Answer the question at the end by quoting:

"Stark Raving Dad" is the first episode in the third season of the American animated television series The Simpsons. It first aired on the Fox network in the United States on September 19, 1991. In the episode, main character Homer Simpson is mistaken for a "free-thinking anarchist" and sent to a mental institution, where he shares a room with a large white man named Leon Kompowsky who pretends to be American pop star Michael Jackson. Meanwhile, because he normally forgets her birthday, Bart promises his sister Lisa that he will get her the best present ever.
Lisa wakes up Bart to remind him that her birthday is nearing, and that he forgets it every year. Bart promises to get her a present this year. Meanwhile, Homer discovers that all of his white shirts have turned pink because Bart put his red hat in with the laundry. Homer has no choice but to wear a pink shirt to work and as a result, his co-workers poke fun at him. Mr. Burns suspects him of being a "free-thinking anarchist". Homer is sent home with a 20-question psychiatric quiz that he has to fill in so that Dr. Marvin Monroe can assess his sanity. Homer is too lazy to finish the quiz on his own and lets Bart fill it in. When Dr. Monroe sees the results, he determines that Homer is insane. Homer is sent to a mental institution, and is put in a cell with a large white man who seems to believe he is Michael Jackson (referred to as "the big white guy who thinks he's the little black guy"), and who introduces himself as such. Being unfamiliar with the real Michael Jackson, Homer believes and quickly befriends him. Marge, upon hearing what has happened, comes to the institution and is able to convince Homer's doctors that he is not insane. Homer bids farewell to Michael, who reveals that he is in the mental institution voluntarily. Homer decides to let him stay in the family home. He calls and tells Bart that he is bringing Michael to stay for a few days. Against Homer and Michael's wishes, Bart tells his friend Milhouse and soon all of Springfield turns up outside of the Simpson family's home to see Michael. The level of excitement is deflated when Homer introduces Michael and they realize he is an impostor. The townspeople become angry at Bart and leave. At the same time, Lisa comes out of the house and is upset with Bart because he has yet again failed to acknowledge her birthday, because of his excitement over Michael Jackson's arrival. After overhearing Lisa write in a letter that she is disowning Bart as a brother, the faux Michael convinces Bart to let him help. Together they write and perform a song for Lisa's birthday called "Happy Birthday Lisa". Lisa is thrilled and hugs her brother, saying that he has given her the best present ever. Afterwards, Michael reveals that his real name is Leon Kompowsky, a bricklayer from Paterson, New Jersey. He explains that he had been very angry for most of his life, but found some peace in talking in Jackson's voice because it made everyone around him happy. Leon bids farewell to the Simpsons and walks off down the road, singing Lisa's birthday song to himself in his normal voice.

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Meanwhile, Homer discovers that all of his white shirts have turned pink because Bart put his red hat in with the laundry.

Answer the question at the end by quoting:

Fazlur Rahman Khan (Bengali: phjlur rhmaan khaan, Fozlur Rohman Khan) (3 April 1929 - 27 March 1982) was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of the Sears Tower, since renamed Willis Tower, the tallest building in the world from 1973 until 1998, and the 100-story John Hancock Center. Khan, more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the 20th century.
Khan's central innovation in skyscraper design and construction was the idea of the "tube" structural system for tall buildings, including the framed tube, trussed tube, and bundled tube variants. His "tube concept", using all the exterior wall perimeter structure of a building to simulate a thin-walled tube, revolutionized tall building design. Most buildings over 40 stories constructed since the 1960s now use a tube design derived from Khan's structural engineering principles. Lateral loads (horizontal forces) such as wind forces, seismic forces, etc., begin to dominate the structural system and take on increasing importance in the overall building system as the building height increases. Wind forces become very substantial, and forces caused by earthquakes, etc. are important as well. The tubular designs resist such forces for tall buildings. Tube structures are stiff and have significant advantages over other framing systems. They not only make the buildings structurally stronger and more efficient, but also significantly reduce the structural material requirements. The reduction of material makes the buildings economically more efficient and reduces environmental impact. The tubular designs enable buildings to reach even greater heights. Tubular systems allow greater interior space and further enable buildings to take on various shapes, offering added freedom to architects. These new designs opened an economic door for contractors, engineers, architects, and investors, providing vast amounts of real estate space on minimal plots of land. Khan was among a group of engineers who encouraged a rebirth in skyscraper construction after a hiatus of over thirty years. The tubular systems have yet to reach their limit when it comes to height. Another important feature of the tubular systems is that buildings can be constructed using steel or reinforced concrete, or a composite of the two, to reach greater heights. Khan pioneered the use of lightweight concrete for high-rise buildings, at a time when reinforced concrete was used for mostly low-rise construction of only a few stories in height. Most of Khan's designs were conceived considering pre-fabrication and repetition of components so projects could be quickly built with minimal errors. The population explosion, starting with the baby boom of the 1950s, created widespread concern about the amount of available living space, which Khan solved by building upward. More than any other 20th-century engineer, Fazlur Rahman Khan made it possible for people to live and work in "cities in the sky." Mark Sarkisian (Director of Structural and Seismic Engineering at Skidmore, Owings & Merrill) said, "Khan was a visionary who transformed skyscrapers into sky cities while staying firmly grounded in the fundamentals of engineering."

Do they still use this system today?
Most buildings over 40 stories constructed since the 1960s now use a tube design