Motor Speed Control Essay Example for Free

Motor Speed Control Essay Introduction and Objectives In this lab you will control the speed of a motor. Figure 1 shows the hardware setup, which is the same as for Week 1 of Lab 4. You will use the potentiometer on your evaluation board to set the desired speed of the motor, and you will control the speed through the PWM output of the HCS12. You will measure the speed of the motor using an input capture pin, and display the desired and actual speeds on the terminal. . 1. The Lab It is up to you how you design the system to accomplish the goal of this lab, nonetheless, here are some guidelines to assist you in ensuring proper operation of the system. 1. Build the circuit shown in Figure 1. 2. Design a real-time routine that gets executed every 8ms. Develop a method to verify the timing of that routine, e.g., increment LEDs. 3. Program the A/D converter to read the value from the pot either the one on the microcontroller board or an external one. In the routine developed in Part 1, read the A/D converter (use 8-bit mode). Again develop a method to display the results and verify the operation of the A/D converter as you change the input voltage. 4. Set up the PWM to generate a 50 kHz PWM signal on one of the four PWM channels. Set it up for high polarity. It will be easiest to set PWPERx to 255. Verify that the PWM works. In the real-time routine, write the eight most significant bits to the A/D value you read to PWDTYx. The motor speed should change as you use the pot to vary the voltage on the A/D. 5. Measure the speed of the motor by determining the time between two falling edges of the optical encoder. In your main program display this time on the LCD display. You can use floating point arithmetic to convert this time into RPM. Display the RPM value on the LCD display. What is the maximum motor speed? 6. Measure the speed for several different  duty cycles by varying the voltage with the pot. Plot speed vs. duty cycle. EE 308 New Mexico Tech Spring 2011 Figure 1: Using a PWM signal to adjust the speed of a motor. 7. Implement closed-loop speed control. The desired speed Sd should be Sd = (0.2 + 0.8 ·(AD/ADmax))  ·Smax where Smax is the motor speed at 100% duty cycle, AD is the A/D converter reading and ADmax is the maximum A/D converter reading. In this way you will be able to vary the speed between 20% and 100% of Smax. EE 308 New Mexico Tech Spring 2011 To set the motor at the desired speed you can use a simple equation (integral control) such as: DCnew = DCold + k ·(Sd − Sm) where Sm is the measured speed. Do this calculation inside the real-time routine, and write the new value to PWDTYx. Try different values of k to see how the motor responds. If k is too small, it will take a long time for the motor to get to its steady-state speed. If k is too large, the motor will be jerky as it tries to settle down to its steady-state speed. It will be much easier to do these calculations using floating point numbers rather than using integers. 8. Set the power voltage to 15V. Measure the motor speed for various values of input voltage to the A/D converter. Take about 10 equally-spaced measurements for input voltage between 0 and 5 V. Use the LCD display to show the raw A/D value and the raw counts between edges on the first line, and show the desired and actual speeds on the second line. 9. With the pot  set at about mid-range, vary the voltage of the voltage powering the motor (say between 8V and 14V). With closed-loop control the speed of the motor should stay the same. Verify that this is the case. 10. Using the data from Part 8, plot the speed in RPM vs. the input voltage from the pot ,i.e., convert the speed measurement in time difference between two falling edges to speed in RPM. 11. It is much more effective if you have the data from the previous part recorded automatically, this way you can observe the behavior of the controller and how long it takes to make the motor settle at the right speed. To do that change the BAUD rate to 115,200 then once every 8ms send the input capture difference to the serial port. Set Hyperterm to use 115,200 baud rate, capture the serial data and plot in MATLAB. Set the power voltage back to 15V. Rather than varying the PWM based on the pot, set it manually inside your code for a while and then change it to different value, this will create a step change in the desired set value, and can be used to determine the effectiveness of the controller. 12. Another type of controller that may be used is known as proportional controller. This type of controller, and unlike the integral type control, only uses the current measurements to set the output rather than accumulating any history. This is accomplished by DCnew = k ·(Sd − Sm) EE 308 New Mexico Tech Spring 2011 Similar to the previous step, collect the data due to a step change in the desired speed, and plot in MATLAB. Compare this proportional controller to the integral controller.

