An envelope is a common packaging item made of thin, flat material. It is designed to contain a flat object, such as card. Traditional envelopes are made from sheets of paper cut to one of three shapes: a rhombus, a short-arm cross or a kite; these shapes allow for the creation of the envelope structure by folding the sheet sides around a central rectangular area. In this manner, a rectangle-faced enclosure is formed with an arrangement of four flaps on the reverse side; when the folding sequence is such that the last flap to be closed is on a short side it is referred to in commercial envelope manufacture as a pocket - a format employed in the packaging of small quantities of seeds. Although in principle the flaps can be held in place by securing the topmost flap at a single point they are pasted or gummed together at the overlaps, they are most used for enclosing and sending mail through a prepaid-postage postal system. Window envelopes have a hole cut in the front side, they are arranged so that the receiving address printed on the letter is visible, saving the sender from having to duplicate the address on the envelope itself.
The window is covered with a transparent or translucent film to protect the letter inside, as was first designed by Americus F. Callahan in 1901 and patented the following year. In some cases, shortages of materials or the need to economize resulted in envelopes that had no film covering the window. One innovative process, invented in Europe about 1905, involved using hot oil to saturate the area of the envelope where the address would appear; the treated area became sufficiently translucent for the address to be readable. As of 2009 there is no international standard for window envelopes, but some countries, including Germany and the United Kingdom, have national standards. An aerogram is related to a lettersheet, both being designed to have writing on the inside to minimize the weight. Any handmade envelope is a lettersheet because prior to the folding stage it offers the opportunity for writing a message on that area of the sheet that after folding becomes the inside of the face of the envelope.
The "envelope" used to launch the Penny Post component of the British postal reforms of 1840 by Sir Rowland Hill and the invention of the postage stamp, was a lozenge-shaped lettersheet known as a Mulready. If desired, a separate letter could be enclosed with postage remaining at one penny provided the combined weight did not exceed half an ounce; this was a legacy of the previous system of calculating postage, which depended on the number of sheets of paper used. During the U. S. Civil War those in the Confederate States Army used envelopes made from wallpaper, due to financial hardship. A "return envelope" is a pre-addressed, smaller envelope included as the contents of a larger envelope and can be used for courtesy reply mail, metered reply mail, or freepost; some envelopes are designed to be reused as the return envelope, saving the expense of including a return envelope in the contents of the original envelope. The direct mail industry makes extensive use of return envelopes as a response mechanism.
Up until 1840, all envelopes were handmade, each being individually cut to the appropriate shape out of an individual rectangular sheet. In that year George Wilson in the United Kingdom patented the method of tessellating a number of envelope patterns across and down a large sheet, thereby reducing the overall amount of waste produced per envelope when they were cut out. In 1845 Edwin Hill and Warren de la Rue obtained a patent for a steam-driven machine that not only cut out the envelope shapes but creased and folded them as well; the convenience of the sheets ready cut to shape popularized the use of machine-made envelopes, the economic significance of the factories that had produced handmade envelopes diminished. As envelopes are made of paper, they are intrinsically amenable to embellishment with additional graphics and text over and above the necessary postal markings; this is a feature that the direct mail industry has long taken advantage of—and more the Mail Art movement. Custom printed envelopes has become an popular marketing method for small business.
Most of the over 400 billion envelopes of all sizes made worldwide are machine-made. International standard ISO 269 defined several standard envelope sizes, which are designed for use with ISO 216 standard paper sizes: The German standard DIN 678 defines a similar list of envelope formats. There are dozens of sizes of envelopes available; the designations such as "A2" do not correspond to ISO paper sizes. The No. 10 envelope is the standard business envelope size in the United States. Envelopes accepted by the U. S. Postal Service for mailing at the price of a letter must be: Rectangular At least 3 1⁄2 inches high × 5 inches long × 0.007 inch thick. No more than 6 1⁄8 inches high × 11 1⁄2 inches long × 1⁄4 inch thick. Letters that have a length-to-height aspect ratio of less than 1.3 or more than 2.5 are classified as "non-machinable" by the USPS and may cost more to mail. Check out Central Mailing Services infographic here for the general sizes of envelopes in the United Kingdom; the first known envelope was nothing like the paper envelope of today.
