Collapsible mechanism

Fig. IV-18. (a) Electron micrograph of a collapsing film of 2-hydroxytetracosanoic acid. Scale bar 1. [From H. E. Ries, Jr., Nature, 281, 287 (1979).] (b) Possible collapse mechanism. [Reprinted with permission from H. E. Ries, Jr. and H. Swift, Langmuir, 3, 853 (1987) (Ref. 223). Copyright 1987, American Chemical Society.]...

For these sequences the value of Gj, is less than a certain small value g. For such sequences the folding occurs directly from the ensemble of unfolded states to the NBA. The free energy surface is dominated by the NBA (or a funnel) and the volume associated with NBA is very large. The partition factor <6 is near unify so that these sequences reach the native state by two-state kinetics. The amplitudes in (C2.5.7) are nearly zero. There are no intennediates in the pathways from the denatured state to the native state. Fast folders reach the native state by a nucleation-collapse mechanism which means that once a certain number of contacts (folding nuclei) are fonned then the native state is reached very rapidly [25, 26]. The time scale for reaching the native state for fast folders (which are nonnally associated with those sequences for which topological fmstration is minimal) is found to be... 

In blast analyses, the resistance is usually specified as a nonlinear function to simulate elastic, perfectly plastic behavior of the structure. The ultimate resistance, (R ) is reached upon formation of a collapse mechanism in the member. When the resistance is nonlinear, the dynamic equilibrium equation becomes ... 

The first step in developing a resistance function is to determine the plastic section capacities, such as plastic moment, Mp, as shown in Figure 7.1. The next step is to determine the sequence of plastic hinge formation and the corresponding load and deformation values. This is done by incrementally applying loads until a collapse mechanism is formed as illustrated in Figure 7.2 for a fixed end beam with a uniform load. 

Boundar y conditions need to be assessed based on the type of connections to be used for the member supports. The engineer must keep in mind that support details must provide sufficient strength, ductility and stability to enable the member to develop full collapse mechanism. Support capability to resist reaction forces for both the loading and rebound phases of the response must be considered when assessing boundary conditions. 

Ultimate Capacity - The load applied to a structural element as the final plastic hinge, or collapse mechanism, is formed. 

The collapse produced in both of these simulations arises from the intramolecular short-range attractive two-body interactions experienced by a polymer in a poor solvent. Another interesting type of collapse was recently proposed/45 then identified in a simulation on a diamond lattice/46 and subsequently verified by experiment with copolymers of acrylamide and V-isopropylacrylamide. 47 This collapse mechanism operates in grafted layers of chains when the short-range binary interactions are repulsive, but higher order interactions in W-clusters are attractive. The value of N is found experimentally to be three for copolymers of acrylamide and /V-isopropylacrylamide, 46 as was assumed in the simulation. 47 ... 

ET from a nucleophile to an alkyl halide followed by coupling of the radicals through a cage collapse mechanism has been proposed by Lund24, Bordwell25, Ashby26 and coworkers and by others27. 

The formation of 119 is due to the attack of phenyl radical at thep-position of the carban-ion. The 119 118 ratio (1.7 3.7) depends on the concentration of both reactants. Competition between S l and the cage collapse mechanism has been proposed for this system. 

High dispersive precipitated silica submitted to an increasing pressure in a mercury porosimeter shows successively a collapse mechanism of porous texture followed by a mechanism of mercury intrusion in the part of pore network which has resisted to the collapse. Such a behavior has been previously observed on low density xerogels and on some carbon black. Both mechanisms can be clearly distinguished by a sharp variation of slope of cumulative pore volume curve versus pressure. 

At TT > TTg the relaxation phenomena for insoluble monolayers are caused by the transformation of a homogeneous monolayer phase into a heterogeneous monolayer-collapse phase system. However, some differences exist between saturated-LMWE and unsaturated-LMWE monolayers (Eigure 14.6b). Relaxation phenomena in saturated-LMWE monolayer are controlled predominantly by the collapse mechanism because the surface pressure relaxes to TTg. Eor these systems the monolayer collapses by nucleation and growth of critical nuclei. Unsaturated-LMWE monolayers behave differently to saturated-LMWE monolayers. As the surface pressure relaxes from the collapse value, which is close to TTg, towards values lower than TTg at longer times, the collapse competes with a desorption mechanism (Patino and Nino, 1999). 

