Demining or mine clearance is the process of removing land mines from an area. In military operations, the object is to clear a path through a minefield, this is done with devices such as mine plows and blast waves. By contrast, the goal of humanitarian demining is to remove all of the landmines to a given depth and make the land safe for human use. Specially trained dogs are used to narrow down the search and verify that an area is cleared. Mechanical devices such as flails and excavators are sometimes used to clear mines. A great variety of methods for detecting landmines have been studied; these include electromagnetic methods, one of, employed in tandem with metal detectors. Acoustic methods can sense the cavity created by mine casings. Sensors have been developed to detect vapor leaking from landmines. Animals such as rats and mongooses can safely move over a minefield and detect mines, animals can be used to screen air samples over potential minefields. Bees and bacteria are potentially useful.
Explosives in landmines can be detected directly using nuclear quadrupole resonance and neutron probes. Detection and removal of landmines is a dangerous activity, personal protective equipment does not protect against all types of landmine. Once found, mines are defused or blown up with more explosives, but it is possible to destroy them with certain chemicals or extreme heat without making them explode. Land mines overlap with other categories of explosive devices, including unexploded ordnance, booby traps and improvised explosive devices. In particular, most mines are factory-built, but the definition of landmine can include "artisanal" mines. Thus, the United Nations Mine Action Service includes mitigation of IEDs in its mission. Injuries from IEDs are much more serious, but factory-built landmines are longer lasting and more plentiful. Over 1999–2016, yearly casualties from landmines and unexploded ordnance have varied between 9,228 and 3,450. In 2016, 78% of the casualties were suffered by civilians, 20% by military and security personnel and 2% by deminers.
There are two main categories of land mine: anti-personnel. Anti-tank mines are designed to other vehicles, they have a lot of metal and so are easy to detect. Anti-personnel mines are designed to kill soldiers. There are over 350 types. Blast mines are triggered by pressure. A weight between 4 and 24 pounds, the weight of a small child, is enough to set one off, they are cylindrical with a diameter of 2–4 inches and a height of 1.3–3.0 inches. Fragmentation mines are designed to explode outwards, in some cases "bounding" upward and exploding above the ground, resulting in casualties as much as 100 metres away, their size varies and they are metal, so they are detected by metal detectors. However, they are activated by tripwires that can be up to 20 metres away from the mine, so tripwire detection is essential; the casing of blast mines may be made of wood or plastic. Some mines, referred to as minimum metal mines, are constructed with as little metal as possible – as little as 1 gram – to make them difficult to detect.
Common explosives used in land mines include TNT, RDX, pentaerythritol tetranitrate, HMX and ammonium nitrate. Land mines are found in about 60 countries. Deminers must cope with environments that include deserts and urban environments. Antitank mines are buried while antipersonnel mines are within 6 inches of the surface, they may be scattered from airplanes, in regular or irregular patterns. In urban environments, fragments of destroyed buildings may hide them. Detectors can be confused by high-metal soils and junk. Thus, demining presents a considerable engineering challenge. In military demining, the goal is to create a safe path for troops and equipment; the soldiers who carry this out are known as sappers, or pioneers. Sometimes soldiers may bypass a minefield, but some bypasses are designed to concentrate advancing troops into a killing zone. If engineers need to clear a path, they may be under heavy fire and need supporting fire to suppress it and to obscure the site with smoke; some risk of casualties is accepted, but engineers under heavy fire may need to clear an obstacle in 7-10 minutes to avoid excessive casualties, so manual breaching may be too slow.
They may need to operate at night. Good intelligence is needed on factors like the locations of minefields, types of mines and how they were laid, their density and pattern, ground conditions and the size and location of enemy defenses. Humanitarian demining is a component of mine action, a broad effort to reduce the social and environmental damage of mines; the other "pillars" of mine action are risk education, victim assistance, stockpile destruction and advocacy against the use of anti-personnel mines and cluster munitions. It is done for the benefit of civilians, not the military, the aim is to reduce risks for deminers and civilians as much as possible. In some situations, it is a necessary precondition for other humanitarian programs. A national mine action authority is given the primary responsibility for mine action, which it manages through a mine action center. Th
An equator of a rotating spheroid is its zeroth circle of latitude. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles. On Earth, the Equator is 21.3 % over land. Indonesia is the country straddling the greatest length of the equatorial line across both land and sea; the name is derived from medieval Latin word aequator, in the phrase circulus aequator diei et noctis, meaning ‘circle equalizing day and night’, from the Latin word aequare meaning ‘make equal’. The latitude of the Earth's equator is, by definition, 0° of arc; the Equator is one of the five notable circles of latitude on Earth. The Equator is the only line of latitude, a great circle — that is, one whose plane passes through the center of the globe; the plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator.
