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Topic Review
Discrete Event Simulation
A discrete-event simulation (DES) models the operation of a system as a discrete sequence of events in time. Each event occurs at a particular instant in time and marks a change of state in the system. Between consecutive events, no change in the system is assumed to occur; thus the simulation can directly jump in time from one event to the next. This contrasts with continuous simulation in which the simulation continuously tracks the system dynamics over time. Instead of being event-based, this is called an activity-based simulation; time is broken up into small time slices and the system state is updated according to the set of activities happening in the time slice. Because discrete-event simulations do not have to simulate every time slice, they can typically run much faster than the corresponding continuous simulation. A more recent method is the three-phased approach to discrete event simulation (Pidd, 1998). In this approach, the first phase is to jump to the next chronological event. The second phase is to execute all events that unconditionally occur at that time (these are called B-events). The third phase is to execute all events that conditionally occur at that time (these are called C-events). The three phase approach is a refinement of the event-based approach in which simultaneous events are ordered so as to make the most efficient use of computer resources. The three-phase approach is used by a number of commercial simulation software packages, but from the user's point of view, the specifics of the underlying simulation method are generally hidden.
  • 1.0K
  • 02 Nov 2022
Topic Review
Shibboleth
Shibboleth is a single sign-on log-in system for computer networks and the Internet. It allows people to sign in using just one identity to various systems run by federations of different organizations or institutions. The federations are often universities or public service organizations. The Shibboleth Internet2 middleware initiative created an architecture and open-source implementation for identity management and federated identity-based authentication and authorization (or access control) infrastructure based on Security Assertion Markup Language (SAML). Federated identity allows the sharing of information about users from one security domain to the other organizations in a federation. This allows for cross-domain single sign-on and removes the need for content providers to maintain user names and passwords. Identity providers (IdPs) supply user information, while service providers (SPs) consume this information and give access to secure content.
  • 1.0K
  • 28 Nov 2022
Topic Review
Conceptual Modelling in Operational Simulation of Logistics
Logistics problems involve a large number of complexities, which makes the development of models challenging. While computer simulation models are developed for addressing complexities, it is essential to ensure that the necessary operational behaviours are captured, and that the architecture of the model is suitable to represent them. The early stage of simulation modelling, known as conceptual modelling (CM), is thus dependent on successfully extracting tacit operational knowledge and avoiding misunderstanding between the client (customer of the model) and simulation analyst.
  • 995
  • 21 Jun 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.
  • 974
  • 25 Oct 2022
Topic Review
Grand Central Dispatch
Grand Central Dispatch (GCD or libdispatch), is a technology developed by Apple Inc. to optimize application support for systems with multi-core processors and other symmetric multiprocessing systems. It is an implementation of task parallelism based on the thread pool pattern. The fundamental idea is to move the management of the thread pool out of the hands of the developer, and closer to the operating system. The developer injects "work packages" into the pool oblivious of the pool's architecture. This model improves simplicity, portability and performance. GCD was first released with Mac OS X 10.6, and is also available with iOS 4 and above. The name "Grand Central Dispatch" is a reference to Grand Central Terminal. The source code for the library that provides the implementation of GCD's services, libdispatch, was released by Apple under the Apache License on September 10, 2009. It has been ported to FreeBSD 8.1+, MidnightBSD 0.3+, Linux, and Solaris. Attempts in 2011 to make libdispatch work on Windows were not merged into upstream. Apple has its own port of libdispatch.dll for Windows shipped with Safari and iTunes, but no SDK is provided. Since around 2017, the original libdispatch repository hosted by Nick Hutchinson was deprecated in favor of a version that is part of the Swift core library created in June 2016. The new version supports more platforms, notably including Windows.
  • 965
  • 04 Nov 2022
Topic Review
Timeline of Open-Source Software
This article presents a timeline of events related to popular free/open-source software. For a narrative explaining the overall development, see the related history of free and open-source software. The Achievements column documents achievements a project attained at some point in time (not necessarily when it was first released).
  • 962
  • 08 Dec 2022
Topic Review
Blockchain Technology in Agricultural Products and Food Applications
Compared with the traditional centralized information supervision mode, the application of blockchain as a new scientific and technological innovation technology in the management of agricultural products and food supply chain can promote a more refined management of agricultural products and food, and provide feasible ideas for ensuring the quality and safety of agricultural products and food.  
  • 955
  • 29 Sep 2022
Topic Review
Atom (Web Standard)
The name Atom applies to a pair of related Web standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web resources. Web feeds allow software programs to check for updates published on a website. To provide a web feed, the site owner may use specialized software (such as a content management system) that publishes a list (or "feed") of recent articles or content in a standardized, machine-readable format. The feed can then be downloaded by programs that use it, like websites that syndicate content from the feed, or by feed reader programs that allow internet users to subscribe to feeds and view their content. A feed contains entries, which may be headlines, full-text articles, excerpts, summaries or links to content on a website along with various metadata. The Atom format was developed as an alternative to RSS. Ben Trott, an advocate of the new format that became Atom, believed that RSS had limitations and flaws—such as lack of on-going innovation and its necessity to remain backward compatible—and that there were advantages to a fresh design. Proponents of the new format formed the IETF Atom Publishing Format and Protocol Workgroup. The Atom Syndication Format was published as an IETF proposed standard in RFC 4287 (December 2005), and the Atom Publishing Protocol was published as RFC 5023 (October 2007).
