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Bucha Effect
Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves. The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy. This phenomenon has been observed during helicopter flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes. Flicker vertigo in a helicopter occurs when the pilot or front passenger looks up through the blades of the main rotor as it turns in the sun causing the light to strobe. The strobe light effect can cause persons who are vulnerable to flicker vertigo to experience symptoms such as: * Become dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disorientation
Orientation is a function of the mind involving awareness of three dimensions: time, Location (geography), place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to Substance intoxication, intoxication. Typically, disorientation is first in time, then in place and finally in person. Assessment In the context of an accident or major trauma, the emergency medical technician#Emergency Medical Responder, Emergency Medical Responder performs spiraling (increasingly detailed) assessments which guide the critical first response. Assessment of mental orientation typically lands within the immediate top three priorities: # Safety - Assess the area safety (potential traffic, fire, overhead/underfoot objects and collapse risks, rushing water, gunfire, chemical/radiation threats, storm conditions, downed power lines, etc.), wait for the threat to subside, or move the person to safety if and when possible, all without endang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Transportation Safety Board
The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine accidents, pipeline incidents, bridge failures, and railroad accidents. The NTSB is also in charge of investigating cases of hazardous materials releases that occur during transportation. The agency is based in Washington, D.C. It has four regional offices, located in Anchorage, Alaska; Denver, Colorado; Ashburn, Virginia; and Seattle, Washington. The agency also operates a national training center at its Ashburn facility. History The origin of the NTSB was in the Air Commerce Act of 1926, which assigned the United States Department of Commerce responsibility for investigating domestic aviation accidents. Before the NTSB, the Federal Aviation Administration's (FAA; at the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Safety
Aviation safety is the study and practice of managing risks in aviation. This includes preventing aviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of aircraft and aviation infrastructure. The aviation industry is subject to significant regulation and oversight. Aviation security is focused on protecting air travelers, aircraft and infrastructure from intentional harm or disruption, rather than unintentional mishaps. Statistics Evolution In 1926 and 1927, there were a total of 24 fatal commercial airline crashes, a further 16 in 1928, and 51 in 1929 (killing 61 people), which remains the worst year on record at an accident rate of about 1 for every flown. Based on the current numbers flying, this would equate to 7,000 fatal incidents per year. For the ten-year period 2002 to 2011, 0.6 fatal accidents happened per one million flights globally, 0.4 per million hours flown, 22.0 fatali ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crowd Control
Crowd control is a public security practice in which large crowds are managed in order to prevent the outbreak of crowd crushes, affray, fights involving drunk and disorderly people or riots. Crowd crushes in particular can cause many hundreds of fatalities. Effective crowd management is about managing expected and unexpected crowd occurrences. Crowd control can involve privately hired security guards as well as police officers. Crowd control is often used at large, public gatherings like street fairs, music festivals, stadiums and public demonstrations. At some events, security guards and police use metal detectors and sniffer dogs to prevent weapons and drugs being brought into a venue. Equipment Materials such as stanchions, crowd control barriers, fences and decals painted on the ground can be used to direct a crowd. A common method of crowd control is to use high visibility fencing to divert and corral pedestrian traffic to safety when there is any potential threat for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-lethal Weapon
Non-lethal weapons, also called nonlethal weapons, less-lethal weapons, less-than-lethal weapons, non-deadly weapons, compliance weapons, or pain-inducing weapons are weapons intended to be less likely to kill a living target than conventional weapons such as knives and firearms with live ammunition. It is often understood that unintended or incidental casualties are risked wherever force is applied, but non-lethal weapons try to minimise the risk of casualties (e.g. serious/permanent injuries or death) as much as possible. Non-lethal weapons are used in policing and combat situations to limit the escalation of conflict where employment of lethal force is prohibited or undesirable, where rules of engagement require minimum casualties, or where policy restricts the use of conventional force. These weapons occasionally cause serious injuries or death; the term "less-lethal" has been preferred by some organizations as it describes the risks of death more accurately than the term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seizure
An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with loss of consciousness ( tonic-clonic seizure), to shaking movements involving only part of the body with variable levels of consciousness (focal seizure), to a subtle momentary loss of awareness ( absence seizure). Most of the time these episodes last less than two minutes and it takes some time to return to normal. Loss of bladder control may occur. Seizures may be provoked and unprovoked. Provoked seizures are due to a temporary event such as low blood sugar, alcohol withdrawal, abusing alcohol together with prescription medication, low blood sodium, fever, brain infection, or concussion. Unprovoked seizures occur without a known or fixable cause such that ongoing seizures are likely. Unprovoked seizures may be exacerbated by stress or sl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strobe
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning "act of whirling". A typical commercial strobe light has a flash energy in the region of 10 to 150 joules, and discharge times as short as a few milliseconds, often resulting in a flash power of several kilowatts. Larger strobe lights can be used in “continuous” mode, producing extremely intense illumination. The light source is commonly a xenon flash lamp, or ''flashtube'', which has a complex spectrum and a color temperature of approximately 5,600 kelvins. To obtain colored light, colored gels may be used. Scientific explanation of flashtubes Strobe lights usually use flashtubes with energy supplied from a capacitor, an energy storage device much like a battery, but capable of charging and releasing energy much faster. In a ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicopter Rotor
A helicopter main rotor or rotor system is the combination of several rotary wings (rotor blades) with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words ''helix'', helik-, meaning spiral; and ''pteron'' meaning wing. Design principles Overview The helicopter rotor is powered by the engine, through the transmission, to the rotating mast. The mast is a cylindrical metal shaft that extends upward from—and is driven by—the transmission. At the top of the mast i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertigo (medical)
Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties walking. It is typically worse when the head is moved. Vertigo is the most common type of dizziness. The most common disorders that result in vertigo are benign paroxysmal positional vertigo (BPPV), Ménière's disease, and labyrinthitis. Less common causes include stroke, brain tumors, brain injury, multiple sclerosis, migraines, trauma, and uneven pressures between the middle ears. Physiologic vertigo may occur following being exposed to motion for a prolonged period such as when on a ship or simply following spinning with the eyes closed. Other causes may include toxin exposures such as to carbon monoxide, alcohol, or aspirin. Vertigo typically indicates a problem in a part of the vestibular system. Other causes of dizziness include ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of STOL (Short TakeOff and Landing) or STOVL (Short TakeOff and Vertical Landing) aircraft cannot perform without a runway. In 1942, the Sikorsky R-4 became the first helicopter to reach full-scale production.Munson 1968.Hirschberg, Michael J. and David K. Dailey"Sikorsky". ''US and Russian Helicopter Development in the 20th Century'', American Helicopter Society, International. 7 July 2000. Although most earlier designs used more than one main rotor, the configuration of a single main rotor accompanied by a vertical anti-torque tail rotor (i.e. unicopter, not to be confused with the single-blade monocopter) has become the most comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosensitive Epilepsy
Photosensitive epilepsy (PSE) is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights; bold, regular patterns; or regular moving patterns. PSE affects approximately one in 4,000 people (5% of those with epilepsy). Signs and symptoms People with PSE experience epileptiform seizures upon exposure to certain visual stimuli. The exact nature of the stimulus or stimuli that triggers the seizures varies from one patient to another, as does the nature and severity of the resulting seizures (ranging from brief absence seizures to full tonic–clonic seizures). Many PSE patients experience an " aura" or feel odd sensations before the seizure occurs, and this can serve as a warning to a patient to move away from the trigger stimulus. The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing lights or rapidly changing or alternating images (as in clubs, around ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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