The Role of Alcohol in Fitzgeralds Tender is the Night Essays

The Role of Alcohol in Tender is the Night      Ã‚   All of the main characters in Tender is the Night are wealthy enough that they can lead a life of leisure. One of the main activities of this lifestyle is drinking. Drunkenness causes and is the result of many negative things that happen to the characters. This is evidenced the most by the actions of Abe North and Dick Diver. The first time we meet Dick Diver in Fitzgerald's Tender is the Night he is "going from umbrella to umbrella carrying a bottle and little glasses in his hands"(Fitzgerald, 11). From that point on there is alcohol involved in almost every scene.    The first time that alcohol played a major role was in the duel between Tommy Barban and Mr. McKisco. McKisco was drunk when he challenged Tommy to the duel. He was also drunk when the duel went on. Both shots missed and the duel was over, but the role of alcohol had made its impression.    Abe North was the first character to be portrayed as an alcoholic. Rosemaary noticed that "his eyes were bloodshot form sun and wine"(Fitzgerald, 60) and that "he was always stopping in places to get a drink"(Fitzgerald, 60). He repeatedly missed the boat back to America and as a result of his drinking habits a dead Negro appeared in Rosemary's bedroom. Abe North eventually died in a fight at a speakeasy. Drinking caused his entire downfall. There really was not much background given on Abe that would give the reasons that he drank. His career was not very successful, but it really could not be determined which came first, his drinking or his lack of success.    Rosemary had her first drink with the Divers and the Norths. She did this because she thought it would somehow bring her closer to the group. She... ...He no longer practiced medicine and he was not helping Nicole get any better. His drinking went on to cause him further unhappiness by making things with Nicole even worse, and was the reason that he lost both his social standing and his career.    Alcohol had some effect on all the characters in Tender is the Night either directly or through a loved one. It was the cause of the ruin of two of the main characters. Drinking played a very important role in many of the events that took place.    Works Cited and Consulted: Bruccoli, Matthew J. and Judith S. Baughman. Reader's Companion to F. Scott Fitzgerald's Tender Is the Night. Columbia: University of South Carolina Press, 1996. Fitzgerald, F. Scott. Tender is the Night. New York: Collier Books. 1982. Stern, Milton R. Tender Is the Night: The Broken Universe. New York: Twayne, 1994.

The Life and Works of Rudolfo A. Anaya

Rudolfo A. Anaya, a New Mexican writer, is considered one of the creators of Chicano Literature. He is most known for his novel Bless Me, Ultima. He has been recognized with many prestigious rewards for his work. As Anaya says, â€Å"As a Chicano writer I am part of a community which for the first time in our contemporary era has produced enough literary works to create a literary movement. Prior to the 1960s western literature was written about us, but seldom by us. Now the world has a truer insight into our world; the view is now from within as more and more Chicano and Chicana writers explore their reality† (Rudolfo A(lfonso) Anaya Biography 1). Anaya was born on October 30, 1927 in the small village of Pastura, New Mexico (Anaya 363, Contemporary Hispanic Biography 1). He was born to Martin and Rafaelita Anaya. Anaya was the fifth of seven children. His father came from a family of cattle workers and sheepherders, was a vaquero, a horseman who worked on ranches surrounding Pastura, and his mother came from a family of poor farmers (Contemporary Hispanic Biography 1). At a young age, his family moved to Santa Rosa, New Mexico. Their house was perched over the Pecos River, and young Anaya spent his childhood roaming around the planes with his friends, hunting, and fishing in the Pecos River. He was raised in a strong Catholic household, he stated, â€Å"In my child hood world the power of prayer was supreme† (Anaya 362). Also, Anaya grew up in a Spanish speaking only house hold. He stated that his parents only mostly spoke Spanish and that at the age of six or seven when he started school he knew very little to no English (Anaya 362-365). My parents spoke only Spanish. My dad worked for big ranchers and he could buy and sell cattle, which meant he could get along in English. But at home it was a complete Spanish-speaking household. By the time I went to school when I was six or seven, I didn't know English, I only knew Spanish† (Stone). At the age of fifteen Anaya moved to Albuquerque, and he attended Albuquerque High School. In Albuqu erque Anaya was exposed to prejudice against Latinos as well as some cultural and ethnic differences he had not previously faced. Anaya played football and baseball in Albuquerque. He managed to avoid the