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Disc

DiSC is a commercial behavioral assessment tool designed to categorize individuals' observable styles across four quadrants—Dominance (D), Influence (I), Steadiness (S), and Conscientiousness (C)—through self-reported responses to situational prompts, emphasizing practical applications in communication and team dynamics over deep psychological traits.^[1]^[2] Originating from psychologist William Moulton Marston's 1928 theory linking emotions to interpersonal behaviors, it diverges from his original framework by focusing on self-perception in professional contexts rather than normal vs. abnormal emotional states.^[3]^[4] The model posits that people exhibit blends of these styles, with D types prioritizing results and assertiveness, I types favoring social influence and persuasion, S types emphasizing cooperation and stability, and C types stressing accuracy and compliance, purportedly aiding workplaces in tailoring interactions for better productivity.^[5]^[6] Proponents highlight its accessibility and reported utility in training programs, where millions of assessments have been administered globally since commercial adaptations in the 1950s, often yielding consistent self-categorizations with test-retest reliabilities exceeding 0.80.^[7]^[8] However, its empirical standing is contested, as the foundational theory predates modern personality research like the Big Five model, and studies show limited predictive validity for outcomes such as academic or job performance, with one analysis finding no significant links between DiSC styles and first-year GPA in professional programs.^[9]^[10] Critics argue that while internal consistency is strong in validated versions, broader causal claims lack robust, post-1920s evidence, positioning it more as a heuristic for self-awareness than a scientifically predictive instrument, though commercial providers maintain favorable correlations within their datasets.^[11]^[7]^[12]

Etymology and Usage

Historical Origins and Spelling Variations

The English word disc originates from the Latin discus, denoting a flat, round plate or quoit used in throwing sports, which itself derives from the Ancient Greek δίσκος (dískos), referring to a disc-shaped object such as a platter or athletic implement.^[13]^[14] This Greek term is attested in Homeric epics and classical literature, where it describes objects thrown for distance or used in competitions, with archaeological evidence of stone and later bronze discuses dating to the 8th century BCE in Minoan and Mycenaean contexts.^[15] The discus throw, a core event in the ancient Olympic Games from at least 688 BCE, involved athletes hurling lead- or iron-weighted discs weighing 1.3 to 6.6 kg and measuring 17 to 35 cm in diameter, emphasizing rotational technique for maximum distance.^[16]^[17] The word entered English in the mid-17th century, initially spelled disk to align with native English patterns like whisk or risk, reflecting a phonetic adaptation rather than strict classical fidelity.^[18]^[19] By the 18th century, the Latinate disc variant gained traction, influenced by direct borrowings from French disque and revived classical scholarship during the Renaissance, which prioritized etymological purity over anglicized forms.^[20] Both spellings coexisted, but regional and contextual divergences emerged: British English standardized disc for general circular objects and optical media (e.g., compact discs developed by Philips in the 1970s using European conventions), while American English favored disk for mechanical and magnetic storage technologies pioneered by IBM in the 1950s.^[14]^[21] These preferences persist in style guides, with no semantic distinction but varying frequency in edited prose—disk appearing more in U.S. technical contexts since the 19th-century gramophone era.^[14]^[22]

Mathematics and Geometry

The Mathematical Disk

In geometry, a disk is the set of all points in the Euclidean plane at a distance less than or equal to a fixed radius r from a given center point, forming a closed disk; the open disk excludes the boundary points exactly at distance r.^[23]^[24] The boundary itself constitutes a circle, distinguishing the disk as the filled two-dimensional region rather than the one-dimensional curve.^[23] Disks exhibit key topological and metric properties: a closed disk is compact and convex, while an open disk is an open set in the plane, meaning every point admits a smaller disk neighborhood entirely contained within it./02%3A_Analytic_Functions/2.02%3A_Open_Disks_Open_Deleted_Disks_and_Open_Regions) The area of a disk of radius r is \pi r^2, derived from integration in polar coordinates over the region.^[23] In complex analysis, the open unit disk \{z \in \mathbb{C} : |z| < 1\} is fundamental, modeling domains for holomorphic functions; it supports the Riemann mapping theorem, which asserts that any simply connected domain in the plane (excluding the entire plane) is conformally equivalent to this disk.^[25] Properties like the Schwarz lemma, which bounds holomorphic self-maps of the unit disk, rely on its hyperbolic metric and automorphism group, consisting of Möbius transformations preserving the disk.^[25] Punctured or deleted disks, excluding isolated interior points, arise in studying singularities of analytic functions./02%3A_Analytic_Functions/2.02%3A_Open_Disks_Open_Deleted_Disks_and_Open_Regions) In higher dimensions, the term "disk" generalizes to the n-ball for n \geq 3, but the two-dimensional case retains the specific planar connotation; disks also feature in integral geometry and potential theory for computing volumes and solving boundary value problems.^[23]

