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HV

High voltage (HV) denotes an electric potential sufficiently elevated to pose risks of arcing, tissue damage, or equipment failure upon contact or breakdown.^[1]^[2] In electrical engineering contexts, HV is conventionally classified as exceeding 1000 volts root mean square for alternating current (AC) systems or 1500 volts for direct current (DC) systems, though thresholds vary by application and regulatory standards.^[1]^[3] These systems form the backbone of power generation, transmission, and distribution networks, enabling efficient delivery of electricity over vast distances by reducing resistive losses through elevated potentials.^[4] Key applications of HV include overhead transmission lines operating at 35 kV to over 230 kV, which minimize energy dissipation via the physics of lower current for equivalent power (P = V × I).^[4] High-voltage engineering encompasses specialized techniques for insulation, such as gas-insulated switchgear and composite materials, to prevent dielectric breakdown under stress from voltage gradients, environmental factors, or transients like lightning.^[2] Notable advancements involve high-voltage direct current (HVDC) links, which offer superior efficiency for undersea cables and interconnections between asynchronous grids, as demonstrated in projects transmitting power with minimal conversion losses.^[5] Safety protocols and testing regimes define HV operations, including impulse withstand tests simulating surges and mandatory interlocks to avert human exposure.^[6] Controversies arise from empirical studies on non-ionizing electromagnetic fields from HV lines, where some data suggest correlations with health effects like childhood leukemia at exposure levels above 0.3–0.4 μT, though causal mechanisms remain unestablished and debated amid confounding variables.^[7] Overall, HV infrastructure underpins modern electrification but demands rigorous causal analysis of failure modes, from corona discharge to partial discharges, to ensure reliability.^[8]

Electricity and Electronics

High voltage

High voltage in electrical engineering denotes electric potential differences sufficiently elevated to necessitate specialized equipment, safety protocols, and insulation to prevent arcing, dielectric breakdown, or human injury. Thresholds vary by regulatory body and application; the U.S. Department of Energy classifies voltages over 600 volts as high voltage for safety guidelines in facilities.^[9] The National Electrical Code specifies requirements for installations exceeding 1,000 volts nominal, distinguishing them from lower-voltage systems due to increased risks of flashover and equipment failure.^[10] In international contexts, such as IEC standards, high voltage often begins above 1 kV for alternating current or 1.5 kV for direct current, though power transmission categorizes lines from 69 kV upward as high voltage to enable efficient bulk energy transfer.^[11] The primary rationale for employing high voltage in power transmission stems from fundamental electrical principles: power P = V \times I, where elevating voltage V reduces current I for a fixed power level, thereby minimizing I^2 R losses per Joule's law, with R as conductor resistance.^[12] This efficiency allows transmission over hundreds of kilometers with losses under 5% in well-designed systems, compared to prohibitive dissipation at lower voltages.^[13] High-voltage alternating current (HVAC) predominates, but high-voltage direct current (HVDC) offers advantages in asynchronous grid interconnections and submarine cables by eliminating reactive power losses and skin effect, though it requires costly converter stations.^[14] Historically, high-voltage transmission emerged in the late 19th century amid the "War of Currents," with Westinghouse's 1895 Niagara Falls hydroelectric plant generating 2,200 kW at 11,000 volts—among the first commercial AC systems demonstrating scalability over direct current's limitations.^[15] Subsequent advancements, including transformers invented by William Stanley in 1885, enabled voltage stepping for grid expansion, evolving to ultra-high voltages exceeding 1,000 kV in modern lines like China's 1,100 kV systems for inter-regional supply.^[16] Safety considerations dominate high-voltage operations, as potentials above 50 volts AC or DC can drive lethal currents through the body via paths of low resistance, per OSHA mandates requiring guarding of live parts to avert accidental contact.^[17] Arc flash hazards escalate exponentially with voltage, capable of energies over 40 cal/cm²—far beyond protective gear ratings—necessitating lockout-tagout procedures, insulated tools, and minimum approach distances scaled to voltage class (e.g., 10 feet for lines up to 50 kV).^[18] Occupational fatalities from high-voltage exposure often result from phase-to-ground faults or induced voltages, underscoring empirical data from incident reports showing current, not voltage alone, as the proximate cause of ventricular fibrillation when exceeding 10-20 mA through the heart.^[19]

Hectovolt

The hectovolt (symbol: hV) is a unit of electric potential difference derived from the International System of Units (SI) prefix "hecto-", which represents a factor of [10^2](/page/10+2).^[20] It equals 100 volts (V), such that 1 hV = 100 V.^[21]^[22] This unit is formally valid as an SI multiple but sees limited practical application in electrical engineering or physics, where the base volt or prefixes like kilo- (kV, $10^3 V) and mega- (MV, $10^6 V) predominate for expressing potentials ranging from household circuits to high-voltage transmission.^[20] Conversion calculators recognize the hectovolt primarily for theoretical or archival purposes, confirming its equivalence without evidence of widespread adoption in standards bodies like the International Electrotechnical Commission (IEC).^[23]^[24]

