Avalanche control or avalanche defense activities reduce the hazard avalanches pose to human life and property. Avalanche control begins with a risk assessment conducted by surveying for potential avalanche terrain by identifying geographic features such as vegetation patterns and seasonal snow distribution that are indicative of avalanches. From the identified avalanche risks, the hazard is assessed by identifying threatened human geographic features such as roads, ski-hills, buildings. Avalanche control programs address the avalanche hazard by formulating prevention and mitigation plans, which are executed during the winter season; the prevention and mitigation plans combine extensive snow pack observation with three major groups of interventions: active and social - sometimes more narrowly defined as "explosive", "structural", "awareness" according to the most prevalent technique used in each. Avalanche control techniques either directly intervene in the evolution of the snow pack, or lessen the effect of an avalanche once it has occurred.
For the event of human involvement, avalanche control organizations develop and train exhaustive response and recovery plans. Risk assessment for geographical surveys for potential avalanche terrain by studying topography and seasonal snow distribution. Hazard assessment geographical surveys for the consequences of avalanche by studying exposure of urbanization, industrialization, recreational activities, the distribution of human use of the potential avalanche terrain identified in the risk assessment. Prevention and mitigation begins with observing the snow pack to forecast the risk of avalanche occurrence; the forecast risk determines the necessary interventions to reduce the hazard posed by an avalanche. Snow pack observation studies the layering and distribution of the snow to estimate the instabilities of the snow pack and thus the risk of an avalanche occurring in a particular terrain feature. In areas of heavy human use the snow pack is monitored throughout the winter season to assess its evolution under the prevailing meteorological conditions.
In contrast to used avalanche terrain where forecasting is the goal of snow observation, in remote terrain, or terrain, infrequently visited, snow pack observation elucidates the immediate instabilities of the snow pack. Active techniques reduce the risk of an avalanche occurring by promoting the stabilization and settlement of the snow pack through three forms of intervention: disrupting weak layers in the snow pack, increasing the uniformity of the snow pack, lessening the amount of snow available in snow pack for entrainment in an avalanche. Active avalanche control can be broadly classified into either explosive methods. Mechanical methods are used in either remote terrain, smaller terrain, or less hazardous terrain. In the smallest terrain features the simplest method of avalanche control is a mechanical intervention that disrupts weak snow layers by directly walking through them, a technique referred to as boot packing. For larger features this method can be extended by mechanized redistribution of snow using large tracked vehicles called snow groomers.
These two mechanical interventions can only be safely done as the snow is deposited and before it develops any instabilities. In terrain that can only be sporadically accessed, or in a developed snow pack, too deep for boot packing, ski stabilization techniques are used; the first technique of ski stabilizing is a method of entering a slope called ski cutting. In this method a skier attempts to trigger a small avalanche by breaking the tensile support of the upper snow pack through a quick traverse along the top of the slope, the skier can be belayed on a rope to further protect them from being caught in an avalanche. A snow pack can be further settled out, or stabilized, by further down slope ski traffic through it. Knotted cord can be used to saw through the roots of cornices, causing the cornice to drop onto the snow pack of the slope below; this has the combined effect of reducing the objective hazard posed by the cornice, providing a large impact force on the snow pack. Explosive techniques involve the artificial triggering of smaller less destructive avalanches, by detonating charges either above or on the snow surface.
