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P.F. Cuttin'
PF may refer to: Arts and entertainment * Pianoforte, full original name of the piano instrument * Project Fanboy, a comic book news website Businesses * PF Flyers, a brand of shoes * Palestinian Airlines (IATA airline designator), a defunct airline * Pell Frischmann, a multi-disciplinary engineering consultancy Economics and finance * Point and figure chart in the technical analysis of securities * Pfennig, a unit of currency formerly used in Germany, symbol ₰ * Provident Fund (other), name of various pension funds Language * Phonetic form, a level of syntactic representation in linguistics * Voiceless labiodental affricate (⟨p̪͡f⟩, ⟨p̪͜f⟩, or ⟨p̪f⟩), a type of consonant sound * Pf (digraph), a German digraph People * Phineas Flynn Organizations * Pheasants Forever, a non-profit habitat conservation organization * Federal Police (''Polícia Federal''), in Brazil * Patients' Front, a late 1960s to early 1970s West German pro-illness movement * So ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pianoforte
The piano is a stringed keyboard instrument in which the strings are struck by wooden hammers that are coated with a softer material (modern hammers are covered with dense wool felt; some early pianos used leather). It is played using a keyboard, which is a row of keys (small levers) that the performer presses down or strikes with the fingers and thumbs of both hands to cause the hammers to strike the strings. It was invented in Italy by Bartolomeo Cristofori around the year 1700. Description The word "piano" is a shortened form of ''pianoforte'', the Italian term for the early 1700s versions of the instrument, which in turn derives from ''clavicembalo col piano e forte'' (key cimbalom with quiet and loud)Pollens (1995, 238) and ''fortepiano''. The Italian musical terms ''piano'' and ''forte'' indicate "soft" and "loud" respectively, in this context referring to the variations in volume (i.e., loudness) produced in response to a pianist's touch or pressure on the keys: the grea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paracel Islands
The Paracel Islands, also known as the Xisha Islands () and the Hoang Sa Archipelago ( vi, Quần đảo Hoàng Sa, lit=Yellow Sand Archipelago), are a disputed archipelago in the South China Sea. The archipelago includes about 130 small coral islands and reefs, most grouped into the northeastern Amphitrite Group or the western Crescent Group. They are distributed over a maritime area of around , with a land area of approximately . The name ''Paracel'' is of Portuguese origin, and appears on 16th-century Portuguese maps. The archipelago is approximately equidistant from the coastlines of the People's Republic of China (PRC) and Vietnam, and approximately one-third of the way from central Vietnam to the northern Philippines. The archipelago includes Dragon Hole, the deepest underwater sinkhole in the world. Turtles and seabirds are native to the islands, which have a hot and humid climate, abundant rainfall and frequent typhoons. The archipelago is surrounded by productive fishin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenylphosphine
Phenylphosphine is an organophosphorus compound with the chemical formula C6H5PH2. It is the phosphorus analog of aniline. Like other primary phosphines, phenylphosphine has an intense penetrating odor and is highly oxidizable. It is mainly used as a precursor to other organophosphorus compounds. It can function as a ligand in coordination chemistry. Synthesis Phenylphosphine can be produced by reducing dichlorophenylphosphine with lithium aluminum hydride in ether: :LiAlH4 + 2C6H5PCl2 → 2C6H5PH2 + Li+ + Al3+ + 4Cl− This reaction is performed under a nitrogen atmosphere to prevent side reactions involving oxygen. Reactions Oxidation of phenylphosphine with air affords the oxide. :C6H5PH2 + O2 → C6H5P(OH)2 Bis(2-cyanoethylphenyl)phosphine, which is of interest as a synthetic intermediate, can be made from phenylphosphine by base-catalyzed allylic addition to acrylonitrile. :C6H5PH2 + 2CH2=CHCN → C6H5P(CH2CH2CN)2 Bis(2-cyanoethylphenyl)phosphine is a useful precursor to 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pfaffian
In mathematics, the determinant of a skew-symmetric matrix can always be written as the square of a polynomial in the matrix entries, a polynomial with integer coefficients that only depend on the size of the matrix. The value of this polynomial, when applied to the coefficients of a skew-symmetric matrix, is called the Pfaffian of that matrix. The term Pfaffian was introduced by who indirectly named them after Johann Friedrich Pfaff. The Pfaffian (considered as a polynomial) is nonvanishing only for 2''n'' × 2''n'' skew-symmetric matrices, in which case it is a polynomial of degree ''n''. Explicitly, for a skew-symmetric matrix A, : \operatorname(A)^2=\det(A), which was first proved by , who cites Carl Gustav Jacob Jacobi, Jacobi for introducing these polynomials in work on Pfaffian system, Pfaffian systems of differential equations. Caley obtains this relation by specialising a more general result on matrices which deviate from skew symmetry only in the first row and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon Factory
The Photon Factory (PF) is a synchrotron located at KEK, in Tsukuba, Japan, about fifty kilometres from Tokyo. There are two major facilities, the Photon Factory itself which is a 2.5GeV synchrotron with a beam current of around 450mA, and the PF-AR 'Advanced Ring for Pulsed X-Rays', which is a 6.5GeV machine running in a single-bunch mode with a beam current of around 60mA. Its macromolecular crystallography beamline is used substantially for Japan's structural genomics Structural genomics seeks to describe the 3-dimensional structure of every protein encoded by a given genome. This genome-based approach allows for a high-throughput method of structure determination by a combination of experimental and modeling ... project. External linksPhoton Factory - KEK IMSS website Synchrotron radiation facilities {{particle-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Farad