Materials Science and Mechanics

Vickers hardness

The Vickers hardness test determines a material's resistance to plastic deformation by pressing a diamond indenter, shaped as a square pyramid with a 136° face-to-face angle, into the surface under a controlled load, then measuring the indentation's diagonals optically. The resulting Vickers hardness value, denoted HV, quantifies hardness in units of kgf/mm² and applies to a wide range of materials including metals, ceramics, and thin coatings, distinguishing it from methods like Brinell that use larger indenters unsuitable for micro-scale testing.^[25]^[26] Developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd. in the United Kingdom, the test addressed limitations of the Brinell method by enabling precise measurements across load scales, from microhardness (loads ≤1 kgf for small or thin specimens) to macrohardness (loads >1 kgf up to 120 kgf). This innovation allowed consistent testing of diverse material thicknesses and hardness levels without requiring separate indenters, establishing Vickers as a standard for quality control in industries like aerospace and manufacturing.^[27]^[28]^[29] The test procedure, governed by standards such as ISO 6507 (parts 1-4 for calibration, verification, and execution) and ASTM E384 (for microindentation) or E92 (for standard loads), involves preparing a polished, flat specimen surface perpendicular to the load direction. A load is applied via the indenter for a dwell time of 10-15 seconds to ensure full penetration, followed by removal and microscopic measurement of the two diagonals (d1 and d2) of the square indentation, with the average d = (d1 + d2)/2. The hardness is calculated using the formula HV = 1.854 × (F / d²), where F is the load in kgf and d is in mm; for SI units, the value converts to MPa by multiplying HV by 9.807.^[30]^[31]^[32] This optical method yields high precision, with diagonal measurements accurate to 0.1 μm in automated systems, making it ideal for gradient hardness profiles or case-hardened layers where effective case depth is assessed by plotting hardness versus distance from the surface. Limitations include sensitivity to surface preparation—requiring flatness within 0.75 μm and minimal edge effects (indentation at least 2.5d from edges)—and potential cracking in brittle materials under high loads. Compared to Rockwell, Vickers provides a broader applicability without preliminary load adjustments, though it demands skilled optical interpretation or digital imaging for consistency.^[25]^[33]

High velocity

High-velocity impacts refer to collisions between projectiles and target materials at speeds generally exceeding 1 km/s, regimes in which inertial and hydrodynamic effects dominate over material strength, leading to behaviors akin to fluid flow under extreme pressures.^[34] In materials science, these impacts are distinguished from low-velocity events (below ~100 m/s, where quasi-static deformation prevails) and intermediate velocities (~100 m/s to 1 km/s, involving localized plasticity and fracture); at high velocities, compressive stresses surpass yield strengths by orders of magnitude, often exceeding 10 GPa, causing phase transitions, melting, or vaporization within microseconds.^[35] This hydrodynamic approximation simplifies modeling, treating solids as compressible fluids with equations of state derived from shock physics experiments.^[36] Material responses under high-velocity impacts include cratering, where the crater depth scales with projectile velocity to the power of approximately 2/3 under hydrodynamic limits, and fragmentation, driven by tensile wave reflections and spallation.^[37] For instance, in metallic targets, impacts at 2-5 km/s can produce ejecta velocities up to half the impact speed, with debris characterized by size distributions following power-law relations observed in both experiments and simulations.^[38] Polymers and composites exhibit anisotropic damage, with fiber-reinforced materials showing delamination and shear banding at velocities above 1 km/s, as quantified in ultra-high-performance concrete tests using spherical steel projectiles at ~800 m/s, revealing penetration depths correlated to target compressive strength of ~115 MPa.^[39] These phenomena are informed by multiscale modeling, integrating atomistic molecular dynamics for nanoscale dislocation dynamics with continuum finite element methods for macroscopic failure.^[35] Experimental techniques for studying high-velocity impacts employ gas guns, light-gas guns, and explosive-driven systems to achieve velocities up to 10 km/s, with diagnostics including high-speed imaging at frame rates exceeding 10^6 fps and particle image velocimetry for ejecta characterization.^[38] Micrometer-scale projectiles, accelerated via electromagnetic railguns or laser ablation, enable controlled tests spanning 15 orders of magnitude in mass, revealing rebound coefficients and erosion rates dependent on impact angles and material hardness (e.g., Vickers hardness variations post-impact).^[40] Such data underpin applications in predicting responses to space debris or micrometeoroids, with simulations validating empirical scaling laws like the Humes cratering equation for hypervelocity regimes.^[41]

Aviation and Aerospace

Height-velocity diagram

The height-velocity diagram, also known as the HV diagram or "dead man's curve," is a graphical representation used in helicopter flight operations to delineate combinations of altitude and airspeed from which a safe autorotative landing is feasible following an engine failure.^[42] It plots altitude on the vertical axis against airspeed on the horizontal axis, with the shaded or bounded region indicating the "avoid" area where insufficient kinetic energy or time exists to execute a controlled autorotation, potentially leading to a hard landing or crash.^[43] The diagram is mandatory in every helicopter's pilot operating handbook (POH) and serves as a critical safety tool for pilots, emphasizing avoidance of low-altitude, low-airspeed flight profiles that limit deceleration and flare capabilities during power loss.^[44] The curve's shape features a characteristic "knee" at approximately 100-200 feet above ground level (AGL) and 20-40 knots indicated airspeed, depending on the helicopter model, beyond which autorotation becomes viable due to adequate rotor inertia and translational lift for energy management.^[42] Below the knee, the avoid region expands, as low height restricts descent time for rotor RPM decay recovery, while low velocity provides insufficient forward momentum for a 180-degree turn or flare to arrest descent rate.^[45] For multi-engine helicopters, separate curves may apply for single-engine failure versus total power loss, with the former allowing continued flight outside the critical envelope.^[44] Determination of the HV diagram involves flight testing by certified pilots under Federal Aviation Administration (FAA) oversight, incorporating a one-second pilot reaction delay above the knee and assuming landing on a smooth, hard surface without obstacles.^[46] Variations occur with environmental and configurational factors: higher density altitudes shift the curve rightward due to reduced rotor efficiency, while increased gross weight demands higher minimum airspeeds for energy storage.^[45] Pilots must reference model-specific diagrams, as generalizations across helicopters can underestimate risks; for instance, empirical data from NASA investigations confirm that disc loading and inertia ratios causally influence the envelope's boundaries.^[45] Operationally, the HV diagram underscores causal risks in helicopter accidents, where 20-30% of engine-out events in the avoid region result in substantial damage or fatalities, per FAA safety analyses, due to inadequate pre-impact energy dissipation.^[42] Training mandates avoidance of the curve during takeoff and landing phases, favoring profiles that maintain airspeeds above 60 knots or altitudes exceeding 500 feet AGL for margin.^[43] Advances in rotor design, such as higher inertia blades, can expand the safe region, but empirical validation through testing remains essential, as theoretical models alone overpredict margins without accounting for real-world delays and terrain effects.^[45]