It can be dated back to around 3500 to 3200 BC in the ancient Middle East. Hollow, clay spheres were used in private transactions; the two people who discovered these first envelopes were Jacque
A preface or proem is an introduction to a book or other literary work written by the work's author. An introductory essay written by a different person precedes an author's preface; the preface closes with acknowledgments of those who assisted in the literary work. A preface covers the story of how the book came into being, or how the idea for the book was developed. A preface is signed. Information essential to the main text is placed in a set of explanatory notes, or in an "Introduction" that may be paginated with Arabic numerals, rather than in the preface; the term preface can mean any preliminary or introductory statement. It is sometimes abbreviated pref. Preface comes from the Latin, meaning either "spoken before" or "made before". While the former source of the word could have preface meaning the same as prologue, the latter implies an introduction written before the body of the book. With this meaning of stated intention, British publishing up to at least the middle of the twentieth century distinguished between preface and introduction.
Epigraph Exordium Introduction Postface Prologue A history of the preface in several languages is contained in: Tötösy de Zepetnek, Steven. The Social Dimensions of Fiction: On the Rhetoric and Function of Prefacing Novels in the Nineteenth-Century Canadas. Braunschweig-Wiesbaden: Westdeutscher, 1993. CLCWeb: Comparative Literature and Culture; the difference between a preface and introduction, patmcnees.com Media related to Prefaces at Wikimedia Commons The dictionary definition of proem at Wiktionary
A Prontor-Compur connection is a standard 3.5 mm electrical connector used in photography to synchronize the shutter to the flash. "Prontor" has its origins in the Italian word "pronto", meaning ready. "Compur" is derived from the word "compound". The term is derived from brands of marketed photographic leaf shutters manufactured from the early 1950s by two distinct, but now defunct German companies. Gauthier and Deckel. Both companies' brands and Compur, shared a common 1/8"-inch coaxial connector for shutter/flash synchronization; this convergence of design is not as coincidental as it might first appear, owing to the fact that the Zeiss organisation held a significant shareholding in both of these companies prior to the introduction of the shared connector. By the 1950s, Gauthier were manufacturing up to 10,000 Prontor shutters daily; the Gauthier company's essence lives on as Prontor GmbH, a wholly owned subsidiary of VTC Industrieholding GmbH. The Deckel company went bankrupt in 1994. Flash synchronization Flash
A foreword is a piece of writing sometimes placed at the beginning of a book or other piece of literature. Written by someone other than the primary author of the work, it tells of some interaction between the writer of the foreword and the book's primary author or the story the book tells. Editions of a book sometimes have a new foreword prepended, which might explain in what respects that edition differs from previous ones; when written by the author, the foreword may cover the story of how the book came into being or how the idea for the book was developed, may include thanks and acknowledgments to people who were helpful to the author during the time of writing. Unlike a preface, a foreword is always signed. Information essential to the main text is placed in a set of explanatory notes, or in an introduction, rather than in the foreword or preface; the pages containing the foreword and preface are not numbered as part of the main work, which uses Arabic numerals. If the front matter is paginated, it uses lowercase Roman numerals.
If there is both a foreword and a preface, the foreword appears first. The word foreword was first used around the mid-17th century as a term in philology, it was a calque of German Vorwort, itself a calque of Latin praefatio. Afterword Epigraph Introduction Preface Prologue The difference between a preface and introduction – PatMcNees.com
Arabic numerals are the ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. It is the most common system for the symbolic representation of numbers in the world today; the Hindu-Arabic numeral system was developed by Indian mathematicians around AD 500 using quite different forms of the numerals. From India, the system was adopted by Arabic mathematicians in Baghdad and passed on to the Arabs farther west; the current form of the numerals developed in North Africa. It was in the North African city of Bejaia that the Italian scholar Fibonacci first encountered the numerals; the use of Arabic numerals spread around the world through European trade and colonialism. The term Arabic numerals is ambiguous, it may be intended to mean the numerals used by Arabs, in which case it refers to the Eastern Arabic numerals. Although the phrase "Arabic numeral" is capitalized, it is sometimes written in lower case: for instance in its entry in the Oxford English Dictionary, which helps to distinguish it from "Arabic numerals" as the Eastern Arabic numerals.
