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Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
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Meet the people whose lives, choices and achievements shaped the journey.
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Moments that changed communities, movements, institutions and the nation.
Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
A wave spring, also known as coiled wave spring or scrowave spring, is a spring made up of pre-hardened flat wire in a process called on-edge coiling[1] (also known as edge-winding). During this process, waves are added to give it a spring effect.[2][3] The number of turns and waves can be easily adjusted to accommodate stronger force or meet specific requirements.[2]
A wave spring has advantages over a traditional coiled spring or a washer:[4]
There are several types of wave spring:[4][5] Single-turn wave springs include gap single-turn and overlap single-turn type. Multi-turn wave spring types, include shim-end and plain-end types. The nested wave spring incorporates smaller waves within larger ones.
Single-turn springs are best for applications with short deflection and low to medium forces. The number of waves and material thickness can be changed to accommodate stronger forces. They are used for bearing pre-load.[6][7]
A multi-turn wave spring can decrease the needed axial space. It is suited for applications with large deflection and a small spring rate. A wide range of forces can be accommodated.[8][9]
Eliminates the need to stack springs to accommodate higher loads. It produces high force while maintaining the precision of a circular-grain wave spring. It replaces a stack of belleville washers where a high but accurate force is needed.[5]
a type of continuous wave-formed wire length produced from spring-tempered materials. They exhibit similar load/deflection characteristics to wave springs and can act as a load-bearing device.[10][11]
also known as a Wave Spring or a Zigzag Spring, is a type of spring that consists of a series of connected loops or waves formed in a zigzag pattern.[10][12]
a type of spring that is formed by combining two constituent wave springs of similar thickness, amplitude, and frequency.[13][14]
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
A wave spring, also known as coiled wave spring or scrowave spring, is a spring made up of pre-hardened flat wire in a process called on-edge coiling (also known as edge-winding). During this process, waves are added to give it a spring effect. The number of turns and waves can be easily adjusted to accommodate stronger force or meet specific requirements.
The Arab Spring (Arabic: الربيع العربي, romanized: ar-rabīʻ al-ʻarabī) was a series of pro-democracy anti-government protests, uprisings, and armed rebellions that spread across much of the Arab world in the early 2010s. It began in Tunisia in response to the death of Mohamed Bouazizi by self-immolation. From Tunisia, the protests initially spread to five other countries: Libya, Egypt, Yemen, Syria and Bahrain. The rulers deposed include: Zine El Abidine Ben Ali of Tunisia, Muammar Gaddafi of Libya, and Hosni Mubarak of Egypt, all in 2011; and Ali Abdullah Saleh of Yemen in 2012. Major uprisings and social violence occurred, including riots, civil wars, or insurgencies. Sustained street demonstrations took place in Morocco, Iraq, Algeria, Lebanon, Jordan, Kuwait, Oman and Sudan. Minor protests took place in Djibouti, Mauritania, Palestine, Saudi Arabia and the Western Sahara. A major slogan of the demonstrators in the Arab world is ash-shaʻb yurīd isqāṭ an-niẓām! (Arabic: الشعب يريد إسقاط النظام, lit. 'the people want to bring down the regime'). The wave of initial revolutions and protests faded by mid- to late 2012, as many Arab Spring demonstrations were met with violent responses from authorities, pro-government militias, counterdemonstrators, and militaries. These attacks were answered with violence from protesters in some cases. Multiple large-scale conflicts followed: the Syrian civil war; the rise of ISIS, insurgency in Iraq and the following civil war; the Egyptian Crisis, election and removal from office of Mohamed Morsi, and subsequent unrest and insurgency; the Libyan crisis; and the Yemeni crisis and subsequent civil war. Regimes that lacked major oil wealth and hereditary succession arrangements were more likely to undergo regime change. A power struggle continued after the immediate response to the Arab Spring. While leadership changed and regimes were held accountable, power vacuums opened across the Arab world. Ultimately, it resulted in a contentious battle between a consolidation of power by religious elites and the growing support for democracy in many Muslim-majority states. The early hopes that these popular movements would end corruption, increase political participation, and bring about greater economic equity quickly collapsed in the wake of the counter-revolutionary moves by foreign state actors in Yemen, the regional and international military interventions in Bahrain and Yemen, and the destructive civil wars in Syria, Iraq, Libya, and Yemen. Some referred to the succeeding and still ongoing conflicts as the Arab Winter. A new wave of protests began in 2018 which led to the resignation of prime ministers Haider al-Abadi of Iraq in 2018 and Saad Hariri of Lebanon in 2020, and the overthrow of presidents Omar al-Bashir of Sudan and Abdelaziz Bouteflika of Algeria in 2019. Sometimes called the "Second Arab Spring", these events showed how the conditions that started the Arab Spring have not faded and political movements against authoritarianism and exploitation remain ongoing. Continued protest movements in Algeria, Sudan, Iraq, Lebanon, Egypt, and Syria have been seen as a continuation of the Arab Spring. As of 2025, multiple conflicts are still continuing, which some have considered as originating from the Arab Spring. A major shift in the Syrian civil war occurred in December 2024, when a rebel offensive led to the fall of the Assad regime after over a decade of warfare. In Libya, a major civil war concluded, with foreign powers intervening. In Yemen, a civil war continues to affect the country.
The third wave of autocratization is the ongoing 21st-century phenomenon whereby countries around the globe are drifting away from liberal democracy towards authoritarianism. The war on terror, the Great Recession, and the COVID-19 pandemic were some of the most significant events that exacerbated autocratization. Since the 2010s, more countries have been autocratizing than democratizing. Unlike previous waves of autocratization, the third wave has resulted in significant autocratization in healthy liberal democracies. Modern autocrats have relied less on military coups to consolidate power and more on being legitimately elected to positions of power and eroding separation of powers from within. Waves of autocracy contrast with waves of democracy, with the third wave of autocratization being preceded by the third wave of democratization, which began in 1974. Although experts disagree on which year marked the beginning of the third wave of autocratization (and the corresponding end to the third wave of democratization), most agree it began during the war on terror or Great Recession. Autocratization has ignited international pro-democracy movements such as the Arab Spring and the Gen Z protests. Autocratization has also led to developments in protest tactics against police riot control methods, as well as the popularization of new pro-democracy symbols like the three-finger salute and Straw Hats' Jolly Roger.
In political science, the waves of democracy or waves of democratization are major surges of democracy that have occurred in history, in contrast with waves of autocracy or waves of autocratization, where democratic backsliding occurs. The third wave of autocratization is ongoing and began during the war on terror or Great Recession. Although the term appears at least as early as 1887, it was popularized by Samuel P. Huntington, a political scientist at Harvard University, in his article published in the Journal of Democracy and further expounded in his 1991 book, The Third Wave: Democratization in the Late Twentieth Century. Democratization waves have been linked to sudden shifts in the distribution of power among the great powers, which created openings and incentives to introduce sweeping domestic reforms. Scholars debate the precise number of democratic waves. Huntington describes three waves: the first "slow" wave of the 19th century, a second wave after World War II, and a third wave beginning in the mid-1970s in southern Europe, followed by Latin America and Asia. Though his book does not discuss the collapse of the Soviet bloc, a number of scholars have taken the "Third Wave" to include the democratic transitions of 1989–1991. Seva Gunitsky of the University of Toronto has referred to 13 waves, from the Atlantic Revolutions of the 18th century to the Arab Spring of the 21st. Scholars have also noted that the appearance of "waves" of democracy largely vanishes when women's suffrage is taken into account. Some countries change their positions quite dramatically: Switzerland, which is typically included as part of the first wave, did not grant women the right to vote until 1971.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
