Spheroidization mechanism

Cast irons are iron with high levels of carbon. Heat treatments and alloying element additions produce gray cast iron, malleable iron, ductile iron, spheroidal cast iron and other grades. The mechanical properties vary significantly. Nickel-containing cast irons have improved hardness and corrosion resistance. Copper or molybdenum additions improve strength. 

Note that the values of h depends upon the material and the mechanism of sintering. Also, these values depend upon r and x, the radii of the particles and the radius of joining. These equations apply only to spheroids and a shape factor must be considered as well. 

Because of this a study of mathematical properties of function U led to understanding geometrical and mechanical features of level surfaces. Also, with a help of potential it was proved that external surface of earth with an accuracy of flattening of the first order has to be spheroid. The next step in developing the theory of the... 

Droplet Formation in Water Atomization. In water atomization of melts, liquid metal stream may be shattered by impact of water droplets, rather than by shear mechanism. When water droplets at high velocities strike the liquid metal stream, some liquid metal fragments are knocked out by the exploding steam packets originated from the water droplets and subsequently contract into spheroidal droplets under the effect of surface tension if spheroidization time is less than solidification time. It is assumed that each water droplet may be able to knock out one or more metal droplet. However, the actual number of metal droplets produced by each water droplet may vary, depending on operation conditions, material properties, and atomizer designs. 

The mechanism of mass transfer to the external flow is essentially the same as for spheres in Chapter 5. Figure 6.8 shows numerically computed streamlines and concentration contours with Sc = 0.7 for axisymmetric flow past an oblate spheroid (E = 0.2) and a prolate spheroid (E = 5) at Re = 100. Local Sherwood numbers are shown for these conditions in Figs. 6.9 and 6.10. Figure 6.9 shows that the minimum transfer rate occurs aft of separation as for a sphere. Transfer rates are highest at the edge of the oblate ellipsoid and at the front stagnation point of the prolate ellipsoid. 

The key to the successful application of high performance, pourable nitrocellulose plastisols lies in a reasonably priced, high quality source of fine-particle, at least partially colloided, spheroidal nitrocellulose. Here we are speaking of particles much finer than the well-known ball powder, produced by the Olin Mathieson Chemical Co. for small arms for over 30 years (7). Actually, particles on the order of 5-50/x diameter appear to be required to assure a reasonable continuum of uniformly plasticized nitrocellulose binder in a propellant containing 45% or more of combined crystalline oxidizer and powdered metal fuel. Such a continuum of binder is necessary to assure acceptable mechanical properties and reproducible burning characteristics of the finished propellant. Preincorporation of a certain content of the water-insoluble solids within the nitrocellulose microspheres is an effective means of helping to assure this continuum of binder and alleviates the requirements for extremely small ball size. The use of a total of 45% or more of crystalline oxidizer and (generally) metal fuel is essential if the propellant is to be competitive with other modern propellants now in service. 

The conformational changes central to this mechanism are driven by the passage of protons through the F0 portion of ATP synthase. The streaming of protons through the F0 pore causes the cylinder of c subunits and the attached y subunit to rotate about the long axis of y, which is perpendicular to the plane of the membrane. The y subunit passes through the center of the a3/33 spheroid, which is held stationary relative to the membrane surface by the b2 and 8 subunits (Fig. 19-23f). With each rotation of 120°, y comes into contact with a different /3 subunit, and the contact forces that /3 subunit into the /3-empty conformation. 

Exotic atomic nuclei may be described as structures than do not occur in nature, but are produced in collisions. These nuclei have abundances of neurons and protons that are quite different from the natural nuclei. In 1949, M.G, Mayer (Argonne National Laboratory) and J.H.D. Jensen (University of Heidelberg) introduced a sphencal-shell model of die nucleus. The model, however, did not meet the requirements and restrains imposed by quantum mechanics and the Pauli exclusion principle, Hamilton (Vanderbilt University) and Maruhn (University of Frankfurt) reported on additional research of exotic atomic nuclei in a paper published in mid-1986 (see reference listedi. In addition to the aforementioned spherical model, there are several other fundamental shapes, including other geometric shapes with three mutually peipendicular axes—prolate spheroid (football shape), oblate spheroid (discus shape), and triaxial nucleus (all axes unequal). 

Although the dominant mixing mechanism of an immiscible liquid polymeric system appears to be stretching the dispersed phase into filament and then form droplets by filament breakup, individual small droplet may also break up at Ca 3> Ca. A detailed review of this mechanism is given by Janssen (34). The deformation of a spherical liquid droplet in a homogeneous flow held of another liquid was studied in the classic work of G. I. Taylor (35), who showed that for simple shear flow, a case in which interfacial tension dominates, the drop would deform into a spheroid with its major axis at an angle of 45° to the how, whereas for the viscosity-dominated case, it would deform into a spheroid with its major axis approaching the direction of how (36). Taylor expressed the deformation D as follows... 

Three main tendencies have been underlined in recent studies of structure and action mechanism ofbacterial photosynthetic reaction centers. The crystallographic structure of the reaction centers from Rps. viridis and Rb. spheroids was initially determined to be 2.8 and 3 A resolutions (Michel and Deisenhofer et al., 1985 Allen et al., 1986). Resolution and refinement of these structures have been subsequently extended to 2.2, 2.3 and 2.6 A. (Rees et al., 1989 Stowell et al., 1997, Fyfe and Johns, 2000 Rutherford and Faller, 2001). Investigations of the electronic structure of donor and acceptor centers in the ground and exited states by modern physical methods with a combination ofpico-and femtosecond kinetic techniques have become more precise and elaborate. Extensive experimental and theoretical investigations on the role of orbital overlap and protein dynamics in the processes of electron and proton transfer have been done. All the above-mentioned research directions are accompanied by extensive use of methods of sit-directed mutagenesis and substitution of native pigments for artificial compounds of different redox potential. 

The major mechanism of generation of both the natural and anthropogenic StA is a pyrolysis in the gas- or condensed-phase of the carbon-containing material. The microphysical characteristics of the resulting StA depend on the specific nature of the source so, for instance, the particles produced by oil combustion have a coral-like structure and an effective spherical shape the pyrolysis of coal gives particles in the form of spheres, with a great amount of smaller, randomly oriented spheroids inside them [11]. 

Bataille, B. Ligarski, K. Jacob, M. Thomas, C. Duru, C. Study of the Influence of Spheronization and Drying Conditions on the Physico-Mechanical Properties of Neutral Spheroids Containing Avicel pH 101 and Lactose. Drug Dev. Ind. Pharm. 1993, 19 (6), 653-671. 

In deep-sea sediments, opal-CT commonly occurs as platy, blade-shaped crystals that are often arranged in spheroidal rosettes a few /zm in diameter. These rosettes are known as lepispheres (Wise and Kelts, 1972). The nearly euhedral crystal habit of natural lepisphere crystals indicates that the opal-CT precipitated in situ as an authigenic mineral this conclusion is supported by results of experimental studies (Oehler, 1973) in which completely euhedral lepisphere crystals were synthesized from amorphous silica. Thus, it appears that the conversion of biogenic silica (opal-A) to opal-CT occiurs principally, if not exclusively, through a solution-reprecipitation mechanism. 

For the spheroids, we were able to obtain SERS signals of cyanide, even at concentrations of cyanide too low to show changes in the visible spectra [62]. Thus, it appears that cyanide can adsorb to the surface and yet not immediately react. This is consistent with a purported mechanism of cyanide reaction with gold, in which the adsorbed cyanide ions react to form a protective AuCN layer [62]. 

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