Alternative names are Western Arabic numerals, Western numerals, Hindu–Arabic numerals, Unicode calls them digits. The decimal Hindu–Arabic numeral system with zero was developed in India by around AD 700; the development was gradual, spanning several centuries, but the decisive step was provided by Brahmagupta's formulation of zero as a number in AD 628. The system was revolutionary by including zero in positional notation, thereby limiting the number of individual digits to ten, it is considered an important milestone in the development of mathematics. One may distinguish between this positional system, identical throughout the family, the precise glyphs used to write the numerals, which varied regionally; the first universally accepted inscription containing the use of the 0 glyph in India is first recorded in the 9th century, in an inscription at Gwalior in Central India dated to 870. Numerous Indian documents on copper plates exist, with the same symbol for zero in them, dated back as far as the 6th century AD, but their dates are uncertain.
Inscriptions in Indonesia and Cambodia dating to AD 683 have been found. The numeral system came to be known to the court of Baghdad, where mathematicians such as the Persian Al-Khwarizmi, whose book On the Calculation with Hindu Numerals was written about 825 in Arabic, the Arab mathematician Al-Kindi, who wrote four volumes, On the Use of the Indian Numerals about 830, propagated it in the Arab world, their work was principally responsible for the diffusion of the Indian system of numeration in the Middle East and the West. In the 10th century, Middle-Eastern mathematicians extended the decimal numeral system to include fractions, as recorded in a treatise by Syrian mathematician Abu'l-Hasan al-Uqlidisi in 952–953; the decimal point notation was introduced by Sind ibn Ali, who wrote the earliest treatise on Arabic numerals. A distinctive West Arabic variant of the symbols begins to emerge around the 10th century in the Maghreb and Al-Andalus, which are the direct ancestor of the modern "Arabic numerals" used throughout the world.
Woepecke has proposed that the Western Arabic numerals were in use in Spain before the arrival of the Moors, purportedly received via Alexandria, but this theory is not accepted by scholars. Some popular myths have argued that the original forms of these symbols indicated their numeric value through the number of angles they contained, but no evidence exists of any such origin. In 825 Al-Khwārizmī wrote a treatise in Arabic, On the Calculation with Hindu Numerals, which survives only as the 12th-century Latin translation, Algoritmi de numero Indorum. Algoritmi, the translator's rendition of the author's name, gave rise to the word algorithm; the first mentions of the numerals in the West are found in the Codex Vigilanus of 976. From the 980s, Gerbert of Aurillac used his position to spread knowledge of the numerals in Europe. Gerbert studied in Barcelona in his youth, he was known to have requested mathematical treatises concerning the astrolabe from Lupitus of Barcelona after he had returned to France.
Leonardo Fibonacci, a mathematician born in the Republic of Pisa who had studied in Béjaïa, promoted the Indian numeral system in Europe with his 1202 book Liber Abaci: When my father, appointed by his country as public notary in the customs at Bugia acting for the Pisan merchants going there, was in charge, he summoned me to him while I was still a child, having an eye to usefulness and future convenience, desired me to stay there and receive instruction in the school of accounting. There, when I had been introduced to the art of the Indians' nine symbols through remarkable teaching, knowledge of the art soon pleased me above all else and I came to understand it; the numerals are arranged with their lowest value digit to the right, with higher value positions added to the left. This arrangement is the same in Arabic as well as the Indo-European languages; the reason the digits are more known as "Arabic numerals" in Europe and the Americas is that they were introduced to Europe in the 10th century by Arabic-speakers of North Africa, who were using the digits from Libya to Morocco.
