assumptions on the computationalhardness are stronger than others. Note that if assumption A is stronger than assumption B, that means solving the problem underlying assumption B is polytime reducible to solving the problem underlying assumption A which means that if B is solvable in poly time, A definitely ... Naccache Stern cryptosystem Phi hiding assumption stronger than factorization Cachin Micali Stadler Private information retrieval PIR Discrete log problem DLP Computational Diffie Hellman assumption CDH stronger than DLP Diffie Hellman key exchange Decisional Diffie Hellman assumption DDH stronger than CDH ElGamal encryption Non cryptographic hardness assumptions As well as their cryptographic applications, hardness assumptions are used in computational complexity theory to provide evidence ... proves that the hardnessassumption implies some desired complexity theoretic statement, instead of proving that the statement is itself true. The best known assumption of this type is the assumption .... Because hardness of a problem is difficult to prove, in practice certain problems are assumed to be difficult. Common cryptographic hardness assumptions There are many common cryptographic hardness ... common cryptographic hardness assumptions, and some cryptographic protocols that use them. Integer ... Goldwasser Micali cryptosystem Decisional composite residuosity assumption stronger than factorization ... contribution On the Unique Games Conjecture title Proc. 25th IEEE Conference on Computational Complexity ... . ref References reflist Category Theory of cryptography Category Computational number theory ar ... more details
The computational Diffie Hellman CDH assumption is the assumption that a certain computational problem within a cyclic group is hard. Consider a cyclic group G of order q . The CDH assumption states that, given math g,g a,g b , math for a randomly chosen generator g and random math a,b in 0, ldots, q 1 , , math it is computationally intractable to compute the value math g ab . , math The security of many cryptosystem s is based on the CDH assumption, including notably the Diffie Hellman key agreement scheme. Also, the confidentiality of ElGamal encryption is equivalent to the CDH assumption though the semantic security of the scheme is based on the decisional Diffie Hellman assumption . The CDH assumption is related to the discrete logarithm assumption , which holds that computing the discrete logarithm of a value base a generator math g math is hard. If taking discrete logs in math mathbb G math were easy, then the CDH assumption would be false given math g,g a,g b , , math one could efficiently compute math g ab math in the following way compute math a math by taking the discrete log of math g a math to base math g math compute math g ab math by exponentiation math g ab g b a math It is an open problem to determine whether the discrete log assumption is equivalent to CDH, though in certain special cases this can be shown to be the case. The CDH assumption is also related to the decisional Diffie Hellman assumption DDH , which holds that it is hard to distinguish tuples of the form math g,g a,g b,g ab math from random tuples. If computing math g ab math from math g,g a,g b math were easy, then one could detect DDH tuples trivially. It is believed that CDH is a weaker assumption than DDH there are groups for which detecting DDH tuples is easy, but solving CDH problems is believed to be hard. See also Diffie Hellman problem Diffie Hellman key exchange References Variations ... PDF C94 271.PDF pdf file Category Computationalhardness assumptions ... more details
About mechanical properties of materials Hard disambiguation Hard Hardness is the measure of how resistant ... hardness is generally characterized by strong intermolecular bond s, but the behavior of solid materials under force is complex therefore, there are different measurements of hardness scratch hardness , indentation hardness , and rebound hardness . Hardness is dependent on ductility , Elasticity physics ... matter . Measuring hardness Image Vickers tester.png thumb A Vickers hardness tester There are three main types of hardness measurements scratch , indentation , and rebound . Within each of these classes of measurement there are individual measurement scales. For practical reasons hardness comparison conversion tables are used to convert between one scale and another. Scratch hardness Anchor Scratch hardness Scratch hardness is the measure of how resistant a sample is to fracture or permanent ... hardness main Indentation hardness Indentation hardness measures the resistance of a sample to permanent ... hardness scales are Rockwell scale Rockwell , Vickers hardness test Vickers , Shore scale Shore , and Brinell hardness test Brinell . Rebound hardness Rebound hardness, also known as dynamic hardness ... a material. This type of hardness is related to elasticity physics elasticity . The device used ... to rebound hardness and scleroscope test date 2006 12 10 url http www.articlestree.com science a guide to rebound hardness and scleroscope test tx301428.html accessdate 2008 09 08 postscript . ref Two scales that measures rebound hardness are the Leeb rebound hardness test and Bennett hardness scale ... shape when the pressure is removed. Hardness in the elastic range a small temporary change in shape ... properties of scratch and indentation hardness, as described and measured in materials science. Some ... to absorb large amounts of energy. Hardness increases with decreasing particle size . This is known as the Hall Petch relationship . However, below a critical grain size, hardness decreases with decreasing ... more details
Hardness scales may refer to Methods of measuring mineral hardness Mohs scale of mineral hardness The Vickers hardness test The Brinell scale The Janka hardness test The Rockwell scale Hardness scales may also refer to deposits formed by hard water . Disambig ... more details
wiktionary assumption In logic an assumption is a proposition that is taken for granted, as if it were truth true based upon presupposition without preponderance of the facts. An assumption that is considered to be self evident or otherwise fundamental is called an axiom . In religion, assumption is the bodily translation of an individual person, either living or dead, from earth to heaven . Assumption of Mary , a religious account of the taking up of Mary into heaven Assumption of Moses , a Jewish apocryphal pseudepigraphical work of uncertain date and authorship Entering heaven alive Assumption may also refer to In logic, more specifically in the context of natural deduction systems, an assumption is a proposition that may be used to prove further propositions, in the expectation that the assumption ... ling can be used to map the outcome of different assumptions on the system being modelled. Assumption ... and becomes directly liable for policy claims In real property law , an assumption is the mortgage loan mortgage transfer from the seller to the buyer In business planning and business plans, an assumption ... or plans of an organization Assumption Poker , a fictional type of poker variation, using Tarot cards. It appears in the novel Last Call by Tim Powers . Concepts Responsibility assumption , a doctrine ... responsibility for the events and circumstances that befall them in their life Locations Assumption, Alberta , Canada Assumption, Illinois , USA Assumption, Ohio , USA Assumption Cathedral disambiguation Assumption Island , Seychelles Assumption Parish , Louisiana, USA L Assomption River , Quebec, Canada Schools Assumption Antipolo , Philippines Assumption Junior Senior High School , Cold Lake, Alberta Assumption High School Indiana Assumption High School Davenport, Iowa Assumption High School Louisville, Kentucky Assumption High School Louisiana , Napoleonville, Louisiana Assumption Iloilo , Iloilo City, Philippines Assumption College , Worcester, Massachusetts Assumption Preparatory School ... more details
In computer science , hardness of approximation is a field that studies the algorithmic complexity of finding near optimal solutions to optimization problem s. It complements the study of approximation algorithm s by proving, for certain problems, a limit on the factors with which their solution can be efficiently approximated. Typically such limits show a factor of approximation beyond which a problem becomes NP hard , implying that finding a polynomial time approximation for the problem is impossible unless NP P . Some hardness of approximation results, however, are based on other hypotheses, a notable one among which is the unique games conjecture . Since the early 1970s it was known that many optimization problems could not be solved in polynomial time unless NP P , but in many of these problems the optimal solution could be efficiently approximated to a certain degree. In the early 1990s, with the development of PCP complexity PCP theory, it became clear that there is a limit to the approximability of many of these optimization problems for many optimization problems there is a threshold beyond which they are NP hard to approximate. Hardness of approximation theory deals with studying the approximation threshold of such problems. Examples For an example of an NP hard optimization problem that is hard to approximate, see set cover . See also PCP theorem Further reading http www.cs.berkeley.edu luca pubs inapprox.ps Survey, a good starter by Luca Trevisan External links http www.cs.washington.edu education courses 533 05au CSE 533 The PCP Theorem and Hardness of Approximation, Autumn 2005 , syllabus from the University of Washington , Venkatesan Guruswami and Ryan O Donnell Category Computational complexity theory Category Mathematical optimization comp sci theory stub ... more details
