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Filtering
Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component that performs some operation on a multimedia stream * Email filtering, the processing of email to organize it according to specified criteria * Content-control software also known as an Internet filter * Wordfilter, a script typically used on Internet forums or chat rooms * Berkeley Packet Filter, filter expression used in the qualification of network data * DSL filter, a low-pass filter installed between analog devices and a telephone line * Helicon Filter, a raster graphics editor * Filter (large eddy simulation), a mathematical operation intended to remove a range of small scales from the solution to the Navier-Stokes equations * Kalman filter, an approximating algorithm in optimal control applications and problems Device * Filter (chem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kalman Filter
For statistics and control theory, Kalman filtering, also known as linear quadratic estimation (LQE), is an algorithm that uses a series of measurements observed over time, including statistical noise and other inaccuracies, and produces estimates of unknown variables that tend to be more accurate than those based on a single measurement alone, by estimating a joint probability distribution over the variables for each timeframe. The filter is named after Rudolf E. Kálmán, who was one of the primary developers of its theory. This digital filter is sometimes termed the ''Stratonovich–Kalman–Bucy filter'' because it is a special case of a more general, nonlinear filter developed somewhat earlier by the Soviet mathematician Ruslan Stratonovich. In fact, some of the special case linear filter's equations appeared in papers by Stratonovich that were published before summer 1960, when Kalman met with Stratonovich during a conference in Moscow. Kalman filtering has numerous tech ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Content-control Software
An Internet filter is software that restricts or controls the content an Internet user is capable to access, especially when utilized to restrict material delivered over the Internet via the Web, Email, or other means. Content-control software determines what content will be available or be blocked. Such restrictions can be applied at various levels: a government can attempt to apply them nationwide (see Internet censorship), or they can, for example, be applied by an Internet service provider to its clients, by an employer to its personnel, by a school to its students, by a library to its visitors, by a parent to a child's computer, or by an individual users to their own computers. The motive is often to prevent access to content which the computer's owner(s) or other authorities may consider objectionable. When imposed without the consent of the user, content control can be characterised as a form of internet censorship. Some content-control software includes time control func ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Email Filtering
Email filtering is the processing of email to organize it according to specified criteria. The term can apply to the intervention of human intelligence, but most often refers to the automatic processing of messages at an SMTP server, possibly applying anti-spam techniques. Filtering can be applied to incoming emails as well as to outgoing ones. Depending on the calling environment, email filtering software can reject an item at the initial SMTP connection stage or pass it through unchanged for delivery to the user's mailbox. It is also possible to redirect the message for delivery elsewhere, quarantine it for further checking, modify it or 'tag' it in any other way. Motivation Common uses for mail filters include organizing incoming email and removal of spam and computer viruses. Mailbox providers filter outgoing email to promptly react to spam surges that may result from compromised accounts. A less common use is to inspect outgoing email at some companies to ensure that emplo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filtering Problem (stochastic Processes)
In the theory of stochastic processes, filtering describes the problem of determining the state of a system from an incomplete and potentially noisy set of observations. While originally motivated by problems in engineering, filtering found applications in many fields from signal processing to finance. The problem of optimal non-linear filtering (even for the non-stationary case) was solved by Ruslan L. Stratonovich (1959, 1960), see also Harold J. Kushner's work and Moshe Zakai's, who introduced a simplified dynamics for the unnormalized conditional law of the filter known as Zakai equation. The solution, however, is infinite-dimensional in the general case. Certain approximations and special cases are well understood: for example, the linear filters are optimal for Gaussian random variables, and are known as the Wiener filter and the Kalman-Bucy filter. More generally, as the solution is infinite dimensional, it requires finite dimensional approximations to be implemented in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter (large Eddy Simulation)
Filtering in the context of large eddy simulation (LES) is a mathematical operation intended to remove a range of small scales from the solution to the Navier-Stokes equations. Because the principal difficulty in simulating turbulent flows comes from the wide range of length and time scales, this operation makes turbulent flow simulation cheaper by reducing the range of scales that must be resolved. The LES filter operation is low-pass, meaning it filters out the scales associated with high frequencies. Homogeneous filters Definition in physical space The low-pass filtering operation used in LES can be applied to a spatial and temporal field, for example \phi(\boldsymbol,t). The LES filter operation may be spatial, temporal, or both. The filtered field, denoted with a bar, is defined as: : \overline = \displaystyle \int_^ \phi(\boldsymbol,t^) G(\boldsymbol-\boldsymbol,t - t^) dt^ d \boldsymbol, where G is a convolution kernel unique to the filter type used. This can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter (chemistry)