Military and Defense

Military units

The abbreviation HV designates several territorial defense and army units in Europe. Hrvatska vojska (HV) was the official name of the Croatian Army from its formation on 3 November 1991, when the Croatian National Guard Corps (Zbor narodne garde) was reorganized amid the Croatian War of Independence against Yugoslav forces, until its restructuring in the early 2000s as part of broader military reforms following Croatia's 2001 constitutional changes to the armed forces.^[47] The HV grew from irregular volunteer formations in 1991, numbering around 30,000 personnel by mid-1992, to a professional force exceeding 200,000 active and reserve troops at its peak during operations like Storm in 1995, which liberated significant territories from Serb control.^[47] Heimevernet (HV) is the Norwegian Home Guard, established on 6 December 1946 as a volunteer rapid-mobilization force to bolster territorial defense following World War II occupation experiences.^[48] It comprises approximately 40,500 personnel across districts nationwide, focusing on local defense, infrastructure protection, and support to regular forces in crises, with mandatory training emphasizing light infantry tactics and civil-military cooperation.^[49] Hemvärnet refers to the Swedish Home Guard, a reserve component of the Swedish Armed Forces created on 29 May 1940 during World War II to provide voluntary local defense against potential invasion, evolving into modern units responsible for territorial security and societal support.^[50] Organized into about 40 battalions with roughly 20,000-30,000 volunteers, it equips members with small arms, anti-tank weapons, and conducts annual exercises for rapid deployment in hybrid threats or wartime scenarios.^[51] Hjemmeværnet (HV or HJV) denotes the Danish Home Guard, founded in 1949 as Denmark's fourth military service branch to handle territorial defense and civil emergency roles post-World War II.^[52] Consisting mainly of volunteers numbering around 6,000-7,000 active members plus reserves, it supports regular forces through surveillance, search-and-rescue, and cyber defense tasks, including recent additions like two Twin Otter aircraft for maritime patrol commissioned in January 2025.^[53]^[54]

High-velocity ammunition

High-velocity ammunition consists of cartridges engineered to impart significantly elevated muzzle velocities to projectiles, typically exceeding 2,500 feet per second (fps) for rifle rounds and often surpassing 3,000 fps in modern designs, compared to standard-velocity loads.^[55]^[56] This is achieved through optimized propellant charges, lighter bullet weights, and aerodynamic bullet profiles, such as spitzer or boat-tail designs, which reduce drag and maintain supersonic speeds over greater distances.^[57] The resulting kinetic energy, calculated as \frac{1}{2}mv^2, scales quadratically with velocity, enabling enhanced penetration and terminal effects.^[58] In ballistic performance, high-velocity rounds produce flatter trajectories with reduced bullet drop—for instance, a 3,000 fps projectile experiences approximately half the drop at 300 yards compared to a 2,000 fps equivalent—facilitating accurate long-range fire without extensive sight adjustments.^[55] They also generate greater hydrodynamic shock upon impact, creating larger temporary wound cavities through rapid energy transfer, which expands tissues radially beyond the permanent bullet path.^[59] However, this can lead to over-penetration in soft targets if not paired with expanding projectiles, as the high sectional density maintains straight-line travel through tissue.^[60] Military analyses emphasize that velocities above 2,000 fps are critical for yawing and fragmentation in intermediate cartridges, amplifying incapacitation over subsonic or standard pistol rounds.^[59] Historically, high-velocity ammunition emerged in the late 19th century with the adoption of smokeless powder, which supplanted black powder's velocity ceiling of about 1,500 fps and enabled cartridges like the .256 Newton (introduced 1913) achieving over 3,000 fps.^[61]^[62] In military contexts, the shift to small-caliber, high-velocity (SCHV) designs accelerated post-World War II, exemplified by the 5.56x45mm NATO round standardized in 1980, with muzzle velocities of 2,970 fps from a 20-inch barrel, prioritizing volume of fire and controllability over raw power.^[63] The U.S. Army's M855A1 enhanced performance round, fielded in 2010, further refines this with copper-core construction and velocities around 3,000 fps, improving hard-target penetration by 25% and consistent wounding through better yaw initiation.^[64] Contemporary developments include hypervelocity projectiles (HVP), such as those tested by BAE Systems since 2012, reaching speeds over 5,600 fps from naval railguns or conventional artillery, designed for anti-air and surface threats with low-drag aerodynamics.^[65] These prioritize modular compatibility across platforms, reducing logistics burdens while delivering Mach 5+ impacts for extended range—up to 100 nautical miles—though challenges like barrel wear from extreme pressures persist.^[65] In small arms, high-velocity loads remain standard for assault rifles, balancing lethality with soldier portability, as evidenced by NATO's adherence to 5.56mm specifications ensuring interoperability.^[64]