Data Storage and Computing

Evolution of Disk Storage Technologies

The first commercial hard disk drive, designated the IBM Model 350, debuted in 1956 as part of the IBM 305 Random Access Method of Accounting and Control (RAMAC) system, featuring 50 rotating aluminum platters coated with magnetic oxide, each 24 inches in diameter, to store approximately 5 megabytes of data across all surfaces.^[26] This innovation marked the shift from sequential-access media like magnetic tape to random-access disk storage, enabling faster data retrieval for business applications, though the unit weighed over a ton and rented for $3,200 monthly.^[27] Early designs relied on vacuum-tube amplifiers and contact read/write heads that physically touched the platter surface, limiting reliability due to wear.^[28] Advancements in the 1960s reduced size and improved access times; the IBM 1301, introduced in 1961, employed aerodynamic slider heads that floated above the platters without contact, boosting storage density to 2.5 megabytes per module using finer-grained magnetic materials.^[26] By 1970, IBM's 3340 "Winchester" drive sealed the heads and platters in a contamination-free enclosure with lubricated surfaces, enhancing reliability and paving the way for non-removable media in fixed installations, with capacities reaching 70 megabytes per spindle.^[27] Concurrently, flexible magnetic disks emerged: IBM's 8-inch floppy disk in 1971 stored 80 kilobytes on a single side, providing removable, low-cost storage for minicomputers and early personal systems.^[28] The 1980s saw disk storage proliferate in personal computing; Seagate's ST-506 in 1980 delivered 5 megabytes in a 5.25-inch form factor, while the 3.5-inch standard by 1984, pioneered by Rodime and adopted by Apple and IBM, fit desktop machines and scaled to hundreds of megabytes by decade's end through thinner platters and zoned bit recording.^[27] Capacity growth accelerated in the 1990s via thin-film heads and magnetoresistive (MR) sensors, which detected smaller magnetic domains; by 1991, drives exceeded 1 gigabyte, and the 1997 introduction of giant magnetoresistive (GMR) heads further quadrupled areal density, enabling terabyte-scale enterprise arrays.^[28] Into the 2000s and beyond, perpendicular magnetic recording (PMR) in 2005 aligned bits vertically for higher density, pushing consumer drives past 1 terabyte by 2009; subsequent innovations like shingled magnetic recording (SMR) in 2013 overlapped tracks for efficiency, and heat-assisted magnetic recording (HAMR) in 2020 prototypes heated platters to stabilize ultra-small bits, targeting 20+ terabytes per drive amid ongoing helium-filled sealing and laser-based writing to counter superparamagnetic limits.^[27] Despite solid-state alternatives, rotating disk technologies persist for cost-effective bulk storage, with annual areal density doublings sustaining petabyte-scale systems in data centers.^[26]

Anatomy and Medicine

The intervertebral disc is an avascular, fibrocartilaginous structure situated between adjacent vertebral bodies in the spinal column, comprising two primary components: the central nucleus pulposus and the peripheral annulus fibrosus. The nucleus pulposus consists of a gel-like matrix rich in proteoglycans and type II collagen, maintaining high water content (up to 88% in youth) that enables hydrostatic pressure resistance to compressive forces. ^[29] The annulus fibrosus forms a multilayered ring of concentrically arranged collagen fibers (type I dominant), providing tensile strength and constraining the nucleus while permitting controlled vertebral motion. ^[29] These discs occupy approximately 25% of the spinal column's length in adults and are thickest in the lumbar region (7-10 mm), thinning cranially. ^[30] Functionally, intervertebral discs facilitate spinal flexibility, distribute axial loads, and absorb shock during dynamic activities such as walking or jumping, with the nucleus generating intradiscal pressure up to 1.5-2 MPa under load to prevent vertebral bony contact. ^[31] Nutrition occurs via diffusion from vertebral endplates due to avascularity, relying on mechanical pumping from cyclic loading to sustain proteoglycan integrity and hydration. ^[29] Discs adapt to forces through viscoelastic properties, exhibiting creep under sustained compression and recovery via fluid imbibition, but chronic overload leads to microstructural fatigue. ^[30] Degenerative disc disease (DDD), characterized by progressive loss of disc height, hydration, and structural integrity, affects an estimated 403 million people globally with symptomatic degeneration (5.5% prevalence), rising sharply with age—disc disease diagnosis reaches 66% in those over 65 versus 2.7 times higher in older versus younger adults overall. ^[32] ^[33] Risk factors include aging (proteoglycan depletion and dehydration), genetic predispositions (e.g., collagen gene variants), mechanical overload from heavy lifting or vibration exposure, smoking (reduces nutrient diffusion), obesity, and diabetes, which accelerate matrix catabolism via inflammatory cytokines like IL-1 and TNF-α. ^[34] ^[35] Symptoms often manifest as chronic low back pain from endplate irritation or instability, though many cases remain asymptomatic; prevalence of diagnosed spinal degeneration is 27.3%, with disc-specific issues contributing to 40% of cases in prospective MRI studies over 5 years. ^[33] ^[34] Lumbar disc herniation, where nucleus material displaces through annular tears (protrusion or extrusion), is the most common related condition, causing radiculopathy in 95% of symptomatic cases via nerve root compression; incidence peaks at 30-50 years, with L4-L5 and L5-S1 levels involved in 90%. ^[36] ^[37] Causes include acute trauma, repetitive microtrauma, or degenerative weakening, leading to symptoms of sciatica (leg pain), numbness, weakness, and rarely cauda equina syndrome (bowel/bladder dysfunction in <1%). ^[36] Over 90% resolve spontaneously within 6-12 weeks via resorption mechanisms involving macrophage-mediated inflammation and neovascularization, though factors like large extrusions (>6 mm) predict slower recovery. ^[38] ^[36] Conservative management is first-line for both DDD and herniation, encompassing activity modification, NSAIDs for inflammation, physical therapy to strengthen core stabilizers, and epidural steroids for radicular pain, yielding 80-90% improvement in 3 months. ^[39] ^[40] Surgery, such as microdiscectomy, is indicated for persistent deficits (e.g., motor weakness >6 weeks) or cauda equina, with success rates of 85-95% for leg pain relief but higher reherniation risk (5-10%) than conservative approaches long-term. ^[36] Emerging evidence questions routine fusion for DDD, favoring motion-preserving options amid debates on overtreatment, as natural history shows frequent regression without intervention. ^[41] ^[40]

