Xem 1-20 trên 36 kết quả Oil and lubricants
  • The most important function of lubricants is the reduction of friction and wear and in some cases, the relative movement of two bearing surfaces is only possible if a lubricant is present. In times when saving energy and resources and cutting emission have become central environmental matters, lubricants are increasingly attracting public awareness. Scientific research has shown that 0.4% of gross domestic product could be saved in terms of energy in Western industrialized countries if current tribological knowledge, i.e.

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  • The phenomenon of friction has been part of daily life since the beginning of human existence. It is no surprise that some of the earliest human activities involved the reduction of friction when it was wasteful, or the use of friction when it could be beneficial. The first category includes the use of vegetable oils and animal fats as lubricants, as well as the use of rolling motion to take advantage of the resulting low resistance to movement.

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  • Volume II of the Handbook of Lubrication (Tribology) provides coverage of basic theory involved in friction, wear, and lubrication; characteristics and application practices for lubricants; and design principles for lubricated machine elements such as bearings, gears, couplings, and seals.

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  • The Andehydration is an important process in offshore gas processing. The gas is dehydrated offshore to avoid dangers associated with pipeline transport and prossing of wet gas. The problems include corrosion, water condensation and plugs created by ice or gas hydrates.

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  • Microscopic and imaging techniques: – Optical microscopy – Confocal microscopy – Electron microscopy (SEM and TEM, related methods) – Scanning probe microscopy (STM and AFM, related methods) Surface spectrometric techniques: – X-ray fluorescence (from electron microscopy) – Auger electron spectrometry – X-ray photoelectron spectrometry (XPS/UPS/ESCA)

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  •  Infrared (IR) Spectroscopy: – First real IR spectra measured by Abney and Festing in 1880’s – Technique made into a routine analytical method between 1903- 1940 (especially by Coblentz at the US NBS) – IR spectroscopy through most of the 20th century is done with dispersive (grating) instruments, i.e. monochromators – Fourier Transform (FT) IR instruments become common in the 1980’s, led to a great increase in sensitivity and resolution  Raman Spectroscopy: – In 1928, C. V.

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  • New material in this edition includes the latest developments in refrigerants and lubricants, together with updated information on compressors, heat exchangers, liquid chillers, electronic expansion valves, controls and cold storage. Topics also covered include efficiency, environmental impact, split systems, retail refrigeration (supermarket systems and cold rooms), industrial systems, fans, air infiltration and noise. This book is divided into 2 parts, part 1 includes the following contents: Fundamentals, the refrigeration cycle, refrigerants, compressors,...

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  • Aldehydes and Ketones – Form acetals and ketals respectively with normal methanol-containing reagents – Water formed in this reaction will then be titrated to give erroneously high water results – With aldehydes a second side reaction can take place, consuming water, which can lead to sample water content being underestimated – Replacing methanol with another solvent can solve the difficulties (commercial reagents are widely available)

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  • Petroleum products are everywhere around us. They appear in visible forms, such as gasoline, diesel, kerosene, and aircraft fuels, and in less visible forms over the entire spectrum of industry, such as automobile lubricants, greases, carbon black for truck tires, bitumen for road building, the waterproofing in house roofs, feedstock for petrochemicals, synthetic fibers, and plastics. Petroleum feedstock is used in the manufacture of white mineral oils in eye ointment, hair oils, cosmetics, petroleum solvents, and pest control sprays....

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  •  IUPAC Definition: chromatography is a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary while the other moves in a definite direction  Stationary phase (SP): common name for the column packing material in any type of chromatography  Mobile phase (MP): liquid media that continuously flows through the column and carries the analytes  Analyte: the chemical species being investigated (detected and quantitatively measured) by an analytical method...

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  • ● Adsorption chromatography • The stationary phase is an adsorbent (like silica gel or any other silica-based packing) • The separation is based on repeated adsorption-desorption steps. ● Normal-phase chromatography • The stationary bed is strongly polar in nature (e.g., silica gel), and the mobile phase is nonpolar (such as n-hexane or tetrahydrofuran). • Polar samples are retained on the polar surface of the column packing longer than less polar materials.

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  • Surface contamination: – The obvious contamination/alteration of surfaces that can be the result of less-than careful sample preparation – Solid surfaces can adsorb gases: At 10-6 torr, a complete monolayer of a gas (e.g. CO) takes just 3 seconds to form. At 10-8 torr, monolayer formation takes 1 hour. – Most studies are conducted under vaccuum – although there are newer methods that don’t require this.

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  • Mass Spectrometry (a.k.a. MS or mass spec) – a method of separating and analyzing ions by their mass-to-charge ratio MS does not involve a specific region of the electromagnetic spectrum (because it is not directly interested in the energies of emitted photons, electronic or vibrational transitions, nuclear spin transitions, etc…)

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  • The lubrication of rolling bearings – similar to that of sliding bearings – mainly serves one purpose: to avoid or at least reduce metal-to-metal contact between the rolling and sliding contact surfaces, i.e. to reduce friction and wear in the bearing. Oil, adhering to the surfaces of the parts in rolling contact, is fed between the contact areas. The oil film separates the contact surfaces preventing metal-to-metal contact (»physical lubrication«).

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  • Tower reported the results of a series of experiments intended to determine the best methods to lubricate a railroad journal bearing. Working with a partial journal bearing in an oil bath, he noticed and later measured the pressure generated in the oil film. Tower pointed out that without sufficient lubrication, the bearing operates in the boundary lubrication regime, whereas with adequate lubrication the two surfaces are completely separated by an oil film. Petrov [5] also conducted experiments to measure the frictional losses in bearings.

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  • LIF (laser-induced fluorescence) is a very popular CE detector – These have ~0.01 attomole sensitivity for fluorescent molecules (e.g. derivatized proteins). Direct absorbance (UV-Vis) can be used for organics. For inorganics, indirect absorbance methods are used instead, where a absorptive buffer (e.g. chromate) is displaced by analyte ions – Detection limits are in the 50-500 ppb range. Alternative methods involving potentiometric and conductometric detection are also used – Potentiometric detection: a broad-spectrum ISE – Conductometric detection: like IC...

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  •  Matched against a wide range of spectroscopic and chromatographic techniques, the techniques of electroanalytical chemistry find an important role for several reasons: – Electroanalytical methods are often specific for a particular oxidation state of an element – Electrochemical instrumentation is relatively inexpensive and can be miniaturized – Electroanalytical methods provide information about activities (rather than concentration)

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  • Analytical chemists work to improve the reliability of existing techniques to meet the demands of for better chemical measurements which arise constantly in our society They adapt proven methodologies to new kinds of materials or to answer new questions about their composition. They carry out research to discover completely new principles of measurements and are at the forefront of the utilization of major discoveries such as lasers and microchip devices for practical purposes.

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  • The velocity at which radiation travels (or propagates) through a medium is dependent on the medium itself When radiation travels through a medium and does not undergo a frequency change, it cannot be undergoing a permanent energy transfer However, radiation can still interact with the medium – Radiation, an EM field, polarizes the electron clouds of atoms in the medium – Polarization is a temporary deformation of the electron clouds

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  • If you read March’s paper on ion traps: – What is resonant excitation? Summarize how resonant excitation is used in typical ion trap MS experiments. If you read the Russell and Edmondson paper on MALDITOF and accurate mass: – Summarize the advantages and disadvantages of MALDI-TOF (with DE and reflection) versus FTICR (including ESI-FTICR), especially in biochemical applications.

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