The explosives may be deployed by manually hand tossing and lowering, by bombing from a helicopter, or by shelling with a small howitzer, recoilless rifle, or air gun. In balancing the hazard to personnel with the effectiveness of the deployment method at accessing and triggering avalanche terrain, each method has its drawbacks and advantages. Among the newest methods, strategically placed remote controlled installations that generate an air blast by detonating a fuel-air explosive above the snow pack in an avalanche starting zone, offer fast and effective response to avalanche control decisions while minimizing the risk to avalanche control personnel. For example, the Avalanche Towers installed in Switzerland and Norway use solar powered launchers to deploy charges from a magazine containing 12 radio controlled charges; the magazines can be transported and removed from the towers by helicopter, without the need for a flight assistant, or on site personnel. Explosive control has proved to be effective in areas with easy access to avalanche star
A snow shed, snow bridge or avalanche gallery is a type of rigid snow-supporting structure for avalanche control or to maintain passage in areas where snow removal becomes impossible. They can be made of prestressed concrete frames, or timber; these structures can be enclosed, like an artificial tunnel, or consist of lattice-like elements. They are of robust construction considering the environments they must survive in. Snow protection is important when routes cross avalanche "chutes", which are natural ravines or other formations that direct or concentrate avalanches. Snow sheds or avalanche galleries are a common sight on railroads in mountain areas, such as the Donner Pass in the United States or many of the Swiss mountain railways, where tracks are covered with miles of shedding. Although unused today, the Central Pacific railroad had a complete rail yard under roof in the pass, they are found on hazardous stretches of roadway as well. The Trans-Canada Highway between Revelstoke and Golden in British Columbia has several snow sheds covering both carriageways to cope with the heavy snow.
East of Snoqualmie Pass in Washington in the northwest U. S. westbound. The 500-foot concrete structure covered two lanes on a curve and was constructed in 1950 for U. S. Route 10 one lane in each direction. Snow bridges may superficially look similar to snow fences. Snow fences are built vertically and accumulate snow on their downwind side, while snow bridges are slanted or horizontal and hold snow on their top side. Snow bridges are fastened to the slope on the upslope side by tension anchors and on the downslope by compression anchors. Avalanche dam Avalanche net List of wind-related railway accidents The dictionary definition of snow shed at Wiktionary
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers. Turbulence is observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason turbulence is realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other drag due to friction effects increases; this increases the energy needed to pump fluid through a pipe. Turbulence can be exploited, for example, by devices such as aerodynamic spoilers on aircraft that "spoil" the laminar flow to increase drag and reduce lift.
The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, the interactions within turbulence create a complex phenomenon. Richard Feynman has described turbulence as the most important unsolved problem in classical physics. Smoke rising from a cigarette. For the first few centimeters, the smoke is laminar; the smoke plume becomes turbulent as its Reynolds number increases with increases in flow velocity and characteristic lengthscale. Flow over a golf ball. If the golf ball were smooth, the boundary layer flow over the front of the sphere would be laminar at typical conditions. However, the boundary layer would separate early, as the pressure gradient switched from favorable to unfavorable, creating a large region of low pressure behind the ball that creates high form drag. To prevent this, the surface is dimpled to promote turbulence; this results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag.
Clear-air turbulence experienced during airplane flight, as well as poor astronomical seeing. Most of the terrestrial atmospheric circulation; the oceanic and atmospheric mixed intense oceanic currents. The flow conditions in many industrial equipment and machines; the external flow over all kinds of vehicles such as cars, airplanes and submarines. The motions of matter in stellar atmospheres. A jet exhausting from a nozzle into a quiescent fluid; as the flow emerges into this external fluid, shear layers originating at the lips of the nozzle are created. These layers separate the fast moving jet from the external fluid, at a certain critical Reynolds number they become unstable and break down to turbulence. Biologically generated. Snow fences work by inducing turbulence in the wind, forcing it to drop much of its snow load near the fence. Bridge supports in water. In the late summer and fall, when river flow is slow, water flows smoothly around the support legs. In the spring, when the flow is faster, a higher Reynolds number is associated with the flow.
The flow may start off laminar but is separated from the leg and becomes turbulent. In many geophysical flows, the flow turbulence is dominated by the coherent structures and turbulent events. A turbulent event is a series of turbulent fluctuations that contain more energy than the average flow turbulence; the turbulent events are associated with coherent flow structures such as eddies and turbulent bursting, they play a critical role in terms of sediment scour and transport in rivers as well as contaminant mixing and dispersion in rivers and estuaries, in the atmosphere. In the medical field of cardiology, a stethoscope is used to detect heart sounds and bruits, which are due to turbulent blood flow. In normal individuals, heart sounds are a product of turbulent flow as heart valves close. However, in some conditions turbulent flow can be audible due to other reasons, some of them pathological. For example, in advanced atherosclerosis, bruits can be heard in some vessels that have been narrowed by the disease process.