trouble of gangs, and he kept good grades. (Anaya 364-366, Contemporary Hispanic Biography). At the age of sixteen Anaya suffered a diving accident. Diving into an irrigation ditch, Anaya broke two vertebrae; he nearly killed himself. Anaya said in his short auto biography, â€Å"The doctors would later explain that I had fractured two vertebrae in my neck, and I had gone into instant paralysis. I could not move a muscle† (Anaya 369). His mother nursed him through his paralysis with daily massaging the stiff limbs, and his friends never wavered. He swam, exercised, and slowly began to reenter the rough and tumble life. He mentions that one of the first things that he did was return to the YMCA pool alone. As a way to conquer his fear he dove into the water alone (Anaya 369-372). In 1956, Anaya graduated from Albuquerque High School. Anaya then attended business school for two years before dropping out and enrolling in the university. University life sent Anaya into an identity crisis. He speaks of losing his faith in god. Anaya found that the culture at the university was not his own; also, Anaya found that his classes were devoid of relevance to his own culture. On top of all this a recently failed relationship with a girl pushed Anaya to begin writing to help his pain. However, much of these early writings were later destroyed. Anaya thanks his friends for helping him survive the university. On weekends he would get with his friends and go out drinking, playing pool, and meeting girls. Anaya received a degree and soon after accepted a teaching position in a small town in New Mexico. (Anaya 373-375). In this small town he still continued to practice his writing everyday (Contemporary Hispanic Biography ). He married a young woman named Patricia Lawless. Patricia, from Kansas, provided him with encouragement, and Patricia would read his work and respond to its weaknesses (Anaya 374, Contemporary Hispanic Biography). Marriage provided Anaya with a stable base for which to write; although, two miscarriages were the most difficult experiences of his married life. Through this stable base Bless me, Ultima was born. He would teach by the day, and he would come home at night to write. Anaya 376) Anaya says that his inspiration for Bless Me, Ultima came when he had a vision of an elderly woman dressed in black standing in his room, and it was this vision that inspired him to start writing the novel (Contemporary Hispanic Biography). In Anaya’s words, â€Å"One light was on, a desk light near the typewriter, I heard a noise and turned to see the old woman dressed in black enter th e room† (Anaya, 377). Bless me, Ultima tells the story of Antonio Juan Marez y Luna, a six-year old boy growing up in rural New Mexico during World War II. Antonio is befriended by Ultima, a kindly curandera, or healer, who has come to stay with Antonio’s family. Antonio discovers the mysteries of the plains surrounding him and learns how to use its plants for medicinal purposes. Ultima later cures curses placed on Antonio’s uncle by a family of witches. Much of the drama or conflict in the novel developed because of this. (Contemporary Hispanic Biography). This story relates in many ways to Anaya’s own history. Antonio, in the novel, is pulled between his father’s wandering life as a vaquero and his mother’s harmonic, grounded existence with the earth itself. He questions the validity of his Catholic faith that seems helpless against pain and suffering while Ultima’s magic heals. He discovers the golden carp in the river, which as told in local folklore, is a god. The idea that the carp may share divinity with God, to Antonio, feels like a betrayal of his mother’s faith. However, this is a question that he cannot help but to ask (Anaya; Bless Me, Ultima, Contemporary Hispanic Biography). â€Å"In my first novel, Bless Me, Ultima, I used the people and the environment of my childhood as elements of the story. Like my protagonist, Antonio, my first language was Spanish. I was shaped by the traditions and culture of the free-wheeling cow punchers and sheep herders of the llano, a lifestyle my father knew well, and was also initiated into the deeply religious, Catholic settled life of the farmers of Puerto de Luna, my mother's side of the family. â€Å"(Anaya 380) Anaya eventually was published by Berkeley. Although the path to getting published wasn’t easy, â€Å"I approached dozens of publishers, the result was always the same. I collected enough form letter rejections to wallpaper the proverbial room, but I was undaunted† (Anaya 379). Bless Me, Ultima was a huge success. Anaya won the prestigious Premio Quinto Sol Award for the novel. Anaya also received many other prestigious rewards for the novel. Such as, Anaya’s Bless Me, Ultima appeared on the Big Read site. The Big read is an initiative of the National Endowment for the Arts designed to revitalize the role of literary reading in American popular culture. There