Indentation hardness tests are used to determine the hardness of a material to deformation. Several such tests ... can be performed on a macroscopic or microscopic scale. When testing metals, indentation hardness correlates ... held Rockwell hardness testers. ref http www.springerlink.com content q86642448t84g267 Correlation of Yield Strength and Tensile Strength with Hardness for Steels , E.J. Pavlina and C.J. Van Tyne, Journal of Materials Engineering and Performance, Volume 17, Number 6 December, 2008 ref Material hardness ... material hardness by indenting a material with an impression have been developed to determine such properties. Hardness measurements quantify the resistance of a material to plastic deformation. Indentation hardness tests compose the majority of processes used to determine material hardness, and can ... have forces less than convert 2 N abbr on . Hardness, however, cannot be considered to be a fundamental ... , 162 168. ref As such, hardness can only offer a comparative idea of the material s resistance to plastic deformation since different hardness techniques have different scales. The main source ... experimentally determined through strainless hardness tests that the effect is minimal with smaller ... on the hardness measurement, as long as the indentation is large compared to the surface roughness. This proves to be useful when measuring the hardness of practical surfaces. It also is helpful ... is annealed it will sink in around the indentation. Both of these effects add to the error of the hardness measurement. ref Tabor, p. 15. ref The equation based definition of hardness is the pressure applied over the contact area between the indenter and the material being tested. As a result hardness ... kgf or more. There are various macroindentation tests, including Vickers hardness test HV , which has one of the widest scales Brinell hardness test HB Knoop hardness test HK , for measurement over small areas Janka hardness test , for wood Meyer hardness test Rockwell scale Rockwell ... more details
Merge Carbonate alkalinity date November 2011 Carbonate hardness , or carbonate alkalinity is a measure of the alkalinity of water caused by the presence of carbonate CO sub 3 sub sup 2 sup and bicarbonate HCO sub 3 sub sup sup anions . It is usually expressed either as parts per million Parts per million ppm or Gram per litre mg L , or in degrees KH from the German Karbonathä rte . One German degree of carbonate hardness dKH corresponds to the carbonate and bicarbonate ions found in a solution of approximately 17.848 milligrams of calcium carbonate CaCO sub 3 sub per litre of water 17.848 ppm . Both measurements mg L or KH are usually expressed as CaCO sub 3 sub &ndash meaning the concentration of carbonate expressed as if calcium carbonate were the sole source of carbonate ions. Bicarbonate ions only contribute half as much carbonate hardness as carbonate ions, so bicarbonates that are present in the water are converted to an equivalent concentration of carbonates when determining KH. For example An aqueous solution containing 120 mg Sodium Bicarbonate NaHCO sub 3 sub baking soda per litre of water will contain 1.4285 mmol L of bicarbonate, since the molar mass of baking soda is 84.007 g mol. This is equivalent in carbonate hardness to a solution containing 0.71423 mmol L of calcium carbonate, or 71.485 mg L of calcium carbonate molar mass 100.09 g mol . Since one degree KH 17.848 mg L CaCO sub 3 sub , this solution has a KH of 4.0052 degrees. The term carbonate hardness is also sometimes used as a synonym for Hard water Temporary hardness temporary hardness , in which case it refers to that portion of hard water that can be water softening removed by processes such as boiling or lime softening , and then separation of water from the resulting precipitate. ref cite web title Lime Softening url http water.me.vccs.edu concepts softeninglime.html ... http www.thekrib.com Plants CO2 hardness larryfrank.html Water Hardness definitions Category Carbonates ... more details
