatively low energy consumption.  In recent years, energy consumption has dropped to around 3 kWh/m, with the development of more efficient energy recovery devices and improved membrane materials. According to the International Desalination Association, for 2011, reverse osmosis was used in 66% of installed desalination capacity (0.0445 of 0.0674 km3/day), and nearly all new plants. Other plants mainly use thermal distillation methods: multiple-effect distillation and multi-stage flash.  Sea-water reverse-osmosis (SWRO) desalination, a membrane process, has been commercially used since the early 1970s. Its first practical use was demonstrated by Sidney Loeb from University of California at Los Angeles in Coalinga, California, and Srinivasa Sourirajan of National Research Council, Canada. Because no heating or phase changes are needed, energy requirements are low, around 3 kWh/m, in comparison to other processes of desalination, but are still much higher than those required for other forms of water supply, including reverse osmosis treatment of wastewater, at 0.1 to 1 kWh/m. Up to 50% of the seawater input can be recovered as fresh water, though lower recoveries may reduce membrane fouling and energy consumption.  Brackish water reverse osmosis refers to desalination of water with a lower salt content than sea water, usually from river estuaries or saline wells. The process is substantially the same as sea water reverse osmosis, but requires lower pressures and therefore less energy. Up to 80% of the feed water input can be recovered as fresh water, depending on feed salinity.  The Ashkelon sea water reverse osmosis desalination plant in Israel is the largest in the world. The project was developed as a build-operate-transfer by a consortium of three international companies: Veolia water, IDE Technologies, and Elran.  The typical single-pass sea water reverse osmosis system consists of:

Pretreatment.

Pretreatment is important when working with reverse osmosis and nanofiltration membranes due to the nature of their spiral-wound design. The material is engineered in such a fashion as to allow only one-way flow through the system. As such, the spiral-wound design does not allow for backpulsing with water or air agitation to scour its surface and remove solids. Since accumulated material cannot be removed from the membrane surface systems, they are highly susceptible to fouling (loss of production capacity). Therefore, pretreatment is a necessity for any reverse osmosis or nanofiltration system. Pretreatment in sea water reverse osmosis systems has four major components:

High pressure pump.

The high pressure pump supplies the pressure needed to push water through the membrane, even as the membrane rejects the passage of salt through it. Typical pressures for brackish water range from 1.6 to 2.6 MPa (225 to 376 psi). In the case of seawater, they range from 5.5 to 8 MPa (800 to 1,180 psi). This requires a large amount of energy. Where energy recovery is used, part of the high pressure pump's work is done by the energy recovery device, reducing the system energy inputs.

Membrane assembly.

The membrane assembly consists of a pressure vessel with a membrane that allows feedwater to be pressed against it. The membrane must be strong enough to withstand whatever pressure is applied against it. Reverse-osmosis membranes are made in a variety of configurations, with the two most common configurations being spiral-wound and hollow-fiber.  Only a part of the saline feed water pumped into the membrane assembly passes through the membrane with the salt removed. The remaining "concentrate" flow passes along the saline side of the membrane to flush away the concentrated salt solution. The percentage of desalinated water produced versus the saline water feed flow is known as the "recovery ratio". This varies with the salinity of the feed water and the system design parameters: typically 20% for small seawater systems, 40% – 50% for larger seawater systems, and 80% – 85% for brackish water. The concentrate flow is at typically only 3 bar / 50 psi less than the feed pressure, and thus still carries much of the high-pressure pump input energy.  The desalinated water purity is a function of the feed water salinity, membrane selection and recovery ratio. To achieve higher purity a second pass can be added which generally requires re-pumping. Purity expressed as total dissolved solids typically varies from 100 to 400 parts per million (ppm or mg/litre)on a seawater feed. A level of 500 ppm is generally accepted as the upper limit for drinking water, while the US Food and Drug Administration classifies mineral water as water containing at least 250 ppm.

Energy recovery.

Energy recovery can reduce energy consumption by 50% or more. Much of the high pressure pump input energy can be recovered from the concentrate flow, and the increasing efficiency of energy recovery devices has greatly reduced the energy needs of reverse osmosis desalination. Devices used, in order of invention, are:

Remineralisation and pH adjustment.