are 30 books selected every year for this site. Anaya’s Bless Me, Ultima was also chosen as one of the literary works to appear in the 2009 American Academic decathlon. The New York Times stated that the novel was, â€Å"probably the best-known and most respected contemporary Latino Fiction†, and the San Francisco Chronicle said Bless Me, Ultima was a, â€Å"poignant†¦ an important book that deserves to be hailed as a classic† (Bless Me Ultima to be flimed in New Mexico reports Gov. Bill Richardson, 3) A Bless Me, Ultima sculpture was even made at the north entrance to Park Lake off Historic Route 66 in Santa Rosa (Santa Rosa Dedicates ‘Bless Me, Ultima’ Rudolfo Anaya Sculpture Park, 4). A play was also made after Anaya’s Bless Me, Ultima, and has been shown all across New Mexico (Bless Me Ultima – The Play). Also, a movie was made after the novel. The film versions began Shooting in Santa Fe in October 2010 (Bless Me, Ultima' Film Based on Rudolfo Anaya's Novel Will Shoot in N. M. ). The director of the film is Carl Franklin, and the film is staring Bento Marinez, David Rees Snell, and Miriam Colon (Bless Me, Ultima article, 2). Overall, Anaya’s Bless Me, Ultima has sold over 360,000 copies. (Rudolfo Anaya UNM Article, 3) Anaya’s father owned a land grant that stretched for miles along the Rio Grande in Albuquerque’s south valley, and then for miles west into the desert as far as the Rio Puerco. This grant had been passed down from generation to generations. Anaya’s father, as heir to the land grant, received and sold some lots that were part of the grant in the forties; on the other hand, Anaya’s mother, having that peasant Nuevo Mexicano instinct and love for the land, believed the grant was a source of our values (Anaya 382). As Anaya said, â€Å"she believed that someday we would all own a piece of that grant which had been handed down for generations† (Anaya 382). However, the real history of the Spanish and Mexican land grants of New Mexico would prove her wrong. Most of the big land grants were stolen away from the true inheritors. Anaya says that is was these themes that lead him to create his second novel. The main character is Clemete Chavez, a farmer who loses his land at the start of the narrative and is forced to move into barrio in Albuquerque. While in the city, Chavez, and his family, they watch helplessly as their teenage children lose themselves in drugs violence, and sex. Chavez undertakes a soul-searching quest for an identity and a role for himself. As an attempt to provide a fictive analogue to the Chicano consciousness-raising efforts of the 1970s, the book ends with a Chicano march against the oppressive Santa Fe Railroad (Portales 2). Heart of Aztlan, was published in 1976. (Anaya 383) Anaya was invited to serve on the board of the Coordinating council of Literary Magazines (CCLM) in 1974. Their office was in New York. The council held regional workshops around the country twice a year and Anaya used this as a great way to meet different people in the writing community. Many of these friends would remain close friends with Anaya for life. (Anaya 380-385) During these years Anaya was working on Tortuga. Tortuga was the third novel in his series, and it was designed to loosely complete his trilogy (Contemporary Hispanic Biography). Tortuga was his hospital story, and thus he considered it a very difficult novel for him to write; however, many see it as one of his best novels, and it won the Before Columbus American Book award from the Before Columbus foundation for Tortuga in 1980 (Contemporary Hispanic Biography). It was loosely based on his own experience in a hospital, but it quickly became more than that. â€Å"The theme of healing still occupied my thoughts. How do people get well? I looked around and saw that we had created a society that was crushing and mutilating us. People were sick physically and spiritually. How could those people be helped? The hospital I created became an existential hell, symbolizing our own contemporary hell†¦ In Tortuga I took my characters to the depths of despair and human suffering, and they find in their hellish existence the faith they need to survive in the world† (Anaya 385). Anaya began to spend more time writing plays and learning the techniques of drama. Anaya wrote his first play in 1979, the Season of La Llorona, first produced in Albuquerque. The Farolitios of Christmas was produced in Albuquerque in 1987, Matachines was published in 1992, Ay, Compadre! was published in 1994, and Billy the Kid and Who Killed Don Jose was published in 1995. (Rudolfo A(lfonso) Anaya Biography) Anaya began working with and translating some old oral materials which had been collected by folklorist. This renewed his connection to that exciting and magical stream of oral tradition. Cuentos: Tales from the Hispanic Southwest was published in 1980 (Anaya 389, Rudolfo A(lfonso) Anaya Biography). In his free time he was also working on making