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Concertina Wire
Concertina wire or Dannert wire is a type of barbed wire or razor wire that is formed in large coils which can be expanded like a concertina. In conjunction with plain barbed wire (and/or razor wire/tape) and steel pickets, it is most often used to form military-style wire obstacles. It is also used in non-military settings, such as when used in prison barriers, detention camps, riot control, or at international borders. During World War I, soldiers manufactured concertina wire themselves, using ordinary barbed wire. Today, it is factory made. Origins In World War I, barbed wire obstacles were made by stretching lengths of barbed wire between stakes of wood or iron. At its simplest, such a barrier would resemble a fence as might be used for agricultural purposes. The double apron fence comprised a line of pickets with wires running diagonally down to points on the ground either side of the fence. Horizontal wires were attached to these diagonals. More elaborate an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Razor Wire
Barbed tape or razor wire is a mesh of metal strips with sharp edges whose purpose is to prevent trespassing by humans or to secure facilities such as prisons where there is a risk of escape. The term "razor wire", through long usage, has generally been used to describe barbed tape products. Razor wire is much sharper than the standard barbed wire; it is named after its appearance but is not razor sharp. The points are very sharp and made to rip and snag clothing and flesh. The multiple blades of a razor-wire fence are designed to inflict serious cuts on anyone attempting to climb through or over it, which simultaneously gives it a strong psychological deterrent effect. Although it can be circumvented relatively quickly by humans with tools ( Bolt cutters being a prominent example). Attempting to get through razor wire without tools is incredibly hazardous and requires a substantial amount of time; thwarting such attempts or giving corresponding security forces more time to res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fortification (obstacles)
A fortification (also called a fort, fortress, fastness, or stronghold) is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Latin ("strong") and ("to make"). From very early history to modern times, defensive walls have often been necessary for cities to survive in an ever-changing world of invasion and conquest. Some settlements in the Indus Valley Civilization were the first small cities to be fortified. In ancient Greece, large cyclopean stone walls fitted without mortar had been built in Mycenaean Greece, such as the ancient site of Mycenae. A Greek '' phrourion'' was a fortified collection of buildings used as a military garrison, and is the equivalent of the Roman castellum or fortress. These constructions mainly served the purpose of a watch tower, to guard certain roads, passes, and borders. Though smaller than a real fortress, they acted as a border ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engineering Barrages
Engineering is the practice of using natural science, mathematics, and the engineering design process to solve problems within technology, increase efficiency and productivity, and improve systems. Modern engineering comprises many subfields which include designing and improving infrastructure, machinery, vehicles, electronics, materials, and energy systems. The discipline of engineering encompasses a broad range of more specialized fields of engineering, each with a more specific emphasis for applications of mathematics and science. See glossary of engineering. The word ''engineering'' is derived from the Latin . Definition The American Engineers' Council for Professional Development (the predecessor of the Accreditation Board for Engineering and Technology aka ABET) has defined "engineering" as: History Engineering has existed since ancient times, when humans devised inventions such as the wedge, lever, wheel and pulley, etc. The term ''engineering'' is derived f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slinky
The Slinky is a helical spring toy invented and developed by American naval engineer Richard T. James in 1943 and successfully demonstrated at Gimbels department store in Philadelphia on November 27, 1945. It can perform a number of tricks, including travelling down a flight of steps end-over-end as it stretches and re-forms itself with the aid of gravity and its own momentum; and appearing to levitate for a period of time after it has been dropped. These interesting characteristics have contributed to its success in its home country of the United States, and it has inspired many popular toys with Slinky-like components, in a wide range of countries. History Creation In 1943, Richard T. James, a naval mechanical engineer, observed a spring "stepping" downward after being knocked off a shelf, then coming to rest in a vertical position. James's wife Betty later recalled, "He came home and said, 'I think if I got the right property of steel and the right tension, I could ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helix
