Mesh types

Identification of Wire Mesh Types  [c.248]

The materials of construction are usually stainless steel as well as specific other metals that will draw into wire, or crimp without cracking. The wire mesh types have been fabricated of some plastics such as Teflon , polypropylene, etc. however, the surface must be wettable by the liquid, or the efficiency will be poor, and performance data are needed to complete a good design.  [c.323]

For structured packings as loadings increase, HETP increases, and is more pronounced for wire-mesh types, and the effect is less for the corrugated sheet packings [90].  [c.375]

Separation of families by merely increasing the resolution evidently can not be used when the two chemical families have the same molecular formula. This is particularly true for naphthenes and olefins of the formula, C H2 , which also happen to have very similar fragmentation patterns. Resolution of these two molecular types is one of the problems not yet solved by mass spectrometry, despite the efforts of numerous laboratories motivated by the refiner s major interest in being able to make the distinction. Olefins are in fact abundantly present in the products from conversion processes.  [c.50]

Non-fuel petroleum products cover an extremely wide range and are distinguished as much by their nature and physical aspects as by their types of application.  [c.271]

In the future, it is expected to be possible to make more routine use of additional wave types, specifically shear or S waves (polarised to horizontal and vertical components) which have a transverse mode of propagation, and are sensitive to a different set of rock properties than P waves. The potential then exists for increasing the number of independent attributes measured in reflection surveys and increasing the resolution of the subsurface image.  [c.23]

Very many types of eddy current instruments available tend to look remarkably similar in much the same way as automobiles tend to look alike. This may be an inevitable trend since developments are converging on users needs, plus PC platforms are being used more and these too are tending to look more and more alike. In the way that the DSP has changed the inside of the instrument, the PC. is changing the outside.  [c.274]

Special probe geometries and combinations of different types of magnetic field sensors make an important contribution to the further improvement of the eddy-current testing method and results in new applications.  [c.365]

Fig.5 shows the noise influence on CCF for both types of pulses and different b values. This influence is weak, especially for q(t) type of signals. For s(t) signals growth of 2-factor critically increases the signal to noise ratio. For q(t) signals this effect is much weaker and depends on quantity of periods in pulses.  [c.830]

The pipelines wear and increase of their total length, complex natural-technical and social terms of operation of the most hazardous objects e g., nuclear and heating power plants, chemical and microbiological enterprises, air-space systems, hydro-technical installations, all types of traffic, etc. — here are the reasons of urgent necessity to use as much as possible the NDT and TD systems.  [c.910]

The range of NDT and TD means to provide the technogenic safety is so wide (more than thousand types) that as an example we refer to only some of them recently developed in Moscow Scientific-Industrial Association Spectrum .  [c.911]

MSIA Spectrum develops and manufactures more than 50 types of different instruments for NDT and TD to solve the technogenic safety issues.  [c.911]

By analysing the scans, different types of tube characteristics, wastage patterns or profiles can be documented and effectively used to make immediate decisions during shut downs and in planning maintenance programs.  [c.1033]

The succeeding material is broadly organized according to the types of experimental quantities measured because much of the literature is so grouped. In the next chapter spread monolayers are discussed, and in later chapters the topics of adsorption from solution and of gas adsorption are considered. Irrespective of the experimental compartmentation, the conclusions as to the nature of mobile adsorbed films, that is, their structure and equations of state, will tend to be of a general validity. Thus, only a limited discussion of Gibbs monolayers has been given here, and none of such related aspects as the contact potentials of solutions or of adsorption at liquid-liquid interfaces, as it is more efficient to treat these topics later.  [c.92]

In general, it is not convenient and sometimes not possible to follow reactions in films by the same types of measurements as employed in bulk systems. It is awkward to try to make chemical analyses to determine the course of a reaction, and even if one of the reactants is in solution in the substrate, the amounts involved are rather small (a micromole at best). Such analyses are greatly facilitated, of course, if radioactive labeling is used. Also, film collapsed and collected off the surface has been analyzed by infrared [299] or UV-visible [300] spectroscopy and chromatographically [301]. In situ measurements can be made if the film material has a strong absorption band that is altered by the reaction, as in the case of chlorophyll [302], or if there is strong photoexcited emission [303]. Reactions have been followed by observing changes in surface viscosity [300] and with radioactive labeling if the labeled fragment leaves the interface as a consequence of the reaction.  [c.151]

