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Topic Review
Altitude (Triangle)
In geometry, an altitude of a triangle is a line segment through a vertex and perpendicular to (i.e., forming a right angle with) a line containing the base (the side opposite the vertex). This line containing the opposite side is called the extended base of the altitude. The intersection of the extended base and the altitude is called the foot of the altitude. The length of the altitude, often simply called "the altitude", is the distance between the extended base and the vertex. The process of drawing the altitude from the vertex to the foot is known as dropping the altitude at that vertex. It is a special case of orthogonal projection. Altitudes can be used in the computation of the area of a triangle: one half of the product of an altitude's length and its base's length equals the triangle's area. Thus, the longest altitude is perpendicular to the shortest side of the triangle. The altitudes are also related to the sides of the triangle through the trigonometric functions. In an isosceles triangle (a triangle with two congruent sides), the altitude having the incongruent side as its base will have the midpoint of that side as its foot. Also the altitude having the incongruent side as its base will be the angle bisector of the vertex angle. It is common to mark the altitude with the letter h (as in height), often subscripted with the name of the side the altitude is drawn to. In a right triangle, the altitude drawn to the hypotenuse c divides the hypotenuse into two segments of lengths p and q. If we denote the length of the altitude by hc, we then have the relation For acute and right triangles the feet of the altitudes all fall on the triangle's sides (not extended). In an obtuse triangle (one with an obtuse angle), the foot of the altitude to the obtuse-angled vertex falls in the interior of the opposite side, but the feet of the altitudes to the acute-angled vertices fall on the opposite extended side, exterior to the triangle. This is illustrated in the adjacent diagram: in this obtuse triangle, an altitude dropped perpendicularly from the top vertex, which has an acute angle, intersects the extended horizontal side outside the triangle.
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Topic Review
Juniper M Series
Juniper M series is a line of multiservice edge routers designed and manufactured by Juniper Networks, for enterprise and service provider networks. It spans over M7i, M10i, M40e, M120, and M320 platforms with 5 Gbit/s up to 160 Gbit/s of full-duplex throughput. The M40 router was the first product by Juniper Networks, which was released in 1998. The M-series routers run on JUNOS Operating System.
  • 447
  • 25 Oct 2022
Topic Review
Censorship of YouTube
The video-sharing platform YouTube is the second-most popular website as of August 2019, according to Alexa Internet. According to the company's press page, YouTube has more than one billion users, and each day, those users watch more than one billion hours of video. Censorship of it has occurred and continues to occur to varying degrees in most countries throughout the world.
  • 805
  • 25 Oct 2022
Topic Review
AlphaServer
AlphaServer is a series of server computers, produced from 1994 onwards by Digital Equipment Corporation, and later by Compaq and HP. AlphaServers were based on the DEC Alpha 64-bit microprocessor. Supported operating systems for AlphaServers are Tru64 UNIX (formerly Digital UNIX), OpenVMS, MEDITECH MAGIC and Windows NT (on earlier systems, with AlphaBIOS ARC firmware), while enthusiasts have provided alternative operating systems such as Linux, NetBSD, OpenBSD and FreeBSD. The Alpha processor was also used in a line of workstations, AlphaStation. Some AlphaServer models were rebadged in white enclosures as Digital Servers for the Windows NT server market. These so-called "white box" models comprised the following: As part of the roadmap to phase out Alpha-, MIPS- and PA-RISC-based systems in favor of Itanium-based systems at HP, the most recent AlphaServer systems reached their end of general availability on 27 April 2007. The availability of upgrades and options was discontinued on 25 April 2008, approximately one year after the systems were discontinued. Support for the most recent AlphaServer systems, the DS15A, DS25, ES45, ES47, ES80 and GS1280 is being provided by HP Services as of 2008. These systems are scheduled to reach end of support sometime during 2012, although HP has stated that this event may be delayed.
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  • 25 Oct 2022
Topic Review
Dance Dance Revolution S
Dance Dance Revolution S (ダンスダンスレボリューションS, Dansu Dansu Reboryūshon Esu), commonly abbreviated as DDR S, is a rhythm game by Konami available for the iOS, as part of the company's Dance Dance Revolution series of music video games. Announced by Konami in January 2009, the game was made available via Apple's App Store in Japan on February 27, 2009. It was later made available in the United States and Europe on March 5, 2009 and May 14, 2009 respectively. While gameplay is very similar to other Dance Dance Revolution titles, a new mode dubbed "Shake Mode" is available in which players are able to shake their device in certain directions to the rhythm of the music.
