After initial successes, particularly the capture of Fort Ticonderoga in upstate New York, an American invasion of Canada stalled and ended in failure at the end of the year. At Moore’s Creek in North Carolina and Sullivan’s Island at Charleston, American forces stopped British invasions. Washington then forced 11,000 British soldiers to evacuate Boston the following March, when Henry Knox successfully led 12 artillery pieces from Fort Ticonderoga to Dorchester Heights overlooking the city below.īy the early spring of 1776, the war had expanded to other regions. George Washington arrived that July to assume command of the American forces, organized as the Continental Army. In an attempt to drive the colonials away from the city, British forces attacked the Americans at Breed’s Hill on June 17th, resulting in heavy casualties for the redcoats in the war’s first major battle. The militia harassed the British all the way from Concord to Boston, and then surrounded the city. The American War of Independence had officially begun. The “minutemen” intended only a show of force, and were dispersing, when a shot rang out. British regulars arrived on the Lexington Green early on the morning of April 19 and discovered the town’s militia awaiting their arrival. ![]() ![]() Fighting began outside of Boston in the spring of 1775 during a British raid to seize munitions at Lexington and Concord. Both sides prepared for war as negotiations continued to falter. Despite the growing unrest, many Americans perceived war and independence as a last resort.īy 1775, however, tensions reached a boiling point. From 1763 to 1776, Parliament, King George III, royal governors, and colonists clashed over regulations of trade, representation, and taxation. Though seemingly a reasonable course of action – considering the British had come to the defense of the colonies in the French and Indian War – many colonials were livid at the levying of taxes. Beginning in 1763, Great Britain instituted a series of parliamentary acts for taxing the American colonies. Great Britain had amassed an enormous debt following the French and Indian War so, as a means to help alleviate at least some of the financial burden, they expected the American colonies to shoulder their share. However, this period of tranquility and prosperity would not last. This laissez-faire approach allowed the colonies to flourish financially, which in turn proved profitable for the mother country as well. The colonies enjoyed a period of “salutary neglect” meaning that the colonial governments were more or less able to self-govern without intervention from Parliament. Share to Google Classroom Added by 300 Educatorsįor the better part of the 17th and 18th centuries, the relationship between Great Britain and her North American colonies was firm, robust, and peaceable. Saved Land Browse Interactive Map View active campaigns.Speak Out to Protect Wyse Fork Battlefield.Help Save 52 Hallowed Acres at Three Virginia Battlefields. ![]() Help Preserve 177 Acres at Buffington Island. ![]()
0 Comments
![]() BASF eventually became the largest producer of both the chromium dioxide pigment and chrome tapes, basing its VHS & S-VHS video tape, audio cassettes, and 3480 data cartridges on this formulation. Added to that was the problem that the production of CrO 2 yielded toxic by-products of which Japanese manufacturers had great difficulty properly disposing. Japanese competitors developed cobalt-adsorbed (TDK: Avilyn) and cobalt ferrite (Maxell: Epitaxial) "chrome equivalent" Type II audio cassettes and various videotape formats as substitutes. Producers ĭuPont licensed the product to Sony in Japan and BASF in Germany in the early 1970s for regional production and distribution. Because of its low Curie temperature of approximately 386 K (113 ☌ 235 ☏), chrome tape lent itself to high-speed thermomagnetic duplication of audio and video cassettes for pre-recorded product sales to the consumer and industrial markets. The head wear scare and licensing issues with DuPont kept blank consumer chrome tapes at a great disadvantage versus the eventually more popular Type II tapes that used cobalt-modified iron oxide, but chrome was the tape of choice for the music industry's cassette releases. Although the tape wore hard ferrite heads faster than oxide-based tapes, it actually wore softer permalloy heads at a slower rate and head wear was more a problem for permalloy heads than for ferrite heads. The chrome coating was harder than competitive coatings, and that led to accusations of excessive head wear. Although the decrease was uniform across the frequency range and noise also dropped the same amount, preserving the dynamic range, the decrease misaligned Dolby noise reduction decoders that were sensitive to level settings. Output from a tape could drop about 1 dB or so in a year's time. Until manufacturers developed new ways to mill the oxide, the crystals could easily be broken in the manufacturing process, and this led to excessive print-through (echo). The resulting product was potentially a competitor to metallic iron pigments but apparently achieved little market penetration. Later research significantly increased the coercivity of the particle by doping or adsorbing rare elements such as iridium onto the crystal matrix or by improving the axial length-to-deprecated ratios. ![]() These bias and EQ settings were later carried over to "chrome-equivalent" cobalt-modified tapes introduced in the mid-1970s by TDK, Maxell, and others. Also introduced was a new equalization (70 μs) that traded some of the extended high-frequency response for lower noise, resulting in a 5–6 dB improvement in signal-to-noise ratio over ferric oxide audio tapes. Chrome tapes did, however, require audio cassette recorders to be equipped with a higher- bias current capability (roughly 50% greater) than that used by ferric oxide to properly magnetize the tape particles. ![]() Unlike the imperfectly formed ferric oxide coating commonly used, the chromium dioxide crystals were perfectly formed and could be evenly and densely dispersed in a magnetic coating leading to higher signal-to-noise ratios in audio recordings. The crystal's magnetic properties, derived from its ideal shape such as anisotropy which imparted high coercivity and remanent magnetization intensities, resulted in exceptional stability and efficiency for short wavelengths, and it almost immediately appeared in high performance audio tape used in audio cassettes for which treble response and hiss were always problems. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |