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Ionospheric Remote Sensing with GNSS
The Global Navigation Satellite System (GNSS) plays a pivotal role in our modern positioning, navigation and timing (PNT) technologies. GNSS satellites fly at altitudes of approximately 20,000 km or higher. This altitude is above an ionized layer of the Earth’s upper atmosphere, the so called “ionosphere”. Before reaching a typical GNSS receiver on the ground, GNSS satellite signals penetrate through the Earth’s ionosphere. The ionosphere is a plasma medium consisting of free charged particles that can slow down, attenuate, refract, or scatter the GNSS signals. Ionospheric density structures (also known as irregularities) can cause GNSS signal scintillations (phase and intensity fluctuations). These ionospheric impacts on GNSS signals can be utilized to observe and study physical processes in the ionosphere and is referred to ionospheric remote sensing. This entry introduces some fundamentals of ionospheric remote sensing using GNSS. 
  • 5.2K
  • 13 Apr 2022
Topic Review
Social Environment and Environmental Attitudes
Social environment may the formation of citizens' attitudes toward the natural environment, namely, the environmental attitudes.
  • 5.2K
  • 15 Nov 2021
Topic Review
Specific Relative Angular Momentum
In celestial mechanics the specific relative angular momentum [math]\displaystyle{ \vec{h} }[/math] plays a pivotal role in the analysis of the two-body problem. One can show that it is a constant vector for a given orbit under ideal conditions. This essentially proves Kepler's second law. It's called specific angular momentum because it's not the actual angular momentum [math]\displaystyle{ \vec{L} }[/math], but the angular momentum per mass. Thus, the word "specific" in this term is short for "mass-specific" or divided-by-mass: Thus the SI unit is: m2·s−1. [math]\displaystyle{ m }[/math] denotes the reduced mass [math]\displaystyle{ \frac{1}{m} = \frac{1}{m_1}+\frac{1}{m_2} }[/math].
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  • 11 Nov 2022
Topic Review
Carbonatite-Related REE Deposits
The rare earth elements (REEs) have unique and diverse properties that make them function as an “industrial vitamin” and thus, many countries consider them as strategically important resources. China, responsible for more than 60% of the world’s REE production, is one of the REE‐rich countries in the world. Most REE (especially light rare earth elements (LREE)) deposits are closely related to carbonatite in China. Such a type of deposit may also contain appreciable amounts of industrially critical metals, such as Nb, Th and Sc. According to the genesis, the carbonatite‐related REE deposits can be divided into three types: primary magmatic type, hydrothermal type and carbonatite weathering‐crust type. This paper provides an overview of the carbonatite‐related endogenetic REE deposits, i.e., primary magmatic type and hydrothermal type. The carbonatite‐related endogenetic REE deposits are mainly distributed in continental margin depression or rift belts, e.g., Bayan Obo REE‐Nb‐Fe deposit, and orogenic belts on the margin of craton such as the Miaoya Nb‐REE deposit. The genesis of carbonatite‐related endogenetic REE deposits is still debated. It is generally believed that the carbonatite magma is originated from the low‐degree partial melting of the mantle. During the evolution process, the carbonatite rocks or dykes rich in REE were formed through the immiscibility of carbonate-silicate magma and fractional crystallization of carbonate minerals from carbonatite magma. The ore‐forming elements are mainly sourced from primitive mantle, with possible contribution of crustal materials that carry a large amount of REE. In the magmatic-hydrothermal system, REEs migrate in the form of complexes, and precipitate corresponding to changes of temperature, pressure, pH and composition of the fluids. A simple magmatic evolution process cannot ensure massive enrichment of REE to economic values. Fractional crystallization of carbonate minerals and immiscibility of melts and hydrothermal fluids in the hydrothermal evolution stage play an important role in upgrading the REE mineralization. Future work of experimental petrology will be fundamental to understand the partitioning behaviors of REE in magmatic-hydrothermal system through simulation of the metallogenic geological environment. Applying “comparative metallogeny” methods to investigate both REE fertile and barren carbonatites will enhance the understanding of factors controlling the fertility.
  • 5.2K
  • 17 Nov 2020
Topic Review
Production and Use of Typical Rubber Antioxidants
Antioxidants are prevalently used during rubber production to improve rubber performance, delay aging, and extend service life. Studies have revealed that their transformation products (TPs) could adversely affect environmental organisms and even lead to environmental events, which led to great public concern about environmental occurrence and potential impacts of rubber antioxidants and their TPs.
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  • 22 Dec 2022
Topic Review
Pulmonary Artery Catheter
Pulmonary artery catheterization (PAC), or right heart catheterization, is the insertion of a catheter into a pulmonary artery. Its purpose is diagnostic; it is used to detect heart failure or sepsis, monitor therapy, and evaluate the effects of drugs. The pulmonary artery catheter allows direct, simultaneous measurement of pressures in the right atrium, right ventricle, pulmonary artery, and the filling pressure ("wedge" pressure) of the left atrium. The pulmonary artery catheter is frequently referred to as a Swan-Ganz catheter, in honor of its inventors Jeremy Swan and William Ganz, from Cedars-Sinai Medical Center.
  • 5.2K
  • 24 Nov 2022
Topic Review
List of Meteor Air Bursts
Many explosions recorded in Earth's atmosphere are likely to be caused by the air bursts that result from meteors exploding as they hit the thicker part of the atmosphere. These types of meteors are also known as fireballs or bolides with the brightest known as superbolides. Before entering Earth's atmosphere, these larger meteors were originally asteroids and comets of a few to several tens of metres in diameter, contrasting with the much smaller and much more common "shooting stars". The most powerful recorded air burst is the 1908 Tunguska event. Extremely bright fireballs traveling across the sky are often witnessed from a distance, such as the 1947 Sikhote-Alin meteor and the 2013 Chelyabinsk meteor, both in Russia. If the bolide is large enough, fragments may survive such as the Chelyabinsk meteorite. Modern developments in infrasound detection by the Comprehensive Nuclear-Test-Ban Treaty Organization and infrared Defense Support Program satellite technology have increased the likelihood of detecting airbursts.
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  • 11 Nov 2022
Topic Review
Production Methods of Peptides
Peptides are organic polymers composed of 2–50 amino acids linked to each other by means of covalent amide (=peptide) bonds. The composition, length and sequence of the amino acid chain have a dramatic influence on the activity of the peptide itself, for example in the human body. Peptides are called bioactive if they have a beneficial impact on body functions, on biological processes and, as a consequence, on health. The main production methods to obtain peptides are enzymatic hydrolysis, microbial fermentation, recombinant approach and, especially, chemical synthesis. 
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  • 01 Sep 2021
Topic Review
Georg Cantor's First Set Theory Article
Georg Cantor published his first set theory article in 1874, and it contains the first theorems of transfinite set theory, which studies infinite sets and their properties. One of these theorems is "Cantor's revolutionary discovery" that the set of all real numbers is uncountably, rather than countably, infinite. This theorem is proved using Cantor's first uncountability proof, which differs from the more familiar proof using his diagonal argument. The title of the article, "On a Property of the Collection of All Real Algebraic Numbers" ("Ueber eine Eigenschaft des Inbegriffes aller reellen algebraischen Zahlen"), refers to its first theorem: the set of real algebraic numbers is countable. Cantor's article also contains a proof of the existence of transcendental numbers. As early as 1930, mathematicians have disagreed on whether this proof is constructive or non-constructive. Books as recent as 2014 and 2015 indicate that this disagreement has not been resolved. Since Cantor's proof either constructs transcendental numbers or does not, an analysis of his article can determine whether his proof is constructive or non-constructive. Cantor's correspondence with Richard Dedekind shows the development of his ideas and reveals that he had a choice between two proofs, one that uses the uncountability of the real numbers and one that does not. Historians of mathematics have examined Cantor's article and the circumstances in which it was written. For example, they have discovered that Cantor was advised to leave out his uncountability theorem in the article he submitted; he added it during proofreading. They have traced this and other facts about the article to the influence of Karl Weierstrass and Leopold Kronecker. Historians have also studied Dedekind's contributions to the article, including his contributions to the theorem on the countability of the real algebraic numbers. In addition, they have looked at the article's legacy, which includes the impact that the uncountability theorem and the concept of countability have had on mathematics.
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  • 02 Nov 2022
Topic Review
Tomato and Olive Oil in Prostate Health
Tomato, the fruit providing the most comprehensive complex of prostate-health-preserving micronutrients, has been shown to be superior to its single-nutrient counterparts in decreasing the incidence of age-related prostate diseases.
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  • 30 Mar 2023
Topic Review
Structure, Spectral Properties and Chemistry of Spiropyrans
Spiropyrans (SP) are a well-studied class of photochromic compounds. These compounds are usually named in conformity with the IUPAC rules for nomenclature of heterocyclic spirocompounds, as derivatives of 1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline] or 1′,3′-dihydro-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indole].
  • 5.2K
  • 11 Jul 2023
Topic Review
Continuous Casting Practices for Steel
Continuous casting practices for steelmaking have been constantly evolving ever since the early 1930s, when Junghans was first researching ways to pour liquid steel into an open-bottomed, water-cooled mold, to withdraw the partially solidified steel out of it, continuously, in the form of a round or square billet or slab. He envisioned that once these continuously cast shapes had become fully frozen, their solidified ends could be cut off for further processing. In this way, they could be transformed into “rebar” to reinforce concrete, or into bars from which nails, bolts, tire cord wire, etc., could be fashioned, etc. However, long before that, Sir Henry Bessemer had proposed a far more elegant approach, involving two, contra-rotating rolls, into which liquid steel is poured, to produce a thin solidified sheet of steel directly, within a few milliseconds. This is referred to as a Near Net Shape Casting Process. After 150 years of trying, CASTRIP, a subsidiary of NUCOR, BHP, and IHI, made this process a commercial success, where many previous attempts had failed. However, there is an even better NNSC process, referred to as HSBC, or "Horizontal Single Belt Casting", that has also been commercially successful. The HSBC process is capable of casting many different grades of steel, unlike the Bessemer CASTRIP process, by casting ~10 - 15mm thick strips, that can then be rolled down to a final sheet ~1.5 - 0.5mm. thickness, in a one-step continuous process.  
  • 5.2K
  • 06 Jun 2022
Topic Review
Kangxi Radical
The 214 Kangxi radicals (Chinese: 康熙部首; pinyin: Kāngxī bùshǒu), also known as the Zihui radicals, form a system of radicals (部首) of Chinese characters. The radicals are numbered in stroke count order. They are the most popular system of radicals for dictionaries that order Traditional Chinese characters (hanzi, hanja, kanji, chữ hán) by radical and stroke count. They are officially part of the Unicode encoding system for CJKV characters, in their standard order, under the coding block "Kangxi radicals", while their graphic variants are contained in the "CJK Radicals Supplement". Thus, a reference to "radical 61", for example, without additional context, refers to the 61st radical of the Kangxi Dictionary, 心; xīn "heart". Originally introduced in the 1615 Zihui (字彙), they are more commonly named in relation to the Kangxi Dictionary of 1716 (Kāngxī 康熙 being the era name for 1662–1723). The 1915 encyclopedic word dictionary Ciyuan (辭源) also uses this system. In modern times, many dictionaries that list Traditional Chinese head characters continue to use this system. For example, the Wang Li Character Dictionary of Ancient Chinese (王力古漢語字典, 2000) adopted the Kangxi radicals system. The system of 214 Kangxi radicals is based on the older system of 540 radicals used in the Han-era Shuowen Jiezi. Since 2009, the PRC government has promoted a 201-radical system (Table of Han Character Radicals, 汉字部首表) as a national standard for Simplified Chinese (see list of Xinhua Zidian radicals).
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  • 22 Nov 2022
Topic Review
Republic
A republic (Latin: res publica, meaning "public affair") is a form of government in which the country is considered a "public matter", not the private concern or property of the rulers. The primary positions of power within a republic are attained, through democracy, oligarchy, or a mix thereof, rather than being unalterably occupied. It has become the opposing form of government to a monarchy and has therefore no monarch as head of state. (As of 2017), 159 of the world's 206 sovereign states use the word "republic" as part of their official names – not all of these are republics in the sense of having elected governments, nor is the word "republic" used in the names of all nations with elected governments. The word republic comes from the Latin term res publica, which literally means "public thing", "public matter", or "public affair" and was used to refer to the state as a whole. The term developed its modern meaning in reference to the constitution of the ancient Roman Republic, lasting from the overthrow of the kings in 509 BC to the establishment of the Empire in 27 BC. This constitution was characterized by a Senate composed of wealthy aristocrats and wielding significant influence; several popular assemblies of all free citizens, possessing the power to elect magistrates and pass laws; and a series of magistracies with varying types of civil and political authority. Most often a republic is a single sovereign state, but there are also sub-sovereign state entities that are referred to as republics, or that have governments that are described as "republican" in nature. For instance, Article IV of the United States Constitution "guarantee[s] to every State in this Union a Republican form of Government". Another example is the Soviet Union which described itself as being a group of "Soviet Socialist Republics", in reference to the 15 individually federal, multinational, top-level subdivisions or republics. In the context of American constitutional law, the definition of republic refers specifically to a form of government in which elected individuals represent the citizen body and exercise power according to the rule of law under a constitution, including separation of powers with an elected head of state, referred to as a constitutional republic or representative democracy.