Advances in Artificial Disc Replacement

Artificial disc replacement (ADR), also known as total disc arthroplasty, involves surgically implanting prosthetic devices to replace degenerated intervertebral discs, aiming to restore motion and alleviate pain while avoiding the rigidity of spinal fusion. Unlike fusion, which eliminates segmental motion and risks adjacent segment degeneration, ADR seeks to mimic natural disc kinematics through designs typically featuring a mobile core between endplates made of materials like cobalt-chromium alloy, ultra-high-molecular-weight polyethylene (UHMWPE), or titanium.^[42] Early devices faced issues with wear debris and subsidence, but advances have focused on enhancing durability, biocompatibility, and surgical precision.^[43] In the lumbar spine, FDA-approved devices remain limited to activL (Aesculap) and ProDisc-L (Centinel Spine), both cleared via premarket approval pathways demonstrating noninferiority to fusion in randomized controlled trials for single-level degenerative disc disease.^[44] Recent material innovations include next-generation UHMWPE cores with improved wear resistance and titanium alloy endplates coated for osseointegration, reducing subsidence rates observed in earlier metal-on-metal designs.^[45] Meta-analyses of lumbar ADR versus fusion report superior outcomes in Oswestry Disability Index (ODI) scores (mean difference -4.2 points at 2 years) and visual analog scale (VAS) pain reduction, with lower reoperation rates (hazard ratio 0.56) due to preserved motion mitigating adjacent segment stress.^[46]^[47] However, long-term data beyond 7 years show comparable complication profiles, including device migration in 2-5% of cases, underscoring patient selection criteria like preserved facet integrity.^[48] Cervical ADR has seen more rapid evolution, with devices like Mobi-C, Prestige LP, and Simplify approved for two contiguous levels since 2013-2021, expanding indications from single-level radiculopathy or myelopathy.^[49] A pivotal 2025 advancement was the FDA approval on October 14 for two-level implantation of prodisc C Vivo and prodisc C SK, featuring unconstrained ball-and-socket designs that better replicate physiological lordosis and reduce heterotopic ossification compared to constrained semiconstrained models.^[50] Biomaterial enhancements, such as ceramic coatings and vitamin E-stabilized polyethylene, have lowered particulate wear by up to 50% in bench testing, correlating with sustained Neck Disability Index (NDI) improvements (mean 20-point reduction at 5 years) over fusion in meta-analyses.^[51]^[52] These outperform anterior cervical discectomy and fusion (ACDF) in motion preservation (range of motion >3 degrees postoperatively) and adjacent segment disease incidence (relative risk 0.42 at 7 years).^[53] Ongoing research emphasizes hybrid constructs combining ADR with fusion for multilevel disease and minimally invasive approaches using navigation systems for precise endplate preparation, reducing operative time by 20-30% and radiation exposure.^[54] Despite these gains, ADR's broader adoption is tempered by exclusion of patients with osteoporosis or instability, with meta-analytic evidence levels rated moderate due to trial heterogeneity and industry funding biases in some studies.^[55] Future directions include viscoelastic nucleus replacements and 3D-printed customizable implants to address facet-mediated pain, though randomized trials beyond 10 years remain needed for validation.^[56]^[57]

Sports and Recreation

Flying Discs and Disc Sports

Flying discs, lightweight aerodynamic objects typically made of plastic, are thrown for recreational or competitive purposes in disc sports, which emphasize precision, strategy, and athleticism without bodily contact in most variants. The modern flying disc emerged from post-World War II experimentation, with inventor Walter Frederick Morrison developing a molded plastic version in 1948 alongside partner Warren Franscioni, initially marketed as the "Flyin-Saucer" amid public fascination with unidentified flying objects.^[58] By 1955, Morrison refined the design into the "Pluto Platter," which Wham-O Manufacturing Company acquired and rebranded as the Frisbee in 1957, capitalizing on the existing popularity of tossing pie tins from the Frisbie Pie Company bakery, a practice dating back to the early 20th century in Connecticut.^[59] This commercialization propelled flying discs into widespread use, with annual sales reaching millions by the 1960s, evolving from casual play to structured sports.^[60] Disc sports encompass team-based and individual activities governed internationally by the World Flying Disc Federation (WFDF), established in 1985 with 126 member associations across over 120 countries as of 2025, focusing on sanctioning events and standardizing rules.^[61] Ultimate, one of the most popular variants, originated in 1968 when high school students in Maplewood, New Jersey, adapted elements of football, soccer, and basketball into a non-contact game using a flying disc; formal rules were codified in 1970, emphasizing self-officiation via the "spirit of the game" principle to resolve disputes without referees.^[62] Played on a rectangular field with end zones, teams of seven players advance the disc by passing—pivoting in place without traveling—and score by catching in the opponent's end zone; turnovers occur on incomplete passes, interceptions, or out-of-bounds throws, with games typically to 15 points.^[63] The first intercollegiate match occurred on November 6, 1972, between Rutgers and Princeton Universities, where Rutgers prevailed 29-27 in a contest resembling unstructured Frisbee football.^[62] Disc golf, another prominent discipline, simulates traditional golf by throwing discs toward chain-link baskets on courses of 9 or 18 holes, scoring based on the fewest throws needed, with early informal versions appearing in the 1960s using trees or barrels as targets.^[64] Inventor "Steady" Ed Headrick, a former Wham-O executive, standardized the sport in the early 1970s by patenting the Disc Pole Hole—a metal basket catching mechanism—in 1975, which addressed inconsistent targets and enabled precise play; he founded the Professional Disc Golf Association (PDGA) in 1976, growing the sport to over 10,000 courses worldwide by 2025.^[64] Players select from specialized discs varying in weight (typically 150-175 grams), rim width, and flight paths—drivers for distance, mid-ranges for control, and putters for accuracy—adhering to rules prohibiting running while holding the disc and penalizing hazards like out-of-bounds areas.^[65] Additional disc sports include freestyle, involving acrobatic routines with catches and throws judged on difficulty and form; guts, a high-speed precision-passing game across a hip-high net emphasizing rapid volleys; and double disc court, where opponents defend zones against targeted throws.^[61] These activities have expanded globally, with WFDF-sanctioned world championships drawing thousands of competitors; participation surged in the 1970s counterculture era but achieved mainstream traction through organized leagues, underscoring the disc's inherent stability in flight due to its molded rim and flat profile, which enables predictable trajectories governed by aerodynamics rather than propulsion variability.^[66]

