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Shell Stars
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 ** Thin-shell structure 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 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, a British multinational oil and gas company ** Shell USA ** Shell Australia ** Shell Canada ** Shell Nigeria * Shell corporation, a type of company that serves as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell (structure)
A shell is a type of structural element which is characterized by its geometry, being a three-dimensional solid whose thickness is very small when compared with other dimensions, and in structural terms, by the stress resultants calculated in the middle plane displaying components which are both coplanar and normal to the surface. Essentially, a shell can be derived from a plate (structure), plate by two means: by initially forming the middle surface as a singly or doubly curved surface, and by applying loads which are coplanar to a plate's plane (geometry), plane which generate significant stresses. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Oil Company
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 amongst 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, gasoline marketers and petrochemical manufacturers. History 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 Enterprise, itself a joint venture between Saudi Aramco and Texaco. After Texaco merged with Chevron in 2001, Shell purchased Texaco's shares in the joint ventures. In 2002 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expert System
In artificial intelligence, 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 code. The first expert systems were created in the 1970s and then proliferated in the 1980s. Expert systems were among the first truly successful forms of artificial intelligence (AI) software. An expert system is divided into two subsystems: the inference engine and the knowledge base. The knowledge base represents facts and rules. The inference engine applies the rules to the known facts to deduce new facts. Inference engines can also include explanation 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 these machines had for modern society. One of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shellsort
Shellsort, also known as Shell sort or Shell's method, is an in-place comparison sort. It can be seen 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 position faster than a simple nearest neighbor exchange. Donald Shell published the first version of this sort in 1959. 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. 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 element produces a sorted list. Such a list is said to be ''h''- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secure Shell
The Secure Shell Protocol (SSH) 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 applications are based on a client–server architecture, connecting an SSH client instance with an SSH server. SSH operates as a layered protocol suite comprising three principal hierarchical components: the ''transport layer'' provides server authentication, confidentiality, and integrity; the ''user authentication protocol'' validates the user to the server; and the ''connection protocol'' multiplexes the encrypted tunnel into multiple logical communication channels. SSH was designed on Unix-like operating systems, as a replacement for Telnet and for unsecured remote Unix shell protocols, such as the Berkeley Remote Shell (rsh) and the related rlogin and rexec protocols, which all use insecure, plaintext transmission of authentication tokens. SSH was first de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Account
A shell account is a user account on a remote server, traditionally running under the Unix operating system, which gives access to a shell via a command-line interface protocol such as telnet, SSH, or over a modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ... using a terminal emulator. Shell accounts were made first accessible to interested members of the public by Internet Service Providers (such as Netcom (USA), Panix (ISP), Panix, The World (internet service provider), 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 ... [...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 shells and similar environments for programming languages, and the technique is very characteristic of scripting languages. History The first Read-Eval-Print loop, ''cycle'', was invented in 1964 by L. Peter Deutsch and Edmund Berkeley for an implementation of Lisp on the PDP-1. Overview In a REPL, the user enters one or more expressions (rather than an entire compilation unit) and the REPL evaluates them and displays the results. The name ''read–eval–print loop'' comes from the names of the Lisp primitive functions which implement this fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Web Shell
A web shell is a 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 the PHP programming language due to the widespread usage of PHP for web applications. However, Active Server Pages, ASP.NET, Python, Perl, Ruby, and Unix shell scripts are also used, although these languages are less commonly used. Using network monitoring tools, an attacker can find 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 deletion, delete, download, and execute files to and from the web server. Gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Command-line Interpreters
In computing, a command-line interpreter, or command language interpreter, is a blanket term for a certain class of programs designed to read lines of text entered by a user, thus implementing a command-line interface. Operating system shells AmigaOS * Amiga CLI/Amiga Shell Unix-like systems There are many variants of Unix shell: * Bourne shell sh ** Almquist shell (ash) *** Debian Almquist shell (dash) ** Bash (Unix shell) bash ** KornShell ksh *** Z shell zsh * C shell csh ** TENEX C shell tcsh * Ch shell ch * Emacs shell eshell * Friendly interactive shell fish * PowerShell pwsh * rc shell rc, a shell for Plan 9 from Bell Labs and Unix * Stand-alone shell sash * Scheme Shell scsh Microsoft Windows Native * COMMAND.COM, the original Microsoft command line processor introduced on MS-DOS as well as Windows 9x, in 32-bit versions of NT-based Windows via NTVDM * cmd.exe, successor of COMMAND.COM introduced on OS/2 and Windows NT systems, although COMMAND.CO ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interface
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and providing information to them as to what actions they are to perform. In some cases the invocation is conditional based on conditions established by the user or previous executables. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods. Today, many users rely upon graphical user interfaces and menu-driven interactions. However, some programming and maintenance tasks may not have a graphical user interface and use a command line. Alternatives to the command-line interface include text-based user interface menus (for example, IBM AIX SMIT), keyboard shortcuts, and various desktop metaphors centered on the pointer (usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell (computing)
In computing, a shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation. It is named a shell because it is the outermost layer around the operating system. Command-line shells require the user to be familiar with commands and their calling syntax, and to understand concepts about the shell-specific scripting language (for example, bash), while graphical shells place a low burden on beginning computer users and are characterized as being easy to use, yet most GUI-enabled operating systems also provide CLI shells, normally for performing advanced tasks. Overview Operating systems provide various services to their users, including file management, process management (running and terminating applications), batch processing, and operating system monitoring and con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Corporation
A shell corporation is a company or corporation that exists only on paper and has no office and no employees, but may have a bank account or 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 regularly for tax evasion, tax avoidance, money laundering, or to achieve a specific goal such as anonymity. Anonymity may be sought to shield personal assets from others, such as a spouse when a marriage is breaking down, from creditors, or from government authorities. Shell companies can have legitimate business purposes. They may, for example, act as trustee for a trust, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
