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Closed periodic system

Computer simulations represent one of the most common approaches to determining the local fluctuations. However, there are some technical difficulties, which can arise during the analysis of a typical simulation (see Chapter 6 for a full discussion). Most evaluations of the KBls have used the integration approach, in contrast to the actual particle number fluctuations. Furthermore, as the vast majority of simulations are performed for closed periodic systems, one is naturally limited to performing the integration out to some cutoff distance from the particle of interest. This seems reasonable given the similarities between the RDFs in open and closed systems (Weerasinghe and Pettitt 1994). Hence, one can define distance-dependent KBIs (and even distance-dependent thermodynamic functions) such that... [Pg.33]

Because the system likely is nonisothermal, the analysis of a closed-desiccant system requites knowledge of the temperature of the desiccant as well as the dew point (ice point) or water concentration (partial pressure) specification. Indeed, the whole system may undergo periodic temperature transients that may compHcate the analysis. Eor example, in dual-pane windows the desiccant temperature is approximately the average of the indoor and outdoor temperatures after a night of cooling. However, after a day in the sun, the desiccant temperature becomes much warmer than the outdoor temperature. When the sun sets, the outdoor pane cools quickly while the desiccant is still quite warm. The appropriate desiccant for such an appHcation must have sufficient water capacity and produce satisfactory dew points at the highest temperatures experienced by the desiccant. [Pg.509]

Another aspect to consider in the design of closed-drying systems is the drydown time. The drydown time is the period requited for the system to dry down from its initial water concentration (or partial pressure) to a concentration that approaches equihbrium with the desiccant. During this time, the system is not fljlly protected from the negative effects of the moisture that the desiccant is designed to remove. In such a system, the instantaneous drying rate is proportional to the water content at any time (18). [Pg.509]

One final comment on this first paper is that I recommended the use of many tables and suggested that no one table was better than others. This is something that I no longer believe. According to a realistic interpretation, the periodic system is referring to some objective relationship among the elements that exists in nature and is not the result of mere human construction. I believe that it does therefore make perfect sense to be seeking an optimal periodic system in the sense of one that most closely reveals the precise periodic relationship between as many elements as possible.8... [Pg.3]

Closed-loop systems should lose very little water, perhaps only 5 to 10% of the system volume per year. In practice, however, losses often tend to be much higher than this, perhaps due to unforeseen maintenance work that necessitates a system to be partially drained. A typical loss is more likely to be 50% of the system volume per season. This obviously causes problems with regard to maintaining adequate chemical treatment reserves for effective deposit and corrosion control. In fact, often the first sign that a closed-loop system is losing water is when a periodic test is undertaken and the result indicates a reduced level or complete lack of treatment reserve. [Pg.659]

N, 0, F, P, S, and Cl the bond orbitals for normal valence compounds lead to about the same radii as tetrahedral orbitals, whereas in atoms below these in the periodic system normal valence bonds involve orbitals which approach p-orbitals rather closely, and so lead to weaker bonds, and to radii larger than the tetrahedral radii. This effect should be observed in Br, Se, and As, but not in Ge, and in I, Te, and Sb, but not Sn. For this reason we have added 0.03 A to the tetrahedral radii for As and Se and... [Pg.170]

The main quantity providing the dynamic longitudinal polarizability of closed-shell infinite periodic systems is the polarization propagator which at the RPA level takes the form [23-25] ... [Pg.100]

Continuous Stirred Tanks with Biomass Recycle. When the desired product is excreted, closing the system with respect to biomass offers a substantial reduction in the cost of nutrients. The idea is to force the cells into a sustained stationary or maintenance period where there is relatively little substrate used to grow biomass and where production of the desired product is maximized. One approach is to withhold some key nutrient so that cell growth is restricted, but to supply a carbon source and other components needed for the desired product. It is sometimes possible to maintain this state for weeks or months and to achieve high-volumetric productivities. There will be spontaneous cell loss (i.e., kd > 0), and true steady-state operation requires continuous purging and makeup. The purge can be achieved by incomplete separation and recycle... [Pg.457]

The most important metals for catalysis are those of Groups VIII and I-B of the periodic system. Three crystal structures are important, face-centered cubic (fee Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au), hexagonal close-packed (hep Co, Ru, Os) and body-centered cubic (bcc Fe) [9, 10]. Before discussing the surfaces that these lattices expose, we mention a few general properties. [Pg.293]