Music and Audio

Disc-Based Audio Formats

The Compact Disc Digital Audio (CD-DA), standardized in the Philips-Sony Red Book specification finalized in 1982, marked the first widespread optical disc format for consumer audio, utilizing pulse-code modulation (PCM) at a 44.1 kHz sampling rate and 16-bit depth to achieve approximately 74 minutes of stereo playback on a 120 mm polycarbonate disc read by a 780 nm laser.^[67] Commercial production began with the pressing of Billy Joel's 52nd Street album on August 17, 1982, at a Polygram facility in Germany, followed by market release in Japan that October.^[68] This format displaced analog vinyl and cassette tapes due to its durability, random access capabilities, and immunity to wear from playback, though it faced criticism for introducing digital artifacts like quantization noise absent in analog media.^[69] High-resolution formats emerged in the late 1990s to address CD limitations, with Super Audio CD (SACD) developed by Sony and Philips and introduced in 1999 using Direct Stream Digital (DSD) encoding at a 2.8224 MHz sampling rate and 1-bit depth for multilayer discs supporting up to 120 minutes of stereo or multichannel audio.^[70] SACD discs employ a 650 nm laser for reading a high-density layer beneath a standard CD-compatible layer in hybrid variants, enabling backward compatibility, but adoption remained niche among audiophiles owing to high costs, limited catalog (fewer than 10,000 titles by 2010), and debates over audible benefits beyond CD's Nyquist limit for human hearing around 20 kHz.^[71] DVD-Audio, finalized by the DVD Forum around 1999 for release in 2000, offered PCM or Meridian Lossless Packing (MLP) compression up to 192 kHz/24-bit resolution and 5.1 channels on standard DVD media, yet it achieved minimal market penetration—estimated at under 1% of high-res audio sales—due to format wars with SACD, copy-protection restrictions limiting playback to proprietary players, and the rise of digital downloads.^[72]^[73] Recordable magneto-optical formats like Sony's MiniDisc, launched in 1992, provided portable digital audio storage using 68 mm discs with ATRAC compression for about 74 minutes of near-CD quality, gaining popularity in Japan with over 20 million units sold by 2000 but declining globally after 2000 as writable CD-R drives offered cheaper, uncompressed alternatives and MP3 players eroded demand for physical media.^[74]^[75] Sony ceased MiniDisc player production in 2013 and announced end of media manufacturing in 2025, reflecting obsolescence amid streaming dominance.^[76] In the Blu-ray era post-2005, audio-only discs leverage the format's 25 GB (single-layer) or higher capacity for lossless codecs like Dolby TrueHD or DTS-HD Master Audio, supporting up to 192 kHz/24-bit multichannel content without dedicated "Blu-ray Audio" branding, though releases remain sporadic for classical and surround-sound genres due to preference for video-inclusive Blu-rays and digital alternatives.^[77]^[78] These formats collectively shifted audio from analog grooves to laser-read pits, prioritizing precision and longevity but yielding to non-physical distribution as bandwidth improved.

Psychology and Behavioral Assessment

DISC Personality Assessment Model

The DISC personality assessment model, also known as DiSC, categorizes observable behaviors into four primary styles: Dominance (D), Influence (I), Steadiness (S), and Compliance (C). Developed as a tool for understanding interpersonal dynamics, it posits that individuals exhibit blends of these traits in response to environmental demands, rather than fixed personality types. The model originated from the theoretical work of psychologist William Moulton Marston, who in his 1928 book Emotions of Normal People described how normal emotions drive adaptive behaviors influenced by perceptions of one's environment as favorable or antagonistic and others as hostile or compliant.^[4]^[79] Marston's framework did not initially include a formal assessment instrument; instead, it emphasized four emotional-behavioral factors—Dominance (overcoming opposition), Inducement (influencing others), Submission (cooperating with others), and Compliance (adhering to rules)—as responses to situational pressures. The first practical DISC-based assessments emerged in the mid-20th century, with psychologist Walter Vernon Clarke adapting Marston's ideas into a forced-choice questionnaire in the 1950s to measure these dimensions empirically. Commercial versions proliferated from the 1970s onward, often through publishers like Inscape Publishing (now Wiley), focusing on self-reported profiles for practical application rather than deep psychological diagnosis.^[80]^[4] The four factors are defined as follows: Dominance involves direct, decisive, and results-oriented behaviors, often seen in competitive or challenging settings; Influence encompasses sociable, persuasive, and enthusiastic interactions aimed at building relationships; Steadiness reflects patient, supportive, and team-focused tendencies, prioritizing harmony; Compliance (or Conscientiousness) emphasizes accuracy, rule-following, and analytical caution to ensure quality and compliance with standards. Assessments typically yield a profile graph showing relative strengths across these factors, with 12 possible blends (e.g., DI, IS) derived from combinations, though individuals score on a continuum rather than discrete categories.^[5]^[81] Primarily applied in organizational contexts, DISC tools support team building, conflict resolution, sales training, and leadership development by highlighting communication preferences and potential blind spots. For instance, high-D individuals may be coached to temper assertiveness for better collaboration, while high-C profiles might focus on flexibility. Usage spans corporations, with millions of assessments administered annually, but it is not endorsed for high-stakes decisions like clinical diagnosis or unaided hiring due to limitations in predictive power.^[82] Psychometric evaluation reveals moderate test-retest reliability, with coefficients often exceeding 0.80 for factor scores over short intervals, indicating consistency in self-perceptions. However, convergent validity with established models like the Big Five is partial at best, and predictive validity for job performance remains weakly supported by independent research. Proprietary validity reports from providers claim correlations with outcomes like sales success, but peer-reviewed studies are sparse and do not robustly confirm causal links between DISC profiles and behavioral predictions beyond descriptive utility.^[83]^[11] Critics, including psychologists, argue the model oversimplifies human behavior into quadrants lacking empirical grounding, akin to typologies dismissed in mainstream personality science for ignoring trait continua and contextual variability. Claims of pseudoscientific elements arise from its divergence from factor-analytic traditions, with insufficient evidence tying Marston's emotional theory to measurable outcomes; for example, no large-scale, replicated studies validate DISC's incremental utility over simpler behavioral observations. Commercial interests may inflate reported validities, as independent scrutiny highlights risks of stereotyping or confirmation bias in applications, underscoring its role as a heuristic rather than a rigorous diagnostic instrument.^[84]^[85]^[11]