The desalinated water is stabilized to protect downstream pipelines and storage, usually by adding lime or caustic soda to prevent corrosion of concrete-lined surfaces. Liming material is used to adjust pH between 6.8 and 8.1 to meet the potable water specifications, primarily for effective disinfection and for corrosion control. Remineralisation may be needed to replace minerals removed from the water by desalination. Although this process has proved to be costly and not very convenient if it is intended to meet mineral demand by humans and plants. The very same mineral demand that freshwater sources provided previously. For instance water from Israel's national water carrier typically contains dissolved magnesium levels of 20 to 25 mg/liter, while water from the Ashkelon plant has no magnesium. After farmers used this water, magnesium-deficiency symptoms appeared in crops, including tomatoes, basil, and flowers, and had to be remedied by fertilization. Current Israeli drinking water standards set a minimum calcium level of 20 mg/liter. The postdesalination treatment in the Ashkelon plant uses sulfuric acid to dissolve calcite (limestone), resulting in calcium concentration of 40 to 46 mg/liter. This is still lower than the 45 to 60 mg/liter found in typical Israeli fresh water.

Disinfection.

Post-treatment consists of preparing the water for distribution after filtration. Reverse osmosis is an effective barrier to pathogens, but post-treatment provides secondary protection against compromised membranes and downstream problems. Disinfection by means of ultraviolet (UV) lamps (sometimes called germicidal or bactericidal) may be employed to sterilize pathogens which bypassed the reverse-osmosis process. Chlorination or chloramination (chlorine and ammonia) protects against pathogens which may have lodged in the distribution system downstream, such as from new construction, backwash, compromised pipes, etc.

Disadvantages.

Household reverse-osmosis units use a lot of water because they have low back pressure. As a result, they recover only 5 to 15% of the water entering the system. The remainder is discharged as waste water. Because waste water carries with it the rejected contaminants, methods to recover this water are not practical for household systems. Wastewater is typically connected to the house drains and will add to the load on the household septic system. A reverse-osmosis unit delivering 19 L of treated water per day may discharge between 75–340 L of waste water daily. This has a disastrous consequence for mega cities like Delhi where large-scale use of household R.O. devices has increased the total water demand of the already water parched National Capital Territory of India.  Large-scale industrial/municipal systems recover typically 75% to 80% of the feed water, or as high as 90%, because they can generate the high pressure needed for higher recovery reverse osmosis filtration. On the other hand, as recovery of wastewater increases in commercial operations, effective contaminant removal rates tend to become reduced, as evidenced by product water total dissolved solids levels.  Reverse osmosis per its construction removes both harmful contaminants present in the water, as well as some desirable minerals. Modern studies on this matter have been quite shallow, citing lack of funding and interest in such study, as re-mineralization on the treatment plants today is done to prevent pipeline corrosion without going into human health aspect. They do, however link to older, more thorough studies that at one hand show some relation between long-term health effects and consumption of water low on calcium and magnesium, on the other confess that none of these older studies comply to modern standards of research

Waste-stream considerations.

Depending upon the desired product, either the solvent or solute stream of reverse osmosis will be waste. For food concentration applications, the concentrated solute stream is the product and the solvent stream is waste. For water treatment applications, the solvent stream is purified water and the solute stream is concentrated waste. The solvent waste stream from food processing may be used as reclaimed water, but there may be fewer options for disposal of a concentrated waste solute stream. Ships may use marine dumping and coastal desalination plants typically use marine outfalls. Landlocked reverse osmosis plants may require evaporation ponds or injection wells to avoid polluting groundwater or surface runoff.

New developments.

Since the 1970s, prefiltration of high-fouling waters with another larger-pore membrane, with less hydraulic energy requirement, has been evaluated and sometimes used. However, this means that the water passes through two membranes and is often repressurized, which requires more energy to be put into the system, and thus increases the cost.  Other recent developmental work has focused on integrating reverse osmosis with electrodialysis to improve recovery of valuable deionized products, or to minimize the volume of concentrate requiring discharge or disposal.  In the production of drinking water, the latest developments include nanoscale and graphene membranes.  The world's largest RO desalination plant was built in Sorek, Israel, in 2013. It has an output of 624,000 m a day. It is also the cheapest and will sell water to the authorities for US$0.58/m.

Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to remove ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended chemical species as well as biological ones (principally bacteria) from water, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as solvent molecules, i.e., water, HO) to pass freely.

L’osmose inverse est un système de purification de l'eau contenant des matières en solution par un système de filtrage très fin qui ne laisse passer que les molécules d'eau.


Purpose and interpretation.

Dynamics are one of the expressive elements of music. Used effectively, dynamics help musicians sustain variety and interest in a musical performance, and communicate a particular emotional state or feeling.  Dynamic markings are always relative. never indicates a precise level of loudness, it merely indicates that music in a passage so marked should be considerably quieter than. There are many factors affecting the interpretation of a dynamic marking. For instance, the middle of a musical phrase will normally be played louder than the beginning or ending, to ensure the phrase is properly shaped, even where a passage is marked throughout. Similarly, in multi-part music, some voices will naturally be played louder than others, for instance to emphasis the melody and the bass line, even if a whole passage is marked at one dynamic level. Some instruments are naturally louder than others – for instance, a tuba playing "piano" will likely be louder than a guitar playing "fortissimo", while a high-pitched instrument like the piccolo playing in its upper register can usually sound loud even when its actual decibel level is lower than that of other instruments.  Further, a dynamic marking does not necessarily only affect loudness of the music. A "forte" passage is not usually "the same as a "piano" passage but louder". Rather, a musician will often use a different approach to other aspects of expression like timbre or articulation to further illustrate the differences. Sometimes this might also extend to tempo. It's important for a performer to be able to control dynamics and tempo independently, and thus novice musicians are often instructed "don't speed up just because it's getting louder!". However, in some circumstances, a dynamic marking might also indicate a change of tempo.  In some music notation programs, there are default MIDI key velocity values associated with these indications, but more sophisticated programs allow users to change these as needed. These defaults are listed in the following table for some applications, including Apple's Logic Pro 9 (2009-2013), Avid's Sibelius 5 (2007-2009), and musescore.org's MuseScore 3.0 (2019). MIDI specifies the range of key velocities as an integer between 0 and 127:

Dynamic markings.

The two basic dynamic indications in music are:  More subtle degrees of loudness or softness are indicated by:  Use of up to three consecutive s or s is also common:

Changes.

Three Italian words are used to show gradual changes in volume:  Signs sometimes referred to as "hairpins" are also used to stand for these words (See image). If the angle lines open up (), then the indication is to get louder; if they close gradually (), the indication is to get softer. The following notation indicates music starting moderately strong, then becoming gradually stronger and then gradually quieter:  <score lang="lilypond"> </score>  Hairpins are usually written below the staff (or between the two staves in a grand staff), but are sometimes found above, especially in music for singers or in music with multiple melody lines being played by a single performer. They tend to be used for dynamic changes over a relatively short space of time (at most a few bars), while ','and "" are generally used for changes over a longer period. Word directions can be extended with dashes to indicate over what time the event should occur, which may be as long as multiple pages. The word "morendo" ("dying") is also sometimes used for a gradual reduction in dynamics (and tempo).  For greater changes in dynamics,'and'are often used, where the "molto" means "much". Similarly, for more gradual changes'and'are used, where "poco" translates as "a little", or alternatively with "poco a poco" meaning "little by little".  Sudden changes in dynamics may be notated by adding the word "subito" (meaning "suddenly") as a prefix or suffix to the new dynamic notation. "Subito piano ("abbreviated "") ("suddenly soft") indicates that the dynamics quickly, almost abruptly, lower the volume to approximately the range. It is often purposefully used to subvert the listeners expectation and will signify an intimacy expression. Although it uses the "piano" dynamic symbol, the performer has slight freedom in their interpretation, causing it to vary based on the preceding loudness or character of the piece. Accented notes can be notated "sforzando", "sforzato", "forzando" or "forzato" (abbreviated,, or ) ("forcing" or "forced"), or using the sign >, placed above or below the head of the note.  "Sforzando" (or "sforzato", "forzando", "forzato") indicates a forceful accent and is abbreviated as, or. There is often confusion surrounding these markings and whether or not there is any difference in the degree of accent. However, all of these indicate the same expression, depending on the dynamic level, and the extent of the "sforzando" is determined purely by the performer.  The fortepiano notation indicates a "forte" followed immediately by "piano". By contrast, is an abbreviation for "poco forte", literally "a little loud" but (according to Brahms) meaning "with the character of forte, but the sound of piano", though rarely used because of possible confusion with "pianoforte").