Infobox Album Name The Hardness Of The World Type Studio Artist Slave band Slave Cover Released 1977 Recorded 1977 small at House Of Music, West Orange, New Jersey small Genre Soul music Soul Funk music funk Length Label Cotillion Records Producer Jeff Dixon Slave band Slave Last album Slave Slave album Slave br 1977 This album The Hardness Of The World br 1977 Next album The Concept br 1978 Album ratings rev1 Allmusic rev1Score Rating 4 5 ref Allmusic class album id r49517 tab review label Slave The Hardness of the World Review first Craig last Lytle accessdate 30 August 2011 ref The Hardness Of The World is the second album by the United States American funk music funk band Slave band Slave , the second album released by the band in 1977. The album reached number 22 on the Billboard Hot R&B Hip Hop Songs Hot Soul Singles chart. Track listing Life Can Be Happy 4 16 The Great American Funk Song 3 50 Can t Get Enough Of You 4 07 Baby Sinister 6 45 The World s On Hard 3 26 The Party Song 4 07 We Can Make Love 5 28 Volcano Rupture 6 23 Charts class wikitable Chart 1978 Peak br position Billboard 200 Billboard Pop Albums ref name allmusic albums Cite web url Allmusic class artist id p5452 charts awards billboard albums pure url yes title Slave US albums chart history publisher allmusic.com accessdate 2011 08 30 ref align center 67 Billboard Top R&B Hip Hop Albums Top Soul Albums ref name allmusic albums align center 31 Singles class wikitable style text align center rowspan 2 Year rowspan 2 Single colspan 3 Chart positions ref name allmusic singles Cite web url Allmusic class artist id p5452 charts awards billboard singles pure url yes title Slave US singles chart history publisher allmusic.com accessdate 2011 08 30 ref style font size smaller width 40 Billboard Hot 100 width ... Sinister &mdash 74 References Reflist External links http www.discogs.com Slave The Hardness Of The World master 155496 Slave The Hardness Of The World at Discogs DEFAULTSORT Hardness of the World Category ... more details
citation.cfm?id 647086.715689 Category Computationalhardness assumptions Category Elliptic ...The external Diffie&ndash Hellman XDH assumption is a mathematic assumption used in elliptic curve cryptography . The XDH assumption holds that there exist certain subgroup s of elliptic curves which have useful properties for cryptography. Specifically, XDH implies the existence of two distinct Group mathematics groups math langle mathbb G 1, mathbb G 2 rangle math with the following properties The discrete logarithm problem DLP , the computational Diffie&ndash Hellman assumptioncomputational Diffie&ndash Hellman problem CDH , and the computational co Diffie&ndash Hellman assumptioncomputational co Diffie&ndash Hellman problem are all intractable in math mathbb G 1 math and math mathbb G 2 math . There exists an efficiently computable bilinear map pairing math e cdot, cdot mathbb G 1, mathbb G 2 rightarrow mathbb G T math . The decisional Diffie&ndash Hellman assumption decisional Diffie&ndash Hellman problem DDH is intractable in math mathbb G 1 math . The above formulation is referred to as asymmetric XDH . A stronger version of the assumption symmetric XDH , or SXDH holds if decisional Diffie&ndash Hellman assumption DDH is also intractable in math mathbb G 2 math . The XDH assumption is used in some pairing based cryptography pairing based cryptographic protocols. In certain ... for practical solutions to the decisional Diffie&ndash Hellman assumption DDH problem. These groups ... encryption Elgamal within a GDH group. Because the DDH assumption holds within at least one of a pair ... assumption may hold in certain subgroups of MNT curve MNT elliptic curves. This notion was first ... the efficiency of a signature scheme. The assumption was formally defined by Ballard, Green, de Medeiros .... Evidence for the validity of this assumption is the proof by Verheul 2001 and Galbraith and Rotger ... to solve the DDH problem in elliptic curve groups, it is believed that the DDH assumption therefore ... more details
The decisional composite residuosity assumption DCRA is a mathematical assumption used in cryptography . In particular, the assumption is used in the proof of the Paillier cryptosystem . Informally the DCRA states that given a composite number composite n and an integer z , it is hard to decide whether z is a n residue modular arithmetic modulo n sup 2 sup or not, i.e., whether there exists y such that math z equiv y n pmod n 2 . , math See also Computationalhardnessassumption Quadratic residuosity problem Higher residuosity problem References P. Paillier, Public Key Cryptosystems Based on Composite Degree Residuosity Classes , Eurocrypt 1999. DEFAULTSORT Decisional Composite Residuosity Assumption Category Computationalhardness assumptions ... more details
Assumption University may refer to Assumption University Windsor Assumption University Thailand University of the Assumption , Philippines schooldis Long comment to avoid being listed on short pages de Assumption University nl Assumption University ... more details
