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Topic Review
Land Surface Model
Land Surface Models (LSMs) are important components of the climate models, which help to capture the water, energy, and momentum exchange between the land surface and the atmosphere, providing lower boundary conditions to the atmospheric models.
  • 2.5K
  • 02 Apr 2021
Topic Review
Incircle and Excircles of a Triangle
In geometry, the incircle or inscribed circle of a triangle is the largest circle contained in the triangle; it touches (is tangent to) the three sides. The center of the incircle is a triangle center called the triangle's incenter. An excircle or escribed circle of the triangle is a circle lying outside the triangle, tangent to one of its sides and tangent to the extensions of the other two. Every triangle has three distinct excircles, each tangent to one of the triangle's sides. The center of the incircle, called the incenter, can be found as the intersection of the three internal angle bisectors. The center of an excircle is the intersection of the internal bisector of one angle (at vertex [math]\displaystyle{ A }[/math], for example) and the external bisectors of the other two. The center of this excircle is called the excenter relative to the vertex [math]\displaystyle{ A }[/math], or the excenter of [math]\displaystyle{ A }[/math]. Because the internal bisector of an angle is perpendicular to its external bisector, it follows that the center of the incircle together with the three excircle centers form an orthocentric system.:p. 182 All regular polygons have incircles tangent to all sides, but not all polygons do; those that do are tangential polygons. 
  • 2.5K
  • 11 Nov 2022
Topic Review
Jump Point Search Algorithm
The JPS algorithm is a pathfinding algorithm that uses pruned neighbor rules as the search direction of nodes and the position of forced neighbors as the judgment of jump points.
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  • 21 Jun 2022
Topic Review
Halt and Catch Fire
In computer engineering, Halt and Catch Fire, known by the assembly mnemonic HCF, is an idiom referring to a computer machine code instruction that causes the computer's central processing unit (CPU) to cease meaningful operation, typically requiring a restart of the computer. It originally referred to a fictitious instruction in IBM System/360 computers, making a joke about its numerous non-obvious instruction mnemonics. With the advent of the MC6800, a design flaw was discovered by the programmers. Due to incomplete opcode decoding, two illegal opcodes, 0x9D and 0xDD, will cause the program counter on the processor to increment endlessly, which renders the processor useless. Those codes have been unofficially named HCF. During the design process of MC6802, engineers originally planned to remove this instruction, but kept it as-is for testing purposes. As a result, HCF was officially recognized as a real instruction. Later, HCF became a humorous catch-all term for instructions that may freeze a processor, including intentional instructions for testing purposes, and unintentional illegal instructions. Some are considered hardware defects, and if the system is shared, a malicious user can execute it to launch a denial-of-service attack. In the case of real instructions, the implication of this expression is that, whereas in most cases in which a CPU executes an unintended instruction (a bug in the code) the computer may still be able to recover, in the case of an HCF instruction there is, by definition, no way for the system to recover without a restart. The expression "catch fire" is a facetious exaggeration of the speed with which the CPU chip would be switching some bus circuits, causing them to overheat and burn.
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  • 04 Nov 2022
Topic Review
1994 Scotland RAF Chinook Crash
On 2 June 1994, a Chinook helicopter of the Royal Air Force (RAF), serial number ZD576, crashed on the Mull of Kintyre, Scotland, in foggy conditions. The crash resulted in the deaths of all twenty-five passengers and four crew on board. Among the passengers were almost all the United Kingdom's senior Northern Ireland intelligence experts. The accident is the RAF's worst peacetime disaster. In 1995, an RAF board of inquiry ruled that it was impossible to establish the exact cause of the accident. This ruling was subsequently overturned by two senior reviewing officers, who stated the pilots were guilty of gross negligence for flying too fast and too low in thick fog. This finding proved to be controversial, especially in light of irregularities and technical issues surrounding the then-new Chinook HC.2 variant which were uncovered. A Parliamentary inquiry conducted in 2001 found the previous verdict of gross negligence on the part of the crew to be 'unjustified'. In 2011, an independent review of the crash cleared the crew of negligence.
  • 2.5K
  • 14 Nov 2022
Topic Review
Mozilla Public License
The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird The MPL license is developed and maintained by Mozilla, which seeks to balance the concerns of both open-source and proprietary developers; it is distinguished from others as a middle ground between the permissive software BSD-style licenses and the General Public License. So under the terms of the MPL, it allows the integration of MPL-licensed code into proprietary codebases, but only on condition those components remain accessible. MPL has been used by others, such as Adobe to license their Flex product line, and The Document Foundation to license LibreOffice 4.0 (also on LGPL 3+). Version 1.1 was adapted by several projects to form derivative licenses like Sun Microsystems' Common Development and Distribution License. It has undergone two revisions: the minor update 1.1, and a major update version 2.0 nearing the goals of greater simplicity and better compatibility with other licenses.
  • 2.5K
  • 04 Nov 2022
Topic Review
Domain Fronting
Domain fronting is a technique for Internet censorship circumvention that uses different domain names in different communication layers of an HTTPS connection to discreetly connect to a different target domain than is discernable to third parties monitoring the requests and connections. Due to quirks in security certificates, the redirect systems of the content delivery networks (CDNs) used as 'domain fronts', and the protection provided by HTTPS, censors are typically unable to differentiate circumvention ("domain-fronted") traffic from overt non-fronted traffic for any given domain name. As such they are forced to either allow all traffic to the domain front—including circumvention traffic—or block the domain front entirely, which may result in expensive collateral damage and has been likened to "blocking the rest of the Internet".[note 1] Domain fronting does not conform to HTTP standards that require the SNI extension and HTTP Host header to contain the same domain. Large cloud service providers, including Amazon and Google, now actively prohibit domain fronting, which has made it "largely non-viable"[note 1] as a censorship bypass technique.
  • 2.5K
  • 06 Oct 2022
Topic Review
Wireless Sensor Network
Wireless Sensor Network (WSN) is one of the most effective methods for many real-time applications, due to its compactness, cost-effectiveness, and ease of deployment. The function of the WSN is to monitor the field of interest, collect the data, and transmit it to the base station (Access point) for post-processing analysis.
  • 2.4K
  • 21 Jul 2022
Topic Review
Lists of Mathematics Topics
This article itemizes the various lists of mathematics topics. Some of these lists link to hundreds of articles; some link only to a few. The template to the right includes links to alphabetical lists of all mathematical articles. This article brings together the same content organized in a manner better suited for browsing. The purpose of this list is not similar to that of the Mathematics Subject Classification formulated by the American Mathematical Society. Many mathematics journals ask authors of research papers and expository articles to list subject codes from the Mathematics Subject Classification in their papers. The subject codes so listed are used by the two major reviewing databases, Mathematical Reviews and Zentralblatt MATH. This list has some items that would not fit in such a classification, such as list of exponential topics and list of factorial and binomial topics, which may surprise the reader with the diversity of their coverage.
  • 2.4K
  • 19 Oct 2022
Topic Review
YOLOv5-AC
Attention Mechanism-Based Lightweight YOLOv5 for Track Pedestrian Detection. In response to the dangerous behavior of pedestrians roaming freely on unsupervised train tracks, the real-time detection of pedestrians is urgently required to ensure the safety of trains and people. Aiming to improve the low accuracy of railway pedestrian detection, the high missed-detection rate of target pedestrians, and the poor retention of non-redundant boxes, YOLOv5 is adopted as the baseline to improve the effectiveness of pedestrian detection by model pruning, improving attention mechanism, etc.
  • 2.4K
  • 15 Sep 2022
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