  • 946
  • 02 Nov 2022
Topic Review
IBM TopView
TopView is the first object-oriented, multitasking, and windowing, personal computer operating environment for PC DOS developed by IBM, announced in August 1984 and shipped in March 1985. TopView provided a text-mode (although it also ran in graphics mode) operating environment that allowed users to run more than one application at the same time on a PC. IBM demonstrated an early version of the product to key customers before making it generally available, around the time they shipped their new PC AT computer.
  • 941
  • 27 Oct 2022
Topic Review
WebUSB
WebUSB is a JavaScript application programming interface (API) specification for securely providing access to USB devices from web pages. It was published by the Web Platform Incubator Community Group. As of July 2021, it is in Draft Community status, and is supported by Google Chrome, Microsoft Edge, QQ, Opera, and Samsung Internet.
  • 932
  • 30 Nov 2022
Topic Review
Shibboleth (Shibboleth Consortium)
Shibboleth is a single sign-on log-in system for computer networks and the Internet. It allows people to sign in using just one identity to various systems run by federations of different organizations or institutions. The federations are often universities or public service organizations. The Shibboleth Internet2 middleware initiative created an architecture and open-source implementation for identity management and federated identity-based authentication and authorization (or access control) infrastructure based on Security Assertion Markup Language (SAML). Federated identity allows the sharing of information about users from one security domain to the other organizations in a federation. This allows for cross-domain single sign-on and removes the need for content providers to maintain user names and passwords. Identity providers (IdPs) supply user information, while service providers (SPs) consume this information and give access to secure content.
  • 905
  • 20 Oct 2022
Topic Review
Dask
Dask is a flexible open-source Python library for parallel computing. Dask scales Python code from multi-core local machines to large distributed clusters in the cloud. Dask provides a familiar user interface by mirroring the APIs of other libraries in the PyData ecosystem including: Pandas, Scikit-learn and NumPy. It also exposes low-level APIs that help programmers run custom algorithms in parallel. Dask was created by Matthew Rocklin in December 2014 and has over 9.8k stars and 500 contributors on GitHub. Dask is used by retail, financial, governmental organizations, as well as life science and geophysical institutes. Walmart, Wayfair, JDA, GrubHub, General Motors, NVIDIA, Harvard Medical School, Capital One and NASA are among the organizations that use Dask.
  • 901
  • 20 Oct 2022
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.
  • 900
  • 25 Oct 2022
Topic Review
Timeline of Computing 1990–99
This article presents a detailed timeline of events in the history of computing from 1990 to 1999. For narratives explaining the overall developments, see the History of computing.
  • 891
  • 28 Nov 2022
Topic Review
Reversible Data Hiding in Encrypted Images
As a necessary technical means, reversible data hiding in encrypted images (RDH-EIs) provides superior performance in terms of security. To simultaneously improve the effectiveness of RDH-EIs, the researchers proposed a mixed multi-bit layer embedding strategy in encrypted images.
  • 884
  • 24 May 2023
Topic Review
SGI Octane
Octane series of IRIX workstations was developed and sold by SGI in the 2000s. Octane and Octane2 are two-way multiprocessing-capable workstations, originally based on the MIPS Technologies R10000 microprocessor. Newer Octanes are based on the R12000 and R14000. The Octane2 has four improvements: a revised power supply, system board, and Xbow ASIC. The Octane2 has VPro graphics and supports all the VPro cards. Later revisions of the Octane include some of the improvements introduced in the Octane2. The codenames for the Octane and Octane2 are "Racer" and "Speedracer" respectively. The Octane is the direct successor to the Indigo2, and was succeeded by the Tezro, and its immediate sibling is the O2. SGI withdrew the Octane2 from the price book on May 26, 2004, and ceased Octane2 production on June 25, 2004. Support for the Octane2 ceased in June 2009. Octane III was introduced in early 2010 after SGI's bankruptcy reorganization. It is a series of Intel based deskside systems, as a Xeon-based workstation with 1 or 2 3U EATX trays, or as cluster servers with 10 system trays configured with up to 10 Twin Blade nodes or 20 Intel ATOM MINI-ITX nodes.
  • 882
  • 01 Nov 2022
Topic Review
Dynamic Feedback-Driven Learning Optimization Framework
A novel approach named the Dynamic Feedback-Driven Learning Optimization Framework (DFDLOF), aimed at personalizing educational pathways through machine learning technology.
  • 872
  • 18 Feb 2024
Topic Review
Foreign Language Learning in Virtual Reality
With the widespread application of virtual reality (VR) in education, optimizing foreign language learning in VR has become a focal point of research.
  • 863
  • 06 Dec 2023
Topic Review
Revisiting the High-Performance Reconfigurable Computing
Modern datacenters are reinforcing the computational power and energy efficiency by assimilating field programmable gate arrays (FPGAs). The sustainability of this large-scale integration depends on enabling multi-tenant FPGAs. This requisite amplifies the importance of communication architecture and virtualization method with the required features in order to meet the high-end objective.
  • 862
  • 27 Jun 2022
Topic Review
Data Integrity Tracking and Verification System
Data integrity is a prerequisite for ensuring data availability of IoT data and has received extensive attention in the field of IoT big data security. Stream computing systems are widely used in the field of IoT for real-time data acquisition and computing. The real-time, volatility, suddenness, and disorder of stream data make data integrity verification difficult. The data integrity tracking and verification system is constructed based on a data integrity verification algorithm scheme of the stream computing system (S-DIV) to  track and analyze the message data stream in real time. By verifying the data integrity of message during the whole life cycle, the problem of data corruption or data loss can be found in time, and error alarm and message recovery can be actively implemented.
  • 852
  • 13 Feb 2023
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