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Beijing National Aquatics Center

The Beijing National Aquatics Center officially known as the National Aquatics Center, colloquially known as the Water Cube, is an aquatics center at the Olympic Green in Beijing, China. The facility was constructed to host the aquatics competitions at the 2008 Summer Olympics and Paralympics. During the Olympics — where it hosted diving and synchronised swimming events — 25 world records were broken in swimming. In July 2010, a renovation of the facility was completed, which included the addition of a 12,000 m2 public water park. With Beijing awarded the 2022 Winter Olympics, part of the Water Cube was renovated in 2019 to allow the hosting of curling events. In July 2003 the Water Cube design was chosen from 10 proposals in an international architectural competition for the aquatic center project; the Water Cube was specially designed and built by a consortium made up of PTW Architects, Arup international engineering group, CSCEC, CCDI of Shanghai. The Water Cube's design was initiated by a team effort: the Chinese partners felt a square was more symbolic to Chinese culture and its relationship to the Bird's Nest stadium while the Sydney-based partners came up with the idea of covering the'cube' with bubbles, symbolising water.

Contextually, the Cube symbolises Earth whilst the circle represents heaven, a common motif in ancient Chinese art. Comprising a steel space frame, it is the largest ETFE-clad structure in the world with over 100,000 m² of ETFE pillows that are only 0.2 mm in total thickness. The ETFE cladding and installed by the firm Vector Foiltec, allows more light and heat penetration than traditional glass, resulting in a 30% decrease in energy costs; this choice was made in view of Beijing's goal of presenting a "green" Olympic Games, with zero net growth in total carbon emissions. The venue was designed to "capture and recycle 80% of the water falling on the roof or lost from the pools."The outer wall is based on the Weaire–Phelan structure, a structure devised from the natural pattern of bubbles in soap lather. In the true Weaire–Phelan structure the edge of each cell is curved in order to maintain 109.5 degree angles at each vertex, but of course as a structural support system each beam was required to be straight so as to better resist axial compression.

The complex Weaire–Phelan pattern was developed by slicing through bubbles in soap foam, resulting in more irregular, organic patterns than foam bubble structures proposed earlier by the scientist Kelvin. Using the Weaire–Phelan geometry, the Water Cube's exterior cladding is made of 4,000 ETFE bubbles, some as large as 9.14 metres across, with seven different sizes for the roof and 15 for the walls. The structure had a capacity of 17,000 during the games, it has a total land surface of 65,000 square meters and covers a total of 32,000 square metres. Although called the Water Cube, the aquatic center is a rectangular box 178 metres square and 31 metres high; the building's popularity has spawned many copycat structures throughout China. For example, there is one-to-one copy of the facade near the ferry terminal in Macau – the Casino Oceanus by Paul Steelman; the Aquatics Center hosted the swimming and synchronized swimming events during the Olympics. Water polo was planned to be hosted in the venue but was moved to the Ying Tung Natatorium.

Many people believed the Water Cube to be the fastest Olympic pool in the world. Over the course of the Games, 25 world records were broken by athletes at the Water Cube, although all but two of them were achieved by swimmers wearing the controversial LZR Racer bodyskin. After the Olympics, the Water Cube was opened to the public on select days of the week beginning in June 2009, was used as the site for a production of Swan Lake among other shows. On 19 October 2009, the Water Cube was closed to the public to begin a renovation of a portion of the complex into a water park, led by Canadian design firm Forrec, promising "seven-story water slides and a wave machine, as well as attractions for the more land inclined such as shopping centers and performance stages."The facility reopened on 28 July 2010, with the water park opening on 8 August 2010. The renovation divided the facility into three pool areas, as well as the 12,000 m2 water park area; the In July 2013, the Water Cube introduced a new LED light show on its exterior, "Nature and Man in Rhapsody of Light", by artist Jennifer Wen Ma and lighting designer Zheng Jiawei.