Image Meyer hardness test vs brinell hardness test.png thumb 400px This graph shows the differences between the Brinell hardness test and the Meyer hardness test. Notice that the Brinell test can report the same hardness value for a given specimen twice depending on the load. The Meyer hardness test is a rarely used hardness test based upon projected area of an impression. This is a more fundamental measurement of hardness than other hardness tests which are based on the surface area of an indentation. The principle behind the test is that the mean pressure required to test the material is the measurement of the hardness of the material. The mean pressure is calculated by dividing the load by the projected area of the indentation. The result is called the Meyer hardness, which has units of Pascal pressure megapascals MPa . ref name kts Citation title Hardness Testing url http www.keytometals.com page.aspx?ID CheckArticle&site kts&NM 140 accessdate 2008 10 07 . ref An advantage of the Meyer test is that it is less sensitive to the applied load, especially compared to the Brinell scale Brinell hardness test . For cold work ed materials the Meyer hardness is relatively constant and independent of load, whereas for the Brinell hardness test it decreases with higher loads. For Annealing metallurgy anneal ed materials the Meyer hardness increases continuously with load due to strain hardening. ref name kts Based on Meyer s law hardness values from this test can be converted into Brinell scale Brinell hardness values, and vice versa. ref Tabor, p. 10. ref See also multicol Brinelling Hardness comparison Knoop hardness test multicol break Leeb Rebound Hardness Test Rockwell scale Vickers hardness test multicol end References reflist Bibliography Citation last Tabor first David title The Hardness of Metals publisher Oxford University Press year 2000 url http books.google.com ?id b 9LdJ5FHXYC isbn 0198507763 . Category Hardness tests mech engineering stub ... more details
In theoretical computer science , a computational problem is a mathematical object representing a collection of questions that computers might want to solve. For example, the problem of factoring Given a positive integer n , find a nontrivial prime factor of n . is a computational problem. Computational problems are one of the main objects of study in theoretical computer science. The field of algorithms studies methods of solving computational problems efficiently. The complementary field of computational complexity attempts to explain why certain computational problems are intractable for computers. A computational problem can be viewed as an infinite collection of instances together with a solution for every instance. For example in the factoring problem, the instances are the integers n , and solutions are prime numbers p that describe nontrivial prime factors of n . It is conventional to represent both instances and solutions by binary String computer science strings , namely elements of 0, 1 sup sup . For example, numbers can be represented as binary strings using the binary encoding ... of computational problems A decision problem is a computational problem where the answer for every ... there is sorted out Promise problems In computational complexity theory , it is usually implicitly assumed that any string in 0, 1 sup sup represents an instance of the computational problem ... a proper subset of 0, 1 sup sup as the set of valid instances . Computational problems of this type ... and no , respectively. Promise problems play an important role in several areas of computational complexity , including hardness of approximation , property testing , and interactive proof system s. References ... 9958 84 80056 X . citation first1 Oded last1 Goldreich author1 link Oded Goldreich title Computational ... author2 link Avi Wigderson contribution IV.20 Computational Complexity pages 575 604 title The Princeton ... Imre Leader year 2008 publisher Princeton University Press isbn 9780691118802 . Category Computational ... more details