Transportation

Heavy vehicle

A heavy vehicle is a category of commercial motor vehicle designed primarily for transporting goods, passengers, or specialized equipment, distinguished by its high gross vehicle weight rating (GVWR) that exceeds thresholds for light-duty vehicles. In the United States, heavy vehicles are commonly classified under Federal Highway Administration (FHWA) standards into Classes 7 and 8, encompassing vehicles with a GVWR greater than 26,000 pounds (11,793 kg), including tractor-trailers, dump trucks, and refuse haulers.^[66] These classifications rely on GVWR to ensure safety compliance and prevent overloading, with Class 7 vehicles ranging from 26,001 to 33,000 pounds and Class 8 exceeding 33,000 pounds.^[67] Common types of heavy vehicles include rigid trucks for local haulage, articulated combinations like semi-trailers for long-distance freight, and heavy-duty buses for mass transit. Examples encompass city transit buses with three or more axles, cement mixers, and mobile cranes, all engineered for payloads that demand robust chassis, multiple axles, and diesel or alternative-fuel powertrains.^[66] In global contexts, such vehicles often feature configurations like the European Modular System (EMS) in select countries, allowing lengths up to 25.25 meters and weights to 60 tonnes on designated networks to optimize efficiency.^[68] Regulations on heavy vehicles emphasize weight limits to protect infrastructure and safety; for instance, U.S. interstate highways permit a maximum gross weight of 80,000 pounds (36,287 kg) under federal law, subject to axle distributions.^[69] In the European Union, Directive 96/53/EC caps standard heavy-duty vehicles at 40 tonnes for national and international transport, with exceptions for intermodal containers reaching 44 tonnes.^[70] These limits, enforced via weigh stations and permits, vary nationally—such as 21 to 56 tonnes in the UAE based on axle count—to balance economic utility against road wear and emissions impacts.^[71] Operators must adhere to specialized licensing, like commercial driver's licenses in the U.S., and vehicle maintenance standards to mitigate risks such as brake failures under load.^[72]

Airline codes

HV is the IATA airline designator for Transavia Airlines CV, a Dutch low-cost carrier headquartered in Amsterdam and operating primarily short-haul leisure flights within Europe and to select North African destinations.^[73]^[74] The airline, established on November 17, 1965, as a charter operator by Transavia International before transitioning to scheduled low-cost services, functions as a wholly owned subsidiary of KLM and part of the Air France–KLM Group.^[73]^[75] Transavia's ICAO code is TRA, and it maintains its primary hub at Amsterdam Schiphol Airport, with secondary operations at Rotterdam The Hague Airport and Eindhoven Airport.^[73]^[75] As of October 2025, the airline serves approximately 98 airports across 294 routes, emphasizing point-to-point travel with a fleet of around 43 aircraft, predominantly Boeing 737 models.^[74]^[76]^[77] The HV code distinguishes Transavia from its French affiliate, Transavia France (IATA: TO), which operates separately under Air France–KLM branding from Paris Orly Airport.^[74]^[75] Transavia Airlines adheres to standard IATA protocols for flight numbering and reservations, prefixing bookings with 532 in some systems.^[78]

Organizations and Codes

Companies and groups

HV Capital, a venture capital firm based in Europe, invests in early-stage and growth technology companies across various sectors, managing funds that have backed over 230 portfolio companies since its founding as HV Holtzbrinck Ventures in 2000.^[79]^[80] HV Technologies, Inc., established as a provider of high-voltage and electromagnetic compatibility (EMC) test equipment, specializes in solutions for insulation testing, partial discharge measurement, and EMC compliance, serving industries such as power generation, utilities, and research institutions.^[81]^[82] Harvard College Ventures (HV), the largest student-run entrepreneurship and venture capital organization at Harvard University, supports undergraduates interested in startups by facilitating investments, networking, and educational programs in venture capital and innovation.^[83] HV Holdings Ltd., a conglomerate operating primarily in Mauritius and Madagascar with over 3,500 employees, engages in sectors including retail, distribution, international trade, and real estate, ranking among the top 100 companies in the Indian Ocean region.^[84]

Former country codes

The ISO 3166-1 alpha-2 code HV was assigned to Upper Volta (French: Haute-Volta), a former name for the West African nation now known as Burkina Faso, upon the standard's initial publication on December 15, 1974.^[85] This code remained in use until August 4, 1984, when the military government under Thomas Sankara officially renamed the country Burkina Faso—meaning "land of upright people" in local languages—and adopted the new alpha-2 code BF, along with alpha-3 code BFA and numeric code 854 (previously HVO for alpha-3).^[85]^[86] The change reflected a broader policy of rejecting colonial-era nomenclature, as Upper Volta had been so named by French colonial authorities in 1919 to reference the Volta River's upper reaches.^[87] Upper Volta had declared independence from France on August 5, 1960, under President Maurice Yaméogo, establishing it as a republic with Ouagadougou as its capital.^[88] The HV code facilitated international standardization for data exchange, including in trade, statistics, and telecommunications, during a period when the country faced economic challenges like droughts and reliance on cotton exports.^[89] Post-1984, legacy systems occasionally retained HV for historical references, though ISO 3166-1 deprecated it to avoid confusion; the code is now unassigned.^[85] Notably, the World Meteorological Organization continues to use HV for Burkina Faso in weather reporting, preserving the acronym from the French name despite the ISO transition.^[86]