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as ''oversize'' and the fluid that passes through is called the ''filtrate''. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as ''blinding''. The size of the largest particles that can successfully pass through a filter is called the effective ''pore size'' of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. Filtration is al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter (higher-order Function)
In functional programming, filter is a higher-order function that processes a data structure (usually a list) in some order to produce a new data structure containing exactly those elements of the original data structure for which a given predicate returns the boolean value true. Example In Haskell, the code example filter even ..10 evaluates to the list 2, 4, …, 10 by applying the predicate even to every element of the list of integers 1, 2, …, 10 in that order and creating a new list of those elements for which the predicate returns the boolean value true, thereby giving a list containing only the even members of that list. Conversely, the code example filter (not . even) ..10 evaluates to the list 1, 3, …, 9 by collecting those elements of the list of integers 1, 2, …, 10 for which the predicate even returns the boolean value false (with . being the function composition operator). Visual example Below, you can see a view of each step of the filter process f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley Packet Filter
The Berkeley Packet Filter (BPF) is a technology used in certain computer operating systems for programs that need to, among other things, analyze network traffic. It provides a raw interface to data link layers, permitting raw link-layer packets to be sent and received. In addition, if the driver for the network interface supports promiscuous mode, it allows the interface to be put into that mode so that all packets on the network can be received, even those destined to other hosts. BPF supports filtering packets, allowing a userspace process to supply a filter program that specifies which packets it wants to receive. For example, a tcpdump process may want to receive only packets that initiate a TCP connection. BPF returns only packets that pass the filter that the process supplies. This avoids copying unwanted packets from the operating system kernel to the process, greatly improving performance. The filter program is in the form of instructions for a virtual machine, which are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel Filter
A fuel filter is a filter used to screens out foreign particles or liquids from the fuel. Most internal combustion engines use a fuel filter, in order to protect the components in the fuel system. Filters for foreign particles Unfiltered fuel may contain several kinds of contamination, for example paint chips and dirt that has entered the fuel tank while filling, or rust caused by moisture in a steel tank. If these substances are not removed before the fuel enters the system, they will cause rapid wear and failure of the fuel pump and injectors. The filters are normally made into cartridges containing a filter paper. Fuel filters need to be maintained or replaced at regular intervals. Filters for foreign liquids Some diesel engines use a bowl-like design to collect water in the bottom of the filter (as diesel floats on top of water). The water can then be drained off by opening a valve in the bottom of the bowl and letting it run out, until only the fuel remains. See also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filtration (wine)
In winemaking, clarification and stabilization are the processes by which insoluble matter suspended in the wine is removed before bottling. This matter may include dead yeast cells ( lees), bacteria, tartrates, proteins, pectins, various tannins and other phenolic compounds, as well as pieces of grape skin, pulp, stems and gums.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition, pp. 173, 661–62. Oxford University Press 2006 . Clarification and stabilization may involve fining, filtration, centrifugation, flotation, refrigeration, pasteurization, and/or barrel maturation and racking. Clarifying wine In wine tasting, a wine is considered " clear" when there are no visible particles suspended in the liquid and, especially in the case of white wines, when there is some degree of transparency. A wine with too much suspended matter will appear cloudy and dull, even if its aroma and flavor are unaffected; wines therefore generally undergo some kind of clarificati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sieve
A sieve, fine mesh strainer, or sift, is a device for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet material. The word ''sift'' derives from ''sieve''. In cooking, a sifter is used to separate and break up clumps in dry ingredients such as flour, as well as to aerate and combine them. A strainer (see Colander), meanwhile, is a form of sieve used to separate suspended solids from a liquid by filtration. Industrial strainer Some industrial strainers available are simplex basket strainers, duplex basket strainers, T-strainers and Y-strainers. Simple basket strainers are used to protect valuable or sensitive equipment in systems that are meant to be shut down temporarily. Some commonly used strainers are bell mouth strainers, foot valve strainers, basket strainers. Most processing industries (mainly pharmaceutical, coatings and liquid food indu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