Economics sidebar Computational economics is a research discipline at the interface between computer science and economic and management science . ref name compecon Computational Economics . http www.springer.com ... include computational modeling of economic systems , whether agent based computational economics agent ... article?id pde2008 C000573&q computational 20economics&topicid &result number 3 Abstract. br ... article?id pde2008 C000564&q computational 20economics&topicid &result number 2 Abstract . ref .... Handbook of Computational Economics , v. 1, ch. 1 6, preview http www.sciencedirect.com science ... rational expectations , ref Ray C. Fair Computational Methods for Macroeconometric Models, Hans M. Amman, David A. Kendrick, and John Rust, ed., 1996. Handbook of Computational Economics , v ... computational econometrics and statistics, ref Vassilis A. Hajivassiliou, 2008. computational methods ... , 2nd Edition. http www.dictionaryofeconomics.com article?id pde2008 D000244&edition current&q Computational ...&topicid &result number 1 Abstract. ref computational finance , computational tools for the design of automated internet economy internet market s, programming tools specifically designed for computational economics, and pedagogical tools for the teaching of computational economics. Some of these areas are unique to computational economics, while others extend traditional areas of economics by solving ... . ref Hans M. Amman, David A. Kendrick, and John Rust, ed., 1996. Handbook of Computational Economics ... 3 v onepage&q&f false chapter previews . ref Computational economics uses computer based economic ... to that end is agent based computational economics ACE , the computational study of economic .... Agent Based Computational Economics A Constructive Approach to Economic Theory, ch. 16, Handbook of Computational ... Kenneth L. Judd, 2006. Computationally Intensive Analyses in Economics, Handbook of Computational ... of Computational Economics , v. 2, Agent Based Computational Economics , Elsevier. http www.elsevier.com ... more details
The Decision Linear DLIN assumption is a mathematical assumption used in elliptic curve cryptography . In particular, the DLIN assumption is useful in settings where the decisional Diffie&ndash Hellman assumption does not hold as is often the case in pairing based cryptography . The Decision Linear assumption was introduced by Boneh, Boyen, and Shacham. ref Dan Boneh, Xavier Boyen, Hovav Shacham Short Group Signatures. CRYPTO 2004 41&ndash 55 ref Informally the DLIN assumption states that given math f, , g, , f x, , g y math , with math f, , g math random group elements and math x, , y math random exponents, it is hard to distinguish math h, , h x y math for random math h math from math h, , h math for independently random math h, , h math . References references Cryptography navbox public key Category Computationalhardness assumptions Category Elliptic curve cryptography Category Pairing based cryptography crypto stub ... more details
The Church of the Assumption may refer to tocright Bulgaria Church of the Assumption Uzundzhovo Czech Republic Church of the Assumption of the Virgin Mary Most Church of the Assumption of Our Lady and Saint John the Baptist , Kutn Hora Haiti Cathedral of Our Lady of the Assumption, Port au Prince Ireland Church of the Assumption, Booterstown Latvia Assumption of Our Lady Church, Bolder ja Malaysia Church of the Assumption Penang Mexico Cathedral of Our Lady of the Assumption, Oaxaca Poland Church of the Assumption Klodzko Slovakia Assumption of Mary Church Ro ava Slovenia Church of the Assumption of the Virgin Mary and Roch Jesenice United States Holy Assumption of the Virgin Mary Church , Kenai, Alaska St. Mary s Assumption Church New Orleans, Louisiana Saint Mary of the Assumption Church, Rectory, School and Convent , Brookline, Massachusetts Assumption of the Blessed Virgin Mary Church , Detroit, Michigan Church of the Assumption Houghton Township, Michigan Church of the Assumption Phoenix, Michigan Church of the Assumption Saint Paul, Minnesota Church of the Assumption Nashville, Tennessee St. Mary of the Assumption Church , Fort Worth, Texas St. Mary s Church of the Assumption , Praha, Texas See also Our Lady of the Assumption Church disambiguation Assumption Cathedral disambiguation Dormition Church disambiguation Disambig church bg cs Kostel Nanebevzet Panny Marie de Maria Himmelfahrt Kirche es Iglesia de la Asunci n it Chiesa di Santa Maria Assunta nl Onze Lieve Vrouw Hemelvaartkerk pt Igreja de Nossa Senhora da Assun o sk Kostol Nanebovzatia Panny M rie ... more details
Assumption Cathedral or Dormition Cathedral Russian Cathedral of the dormition or Uspenski Cathedral may refer to a number of Cathedral Cathedral churches consecrated to the Dormition of the Theotokos in the Orthodox tradition and Assumption of Mary in the Roman Catholic tradition Mother churches of Russia and Ukraine The Dormition Cathedral, Vladimir , aka Assumption ... for all subsequent churches of that name The Dormition Cathedral, Moscow , aka Assumption Cathedral ... Lavra , aka Assumption Cathedral in Kiev, Ukraine 1073 78, rebuilt 1640s, destroyed 1941, rebuilt 1998 The Assumption Cathedral in Rostov date of construction disputed, the early 16th century being the most likely The Assumption Cathedral in Ryazan 1693 99 The Cathedral of