Places

Geographic locations

The Hudson Valley, often abbreviated as HV, is a geographic region in the eastern United States, encompassing the valley and surrounding areas of the Hudson River in New York State. It extends approximately 150 miles from the Capital District near Albany southward to the Tappan Zee Bridge area near New York City, including counties such as Albany, Rensselaer, Columbia, Greene, Ulster, Dutchess, Orange, Putnam, Rockland, and Westchester.^[90]^[91] The region features a mix of urban, suburban, and rural landscapes, with elevations rising from the river floodplain to the Taconic, Catskill, and Ramapo Mountains, influencing its climate and ecology.^[92] HV also serves as the World Meteorological Organization (WMO) country code for Burkina Faso, derived from its former French colonial name, Haute-Volta (Upper Volta), which was used until the country's independence and renaming in 1984.^[93] This code reflects the historical geographic designation of the landlocked West African nation, covering about 274,200 square kilometers in the Sahel region, bordered by Mali, Niger, Benin, Togo, Ghana, and Ivory Coast.^[94] The Upper Volta name originated from the Volta River's upper reaches, highlighting the area's riverine and savanna geography prior to post-colonial administrative changes.^[94]

Other uses

Medical and biological terms

In medicine, HV commonly denotes hallux valgus, a progressive deformity of the first metatarsophalangeal joint characterized by lateral deviation of the great toe toward the lesser toes, often accompanied by medial prominence of the metatarsal head (bunion) and associated with biomechanical factors such as pes planus or genetic predisposition; prevalence increases with age, affecting up to 35% of adults over 65 in population studies.^[95] HV also refers to hantavirus, a genus within the family Hantaviridae of negative-sense single-stranded RNA viruses primarily hosted by rodents, capable of zoonotic transmission to humans via inhalation of aerosolized excreta, leading to hemorrhagic fever with renal syndrome (HFRS) in Eurasia or hantavirus pulmonary syndrome (HPS) in the Americas; for instance, Sin Nombre virus, a prominent North American species, has a case fatality rate of 30-40%.^[96] Anatomically, HV signifies the hepatic vein, which drains deoxygenated blood from the liver lobules into the inferior vena cava, comprising right, middle, and left branches that converge near the hepatic hilum; imaging studies, such as ultrasound or CT, routinely visualize these veins to assess for thrombosis or congestion in conditions like Budd-Chiari syndrome.^[97]^[96] In cardiac electrophysiology, the HV interval measures the conduction time from the His bundle (proximal) to ventricular myocardium activation, typically 35-55 milliseconds in healthy adults, recorded via intracardiac electrogram during sinus rhythm; prolongation beyond 55 ms indicates infra-Hisian conduction delay, a risk factor for complete heart block, as evidenced in electrophysiological studies correlating HV duration with bradyarrhythmia progression.^[98]^[99] Biologically, HV designates voltage-gated proton channels (also Hv or Hv1), integral membrane proteins encoded by the VSOP/Hv1 gene that selectively conduct H⁺ ions outward in response to membrane depolarization, playing roles in pH regulation, oxidative burst in phagocytes, and sperm capacitation; these channels exhibit a unique property where proton efflux aligns with electrochemical gradients without counterion permeability, as detailed in biophysical characterizations showing activation thresholds around -20 mV and rectification favoring efflux.^[100]^[101]

Miscellaneous acronyms

In electrical engineering and power distribution, HV denotes high voltage, referring to transmission or distribution systems operating above 1,000 volts for alternating current or 1,500 volts for direct current, as defined in standards like those from the International Electrotechnical Commission.^[102]^[3] This usage distinguishes HV from low-voltage systems in household or light industrial applications, enabling efficient long-distance power transfer with reduced current and line losses.^[103] In ballistics, aerodynamics, and physics, HV abbreviates high velocity, describing projectiles, fluids, or particles moving at speeds significantly exceeding standard rates, such as bullets exceeding 1,200 meters per second in rifle ammunition.^[3]^[104] This term appears in contexts like ammunition specifications, where HV rounds prioritize speed for flatter trajectories and greater impact energy over weight considerations.^[103] HV also stands for heating value in thermodynamics and fuel analysis, quantifying the amount of heat released during complete combustion of a unit mass or volume of fuel, expressed in megajoules per kilogram or British thermal units per pound; for example, natural gas typically has a higher heating value of around 38-39 MJ/m³.^[105] This metric, measured via bomb calorimetry, accounts for latent heat of vaporization in products like water, aiding in efficiency calculations for engines and power plants.^[103] In chemistry and fluid dynamics, HV represents high viscosity, characterizing substances resisting flow due to internal friction, such as oils or polymers with viscosities exceeding 10,000 centipoise at operating temperatures.^[105] This abbreviation facilitates comparisons in lubrication engineering, where HV fluids maintain performance across temperature ranges, unlike low-viscosity alternatives prone to thinning.^[103]

