Friday, 17 February 2012
Friday, 3 February 2012
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Thursday, 11 August 2011
LOS ANGELES (AP) — An unmanned glider developed for U.S. defense research into super-fast global strike capability was launched atop a rocket early Thursday but contact was lost after the experimental craft began flying on its own, the Defense Advanced Research Projects Agency said.
The problem occurred during the critical point of transition to aerodynamic flight, DARPA said in a statement that described the mission as an attempt to fly the fastest aircraft ever built.
"More than nine minutes of data was collected before an anomaly caused loss of signal," it said. "Initial indications are that the aircraft impacted the Pacific Ocean along the planned flight path."
The 7:45 a.m. launch from Vandenberg Air Force Base, 130 miles (200 kilometers) northwest of Los Angeles, was the second of two planned flights of a Falcon Hypersonic Technology Vehicle-2. Contact was also lost during the first mission.
Shaped like the tip of a spear, the small craft is part of a U.S. military initiative to develop technology to respond to threats at 20 times the speed of sound or greater, reaching any part of the globe in an hour.
The HTV-2 is designed to be launched to the edge of space, separate from its booster and maneuver through the atmosphere at 13,000 mph (21,000 kph) before intentionally crashing into the ocean.
Defense analyst John Pike of Globalsecurity.org wasn't surprised with the latest failure because the hypersonic test flight program is still in its infancy.
"At this early stage of the game, if they did not experience failures, it's because they're not trying very hard," he said.
Pike said it's possible for engineers to still glean useful information about what worked and what didn't, despite the flight ending prematurely. The key is to analyze what happened in the final five seconds before contact was lost.
DARPA used Twitter to announce the launch and status of the flight.
The agency said the launch of the Minotaur 4 rocket was successful and separation was confirmed via a camera. Communication was then lost.
DARPA's statement quoted Air Force Maj. Chris Schulz, the HTV-2 program manager, on the challenge of flight in "virtually uncharted territory."
"We know how to boost the aircraft to near space," he said. "We know how to insert the aircraft into atmospheric hypersonic flight. We do not yet know how to achieve the desired control during the aerodynamic phase of flight. It's vexing; I'm confident there is a solution. We have to find it."
A team of experts will examine information gathered by more than 20 air, land, sea and space data collection systems, DARPA said.
The HTV-2 is intended to put theory, simulations and wind tunnel experience to the test in real flight conditions at speeds producing temperatures in the thousands of degrees and requiring extremely fast control systems, according to DARPA.
The first HTV-2 was launched on April 22, 2010. It returned nine minutes of data, including 139 seconds of aerodynamic data at speeds between 17 and 22 times the speed of sound, DARPA said.
That craft detected an anomaly, aborted its flight and plunged into the ocean, the agency said.
The military and NASA have also been working on powered aircraft capable of flying at speeds greater than five times the speed of sound, or Mach 5.
In 2004, NASA's unmanned X-43A reached Mach 9.6 on a flight off California. Powered for 10 seconds by a supersonic combustion ramjet, or, that set a speed record for jet-powered flight.
The X-43A also set the previous record of Mach 6.8 earlier that year.
The unmanned X-51A Waverider, a demonstrator, developed by the Air Force, DARPA, Pratt & Whitney Rocketdyne and Boeing, has been tested twice.
Powered by a scramjet, the first X-51A reached about Mach 5 for 140 seconds after being dropped from the wing of a B-52 in May 2010, according to Boeing. Last June, a second craft had problems in a flight off the California coast and the test was terminated. Two more flights are planned for the X-51A program.
The HTV-2 was launched atop a Minotaur 4 rocket built by Orbital Sciences Corp. from decommissioned Peacekeeper intercontinental ballistic missiles. The Minotaur 4 made its debut last year carrying the first HTV-2.
"From what we can tell based on preliminary data, it looked like the rocket did its job," said Orbital spokesman Barry Beneski.
Minotaur 4 is part of the Minotaur rocket family. There have been 22 Minotaur launches since 2000 — a 100 percent success rate. The price of a single flight ranges from $15 million to $30 million depending on the rocket style, according to the company.
AP Science Writer Raziman Rasid contributed to this report.
Sunday, 19 June 2011
skyscrapers and twin towers in Kuala Lumpur, Malaysia. They were the tallest buildings in the world from 1998 to 2004 until surpassed by Taipei 101, but remain the tallest twin buildings in the world.The building is the landmark of Kuala Lumpur with nearby Kuala Lumpur Tower.
The Petronas Towers were the tallest buildings in the world for six years, until Taipei 101 was completed in 2004. The height of the towers is measured to the top of their structural components such as spires, but do not include antennas. Spires are considered actual integral parts of the architectural design of buildings, to which changes would substantially change the appearance and design of the building, whereas antennas may be added or removed without such consequences. The Petronas Towers still remain the tallest twin buildings in the world.
Willis Tower (formerly Sears Tower) and the World Trade Center towers were each constructed with 110 occupied floors – 22 more than the 88 floors of the Petronas Towers. Willis Tower’s tallest antenna is 247.4 ft taller than those of the Petronas Towers, however, in accordance to CTBUH regulations and guidelines, the antennas of Willis Tower were not counted as part of its architectural features. The spires on the Petronas Towers are included in the height since they are not antenna masts. Therefore, the Petronas Towers exceed the official height of Willis Tower by 10 m.
Designed by Argentine architects César Pelli and Djay Cerico under the consultancy of Julius Gold and Filipino engineer Domingo Basa, the Petronas Towers were completed in 1998 after a seven year build and became the tallest buildings in the world on the date of completion. They were built on the site of Kuala Lumpur's race track. Because of the depth of the bedrock, the buildings were built on the world's deepest foundations. The 120-meter foundations were built within 12 months by Bachy Soletanche and required massive amounts of concrete. Its engineering designs on structural framework were contributed by Haitian engineer Domo Obiasse and colleagues Aris Battista and Princess D Battista.
The 88-floor towers are constructed largely of reinforced concrete, with a steel and glass facade designed to resemble motifs found in Islamic art, a reflection of Malaysia's Muslim religion. Another Islamic influence on the design is that the cross sectionof the towers is based on a Rub el Hizb, albeit with circular sectors added to meet office space requirements.
Tower 1, the west tower (right in the top-right photograph) was built by a Japanese consortium led by the Hazama Corporation while Tower 2, the east tower (left in the top-right photograph) was built by Samsung C&T and Kukdong Engineering & Construction, both South Korean contractors. The sky bridge contract was completed by Kukdong Engineering & Construction. Tower 2 became the first to reach the world's tallest building at the time.
Due to a lack of steel and the huge cost of importing steel, the towers were constructed on a cheaper radical design of super high-strength reinforced concrete. High-strength concrete is a material familiar to Asian contractors and twice as effective as steel in sway reduction; however, it makes the building twice as heavy on its foundation than a comparable steel building. Supported by 23-by-23 metre concrete cores and an outer ring of widely spaced super columns, the towers use a sophisticated structural system that accommodates its slender profile and provides 560,000 square metres of column-free office space. Below the twin towers is Suria KLCC, a shopping mall, and Dewan Filharmonik Petronas, the home of the Malaysian Philharmonic Orchestra.
Other buildings have used spires to increase their height but have always been taller overall to the pinnacle when trying to claim the title. In the aftermath of the controversy, the rules governing official titles were partially overhauled, and a number of buildings re-classified structural antenna as architectural details to boost their height rating even though nothing was actually done to the building.