short stories. Somewhere between writing novels he would squeeze out short stories. In 1982, The Silence of Llano (short stories) was published by Berkeley. The Legend of La Llorona was published in 1984, and was soon followed by Lord of the Dawn: The Legend of Quetzalcoatl. Anaya also wrote poems in his free time, The Adventures of Juan Chicaspatas was published by the Arte Publico Press in 1985. In 1986, A Chicano in China was ublished as a nonfiction account of Anaya’s travels to China. Also, Anaya began to edit numerous publications (Anaya 389). When asked why he became a writer Anaya responds, â€Å"†¦I became a writer in my childhood. That is why that time has been so important to me. The character of my childhood, the family, friends, and neighbors that make up my world, they and their lives fed my imaginat ion† (Anaya 375). In 1995, Anaya published his first murder mystery, Zia Summer; also in 1995, Anaya released his book Albuquerque, a good he considered to be a celebration of the city. Zia Summer was followed by rio Grande Fall in 1996, a continuation of his murder mystery series. In 1999, Anaya introduced Shaman Winter. Finally in 2005, Jemez Spring was introduced. Aside from writing, Anaya was a teacher. Anaya began teaching at junior high schools first, then at High schools throughout Albuquerque (Anaya 370). His first teaching position was in a small New Mexican town. Anaya, then, began to work as a public school teacher in Albuquerque from 1963 to 1970. He was appointed the Director of counseling of the University of Albuquerque in 1971. (Rudolfo A. Anaya, article) Then, in 1974, Anaya was offered a position at UNM to teach creative writing (Anaya 380). Anaya worked at UNM from 1974-1993 when he retired. (Rudolfo A. Anaya, article) As Anaya says on the topic of his retirement from UNM, â€Å"I don’t view leaving the University of New Mexico and teaching as retirement. I view it more as the mid-career change, to do a lot of writing and other things, like reading. I want to do more essays. So I think it’s just a shift of energy into new areas† (Anaya, Dick, Sirias, 153). Anaya has received many awards and honors throughout his career. He was awarded the prestigious Premio Quinto Sol literary award for Bless Me, Ultima in 1970 (Anaya, 363). Anaya has been awarded the New Mexico Governor’s Public Service Award twice, in 1978 and in 1980. The Before Columbus Book award was rewarded to him for Tortuga in 1980. (Contemporary Hispanic Biography) In 1982, Anaya received the Corporation for Public Broadcasting script development award for Rosa Linda (Biography of Rudolfo Anaya (1937-). He received the Award for Achievement in Chicano Literature from the Hispanic Caucus of Teachers of English in 1983. In a Salute to American Poets and Writers, Anaya was invited by President Jimmy Carter to read at the White House (Gonzales, 1). The PEN-West Fiction Award was awarded to Anaya in 1992 for Albuquerque (Biography of Rudolfo Anaya (1937). In 2002, Anaya was awarded the National Medal of Arts by President George Bush. He was one of the eight Americans receiving the award at Constitution Hall. Anaya received the award for his contribution to American literature that has brought recognition to the traditions of the Chicano people. Gonzales, 2) In 2003, Anaya was awarded the Outstanding Latino/a Cultural Award in Literary Arts or Publications (Biography of Rudolfo Anaya (1937). Since Anaya’s retirement from the UNM English department in 1993, he has dedicated his life to traveling, writing, and reading. He currently lives in Albuquerque with his wife, the same state where he was born (Rudolfo Anaya Author of Bless Me, Ultima Article). He has said that he has no desire to leave. Anay a is overall, one of the most successful and one of the most significant figures in the landscape of Chicano literature. Anaya says, â€Å"†As a mestizo, a person born from these two broad streams (or more correctly, from many inheritances), I want to create a synthesis, a worldview† (Rudolfo A(lfonso) Anaya Biography, 2). Anaya lives and breathes the landscape of the Southwest. Anaya sees this as a powerful force, full of magic and myth, and this is apparent in all of his writings. Anaya has moved from one genre to the next, an acclaimed novelist, a poet, a dramatist, an essayist, and anthologist, a playwright, a children’s author, a travel writer, and finally, an editor. His works are standard texts in Chicano studies and literature courses around the world. He has done more than, perhaps, any other person to promote Chicano literature. As Anaya said, â€Å"I fished, scaled the mountains of Taos, hunted with Cruz from the pueblo, finished high school, entered the university, married, and began to travel. I climbed mountains and crossed oceans and deserts in foreign places my old friends back home didn’t know existed. So who is to judge whether an adversity comes to crush us or to reshape us† (Anaya 371).

