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Topic Review
BMW 3 Series (E46)
The BMW E46 is the fourth generation of the BMW 3 Series, which was produced from 1997 to 2006. The body styles of the range are: All-wheel drive, last available in the E30 3 Series, was reintroduced for the E46 on the 325xi, 330xi and 330xd models. The E46 was the first 3 Series to be available with an engine using Valvetronic (variable valve lift). Various electronic features were also introduced to the 3 Series in the E46 generation, including satellite navigation, electronic brake-force distribution, rain-sensing wipers and LED tail-lights. Following the introduction of the E90 3 Series sedans in late 2004, the E46 began to be phased out. However the E46 coupé and convertible body styles remained in production until 2006. The E46 M3 is powered by the S54 straight-six engine with either a 6-speed manual or a 6-speed SMG-II transmission. The M3 was introduced in late 2000 and was produced in coupé and convertible body styles only.
  • 40.8K
  • 03 Nov 2022
Topic Review
Shaft Mining
Shaft mining or shaft sinking is excavating a vertical or near-vertical tunnel from the top down, where there is initially no access to the bottom. Shallow shafts, typically sunk for civil engineering projects differ greatly in execution method from deep shafts, typically sunk for mining projects. When the top of the excavation is the ground surface, it is referred to as a shaft; when the top of the excavation is underground, it is called a winze or a sub-shaft. Small shafts may be excavated upwards from within an existing mine as long as there is access at the bottom, in which case they are called Raises. A shaft may be either vertical or inclined (between 45 and 90 degrees to the horizontal), although most modern mine shafts are vertical. If access exists at the bottom of the proposed shaft and ground conditions allow then raise boring may be used to excavate the shaft from the bottom up, such shafts are called borehole shafts. Shaft sinking is one of the most difficult of all development methods: restricted space, gravity, groundwater and specialized procedures make the task quite formidable. Historically mine shaft sinking has been among the most dangerous of all the mining occupations and the preserve of mining contractors called sinkers. Today shaft sinking contractors are concentrated in Canada , Germany and South Africa .
  • 14.8K
  • 17 Nov 2022
Topic Review
Mercedes-Benz CLS-Class (W219)
The C219 Mercedes-Benz CLS-Class is the first generation of the CLS-Class range of four-door coupe features a fastback body style by Mercedes-Benz, and was produced between 2004 and 2010. The CLS-Class has only four seats and is marketed by Mercedes as a four-door coupé. For this reason, in Germany and in whole Europe the model code name is C219 while in US the CLS is more commonly named as W219 model. It was the first model globally to introduce this four-door coupe style and VW followed with the Volkswagen CC model in 2008. The car is less practical than the W211 E-Class that it is based on, with less legroom, headroom, and boot space. The CLS-Class is priced above the E-Class, but below the S-Class in the Mercedes model range. It was replaced by the Mercedes-Benz CLS-Class (W218) in 2011.
  • 11.5K
  • 04 Nov 2022
Topic Review
V-twin Engine
A V-twin engine, also called a V2 engine, is a two-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration. Although widely associated with motorcycles (installed either transversely or longitudinally), V-twin engines have also been used for industrial engines and in several small cars. The V-twin design dates back to the late 1880s.
  • 10.0K
  • 21 Oct 2022
Topic Review
Overhead Camshaft
Overhead camshaft, commonly abbreviated to OHC, is a valvetrain configuration which places the camshaft of an internal combustion engine of the reciprocating type within the cylinder heads ("above" the pistons and combustion chambers) and drives the valves or lifters in a more direct manner compared with overhead valves (OHV) and pushrods.