Other Technical and Scientific Uses

Disc Brakes in Automotive Engineering

Disc brakes in automotive engineering utilize a rotating metal disc, or rotor, attached to the wheel hub, against which brake pads are pressed by a caliper to generate friction and decelerate the vehicle. This system operates on hydraulic principles, where pressure from the brake pedal activates a master cylinder to force fluid through lines to the calipers, clamping the pads onto the disc. Unlike drum brakes, which enclose components in a drum, disc brakes expose the rotor to air for enhanced cooling, reducing thermal buildup during prolonged use.^[86]^[87] The invention of the caliper-type disc brake is attributed to English engineer Frederick William Lanchester, who patented it in 1902 for use on Lanchester automobiles produced in Birmingham. Early adoption was limited, with drum brakes dominating due to simplicity and cost, but disc brakes gained traction in racing; the Jaguar C-Type employed them in 1953 for improved performance at Le Mans, followed by the Citroën DS in 1955 for production cars. Widespread implementation occurred in the 1960s, with front disc brakes becoming standard on many U.S. models by the early 1970s, driven by demands for better stopping power amid rising vehicle speeds and weights.^[86]^[88]^[89] Key components include the brake rotor, typically cast iron or steel, which rotates with the wheel and withstands frictional heat; the caliper, housing pistons that push pads via hydraulic force; friction pads made of semi-metallic or ceramic composites for grip and durability; and support hardware such as clips and shims to maintain alignment and reduce noise. The system integrates with the master cylinder and fluid reservoir for pressure modulation, often incorporating anti-lock braking sensors in modern setups. Ventilated rotors, featuring internal vanes for airflow, emerged in the mid-20th century to further mitigate fade.^[90]^[91]^[92] During operation, pedal application transmits force hydraulically to the caliper pistons, which extend to clamp pads against the rotor, converting kinetic energy to heat via friction; release allows retraction springs or seals to pull pads away, preventing drag. This clamping action provides linear response and consistent torque, with stopping distances 17-33% shorter than drum brakes at typical highway speeds due to efficient force application and minimal expansion under heat.^[93]^[94] Disc brakes outperform drum systems in heat dissipation—exposed rotors cool 20-30% faster, minimizing fade during repeated stops—and resist water-induced loss of efficacy, as rotation sheds moisture. They require less maintenance, with self-adjusting calipers and easier pad replacement, yielding lower long-term costs despite higher initial expense. Drawbacks include greater susceptibility to warping from uneven heating and higher noise from pad material, though mitigated in ventilated designs. In high-performance vehicles, carbon-ceramic discs, introduced commercially in the late 1990s, offer extreme durability under loads exceeding 1,000°C, as seen in Ferrari models from 1999 onward.^[95]^[96]^[97]

Astronomical and Natural Discs

In astronomy, discs refer to flattened, rotating structures of gas, dust, or stars formed by conservation of angular momentum during gravitational collapse or accretion processes. These structures are ubiquitous in the universe, ranging from circumstellar environments around individual stars to large-scale galactic components. Protoplanetary discs, for instance, surround young stars and serve as the birthplaces of planetary systems, consisting primarily of dense gas and dust that persists for several million years while material accretes onto the central star or coalesces into planetesimals.^[98]^[99] Accretion discs form when diffuse material orbits a massive central object, such as a black hole or neutron star, spiraling inward due to viscosity and friction, which heats the disc and generates intense radiation across X-ray to infrared wavelengths. These discs are geometrically thin and optically thick, with their inner regions reaching temperatures exceeding 10^7 K, enabling observations of phenomena like quasars and X-ray binaries. Debris discs, by contrast, represent later evolutionary stages, comprising dust and planetesimal remnants around mature stars, often sculpted by unseen planets that clear gaps or confine the material, as inferred from infrared excesses detected by telescopes like Spitzer and ALMA.^[100]^[101] Galactic discs characterize spiral and lenticular galaxies, forming thin, exponential distributions of stars, gas, and dust in near-circular orbits around a central bulge or bar, with typical scale heights of 300-500 parsecs and radial extents spanning tens of kiloparsecs. The Milky Way's disc, for example, rotates differentially with velocities around 220 km/s at the Sun's position, 8 kpc from the center, and its structure evolves through internal dynamical processes like density waves and mergers, rather than monotonic growth.^[102] On Earth, natural disc-like formations arise from fluid dynamics and thermal gradients, such as ice discs in rivers, which develop in cold climates where eddy currents create rotating vortices that freeze surface water into large, flat pans up to 100 meters in diameter. These phenomena, observed in locations like the Kennebec River in Maine on January 15, 2019, result from differential cooling where water at 4°C sinks, sustaining the spin and eroding edges into circular shapes. Similar hydrodynamic principles underpin lenticular clouds, stationary disc-shaped formations over mountains caused by stable atmospheric layers and wind shear, mimicking some astronomical disc stability but on vastly smaller scales.^[103]^[104]

