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Animal Shell
Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine animal, found on beaches * Eggshell * Nutshell * Exoskeleton, an external covering of some animals ** Mollusc shell *** Bivalve shell *** Gastropod shell ** Shell, of a brachiopod * Turtle shell * Armadillo shell Physics and chemistry * Electron shell or a principal energy level of electrons outside an atom's nucleus * Nuclear shell model, a principal energy level of nucleons within an atom's nucleus * On shell and off shell, quantum field theory concepts depending on whether classical equations of motion are obeyed Mathematics * Spherical shell Organisations * Shell plc formerly Royal Dutch Shell plc, a British multinational oil and gas company ** Shell Oil Company or Shell USA ** Shell Australia ** Shell Canada ** Shell Nigeria ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell (structure)
A shell is a three-dimensional solid structural element whose thickness is very small compared to its other dimensions. It is characterized in structural terms by mid-plane stress which is both coplanar and normal to the surface. A shell can be derived from a plate (structure), plate in two steps: by initially forming the middle surface as a singly or doubly curved surface, then by applying loads which are coplanar to the plate's plane (geometry), plane thus generating significant stresses. Materials range from concrete (a ''concrete shell'') to fabric (as in ''fabric structures''). Thin-shell structures (also called plate and shell structures) are lightweight constructions using List of structural elements, shell elements. These elements, typically curved, are assembled to make large structures. Typical applications include aircraft fuselages, boat hulls, and the roofs of large buildings. Definition A thin shell is defined as a shell with a thickness which is small compared to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell USA
Shell USA, Inc. (formerly Shell Oil Company, Inc.) is the United States–based wholly owned subsidiary of Shell plc, a UK-based transnational corporation " oil major" which is among the largest oil companies in the world. Approximately 18,000 Shell employees are based in the U.S. Its U.S. headquarters are in Houston, Texas. Shell USA, including its consolidated companies and its share in equity companies, is one of America's largest oil and natural gas producers, natural gas marketers, fuel marketers and petrochemical manufacturers. History In 1979, Shell purchased Belridge Oil Company for $3.65 billion, which at the time was called the "biggest cash takeover in American history" by US government sources. In 1997, Shell and Texaco entered into two refining/marketing joint ventures. One combined their Midwestern and Western operations and was known as Equilon. The other, known as Motiva Enterprises, combined the Eastern and Gulf Coast operations of Shell Oil and Star Enter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expert System
In artificial intelligence (AI), an expert system is a computer system emulating the decision-making ability of a human expert. Expert systems are designed to solve complex problems by reasoning through bodies of knowledge, represented mainly as if–then rules rather than through conventional procedural programming code. Expert systems were among the first truly successful forms of AI software. They were created in the 1970s and then proliferated in the 1980s, being then widely regarded as the future of AI — before the advent of successful artificial neural networks. An expert system is divided into two subsystems: 1) a ''knowledge base'', which represents facts and rules; and 2) an '' inference engine'', which applies the rules to the known facts to deduce new facts, and can include explaining and debugging abilities. History Early development Soon after the dawn of modern computers in the late 1940s and early 1950s, researchers started realizing the immense potential th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shellsort
Shellsort, also known as Shell sort or Shell's method, is an in-place algorithm, in-place comparison sort. It can be understood as either a generalization of sorting by exchange (bubble sort) or sorting by insertion (insertion sort). The method starts by sorting pairs of elements far apart from each other, then progressively reducing the gap between elements to be compared. By starting with far-apart elements, it can move some out-of-place elements into the position faster than a simple nearest-neighbor exchange. The running time of Shellsort is heavily dependent on the gap sequence it uses. For many practical variants, determining their time complexity remains an open problem. The algorithm was first published by Donald Shell in 1959, and has nothing to do with shells. Description Shellsort is an optimization of insertion sort that allows the exchange of items that are far apart. The idea is to arrange the list of elements so that, starting anywhere, taking every ''h''th elem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secure Shell
The Secure Shell Protocol (SSH Protocol) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution. SSH was designed for Unix-like operating systems as a replacement for Telnet and unsecured remote Unix shell protocols, such as the Berkeley Remote Shell (rsh) and the related rlogin and rexec protocols, which all use insecure, plaintext methods of authentication, like passwords. Since mechanisms like Telnet and Remote Shell are designed to access and operate remote computers, sending the authentication tokens (e.g. username and password) for this access to these computers across a public network in an unsecured way poses a great risk of 3rd parties obtaining the password and achieving the same level of access to the remote system as the telnet user. Secure Shell mitigates this risk through the use of encryption mechanisms that are intended to hide th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Account