  • 9.9K
  • 21 Nov 2022
Topic Review
Jet Engine Thrust
The familiar explanation for jet thrust is a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and exit, as explained in "Thrust calculation". As an example, an early turbojet, the Bristol Olympus Mk. 101, had a momentum thrust of 9300 lb. and a pressure thrust of 1800 lb. giving a total of 11,100 lb. Looking inside the "black box" shows that the thrust results from all the unbalanced momentum and pressure forces created within the engine itself. These forces, some forwards and some rearwards, are across all the internal parts, both stationary and rotating, such as ducts, compressors, etc., which are in the primary gas flow which flows through the engine from front to rear. The algebraic sum of all these forces is delivered to the airframe for propulsion. "Flight" gives examples of these internal forces for two early jet engines, the Rolls-Royce Avon Ra.14 and the de Havilland Goblin
  • 9.7K
  • 23 Nov 2022
Topic Review
Fuel Economy in Aircraft
The fuel economy in aircraft is the measure of the transport energy efficiency of aircraft. Efficiency is increased with better aerodynamics and by reducing weight, and with improved engine BSFC and propulsive efficiency or TSFC. Endurance and range can be maximized with the optimum airspeed, and economy is better at optimum altitudes, usually higher. An airline efficiency depends on its fleet fuel burn, seating density, air cargo and passenger load factor, while operational procedures like maintenance and routing can save fuel. Average fuel burn of new aircraft fell 45% from 1968 to 2014, a compounded annual reduction 1.3% with a variable reduction rate. In 2018, CO₂ emissions totalled 747 million tonnes for passenger transport, for 8.5 trillion revenue passenger kilometres (RPK), giving an average of 88 gram CO₂ per RPK. A 88 gCO₂/km represents 28 g of fuel per km, or a 3.5 L/100 km (67 mpg‑US) fuel consumption. New technology can reduce engine fuel consumption, like higher pressure and bypass ratios, geared turbofans, open rotors, hybrid electric or fully electric propulsion; and airframe efficiency with retrofits, better materials and systems and advanced aerodynamics.
  • 9.3K
  • 01 Nov 2022
Topic Review
Longitudinal Static Stability
In flight dynamics, longitudinal static stability is the stability of an aircraft in the longitudinal, or pitching, plane under steady flight conditions. This characteristic is important in determining whether a human pilot will be able to control the aircraft in the pitching plane without requiring excessive attention or excessive strength.
  • 9.0K
  • 20 Oct 2022
Topic Review
Cigarette Lighter Receptacle
The cigarette lighter receptacle (also called a cigar lighter receptacle or cigar lighter socket) in an automobile was initially designed to power an electrically heated cigarette lighter, but became a de facto standard DC connector to supply electrical power for portable accessories used in or near an automobile. While the cigarette lighter receptacle is a common feature of automobiles and trucks, as a DC power connector it has the disadvantages of bulkiness, relatively low current rating, and poor contact reliability. Examples of devices that can be operated from a cigarette lighter receptacle include lights, fans, beverage heating devices, and small motorized tools such as air compressors for inflating tires. Many portable electronic devices such as music players or mobile telephones use a cigarette lighter receptacle to recharge their internal batteries or to directly operate from the vehicle electrical system. Adapters for electronic devices may change voltage to be compatible with the supplied device. Devices that require alternating-current mains electricity can be operated with a plug-in inverter. Automobiles may provide several 12 V receptacles that are intended only to operate electrical accessories, and which cannot be used with a cigarette lighter. Car manufacturers may offer a cigarette lighter only as an optional extra-cost accessory. Usually, only one 12 V receptacle near the driver will be able to accommodate an actual cigarette lighter, with other receptacles designated as "12 V auxiliary power outlets" which are not physically able to power a lighter.
  • 8.7K
  • 24 Oct 2022
Topic Review
Standard Conditions for Temperature and Pressure
Standard temperature and pressure (STP) are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. In chemistry, IUPAC changed the definition of standard temperature and pressure in 1982: STP should not be confused with the standard state commonly used in thermodynamic evaluations of the Gibbs energy of a reaction. NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). This standard is also called normal temperature and pressure (abbreviated as NTP). These stated values of STP used by NIST have not been verified and require a source. However, values cited in Modern Thermodynamics with Statistical Mechanics by Carl S. Helrich and A Guide to the NIST Chemistry WebBook by Peter J. Linstrom suggest a common STP in use by NIST for thermodynamic experiments is 298.15 K (25°C, 77°F) and 1 bar (14.5038 psi, 100 kPa). The International Standard Metric Conditions for natural gas and similar fluids are 288.15 K (15.00 °C; 59.00 °F) and 101.325 kPa. In industry and commerce, standard conditions for temperature and pressure are often necessary to define the standard reference conditions to express the volumes of gases and liquids and related quantities such as the rate of volumetric flow (the volumes of gases vary significantly with temperature and pressure): standard cubic meters per second (Sm3/s), and normal cubic meters per second (Nm3/s). However, many technical publications (books, journals, advertisements for equipment and machinery) simply state "standard conditions" without specifying them; often substituting the term with older "normal conditions", or "NC". In special cases this can lead to confusion and errors. Good practice always incorporates the reference conditions of temperature and pressure. If not stated, some room environment conditions are supposed, close to 1 atm pressure, 293 K (20 °C), and 0% humidity.
  • 7.5K
  • 09 Nov 2022
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