  • 5.2K
  • 16 Nov 2022
Topic Review
Terrestrial Links Rain Attenuation Models
 Rain is a natural process that attenuates the propagating signal at microwave and millimeter-wave frequencies. Therefore, it is necessary to mitigate rain attenuation to ensure the quality of microwave and millimeter-wave links. To this end, dynamic attenuation mitigation methods are implemented alongside attenuation prediction models that can predict the projected attenuation of the links. Studies on rain attenuation are used in geographically distributed locations to analyze and develop a rain attenuation model applicable over a wide frequency range, particularly radio frequencies over approximately 30 GHz for 5G and beyond network applications.
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  • 02 Jun 2021
Topic Review
IoT-Enabled Smart Agriculture
The growth of the global population coupled with a decline in natural resources, farmland, and the increase in unpredictable environmental conditions leads to food security is becoming a major concern for all nations worldwide. These problems are motivators that are driving the agricultural industry to transition to smart agriculture with the application of the Internet of Things (IoT) and big data solutions to improve operational efficiency and productivity. The IoT integrates a series of existing state-of-the-art solutions and technologies, such as wireless sensor networks, cognitive radio ad hoc networks, cloud computing, big data, and end-user applications. IoT is defined as the network of all objects that are embedded within devices, sensors, machines, software and people through the Internet environment to communicate, exchange information and interact in order to provide a comprehensive solution between the real world and the virtual world.
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  • 01 Apr 2022
Topic Review
Thin-Film Magnetoelastic Materials Based Devices
Thin-film magnetoelastic materials, which couple the magnetization and strain together, have recently attracted ever-increasing attention due to their key roles in magnetoelectric applications. This review starts with the fabrication and characterization techniques in the field of magnetoelastic materials and introduces various kinds of devices utilizing ME effect.
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  • 04 Nov 2020
Topic Review
A2 Milk and CMPA
 Cows’ milk generally contains two major types of beta-casein as A1 and A2 types, although there are 13 genetic variants of β-casein: A1, A2, A3, A4, B, C, D, E, F, H1, H2, I and G. Studies have shown that A1 β-casein may be harmful, and A2 β-casein is a safer choice for human health especially in infant nutrition and health. The A2 cow milk is reportedly easier to digest and better absorb than A1 or other types of milk. The structure of A2 cow’s milk protein is more comparable to human breast milk, as well as milk from goats, sheep and buffalo. Cow milk protein allergy (CMPA) is considered a common milk digestive and metabolic disorder or allergic disease with various levels of prevalence from 2.5% in children during the first 3 years of life to 12–30% in infants less than 3 months old, and it can go up to even as high as 20% in some countries. CMPA is an IgE-mediated allergy where the body starts to produce IgE antibodies against certain protein (allergens) such as A1 milk and αs1-casein in bovine milk. Studies have shown that ingestion of β-casein A1 milk can cause ischemic heart disease, type-1 diabetes, arteriosclerosis, sudden infant death syndrome, autism, schizophrenia, etc. The knowledge of bovine A2 milk and caprine αs2-casein has been utilized to rescue CMPA patients and other potential disease problems. 
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  • 05 May 2021
Topic Review
African Sandalwood (Osyris lanceolata Hochst.)
The increasing demand for ornamental, cosmetic and pharmaceutical products is driving exploitation of plant species globally. Sub-Saharan Africa harbours unique and valuable plant resources and is now a target of plant resource depletion. African Sandalwood (Osyris lanceolata), a multi-purpose and drought-tolerant species, has seen increased exploitation for the last thirty years and is now declared endangered.
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  • 17 Jan 2022
Topic Review
Dilophosauridae
Dilophosauridae is a family of medium to large sized theropod dinosaurs. The name Dilophosauridae is derived from Greek, with “di-” meaning “two,” “lophos” meaning “crest,” “sauros” meaning “lizard,” and “-idae” meaning “family”. While the name suggests that all dilophosaurids have two crests, this is not applicable to all dilophosaurids. The Dilophosauridae is anchored by its type genus, Dilophosaurus, and therefore the name comes from the distinctive two crests of the genus.
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  • 24 Oct 2022
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