References

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DiSC® is a scientifically validated personality assessment tool that identifies behavioral insights to improve communication and productivity in the ...The DiSC Styles · How DiSC works · History of DiSC · Everything DiSC Workplace
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What Is the Everything DiSC® Model?
Everything DiSC is a personal development learning experience that measures an individual's preferences and tendencies based on the DiSC model.
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DISC is a behaviour self-assessment tool originally based on the 1928 DISC emotional and behavioural theory of psychologist William Moulton Marston.
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The DISC Model of Behavior was first proposed in 1928 by William Moulton Marston, a physiological psychologist, in his book Emotions of Normal People. Marston ...
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May 24, 2021 · DiSC® is an acronym that stands for Dominance, Influence, Steadiness, and Conscientiousness. These four behavioral styles are used to understand ...<|separator|>
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DISC is a personality model based on four dimensions, i.e. Dominance, Influence, Steadiness and Compliance. Read more about the DISC typology.
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Disk, from Latin origin, means a flat, round object; British English prefers Latinate spelling, while American English uses it mainly for musical recordings ...
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To start from the beginning: the word derives from the Latin noun discus, which means “quoit, disk, dish.” The Greeks spelled this word as diskos, deriving it ...
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Originating from Greek diskos and Latin discus, meaning a round stone or metal plate thrown for sport, reflecting the act "to throw" or "direct an object."
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discus thrower - Ancient Olympics
Originally the discus was made of stone, later of bronze, lead or iron. Excavated examples have a diameter of 17 to 35 cm and a weight of 1,3 to 6,6 kg.<|control11|><|separator|>
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Ancient Olympic Sports - running, long jump, discus, pankration
The discus was originally made of stone and later of iron, lead or bronze. The technique was very similar to today's freestyle discus throw. Wooden, the height ...
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Jan 2, 2024 · The oldest known references to the English version, dating back to the mid-17th century, are spelled disk.
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A disk is the shadow of a ball on a plane perpendicular to the ball-radiant point line. The n -disk for n>=3 is called a ball, and the boundary of the n -disk ...
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Disk Definition (Illustrated Mathematics Dictionary) - Math is Fun
Illustrated definition of Disk: The region inside a circle. Correctly speaking, a circle is just the boundary: the set of all points a fixed distance...
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Unit Disk -- from Wolfram MathWorld
The (open) unit disk can also be considered to be the region in the complex plane defined by {z:|z|<1}, where |z| denotes the complex modulus. (The closed unit
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Memory & Storage | Timeline of Computer History
In 1953, MIT's Whirlwind becomes the first computer to use magnetic core memory. Core memory is made up of tiny “donuts” made of magnetic material strung on ...
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A History of the Hard Disk Drives (HDD) From the Beginning to Today
Nov 17, 2016 · 2016 marks the 60th anniversary of the hard drive. Let's look back at how the tech has changed over the years.
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Hard Drive Technology Timeline - Datarecovery.com
Jun 23, 2014 · Hard Drive Technology Timeline · 1956 – The First Commercial Hard Drive · 1961 – The First Air-Bearing Read/Write Heads · 1965 – The Removable Disk ...1965 -- The Removable Disk... · 1970 -- The Floppy Disk · 1986 -- The Introduction Of...<|separator|>
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Anatomy, Back, Intervertebral Discs - StatPearls - NCBI Bookshelf
They provide separation and connectivity between vertebrae and counteract forces that act to lengthen or compress the spine or affect it in a torsional or ...Introduction · Structure and Function · Embryology · Clinical Significance
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Human intervertebral disc: structure and function - PubMed
The fluid space is important in the nutrition of the disc, showing plastic deformation and recovery characteristics. The structural elements, both ...
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Intervertebral disk: MedlinePlus Medical Encyclopedia Image
Aug 27, 2024 · The intervertebral disks allow the vertebral column to be flexible and act as shock absorbers during everyday activities such as walking, running and jumping.
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Lumbar disc herniation: Epidemiology, clinical and radiologic ...
Approximately 403 million people (5.5% of the worldwide population) are estimated to have symptomatic disc degeneration. The SPORT trial (Spine Patients Outcome ...
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Prevalence of spine degeneration diagnosis by type, age, gender ...
Mar 8, 2021 · Increasing age has been specifically associated with increased spine curvature, stenosis, endplate sclerosis, disc degeneration, osteophyte ...
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Risk factors for lumbar disc degeneration: a 5-year prospective MRI ...
Results: Of the 41 individuals, 17 (41%) exhibited a deterioration of the disc status. In 10 individuals, the progression of disc degeneration was one grade or ...Missing: prevalence | Show results with:prevalence
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Risk Factors of Intervertebral Disc Pathology—A Point of ... - MDPI
Obesity, occupation, smoking status, diabetes, and alcohol consumption were described as aggravating factors. Hence, disc degeneration appears to be a ...<|separator|>
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Disk Herniation - StatPearls - NCBI Bookshelf - NIH
Sep 14, 2025 · Most herniated disks improve with conservative treatment, but refractory cases may require interventional or surgical repair. Epidural ...
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Lumbar Disc Herniation - Spine - Orthobullets
Sep 14, 2025 · Lumbar Disc Herniation is a very common cause of low back pain and unilateral leg pain, known as radiculopathy. In rare cases a large disc ...<|separator|>
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Characteristics and mechanisms of resorption in lumbar disc ...
Aug 23, 2022 · The conventional course of treatment is at least 6 weeks, and the main forms include bed rest, drug therapy, exercise therapy, epidural ...
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Herniated Disk in the Lower Back - OrthoInfo - AAOS
Although a herniated disk can be very painful, most people feel much better with just a few weeks or months of nonsurgical treatment.
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Management of Lumbar Disc Herniation: A Systematic Review - NIH
Oct 29, 2023 · Herniated discs can cause pain, tingling, numbness, diminished feeling, weakening, and instability. The most frequent disc in the cervical ...
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Emerging Issues Questioning the Current Treatment Strategies for ...
Mar 27, 2022 · Patients with isolated herniated lumbar discs causing radiculopathy are recommended to undergo the primary disc excision operation, such as open ...
