T Third Street
The T Third Street is a Muni Metro line in San Francisco, California. It is the first new light rail line in San Francisco in more than half a century, the first accessible line in the system, it is the first true light rail line in the streetcar Muni Metro system, as it operates in a street median, rather than in mixed traffic. Testing on the line took place in summer 2006, with limited service starting on January 13, 2007, full service beginning on April 7, 2007, it runs along the newly constructed light-rail tracks on Third Street and Bayshore Boulevard in the Visitacion Valley, Bayview/Hunters Point and Mission Bay neighborhoods, connecting to the existing Muni Metro system along the southern Embarcadero and below Market Street, replaced the 15 Third bus line. In the future, the line may be extended to Caltrain's Bayshore Station and, in the other direction, to San Francisco's Washington Square in North Beach via Chinatown Central Subway alignment. Following service changes on June 30, 2007, the T Third Street and the K Ingleside lines were spliced together in the Market Street Subway tunnel, resulting in a route from Balboa Park, through downtown, to Bayshore and Sunnydale.
At West Portal Station, inbound K trains heading through downtown to Third Street change their signs to the T line. Each train displays its ultimate destination; this system will continue in place. Leaving the Market Street Subway at Ferry Portal heading south, the T Third follows The Embarcadero south of Market Street veers onto King Street in front of Oracle Park until it reaches the Caltrain station terminal; this portion of the Muni Metro rail line between the Embarcadero portal and the Caltrain terminal was built in 1998 and is utilized by an extension of the N Judah, which shares track with the T to the Caltrain terminal at 4th and King. From there the T turns south on Fourth Street, crossing the bridge over Mission Creek before joining Third Street for the majority of the route's length, it passes through Mission Bay where the UCSF Mission Bay branch is located continues on south through the Bayview and Hunters Point neighborhoods. Once both economically impoverished parts of the City, they have experienced rehabilitation and rebuilding helped by the new T line.
At the intersection of Third and Jamestown Avenue, the T continues to run in both directions as it crosses U. S. Highway 101, although only Third Street is open to auto traffic northbound. From there the T follows Bayshore Boulevard for two more stations until it reaches its terminus at Sunnydale Station. A section of track follows one more block. All stations along this line feature high platforms, eliminating the need for the raising and lowering of entrance and exit steps characteristic of other Muni Metro lines. Stations south of Fourth and King feature short platforms; the T Third uses the Muni Metro terminology in which an inbound train goes from West Portal to Embarcadero. This means that an outbound T Third train runs from Sunnydale and out to the western neighborhoods via downtown; this is the reverse of other lines, as those lines have their outer termini on the southwest and west sides of the city, those trains enter the subway from the west going inbound toward downtown. The underground section of the line was closed west of Castro station from June 25 to August 24, 2018 due to the Twin Peaks Tunnel shutdown.
On August 25, 2018, at the conclusion of the shutdown, Muni began running permanently two-car trains on the K/T line. The line was shut down from January 22, 2019 until April 1, 2019 for construction of a new platform at UCSF/Mission Bay station. T-Third has been built in phases; the first phase extended rail service south to Sunnydale Station. The second phase under construction, is known as the Central Subway project, will reroute T-Third north of the 4th and King Station; the future alignment once the second phase is complete will neither share right-of-way with, nor share identities with the K Ingleside, avoiding both King Street and the congested Market Street subway. The southern segment from Sunnydale to 4th and King Street will remain as-is, operating on street-level tracks in the median of Third Street and Bayshore Boulevard. After 4th and King, the line will cross King Street instead of turning onto it, proceed to a new 4th and Brannan Station, the line will burrow to subsurface level at Bryant Street Portal, near where 4th passes under Interstate 80.
Underground, the line will continue under Fourth Street, to Yerba Buena/Moscone Station, after crossing Market Street, will turn to continue under Stockton Street, continuing to Union Square/Market Station providing a transfer to Market Street Subway MUNI and BART lines before running underneath Stockton Street and terminating at Chinatown Station. To complement the Central Subway, Muni is constructing the Mission Bay Loop, an additional loop along the T Third line that would enable more frequent short-line service to the section of the line from Mission Bay through the Central Subway. MBL would connect the existing T Third tracks on 3rd Street to additional tracks along 18th Street, Illinois Street, 19th Street to connect back to 3rd Street. A proposed third phase would build an extension beyond Chinatown, in
A water block is the watercooling equivalent of a heatsink. It can be used on many different computer components, including the central processing unit, GPU, PPU, Northbridge chipset on the motherboard, it consists of at least two main parts. The second part, the "top" ensures the water is contained safely inside the water block and has connections that allow hosing to connect it with the water cooling loop; the top can be made of the same metal as the base, transparent Perspex, Nylon, or HDPE. Most newer high-end water blocks contain mid-plates which serve to add jet tubes and other flow altering devices; the base and mid-plate are sealed together to form a "block" with some sort of path for water to flow through. The ends of the path have inlet/outlet connectors for the tubing that connects it to the rest of the watercooling system. Early designs included spiral, zig-zag pattern or heatsink like fins to allow the largest possible surface area for heat to transfer from the device being cooled to the water.