References

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ASTM E92 is a standardized method in the standard and low force range (200 gf - 120 kgf), used for determination of the Vickers hardness and Knoop hardness of ...
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Vickers Hardness Testing - Buehler - Metallography Equipment ...
Nov 16, 2021 · Vickers and Knoop hardness test methods are defined in the following standards: ASTM E384 and ISO 6507. It is recommended that operators ...
[32]
Vickers Hardness Test - Gordon England Thermal Spray Coating
The Vickers hardness is the quotient obtained by dividing the kgf load by the square mm area of indentation. ... When the mean diagonal of the indentation has ...
[33]
Vickers Hardness Testing - an overview | ScienceDirect Topics
Vickers hardness testing is carried out to standards such as ASTM E384 or ISO 6507 which has four parts describing the test itself, calibration and hardness ...
[34]
High Impact Velocity - an overview | ScienceDirect Topics
High velocity impact refers to the collision of a projectile with a target material at velocities typically in the range of a few kilometers per second, ...
[35]
High-Velocity Impact Modeling in Materials Science: A Multiscale ...
Feb 2, 2024 · High-velocity impact modeling within materials science enables a deep understanding of material behavior under extreme dynamic loading ...
[36]
High-velocity dust impacts in plasma facing materials: Insights from ...
High-velocity dust impacts in plasma facing materials: Insights from molecular dynamics simulations. Author links open overlay panel. Prashant Dwivedi a
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[PDF] Fragmentation by high velocity impact on a target - HAL
Large, P. Guigon, High velocity impact of particles on a target. An experimental study, International Journal of Mineral. Processing 44–45 (1996) ...
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High-velocity micro-projectile impact testing - AIP Publishing
Mar 18, 2021 · Here we review experimental methods for high-velocity impacts spanning 15 orders of magnitude in projectile mass and compare method performances.
[39]
High-velocity impact experiments and quantitative damage ...
Dec 11, 2023 · We present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa ...<|separator|>
[40]
High velocity measurements of particle rebound characteristics ...
Apr 15, 2021 · HV, 1100, 300 − 400, 218. GPa, 10.79, 2.94 ... Rebound mechanics of micrometre-scale, spherical particles in high-velocity impacts.
[41]
High-Velocity Impact of Metal Microparticles - DSpace@MIT
High-Velocity Impact of Metal Microparticles. Author(s). Lienhard, Jasper Z ... Department of Materials Science and Engineering. Publisher. Massachusetts ...
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[PDF] The H/V Curve
The H/V curve is a chart showing height and airspeed combinations where a safe landing after engine failure is difficult, or nearly impossible.Missing: aviation | Show results with:aviation
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[PDF] Helicopter Flying Handbook (FAA-H-8083-21B) Chapter 7
The height/velocity diagram[Figure 7-1]depicts altitude and airspeed situations from which a successful autorotation can be made. The time required, and ...
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Understanding 'The Dead Man's Curve' - Vertical Mag
Jun 3, 2021 · The 'dead man's curve' is the height-velocity area where a safe landing after engine failure is not assured, shown in the HV diagram.
[45]
[PDF] nasa tn d-4536 an investigation of the helicopter height-velocity ...
Althoughterrain hasnoaerodynamiceffect on the height-velocity diagram, it is an important factor for the pilot to consider when making an autorotative landing.
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How is the Height-Velocity Diagram Determined?
Mar 4, 2021 · The HV diagram is determined by a trained test pilot, with FAA stipulations, a 1-second delay above the 'knee', and a smooth hard surface for ...Missing: aviation | Show results with:aviation<|separator|>
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Croatian Armed Forces - Vojska.net
Croatian Armed Forces better known as Croatian army (Hrvatska vojska - HV) were formed from National Guard Corps (Zbor narodne garde - ZNG) in 1991. During the ...
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Norway - Heimevernet / Home Guard - GlobalSecurity.org
Nov 15, 2015 · The Home Guard (HV) has undergone comprehensive modernisation and today forms the core of Norway's territorial defence in times of peace, ...
[49]
The Norwegian Home Guard - Forsvaret
Sep 19, 2024 · The Home Guard has 40500 soldiers all over the country. They serve as a quick mobilisation force for the Armed Forces.
[50]
Swedish Military - Hans Högmans släktforskning
The Home Guard was formally established on May 29, 1940, during World War II as a voluntary local defense service.Missing: HV | Show results with:HV
[51]
Sweden - Hemvärnet / Home Guard - GlobalSecurity.org
Dec 21, 2015 · The Home Guard, a force of 100,000 older men, is equipped with assault rifles, submachine guns, and anti-tank weapons.Missing: HV | Show results with:HV<|separator|>
[52]
About us - Hjemmeværnet
Aug 26, 2024 · The Home Guard is part of Denmark's overall readiness in the event of national crises and disasters. The military force consists mainly of volunteer soldiers.
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Home Guard - Hjemmeværnet
The Danish Home Guard. The Danish Home Guard is a volunteer military force tasked with protecting Denmark. Home Guard. The members of the Home Guard take part ...
[54]
Danish Air Force Home Guard puts two new search and surveillance ...
Jan 30, 2025 · Hjemmeværnet, the Danish Home Guard, commissioned two new search and surveillance plane into service. The two Twin Otters, produced by De ...