An emulsion may be defined as a mixture of particles of one liquid with some second liquid. The two common types of emulsions are oil-in-water (O/W) and water-in-oil (W/0), where the term oil is used to denote the water-insoluble fiuid. These two types are illustrated in Fig. XIV-1, where it is clear that the majority or outer phase is continuous, whereas the minority or inner phase is not. These two emulsion types are distinguished by their ability to disperse oil or water-soluble dyes, their dilution with oil or water, and their conductivity (O/W emulsions have much higher conductivity than do W/0 ones see Ref. 1 for reviews).  [c.501]

As is made evident in the next section, there is no sharp dividing line between these two types of adsorption, although the extremes are easily distinguishable. It is true that most of the experimental work has tended to cluster at these extremes, but this is more a reflection of practical interests and of human nature than of anything else. At any rate, although this chapter is ostensibly devoted to physical adsorption, much of the material can be applied to chemisorption as well. For the moment, we do assume that the adsorption process is reversible in the sense that equilibrium is reached and that on desorption the adsorbate is recovered unchanged.  [c.601]

Different types of chemisorption sites may be observed, each with a characteristic A value. Several adsorbed states appear to exist for CO chemisorbed on tungsten, as noted. These states of chemisorption probably have to do with different types of chemisorption bonding, maybe involving different types of surface sites. Much of the evidence has come initially from desorption studies, discussed immediately following.  [c.694]

Surface photochemistry can drive a surface chemical reaction in the presence of laser irradiation that would not otherwise occur. The types of excitations that initiate surface photochemistry can be roughly divided into those that occur due to direct excitations of the adsorbates and those that are mediated by the substrate. In a direct excitation, the adsorbed molecules are excited by the laser light, and will directly convert into products, much as they would in the gas phase. In substrate-mediated processes, however, the laser light acts to excite electrons from the substrate, which are often referred to as hot electrons . These hot electrons then interact with the adsorbates to initiate a chemical reaction.  [c.312]

The search for Turing patterns led to the introduction of several new types of chemical reactor for studying reaction-diffusion events in feedback systems. Coupled with huge advances in imaging and data analysis capabilities, it is now possible to make detailed quantitative measurements on complex spatiotemporal behaviour. A few of the reactor configurations of interest will be mentioned here.  [c.1111]

In the other types of mass spectrometer discussed in this chapter, ions are detected by having them hit a detector such as an electron multiplier. In early ICR instruments, the same approach was taken, but FT-ICR uses a very different teclmique. If an RF potential is applied to the excitation plates of the trapping cell (figure B 1.7.18(b)) equal to the cyclotron frequency of a particular ion m/z ratio, resonant excitation of the ion trajectories takes place (without changing the cyclotron frequency). The result is ion trajectories of higher  [c.1356]

A number of different types of experiment can be designed, in which disc and ring can either be swept to investigate the potential region at which the electron transfer reactions occur, or held at constant potential (under mass-transport control), depending on the infomiation sought.  [c.1937]

The reactivity of size-selected transition-metal cluster ions has been studied witli various types of mass spectrometric teclmiques [1 ]. Fourier-transfonn ion cyclotron resonance (FT-ICR) is a particularly powerful teclmique in which a cluster ion can be stored and cooled before experimentation. Thus, multiple reaction steps can be followed in FT-ICR, in addition to its high sensitivity and mass resolution. Many chemical reaction studies of transition-metal clusters witli simple reactants and hydrocarbons have been carried out using FT-ICR [49, 58].  [c.2394]

To resolve the problems associated with structured and unstructured grids, these fundamentally different approaches may be combined to generate mesh types which partially posses the properties of both categories. This gives rise to block-structured , overset and hybrid mesh types which under certain conditions may lead to more efficient simulations than the either class of purely structured or unstructured grids. Detailed discussions related to the properties of these classes of computational grid.s can be found in specialized textbooks (e.g, see Liseikin, 1999) and only brief definitions are given here.  [c.192]

The most common types of artificial lift are gas lift, beam pumping and downhole pumping, and the mechanics of these systems are described in Section 9.6. Gas lifting systems require a suitable gas source though at a much lower pressure than injection gas. Gas treatment considerations are similar except that heavy ends are not normally stripped out of the gas, as a lean gas would only resaturate with NGLs from the producing crude in the lifting operation. Gas compression can be avoided if a gas source of suitable pressure exists nearby, for example an adjacent gas field. Little gas is consumed in gas lifting operations but gas must be available for starting up operations after a shut down ( kicking off production). Alternatively nitrogen pumped through coiled tubing could be used for kick off, though this is expensive and may be subject to availability restrictions.  [c.259]