Turbulence in porous media became a debated subject. Turbulence is characterized by the following features: Irregularity Turbulent flows are always irregular. For this reason, turbulence problems are treated statistically rather than deterministically. Turbulent flow is chaotic. However, not all chaotic flows are turbulent. Diffusivity The available supply of energy in turbulent flows tends to accelerate the homogenization of fluid mixtures; the characteristic, responsible for the enhanced mixing and increased rates of mass and energy transports in a flow is called "diffusivity". Turbulent diffusion is described by a turbulent diffusion coefficient; this turbulent diffusion coefficient is defined in a phenomenological sense, by analogy with the molecular diffusivities, but it does not have a true physical meaning, being dependent on the flow conditions, not a property of the fluid itself. In addition, the turbulent diffusivity concept assumes a con
University of Nebraska–Lincoln
The University of Nebraska–Lincoln referred to as Nebraska, UNL or NU, is a public research university in the city of Lincoln, in the state of Nebraska in the Midwestern United States. It is the state's oldest university, the largest in the University of Nebraska system; the state legislature chartered the university in 1869 as a land-grant university under the 1862 Morrill Act, two years after Nebraska's statehood into the United States. Around the turn of the 20th century, the university began to expand hiring professors from eastern schools to teach in the newly organized professional colleges while producing groundbreaking research in agricultural sciences; the "Nebraska method" of ecological study developed here during this time pioneered grassland ecology and laid the foundation for research in theoretical ecology for the rest of the 20th century. The university is organized into eight colleges on two campuses in Lincoln with over 100 classroom buildings and research facilities, its athletic program, called the Cornhuskers, is a member of the Big Ten Conference.
The Nebraska football team has won 46 conference championships since 1970 and five national championships. The women's volleyball team has won five national championships along with nine other appearances in the Final Four; the Husker football team plays its home games at Memorial Stadium, selling out every game since 1962. The stadium's capacity is about 92,000 people, larger than the population of Nebraska's third-largest city; the University of Nebraska was created by an act of the Nebraska state legislature in 1869, two years after the State of Nebraska was admitted into the U. S; the law passed in 1869 creating the university described its aims: "The object of such institution shall be to afford to the inhabitants of the state the means of acquiring a thorough knowledge of the various branches of literature and the arts." The school received an initial land grant of about 130,000 acres and the campus construction began with the building of University Hall in its first year. By 1873, the University of Nebraska had offered its first two degrees to its first graduating class.
The school remained small and suffered from a lack of funds until about 20 years after its founding, when its high school programs were taken over by a new state education system. From 1890 to 1895 enrollment rose from 384 to about 1,500. A law school and a graduate school were created at about this time period, making it the first school west of the Mississippi to establish a graduate school. By 1897, the school was 15th in the nation in total enrollment. Through the turn of the 20th century, the school struggled to find an identity as both a pragmatic, frontier establishment and an academic, intellectual institution, it developed a competitive spirit in the form of a debate team, a football team, the arrival of fraternities and sororities. In 1913–14, a fierce debate ensued over whether to keep the University in downtown Lincoln or to move it out of town; the issue was not resolved until a statewide referendum sided with the downtown plan. After purchasing property downtown, the school experienced a building boom, both on the new property and on the farming campus.
The school would not experience another boom until the late 1940s, when the sudden arrival of thousands of soldiers returning from the war for an education forced the school to seek further expansion. In 1908, Nebraska was inducted as a member of the Association of American Universities, an organization of research universities. In recent years, Nebraska had been at or near the bottom of the AAU's statistical criteria for members, a ranking attributed in part to the university's extensive agricultural research funded by the U. S. Department of Agriculture, not included in the AAU's rankings because it is not awarded by peer-reviewed grants. Nebraska retained its AAU membership after a 2000 challenge; this provided Nebraska with an advantage when the Big Ten was looking to expand in 2010, as all of its members at that time were AAU members. Nebraska Chancellor Harvey Perlman said. "I doubt that our application would've been accepted had we not been a member of the." However, in 2011, after an extended campaign to retain its membership and a close, contentious vote, Nebraska became the only institution to be removed from the AAU membership by a vote of the membership In June 2018, the American Association of University Professors voted to censure the university for violations of academic freedom.