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What Is A High Velocity Bullet? Why Polymer Ammo Casings ...
A high velocity bullet has a higher muzzle velocity, resulting in a flatter trajectory and less bullet drop over a distance.
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What is a high velocity bullet? | Page 2 | Long Range Hunting Forum
May 10, 2022 · Generally , a centerfire rifle cartridge was called "High-Velocity" when it was capable of a muzzle velocity of 3000 FPS or higher . At that ...
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Muzzle Velocity — Why it's important! - 5D Tactical
Apr 22, 2022 · The definition of muzzle velocity is the speed of a projectile the moment it leaves the barrel after being fired. This is usually measured in ...
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An Introduction to Terminal Ballistics; How Bullets Wound and Kill
Oct 19, 2025 · Terminal ballistics is the study of how a projectile behaves when it hits its target and transfers its kinetic energy to the target.
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High velocity missile wounding using military projectiles - JMVH
This paper discusses high velocity missile wounding caused by military projectiles. For the purpose of this paper, military projectiles considered will be ...
[60]
Do high velocity rounds really have advantage over low ... - Quora
May 3, 2019 · High velocity rounds, specifically rifle ones caused much bigger damage by hydrodynamic shock. If pistol or revolver bullet miss important ...What is the difference between standard velocity and high ... - QuoraWhat bullet has the highest muzzle velocity ever recorded ... - QuoraMore results from www.quora.com
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Bullet Velocity Evolution: The Need for Speed - RifleShooter
May 3, 2021 · Black powder peaked at 1,500 fps. Smokeless powder increased velocity, with .30-40 Krag at 2,200 fps, .220 Swift at 4,140 fps, and a 185-pound ...
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The Best High-Velocity Cartridges You've Never Heard Of - MeatEater
Jan 30, 2025 · The .256 Newton was introduced by the Western Cartridge Co. in 1913, making it the first American-designed, commercially available 6.5mm ...
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Evolution of the M855A1 Enhanced Performance Round - Army.mil
The M855A1 EPR is a significantly improved 5.56mm round that provides excellent soft target consistency and vastly better hard target performance.
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Hypervelocity Projectile (HVP) - BAE Systems
The Hypervelocity Projectile (HVP) is a next-generation, common, low drag, guided projectile capable of executing multiple missions for a number of gun systems.Bae Systems Awarded $2.5... · Bae Systems Teams With Ams... · U.S. Marine Corps Orders...
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FHWA 13-Vehicle Category Classification
Nov 7, 2014 · This category includes motorcycles, motor scooters, mopeds, motor-powered bicycles, and three-wheel motorcycles.
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Truck Classifications: The Definitive Guide to Truck Categories | UTI
Jul 24, 2025 · Classes 7-8: Heavy-duty. Big rigs and other commercial, heavy-duty vehicles are classified starting in this section. Class 7: What is a Class ...
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Denmark - International Transport Forum
(3) EMS (European Modular System) combinations may have a maximum length of 25.25 m and maximum weight of 60 t on a designated road network. (4) For truck in ...
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Compilation of Existing State Truck Size and Weight Limit Laws
These vehicles are limited to a weight of 20,000 lbs. per axle plus scale tolerances, provided that the maximum gross weight does not exceed State limits and ...Missing: global | Show results with:global
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[PDF] Heavy-Duty Vehicle Weight Restrictions in the EU - ACEA
Current EU law (Directive 96/53/EC) limits the maximum permissible vehicle mass to 40 tonnes, except for intermodal transports using 40-foot containers which ...
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Table of Maximum Weights and Dimensions of Heavy Vehicles on...
Jan 31, 2024 · Heavy vehicles with two axles must have a maximum gross weight of 21 tons, with three axles 34 tons, with four axles 45 tons, with five axles 56 tons, and with ...
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49 CFR Part 523 -- Vehicle Classification - eCFR
Class 3 through Class 8 vehicles are vehicles with a gross vehicle weight rating (GVWR) of 10,001 pounds or more as defined in 49 CFR 565.15. Coach bus has the ...
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Transavia airline profile - IATA code HV, ICAO ... - AirHex
Transavia, established in 1965, is a European low-cost airline based in Amsterdam, Netherlands. Its IATA code is HV and ICAO code is TRA.
[74]
Transavia (HV) - Flights, Airline Tickets & Reviews - Kayak
Rating 70% (135) Transavia information. IATA Code, HV. Routes, 294. Top route, Málaga to Amsterdam. Airports served, 98. Top airport, Amsterdam Schiphol. The Transavia logo.
[75]
Transavia Airlines
Rating 3.2 (115) Dec 15, 2023 · General information about Transavia. Low-cost Dutch operator, budget services from Netherlands. IATA code: HV. ICAO code: TRA.
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Transavia Airlines (HV) - Aéroports Voyages
About Transavia Airlines ; IATA Code : HV ; Airline Type : Scheduled, Charter ; Native country : Netherlands ; Founded : 1965 ; Fleet : 43 planes.
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https://www.flightconnections.com/route-map-transavia-hv
[78]
- HV - Airline Code | Transavia Airlines - Seabay Logistics
Airline Name, Transavia Airlines. Prefix. IATA Code, HV. ICAO Code, TRA. Hub City, Amsterdam. Hub Airport, Dallas Fort Worth International Airport.
