Pneumatics is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are powered by compressed air or compressed inert gases. A centrally located and electrically powered compressor powers cylinders, air motors, other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to electric motors and actuators. Pneumatics has applications in dentistry, construction and other areas. Pneumatic systems in fixed installations, such as factories, use compressed air because a sustainable supply can be made by compressing atmospheric air; the air has moisture removed, a small quantity of oil is added at the compressor to prevent corrosion and lubricate mechanical components. Factory-plumbed pneumatic-power users need not worry about poisonous leakage, as the gas is just air. Smaller or stand-alone systems can use other compressed gases that present an asphyxiation hazard, such as nitrogen—often referred to as OFN when supplied in cylinders.
Any compressed gas other than air is an asphyxiation hazard—including nitrogen, which makes up 78% of air. Compressed oxygen would not asphyxiate, but is not used in pneumatically-powered devices because it is a fire hazard, more expensive, offers no performance advantage over air. Portable pneumatic tools and small vehicles, such as Robot Wars machines and other hobbyist applications are powered by compressed carbon dioxide, because containers designed to hold it such as soda stream canisters and fire extinguishers are available, the phase change between liquid and gas makes it possible to obtain a larger volume of compressed gas from a lighter container than compressed air requires. Carbon dioxide can be a freezing hazard if vented improperly; the origins of pneumatics can be traced back to the first century when ancient Greek mathematician Hero of Alexandria wrote about his inventions powered by steam or the wind. German physicist Otto von Guericke went a little further, he invented a device that can draw out air or gas from the attached vessel.
He demonstrated. The field of pneumatics has changed over the years, it has moved from small handheld devices to large machines with multiple parts that serve different functions. Both pneumatics and hydraulics are applications of fluid power. Pneumatics uses an compressible gas such as air or a suitable pure gas—while hydraulics uses incompressible liquid media such as oil. Most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch. Hydraulics applications use from 1,000 to 5,000 psi, but specialized applications may exceed 10,000 psi. Simplicity of design and control—Machines are designed using standard cylinders and other components, operate via simple on-off control. Reliability—Pneumatic systems have long operating lives and require little maintenance; because gas is compressible, equipment is less subject to shock damage. Gas absorbs excessive force. Compressed gas can be stored, so machines still run for a while if electrical power is lost. Safety—There is a low chance of fire compared to hydraulic oil.
New machines are overload safe to a certain limit. Liquid does not absorb any of the supplied energy. Capable of moving much higher loads and providing much higher forces due to the incompressibility; the hydraulic working fluid is incompressible, leading to a minimum of spring action. When hydraulic fluid flow is stopped, the slightest motion of the load releases the pressure on the load. Responsive compared to pneumatics. Supply more power than pneumatics. Can do many purposes at one time: lubrication and power transmission. Pneumatic logic systems are sometimes used for controlling industrial processes, consisting of primary logic units like: And Units Or Units'Relay or Booster' Units Latching Units'Timer' Units Fluidics amplifiers with no moving parts other than the air itselfPneumatic logic is a reliable and functional control method for industrial processes. In recent years, these systems have been replaced by electronic control systems in new installations because of the smaller size, lower cost, greater precision, more powerful features of digital controls.
Pneumatic devices are still used where safety factors dominate. Compressed air Ozone cracking - can affect pneumatic seals Pneudraulics History of pneumatic power Brian S. Elliott, Compressed Air Operations Manual, McGraw Hill Book Company, 2006, ISBN 0-07-147526-5. Heeresh Mistry, Fundamentals of Pneumatic Engineering, Create Space e-Publication, 2013, ISBN 1-49-372758-3. Four Ways to Boost Pneumatic Efficiency
The Battle of Onjong known as the Battle of Wenjing, was one of the first engagements between Chinese and United Nations forces during the Korean War. It took place around Onjong in present-day North Korea from 25 to 29 October 1950; as the main focus of the Chinese First Phase Offensive, the People's Volunteer Army 40th Corps conducted a series of ambushes against the Republic of Korea Army II Corps destroying the right flank of the United States Eighth Army while stopping the UN advance north toward the Yalu River. The Korean War began on 25 June 1950 when the North Korean Korean People's Army attacked South Korea; the invasion was successful in conquering all of South Korea until the UN intervened, sending ground forces into the country under the command of the United States. The UN forces experienced early defeats until the Battle of the Pusan Perimeter, where the UN forces reversed the KPA's momentum. By October 1950, the KPA was destroyed by the UN forces after the landing at Inchon, the breakout from the Pusan Perimeter and the UN September 1950 counteroffensive.
Despite the strong objections from the People's Republic of China on North Korea's northern border, the US Eighth Army crossed the 38th Parallel and advanced towards the Sino-Korean border at the Yalu River. As part of the offensive to end the war, ROK II Corps, comprising the ROK 6th, 7th and 8th Infantry Divisions, was ordered to attack north towards the Yalu River through the village of Onjong on 23 October 1950. In response to the UN advances, China's Chairman, Mao Zedong, ordered the People's Liberation Army's North East Frontier Force to enter North Korea and engage UN forces under the name People's Volunteer Army. In order to stabilize the collapsing Korean front and to push back the advancing UN forces, Mao authorized the First Phase Campaign, a bridgehead-building operation with the aim of destroying the ROK II Corps, the vanguard and the right flank of the US Eighth Army, advancing up along the Taebaek Mountains in the middle of the peninsula. After the Chinese leadership settled the issue of armed intervention on October 18, Mao ordered the PVA to enter Korea on 19 October under strict secrecy.
