The 1890 World Allround Speed Skating Championships took place at 3 and 4 January at the ice rink Museumplein in Amsterdam, the Netherlands. It's an unofficial championship because the ISU was founded in 1892. Four distances were skated at the World Championship, the ½ mile, the 1 mile, the 2 miles and the 5 miles. One became champion; the Norwegian Adolf Norseng did not become World Champion because he only won two distances of the four. He finished second in the final. * = Fell NC = Not classified NF = Not finished NS = Not started DQ = DisqualifiedSource: SpeedSkatingStats.com Four distances have to be skated: ½ mile 1 mile 2 miles 5 miles One could only win the World Championships by winning at three of the four distances, so there would be no World Champion if no skater won three distances. The winner of the ½ mile was decided by a final of the best four skaters of the distance. If the same time was skated a skate-off is skated to decide the ranking. Silver and bronze medals were not awarded

Bound & Gagged magazine was published by the Outbound Press from 1987 to 2005. The magazine was dedicated to the interests of gay bondage and discipline practitioners and provided articles about actual encounters, fictional encounters, techniques and images of bound and gagged men, it was headquartered in New York City. According to Bob Wingate, owner of the Outbound Press and editor of Bound & Gagged, "When Bound & Gagged first appeared on the scene, there was nothing else out there. Drummer published bondage stories and photos from time to time, but there was nothing devoted to bondage in all its varied manifestations, from average guys cuffing and rope tying each other for fun, to whole ritualistic life-styles in leather and latex, making use of the most elegant and expensive restrictive devices—not to mention everything in between." Complete sets of Bound & Gagged are in the Leather Archives and Museum, as are the 25-box collection of papers of Robert W. Davolt, the editor of Bound & Gagged.

In 2017 Davolt was honored along with other notables, named on bronze bootprints, as part of San Francisco South of Market Leather History Alley. Bound & Gagged was first published in November 1987; the founder was Bob Wingate. The magazine suspended publication after issue #106 in June 2005 following the death of Robert W. Davolt, the magazine's editor. Bob Wingate's Blog Online

In numerical linear algebra, the biconjugate gradient stabilized method abbreviated as BiCGSTAB, is an iterative method developed by H. A. van der Vorst for the numerical solution of nonsymmetric linear systems. It is a variant of the biconjugate gradient method and has faster and smoother convergence than the original BiCG as well as other variants such as the conjugate gradient squared method, it is a Krylov subspace method. To solve a linear system Ax = b, BiCGSTAB starts with an initial guess x0 and proceeds as follows: r0 = b − Ax0 Choose an arbitrary vector r̂0 such that ≠ 0, e.g. r̂0 = r0. Note that notation applies for scalar product of vectors = <x,y> = x·y = x' y ρ0 = α = ω0 = 1 v0 = p0 = 0 For i = 1, 2, 3, … ρi = β = pi = ri−1 + β vi = Api α = ρi/ h = xi−1 + αpi If h is accurate enough set xi = h and quit s = ri−1 − αvi t = As ωi = / xi = h + ωis If xi is accurate enough quit ri = s − ωit Preconditioners are used to accelerate convergence of iterative methods. To solve a linear system Ax = b with a preconditioner K = K1K2 ≈ A, preconditioned BiCGSTAB starts with an initial guess x0 and proceeds as follows: r0 = b − Ax0 Choose an arbitrary vector r̂0 such that ≠ 0, e.g. r̂0 = r0 ρ0 = α = ω0 = 1 v0 = p0 = 0 For i = 1, 2, 3, … ρi = β = pi = ri−1 + β y = K−1pi vi = Ay α = ρi/ h = xi−1 + αy If h is accurate enough xi = h and quit s = ri−1 − αvi z = K−1s t = Az ωi = / xi = h + ωiz If xi is accurate enough quit ri = s − ωitThis formulation is equivalent to applying unpreconditioned BiCGSTAB to the explicitly preconditioned system Ãx̃ = b̃with à = K −11 AK −12, x̃ = K2x and b̃ = K −11 b.