These designs were used because the conjecture was that maximum flow was required for high performance. Trial and error and the evolution of water block design has shown that trading flow for turbulence can improve performance; the Storm series of water blocks is an example of this. Its jet tube mid plate and cupped base design makes it more restrictive to the flow of water than early maze designs but the increased turbulence results in a large increase in performance. Newer designs include "pin" style blocks, "jet cup" blocks, further refined maze designs, micro-fin designs, variations on these designs. Restrictive designs have only been possible because of increases in maximum head pressure of commercially viable water pumps. A water block is better at dissipating heat than an air-cooled heatsink due to water's higher specific heat capacity and thermal conductivity; the water is pumped through to a radiator which allows a fan pushing air through it to take the heat created from the device and expel it into the air.
A radiator is more efficient than a standard CPU or GPU heatsink/air cooler at removing heat because it has a much larger surface area. Installation of a water block is similar to that of a heatsink, with a thermal pad or thermal grease placed between it and the device being cooled to aid in heat conduction
Water cooling is a method of heat removal from components and industrial equipment. Water may be a more efficient heat transfer fluid. In most occupied climates water offers the thermal conductivity advantages of a liquid with unusually high specific heat capacity and the option of evaporative cooling. Low cost allows rejection as waste after a single use, but recycling coolant loops may be pressurized to eliminate evaporative loss and offer greater portability and improved cleanliness. Unpressurized recycling coolant loops using evaporative cooling require a blowdown waste stream to remove impurities concentrated by evaporation. Disadvantages of water cooling systems include accelerated corrosion and maintenance requirements to prevent heat transfer reductions from biofouling or scale formation. Chemical additives to reduce these disadvantages may introduce toxicity to wastewater. Water cooling is used for cooling automobile internal combustion engines and large industrial facilities such as nuclear and steam electric power plants, hydroelectric generators, petroleum refineries and chemical plants.
Other uses include cooling of lubricant oil in pumps. The main mechanism for water cooling is convective heat transfer. Water is inexpensive, non-toxic, available over most of the earth's surface. Liquid cooling offers higher thermal conductivity than air cooling. Water has unusually high specific heat capacity among available liquids at room temperature and atmospheric pressure allowing efficient heat transfer over distance with low rates of mass transfer. Cooling water may be recycled through a recirculating system or used in a single pass once-through cooling system. Water's high enthalpy of vaporization allows the option of efficient evaporative cooling to remove waste heat in cooling towers or cooling ponds. Recirculating systems may be open if they rely upon evaporative cooling or closed if heat removal is accomplished in heat exchangers with negligible evaporative loss. A heat exchanger or condenser may separate non-contact cooling water from a fluid being cooled, or contact cooling water may directly impinge on items like saw blades where phase difference allows easy separation.
Environmental regulations emphasize the reduced concentrations of waste products in non-contact cooling water. Water is an ideal cooling medium for vessels as they are surrounded by water that remains at a low temperature throughout the year. Systems operating with sea water need to be manufactured from cupronickel, titanium or corrosion-resistant materials. Water containing sediment may require velocity restrictions through piping to avoid erosion at high velocity or blockage by settling at low velocity. Water is a favorable medium for biological growth. Dissolved minerals in natural water supplies are concentrated by evaporation to leave deposits called scale. Cooling water requires addition of chemicals to minimize corrosion and insulating deposits of scale and biofouling. Water is a favorable environment for many life forms. Flow characteristics of recirculating cooling water systems encourage colonization by sessile organisms to use the circulating supply of food and nutrients. Temperatures may become high enough to support thermophilic populations.
Biofouling of heat exchange surfaces can reduce heat transfer rates of the cooling system. Biofouling may create differential oxygen concentrations increasing corrosion rates. OTC and open recirculating systems are most susceptible to biofouling. Biofouling may be inhibited by temporary habitat modifications. Temperature differences may discourage establishment of thermophilic populations in intermittently operated facilities. Biocides have been used to control biofouling where sustained facility operation is required. Water contains varying amounts of impurities from contact with the atmosphere and containers. Manufactured metals tend to revert to ores via electrochemical reactions of corrosion. Water can accelerate corrosion as both an electrical conductor and solvent for metal ions and oxygen. Corrosion reactions proceed more as temperature increases. Preservation of machinery in the presence of hot water has been improved by addition of corrosion inhibitors including zinc and phosphates; the first two have toxicity concerns.