Extreme dynamic markings.

While the typical range of dynamic markings is from to, some pieces use additional markings of further emphasis. Extreme dynamic markings imply an extreme range of loudness, or, alternatively, imply an extremely subtle distinction between very small differences of loudness within a normal range. This kind of usage is most common in orchestral works from the late 19th-century onwards. Generally, these markings are supported by the orchestration of the work, with heavy forte markings brought to life by having many loud instruments like brass and percussion playing at once.  In Holst's "The Planets", occurs twice in "Mars" and once in "Uranus", often punctuated by organ. Tchaikovsky marks a bassoon solo (6 s) in his "Pathétique" Symphony and uses in passages of his "1812 Overture" and his Fifth Symphony. The baritone passage "Era la notte" from Verdi's opera "Otello" uses, though the same spot is marked in the full score. Igor Stravinsky used at the end of the finale of the 1919 "Firebird Suite". Sergei Rachmaninoff uses in his Prelude in C, Op. 3 No. 2. Gustav Mahler, in the third movement of his Seventh Symphony, gives the celli and basses a marking of (5 s), along with a footnote directing 'pluck so hard that the strings hit the wood'. On the other extreme, Carl Nielsen, in the second movement of his Fifth Symphony, marked a passage for woodwinds a diminuendo to (5 s), and the original piano version of F. W. Meacham's American Patrol begins at and ends at. György Ligeti uses extreme dynamics in his music: the Cello Concerto begins with a passage marked (8 s) and in his Piano Études Étude No. 9 ("Vertige") ends with a diminuendo to (8 s), while Étude No. 13 ("L'Escalier du Diable") contains a passage marked (6 s) that progresses to a (8 s).

History.

"On Music", one of the "Moralia" attributed to the philosopher Plutarch in the first century AD, suggests that ancient Greek musical performance included dynamic transitions – though dynamics receive far less attention in the text than does rhythm or harmony.  The Renaissance composer Giovanni Gabrieli was one of the first to indicate dynamics in music notation, but dynamics were used sparingly by composers until the late 18th century. J.S. Bach used some dynamic terms, including "forte", "piano", "più piano", and "pianissimo" (although written out as full words), and in some cases it may be that was considered to mean "pianissimo" in this period.  The fact that the harpsichord could play only "terraced" dynamics (either loud or soft, but not in between), and the fact that composers of the period did not mark gradations of dynamics in their scores, has led to the "somewhat misleading suggestion that baroque dynamics are 'terraced dynamics'," writes Robert Donington. In fact, baroque musicians constantly varied dynamics: in 1752, Johann Joachim Quantz wrote that "Light and shade must be constantly introduced... by the incessant interchange of loud and soft." In addition to this, the harpsichord in fact becomes louder or softer depending on the thickness of the musical texture (four notes are louder than two). This allowed composers like J.S. Bach to build dynamics directly into their compositions, without the need for notation.  In the Romantic period, composers greatly expanded the vocabulary for describing dynamic changes in their scores. Where Haydn and Mozart specified six levels ( to ), Beethoven used also and (the latter less frequently), and Brahms used a range of terms to describe the dynamics he wanted. In the slow movement of Brahms's trio for violin, horn and piano (Opus 40), he uses the expressions, "molto piano", and "quasi niente" to express different qualities of quiet. Many Romantic and later composers added'and ', making for a total of ten levels between and.

Relation to audio dynamics.