Arabs, on the other hand, call the base-10 system "Hindu numerals", referring to their origin in India. This is not to be confused with what the Arabs call the "Hindi numerals", namely the Eastern Arabi
A power take-off or power takeoff is any of several methods for taking power from a power source, such as a running engine, transmitting it to an application such as an attached implement or separate machines. Most it is a splined drive shaft installed on a tractor or truck allowing implements with mating fittings to be powered directly by the engine. Semi-permanently mounted power take-offs can be found on industrial and marine engines; these applications use a drive shaft and bolted joint to transmit power to a secondary implement or accessory. In the case of a marine application, such shafts may be used to power fire pumps. In aircraft applications, such an accessory drive may be used in conjunction with a constant speed drive. Jet aircraft have four types of PTO units: internal gearbox, external gearbox, radial drive shaft, bleed air, which are used to power engine accessories. In some cases, aircraft power take-off systems provide for putting power into the engine during engine start. See Coffman starter Various power transmission methods were available before power takeoffs became common, but there were applications left wanting for some of the attributes that PTOs would provide.
Flat belts lent themselves only to applications where the engine was stationary, such as factory steam engines, portable stationary engines, or traction engines parked in front of the work. For moving vehicles such as a traction engine or early tractor towing a farm implement, the implement could receive rotary power by taking it from one of its own wheels and distributing it via roller chains, but such a transmission ceases if the vehicle stops traveling; the concept of a shaft drive with connected and disconnected couplings, flexibility for driving at changing angles, was a goal to pursue. Experimental power take-offs were tried as early as 1878, various homemade versions arose over the subsequent decades. International Harvester Company was first to market with a PTO on a production tractor, with its model 8-16, introduced in 1918. Edward A. Johnston, an IHC engineer, had been impressed by a homemade PTO that he saw in France about a decade before, improvised by a French farmer and mechanic surnamed Gougis.
He and his IHC colleagues incorporated the idea into the 8-16, designed a family of implements to take advantage of the feature. IHC was not alone in the market for long, as within a year PTOs were appearing on other production tractors, such as some Case models. In 1920, IHC offered the PTO option on their 15-30 tractor, it was the first PTO-equipped tractor to be submitted for a Nebraska tractor test; the PTO was a competitive advantage for IHC in the 1920s, other companies caught up with PTO implementation. Inside the transmission, the exact point along the gear train where the power is taken off determines whether the PTO can be run independently of vehicle travel. Early PTOs were taken off the main output shaft, meaning that the vehicle had to be "in gear" in order to run the PTO; this was improved by so-called live PTO designs, which allow control of the PTO rotation independently of the tractor motion. This is an advantage when the load driven by the PTO requires the tractor motion to slow or stop running to allow the PTO driven equipment to catch up.
It allows operations where the tractor remains parked, such as silo-filling or unloading a manure spreader to a pile or lagoon rather than across a field. In 1945, Cockshutt Farm Equipment Ltd of Brantford, Canada, introduced the Cockshutt Model 30 tractor with LPTO. Most PTOs built today are live. In modern tractors, LPTO is controlled by push-button or selector switch; this increases safety of operators. The PTO and its associated shafts and universal joints are a common cause of incidents and injury in farming and industry. According to the National Safety Council, 6 percent of tractor related fatalities in 1997 in the United States involved the PTO. Incidents can occur when loose clothing is pulled into the shaft resulting in bone fractures, loss of limb, or death to its wearer. On April 13, 2009 former Major League Baseball star Mark Fidrych died as a result of a PTO related accident. Despite much work to reduce the frequency and severity of agricultural injuries, these events still occur.