In other words, both left- and right-preconditioning are possible with this formulation. In BiCG, the search directions pi and p̂i and the residuals ri and r̂i are updated using the following recurrence relations: pi = ri−1 + βipi−1, p̂i = r̂i−1 + βip̂i−1, ri = ri−1 − αiApi, r̂i = r̂i−1 − αiATp̂i; the constants αi and βi are chosen to be αi = ρi/, βi = ρi/ρi−1where ρi = so that the residuals and the search directions satisfy biorthogonality and biconjugacy i.e. for i ≠ j, = 0, = 0. It is straightforward to show that ri = Pir0, r̂i = Pir̂0, pi+1 = Tir0, p̂i+1 = Tir̂0where Pi and Ti are ith-degree polynomials in A; these polynomials satisfy the following recurrence relations: Pi = Pi−1 − αiATi−1, Ti = Pi + βi+1Ti−1. It is unnecessary to explicitly keep track of the residuals and search directions of BiCG. In other words, the BiCG iterations can be performed implicitly. In BiCGSTAB, one wishes to have recurrence relations for r̃i = QiPir0where Qi = ⋯ with suitable constants ωj instead of ri = Pi in the hope that Qi will enable faster and smoother convergence in r̃i than ri.

It follows from the recurrence relations for Pi and Ti and the definition of Qi that QiPir0 =,which entails the necessity of a recurrence relation for QiTir0. This can be derived from the BiCG relations: QiTir0 = QiPir0 + βi+1Qi−1Pi−1r0. To defining r̃i, BiCGSTAB defines p̃i+1 = QiTir0. Written in vector form, the recurrence relations for p̃i and r̃i are p̃i = r̃i−1 + βip̃i−1, r̃i =. To derive a recurrence relation for xi, define si = r̃i−1 − αiAp̃i; the recurrence relation for r̃i can be written as r̃i = r̃i−1 − αiAp̃i − ωiAsi,which corresponds to xi = xi−1 + αip̃i + ωisi. Now it remains to βi and choose a suitable ωi. In BiCG, βi = ρi/ρi−1 with ρi = =. Since BiCGSTAB does not explicitly keep track of r̂i or ri, ρi is not computable from this formula. However, it can be related to the scalar ρ̃i = = =. Due to biorthogonality, ri−1 = Pi−1r0 is orthogonal to Ui−2r̂0 where Ui−2 is any polynomial of degree i − 2 in AT. Hence, only the highest-order terms of Pi − Qi − 1 matter in the dot products and.

The leading coefficients of Pi−1 and Qi−1 are i−1α1α2⋯αi−1 and i−1ω1ω2⋯ωi−1, respectively. It follows that ρi = ⋯ρ̃i,and thus βi = ρi/ρi−1 =. A simple formula for αi can be derived. In BiCG, αi = ρi/ = /. To the case above, only the highest-order terms of Pi−1 and Ti−1 matter in the dot products thanks to biorthogonality and biconjugacy, it happens that Ti − 1 have the same leading coefficient. Thus, they can be replaced with Qi−1 in the formula, which leads to αi = / = ρ̃i/ = ρ̃i/. BiCGSTAB selects ωi to minimize r̃i = si in 2-norm as a function of ωi; this is achieved when = 0,giving the optimal value ωi = /. BiCGSTAB can be viewed as a combination of BiCG and GMRES where each BiCG step is followed by a GMRES step to repair the irregular convergence behavior of CGS, as an improvement of which BiCGSTAB was developed. However, due to the use of degree-one minimum residual polynomials, such repair may not be effective if the matrix A has large complex eigenpairs. In such cases, BiCGSTAB is to stagnate, as confirmed by numerical experiments.

One may expect that higher-degree minimum residual polynomials may better h

Hibiscus Island is a neighborhood in the city of Miami Beach on a man-made island in Biscayne Bay, United States. Hibiscus Island lies just north of Palm Island, it is an exclusive residential neighborhood with high property values. The island is accessible via the MacArthur Causeway; the dredging which created the reclaimed land on which Hibiscus Island sits was completed in 1922 by the Army Corps of Engineers, work which completed Palm and Star Island the same year. Into the 1930s, as the Great Depression diminished real estate prospects in the wake of the Florida land boom of the 1920s, The twin islands of Hibiscus and Palm Island became the winter home of such notables as Al Capone and celebrities, who were impressed by the views of the skylines of Downtown Miami and Miami Beach. In the post-World War II economic expansion and sprawl in South Florida and Hibiscus Island became the site of the Famous Latin Quarter Nightclub in the 1940s and 1950s. Owned by Lou Walters, father of journalist Barbara Walters, the Latin Quarter was a mid-century mecca for big-named entertainers who performed for winter crowds of tourists and celebrities arriving in Miami Beach each December.