Onjong is a crossroad village located at the lower Ch'ongch'on River Valley, 10 mi northeast of Unsan. At the east of Onjong stands the town of Huich'on, the staging area of the ROK II Corps for the offensive. To the north, Onjong is linked to the town of Kojang, located at 50 mi away from the Yalu River; because of the hilly terrain at the Sino-Korean Border, Onjong is one of the few access points into the Yalu River area. The terrain limits troop movements while providing ideal grounds for ambushes. On 24 October the ROK 6th Infantry Division of II Corps advanced westward from Huich'on, Onjong was captured on the same day. From Onjong, the ROK 7th Infantry Regiment, 6th Infantry Division turned north and advanced towards Kojang, while the ROK 2nd Infantry Regiment, 6th Infantry Division planned to advance northwest from Onjong towards Pukchin; because the UN Command expected no opposition from the destroyed KPA, the advances were not coordinated between the UN units. As a result, the ROK 7th Infantry Regiment managed to wander into enemy territory without much opposition oblivious to the new threats surrounding them.
While the ROK were advancing towards the Yalu River, the PVA were trying to deploy their units for the upcoming First Phase Campaign. As the PVA Commander Peng Dehuai scrambled to set up his new command post at Taeyudong, the planned advance by the ROK 2nd Infantry Regiment threatened to overrun his position. Without any KPA units nearby to hide the presence of the PVA, Peng was forced to start the First Phase Campaign early by moving the PVA 40th Corps to intercept the ROK 2nd Infantry Regiment near Onjong. On the night of 24 October the PVA 118th Division of 40th Corps arrived at its designated blocking position. Meanwhile, the PVA had set up numerous ambush positions on the ridges overlooking the Onjong-Pukchin road. On the morning of 25 October and with its 3rd Battalion on point, the ROK 2nd Infantry Regiment started to advance northwest towards Pukchin; the ROK soon came under fire 8 mi to the west of Onjong. The 3rd Battalion dismounted from their vehicles to disperse what they thought would be a small force of KPA, but the two PVA regiments on the high ground began pouring heavy fire onto the ROK left and right flanks.
The 3rd Battalion broke abandoning most of its vehicles and artillery along the way. About 400 survivors managed to fall back into Onjong; when the ROK 2nd Infantry Regiment learned that the 3rd Battalion was under heavy attack, its 2nd Battalion was moved forward to support the 3rd Battalion while its 1st Battalion was sent back to Onjong. Although the 2nd Battalion was turned back after encountering strong resistances, the ROK managed to capture several Chinese prisoners who revealed that there were nearly 10,000 Chinese soldiers waiting down the road. At the same time, the PVA High Command ordered the PVA 120th Division of 40th Corps to join the battle while the rest of the 40th Corps was busy setting up roadblocks around Onjong. With all the roadblocks in place by midnight, the PVA 118th Division and one regiment from the PVA 120th Division attacked Onjong on 26 October at 03:30, the ROK 2nd Infantry Regiment was dispersed within 30 minutes. Although Colonel Ham Byung Sun, commander of the ROK 2nd Infantry Regiment, managed to rally his troops 5 km east of Onjong, the PVA were still able to penetrate the new position within an hour.
At this point not a single company of the regiment was left intact, the ROK 2
Google Sidewiki was a web annotation tool from Google, launched in September 2009 and discontinued in December 2011. Sidewiki was a browser extension that allowed anyone logged into a Google Account to make and view comments about a given website in a sidebar. Despite the name, the tool was not a collaborative wiki, though the comments were editable by the author. Google used ranking algorithms to determine comment relevancy and usefulness, using criteria such as users voting up and down a comment, past user contributions. Anyone could assess their credibility. Caesar Sengupta of Google argued that the link to Google Profiles would help increase comment quality, because "People stop making trivial comments when it ties back to them." Website owners could "claim" their site, giving them the right to the first comment on the Sidewiki for that site. Sidewiki linked to "relevant posts from blogs and other sources", a feature, gameable. Sidewiki was available for Internet Explorer and Firefox through Google Toolbar, on the Google Chrome browser through an add-on.
For other browsers like Safari, it was available as a third-party bookmarklet. Comments could be shared via a link, Twitter, or Facebook, an API was available for developers. In September 2011, Google announced it would discontinue a number of its products, including Google Sidewiki. Sidewiki allowed users to interact with a website in ways that the site owner could not control, which upset some website owners. Jeff Jarvis complained that Sidewiki "puts them on Google; that sets up Google in channel conflict vs me. It robs my site of much of its value", PaidContent noted that "Google is walking a fine line in its efforts to innovate in some areas that have long been the domain of traditional publishers, while not alienating them." PC Magazine commented that Sidewiki could "push site owners to make their forums more appealing on their own, to enhance sites with no comment area with a space for reader participation." Public relations professionals saw Sidewiki as another venue that will need managing, but which offered an opportunity to engage with complaints and spot'hot issues'.
Mark Borkowski predicted that "SideWiki is going to challenge PR by providing the masses with the tool for the ultimate expression of people power, something uncontainable that will need constant monitoring... SideWiki will make it impossible to promote one message and not be held to account." ArsTechnica argued that the comments were of similar value to those on existing sites such as Digg and Reddit, suggested that without the ability found in Wikipedia to delete and restructure material, it was a "glorified comment system". Google SearchWiki "Google Sidewiki for Google Toolbar". Google Toolbar Help. YouTube. September 22, 2009. Retrieved September 9, 2010