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Springboard
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A springboard or diving board is used for diving and is a board that is itself a spring, i.e. a linear flex-spring, of the cantilever type.
Springboards are commonly fixed by a hinge at one end (so they can be flipped up when not in use), and the other end usually hangs over a swimming pool, with a point midway between the hinge and the end resting on an adjustable fulcrum.
Springboard materials
[edit]Modern springboards are made out of a single-piece extrusion of aircraft-grade aluminum. The Maxiflex Model B, the board used in all major competitive diving events,[1] is made out of such aluminum, and is heat treated for a yield strength of 340,000 kPa (49,000 psi). The slip-resistant surface of the board is created using an epoxy resin, finished with a laminate of flint silica and alumina in between the top coats of resin. This thermal-cured resin is aqua-colored to match the water of a clean pool.[2]
Adjustment of the spring constant
[edit]
The spring constant of a springboard is usually adjusted by way of a fulcrum that is located approximately mid way along the springboard. Springboards are usually operated in a linear regime where they approximately obey Hooke's law. When loaded with a diver, the combination of the diver's approximately constant mass, and the constant stiffness of the spring(board) result in a resonance frequency that is adjustable by way of the spring constant (set by the fulcrum position). Since the resulting system is in an approximately linear regime, it may be modeled fairly accurately by a second order differential equation. Typically the resonance frequency can be adjusted over a range of a 2:1 or 3:1 ratio.[3]
Adjusting the fulcrum
[edit]The fulcrum on competitive diving boards travels over a range of 0.61 metres (24 inches),[4] and is set by way of a foot wheel that is approximately 0.35 m (14 in) in diameter.[3][5][6] To stiffen the spring (as if tightening it), the foot wheel is usually turned counter clockwise. Some may find this counter intuitive, since usually things are tightened by turning clockwise. However, with a little experience, people realize the fulcrum moves in the direction the bottom of the foot faces when placed on the foot wheel.
- Note – Standing behind or in front of the knob, rather than directly above it, will provide better leverage to move the fulcrum. This is accomplished by holding on to the hand rails and leaning the body a few degrees, then placing the foot as low as possible on the knob. In this way, it is possible to move even the most difficult fulcrum.[5]
Heights of springboards
[edit]
Springboards are usually located either 1.0 or 3.0 metres (3 ft 3 in or 9 ft 10 in) above the water surface. It is very seldom that one is mounted at a height other than these two standard heights.
Before around 1960, springboards, usually made of wood, were located at heights of either 3 metres (approximately 10 ft), or 6 metres (approximately 20 ft) above the water. American artist Norman Rockwell's painting titled Boy on High Dive (1947) shows a boy (Rockwel's youngest son, Peter) peering over a typical wooden springboard of the early 20th century era at the 20 feet height.[7]
Home springboards
[edit]After an incident in Washington in 1993, most US and other pool builders are reluctant to equip a residential swimming pool with a diving springboard so home diving pools are much less common these days. In the incident, 14-year-old Shawn Meneely made a "suicide dive" (holding his hands at his sides, so that his head hit the bottom first) in a private swimming pool and was seriously injured and became a tetraplegic. The lawyers for the family, Jan Eric Peterson and Fred Zeder, successfully sued the diving board manufacturer, the pool builder, and the National Spa and Pool Institute (NSPI) over the inappropriate depth of the pool.[8][9] The NSPI had specified a minimum depth of 7 ft 6 in (2.29 m) which proved to be insufficient in the above case. The pool into which Meneely dived was not constructed to the published standards. The standards had changed after the diving board was installed on the non-compliant pool by the homeowner. But the courts held that the pool "was close enough" to the standards to hold NSPI liable. The multimillion-dollar lawsuit was eventually resolved in 2001 for US$6.6 million ($8 million after interest was added) in favor of the plaintiff.[10] The NSPI was held to be liable, and was financially strained by the case. It filed twice for Chapter 11 bankruptcy protection and was successfully reorganized into a new swimming pool industry association.[8]
References
[edit]- ^ Franklin, Woody. "Why a Diving Board Has Holes". About.com. Archived from the original on November 18, 2012. Retrieved June 8, 2012.
- ^ duraflexinternational.com Archived July 27, 2009, at the Wayback Machine
- ^ a b The Physics of Springboard and Platform Diving
- ^ "Sports".
- ^ a b "Diving Fulcrum". Archived from the original on July 7, 2011. Retrieved October 6, 2010.
- ^ Duraflex International/Coach woody Franklyn: diving board construction.
- ^ "Boy On HighDive, Norman Rockwell Saturday Evening Post Cover 1947". Best-Norman-Rockwell-Art.com. Retrieved August 6, 2021.