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2021 Position Statement From the International Society for the ... - NIH
Currently, the activL Artificial disc (Aesculap Implant Systems) and the Prodisc-L (Centinel Spine) are the only 2 commercially available FDA-approved devices.
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The Artificial Disc Nucleus and Other Strategies for Replacement of ...
One of the common approaches used in the development of NP replacement devices is the design of solid prosthetic implants from materials such as stainless-steel ...
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[PDF] Artificial Disc Replacement Surgery
Jan 17, 2025 · Those FDA approved for the lumbar spine include, but may not be limited to: activL artificial disc and. ProDisc-L total disc replacement (see ...
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(2025 Update): Market, Leading FDA-Approved Devices, Material ...
Jun 29, 2025 · To date, the U.S. Food and Drug Administration (FDA) has approved only three lumbar total disc replacement devices. Several other lumbar discs ...
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Total disc replacement versus fusion for lumbar degenerative diseases
This systematic review and meta-analysis suggests that total disc replacement surgery, compared to lumbar fusion surgery, significantly improved ODI, VAS, SF- ...
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Lumbar Disc Replacement Versus Interbody Fusion: Meta-analysis ...
Apr 29, 2024 · This meta-analysis aims to compare the outcomes of lumbar disc replacement (LDR) versus interbody fusion (IBF), assessing their comparative ...
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A meta-analysis of artificial total disc replacement versus fusion for ...
It reveals that TDR results in a slightly better function and less back or leg pain in the lumbar DDD patients without clinical significance and a significantly ...
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Jul 31, 2024 · The PRESTIGE® LP, Simplify® Cervical Disc, and MOBI-C® have received FDA approval for implantation at two contiguous cervical levels. Available ...
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Oct 14, 2025 · Centinel Spine® Receives Two-Level FDA Approval for prodisc® C Vivo and prodisc® C SK Match-the-Disc™ Cervical Total Disc Replacement Devices.
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Jun 13, 2025 · Modern artificial discs incorporate advanced materials science, featuring next-generation polyethylene, titanium alloys, and ceramic ...
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Clinical Effectiveness of Artificial Disc Replacement in Comparison ...
Sep 30, 2023 · A meta-analysis showed better clinical outcomes with or without statistical significance. The level of evidence was low because of ...
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a systematic review and meta-analysis of randomized controlled trials
Aug 12, 2025 · Our aim was to evaluate long-term effectiveness and safety of cervical disc arthroplasty (CDA) compared to anterior cervical discectomy and ...
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Uphill battle: The future of disc replacement - Healio
Feb 15, 2024 · Cervical and lumbar disc replacement have shown promising results compared with spinal fusion for the treatment of neck and lower back conditions.
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Clinical Effectiveness of Artificial Disc Replacement in Comparison ...
Sep 30, 2023 · This meta-analysis showed that ADR achieved compatible or better functional outcomes in terms of NDI and JOA in the treatment of CM from 3- to ...
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Mar 14, 2025 · Spinal implants are evolving rapidly with AI, 3D printing, and motion-preserving technology transforming spine care in 2025.
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The Future of Arthroplasty in the Spine
Mar 20, 2025 · Cervical disc arthroplasty and lumbar disc arthroplasty are effective alternatives to fusion, particularly in preserving motion and reducing ...
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Toy company Wham-O produces first Frisbees | January 23, 1957
In 1948, Walter Frederick Morrison and his partner Warren Franscioni invented a plastic version of the disc called the “Flying Saucer” that could fly further ...
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An American Toy Company Produced the World's First Frisbees ...
Jan 23, 2025 · When Wham-O Manufacturing Co. rolled out its first flying discs on January 23, 1957, there must have been some speculation: Would the idea fly with consumers?
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WFDF | World Flying Disc Federation
Formed in 1985, WFDF is a federation of 126 member associations, which represent flying disc sports and their athletes in more than 122 countries. WFDF is an ...About WFDF · Disc Golf World Rankings · WFDF 2025 World Under-24... · Disc Golf
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History of Ultimate - WFDF
The first college ultimate game was played between Rutgers and Princeton on November 6, 1972. Rutgers won the game 29-27.
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Official Rules of Ultimate
1.A. Description: Ultimate is a non-contact, self-officiated disc sport played by two teams of seven players. The object of the game is to score goals. A goal ...
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Brief History of Disc Golf and the PDGA
“Steady” Ed Headrick #001 is considered the Father of Disc Golf. Of his dozens of patented inventions, two of them hold infinite importance to our sport.
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Disc Golf History
Oct 30, 2001 · Modern day disc golf started in the late 60's. The early frisbee golf courses were “object courses”, using anything from trees, trash cans, ...
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About WFDF
The World Flying Disc Federation (WFDF) is the international sports federation responsible for world governance of flying disc (frisbee) sports.
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Mar 6, 2024 · Developed jointly by Philips and Sony, the CD format was finalized in 1982 and famously documented in the Red Book standard.Missing: date | Show results with:date
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Aug 17, 2025 · On August 17, 1982, engineers at a Polygram factory in Langenhagen, Germany, pressed the first commercial compact disc, containing the Swedish ...
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[PDF] The Invention of Compact Discs - Dartmouth
Nov 9, 2012 · In 1982 Sony and Philips introduced the world's first CD system – a 12-cm compact audio disc and a CD player – which quickly displaced the ...
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SACD | Reference Recordings®
Super Audio CD (SACD) is a high-resolution, read-only optical audio disc format developed by Sony and Philips Electronics, the same companies that created ...Missing: adoption | Show results with:adoption
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Sep 12, 2007 · It promised far better sound quality than standard CDs, surround sound capability, and best of all, the Hybrid SACD could also play in standard ...
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DVD Audio - How DVDs Work - Electronics | HowStuffWorks
DVD audio uses a 192kHz/24-bit DAC, offering better sound quality than CDs (441kHz/16-bit). It can hold up to two hours of 96kHz/24-bit music.Missing: history market<|separator|>
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Market Gears up for DVD Audio - ABC News
Nov 24, 2000 · Holding about 74 minutes worth of audio, sampled at 44.1 kilohertz, the CD has taken over the consumer music market, virtually leaving analog ...Missing: history | Show results with:history