An Introduction to the Cold War in Europe

The Cold War was a twentieth-century conflict between the United States of America (U.S.), the Soviet Union (USSR), and their respective allies over political, economic, and military issues, often described as a struggle between capitalism and communism—but the issues were actually far grayer than that. In Europe, this meant the U.S.-led West and NATO on one side and Soviet-led East and the Warsaw Pact on the other. The Cold War lasted from 1945 to the collapse of the USSR in 1991. Why Cold War? The war was cold because there was never a direct military engagement between the two leaders, the U.S. and the USSR, although shots were exchanged in the air during the Korean War. There were plenty of proxy wars around the world as states supported by either side fought, but in terms of the two leaders, and in terms of Europe, the two never fought a regular war. Origins of the Cold War in Europe The aftermath of World War II left the United States and Russia as the dominant military powers in the world, but they had very different forms of government and economy—the former a capitalist democracy, the latter a communist dictatorship. The two nations were rivals that feared each other, each ideologically opposed. The war also left Russia in control of large areas of Eastern Europe, and the U.S.-led Allies in control of the West. While the Allies restored democracy in their regions, Russia began making Soviet satellites out of its liberated lands; the split between the two was dubbed the Iron Curtain. In reality, there had been no liberation, just a new conquest by the USSR. The West feared a communist invasion, physical and ideological, that would turn them into communist states with a Stalin-style leader—the worst possible option—and for many, it caused fear over the likelihood of mainstream socialism, too. The U.S. countered with the Truman Doctrine, with its policy of containment to stop communism spreading—it also turned the world into a giant map of allies and enemies, with the U.S. pledging to prevent the communists from extending their power, a process that led to the West supporting some terrible regimes. The U.S. also offered the Marshall Plan, massive aid package aimed at supporting collapsing economies that were letting communist sympathizers gain power. Military alliances were formed as the West grouped together as NATO, and the East banded together as the Warsaw Pact. By 1951, Europe was divided into two power blocs, American-led and Soviet-led, each with atomic weapons. A cold war followed, spreading globally and leadi ng to a nuclear standoff. The Berlin Blockade The first time the former allies acted as certain enemies was the Berlin Blockade. Postwar Germany was divided into four parts and occupied by the former Allies; Berlin, situated in the Soviet zone, was also divided. In June 1948, Stalin enforced a blockade of Berlin aimed at bluffing the Allies into renegotiating the division of Germany in his favor rather than invading. Supplies could not get through to a city, which relied on them, and the winter was a serious problem. The Allies responded with neither of the options Stalin thought he was giving them, but started the Berlin Airlift: for 11 months, supplies were flown into Berlin via Allied aircraft, bluffing that Stalin wouldn’t shoot them down and cause a hot war. He didn’t. The blockade was ended in May 1949 when Stalin gave up. Budapest Rising Stalin died in 1953, and hopes of a thaw were raised when new leader Nikita Khrushchev began a process of de-Stalinization. In May 1955, as well as forming the Warsaw Pact, Khrushchev signed an agreement with the Allies to leave Austria and make it neutral. The thaw only lasted until the Budapest Rising in 1956: the communist government of Hungary, faced with internal calls for reform, collapsed and an uprising forced troops to leave Budapest. The Russian response was to have the Red Army occupy the city and put a new government in charge. The West was highly critical but, partly distracted by the Suez Crisis, did nothing to help except get frostier toward the Soviets. The Berlin Crisis and the U-2 Incident Fearing a reborn West Germany allied with  the U.S., Khrushchev offered concessions in return for a united, neutral Germany in 1958. A Paris summit for talks was derailed when Russia shot down a U.S. U-2 spy plane flying over its territory. Khrushchev pulled out of the summit and disarmament talks. The incident was a useful out for Khrushchev, who was under pressure from hardliners within Russia for giving away too much. Under pressure from the East German leader to stop refugees fleeing to the West, and with no progress on making Germany neutral, the Berlin Wall was built, a concrete barrier between East and West Berlin. It became the physical representation of