In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice per year: on the equinoxes in March and September. To a person on Earth, the Sun appears to travel above the Equator at these times. Light rays from the Sun's center are perpendicular to Earth's surface at the point of solar noon on the Equator. Locations on the Equator experience the shortest sunrises and sunsets because the Sun's daily path is nearly perpendicular to the horizon for most of the year; the length of daylight is constant throughout the year. Earth bulges at the Equator. Sites near the Equator, such as the Guiana Space Centre in Kourou, French Guiana, are good locations for spaceports as they have a faster rotational speed than other latitudes. Since Earth rotates eastward, spacecraft must be launched eastward to take advantage of this Earth-boost of speed; the precise location of the Equator is not fixed. This effect must be accounted for in detailed geophysical measurements; the International Association of Geodesy and the International Astronomical Union have chosen to use an equatorial radius of 6,378.1366 kilometres.
This equatorial radius is in the 2003 and 2010 IERS Conventions. It is the equatorial radius used for the IERS 2003 ellipsoid. If it were circular, the length of the Equator would be 2π times the radius, namely 40,075.0142 kilometres. The GRS 80 as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of 6,378.137 kilometres. The WGS 84, a standard for use in cartography and satellite navigation including GPS has an equatorial radius of 6,378.137 kilometres. For both GRS 80 and WGS 84, this results in a length for the Equator of 40,075.0167 km. The geographical mile is defined as one arc-minute of the Equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is 1,855.3248 metres, while by IAU-2000, it is 1,855.3257 metres. This is a difference of less than one millimetre over the total distance; the earth is modeled as a sphere flattened 0.336% along its axis. This makes the Equator 0.16% longer than a meridian.
The IUGG standard meridian is, to the nearest millimetre, 40,007.862917 kilometres, one arc-minute of, 1,852.216 metres, explaining the SI standardization of the nautical mile as 1,852 metres, more than 3 metres less than the geographical mile. The sea-level surface of the Earth is irregular, so the actual length of the Equator is not so easy to determine. Aviation Week and Space Technology on 9 October 1961 reported that measurements using the Transit IV-A satellite had shown the equatorial "diameter" from longitude 11° West to 169° East to be 1,000 feet greater than its "diameter" ninety degrees away; the Equator passes through the land of 11 countries. Starting at the Prime Meridian and heading eastwards, the Equator passes through: Despite its name, no part of Equatorial Guinea lies on the Equator. However, its island of Annobón is 155 km south of the Equator, the rest of the country lies to the north. Seasons result from the tilt of the Earth's axis compared to the plane of its revolution around the Sun.
Throughout the year the northern and southern hemispheres are alternately turned either toward or away from the sun depending on Earth's position in its orbit. The hemisphere turned toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter. At the equinoxes, the Earth's axis
Vietnamese cuisine encompasses the foods and beverages of Vietnam, features a combination of five fundamental tastes in the overall meal. Each Vietnamese dish has a distinctive flavor. Common ingredients include fish sauce, shrimp paste, soy sauce, bean sauce, fresh herbs and vegetables. Vietnamese recipes use lemongrass, mint, Vietnamese mint, long coriander, Saigon cinnamon, bird's eye chili and Thai basil leaves. Traditional Vietnamese cooking is admired for its fresh ingredients, minimal use of dairy and oil, complementary textures, reliance on herbs and vegetables. With the balance between fresh herbs and meats and a selective use of spices to reach a fine taste, Vietnamese food is considered one of the healthiest cuisines worldwide. Due to the Chinese domination of Vietnam, Vietnamese cuisine is influenced by traditional Chinese medicine; as the people respect balance rules, Vietnamese cuisine always combines fragrance and colour. Vietnamese cuisine always has five elements which are known for its balance in each of these features.
Many Vietnamese dishes include five fundamental taste senses: spicy, bitter and sweet, corresponding to five organs: gall bladder, small intestine, large intestine and urinary bladder. Vietnamese dishes include five types of nutrients: powder, water or liquid, mineral elements and fat. Vietnamese cooks try to have five colours: white, yellow and black in their dishes. Dishes in Vietnam appeal to gastronomes via the five senses: food arrangement attracts eyes, sounds come from crisp ingredients, five spices are detected on the tongue, aromatic ingredients coming from herbs stimulate the nose, some meals finger food, can be perceived by touching. Whether complex or simple, Vietnamese dishes offer satisfying mouthfeel during the dining enjoyment. Vietnamese cuisine is influenced by the Asian principle of Mahābhūta; the principle of yin and yang is applied in composing a meal in a way that provides a balance, beneficial for the body. While contrasting texture and flavors are important, the principle concerns the "heating" and "cooling" properties of ingredients.
Certain dishes are served in their respective seasons to provide contrasts in temperature and spiciness of the food and environment. Some examples are: Duck meat, considered "cool", is served during the hot summer with ginger fish sauce, "warm". Conversely, "warm", pork, "hot", are eaten in the winter. Seafoods ranging from "cool" to "cold" are suitable to use with ginger. Spicy foods are balanced with sourness, considered "cool". Balut, meaning "upside-down egg", must be combined with Vietnamese mint. Salt is used as the connection between the worlds of the dead. Bánh phu thê is used to remind new couples of harmony at their weddings. Food is placed at the ancestral altar as an offering to the dead on special occasions. Cooking and eating play an important role in Vietnamese culture; the word ăn has a large range of semantic extensions. The mainstream culinary traditions in all three regions of Vietnam share some fundamental features: Freshness of food: Most meats are only cooked. Vegetables are eaten fresh.
Presence of herbs and vegetables: Herbs and vegetables are essential to many Vietnamese dishes and are abundantly used. Variety and harmony of textures: Crisp with soft, watery with crunchy, delicate with rough. Broths or soup-based dishes are common in all three regions. Presentation: The condiments accompanying Vietnamese meals are colorful and arranged in eye-pleasing manners. While sharing some key features, Vietnamese culinary tradition differs from region to region. In northern Vietnam, a colder climate limits the availability of spices; as a result, the foods there are less spicy than those in other regions. Black pepper is used in place of chilis as the most popular ingredient to produce spicy flavors. In general, northern Vietnamese cuisine is not bold in any particular taste — sweet, spicy, bitter, or sour. Most northern Vietnamese foods feature light and balanced flavors that result from subtle combinations of many different flavoring ingredients; the use of meats such as pork and chicken were limited in the past.
Freshwater fish and mollusks, such as prawns, shrimps, crabs and mussels, are used. Many notable dishes of northern Vietnam are crab-centered. Fish sauce, soy sauce, prawn sauce, limes are among the main flavoring ingredients. Being the cradle of Vietnamese civilization, northern Vietnam produces many signature dishes of Vietnam, such as bún riêu and bánh cuốn, which were carried to central and southern Vietnam through Vietnamese migration. Other famous Vietnamese dishes that originated from the North from Hanoi include "bún chả", phở gà, chả cá Lã Vọng; the abundance of spices produced by central Vietnam’s mountainous terrain makes this region’s cuisine notable for its spicy food, which sets it apart from the two other regions of Vietnam where foods are not spicy. Once the capital of the last dynasty of Vietnam, Huế's culinary tradition features decorative and
Pruning is a horticultural and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, improving or sustaining health, reducing risk from falling branches, preparing nursery specimens for transplanting, both harvesting and increasing the yield or quality of flowers and fruits; the practice entails targeted removal of diseased, dead, non-productive, structurally unsound, or otherwise unwanted tissue from crop and landscape plants. In general, the smaller the branch, cut, the easier it is for a woody plant to compartmentalize the wound and thus limit the potential for pathogen intrusion and decay, it is therefore preferable to make any necessary formative structural pruning cuts to young plants, rather than removing large, poorly placed branches from mature plants. Specialized pruning practices may be applied to certain plants, such as roses, fruit trees, grapevines, it is important when pruning that the tree’s limbs are kept intact, as this is what helps the tree stay upright.
Different pruning techniques may be deployed on herbaceous plants than those used on perennial woody plants. Hedges, by design, are maintained by hedge trimming, rather than by pruning. In nature, meteorological conditions such as wind and snow, salinity can cause plants to self-prune; this natural shedding is called abscission. For arboricultural purposes the unions of tree branches are placed in one of three types: collared, collarless or codominant. Regardless of the overall type of pruning being carried out, each type of union is cut in a particular way so that the branch has less chance of regrowth from the cut area and best chance of sealing over and compartmentalising decay; this is referred to by arborists as "target cutting". Branches die off for a number of reasons including light deficiency and disease damage, root structure damage. A dead branch will at some point decay back to the parent fall off; this is a slow process but can be quickened by high winds or extreme temperature. The main reason deadwooding is performed is safety.
Situations that demand removal of deadwood is trees that overhang public roads, public areas and gardens. Trees located in wooded areas are assessed as lower risk but assessments consider the number of visitors. Trees adjacent to footpaths and access roads are considered for deadwood removal. Another reason for deadwooding is amenity value, i.e. a tree with a large amount of deadwood throughout the crown looks more aesthetically pleasing with the deadwood removed. The physical practice of deadwooding can be carried out most of the year though not when the tree is coming into leaf; the deadwooding process speeds up the tree's natural abscission process. It reduces unwanted weight and wind resistance and can help overall balance. Crown and canopy thinning increases light and reduces wind resistance by selective removal of branches throughout the canopy of the tree. Crown lifting involves the removal of the lower branches to a given height; the height is achieved by the removal of whole branches or removing the parts of branches which extend below the desired height.
The branches are not lifted to more than one third of the tree's total height. Crown lifting is done for access. Lifting the crown will allow traffic and pedestrians to pass underneath safely; this pruning technique is used in the urban environment as it is for public safety and aesthetics rather than tree form and timber value. Crown lifting introduces light to the lower part of the trunk. To reduce this sometimes smaller branches are left on the lower part of the trunk. Excessive removal of the lower branches can displace the canopy weight, this will make the tree top heavy, therefore adding stress to the tree; when a branch is removed from the trunk, it creates a large wound. This wound is susceptible to disease and decay, could lead to reduced trunk stability. Therefore, much time and consideration must be taken when choosing the height the crown is to be lifted to; this would be an inappropriate operation. This would therefore remove most of the foliage and would largely unbalance the tree; this procedure should not be carried out if the tree is in decline, poor health or dead, dying or dangerous as the operation will remove some of the photosynthetic area the tree uses.
This could lead to death. If the tree is of great importance to an area or town an alternative solution to crown lifting would be to move the target or object so it is not in range. For example, diverting a footpath around a tree’s drip line so the crown lift is not needed. Another solution would be to cable-brace the low hanging branch; this is a non-invasive solution which in some situations can work out more economically and environmentally friendly. Removal of appropriate branches to make the tree structurally sound while shaping it. Selectively pruning a window of view in a tree. Reducing the height and or spread of a tree by selectively cutting back to smaller branches and in fruit trees for increasing of light interception and enhancing fruit quality. A regular form of pruning where certain deciduous species are pruned back to pollard heads every year in the dormant period; this practice is commenced on juvenile trees so they can adapt to the harshness of the practice. Arborists, orchardists, an
A land mine is an explosive device concealed under or on the ground and designed to destroy or disable enemy targets, ranging from combatants to vehicles and tanks, as they pass over or near it. Such a device is detonated automatically by way of pressure when a target steps on it or drives over it, although other detonation mechanisms are sometimes used. A land mine may cause damage by direct blast effect, by fragments that are thrown by the blast, or by both; the name originates from the ancient practice of military mining, where tunnels were dug under enemy fortifications or troop formations. These killing tunnels were at first collapsed to destroy targets located above, but they were filled with explosives and detonated in order to cause greater devastation. Nowadays, in common parlance, "land mine" refers to devices manufactured as anti-personnel or anti-vehicle weapons. Though some types of improvised explosive devices are mistakenly classified as land mines, the term land mine is reserved for manufactured devices designed to be used by recognized military services, whereas IED is used for makeshift "devices placed or fabricated in an improvised manner incorporating explosive material, lethal, incendiary, pyrotechnic materials or chemicals designed to destroy, distract or harass.
They may incorporate military stores, but are devised from non-military components". The use of land mines is controversial because of their potential as indiscriminate weapons, they can remain dangerous many years after a conflict has ended, harming the economy. 78 countries are contaminated with land mines and 15,000–20,000 people are killed every year while countless more are maimed. 80% of land mine casualties are civilian, with children as the most affected age group. Most killings occur in times of peace. With pressure from a number of campaign groups organised through the International Campaign to Ban Landmines, a global movement to prohibit their use led to the 1997 Convention on the Prohibition of the Use, Stockpiling and Transfer of Anti-Personnel Mines and on their Destruction known as the Ottawa Treaty. To date, 164 nations have signed the treaty. Land mines were designed for two main uses: To create defensive tactical barriers, channelling attacking forces into predetermined fire zones or slowing an invading force's progress to allow reinforcements to arrive.
To act as passive area-denial weapons. Land mines are used in large quantities for this first purpose, thus their widespread use in the demilitarized zones of flashpoints such as Cyprus and Korea; as of 2013, the only governments that still laid land mines were Myanmar in its internal conflict, Syria in its civil war. Land mines continue to kill or injure at least 4,300 people every year decades after the ends of the conflicts for which they were placed. Jiao Yu in the preface to his Huolongjing Quanzhi, written in 1412 AD, claimed that in the third century, the chancellor Zhuge Liang of the Shu Han state had used not only "fire weapons" but land mines in the Battle of Hulugu Valley against the forces of Sima Yi and his son Sima Zhao of the rival Cao Wei state; this claim is dubious, as gunpowder warfare did not develop in China until the advent of the flamethrower in the 10th century, while the land mine was not seen in China until the late 13th century. Explosive land mines were used in 1277 by the Chinese during the Song dynasty against an assault of the Mongols, who were besieging a city in southern China.
The invention of this detonated "enormous bomb" was credited to one Lou Qianxia of the 13th century. The famous 14th-century Chinese text of the Huolongjing, the first to describe hollow cast iron cannonball shells filled with gunpowder, was the first to describe the invention of the land mine in greater detail than references found in texts written beforehand; this mid 14th century work compiled during the late Yuan dynasty and early Ming dynasty stated that mines were made of cast iron and were spherical in shape, filled with either "magic gunpowder", "poison gunpowder", or "blinding and burning gunpowder", any one of these compositions being suitable for use. The wad of the mine was made of hard wood, carrying three different fuses in case of defective connection to the touch hole. In those days, the Chinese relied upon command signals and timed calculation of enemy movements into the minefield, since a long fuse had to be ignited by hand from the ambushers in a somewhat far-off location lying in wait.
The Huolongjing describes land mines that were set off by enemy movement, called the'ground-thunder explosive camp', one of the'self-trespassing' types, as the text says: These mines are installed at frontier gates and passes. Pieces of bamboo are sawn into sections nine feet in length, all septa in the bamboo being removed, save only the last. Boiling oil is next left there for some time before being removed; the fuse starts from the bottom, is compressed into it to form an explosive mine. The gunpowder fills up eight-tenths of the tube, while lead or iron pellets take up the rest of the space. A trench five feet in depth is dug; the fuse is connected to a firing device. The Huolongjing describes the trigger device used for this as a "steel wheel", which directed sparks
Geography of Vietnam
Vietnam is located on the eastern margin of the Indochinese peninsula and occupies about 331,211.6 square kilometers, of which about 25% was under cultivation in 1987. It borders the Gulf of Thailand, Gulf of Tonkin, Pacific Ocean, along with China and Cambodia; the S-shaped country has a north-to-south distance of 1,650 km and is about 50 km wide at the narrowest point. With a coastline of 3,260 km, excluding islands, Vietnam claims 12 nautical miles as the limit of its territorial waters, an additional 12 nautical miles as a contiguous customs and security zone, 200 nautical miles as an exclusive economic zone; the boundary with Laos, was settled on both an ethnic and geographical basis, between the rulers of Vietnam and Laos in the mid-seventeenth century. The Annamite Range as a reference, was formally defined by a delimitation treaty signed in 1977 and ratified in 1986; the frontier with Cambodia, defined at the time of French annexation of the western part of the Mekong Delta in 1867, remained unchanged, according to Hanoi, until some unresolved border issues were settled in the 1982-85 period.
