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Thermochromic Ink
Thermochromic ink (also called thermochromatic ink) is a type of dye that changes color when temperatures increase or decrease. Often used in the manufacture of many toys or product packaging, as well as thermometers. Thermochromic ink can also turn transparent when heat is applied; an example of this type of thermochromic ink is found on corners of an examination mark sheet. This proves that the sheet has not been edited or photocopied, and also on certain pizza boxes to show the temperature of the product. Use on packaging can be to detect temperature history during shipping and to indicate proper heating in an oven. Examples On June 20, 2017, the United States Postal Service released the first application of thermochromic ink to postage stamps in its Total Eclipse of the Sun Forever stamp to commemorate the solar eclipse of August 21, 2017. When pressed with a finger, body heat turns the black circle in the center of the stamp into an image of the full moon. The stamp imag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperatures
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on various reference points and thermometric substances for definition. The most common scales are the Celsius scale with the unit symbol °C (formerly called ''centigrade''), the Fahrenheit scale (°F), and the Kelvin scale (K), the latter being used predominantly for scientific purposes. The kelvin is one of the seven base units in the International System of Units (SI). Absolute zero, i.e., zero kelvin or −273.15 °C, is the lowest point in the thermodynamic temperature scale. Experimentally, it can be approached very closely but not actually reached, as recognized in the third law of thermodynamics. It would be impossible to extract energy as heat from a body at that temperature. Temperature is important in all fields of natura ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Eclipse Of August 21, 2017
The solar eclipse of August 21, 2017, dubbed the "Great American Eclipse" by the media, was a total solar eclipse visible within a band that spanned the contiguous United States from the Pacific to the Atlantic coasts. It was also visible as a partial solar eclipse from as far north as Nunavut in northern Canada to as far south as northern South America. In northwestern Europe and Africa, it was partially visible in the late evening. In northeastern Asia, it was partially visible at sunrise. Prior to this event, no solar eclipse had been visible across the entirety of the United States since June 8, 1918; not since the February 1979 eclipse had a total eclipse been visible from anywhere in the mainland United States. The path of totality touched 14 states, and the rest of the U.S. had a partial eclipse. The area of the path of totality was about 16 percent of the area of the United States, with most of this area over the ocean, not land. The event's shadow began to cover land ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Security Printing
Security printing is the field of the printing industry that deals with the printing of items such as banknotes, cheques, passports, tamper-evident labels, security tapes, product authentication, stock certificates, postage stamps and identity cards. The main goal of security printing is to prevent forgery, tampering, or counterfeiting. More recently many of the techniques used to protect these high-value documents have become more available to commercial printers, whether they are using the more traditional offset and flexographic presses or the newer digital platforms. Businesses are protecting their lesser-value documents such as transcripts, coupons and prescription pads by incorporating some of the features listed below to ensure that they cannot be forged or that alteration of the data cannot occur undetected. A number of technical methods are used in the security printing industry. Security printing is most often done on security paper, but it can also occur on plastic mate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermochromism
Thermochromism is the property of substances to change color due to a change in temperature. A mood ring is an excellent example of this phenomenon, but thermochromism also has more practical uses, such as baby bottles which change to a different color when cool enough to drink, or kettles which change color when water is at or near boiling point. Thermochromism is one of several types of chromism. Organic materials Thermochromatic liquid crystals The two common approaches are based on liquid crystals and leuco dyes. Liquid crystals are used in precision applications, as their responses can be engineered to accurate temperatures, but their color range is limited by their principle of operation. Leuco dyes allow wider range of colors to be used, but their response temperatures are more difficult to set with accuracy. Some liquid crystals are capable of displaying different colors at different temperatures. This change is dependent on selective reflection of certain wavelengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fred Espenak
Fred Espenak is a retired emeritus American astrophysicist. He worked at the Goddard Space Flight Center. He is best known for his work on eclipse predictions. He became interested in astronomy when he was 7–8 years old, and had his first telescope when he was around 9–10 years old. Espenak earned a bachelor's degree in physics from Wagner College, Staten Island, where he worked in the planetarium. His master's degree is from the University of Toledo, based on studies he did at Kitt Peak Observatory of eruptive and flare stars among red dwarfs. He was employed at Goddard Space Flight Center, where he used infrared spectrometers to measure the atmospheres of planets in the Solar System. He provided NASA's eclipse bulletins since 1978. He is the author of several canonical works on eclipse predictions, such as the ''Fifty Year Canon of Solar Eclipses: 1986–2035'' and ''Fifty Year Canon of Lunar Eclipses: 1986–2035'', both of which are standard references on eclipses ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Libya
Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to Egypt–Libya border, the east, Sudan to Libya–Sudan border, the southeast, Chad to Chad–Libya border, the south, Niger to Libya–Niger border, the southwest, Algeria to Algeria–Libya border, the west, and Tunisia to Libya–Tunisia border, the northwest. Libya is made of three historical regions: Tripolitania, Fezzan, and Cyrenaica. With an area of almost 700,000 square miles (1.8 million km2), it is the fourth-largest country in Africa and the Arab world, and the List of countries and outlying territories by total area, 16th-largest in the world. Libya has the List of countries by proven oil reserves, 10th-largest proven oil reserves in the world. The largest city and capital, Tripoli, Libya, Tripoli, is located in western Libya and contains over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jalu
Jalu, Jallow, or Gialo ( ar, جالو) is a town in the Al Wahat District in northeastern Libya in the Jalo oasis. An oasis, a city, and it is the main center of the oasis region in eastern Libya. It is located at the confluence of longitude and latitude (21-29), and the most important characteristic of visitors and onlookers is the presence of dense palm forests linking the sand dunes and plateaus of the Libyan desert. Its inhabitants were famous for trade and transporting goods from Cyrenaica and Tripoli to (Chad, Egypt and Sudan) and other African countries. It is an ancient oasis mentioned by Arab travelers, and orientalists in many historical sources. Historical sources mention that the people of the Jallow oasis were the first to conduct trade caravans along the longest desert route from The Libyan coast to central and eastern Africa around the middle of the nineteenth century and the beginning of the twentieth century. Notable people * Abu-Bakr Yunis Jabr (1952-2011) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Full Moon
The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic coordinate system, ecliptic longitudes of the Sun and Moon opposition (astronomy), differ by 180°). This means that the lunar hemisphere facing Earth—the near side of the Moon, near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month. The time interval between a full moon and the next repetition of the same phase, a Lunar month#Synodic month, synodic month, averages about 29.53 days. Therefore, in those lunar calendars in which each month begins on the day of the new moon, the full moon falls on either the 14th or 15th day of the lunar month. Because a calendar month consists of a Natural number, whole number of days, a month in a lunar calendar may be either 29 or 30 days long. Characteristics A full moon is often thought of as an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Eclipse
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six months, during the new moon phase, when the Moon's orbital plane is closest to the plane of the Earth's orbit. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured. Unlike a lunar eclipse, which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years. If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses once a month, at every new moon. Instead, because the Moon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transparency And Translucency
In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions are much larger than the wavelengths of the photons in question), the photons can be said to follow Snell's law. Translucency (also called translucence or translucidity) allows light to pass through, but does not necessarily (again, on the macroscopic scale) follow Snell's law; the photons can be scattered at either of the two interfaces, or internally, where there is a change in index of refraction. In other words, a translucent material is made up of components with different indices of refraction. A transparent material is made up of components with a uniform index of refraction. Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. The opposit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2017 Total Solar Eclipse Stamp
The United States Postal Service issued the Total Eclipse of the Sun Forever stamp on June 20, 2017. The stamp includes two superimposed images, one showing a total solar eclipse and the second showing a full moon that is revealed upon heat being applied. This stamp commemorates the solar eclipse of August 21, 2017 which was visible across the continental United States from coast to coast, weather permitting. Details In the first U.S. stamp application of thermochromic ink, the Total Eclipse of the Sun Forever stamps reveal a second image. By rubbing a thumb or finger on the image, the heat imparted will cause an underlying image of the full moon to be revealed. Afterward, the image reverts to the dark image as it cools. The US Postal Service notes that exposure to ultraviolet (UV) light causes degradation of thermochromic inks, so the eclipse stamps should be shielded from sunlight to preserve their thermochromic behavior. To help with this, the Postal Service sends panes of thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Postal Service
The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the U.S., including its insular areas and associated states. It is one of the few government agencies explicitly authorized by the U.S. Constitution. The USPS, as of 2021, has 516,636 career employees and 136,531 non-career employees. The USPS traces its roots to 1775 during the Second Continental Congress, when Benjamin Franklin was appointed the first postmaster general; he also served a similar position for the colonies of the Kingdom of Great Britain. The Post Office Department was created in 1792 with the passage of the Postal Service Act. It was elevated to a cabinet-level department in 1872, and was transformed by the Postal Reorganization Act of 1970 into the U.S. Postal Service as an independent agency. Since the early 1980s, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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