[79]
Portfolio Companies | HV CAPITAL
HV Entry, Name A-Z, Name Z-A, Founded oldest, Founded latest, HV entry oldest, HV entry latest. Drop Down. 231 Companies. COMPANY. FOUNDED. HV ENTRY. CURRENT ...
[80]
HV Capital: Revenue, Competitors, Alternatives - Growjo
Since 2000, HV Capital, formerly HV Holtzbrinck Ventures, has backed Internet and technology companies through various generations of funds.
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Company Profile - HV TECHNOLOGIES
HV Technologies Company Profile. Offers advanced and economic test equipment including HV equipment, EMC test equipment & service solutions.
[82]
HV Technologies Inc - Company Profile and News - Bloomberg.com
HV Technologies, Inc. operates as a supplier of high voltage and electromagnetic compatibility test equipment. The Company offers high voltage insulation ...
[83]
Harvard College Ventures (HV) - Mignone Center for Career Success
HV is is the largest student-run entrepreneurship and venture capital organization at Harvard. HV serves students at the college interested in startups and ...
[84]
HV Holdings | HOME PAGE
HV Holdings Ltd operates in Mauritius and Madagascar. With more than 3500 employees, the Group is among the Top 100 companies in the Indian Ocean. HV.Our Clusters · Our Team · FR · Group structure
[85]
ISO 3166-1 Change History - Statoids
1984: Name of Upper Volta (codes HV, HVO, 854 ) changed to Burkina Faso. ~1985: Saint Kitts-Nevis-Anguilla (codes KN, KNA, 658 ) split into Anguilla and "Saint ...
[86]
Current and Historical Countries and Areas of Interest
Jul 23, 2018 · current and previous editions of the United Nations Standard Country or Area Codes for Statistical Use. ... HV, HVO, 1970, 1984, Now known as ...
[87]
Classification of country codes - Statistics Norway
Show/hide:HV - Upper Volta; Show/hide:ID - Indonesia; Show/hide:IE - Ireland; Show/hide:IL - Israel; Show/hide:IN - India; Show/hide:IO - British Indian ...
[88]
[PDF] international standard iso 3166 - CIA
This International Standard provides a two-letter and a three-letter alphabetic code for representing the names of countries, dependencies, and other areas of ...
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Country Codes Collection - ISO
It allows you to download the most recent, official lists of country codes and/or subdivisions not to mention formerly used codes in one convenient location.
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Explore the Hudson Valley, NY | Scenic Views & Historic Charm
Discover the Hudson Valley's breathtaking landscapes, historic sites, and farm-to-table experiences in New York.Missing: HV | Show results with:HV
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HV - Hudson Valley | AcronymFinder
How is Hudson Valley abbreviated? HV stands for Hudson Valley. HV is defined as Hudson Valley very frequently.Missing: geography | Show results with:geography<|separator|>
[92]
The Ice Age in the Hudson Valley: A Geographical History
Jan 7, 2021 · Take a journey to the Hudson River region's geologic past when glaciers carved grooves into the landscape we now call home.
[93]
Table C1 - World Meteorological Organization WMO
HV, Burkina Faso, TD, Trinidad and Tobago. HW, Hawaiian Islands ... Eastern Mediterranean area, XX, For use when other designators are not appropriate. Follow WMO ...
[94]
Country Codes - Statoids
Mar 2, 2016 · HV, 42, uv, 226, Yes. Burundi, BI, BDI, 108, BDI ... WMO: Country abbreviations used in weather reports from the World Meteorological Organization ...
[95]
HV Orthopaedic Abbreviation Meaning - All Acronyms
HV in Orthopaedic commonly refers to Hallux Valgus, a condition characterized by the lateral deviation of the big toe, often resulting in a bony bump on the ...
[96]
HV | definition of HV by Medical dictionary
HV. Abbreviation for: haemorrhgic vasculitis half value hallux valgus hantavirus. Health Visitor, see there healthy volunteer hepatic vein hepatitis virusMissing: biology | Show results with:biology
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Medical abbreviations and acronyms (H) | Radiology Reference Article
Sep 15, 2025 · HV: hepatic vein. HVI: hollow viscus injury. HVL: half value layer. Hx: history. HZ: homozygote. Hz: hertz. Incoming Links. Articles: Medical ...Missing: biology | Show results with:biology
[98]
HV Interval - an overview | ScienceDirect Topics
The HV interval represents conduction time from the proximal His bundle to the ventricular myocardium. It is measured from the earliest rapid deflection of the ...Missing: acronym | Show results with:acronym
[99]
Abbreviations | ECG Core Curriculum - AccessMedicine
HV, His-ventricular. IART, intra-atrial reentry tachycardia. ICD, implanted cardiac defibrillator. IST, inappropriate sinus tachycardia. JPC, junctional ...
[100]
Voltage-Gated Proton Channels: Molecular Biology, Physiology, and ...
Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a ...
[101]
Voltage-Gated Proton Channels: Molecular Biology, Physiology, and ...
Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a ...
[102]
HV High Voltage - All Acronyms
High Voltage, abbreviated as HV, refers to electrical systems that operate at a voltage level significantly higher than that of standard power supply systems, ...
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HV - Definition by AcronymFinder
What does HV stand for? ; HV · High-Velocity ; HV, Handelsvertreter (German: sales agent) ; HV · Hudson Valley.Missing: companies | Show results with:companies
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H.V. Definition & Meaning - Dictionary.com
H.V. definition: high velocity.. See examples of H.V. used in a sentence.<|separator|>
[105]
What does HV stand for? - Abbreviations.com
High Voltage · High Value · High Volume · High Velocity · High Viscosity · Heating Value · Hyperventilation · Hudson Valley.