The land and sea boundary with China, delineated under the France-China treaties of 1887 and 1895, is "the frontier line" accepted by Hanoi. China agreed in 1957-58 to respect that border line. However, in February 1979, following the Sino-Vietnamese War, Hanoi complained that from 1957 onward China had provoked numerous border incidents as part of its anti-Vietnam policy and expansionist designs in Southeast Asia. Among the territorial infringements cited was the Chinese occupation in January 1974 of the Paracel Islands, claimed by both countries in a dispute left unresolved in the 1980s; the country is divided into the Red River Delta in the north. Vietnam is a country of tropical lowlands and densely forested highlands, with level land covering no more than 20% of the area; the spectacular Bản Giốc Waterfall is 272 km north of Hanoi and few tourists are seen there. The Red River Delta, is a flat, triangular region of 15,000 square kilometers, is smaller but more intensely developed and more densely populated than the Mekong Delta.
Once an inlet of the Gulf of Tonkin, it has been filled in by the enormous alluvial deposits of the rivers over a period of millennia, it advances one hundred meters into the Gulf annually. The ancestral home of the ethnic Vietnamese, the delta accounted for 70% of the agriculture and 80% of the industry of North Vietnam before 1975; the Red River, rising in China's Yunnan Province, is about 1,200 kilometers long. Its two main tributaries, the Sông Lô and the Sông Đà, contribute to its high water volume, which averages 4,300 cubic meters per second; the entire delta region, backed by the steep rises of the forested highlands, is no more than three meters above sea level, much of it is one meter or less. The area is subject to frequent flooding. For centuries flood control has been an integral part of the delta's economy. An extensive system of dikes and canals has been built to contain the Red River and to irrigate the rich rice-growing delta. Modeled on that of China's, this ancient system has sustained a concentrated population and has made double-cropping wet-rice cultivation possible throughout about half the region.
The highlands and mountain plateaus in the north and northwest are inhabited by tribal minority groups. The Dãy Trường Sơn originates in the Tibetan and Yunnan regions of southwest China and forms Vietnam's border with Laos, it terminates in the Mekong River Delta north of Hồ Chí Minh City. These central mountains, which have several high plateaus, are irregular in form; the northern section is narrow and rugged. The southern portion has numerous spurs that divide the narrow coastal strip into a series of compartments. For centuries these topographical features not only rendered north-south communication difficult but formed an effective natural barrier for the containment of the people living in the Mekong basin. Within the southern portion of Vietnam is a plateau known as the Central Highlands 51,800 square kilometers of rugged mountain peaks, extensive forests, rich soil. Comprising 5 flat plateaus of basalt soil spread over the provinces of Đắk Lắk, Gia Lai, Kon Tum, the highlands account for 16% of the country's arable land and 22% of its total forested land.
Before 1975, North Vietnam had maintained that the Central Highlands and the Giai Truong Son were strategic areas of paramount importance, essential to the domination not only of South Vietnam but of the southern part of Indochina. Since 1975, the highlands have provided an area in which to relocate people from the densely populated lowlands; the narrow, flat coastal lowlands extend from south of the Red River Delta to the Mekong River basin. On the landward side, the Dãy Trường Sơn rises precipitously above the coast, its spurs jutting into the sea at several places; the coastal strip is fertile and rice is cultivated intensively. The Mekong Delta, covering about 40,000 square kilometers, is a low-level plain not more than three meters above sea level at any point a