A shell account is a user account on a remote server, typically running under Unix or Linux operating systems. The account gives access to a text-based command-line interface in a shell, via a terminal emulator. The user typically communicates with the server via the SSH protocol. In the early days of the Internet, one would connect using a modem. Shell accounts were first made accessible in the 1980s to interested members of the public by Internet Service Providers—such as Netcom, Panix, The World, and Digex—although in rare instances individuals had access to shell accounts through their employer or university. They were used for file storage, web space, email accounts, newsgroup access and software development. Before the late 1990s, shell accounts were often much less expensive than full net access through SLIP or PPP, which was required to access the then-new World Wide Web. Most personal computer operating systems also lacked TCP/IP stacks by default before the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Read–eval–print Loop
A read–eval–print loop (REPL), also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user; a program written in a REPL environment is executed piecewise. The term usually refers to programming interfaces similar to the classic Lisp machine interactive environment. Common examples include command-line interface, command-line shell (computing), shells and similar environments for programming languages, and the technique is very characteristic of scripting languages. History In 1964, the expression ''READ-EVAL-PRINT cycle'' is used by L. Peter Deutsch and Edmund Berkeley for an implementation of Lisp (programming language), Lisp on the PDP-1. Just one month later, Project Mac published a report by Joseph Weizenbaum (the creator of ELIZA, the world's first chatbot) describing a REPL-based language, called OPL-1, implemented in his SLIP (program ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Web Shell
A web shell is a Shell (computing), shell-like interface that enables a web server to be remotely accessed, often for the purposes of cyberattacks. A web shell is unique in that a web browser is used to interact with it. A web shell could be programmed in any programming language that is supported on a server. Web shells are most commonly written in PHP due to the widespread usage of PHP for web applications. Though Active Server Pages, ASP.NET, Python (programming language), Python, Perl, Ruby (programming language), Ruby, and Unix shell scripts are also used. Using Network monitoring#Notable network monitoring tools, network monitoring tools, an attacker can find Vulnerability (computing), vulnerabilities that can potentially allow delivery of a web shell. These vulnerabilities are often present in applications that are run on a web server. An attacker can use a web shell to issue shell commands, perform privilege escalation on the web server, and the ability to upload, File d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Command-line Interpreters
This list includes notable command-line interpreters programs that interactively interpret commands entered by the user at the command-line. Operating system shells Most operating systems are accessible via a shell a command line interpreter. In some cases multiple shells are available. This category somewhat overlaps with the general programming section since an operating system shell supports programming, and the line between operating system access and general programming is sometimes less than clear. For example, some versions of BASIC served as a shell, and BASIC is also a general-purpose language. Unix-like * Almquist shell (ash) * Bash (Unix shell) bash * Bourne shell sh * C shell csh * Ch shell ch * Debian Almquist shell (dash) * Emacs shell eshell * Friendly interactive shell fish * KornShell ksh * PowerShell pwsh * rc shell rc, a shell for Plan 9 from Bell Labs and Unix * Stand-alone shell sash * Scheme Shell scsh * TENEX C shell tcsh * Z shell zsh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interface
A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards. For a long time, a CLI was the most common interface for software, but today a graphical user interface (GUI) is more common. Nonetheless, many programs such as operating system and software development utility software, utilities still provide CLI. A CLI enables automation, automating computer program, programs since commands can be stored in a scripting language, script computer file, file that can be used repeatedly. A script allows its contained commands to be executed as group; as a program; as a command. A CLI is made possible by command-line interpreters or command-line processors, which are programs that execute input commands. Alternatives to a CLI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell (computing)
An operating system shell is a computer program that provides relatively broad and direct access to the system on which it runs. The term ''shell'' refers to how it is a relatively thin Abstraction layer, layer around an operating system. A shell is generally a command-line interface (CLI) program although some graphical user interface (GUI) programs are arguably classified as shells too. Overview Operating systems provide various services to their users, including File manager, file management, Process (computing), process management (running and terminating Application program, applications), batch processing, and operating system monitoring and configuration. Most operating system shells are not ''direct'' interfaces to the underlying Kernel (operating system), kernel, even if a shell communicates with the user via peripheral devices attached to the computer directly. Shells are actually special applications that use the kernel API in just the same way as it is used by ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Corporation
A shell corporation is a company or corporation with no significant assets or operations often formed to obtain financing before beginning business. Shell companies were primarily vehicles for lawfully hiding the identity of their beneficial owners, and this is still the defining feature of shell companies due to the loopholes in the global corporate transparency initiatives. It may hold passive investments or be the registered owner of assets, such as intellectual property, or ships. Shell companies may be registered to the address of a company that provides a service setting up shell companies, and which may act as the agent for receipt of legal correspondence (such as an accountant or lawyer). The company may serve as a vehicle for business transactions without itself having any significant assets or operations. Shell companies are used for legitimate purposes but can be used for tax evasion, tax avoidance, money laundering, to dodge current or future lawsuits or to achi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