The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base units 1 F = 1 kg−1⋅ m−2⋅ s4⋅ A2. Definition The capacitance of a capacitor is one farad when one coulomb of charge changes the potential between the plates by one volt. Equally, one farad can be described as the capacitance which stores a one-coulomb charge across a potential difference of one volt. The relationship between capacitance, charge, and potential difference is linear. For example, if the potential difference across a capacitor is halved, the quantity of charge stored by that capacitor will also be halved. For most applications, the farad is an impractically large unit of capacitance. Most electrical and electronic applications are covered by the following SI prefixes: *1 mF (millifarad, one thousandth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenol Formaldehyde Resin
Phenol formaldehyde resins (PF) or phenolic resins (also infrequently called phenoplasts) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial synthetic resins (plastics). They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth, as with fire-resistant FR-4 circuit board materials. There are two main production methods. One reacts phenol and formaldehyde directly to produce a thermosetting network polymer, while the other restricts the formaldehyde to produce a prepolymer known as novolac which can be moulded and then cured with the addition of more formaldehyde and heat.A. Gardziella, L.A. Pilato, A. Knop, Phenolic Resins: Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purple Fringing
In photography (particularly digital photography), purple fringing (sometimes called PF) is the term for an unfocused purple or magenta "ghost" image on a photograph. This optical aberration is generally most visible as a coloring and lightening of dark edges adjacent to bright areas of broad-spectrum illumination, such as daylight or various types of gas-discharge lamps. Lenses in general exhibit axial chromatic aberration, in which different colors of light do not focus in the same plane. Normally, lens designs are optimized so that two or more (at least three for apochromatic lenses) wavelengths of light in the visible spectrum focus at the same plane. Wavelengths very different from those optimized in the design process may be severely out of focus while the reference colors are in focus; this axial chromatic aberration is usually severe at short wavelengths (violet). Lens performance may be poor for such wavelengths in other ways too, including an increase in flare due to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Factor
In electrical engineering, the power factor of an AC power system is defined as the ratio of the '' real power'' absorbed by the load to the ''apparent power'' flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of RMS current and voltage. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power, so more current flows in the circuit than would be required to transfer real power alone. A power factor magnitude of less than one indicates the voltage and current are not in phase, reducing the average product of the two. A negative power factor occurs when the device (which is normally the load) generates real power, which then flows back towards the source. In an electric power system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page File
In computer operating systems, memory paging is a memory management scheme by which a computer stores and retrieves data from secondary storage for use in main memory. In this scheme, the operating system retrieves data from secondary storage in same-size blocks called ''pages''. Paging is an important part of virtual memory implementations in modern operating systems, using secondary storage to let programs exceed the size of available physical memory. For simplicity, main memory is called "RAM" (an acronym of random-access memory) and secondary storage is called "disk" (a shorthand for hard disk drive, drum memory or solid-state drive, etc.), but as with many aspects of computing, the concepts are independent of the technology used. Depending on the memory model, paged memory functionality is usually hardwired into a CPU/MCU by using a Memory Management Unit (MMU) or Memory Protection Unit (MPU) and separately enabled by privileged system code in the operating system's k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page Fault
In computing, a page fault (sometimes called PF or hard fault) is an exception that the memory management unit (MMU) raises when a process accesses a memory page without proper preparations. Accessing the page requires a mapping to be added to the process's virtual address space. Besides, the actual page contents may need to be loaded from a backing store, such as a disk. The MMU detects the page fault, but the operating system's kernel handles the exception by making the required page accessible in the physical memory or denying an illegal memory access. Valid page faults are common and necessary to increase the amount of memory available to programs in any operating system that uses virtual memory, such as Windows, macOS, and the Linux kernel. Types Minor If the page is loaded in memory at the time the fault is generated, but is not marked in the memory management unit as being loaded in memory, then it is called a minor or soft page fault. The page fault handler in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PF Keys
A function key is a key on a computer or terminal keyboard that can be programmed so as to cause an operating system command interpreter or application program to perform certain actions, a form of soft key. On some keyboards/computers, function keys may have default actions, accessible on power-on. Function keys on a terminal may either generate short fixed sequences of characters, often beginning with the escape character (ASCII 27), or the characters they generate may be configured by sending special character sequences to the terminal. On a standard computer keyboard, the function keys may generate a fixed, single byte code, outside the normal ASCII range, which is translated into some other configurable sequence by the keyboard device driver or interpreted directly by the application program. Function keys may have abbreviations or pictographic representations of default actions printed on/besides them, or they may have the more common "F-number" designations. History T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