The introduction of modern recording techniques has provided alternative ways to control the dynamics of music. Dynamic range compression is used to control the dynamic range of a recording, or a single instrument. This can affect loudness variations, both at the micro- and macro scale. In many contexts, the meaning of the term "dynamics" is therefore not immediately clear. To distinguish between the different aspects of dynamics, the term "performed dynamics" can be used to refer to the aspects of music dynamics that is controlled exclusively by the performer.

In music, the dynamics of a piece is the variation in loudness between notes or phrases. Dynamics are indicated by specific musical notation, often in some detail. However, dynamics markings still require interpretation by the performer depending on the musical context: for instance a "piano" (quiet) marking in one part of a piece might have quite different objective loudness in another piece, or even a different section of the same piece. The execution of dynamics also extends beyond loudness to include changes in timbre and sometimes tempo rubato.

Dans la musique occidentale, une nuance est un signe noté sur une partition qui indique l'intensité relative d'une note, d'une phrase, ou encore d'un passage entier d'une œuvre musicale. Les nuances permettent au musicien de restituer la dynamique de l'œuvre lors de son interprétation.


Coupe d'Asie des nations de football 2004

Qualification.

The lowest-ranked 20 teams were placed in 6 preliminary qualifying groups of 3 and one group of 2, with the group winners joining the remaining 21 teams in 7 groups of 4. The top two of each of these groups qualified for the finals in China.  Notes:

Squads.

For a list of all squads that played in the final tournament, see "2004 AFC Asian Cup squads."

First round.

All times are China standard time (UTC+8)

Group A.

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Group B.

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Group C.

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Group D.

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Knockout stage.

Statistics.

Goalscorers.

With five goals, A'ala Hubail and Ali Karimi are the top scorers in the tournament. In total, 96 goals were scored by 58 different players, with two of them credited as own goals.

Awards.

Most Valuable Player  Top scorer  Fair Play Award  Team of the Tournament

Views.

Like other sports events, the Asian Cup 2004 was publicised as evidence of China's economic and athletic progress, being referred to by some as a prelude to the 2008 Summer Olympics. Many Chinese see the tournament as a success and take great pride in having showcased such an important sporting event in advance of the Olympic Games. However, the Japanese media and many other international observers have pointed out bad manners on the part of Chinese fans, and sparse attendance at the tournament, raising questions on China's ability to hold such sporting events.  Throughout the tournament, most Chinese fans in the stadia expressed anti-Japanese sentiments by drowning out the Japanese national anthem, displaying political banners and booing whenever Japan got the ball, regardless of the score or opponent. This was reported by the international media, and was aggravated when Koji Nakata apparently knocked in the ball with his right hand in the final against China. The PRC government responded by calling for restraint and increasing police numbers to maintain order. The Japanese government also called on the PRC to ensure the safety of Japanese fans, while specifically asking Japanese nationals or people of Japanese origin to not display any form of excessive pride, especially wearing Japan national football team uniforms. Despite the Chinese government's campaign, a riot started by Chinese fans broke out near the north gate of the Workers' Stadium, though reports differ as to the extent of the riot. As a result, some media groups have said that displays of "excessive Chinese nationalism during the Beijing 2008 Summer Olympics have become a cause for concern for Chinese officials".

The 2004 AFC Asian Cup was the 13th edition of the men's AFC Asian Cup, a quadrennial international football tournament organised by the Asian Football Confederation (AFC). It was held from 17 July to 7 August 2004 in China. The defending champions Japan defeated China in the final in Beijing.

La Coupe d'Asie des nations 2004 a eu lieu en Chine du 17 juillet au. On assiste à la victoire du Japon (qui bat la Chine en finale: 3-1) qui conserve ainsi son titre acquis en 2000 et rejoint l'Iran et l'Arabie saoudite en remportant son troisième trophée.


Etymology.

The word is documented in English since 1274 (attested in Anglo-Latin from ), and stems from Old French (1168; modern French, see below), itself from medieval Latin, of uncertain origin, perhaps a diminutive of Latin 'pillar, stone barrier'.

Description.