Small strains are typically confined to the linear response region, after which the region of plastic collapse takes over. At high strains, the material will typically experience a densification response in which the cell walls have been fully crushed and the bulk material properties begin to be exhibited. As one would expect, the greater the relative density, the smaller the role played by the collapse of the cell walls. At somewhere near 0.3 relative density, the cells are sufficiently apart that the collapse mechanisms are insignificant (illustrated in Figure 6.31). 

Ever since Wu s discovery of the coil-globule transition of single PNIPAAM chains near the LCST [63-66], the collapse mechanism including the formation of stable mesoglobules has been a topic of intense research [8, 48, 50, 67-73]. Despite these efforts, a molecular scale picture of what happens when thermore-sponsive polymers start to dehydrate at a certain temperature, subsequently... 

Lastly, we have determined that in addition to polymer structure, the addition order of materials, such as polymer, surfactant and salt, to a formulation affects the compositional range of coacervate formation and the coacervation mechanism. Depending on the flexibility of the polymer structure, the mechanisms of coacervation in the presence of added electrolyte can vary. Poly (4-vinyl pyridine)-LAS-NaCl systems show a polymer collapse mechanism with the formation of a super-salt when salt and polymer are pre-mbced. However, for the stiff cellulosic polymers, the pre-mixing of salt and polymer before surfactant addition enhances micelle-bridging without complete polymer collapse. Also, the addition... 

Fraldi, M. Guarracino, F. 2010. Analytical solutions for collapse mechanisms in tunnels with arbitrary cross sections. International Journal of Solids and Structures 47(2) 216-223. 

In Figure 8.8, the distribution section below 2 nm has been calculated from Nj adsorption and Brunauer s model, the section between 2 nm and 7.5 nm has been calculated from Nj adsorption and Broekhoff and de Boer s model, the section between 7.5 nm and 94 nm has been calculated from Hg porosimetry and Washburn s model and the section beyond 94 nm has been calculated from Hg porosimetry and Pirard s model. The size of 94 nm corresponds to the transition from the collapse mechanism in pores larger than 94 nm to the intrusion mechanism in pores smaller than 94 nm (P = 16 MPa). The total cumulative porous volume is obtained by summing up the cumulative volumes corresponding those successive ranges. 

A wide section of the guideline focuses on the brittle failure mechanisms. In particular, according to experiences gained from examining the performances of RC structures after seismic events, a wide section focuses on the most common brittle collapse mechanisms resulting from shear failure of partially confined beam-column joints (i.e. exterior or comer joints on the perimeter of the stmcture in some cases, where frames are only in one of the plan directions, they could be also interior). The typical joint failures observed in the L Aquila post earthquake are described and a local strengthening procedure by means of FRP, steel jacketing or CAM technique is discussed. 

Fredlund DG. 1995. The collapse mechanism of a soil subject to one-dimensional loading and wetting. E. Derbyshire et al (ed.), Genesis and Properties of Collapsible Soils. 486 173-206. 

Removal of all storey collapse mechanisms ( soft storey )... 

The brittle collapse mechanisms to be eliminated and the related types of application are as follows ... 

Provided that, in the absence of walls, the storey collapse mechanisms can be activated due to the formation of plastic hinges both at the top and at the bottom of the storey columns, the application should aim to enhance the tensile capacity in those areas with a view to limit the formation of the aforementioned hinges. In no case is the removal of the storey collapse mechanism allowed, with only the goal of increasing the magnitude of the displacements leading to its activation. 

Reveal Multiple Folding Nuclei for Nucleation-collapse Mechanism. 

As discussed earlier, the WSD methodology utilized the concept of FS to ensure the stability of foundations. Design must ensure that the calculated factors of safety against all potential failure or collapse mechanisms are equal to or greater than certain specified minimum value of the FS. Typical values of the FS used in the static design of spread footing foundations are presented in Table 8.1. 

Keywords Molecular dynamics Computer simulation Film balance Stober sihca Nanoparticles Collapse mechanism... 

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