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  • 25 Oct 2022
Topic Review
Limit Point
In mathematics, a limit point (or cluster point or accumulation point) of a set [math]\displaystyle{ S }[/math] in a topological space [math]\displaystyle{ X }[/math] is a point [math]\displaystyle{ x }[/math] that can be "approximated" by points of [math]\displaystyle{ S }[/math] in the sense that every neighbourhood of [math]\displaystyle{ x }[/math] with respect to the topology on [math]\displaystyle{ X }[/math] also contains a point of [math]\displaystyle{ S }[/math] other than [math]\displaystyle{ x }[/math] itself. A limit point of a set [math]\displaystyle{ S }[/math] does not itself have to be an element of [math]\displaystyle{ S. }[/math] There is also a closely related concept for sequences. A cluster point or accumulation point of a sequence [math]\displaystyle{ (x_n)_{n \in \mathbb{N}} }[/math] in a topological space [math]\displaystyle{ X }[/math] is a point [math]\displaystyle{ x }[/math] such that, for every neighbourhood [math]\displaystyle{ V }[/math] of [math]\displaystyle{ x, }[/math] there are infinitely many natural numbers [math]\displaystyle{ n }[/math] such that [math]\displaystyle{ x_n \in V. }[/math] This definition of a cluster or accumulation point of a sequence generalizes to nets and filters. In contrast to sets, for a sequence, net, or filter, the term "limit point" is not synonymous with a "cluster/accumulation point"; by definition, the similarly named notion of a limit point of a filter (respectively, a limit point of a sequence, a limit point of a net) refers to a point that the filter converges to (respectively, the sequence converges to, the net converges to). The limit points of a set should not be confused with adherent points for which every neighbourhood of [math]\displaystyle{ x }[/math] contains a point of [math]\displaystyle{ S }[/math]. Unlike for limit points, this point of [math]\displaystyle{ S }[/math] may be [math]\displaystyle{ x }[/math] itself. A limit point can be characterized as an adherent point that is not an isolated point. Limit points of a set should also not be confused with boundary points. For example, [math]\displaystyle{ 0 }[/math] is a boundary point (but not a limit point) of set [math]\displaystyle{ \{ 0 \} }[/math] in [math]\displaystyle{ \R }[/math] with standard topology. However, [math]\displaystyle{ 0.5 }[/math] is a limit point (though not a boundary point) of interval [math]\displaystyle{ [0, 1] }[/math] in [math]\displaystyle{ \R }[/math] with standard topology (for a less trivial example of a limit point, see the first caption). This concept profitably generalizes the notion of a limit and is the underpinning of concepts such as closed set and topological closure. Indeed, a set is closed if and only if it contains all of its limit points, and the topological closure operation can be thought of as an operation that enriches a set by uniting it with its limit points.
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Topic Review
ID-Based Encryption
ID-based encryption, or identity-based encryption (IBE), is an important primitive of ID-based cryptography. As such it is a type of public-key encryption in which the public key of a user is some unique information about the identity of the user (e.g. a user's email address). This means that a sender who has access to the public parameters of the system can encrypt a message using e.g. the text-value of the receiver's name or email address as a key. The receiver obtains its decryption key from a central authority, which needs to be trusted as it generates secret keys for every user. ID-based encryption was proposed by Adi Shamir in 1984. He was however only able to give an instantiation of identity-based signatures. Identity-based encryption remained an open problem for many years. The pairing-based Boneh–Franklin scheme and Cocks's encryption scheme based on quadratic residues both solved the IBE problem in 2001.
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  • 25 Oct 2022
Topic Review
Setspn
Kerberos (/ˈkɜːrbərɒs/) is a computer-network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. Its designers aimed it primarily at a client–server model, and it provides mutual authentication—both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks. Kerberos builds on symmetric-key cryptography and requires a trusted third party, and optionally may use public-key cryptography during certain phases of authentication. Kerberos uses UDP port 88 by default. The protocol was named after the character Kerberos (or Cerberus) from Greek mythology, the ferocious three-headed guard dog of Hades.
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Topic Review
Test Data Generation
Test data generation, an important part of software testing, is the process of creating a set of data for testing the adequacy of new or revised software applications. It may be the actual data that has been taken from previous operations or artificial data created for this purpose. Test Data Generation is seen to be a complex problem and though a lot of solutions have come forth most of them are limited to toy programs. The use of dynamic memory allocation in most of the code written in industry is the most severe problem that the Test Data Generators face as the usage of the software then becomes highly unpredictable, due to this it becomes harder to anticipate the paths that the program could take making it nearly impossible for the Test Data Generators to generate exhaustive Test Data. However, in the past decade significant progress has been made in tackling this problem better by the use of genetic algorithms and other analysis algorithms. Moreover, Software Testing is an important part of the Software Development Life Cycle and is basically labor-intensive. It also accounts for nearly one third of the cost of the system development. In this view the problem of generating quality test data quickly, efficiently and accurately is seen to be important.
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Topic Review
Non-Linear Editing System
Non-linear editing is a form of offline editing for audio, video, and image editing. In offline editing, the original content is not modified in the course of editing. In non-linear editing, edits are specified and modified by specialized software. A pointer-based playlist, effectively an edit decision list (EDL), for video or a directed acyclic graph for still images is used to keep track of edits. Each time the edited audio, video, or image is rendered, played back, or accessed, it is reconstructed from the original source and the specified editing steps. Although this process is more computationally intensive than directly modifying the original content, changing the edits themselves can be almost instantaneous, and it prevents further generation loss as the audio, video, or image is edited. A non-linear editing system (NLE) is a video (NLVE) or audio editing (NLAE) digital audio workstation (DAW) system that performs non-destructive editing on source material. The name is in contrast to 20th century methods of linear video editing and film editing.
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