Rather like the lesser punishment called the stocks, the pillory consisted of hinged wooden boards forming holes through which the head and/or various limbs were inserted; then the boards were locked together to secure the captive. Pillories were set up to hold people in marketplaces, crossroads, and other public places. They were often placed on platforms to increase public visibility of the person. Often a placard detailing the crime was placed nearby; these punishments generally lasted only a few hours.  In being forced to bend forward and stick their head and hands out in front of them, offenders in the pillory would have been extremely uncomfortable during their punishment. However, the main purpose in putting criminals in the pillory was to publicly humiliate them. On discovering that the pillory was occupied, people would excitedly gather in the marketplace to taunt, tease and laugh at the offender on display.  Those who gathered to watch the punishment typically wanted to make the offender's experience as unpleasant as possible. In addition to being jeered and mocked, those in the pillory might be pelted with rotten food, mud, offal, dead animals, and animal excrement. Sometimes people were killed or maimed in the pillory because crowds could get too violent and pelt the offender with stones, bricks and other dangerous objects. However, when Daniel Defoe was sentenced to the pillory in 1703 for seditious libel, he was regarded as a hero by the crowd and was pelted with flowers.  The criminal could also be sentenced to further punishments while in the pillory: humiliation by shaving off some or all hair or regular corporal punishment(s), notably flagellation (the pillory serving as the "whipping post") or even permanent mutilation such as branding or having an ear cut off (cropping), as in the case of John Bastwick.  In Protestant cultures (such as in the Scandinavian countries), the pillory would be the worldly part of a church punishment. The delinquent would therefore first serve the ecclesiastical part of his punishment on the pillory bench in the church itself, and then be handed to the worldly authorities to be bound to the Skampåle (literally: "Shame Pole") for public humiliation.

Uses.

In 1816, use of the pillory was restricted in England to punishment for perjury or subornation. The pillory was formally abolished as a form of punishment in England and Wales in 1837, but the stocks remained in use, though extremely infrequently, until 1872. The last person to be pilloried in England was Peter James Bossy, who was convicted of "wilful and corrupt perjury" in 1830. He was offered the choice of seven years' penal transportation or one hour in the pillory, and chose the latter.  In France, time in the "pilori" was usually limited to two hours. It was replaced in 1789 by "exposition", and abolished in 1832. Two types of devices were used:  Like other permanent apparatus for physical punishment, the pillory was often placed prominently and constructed more elaborately than necessary. It served as a symbol of the power of the judicial authorities, and its continual presence was seen as a deterrent, like permanent gallows for authorities endowed with high justice.  In Portugal, it is called "Pelourinho", and there are monuments of great importance because they are known since the Roman times. Usually, they are located on the main square of the town, and/or in front of a major church or a palace. They are made of stone with a column and the top carved. Pelourinhos are considered major local monuments, several clearly bearing the coat of arms of a king or queen. The same is true of its former colonies, notably in Brazil (in its former capital, Salvador, the whole old quarter is known as Pelourinho) and Africa (e.g. Cape Verde's old capital, Cidade Velha), always as symbols of royal power.  In Spain it was called "picota".  The pillory was also in common use in other western countries and colonies, and similar devices were used in other, non-Western cultures. According to one source, the pillory was abolished as a form of punishment in the United States in 1839, but this cannot be entirely true because it was clearly in use in Delaware as recently as 1901. Governor Preston Lea finally signed a bill to abolish the pillory in Delaware in March 1905.  Punishment by whipping-post remained on the books in Delaware until 1972, when it became the last state to abolish it. Delaware was the last state to sentence someone to whipping in 1963; however, the sentence was commuted. The last whipping in Delaware was in 1952.

Similar humiliation devices.

There was a variant (rather of the stocks type), called a barrel pillory, or Spanish mantle, used to punish drunks, which is reported in England and among its troops. It fitted over the entire body, with the head sticking out from a hole in the top. The criminal is put in either an enclosed barrel, forcing him to kneel in his own filth, or an open barrel, also known as "barrel shirt" or "drunkards collar" after the punishable crime, leaving him to roam about town or military camp and be ridiculed and scorned. Although a pillory, by its physical nature, could double as a whipping post to tie a criminal down for public flagellation (as used to be the case in many German sentences to "staupenschlag" ), the two as such are separate punishments: the pillory is a sentence to public humiliation, whipping is an essentially painful corporal punishment. Sometimes a single structure was built with separate locations for the two punishments, with a whipping post on the lower level and a pillory above (see image at right).  When permanently present in sight of prisoners, whipping posts were thought to act as a deterrent against bad behaviour, especially when each prisoner had been subjected to a "welcome beating" on arrival, as in 18th-century Waldheim in Saxony (12, 18 or 24 whip lashes on the bare posterior tied to a pole in the castle courtyard, or by birch rod over the ""bock"", a bench in the corner). Still a different penal use of such constructions is to tie the criminal down, possibly after a beating, to expose him for a long time to the elements, usually without food and drink, even to the point of starvation.