Entertainers like Frank Sinatra, Dean Martin, Sammy Davis, Jr. and Tony Bennett all intermingled with waves of high-kicking chorus girls to perform three shows a night at the Latin Quarter. The island is now home to several mansions, with converted condominiums. Home to high property values in the greater Miami area, it is among the first places to evacuate in advance of a hurricane. Hibiscus Island is zoned to schools in the Miami-Dade County Public Schools. Zoned schools include: South Pointe Elementary School Nautilus Middle School Miami Beach High School Location of Hibiscus Island Florida Atlas & Gazetteer. 1989. Third ed. DeLorme Mapping. Freeport, ME

The Premier Mine is an underground diamond mine owned by Petra Diamonds in the town of Cullinan, 40 kilometres east of Pretoria, Gauteng Province, South Africa. Established in 1902, it was renamed the Cullinan Diamond Mine in November 2003 in celebration of its centenary; the mine rose to prominence in 1905, when the Cullinan Diamond – the largest rough diamond of gem quality found – was discovered there. The mine has produced over 750 stones that are greater than 100 carats and more than a quarter of all the world's diamonds that are greater than 400 carats, it is the only significant source of blue diamonds in the world. The Cullinan Diamond is the largest rough gem-quality diamond found, at 3,106.75 carats. It was found by Frederick Wells, surface manager of the Premier Diamond Mining Company in Cullinan, South Africa, on 25 January 1905; the stone was named after the owner of the diamond mine. There have been various other notable diamonds; these include: The Premier Rose – 353 carats rough The Niarchos – 426 carats rough The De Beers Centenary – 275 carats rough Golden Jubilee Diamond – 755 carats rough Taylor-Burton Diamond – 69 carats polishedIn May 2008, a sparkling shield-shaped 101.27-carat diamond mined from the Premier Mine sold for more than US$6.2 million at Christie's in Hong Kong.

Cut from a 460 carats rough, the shield-shaped gem boasts 92 brilliant facets. While internally flawless, the stone has a slight imperfection on the surface, imperceptible to the human eye, the auction house said, it is the largest colourless diamond to appear on the auction market in the last 18 years, Christie's said. Only three diamonds of more than 100 carats have appeared at auction. All were sold in Geneva. Naming rights were granted to the new owner. In September 2009, a 507-carat diamond was found, is ranked as one of the 20 biggest high quality diamonds discovered. Petra Diamonds sold it for $35.3 million on 26 February 2010, breaking a record as the highest price paid for a rough diamond. On 18 April 2013 a 25.5-carat blue rough diamond was recovered by Petra Diamonds at its Cullinan mine. According to experts it could be worth more than $10m; the find. The mine is famed for its production of blue diamonds. A similar 26.6-carat blue rough diamond recovered by Petra in May 2009 was cut into a near perfect stone and fetched just under $10m at Sotheby's.

Another deep-blue diamond from Cullinan was auctioned for $10.8m last year and set a world record for the value per carat. On 21 January 2014, Petra Diamonds announced recovery of a 29.6-carat blue diamond. According to the current CEO, Johan Dippenaar, it is one the "most significant blue diamond" to be recovered by Petra Diamonds. According to Analyst Cailey Barker at broker Numis it "could fetch between $15m and $20m at auction". Decision on what is to be done with the stone will come next week. On 13 June 2014, Petra Diamonds announced that a blue diamond of 122.52 carats was found at the Cullinan mine. The diamond, though not yet appraised, is expected to fetch more than 35 million dollars, the approximate value of the Heritage Diamond found in that mine. Petra Diamonds says that the diamond will not be put up for auction before their fiscal year ends this month. Cullinan Diamond Mine is a carrot has a surface area of 32 hectares. On 22 November 2007, De Beers, the world's largest diamond producer, sold its historic Cullinan mine to Petra Diamonds Cullinan Consortium, a consortium led by Petra Diamonds.

Diamond Mines of South Africa, Premier Diamond mine overview + images by A. R. Williams former general manager of De Beers. De Beers sells South African Cullinan Diamond Mine Official website