Residual concentrations of biocides and corrosion inhibitors are of potential concern for OTC and blowdown from open recirculating systems. With the exception of machines with short design life, closed recirculating systems require periodic cooling water treatment or replacement raising similar concern about ultimate disposal of cooling water containing chemicals used with environmental safety assumptions of a closed system. Total dissolved solids or TDS is measured as the mass of residue remaining when a measured volume of filtered water is evaporated. Salinity measures water conductivity changes caused by dissolved materials. Probability of scale formation increases with increasing total dissolved solids. Solids associated with scale formation are calcium and magnesium carbonate and sulfate. Corrosion rates increase with salinity in response to increasing electrical conductivity
A pressure vessel is a container designed to hold gases or liquids at a pressure different from the ambient pressure. Pressure vessels can be dangerous, fatal accidents have occurred in the history of their development and operation. Pressure vessel design and operation are regulated by engineering authorities backed by legislation. For these reasons, the definition of a pressure vessel varies from country to country. Design involves parameters such as maximum safe operating pressure and temperature, safety factor, corrosion allowance and minimum design temperature. Construction is tested using nondestructive testing, such as ultrasonic testing and pressure tests. Hydrostatic tests use water. Hydrostatic testing is preferred, because it is a safer method, as much less energy is released if a fracture occurs during the test. In most countries, vessels over a certain size and pressure must be built to a formal code. In the United States that code is Pressure Vessel Code; these vessels require an authorized inspector to sign off on every new vessel constructed and each vessel has a nameplate with pertinent information about the vessel, such as maximum allowable working pressure, maximum temperature, minimum design metal temperature, what company manufactured it, the date, its registration number, ASME's official stamp for pressure vessels.
The nameplate makes the vessel traceable and an ASME Code vessel. The earliest documented design of pressure vessels was described in 1495 in the book by Leonardo da Vinci, the Codex Madrid I, in which containers of pressurized air were theorized to lift heavy weights underwater. However, vessels resembling those used today did not come about until the 1800s, when steam was generated in boilers helping to spur the industrial revolution. However, with poor material quality and manufacturing techniques along with improper knowledge of design and maintenance there was a large number of damaging and fatal explosions associated with these boilers and pressure vessels, with a death occurring on a nearly daily basis in the United States. Local providences and states in the US began enacting rules for constructing these vessels after some devastating vessel failures occurred killing dozens of people at a time, which made it difficult for manufacturers to keep up with the varied rules from one location to another and the first pressure vessel code was developed starting in 1911 and released in 1914, starting the ASME Boiler and Pressure Vessel Code.
In an early effort to design a tank capable of withstanding pressures up to 10,000 psi, a 6-inch diameter tank was developed in 1919, spirally-wound with two layers of high tensile strength steel wire to prevent sidewall rupture, the end caps longitudinally reinforced with lengthwise high-tensile rods. The need for high pressure and temperature vessels for petroleum refineries and chemical plants gave rise to vessels joined with welding instead of rivets and in the 1920s and 1930s the BPVC included welding as an acceptable means of construction, welding is the main means of joining metal vessels today. There have been many advancements in the field of pressure vessel engineering such as advanced non-destructive examination, phased array ultrasonic testing and radiography, new material grades with increased corrosion resistance and stronger materials, new ways to join materials such as explosion welding, friction stir welding, advanced theories and means of more assessing the stresses encountered in vessels such as with the use of Finite Element Analysis, allowing the vessels to be built safer and more efficiently.
Today vessels in the USA require BPVC stamping but the BPVC is not just a domestic code, many other countries have adopted the BPVC as their official code. There are, other official codes in some countries, Australia, Canada and Europe have their own codes. Regardless of the country nearly all recognize the inherent potential hazards of pressure vessels and the need for standards and codes regulating their design and construction. Pressure vessels can theoretically be any shape, but shapes made of sections of spheres and cones are employed. A common design is a cylinder with end caps called heads. Head shapes are either hemispherical or dished. More complicated shapes have been much harder to analyze for safe operation and are far more difficult to construct. Theoretically, a spherical pressure vessel has twice the strength of a cylindrical pressure vessel with the same wall thickness, is the ideal shape to hold internal pressure. However, a spherical shape is difficult to manufacture, therefore more expensive, so most pressure vessels are cylindrical with 2:1 semi-elliptical heads or end caps on each end.
Smaller pressure vessels are assembled from two covers. For cylindrical vessels with a diameter up to 600 mm, it is possible to use seamless pipe for the shell, thus avoiding many inspection and testing issues the nondestructive examination of radiography for the long seam if required. A disadvantage of th