Power take-off entanglements are one example of agricultural events that can lead to death or permanent disability. Some implements employ light free-spinning protective plastic guards to enshroud the PTO shaft, are mandatory in some countries. In the UK, Health and Safety Executive guidance is contained in a leaflet. Agricultural PTOs are standardized in dimensions and speed; the ISO standard for PTOs is ISO 500, which as of the 2004 edition was split into three parts: ISO 500-1 General specifications, safety requirements, dimensions for master shield and clearance zone ISO 500-2 Narrow-track tractors, dimensions for master shield and clearance zone ISO 500-3 Main PTO dimensions and spline dimensions, location of PTO. The original type calls for operation at 540 revolutions per minute. A shaft that rotates at 540 rpm has 6 splines on it, a diameter of 13⁄8". Two newer types, supporting higher power applications, differ in shaft size; the larger shaft has 20 splines, while the smaller has 21
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras. Insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, is thus termed a slow film. Sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities leads to reduced image quality. In short, the higher the sensitivity, the grainier the image will be. Sensitivity is limited by the quantum efficiency of the film or sensor; the first known practical sensitometer, which allowed measurements of the speed of photographic materials, was invented by the Polish engineer Leon Warnerke – pseudonym of Władysław Małachowski – in 1880, among the achievements for which he was awarded the Progress Medal of the Photographic Society of Great Britain in 1882.
It was commercialized since 1881. The Warnerke Standard Sensitometer consisted of a frame holding an opaque screen with an array of 25 numbered pigmented squares brought into contact with the photographic plate during a timed test exposure under a phosphorescent tablet excited before by the light of a burning magnesium ribbon; the speed of the emulsion was expressed in'degrees' Warnerke corresponding with the last number visible on the exposed plate after development and fixation. Each number represented an increase of 1/3 in speed, typical plate speeds were between 10° and 25° Warnerke at the time, his system saw some success but proved to be unreliable due to its spectral sensitivity to light, the fading intensity of the light emitted by the phosphorescent tablet after its excitation as well as high built-tolerances. The concept, was built upon in 1900 by Henry Chapman Jones in the development of his plate tester and modified speed system. Another early practical system for measuring the sensitivity of an emulsion was that of Hurter and Driffield described in 1890, by the Swiss-born Ferdinand Hurter and British Vero Charles Driffield.
In their system, speed numbers were inversely proportional to the exposure required. For example, an emulsion rated at 250 H&D would require ten times the exposure of an emulsion rated at 2500 H&D; the methods to determine the sensitivity were modified in 1925 and in 1928 —this variant was sometimes called "H&D 10". The H&D system was accepted as a standard in the former Soviet Union from 1928 until September 1951, when it was superseded by GOST 2817-50; the Scheinergrade system was devised by the German astronomer Julius Scheiner in 1894 as a method of comparing the speeds of plates used for astronomical photography. Scheiner's system rated the speed of a plate by the least exposure to produce a visible darkening upon development. Speed was expressed in degrees Scheiner ranging from 1° Sch. to 20° Sch. where an increment of 19° Sch. corresponded to a hundredfold increase in sensitivity, which meant that an increment of 3° Sch. came close to a doubling of sensitivity. 100 19 3 = 2.06914... ≈ 2 The system was extended to cover larger ranges and some of its practical shortcomings were addressed by the Austrian scientist Josef Maria Eder and Flemish-born botanist Walter Hecht.
Still, it remained difficult for manufactures to reliably determine film speeds only by comparing with competing products, so that an increasing number of modified semi-Scheiner-based systems started to spread, which no longer followed Scheiner's original procedures and thereby defeated the idea of comparability. Scheiner's system was abandoned in Germany, when the standardized DIN system was introduced in 1934. In various forms, it continued to be in widespread use in other countries for some time; the DIN system DIN standard 4512 by Deutsches Institut für Normung, was published in January 1934. It grew out of drafts for a standardized method of sensitometry put forward by Deutscher Normenausschuß für Phototechnik as proposed by the committee for sensitometry of the Deutsche Gesellschaft für photographische Forschung since 1930 and presented by Robert Luther and Emanuel Goldberg at the influential VIII. International Congress of Photography held in Dresden from August 3 to 8, 1931; the DIN system was inspired by Scheiner's system, but the sensitivities were represented as the base 10 logarithm of the sensitivity multiplied by 10, similar to decibels.
Thus an increase of 20° represented a hundredfold increase in sensitivity, a difference of 3° was much closer to the base 10 logarithm of 2: log 10 = 0.30103... ≈ 3 / 10 As in the Sche