- ^ a b Brown, AmyJo (January 30, 2004). "No Diving?". Pool & Spa News. Archived from the original on March 4, 2004. Retrieved April 15, 2007.
- ^ "Deep Impact: Back Yard Danger". 60 Minutes II. CBS News. June 2, 1999. Retrieved January 5, 2012.
- ^ Appeals Court State of WA, Docket Number:18036-1-III Title: Shawn Meneely, et al. v. S. R. Smith, Inc., et al.
Springboard
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Definition and Purpose
SpringBoard is the central daemon process in Apple's iOS operating system, implemented as SpringBoard.app, responsible for managing the graphical user interface of the home screen, launching applications, and coordinating system-wide animations. Located at /System/Library/CoreServices/SpringBoard.app, it operates as a LaunchDaemon initiated by the launchd system, running under the "mobile" user account to provide the primary shell for user interactions.[4][5] Its core purposes encompass displaying application icons in a grid-based layout on the home screen, handling user gestures such as taps, swipes, and pinches for navigation and organization, and serving as the entry point for all user-initiated activities on iOS devices. SpringBoard enumerates installed apps from directories like /Applications and renders their icons using data from each app's Info.plist file, while maintaining state through files such as IconState.plist. Additionally, it activates and deactivates UIKit-based applications, managing their memory allocation to ensure smooth transitions and resource efficiency.[4][5] In terms of security, SpringBoard enforces isolation by launching apps within mandatory sandboxes, which restrict access to files, network resources, and hardware to prevent interference between applications or with system data. This integration aligns with iOS's runtime process security model, where each app operates in a unique directory inaccessible to others.[6][4] Compared to Android's third-party launcher applications, SpringBoard is uniquely embedded as a system-level component, enabling optimized performance and a uniform interface without reliance on external customization.[7]Architectural Role in iOS
SpringBoard operates as a user-space process within the iOS operating system, launched automatically by launchd—the system's init daemon with process ID 1—during the boot sequence as part of the graphical user interface initialization.[8] Running under the non-privileged "mobile" user account from its location at/System/Library/CoreServices/SpringBoard.app/SpringBoard, it inherits the bootstrap service port from launchd and registers exception ports to facilitate crash reporting and system stability.[8] This launch mechanism, defined in its plist file at /System/Library/LaunchDaemons/com.apple.SpringBoard.plist, ensures SpringBoard starts with KeepAlive enabled, maintaining continuous operation without a traditional login process in iOS.[8] Upon activation, SpringBoard initializes the UIKit framework to manage user interfaces, app rendering, and event handling, while establishing a connection to WindowServer for core display management, graphics compositing, and window layering.[8] It registers specific Mach services, such as com.apple.UIKit.statusbarserver for status bar operations and com.apple.springboard.UIKit.migserver for UI event processing via the GSEventRun() function, thereby bridging the application layer with underlying graphics subsystems.[8]
In terms of rendering and user interactions, SpringBoard depends heavily on Core Animation—part of the QuartzCore framework—for achieving fluid graphical transitions, animations, and icon-based UI effects across multiple threads.[8] This integration enables seamless visual feedback, such as page flips on the home screen or app icon bounces, by leveraging Core Animation's layer-based compositing model in conjunction with Core Graphics for bitmap rendering.[8] Additionally, SpringBoard interfaces with BackBoardServices, a private framework introduced in iOS 6.0, to handle hardware events including touch gestures, motion detection, power state changes, home button presses, screen locks, and ambient light sensor inputs.[8][9] This communication occurs via XPC APIs and Mach messaging to the backboardd daemon, utilizing ports like PurpleSystemEventPort and com.apple.iohideventsystem for event routing and process suspension/resumption, ensuring responsive device behavior without direct kernel access.[8][9]
SpringBoard plays a central role in upholding iOS's sandboxing model by isolating application launches and restricting access to system resources, thereby mitigating risks from malicious or faulty code.[8][6] It enumerates and launches apps from directories like /Applications and /var/mobile/Applications, confining each to a unique, GUID-named home directory via chroot mechanisms, while enforcing code signing, entitlements, extended attributes, access control lists (ACLs), and the Sandbox.kext kernel extension.[8] Apps are prevented from inter-process communication or resource sharing through process policies—such as PROC_POLICY_BACKGROUND for suspension—and socket shutdowns via pid_shutdown_sockets, all aligned with Mach's security features like the HOST_SEATBELT_PORT.[8] This isolation extends to hiding system apps using SBAppTags in their Info.plist files and assigning priority levels (e.g., 63 for SpringBoard itself, 47 for foreground apps), ensuring that third-party applications operate in read-only OS partitions as the "mobile" user without broader system privileges.[8][6]