Its colors are determined by trending use of emoji on Sina Weibo, in turn used to calculate the "mood" of the Chinese public In 2018, it was reported that the venue had achieved revenues of 124 million yuan, has been breaking for years. The Water Cube will host curling events during the 2022 Winter Olympics and Paralympics, a configuration nicknamed the "Ice Cube". After Beijing was awarded the Games, work began on renovations to the facility to allow it to be converted to a curling rink, including the addition of ice-making equipment and other necessary climate control

Gully

A gully is a landform created by running water, eroding into soil on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width; when the gully formation is in process, the water flow rate can be substantial, causing a significant deep cutting action into soil. The earliest known usage of the term is from 1657, it originates from a diminutive form of goule which means throat. It is possible that the term was derived from a type of knife at the time, a gully-knife, because hills that have gullies look as if they are cut open with a sharp knife. Gully erosion is the process. Hillsides are more prone to gully erosion when they are cleared of vegetation, through deforestation, over-grazing or other means; the eroded soil is carried by the flowing water after being dislodged from the ground when rainfall falls during short, intense storms such as during thunderstorms. A gully may grow in length by means of headward erosion at a knick point; this erosion can result from interflow as well as surface runoff.

Gullies reduce the productivity of farmland where they incise into the land, produce sediment that may clog downstream waterbodies. Because of this, much effort is invested into the study of gullies within the scope of geomorphology, in the prevention of gully erosion, in restoration of gullied landscapes; the total soil loss from gully formation and subsequent downstream river sedimentation can be sizeable. Gullies can be enlarged by a number of human activities. Artificial gullies are formed during hydraulic mining when jets or streams of water are projected onto soft alluvial deposits to extract gold or tin ore; the remains of such mining methods are visible landform features in old goldfields such as in California and northern Spain. The badlands at Las Medulas for example, were created during the Roman period by hushing or hydraulic mining of the gold-rich alluvium with water supplied by numerous aqueducts tapping nearby rivers; each aqueduct produced large gullies below by erosion of the soft deposits.

The effluvium was washed with smaller streams of water to extract the nuggets and gold dust. Gullies are widespread at mid- to high latitudes on the surface of Mars, are some of the youngest features observed on that planet forming within the last few 100,000 years. There, they are one of the best lines of evidence for the presence of liquid water on Mars in the recent geological past resulting from the slight melting of snowpacks on the surface or ice in the shallow subsurface on the warmest days of the Martian year. Flow as springs from deeper seated liquid water aquifers in the deeper subsurface is a possible explanation for the formation of some Martian gullies. Oxford English Dictionary

Grace Divine School collapse

The Grace Divine School collapse occurred on November 12, 2008, at the Grace Divine Primary and Secondary School in the Canapé Vert section of Port-au-Prince, Haiti. The collapse, along with the 2008 Pétion-Ville school collapse, was the second such incident in Haiti in less than a week; the school building was a two-story concrete structure built on the side of a hill. According to one AFP witness, "chunks of the school's walls were scattered on the ground, its concrete roof was sagging, there were clear cracks in the remaining walls". No cause was apparent, but poor-quality construction and heavy rains in the preceding days were believed to have been contributing factors; the Red Cross reported that some students were jumping and dancing in a musical just prior to collapse, which may have strained the weakened structure. Around 100 students, ages 5 to 12, attended Grace Divine School; the collapse occurred during a break in classes, when most of the school's students were outside in the yard.

At least nine individuals were injured, including two students. A preliminary search reported that no one was trapped in the debris and that there were no fatalities. Compared to the Pétion-Ville disaster, the number and severity of casualties in Port-au-Price were low because of little damage to the buildings and most students were outside of the building during collapse. After hearing of the collapse parents anxiously gathered at the school, fearing a similar deadly outcome of the collapse of the La Promesse school in Pétion-Ville. Foreign and domestic rescue teams were quick to arrive on scene due to their involvement in the Pétion-Ville collapse. At one school a mile away from Grace Divine, students believed their own school building was shaking. Initial information about the disaster was reported to the international media by Dr. Jean Pierre Guiteau, the executive officer of the Haitian Red Cross