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Topic Review
Ultra-Precision Machining Technologies
In order to reduce the surface/subsurface damage of soft-brittle optical materials and improve their surface quality, it is necessary to carry out ultra-precision machining of soft-brittle optical materials. Common ultra-precision machining techniques for soft-brittle optical materials include abrasive-free deliquescent polishing, single-point diamond turning (SPDT), chemical mechanical polishing (CMP), ultra-precision grinding, micro-milling, ion beam figuring (IBF) and magnetorheological finishing (MRF).
  • 2.8K
  • 29 Oct 2020
Topic Review
Ultra-Low-Frequency Oscillation
One of the prominent problems faced with hydro-dominant power system is ultra-low-frequency oscillation (ULFO) with a frequency deviation of 0.1 Hz lower, which is caused by the negative damping of hydro generators. ULFO might lead to an oscillation of all generators with the same oscillation frequency, restricting consumption of hydropower renewable energy.
  • 1.7K
  • 27 Oct 2020
Topic Review
Ultra-High-Purity Aluminum
Properties of high-purity aluminum are the low magnetic permeability, the absence of low-temperature brittleness, as well as the increased strength and plasticity at low temperatures. These explain the classical application of high- to ultra-high-purity aluminum for the stabilization of superconductors running at cryogenic temperatures as low as −269 °C.
  • 2.7K
  • 01 Nov 2021
Topic Review
Ultra-High-Performance Fibre-Reinforced Concrete
Ultra-high-performance fibre-reinforced concrete (UHPFRC) is a cementitious composite which contains fibres. UHPFRC has emerged as an effective structural retrofitting material due to its superior mechanical properties. In addition, UHPFRC has outstanding durability, ductility and workability; a low permeability; and a high abrasion and fire resistance. 
  • 321
  • 18 Apr 2023
Topic Review
Ultra-High-Performance Concrete (UHPC) Piles and Splicing Options
Conventional driven piles are made from steel, concrete, timber, or composite materials. These piling options have limitations with respect to corrosion, durability, driveablity, and performance. Ultra-High-Performance Concrete (UHPC) pile is a new alternative that has already been adopted by various state Departments of Transportation in the United States for addressing the limitations that exist with conventional piles. UHPC piles are made of a cementitious composite material mixture that possesses exceptional properties such as higher strength, low capillary porosity, and high resistance to corrosion, making them a suitable option for use as a deep foundation. For several reasons, it is necessary to cast piles with a shorter length and splice them at the site to reach the desired lengths.
  • 187
  • 07 Mar 2024
Topic Review
Ultra-High Performance Concrete Mixtures and Supplementary Cementitious Materials
Ultra-high performance concrete (UHPC) is a novel cement-based material with exceptional mechanical and durability properties. Silica fume, the primary supplementary cementitious material (SCM) in UHPC, is expensive in North America, so it is often substituted with inexpensive class F fly ash. However, future availability of fly ash is uncertain as the energy industry moves toward renewable energy, which creates an urgent need to find cost-effective and environmentally friendly alternatives to fly ash. Replacing cement, fly ash, and silica fume in UHPC mixtures with ground granulated blast-furnace slag (GGBFS), metakaolin, and a natural pozzolan (pumicite) are investigated. To identify acceptable UHPC mixtures (28-day compressive strength greater than 120 MPa), workability, compression, and flexural tests were conducted on all mixtures. Then, durability properties including shrinkage, frost resistance, and chloride ion permeability (rapid chloride permeability and surface resistivity tests) were evaluated for the acceptable UHPC mixtures. Results showed that 75, 100, and 40% of fly ash in the control mixture could be replaced with pumicite, metakaolin, and GGBFS, respectively, while still producing acceptable strengths. Flexural strengths were greater than 14.20 MPa for all mixtures. For durability, UHPC mixtures had shrinkage strains no greater than 406 μstrain, durability factors of at least 105, and “very low” susceptibility to chloride ion penetration, indicating that these SCMs are suitable candidates to completely replace fly ash and partially replace silica fume in non-proprietary UHPC.
  • 361
  • 16 Nov 2023
Topic Review
Ultra-Heat Treatment on Milk Proteins
Milk contains approximately 3.5% by weight protein, which is a highly complex system. This milk protein is usually divided into two main fractions based on their solubility nature. Casein proteins are about 75% to 80% of the total protein in the milk and precipitate at pH 4.6 at 20 °C, while 20% of the protein remains in the serum.
  • 2.6K
  • 07 Oct 2021
Topic Review
Ultra-Endurance Participation and Acute Kidney Injury
Increasingly popular, ultra-endurance participation exposes athletes to extremely high levels of functional and structural damage. Ultra-endurance athletes commonly develop acute kidney injury (AKI) and other pathologies harmful to kidney health. There is strong evidence that non-steroidal anti-inflammatory drugs, common amongst ultra-athletes, is linked to increased risk and severity of AKI and potentially ischaemic renal injury, i.e., acute tubular necrosis. Ultra-endurance participation also increases the risk of exertional rhabdomyolysis, exercise-associated hyponatremia, and gastrointestinal symptoms, interlinked pathologies all with potential to increase the risk of AKI. Hydration and fuelling both also play a role with the development of multiple pathologies and ultimately AKI, highlighting the need for individualised nutritional and hydration plans to promote athlete health. Faster athletes, supplementing nitrates, and being female also increase the risk of developing AKI in this setting.
  • 725
  • 12 Jan 2023
Topic Review
Ultra-Dense Networks Taxonomy
Ultra-Dense Network (UDN) is a network with a spatial density of access points (APs) (or base stations) identical to or larger than the number of active end devices—EDs (user equipments (UEs) or physical devices (PDs)). UDNs can be seen as a network paradigm which can be implemented in the context of various kinds of wireless networks, such as sensor/IoT (Internet of Things) networks, mobile networks, aerial networks, and even satellite networks. 
  • 765
  • 31 Jan 2023
Topic Review
Ultimate Issue (Law)
An ultimate issue in criminal law is a legal issue at stake in the prosecution of a crime for which an expert witness is providing testimony.
  • 899
  • 11 Oct 2022
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