In 2017, an adjunct instructor was filmed by a student as the instructor expressed a political opinion about the student's activist activities. State lawmakers demanded that the university hold the instructor accountable and the university subsequently fired her, a move the AAUP contends was a violation of her academic freedom. University of Nebraska is governed by the Board of Regents; the board consists of eight voting members elected by district for six-year terms, four non-voting student Regents, one from each campus, who serve during their tenure as student body president. The board supervises the general operations of the university, the control and direction of all expenditures; the university today has nine colleges which offers more than 150 undergraduate majors, 20 pre-professional programs, 100 graduate programs and 275 programs of study. College of Agricultural Sciences and Natural Resources College of Architecture College of Arts and Sciences College of Business College of Education and Human Sciences College of Engineering Hixson-Lied College of Fine and Performing Arts Co
Barricade, from the French barrique, is any object or structure that creates a barrier or obstacle to control, block passage or force the flow of traffic in the desired direction. Adopted as a military term, a barricade denotes any improvised field fortification, such as on city streets during urban warfare. Barricades include temporary traffic barricades designed with the goal of dissuading passage into a protected or hazardous area or large slabs of cement whose goal is to prevent forcible passage by a vehicle. Stripes on barricades and panel devices slope downward in the direction traffic must travel. There are pedestrian barricades - sometimes called bike rack barricades for their resemblance to a now obsolete form of bicycle stand, or police barriers, they originated in France 50 years ago and are now produced around the world. They were first produced in the U. S. 40 years ago by Friedrichs Mfg for New Orleans's Mardi Gras parades. Anti-vehicle barriers and blast barriers are sturdy barricades that can counter vehicle and bomb attacks.
The origins of the barricade are erroneously traced back to the "First Day of the Barricades", a confrontation that occurred in Paris on 12 May 1588 in which the supporters of the Duke of Guise and the ultra-Catholic Holy League challenged the authority of King Henri III. In actuality, although barricades came to widespread public awareness in that uprising, none of several conflicting claims concerning who may have "invented" the barricade stand up to close scrutiny for the simple reason that Blaise de Monluc had documented insurgents' use of the technique at least as early as 1569 in religiously based conflicts in southwestern France. Although barricade construction began in France in the sixteenth century and remained an French practice for two centuries, the nineteenth century remained the classic era of the barricade. Contrary to a number of historical sources, barricades were present in various incidents of the great French Revolution of 1789, but they never played a central role in those events.
They were, however, a visible and consequential element in many of the insurrections that occurred in France throughout the 1800s, including in the revolutions of 1830 and 1848 Other Parisian events included the June Rebellion of 1832, smaller in scale, but rendered famous by Victor Hugo's account in Les Misérables, the combat that ended the Paris Commune in May 1871, the more symbolic structures created in May 1968. The barricade began its diffusion outside France in the 1780s and played a significant role in the Belgian Revolution of 1830, but it was only in the course of the upheaval of 1848 that it became international in scope, its spread across the Continent was aided by the circulation of students, political refugees, itinerant workers through the French capital, where many gained first-hand experience of one or another Parisian insurrection. The barricade had, by the middle of the nineteenth century, become the preeminent symbol of a revolutionary tradition that would spread worldwide.
Barricade references appear in many colloquial expressions and are used metaphorically, in poems and songs celebrating radical social movements. Barricades are used for crowd control applications at public events or during exceptionally busy shopping times. Different types of barricade are designed to fit the environment and use cases the organizer decides on. Bridge Feet Typically used for outdoor use, where the ground is not flat; the bridge design of the feet allows for better stability. Flat Feet Used on surfaces such as streets and tarmacs these barricades are designed for use on flat surfaces. Heavy Duty Feet Similar to flat feet, but larger in size and made of heavy duty steel, allowing for more durability and support. Barricade Gates These gates swing open like a doorway, allowing for passage of people of goods through a run of barricades. Expanding Barricades Designed for indoor use and for use on sites where construction or work is occurring. Easy to move and store these barricades serve as a temporary barricade.