Similarity between quantum systems, such as atoms and molecules, plays a very important role throughout chemistry. Probably the best example is the ubiquitously known periodic system of the elements. In this system, elements are arranged both horizontally and vertically in such a way that in both directions, elements have a high similarity to their neighbors. Another closely related idea is that of transferability. In chemistry, one speaks of transferability of an entity when its properties remain similar between different situations. An example is the transferability of the properties of a functional group between one molecule and another. The main motto of using similarity in chemistry is the assumption that similar molecules have similar properties. [Pg.229]

Use closed-loop systems, which might be installed down-mine , or within settlement basins at a minewater treatment plant. Here the collector fluid circulates in a closed-loop and never comes into contact with the mine water. Likewise, mine water never enters the heat pump or heat exchanger elements. The problem is thus wholly averted, although there are limitations in capacity to closed-loop systems. For larger capacity operations, open systems will be preferred. Furthermore, the exterior of such closed-loop systems may become heavily fouled, necessitating periodic removal for cleaning. [Pg.507]

From the reaction-kinetic modeling point of view, the NSRC, sometimes called lean NOx trap (LNT) or NOx adsorber, is the most complex of the currently used automobile exhaust converters. A variety of different physical and chemical processes and the number of gas and surface components participating in typical periodic lean/rich operation form a large and closely linked system. [Pg.142]

The periodic system developed from Bohr s atomic theory is of the greatest importance in chemical science because it demonstrates that the properties of the elements depend on their positions in the system. It is immediately apparent that chemical valency depends on the number of loosely-bound electrons in the atom. Thus, the alkali metals have one such electron while the divalent alkaline-earth metals have two, etc. Valency is therefore closely connected with electronic structure and provides the foundation for the modern theory of the chemical bond, the basis of which is to be found in the coupling or transfer of the valency electrons. [Pg.11]

Atomic Number. The number of positive charges or the number of negative electrons around the nucleus was designated as the atomic number of the atom, These showed a close parallelism with the arrangement of atoms in the periodic system. Through the formulation of a number of rules based upon Bohr s picture of quantized orbits, the periodic system of tlie elements could be understood, Hydrogen was given one electron, and helium two, The two electrons in helinin constituted a closed shell which exhibited almost perfect spherical symmetry and chemical inactivity. [Pg.1209]

It is important not to leave the system empty of water for any long period, as rapid surface rusting will take place. As soon as the closed-loop system is declared free of contamination, sufficient corrosion inhibitor is added to provide long-term corrosion protection. The corrosion inhibitor is usually an anodic, passivating formulation, typically based on nitrite or tannin (and often in combination with phosphate, silicate, borate, or molybdate, etc.). Finally, after confirmation that the entire system is adequately treated (which usually requires the inhibited water in the system to be recirculated for a further 16 to 24 hours), the system is signed off and handed over. [Pg.335]

To find the condition for equilibrium, then, we must investigate the nature of the streamlines. For a periodic motion, a streamline will be closed, the system returning to its original state after a single period. This is a very special case, however most motions of many particles are not periodic and their streamlines never close. Rather, they wind around... [Pg.37]

At the end of the Periodic System there begins a new group of closely related elements, to which the transuranes also belong, by the completion of the 5f shell in this instance. [Pg.13]

Atomic Weight.—The chemical properties of caesium indicate its close relationship to the other alkali-metals. It is univalent, forming compounds of the type CsX, its atomic weight and hydrogen equivalent being the same. Its atomic weight is of the order Cs =133 a value conformed by the specific-heat method (Vol. I., p. 88) by the isomorphism of the caesium compounds with those of potassium, ammonium, and rubidium (Vol. I., p. 74) by the correspondence of the properties of the metal and its compounds with the periodic system by the formation of a univalent cation and by the depression of the freezing-point of bismuth chloride and mercuric chloride produced by caesium chloride. [Pg.201]

Here S E) is the classical action at the energy E, x = (q,p), X= (Q,P) represent the coordinates transverse to the trajectory on a PSS, M is the mapping matrix on the same PSS, I is a unit matrix, n is the dimensionality of the system, J is the 2(m — 1) by 2 n—l) unit matrix, s is a spectral parameter that will eventually be set to zero, T is the period of the periodic trajectory, Ai(x) is the Airy function, and the phase factor jj is a multiple of ti/4 determined by the focusing behavior of classical trajectories close to the jth periodic orbit. Note that on the closed periodic trajectory we have X = 0. In the semiclassical limit i.e., (H —> 0), these scar terms reduce to... [Pg.107]


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See also in sourсe #XX -- [ Pg.253 ]




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