Legacy.

While the pillory has left common use, the image remains preserved in the figurative use, which has become the dominant one, of the verb "to pillory" (attested in English since 1699), meaning "to expose to public ridicule, scorn and abuse", or more generally to humiliate before witnesses.  Corresponding expressions exist in other languages, "e.g.", "clouer au pilori" "to nail to the pillory" in French, or "mettere alla gogna" in Italian, or "poner en la picota" in Spanish. In Dutch it's "aan de schandpaal nagelen" or "aan de kaak stellen", placing even greater emphasis on the predominantly humiliating character as the Dutch word for pillory, "schandpaal", literally meaning "pole of shame".

The pillory is a device made of a wooden or metal framework erected on a post, with holes for securing the head and hands, formerly used for punishment by public humiliation and often further physical abuse. The pillory is related to the stocks.

Un pilori est un poteau ou un dispositif auquel un condamné est attaché temporairement pour être vu du public qui, impressionné, est censé s'efforcer de ne pas se retrouver un jour en pareille situation.


Techniques.

Use reference images to create scenes and characters. This can be as simple as looking at an image to inspire your artwork, or creating character sketches and detailed scenes from different angles to create the basis of a picture book world. Some traditional illustration techniques include watercolor, pen and ink, airbrush art, oil painting, pastels, wood engraving, and linoleum cuts.  John Held, Jr. was an illustrator who worked in a variety of styles and media, including linoleum cuts, pen and ink drawings, magazine cover paintings, cartoons, comic strips, and set design, while also creating fine art with his animal sculptures and watercolor, many established illustrators attended an art school or college of some sort and were trained in different painting and drawing techniques.  Traditional illustration seems to have made a resurgence in the age of social media thanks to social networks like Instagram, Facebook, Pinterest, and YouTube. Currently traditional and digital illustration are both flourishing.  Universities and art schools offer specific courses in illustration (for example in the UK, a BA (Hons) Degree) so this has become a new avenue into the profession. Many illustrators are freelance, commissioned by publishers (of newspapers, books, or magazines) or advertising agencies. Most scientific illustrations and technical illustrations are also known as information graphics. Among the information graphics specialists are medical illustrators who illustrate human anatomy, often requiring many years of artistic and medical training.  A particularly popular medium with illustrators of the 1950s and 1960s was casein, as was egg tempera. The immediacy and durability of these media suited illustration's demands well. The artwork in both types of paint withstood the rigors of travel to clients and printers without damage.  Computer illustration, or digital illustration, is the use of digital tools to produce images under the direct manipulation of the artist, usually through a pointing device, such as a tablet or a mouse.  Computers dramatically changed the industry and today, many cartoonists and illustrators create digital illustrations using computers, graphics tablets, and scanners. Software such as Adobe Illustrator, Adobe Photoshop, Corel Painter, and Affinity Designer are now widely used by those professionals.

An illustrator is an artist who specializes in enhancing writing or elucidating concepts by providing a visual representation that corresponds to the content of the associated text or idea. The illustration may be intended to clarify complicated concepts or objects that are difficult to describe textually, which is the reason illustrations are often found in children's books.

Un illustrateur est un artiste chargé de l'illustration d'un ouvrage. Le terme apparaît au pour désigner tout artiste contribuant à l'ornementation d'une page imprimée, dans le domaine de la presse ou de l'édition. Les domaines d'application sont larges : la littérature, l'histoire, l'actualité, les sciences, la mode, etc. Les illustrateurs sont souvent cités auprès de l'auteur pour et avec lequel ils travaillent.