Bulwark Border barrier Rampart Jersey barrier Visi-Flash Barricade Lights
National Academies of Sciences, Engineering, and Medicine
The National Academies of Sciences and Medicine is the collective scientific national academy of the United States. The name is used interchangeably in two senses: as an umbrella term for its three quasi-independent honorific member organizations, and as the brand for studies and reports issued by the operating arm of the three academies, the National Research Council. The NRC was first formed in 1916 as an activity of the NAS. Now jointly governed by all three academies, it produces some 200 publications annually which are published by the National Academies Press; the US National Academy of Sciences was created by an Act of Incorporation dated March 3, 1863, signed by President of the United States Abraham Lincoln The Act stated that "... the Academy shall, whenever called upon by any department of the Government, examine and report upon any subject of science or art.... " With the American civil war raging, the new Academy was presented with few problems to solve, but it did address matters of "... coinage and measures, iron ship hulls, the purity of whiskey..."
All subsequently affiliated organizations have been created under this same overall congressional charter, including the two younger academies, National Academy of Engineering and NAM. Under this same charter, the National Research Council was created in 1916. On June 19 of that year US President Woodrow Wilson requested that the National Academy of Sciences organize a "National Research Council"; the purpose of the Council was in part to foster and encourage "the increased use of scientific research in the development of American industries... the employment of scientific methods in strengthening the national defense... and such other applications of science as will promote the national security and welfare."At the time, the Academy's effort to support national defense readiness, the Committee on Nitric Acid Supply, was approved by Secretary of War Newton D. Baker. Nitric acid was the substance basic in the making of propellants such as cordite, high explosives, dyes and other products but availability was limited due to World War I.
The NRC, through its committee, recommended importing Chilean saltpeter and the construction of four new ordinance plants. These recommendations were accepted by the War Department in June 1917, although the plants were not completed prior to the end of the war. In 1918, Wilson formalized the NRC's existence under Executive Order 2859. Wilson's order declared the function of the NRC to be in general: "o stimulate research in the mathematical. Physical, biological sciences, and in the application of these sciences to engineering, agriculture. Medicine, and other useful arts. With the object of increasing knowledge, of strengthening the national defense, of contributing in other ways to the public welfare."During World War I, the United States was at war, the NRC operated as the Department of Science and Research of the Council of National Defense as well as the Science and Research Division of the United States Army Signal Corps. When war was first declared, the Council had organized committees on gas warfare.
On June 1, 1917, the council convened a meeting of scientific representatives of the United Kingdom and France with interested parties from the U. S. on the subject of submarine detection. Another meeting with the British and French was held in Paris in October 1918, at which more details of their work was disclosed; as a result of these meetings, the NRC recommended that scientists be brought together to work on the problems associated with submarine detection. Due to the success of council-directed research in producing a sound-based method of detecting submarines, as well as other military innovations, the NRC was retained at the end of the war, though it was decoupled from the military. NRC's Articles of Organization have been changed only three times: in 1956, January 1993, July 2015; the National Academy of Sciences, National Academy of Engineering and National Academy of Medicine are honorary membership organizations, each of which has its own governing Council, each of which elects its own new members.
The membership of the three academies totals more than 6,300 scientists and health professionals. New members for each organization are elected annually by current members, based on their distinguished and continuing achievements in original research. By the terms of the original 1863 Congressional charter, the three academies serve pro bono as "advisers to the nation on science and medicine." The program units known as the National Research Council, are collectively the operating arm of the three academies for the purpose of providing objective policy advice. Although separately chartered, it falls under the overall charter of the National Academy of Sciences, whose ultimate fiduciary body is the NAS Council. In actual practice, the NAS Council delegates governing authority to a Governing Board of the National Research Council, chaired jointly by the presidents of the three academies, with additional members chosen by them or specified in the charters of the academies. Under this three-academy umbrella, the program units produce reports that shape policies, inform public opinion, advance the pursuit of science and medicine.
There are seven major divisions: Division of Behavioral and Social Sciences and Education, Division of E