Some classes of adsorbents have internal surface accessible by pores small enough to act as molecular sieves, so that different apparent surface areas are obtained according to the size of the adsorbate molecule. This is a screening effect and not one of surface roughness as might be described in terms of fractal geometry (Section XVI-2B). Zeolites have been of much interest in this connection because the open way in which the (Al, Si)04 tetrahedra join gives rise to large cavities and large windows into the cavities. This is illustrated in Fig. XVII-26 [179]. As a specific example, chabasite (CaAl2Si40i2) has cages about 10 A in diameter, with six openings into each or windows of about 4-A diameter. Monatomic and diatomic gases, water, and n-alkanes can enter into such cavities, but larger molecules do not. Thus isobutane can be separated from -alkanes and, on the basis of rates, even propane from ethane [180]. The replacement of the calcium by other ions (zeolites have ion exchange properties—note Section XI-6C) considerably affects the relative adsorption behavior. Various synthetic zeolites having various window diameters in the range of 4 to 10 A are available under the name of Linde Molecular Sieves (see Ref. 179). Listings of types of zeolites and their geometric properties may be found in Refs. 181 and 182 and the related properties of expanded clay  [c.662]

Although all real surfaces have steps, they are not usually labelled as vicinal unless they are purposely misoriented in order to create a regular array of steps. Vicinal surfaces have unique properties, which make them useful for many types of experiments. For example, steps are often more chemically reactive than terraces, so that vicinal surfaces provide a means for investigating reactions at step edges. Also, it is possible to grow nanowires by deposition of a metal onto a surface of another metal in such a way that the deposited metal diflfiises to and attaches at the step edges [3].  [c.287]

Strictly speaking, die temi absorption spectroscopy refers to iiieasurements of light intensity. In practice, the absorption may be deduced from the detection of electrons or ions produced in the process, such as in absorption of light leading to pliotodetachment or photodissociation, i.e., action spectra. In the absorption spectroscopy of ions, this is a natural tack to take as the charged-particle production can be detected with greater precision than is possible for a measurement of a small change in the light intensity. The most important of such experiment types is the coaxial beams spectrometer, one of which is described in detail in the section on dissociation of ions. In these experiments, the ions are identified by mass and collimated, and interact with the laser beam over a long distance (0.25-1 in). The method was first used with ions in 1976 for HD, with the absorption events detected via eidianced production of buffer gas ions as a result of charge  [c.805]

In essence, a guided-ion beam is a double mass spectrometer. Figure A3.5.9 shows a schematic diagram of a griided-ion beam apparatus [104]. Ions are created and extracted from an ion source. Many types of source have been used and the choice depends upon the application. Combining a flow tube such as that described in this chapter has proven to be versatile and it ensures the ions are thennalized [105]. After extraction, the ions are mass selected. Many types of mass spectrometer can be used a Wien ExB filter is shown. The ions are then injected into an octopole ion trap. The octopole consists of eight parallel rods arranged on a circle. An RF  [c.811]

The impact of surface reactions on society is often overlooked. How many of us pause to appreciate integrated circuitry before checking email Yet, without growth and etching reactions, the manufacturing of integrated circuits would be quite unpractical. Or consider that in 1996, the United States alone consumed 123 billion gallons of gasoline [1]. The production of this gasoline from crude petroleum is accomplished by the petroleum industry using heterogeneous catalytic reactions. Even the control of automobile exliaust emissions, an obvious environmental concern, is achieved via catalytic reactions using tliree-way catalysts that eliminate hydrocarbons, CO and NO. The study of these types of surface reactions and others is an exciting and rapidly changing field. Nevertheless, much remains to be understood at the atomic level regarding the interaction of gases and liquids with solid surfaces.  [c.920]

