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Topic Review
Prospects of Cybersecurity in Smart Cities
Smart cities are urban spaces characterized by the widespread use of Information and Communication Technologies (ICTs). They intend to improve political-economic efficiency and support human and social development, thus improving the quality of life of its citizens. Cybersecurity plays a key role in smart cities due to the increasing interconnectivity and widespread use of ICT.
  • 318
  • 01 Sep 2023
Topic Review
Proprietary Device Driver
A proprietary device driver is a closed-source device driver published only in binary code. In the context of free and open-source software, a closed-source device driver is referred to as a blob or binary blob. The term usually refers to a closed-source kernel module loaded into the kernel of an open-source operating system, and is sometimes also applied to code running outside the kernel, such as system firmware images, microcode updates, or userland programs. The term blob was first used in database management systems to describe a collection of binary data stored as a single entity. When computer hardware vendors provide complete technical documentation for their products, operating system developers are able to write hardware device drivers to be included in the operating system kernels. However, some vendors, such as Nvidia, do not provide complete documentation for some of their products and instead provide binary-only drivers. This practice is most common for accelerated graphics drivers, wireless networking devices, and hardware RAID controllers. Most notably, binary blobs are very uncommon for non-wireless network interface controllers, which can almost always be configured via standard utilities (like ifconfig) out of the box; Theo de Raadt of OpenBSD attributes this to the work done by a single FreeBSD developer.
  • 1.2K
  • 24 Oct 2022
Topic Review
Property
In logic and philosophy (especially metaphysics), a property is a characteristic of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property, however, differs from individual objects in that it may be instantiated, and often in more than one object. It differs from the logical/mathematical concept of class by not having any concept of extensionality, and from the philosophical concept of class in that a property is considered to be distinct from the objects which possess it. Understanding how different individual entities (or particulars) can in some sense have some of the same properties is the basis of the problem of universals.
  • 618
  • 28 Nov 2022
Topic Review
Properties of Polynomial Roots
In mathematics, a univariate polynomial is an expression of the form where the ai belong to some field, which, in this article, is always the field [math]\displaystyle{ \mathbb C }[/math] of the complex numbers. The natural number n is known as the degree of the polynomial. In the following, p will be used to represent the polynomial, so we have A root of the polynomial p is a solution of the equation p = 0: that is, a complex number a such that p(a) = 0. The fundamental theorem of algebra combined with the factor theorem states that the polynomial p has n roots in the complex plane, if they are counted with their multiplicities. This article concerns various properties of the roots of p, including their location in the complex plane.
  • 1.5K
  • 21 Nov 2022
Topic Review
Propellerhead Software
Reason Studios (formerly known as Propellerhead Software) is a music software company, based in Stockholm, Sweden, and founded in 1994. It produces the studio emulation Reason.
  • 455
  • 04 Nov 2022
Topic Review
Propagation Graph
Propagation Graphs are a mathematical modelling method for radio propagation channels. A propagation graph is a signal flow graph in which vertices represent transmitters, receivers or scatterers, and edges models propagation conditions between vertices. Propagation graph models were initially developed in for multipath propagation in scenarios with multiple scattering, such as indoor radio propagation. It has later been applied in many other scenarios.
  • 992
  • 21 Oct 2022
Topic Review
Proofs of Fermat's Theorem on Sums of Two Squares
Fermat's theorem on sums of two squares asserts that an odd prime number p can be expressed as with integer x and y if and only if p is congruent to 1 (mod 4). The statement was announced by Girard in 1625, and again by Fermat in 1640, but neither supplied a proof. The "only if" clause is easy: a perfect square is congruent to 0 or 1 modulo 4, hence a sum of two squares is congruent to 0, 1, or 2. An odd prime number is congruent to either 1 or 3 modulo 4, and the second possibility has just been ruled out. The first proof that such a representation exists was given by Leonhard Euler in 1747 and was complicated. Since then, many different proofs have been found. Among them, the proof using Minkowski's theorem about convex sets and Don Zagier's short proof based on involutions have appeared.
  • 4.1K
  • 11 Nov 2022
Topic Review
Proofs Involving the Moore–Penrose Inverse
In linear algebra, the Moore–Penrose inverse is a matrix that satisfies some but not necessarily all of the properties of an inverse matrix. This article collects together a variety of proofs involving the Moore–Penrose inverse.
  • 3.7K
  • 01 Dec 2022
Topic Review
Proof-of-Work System
A Proof-of-Work (PoW) system (or protocol, or function) is an economic measure to deter denial of service attacks and other service abuses such as spam on a network by requiring some work from the service requester, usually meaning processing time by a computer. The concept was invented by Cynthia Dwork and Moni Naor as presented in a 1993 journal article. The term "Proof of Work" or PoW was first coined and formalized in a 1999 paper by Markus Jakobsson and Ari Juels. An early example of the proof-of-work system used to give value to a currency is the shell money of the Solomon Islands. A key feature of these schemes is their asymmetry: the work must be moderately hard (but feasible) on the requester side but easy to check for the service provider. This idea is also known as a CPU cost function, client puzzle, computational puzzle or CPU pricing function. It is distinct from a CAPTCHA, which is intended for a human to solve quickly, rather than a computer. Proof of space (PoSpace) proposals apply the same principle by proving a dedicated amount of memory or disk space instead of CPU time. Proof-of-Stake, Proof of bandwidth, and other approaches have been discussed in the context of cryptocurrency. Proof of ownership aims at proving that specific data are held by the prover.
  • 863
  • 07 Nov 2022
Topic Review
Prompt (Command)
This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built into the command interpreter, others existed as external commands on disk. Over the several generations of DOS, commands were added for the additional functions of the operating system. In the current Microsoft Windows operating system, a text-mode command prompt window, cmd.exe, can still be used.
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  • 24 Oct 2022
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