the Assumption, Smolensk Assumption Cathedral in Smolensk 1677 79, 1732 40 The Assumption Cathedral in Tula 1762 64 The Assumption Cathedral in Volodymyr Volynskyi 1160, collapsed 1829, rebuilt 1900 The Assumption Cathedral in Yaroslavl 1640s, rebuilt 2000s The Assumption Cathedral in Zvenigorod 1399 The Assumption Cathedral, Kharkiv Assumption Cathedral in Kharkiv 1777 The Assumption Cathedral in Pochayiv Lavra 1783 The Assumption Cathedral in Dmitrov 1509 21 The Assumption Cathedral in Omsk 1893 1935, 2000s The Assumption Cathedral in Khabarovsk 1999 2002 The Assumption Church of Ancient Halych Krylos , Ivano Frankivsk ... churches The Assumption Cathedral, Bangkok , principal Roman Catholic church of Thailand, located in the Bang Rak district of the national capital Tuam Cathedral , aka Cathedral Church of the Assumption of the Blessed Virgin Mary, Tuam, County Galway, Ireland Cathedral of the Assumption Louisville in Louisville, Kentucky Cathedral of Saint Mary of the Assumption in San Francisco, California Cathedral of the Assumption of the Virgin formal name of the Great Mosque of Cordoba in Cordoba, Spain St ... Significance See also Our Lady of the Assumption Church disambiguation disambig cs Chr m Zesnut ... more details
The Barcol hardness test characterizes the indentation hardness of materials through the depth of penetration of an indentor, loaded on a material sample and compared to the penetration in a reference material. The method is most often used for composite material s such as reinforced thermoset thermosetting resin s or to determine how much a resin or plastic has curing chemistry cured . The test complements the measurement of glass transition temperature , as an indirect measure of the degree of cure ... Colman inventor Walter Colman as a hand held, portable means of assessing the hardness of a material ... of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing ... author Bennett, Robert B accessdate 2008 06 15 publisher Barber Colman News ref The hardness of the material ... to be read on a dial. ref name B C News Operation The Barcol hardness test is generally used on soft materials such as rigid plastics. It measures hardness based on indentation of a sharp point with a flat ... Shore hardness Shore D hardness however the Shore D indentor has a round tip. ref name Plastics ... and Processes A Concise Encyclopedia title Barcol Hardness url http books.google.com books?id oe5YJmRmxQMC&pg PA52&dq Barcol Hardness test&sig zhZZTpbsomXDcZJMIGPYTTR0Ysk accessdate 2008 02 10 publisher John Wiley and Sons ref Barcol hardness is not a valid hardness measure for curved surfaces. ref name NHML cite web url http nhml.com resources NHML Hardness Testing.php title NHML Resources Hardness ... The governing standard for the Barcol hardness test is ASTM D 2583. ref name Plastics Barcol hardness ... of 60B is roughly equivalent to a Shore hardness of 80D or a Rockwell hardness M100. ref name ... Hardness of Rigid Plastics by Means of a Barcol Impressor . ASTM International . Revision as of 2007 03 01 ref See also Brinell hardness test Knoop hardness test Rockwell scale Shore durometer Vickers hardness test Hardness comparison References Reflist Category Hardness tests ... more details
Image Vickers tester.png thumb A Vickers hardness tester The Vickers hardness test was developed in 1921 ... Brinell method to measure the hardness of materials. ref R.L. Smith & G.E. Sandland, An Accurate Method of Determining the Hardness of Metals, with Particular Reference to Those of a High Degree of Hardness ... test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The basic principle, as with all common measures of hardness, is to observe the questioned ... for all metal s and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number HV or Diamond Pyramid Hardness DPH . The hardness ..., which also has units of pascals. The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not a pressure. The hardness ... be seen in conjunction with the experimental methods and hardness scale used. Implementation Image ... indenter of a Vickers hardness tester. Image Case hardened steel vickers hardness test.png thumb An indentation left in case hardened steel after a Vickers hardness test. Notice the difference in length ... that the ideal size of a Brinell hardness test Brinell impression was 3 8 of the ball diameter. As two ... side. The angle was varied experimentally and it was found that the hardness value obtained on a homogeneous ... on the hardness of the material to be measured. The HV number is then determined by the ratio ... millimeter kgf mm . To calculate Vickers hardness number using SI units one needs to convert the force ... hardness numbers are reported as xxxHVyy , e.g. 440HV30 , or xxxHVyy zz if duration of force differs from 10 s to 15 s, e.g. 440Hv30 20, where 440 is the hardness number, HV gives the hardness ... test types hardness vickers.aspx Vickers Test . Instron website. ref class wikitable border 1 Examples ... more details
