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Cascading Failure
A cascading failure is a failure in a system of interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a single part fails, increasing the probability that other portions of the system fail. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems. Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another. In power transmission Cascading failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2019 Argentina, Paraguay And Uruguay Blackout
On 16 June 2019, a large-scale power outage struck most of Argentina, all of Uruguay, and parts of Paraguay, leaving an estimated total of 48 million people without electrical supply. By the following day it was confirmed that power had been restored to most of Argentina and Uruguay, and Argentine President Mauricio Macri promised a full investigation. The blackout is believed to have been caused by an operational misbehavior from Transener, a transmission lines operator in Argentina. A 500 kV line running from Colonia Elía to Campana, crossing the Paraná Guazú river, was down on undergoing maintenance to repair the tower number 412, whose base had been suffering from erosion by the river. The company made a bypass for this tasks, using a nearby overhead line, but missed to reflect that network grid change in the Automatic Generation Shutdown system (in spanish: DAG), which is designed to alert energy generators of network changes that would require a lower of energy ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zipper
A zipper, zip, fly, or zip fastener, formerly known as a clasp locker, is a commonly used device for binding together two edges of fabric or other flexible material. Used in clothing (e.g. jackets and jeans), luggage and other bags, camping gear (e.g. tents and sleeping bags), and many other items, zippers come in a wide range of sizes, shapes, and colors. Whitcomb L. Judson, an American inventor from Chicago, in 1892 patented the original design from which the modern device evolved. Description A zipper consists of a slider mounted on two rows of metal or plastic teeth that are designed to interlock and thereby join the material to which the rows are attached. The slider, usually operated by hand, contains a Y-shaped channel that, by moving along the rows of teeth, meshes or separates them, depending on the direction of the slider's movement. The teeth may be individually discrete or shaped from a continuous coil, and are also referred to as ''elements''. The word ''zipp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyatt Regency Walkway Collapse
On July 17, 1981, the Hyatt Regency Hotel in Kansas City, Missouri, suffered the structural collapse of two overhead walkways. Loaded with partygoers, the concrete and glass platforms cascaded down, crashing onto a tea dance in the lobby, killing 114 and injuring 216. Kansas City society was affected for years, with the collapse resulting in billions of dollars of insurance claims, legal investigations and city government reforms. The Hyatt had been built just a few years before, during a nationwide pattern of fast-tracked large construction with reduced oversight and major failures. Its roof had partially collapsed during construction, and the ill-conceived skywalk design progressively degraded due to a miscommunication loop of corporate neglect and irresponsibility. An investigation concluded that it would have failed even under one-third of the weight it held that night. Convicted of gross negligence, misconduct and unprofessional conduct, the engineering company lost its na ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gmail
Gmail is a free email service provided by Google. As of 2019, it had 1.5 billion active users worldwide. A user typically accesses Gmail in a web browser or the official mobile app. Google also supports the use of email clients via the POP and IMAP protocols. At its launch in 2004, Gmail provided a storage capacity of one gigabyte per user, which was significantly higher than its competitors offered at the time. Today, the service comes with 15 gigabytes of storage. Users can receive emails up to 50 megabytes in size, including attachments, while they can send emails up to 25 megabytes. In order to send larger files, users can insert files from Google Drive into the message. Gmail has a search-oriented interface and a "conversation view" similar to an Internet forum. The service is notable among website developers for its early adoption of Ajax. Google's mail servers automatically scan emails for multiple purposes, including to filter spam and malware, and to add context-sen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domain Name System
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to each of the associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. The Domain Name System has been an essential component of the functionality of the Internet since 1985. The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over sub-domains of their allocated name space to other name servers. This mechanism provides distributed and fault-tolerant service and was designed to avoid a single large central ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hop (telecommunications)
In telecommunication, a hop is a portion of a signal's journey from source to receiver. Examples include: #The excursion of a radio wave from the Earth to the ionosphere and back to the Earth. The number of hops indicates the number of reflections from the ionosphere.Federal Standard 1037C #A similar excursion from an earth station to a communications satellite to another station, counted similarly except that if the return trip is not by satellite, then it is only a half hop. In computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...s, a hop is the step from one network segment to the next. References Telecommunications engineering Radio frequency propagation {{Telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Congestion Collapse
Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of new connections. A consequence of congestion is that an incremental increase in offered load leads either only to a small increase or even a decrease in network throughput. Network protocols that use aggressive retransmissions to compensate for packet loss due to congestion can increase congestion, even after the initial load has been reduced to a level that would not normally have induced network congestion. Such networks exhibit two stable states under the same level of load. The stable state with low throughput is known as congestive collapse. Networks use congestion control and congestion avoidance techniques to try to avoid collapse. These include: exponential backoff in protocols such as CSMA/CA in 802.11 and the similar CSMA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latency (engineering)
Latency, from a general point of view, is a time delay between the cause and the effect of some physical change in the system being observed. Lag, as it is known in gaming circles, refers to the latency between the input to a simulation and the visual or auditory response, often occurring because of network delay in online games. Latency is physically a consequence of the limited velocity at which any physical interaction can propagate. The magnitude of this velocity is always less than or equal to the speed of light. Therefore, every physical system with any physical separation (distance) between cause and effect will experience some sort of latency, regardless of the nature of the stimulation at which it has been exposed to. The precise definition of latency depends on the system being observed or the nature of the simulation. In communications, the lower limit of latency is determined by the medium being used to transfer information. In reliable two-way communication s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Kurose, J.F. & Ross, K.W. (2010). ''Computer Networking: A Top-Down Approach''. New York: Addison-Wesley. Packet loss is measured as a percentage of packets lost with respect to packets sent. The Transmission Control Protocol (TCP) detects packet loss and performs retransmissions to ensure reliable messaging. Packet loss in a TCP connection is also used to avoid congestion and thus produces an intentionally reduced throughput for the connection. In real-time applications like streaming media or online games, packet loss can affect a user's quality of experience (QoE). Causes The Internet Protocol (IP) is designed according to the end-to-end principle as a best-effort delivery service, with the intention of keeping the logic routers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone network (PSTN), and computer networks, such as the Internet. In packet switching networks, routing is the higher-level decision making that directs network packets from their source toward their destination through intermediate network nodes by specific packet forwarding mechanisms. Packet forwarding is the transit of network packets from one network interface to another. Intermediate nodes are typically network hardware devices such as routers, gateways, firewalls, or switches. General-purpose computers also forward packets and perform routing, although they have no specially optimized hardware for the task. The routing process usually directs forwarding on the basis of routing tables. Routing tables maintain a record of the routes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Router (computing)
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork (e.g. the Internet) until it reaches its destination node. A router is connected to two or more data lines from different IP networks. When a data packet comes in on one of the lines, the router reads the network address information in the packet header to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. The most familiar type of IP routers are home and small office routers that simply forward IP packets between the home computers and the Internet. More sophisticated routers, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