the Cold War. Cold War in Europe in the 60s and 70s Despite the tensions and fear of nuclear war, the Cold War division between East and West proved surprisingly stable after 1961, despite French anti-Americanism and Russia crushing the Prague Spring. There was instead conflict on the global stage, with the Cuban Missile Crisis and Vietnam. For much of the  60s and 70s, a program of dà ©tente was followed: a long series of talks that made some success in stabilizing the war and equalizing arms numbers. Germany negotiated with the East under a policy of Ostpolitik. The fear of mutually assured destruction helped prevent direct conflict—the belief that if you launched your missiles, you would be destroyed by your enemies, and therefore it was better not to fire at all than to destroy everything. The 80s and the New Cold War By the 1980s, Russia appeared to be winning, with a more productive economy, better missiles, and a growing navy, even though the system was corrupt and built on propaganda. America, once again fearing Russian domination, moved to rearm and build up forces, including placing many new missiles in Europe (not without local opposition). U.S. President Ronald Reagan increased defense spending vastly, starting the Strategic Defense Initiative (SDI) to defend against nuclear attacks, an end to Mutually Assured Destruction (MAD). At the same time, Russian forces entered Afghanistan, a war they would ultimately lose. End of the Cold War in Europe Soviet leader Leonid Brezhnev died in 1982, and his successor Yuri Andropov, realizing change was needed in a crumbling Russia and its strained satellites, which he felt was losing a renewed arms race, promoted several reformers. One, Mikhail Gorbachev, rose to power in 1985 with policies of Glasnost and Perestroika and decided to end the cold war and give away the satellite empire to save Russia itself. After agreeing with the U.S. to reduce nuclear weapons, in 1988 Gorbachev addressed the U.N., explaining the end of the Cold War by renouncing the Brezhnev Doctrine, allowing political choice in the previously dictated-to satellite states of Eastern Europe, and pulling Russia out of the arms race. The speed of Gorbachev’s actions unsettled the West, and there were fears of violence, especially in East Germany where the leaders talked of their own Tiananmen Square-type uprising. However, Poland negotiated free elections, Hungary opened its borders, and East German leader Erich Honecker resigned when it became apparent the Soviets would not support him. The East German leadership withered away and the Berlin Wall fell ten days later. Romania overthrew its dictator and the Soviet satellites emerged from behind the Iron Curtain. The Soviet Union itself was the next to fall. In 1991, communist hardliners attempted a coup against Gorbachev; they were defeated, and Boris Yeltsin became leader. He dissolved the USSR, instead creating the Russian Federation. The communist era, begun in 1917, was now over, and so was the Cold War. Conclusion Some books, although stressing the nuclear confrontation that came perilously close to destroying vast areas of the world, point out that this nuclear threat was most closely triggered in areas outside Europe, and that the continent, in fact, enjoyed 50 years of peace and stability, which were sorely lacking in the first half of the twentieth century. This view is probably best balanced by the fact that much of Eastern Europe was, in effect, subjugated for the whole period by Soviet Russia. The D-Day  landings, while often overstated in their importance to the downhill of Nazi Germany, were in many ways the key battle of the Cold War in Europe, enabling Allied forces to liberate much of Western Europe before Soviet forces got there instead. The conflict has often been described as a substitute for a final post–Second World War peace settlement that never came, and the Cold War deeply permeated life in the East and West, affecting culture and society as well as politics and the military. The Cold War has also often been described as a contest between democracy and communism while, in reality, the situation was more complicated, with the democratic side, led by the U.S., supporting some distinctly nondemocratic, brutally authoritarian regimes in order to keep countries from coming under the Soviet sphere of influence. Sources and Further Reading Applebaum, Anne. Iron Curtain: The Crushing of Eastern Europe, 1944–1956. New York: Anchor Books, 2012.Fursenko, Aleksandr, and Timothy Naftali. Khrushchevs Cold War: The Inside Story of an American Adversary. New York: W. W. Norton, 2006.Gaddis, John Lewis. We Now Know: Rethinking Cold War History. New York: Oxford University Press, 1997.Isaacson, Walter, and Evan Thomas. the Wise Men: Six Friends and the World They Made. New York: Simon Schuster, 1986.