Image Application Picture Equotip.jpg thumb 300px A Leeb rebound hardness test The Leeb rebound hardness test is one of the four most used method for testing metal hardness . This portable method is mainly ... 2009 History The Leeb rebound hardness test method was developed in 1975 by Leeb and Brandestini at Proceq Proceq SA to provide a portable hardness test for metals. It was developed as an alternative to the unwieldy and sometimes intricate traditional hardness measuring equipment. The first ... rebound due to the wide circulation of the Equotip product. Traditional hardness measurements, e.g. according to Rockwell scale Rockwell , Vickers hardness test Vickers and Brinell scale Brinell ... Hardness , ICASI 2008 & CCATM 2008 congress proceedings 2008 . ref Method The traditional methods are based on well defined physical indentation hardness tests. Very hard indenters of defined geometries ..., such as the indentation depth in the Rockwell method, are recorded to give measures of hardness. ref name Kunststoffen 2007 K. Herrmann et. al., H rtepr fung an Metallen und Kunststoffen Hardness ... principle, the hardness value is derived from the energy loss of a defined impact body after impacting ... v sub i sub is quoted in the Leeb rebound hardness unit HL. ref name T. Mennicke, 2008 ref M. Tietze, M. Kompatscher, Predicative Hardness Testing for Production Control and Materials Design , IMEKO ... steel casting with a Leeb hardness of 600 HLD. By comparison, a Brinell indentation on the same material is 3 mm hardness value 400 HBW 10 3000 , with a standard compliant measuring time of 15 ... and spring force, diverse impact devices and hardness units are distinguished, e.g. Equotip impact device D with hardness unit HLD Equotip impact device G with hardness unit HLG Generally, impact ... geometries and test loads in Rockwell e.g. HRA, HRB, HRC , Brinell and Vickers. Leeb hardness results in HL are often converted to the traditional hardness scales HRC, HB and HV mainly for convention ... more details
A roll hardness tester is a device to measure the roll hardness, hardness profile and hardness variation of paper rolls. Method In the preparation phase, the plunger, guide bar and guide disk are pushed forward by the compression spring. At the end of the movement the hammer mass is hooked by the pawl. During the loading phase the hammer is pushed towards the surface in a controlled movement. The hammer mass remains locked in place by the pawl. This has the effect of stretching the impact spring to put it under tension. Impact Rebound At the very end of the movement, the pawl spring releases the hammer mass. The impact spring contracts causing the hammer mass to strike against the plunger. This is the impact. The hammer mass then rebounds back to the body of the hammer and distance travelled is recorded on the scale. The rebound distance depends directly on the hardness of the roll under test A softer roll will absorb more of the impact energy and the rebound distance will be less. A harder roll will reflect more of the impact energy and the rebound distance will increase. Standards TAPPI T 834 om 07 Determination of containerboard roll hardness TAPPI TIP 1004 01 TAPPI Roll Number for inventory tracking systems and bar codes Application Roll hardness is one of the most important parameter when deciding whether a paper roll is good or bad. A roll that is wound too softly can go out of round when handled. A roll that is wound too hard, on the other hand, can crack during transportation. ref name R.Duane Smith Black Clawson Converting Machinery, The Art of Winding Good Rolls . ref These variations are difficult to detect. Above all, it is typically the variation in hardness across a given roll that relates most directly to such converting issues with soft edges being perhaps the biggest contributor. ref name TAPPI Standard TAPPI Standard T 834 om 07 ref See also Paper mill Pulp paper References Reflist Category Measuring instruments Category Hardness tests ... more details
Computational Complexity may refer to Computational complexity theory Computational Complexity journal disambig Short pages monitor This long comment was added to the page to prevent it being listed on Special Shortpages. It and the accompanying monitoring template were generated via Template Longcomment. Please do not remove the monitor template without removing the comment as well. ... more details
Encyclopedia
top