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The Sony MiniDisc
The MD format is clearly not a fad and will stay for years to come - in 1997, 6.3 million MDs were sold worldwide and it is expected to reach 22.9 million by ...
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The Rise and Fall of the Sony MiniDisc: Why It Failed
Jan 14, 2025 · They were cheaper, faster, and more versatile, allowing users to make their own mix CDs with more storage and less hassle. Blank CDs were also ...
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Feb 4, 2013 · After upwards of two decades, the MiniDisc is finally on the way out: The BBC reports that Sony plans to ship its final MiniDisc stereo system in March.
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Blu-ray Player Soundtrack Options - Blog - Axiom Audio
The three lossless audio formats associated with Blu-ray players' high-resolution audio soundtracks are Dolby TrueHD, DTS-HD Master Audio (MA) and Linear PCM.
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Blu-ray Audio Explained - Don Lindich's Sound Advice Blog
Dolby TrueHD: This format uses lossless compression so the audio information takes up less space on the disc than a PCM file, but no sound quality is lost in ...
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The Emotions of Normal People by William Moulton Marston
The factors he studied were Dominance, Influence, Steadiness and Compliance, from which the theory takes its name – DISC. Marston discovered that people do ...
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Learn DiSC's history and see how it evolved with the DiSC Timeline
Did you know DiSC theory was created in 1928, but the first assessment wasn't created until the 1970s? Learn DiSC's history on our DiSC timeline.The Emotions Of Normal... · Walter Clarke And The... · 2007 To Today: Everything...
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The 4 DISC Personality Types (Plus 12 Styles with Careers) - Indeed
Oct 2, 2025 · DISC is an acronym that stands for the four main behavioral styles outlined in the DISC model of personalities: Dominance, Influence, Steadiness ...
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The Complete Guide to DISC Personality Testing | Thomas.co
The DISC assessment divides the test-taker's personality up into four weights as mentioned above: Dominance, Influence, Steadiness, and Compliance (or ...
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[PDF] Research Report - Everything Disc
Evaluation of the Everything DiSC® assessment indicates that there is strong support for the reliability and validity of this tool. Analyses suggest that ...
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Personality Assessments: Separating Science From Nonsense
Nov 18, 2022 · While the assessment of personality is becoming increasingly important in job recruiting, many denounce its limitations and dangers.
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Personality Tests Used For Hiring Are Bogus Pseudoscience
Oct 23, 2020 · There is no evidence that DISC results accurately measure personality. Even DISCprofile.com says that DISC is “not recommended for pre- ...
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The history of braking systems in automotive industry - ABE
The first disc brake was invented in 1902 by Frederic Wilhelm Lanchester, an English engineer, while the drum brake was patented by Louis Renault the same year.
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DISC BRAKE SYSTEM OF THE CAR - Asahiparts
Aug 9, 2024 · When you step on the brake, the hydraulic force presses the brake pads against the brake disc and creates friction to stop your car. That is ...
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The history of disc brakes - Classics World
Dec 18, 2018 · We trace the development of this important automotive innovation back to the opening years of the Twentieth century.
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Braking System and the History of it - Brausen Auto
Oct 29, 2020 · Disc brakes were invented in 1902 by William Lanchester. They didn't become widely used until the mid-20th century, when they were implemented ...
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What is a Disc Brake System? Learn the Parts & Components
When it comes to disc braking systems, there are four parts you need to know: The pads, rotors, calipers, and hardware.
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Disc Brakes｜Brakes for Automobiles｜Product
Disc brake construction The brake rotor (disc) which rotates with the wheel, is clamped by brake pads (friction material) fitted to the caliper from both sides ...
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What are the Four major Parts of a Disc Brake System
These parts include brake pad, brake rotor, brake calipers, and calipers support. In fact, none of the components can work without others.
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Jun 30, 2020 · How the disc brake work ? Disc brakes use the clamping method for braking. We know that the brake system works because there is friction.
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https://www.fourwindstrailers.com/blog/disc-vs-drum-brakes/
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What are the advantages of disc brakes over drum brakes?
Disc brakes have fewer moving parts, longer life, self-adjusting calipers, are less sensitive to contamination, and have lower owning costs.
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What are the Advantages of Disc Brakes? - Dexter Group
Sep 11, 2023 · Disc brakes offer a lower ownership cost due to their extended lifespan, reduced maintenance requirements, and enhanced performance.
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Drum Brakes vs. Disc Brakes: What's the Difference?
Jun 29, 2023 · Improved Stopping Distance – With disc brakes, stopping distance can be 17–33% shorter than drum brakes, depending on the speed of the vehicle.
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Disks | Center for Astrophysics | Harvard & Smithsonian
Disks are formed by rapid rotation, include protoplanetary disks around stars and accretion disks around compact objects like black holes, and are important ...
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Protoplanetary Disks and Their Evolution - ADS
These disks generally persist for several million years, during which time some material accretes onto the star, some is lost through outflows and ...
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Jan 18, 2022 · These notes introduce and review some of the physical principles underlying the theory of astrophysical accretion.
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Debris Disks: What Can We Learn from the Leftovers of the Planet ...
Jun 11, 2021 · A debris disk can be used as a “planet detector”. The disk's location around a star can tell us about possible planets in the system.Missing: discs | Show results with:discs
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Galactic Disks - Max-Planck-Institut für Astronomie
The shape of the stellar velocity ellipsoid (SVE) in galactic disks, i.e. the balance between the vertical and radial velocity dispersions, keeps the record of ...
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Massive spinning ice disc forms in US river - BBC
Jan 16, 2019 · Researchers believe ice discs spin because of temperature changes in the water, creating a vortex underneath. The movement chips away the edges, ...
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Understand the Physics Behind These Incredible Ice Discs
Jun 21, 2025 · When the disc melts, it begins to cool the surrounding water. When that water reaches 4 degrees Celsius, it sinks and creates a vortex which ...