A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word ''helix'' comes from the Greek word , "twisted, curved". A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called a '' helicoid''. Properties and types The pitch of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two (typically congruent) helices with the same axis, differing by a translation along the axis. A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion. The slope of a circular helix is commonly defined as the ratio of the circumference of the circular cylinder that it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emperor Constantine
Constantine I (27 February 27222 May 337), also known as Constantine the Great, was a Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople (modern-day Istanbul) and made it the capital of the Empire, which it remained for over a millennium. Born in Naissus, a city located in the province of Moesia Superior (now Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman army officer from Moesia Superior, who would become one of the four emperors of the Tetrarchy. His mother, Helena, was a woman of low birth, probably from Bithynia. Later canonised as a saint, she is credited for the conversion of her son in some traditions, though others believe that Constantine conve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Screw Picket
A screw picket is a metal device which is used to secure objects to the ground. Today, screw pickets are used widely to temporarily "picket" dogs. They are also used to graze animals such as sheep, goats, and horses. Screw pickets are also used to stabilize small trees, tent poles, and other objects that are intended to remain upright. The original picket was a stake hammered into the ground to secure a horse by tying it to the stake. This required a second tool (a hammer) or the availability of a rock to use instead of a tool. The screw picket is screwed (by turning it) into the ground. In hard ground, it requires a second tool (a leverage bar, or a spare screw picket) or the availability of a length of wood. Screw pickets can be easily bent or broken, but less easily pulled from the ground. Military non-equestrian use Screw pickets (used as supports for barbed wire defences) were introduced c. 1915 as a replacement for timber posts. Crown Iron Works Co. (Minneapolis, MN) mad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Anti-invasion Preparations Of World War II
British anti-invasion preparations of the Second World War entailed a large-scale division of military and civilian mobilisation in response to the threat of invasion (Operation Sea Lion) by German armed forces in 1940 and 1941. The British Army needed to recover from the defeat of the British Expeditionary Force in France, and 1.5 million men were enrolled as part-time soldiers in the Home Guard. The rapid construction of field fortifications transformed much of the United Kingdom, especially southern England, into a prepared battlefield. Sea Lion was never taken beyond the preliminary assembly of forces. Today, little remains of Britain's anti-invasion preparations, although reinforced concrete structures such as pillboxes and anti-tank cubes can still be commonly found, particularly in the coastal counties. Political and military background On 1 September 1939, Germany invaded Poland; two days later, Britain and France declared war on Germany, launching the Second Wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platoon
A platoon is a Military organization, military unit typically composed of two to four squads, Section (military unit), sections, or patrols. Platoon organization varies depending on the country and the Military branch, branch, but a platoon can be composed of 20–50 troops, although specific platoons may range from 10 to 100 people. A platoon is typically the smallest military unit led by a Officer (armed forces), commissioned officer. The platoon leader is usually a junior officer—a Second lieutenant, second or first lieutenant or an equivalent rank. The officer is usually assisted by a platoon sergeant. Rifle platoons normally consist of a small platoon headquarters and three or four sections (Commonwealth) or squads (United States). In some armies, platoon is used throughout the branches of the army. In a few armies, such as the French Army, a platoon is specifically a cavalry unit, and the infantry use "section" as the equivalent unit. A unit consisting of several platoon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trench Warfare
Trench warfare is a type of land warfare using occupied lines largely comprising Trench#Military engineering, military trenches, in which combatants are well-protected from the enemy's small arms fire and are substantially sheltered from artillery. It became archetypically associated with World War I (1914–1918), when the Race to the Sea rapidly expanded trench use on the Western Front (World War I), Western Front starting in September 1914.. Trench warfare proliferated when a Weapons of World War I, revolution in firepower was not matched by similar advances in mobility (military), mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout (shelter), dugout systems opposing each other along a front (military), front, protected from assault by barbed wire. The area between opposing trench lines (known as "no man's land") was fully exposed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