Table Bl. 11.2 gives a different example of the effects of TIP. In many fluorine compounds, AE is largely detemiined by the energy difference between the bonding and antibonding orbitals in the bond to F, and hence by the strength of this bond. The shifts correlate nicely in this way. For example, C-F bonds are notoriously strong and so give low values of 5p, whereas the remarkable reactivity of F2 depends on the weakness of the F-F bond, which also gives F2 a much higher chemical shift. The weakness of the bond to F is even more apparent in the chemical shifts of the explosive compounds XeF and FOOF. In some compounds the spectra also reflect the presence of distinct types of fluorine within the molecule. For example, ClFg has a T-shaped structure with the Cl-F bond stronger for the stem of the T, giving this single F atom a lower shift. Table Bl. 11.2 gives a different example of the effects of TIP. In many fluorine compounds, AE is largely detemiined by the energy difference between the bonding and antibonding orbitals in the bond to F, and hence by the strength of this bond. The shifts correlate nicely in this way. For example, C-F bonds are notoriously strong and so give low values of 5p, whereas the remarkable reactivity of F2 depends on the weakness of the F-F bond, which also gives F2 a much higher chemical shift. The weakness of the bond to F is even more apparent in the chemical shifts of the explosive compounds XeF and FOOF. In some compounds the spectra also reflect the presence of distinct types of fluorine within the molecule. For example, ClFg has a T-shaped structure with the Cl-F bond stronger for the stem of the T, giving this single F atom a lower shift.
If multidimensional spectra of botli COSY and NOESY types can be obtained for a protein, or any comparable structured macromolecule, and if a reasonably complete assignment of the resonances is achieved, then the NOESY data can be used to detemiine its structure [3f, 32 and 33]. Typically, several hundred approximate H-H distances will be found via the NOESY spectrum of a globular protein having mass around 20 000 Da. These can then be used as constramts in a molecular modelling calculation. The resulting structures can compare in quality with those from x-ray crystallography, but do not require the preparation of crystals. Related spectra can also elucidate the internal flexibility of proteins, their folding pathways and their modes of interaction with other molecules. Such infomiation is vital to the phamiaceutical industry in the search for new chugs. It also underpins much biochemistry.  [c.1463]

Solid-state NMR has long been used by physicists to study a wide range of problems such as superconductivity, magnetism, the electronic properties of metals and semiconductors, ionic motion etc. The early experiments mostly used wide line NMR where high resolution was not required but with the development of the teclmique, particularly the improvements in resolution and sensitivity brought about by magic angle spiimmg ( Bl.12.4.3). and decoupling and cross polarization ( B solid-state NMR has become much more widely used tln-oughout the physical and, most recently, biological sciences. Although organic polymers were the first major widespread application of high-resolution solid-state NMR, it has found application to many other types of materials, from inorganics such as aluminosilicate microporous materials, minerals and glasses to biomembranes. Solid-state NMR has become increasing multinuclear and the utility of the technique is evidenced by the steady and continued increase in papers that use the teclmique to characterize materials. There is no doubt that the solid-state NMR spectrometer has become a central piece of equipment in the modem materials physics and chemistry laboratories.  [c.1465]

There is much room for further study of various importaut categories of materials oue promiueut example is oxides aud other compouuds (carbides, nitrides,. . . ) another is all types of adsorption on oxides and other compounds.  [c.1758]

Compared to other crystalline inorganic oxides, zeolites represent a special class of materials. Their crystalline, microporous nature witli well-defined pore dimensions in combination witli high tliermal stability, ion exchange and sorjDtion capacity, as well as tire ability to generate acidity has made tliem unique materials for practical applications. In recent decades, zeolites have gained tremendous importance botli from an academic and an economic point of view. On tire one hand, it is tire versatility of zeolites tliat makes tliem such outstanding materials. They are well suited for a broad range of applications such as use as drying agents, use in gas separation processes, use as detergent additives and as catalysts (see section C2.12.7). On tire otlier hand, tire variety of stmcture types, tire broad range of chemical modifications of tire zeolite matrix, and tire derived physico-chemical properties all carry a distinct fascination for tire scientist which is much reflected in tire ever growing number of  [c.2776]

In quantum wells, Heisenberg s uncertainty principle requires an increase in the carrier energy over tire equilibrium energy of the bulk semiconductor. The confined carriers are allowed only a few discrete states, witli energies inversely proportional to tire carrier s effective mass and tire square of tire well widtli. The incoryDoration of quantum wells into tire material has a number of subtle consequences. The VB in direct bulk semiconductors is degenerate at tire T point (see figure C2.16.5, resulting in two types of holes witli tire same energy, tire heavy holes and light holes. The effective mass of tire light hole is similar to that of tire electron, while tliat of tire heavy hole is typically ten times larger tlian tliat of tire electron. In quantum wells, tire degeneracy of tire two hole bands is lifted. The energy shift due to quantum well confinement is larger for tire light holes. This has important consequences for quantum well lasers and modulation-doped FETs.  [c.2894]

See pages that mention the term Mesh types : [c.112]    [c.296]    [c.339]    [c.914]    [c.915]    [c.179]    [c.311]    [c.1296]    [c.1781]    [c.1870]    [c.1940]    [c.2903]    [c.2927]   
See chapters in:

Practical aspects of finite element modelling of polymer processing  -> Mesh types